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Sample records for assembled multilayer functionalized

  1. A multilayered supramolecular self-assembled structure from soybean oil by in situ polymerization and its applications.

    Science.gov (United States)

    Kavitha, Varadharajan; Gnanamani, Arumugam

    2013-05-01

    The present study emphasizes in situ transformation of soybean oil to self-assembled supramolecular multilayered biopolymer material. The said polymer material was characterized and the entrapment efficacy of both hydrophilic and hydrophobic moieties was studied. In brief, soybean oil at varying concentration was mixed with mineral medium and incubated under agitation (200 rpm) at 37 degrees C for 240 h. Physical observations were made till 240 h and the transformed biopolymer was separated and subjected to physical, chemical and functional characterization. The maximum size of the polymer material was measured as 2 cm in diameter and the cross sectional view displayed the multilayered onion rings like structures. SEM analysis illustrated the presence of multilayered honeycomb channeled structures. Thermal analysis demonstrated the thermal stability (200 degrees C) and high heat enthalpy (1999 J/g). Further, this multilayered assembly was able to entrap both hydrophilic and hydrophobic components simultaneously, suggesting the potential industrial application of this material.

  2. Multilayer Perceptrons to Approximate Quaternion Valued Functions.

    Science.gov (United States)

    Xibilia, M G.; Muscato, G; Fortuna, L; Arena, P

    1997-03-01

    In this paper a new type of multilayer feedforward neural network is introduced. Such a structure, called hypercomplex multilayer perceptron (HMLP), is developed in quaternion algebra and allows quaternionic input and output signals to be dealt with, requiring a lower number of neurons than the real MLP, thus providing a reduced computational complexity. The structure introduced represents a generalization of the multilayer perceptron in the complex space (CMLP) reported in the literature. The fundamental result reported in the paper is a new density theorem which makes HMLPs universal interpolators of quaternion valued continuous functions. Moreover the proof of the density theorem can be restricted in order to formulate a density theorem in the complex space. Due to the identity between the quaternion and the four-dimensional real space, such a structure is also useful to approximate multidimensional real valued functions with a lower number of real parameters, decreasing the probability of being trapped in local minima during the learning phase. A numerical example is also reported in order to show the efficiency of the proposed structure. Copyright 1997 Elsevier Science Ltd. All Rights Reserved.

  3. Nanoscale patterning of ionic self-assembled multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Tulpar, Aysen; Jang, C-H; Ducker, William A [Department of Chemistry, Virginia Tech, Blacksburg, VA 24061 (United States); Wang Zhiyong [Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, VA 24061 (United States); Jain, Vaibhav [Macromolecular Science and Engineering, Virginia Tech, Blacksburg, VA 24061 (United States); Heflin, James R [Department of Physics, Virginia Tech, Blacksburg, VA 24061 (United States)], E-mail: wducker@unimelb.edu.au

    2009-04-15

    Films that are nanostructured in all three dimensions can be fabricated by the templated growth of ionic self-assembled multilayers (ISAMs) on solids that have been patterned by nanografting. Nanografting was used to controllably pattern -COOH surface groups on a background of -OH groups. Atomic force microscopy (AFM) confirms that ISAM bilayers grow selectively on the -COOH groups and not on the surrounding -OH groups. The patterned area clearly shows an increase in height with an increase in the number of bilayers. As compared with other methods of nanofabrication, nanografting with ISAM deposition provides fast and precise control over the size of the pattern region, which remains stable even after repeated washing. This combination allows the fabricated template to be altered in situ without the need of any kind of mask, expensive probe, or post-lithography processing/cleaning methods. We have demonstrated line widths of 75 nm. Ultimately the line width is limited by the width of the AFM tip that causes desorption of the thiol, which is typically about 25 nm. Smaller line widths should be possible with the use of sharper AFM tips.

  4. Multilayer thin films: sequential assembly of nanocomposite materials

    National Research Council Canada - National Science Library

    Decher, Gero; Schlenoff, Joseph B

    2003-01-01

    ... polymeric or nanoparticulate building blocks, understanding the polymer physical chemistry of multilayers, or characterizing their optical, electrical or biological activities. The reasons for the intense interest in the field are also clearly evident: multilayers bridge the gap between monolayers and spun-on or dip-coated films, ...

  5. Multilayer Thin Films Sequential Assembly of Nanocomposite Materials

    CERN Document Server

    Decher, Gero

    2003-01-01

    Materials scientists are often faced with the problem of modifying surfaces of objects, yet keeping their shape and properties. This book provides a detailed survey on the new technology of adsorption from solution for the fabrication of molecularly ordered multicomposite films in order to replace and expand on the well known Langmuir-Blodgett technology and to open the field of molecular self-assembly to materials and biosciences. The book is aimed at scientists who want to integrate several different functional entities in a single device. To this audience it presents the technique of layer-

  6. Film bulk acoustic formaldehyde sensor with layer-by-layer assembled carbon nanotubes/polyethyleneimine multilayers

    Science.gov (United States)

    Wang, Wei; Chen, Da; Wang, Hongfei; Yu, Wenhua; Wu, Maozeng; Yang, Lei

    2018-02-01

    Trace formaldehyde vapor was detected by a micron-scale AlN film bulk acoustic resonator based on mass-sensitive mechanism. The layer-by-layer carbon nanotubes/polyethyleneimine multilayers were assembled on the resonator surface as the sensitive coating. An almost linear decrease of the resonant frequency was observed as a function of the number of nanotubes/polyethyleneimine periods. The multilayers showed a random and porous structure and thus provided a large specific surface area for gas adsorption and diffusion. At the same time, the amine groups in polyethyleneimine had an strong affinity to formaldehyde with excellent selectivity. When exposed to gaseous formaldehyde, the attachment of gas molecules induced a small decrease in the resonant frequency, which made the sensor easily detect formaldehyde at ppb levels with 1 min response time. A linear relationship was observed between the formaldehyde concentrations and the frequency downshift of the resonator. The layer number had an obvious influence on the absorption/desorption behavior of formaldehyde. The gas sensitivity of FBAR sensors was 1.29–1.90 kHz ppb‑1 with the limit of detection of 24–38 ppb.

  7. Silica nanoparticles for the layer-by-layer assembly of fully electro-active cytochrome c multilayers

    Directory of Open Access Journals (Sweden)

    Feifel Sven C

    2011-12-01

    influence of particle size are discussed. Conclusions This study demonstrates the ability to construct fully electro-active cyt c multilayer assemblies by using carboxy-modified silica nanoparticles. Thus it can be shown that functional, artificial systems can be build up following natural examples of protein arrangements. The absence of any conductive properties in the second building block clearly demonstrates that mechanisms for electron transfer through such protein multilayer assemblies is based on interprotein electron exchange, rather than on wiring of the protein to the electrode. The construction strategy of this multilayer system provides a new controllable route to immobilize proteins in multiple layers featuring direct electrochemistry without mediating shuttle molecules and controlling the electro-active amount by the number of deposition steps.

  8. Electrostatics and charge regulation in polyelectrolyte multilayered assembly.

    Science.gov (United States)

    Cherstvy, Andrey G

    2014-05-01

    We examine the implications of electrostatic interactions on formation of polyelectrolyte multilayers, in application to field-effect based biosensors for label-free detection of charged macromolecules. We present a quantitative model to describe the experimental potentiometric observations and discuss its possibilities and limitations for detection of polyelectrolyte adsorption. We examine the influence of the ionic strength and pH on the sensor response upon polyelectrolyte layer-by-layer formation. The magnitude of potential oscillations on the sensor-electrolyte interface predicted upon repetitive adsorption charge-alternating polymers agrees satisfactorily with experimental results. The model accounts for different screening by mobile ions in electrolyte and inside tightly interdigitated multilayered structure. In particular, we show that sensors' potential oscillations are larger and more persistent at lower salt conditions, while they decay faster with the number of layers at higher salt conditions, in agreement with experiments. The effects of polyelectrolyte layer thickness, substrate potential, and charge regulation on the sensor surface triggered by layer-by-layer deposition are also analyzed.

  9. Hyperbolic metamaterials beyond simple multilayers

    DEFF Research Database (Denmark)

    Zhukovsky, Sergei; Andryieuski, Andrei; Lavrinenko, Andrei

    2014-01-01

    Highly corrugated surfaces, nanoparticle assemblies, and super- structured multilayers offer superior functionality in controlling propagating volume plasmons with large wave vectors.......Highly corrugated surfaces, nanoparticle assemblies, and super- structured multilayers offer superior functionality in controlling propagating volume plasmons with large wave vectors....

  10. Single- and Multilayered Nanostructures via Laser-Induced Block Copolymer Self-Assembly

    Science.gov (United States)

    Majewski, Pawel; Yager, Kevin; Rahman, Atikur; Black, Charles

    We present a novel method of accelerated self-assembly of block copolymer thin films utilizing laser light, called Laser Zone Annealing (LZA). In our approach, steep temperature transients are induced in block copolymer films by rastering narrowly focused laser line over the light-absorbing substrate. Extremely steep temperature gradients accelerate the process of self-assembly by several orders-of-magnitude compared to conventional oven annealing, and, when coupled to photo-thermal shearing, lead to global alignment of block copolymer domains assessed by GISXAS diffraction studies and real-space SEM imaging. We demonstrate monolithic alignment of various block-copolymer thin films including PS-b-PMMA, PS-b-PEO, PS-b-P2VP, PS-b-PI and observe different responsiveness to the shearing rate depending on the characteristic relaxation timescale of the particular material. Subsequently, we use the aligned polymeric films as templates for synthesis of single- and multi-layered arrays of inorganic, metallic or semiconducting nanowires and nanomeshes and investigate their anisotropic electro-optical properties. Research carried out in part at the Center for Functional Nanomaterials, Brookhaven National Laboratory, which is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886.

  11. Multilayer Thin Films Sequential Assembly of Nanocomposite Materials

    CERN Document Server

    Decher, Gero

    2012-01-01

    This second, comprehensive edition of the pioneering book in this field has been completely revised and extended, now stretching to two volumes. The result is a comprehensive summary of layer-by-layer assembled, truly hybrid nanomaterials and thin films, covering organic, inorganic, colloidal, macromolecular and biological components, plus the assembly of nanoscale films derived from them on surfaces. Praise for the first edition: "... highly recommended to anyone interested in the field... and to scientists and researchers active in materials development..." –Polymer News With contri

  12. Layer-by-Layer Self-Assembled Graphene Multilayer Films via Covalent Bonds for Supercapacitor Electrodes

    Directory of Open Access Journals (Sweden)

    Xianbin Liu

    2015-05-01

    Full Text Available To maximize the utilization of its single-atom thin nature, a facile scheme to fabricate graphene multilayer films via a layer-by-layer self-assembled process was presented. The structure of multilayer films was constructed by covalently bonding graphene oxide (GO using p-phenylenediamine (PPD as a covalent cross-linking agent. The assembly process was confirmed to be repeatable and the structure was stable. With the π-π conjugated structure and a large number of spaces in the framework, the graphene multi‐ layer films exhibited excellent electrochemical perform‐ ance. The uniform ultrathin electrode exhibited a capacitance of 41.71 μF/cm2 at a discharge current of 0.1 μA/cm2, and displayed excellent stability of 88.9 % after 1000 charge-discharge cycles.

  13. Layer-by-Layer Self-Assembled Ferrite Multilayer Nanofilms for Microwave Absorption

    OpenAIRE

    Jiwoong Heo; Daheui Choi; Jinkee Hong

    2015-01-01

    We demonstrate a simple method for fabricating multilayer thin films containing ferrite (Co0.5Zn0.5Fe2O4) nanoparticles, using layer-by-layer (LbL) self-assembly. These films have microwave absorbing properties for possible radar absorbing and stealth applications. To demonstrate incorporation of inorganic ferrite nanoparticles into an electrostatic-interaction-based LbL self-assembly, we fabricated two types of films: (1) a blended three-component LbL film consisting of a sequential poly(acr...

  14. Fiber Optic pH Sensor with Self-Assembled Polymer Multilayer Nanocoatings

    OpenAIRE

    Hwa-Yaw Tam; Jacques Albert; Ming-Jie Yin; Li-Yang Shao

    2013-01-01

    A fiber-optic pH sensor based on a tilted fiber Bragg grating (TFBG) with electrostatic self-assembly multilayer sensing film is presented. The pH sensitive polymeric film, poly(diallyldimethylammonium chloride) (PDDA) and poly(acrylic acid) (PAA) was deposited on the circumference of the TFBG with the layer-by-layer (LbL) electrostatic self-assembly technique. The PDDA/PAA film exhibits a reduction in refractive index by swelling in different pH solutions. This effect results in wavelength s...

  15. Layer-by-layer assembled multilayers and polymeric nanoparticles for drug delivery in tissue engineering applications

    Science.gov (United States)

    Mehrotra, Sumit

    Tissues and organs in vivo are structured in three dimensional (3-D) ordered assemblies to maintain their metabolic functions. In the case of an injury, certain tissues lack the regenerative abilities without an external supportive environment. In order to regenerate the natural in vivo environment post-injury, there is a need to design three-dimensional (3-D) tissue engineered constructs of appropriate dimensions along with strategies that can deliver growth factors or drugs at a controlled rate from such constructs. This thesis focuses on the applications of hydrogen bonded (H-bonded) nanoscale layer-by-layer (LbL) assembled multilayers for time controlled drug delivery, fabrication of polymeric nanoparticles as drug delivery carriers, and engineering 3-D cellular constructs. Axonal regeneration in the central nervous system after spinal cord injury is often disorganized and random. To support linear axonal growth into spinal cord lesion sites, certain growth factors, such as brain-derived neurotrophic factor (BDNF), needs to be delivered at a controlled rate from an array of uniaxial channels patterned in a scaffold. In this study, we demonstrate for the first time that H-bonded LbL assembled degradable thin films prepared over agarose hydrogel, whereby the protein was loaded separately from the agarose fabrication, provided sustained release of protein under physiological conditions for more than four weeks. Further, patterned agarose scaffolds implanted at the site of a spinal cord injury forms a reactive cell layer of leptomeningeal fibroblasts in and around the scaffold. This limits the ability of axons to reinnervate the spinal cord. To address this challenge, we demonstrate the time controlled release of an anti-mitotic agent from agarose hydrdgel to control the growth of the reactive cell layer of fibroblasts. Challenges in tissue engineering can also be addressed using gene therapy approaches. Certain growth factors in the body are known to inhibit

  16. Polypeptide Multilayer Self-Assembly Studied by Ellipsometry

    Directory of Open Access Journals (Sweden)

    Marina Craig

    2014-01-01

    Full Text Available A polypeptide nanofilm made by layer-by-layer (LbL self-assembly was built on a surface that mimics nonwoven, a material commonly used in wound dressings. Poly-L-lysine (PLL and poly-L-glutamic acid (PLGA are the building blocks of the nanofilm, which is intended as an enzymatically degradable lid for release of bactericides to chronic wounds. Chronic wounds often carry infection originating from bacteria such as Staphylococcus aureus and a release system triggered by the degree of infection is of interest. The dry nanofilm was studied with ellipsometry. The thickness of the nanofilm was 60% less in its dry state than in its wet state. The measurements showed that a primer was not necessary to build a stable nanofilm, which is practically important in our case because a nondegradable primer is highly unwanted in a wound care dressing. Added V8 (glutamyl endopeptidase enzymes only showed adsorption on the nanofilm at room temperature, indicating that the PLL/PLGA “lid” may remain intact until the dressing has been filled with wound exudate at the elevated temperature typical of that of the wound.

  17. Polypeptide multilayer self-assembly studied by ellipsometry.

    Science.gov (United States)

    Craig, Marina; Holmberg, Krister; Le Ru, Eric; Etchegoin, Pablo

    2014-01-01

    A polypeptide nanofilm made by layer-by-layer (LbL) self-assembly was built on a surface that mimics nonwoven, a material commonly used in wound dressings. Poly-L-lysine (PLL) and poly-L-glutamic acid (PLGA) are the building blocks of the nanofilm, which is intended as an enzymatically degradable lid for release of bactericides to chronic wounds. Chronic wounds often carry infection originating from bacteria such as Staphylococcus aureus and a release system triggered by the degree of infection is of interest. The dry nanofilm was studied with ellipsometry. The thickness of the nanofilm was 60% less in its dry state than in its wet state. The measurements showed that a primer was not necessary to build a stable nanofilm, which is practically important in our case because a nondegradable primer is highly unwanted in a wound care dressing. Added V8 (glutamyl endopeptidase) enzymes only showed adsorption on the nanofilm at room temperature, indicating that the PLL/PLGA "lid" may remain intact until the dressing has been filled with wound exudate at the elevated temperature typical of that of the wound.

  18. Characterization of Self-Assembled Multilayers Made from Polycations Bearing Chromophore Residues.

    Science.gov (United States)

    Arys, X.; Jonas, A. M.; Legras, R.; Laschewsky, A.; Mayer, B.; Wischerhoff, E.

    1996-03-01

    The successive physisorption of polyelectrolytes bearing opposite charges has been extensively studied as a convenient way to obtain thin polymeric multilayered coatings on properly charged substrates footnote G. Decher et al., Biosensors & Bioelectronics 9, 677 (1994). We have controlled by X-ray reflectivity (XRR), ellipsometry and UV/VIS absorption studies the build-up of such multilayers made from polyvinylsulfate (PVS), and from polycations of the polyionene-type bearing azo-dye chromophores. A regular deposition is observed, with the internal structure of the layers being revealed by XRR. We then have combined features of this technique with ones of multilayer self-assembly and self-organization of amphiphiles, consisting in the cyclic physisorption of a polyionene bearing hydrophobic segments and reactive aniline residues, followed by a chemical activation (diazonium coupling) causing charge reversal at the interfaces. The multilayers build up regularly, with an average value of 12 Åper layer as determined by XRR. In this case, 2nd harmonic generation by the coatings was observed, suggesting a preferential orientation of the chromophores in the layers.

  19. Electrostatic self-assembly of multilayer copolymeric membranes on the surface of porous tantalum implants for sustained release of doxorubicin.

    Science.gov (United States)

    Guo, Xinming; Chen, Muwan; Feng, Wenzhou; Liang, Jiabi; Zhao, Huibin; Tian, Lin; Chao, Hui; Zou, Xuenong

    2011-01-01

    Many studies in recent years have focused on surface engineering of implant materials in order to improve their biocompatibility and other performance. Porous tantalum implants have increasingly been used in implant surgeries, due to their biocompatibility, physical stability, and good mechanical strength. In this study we functionalized the porous tantalum implant for sustained drug delivery capability via electrostatic self-assembly of polyelectrolytes of hyaluronic acid, methylated collagen, and terpolymer on the surface of a porous tantalum implant. The anticancer drug doxorubicin was encapsulated into the multilayer copolymer membranes on the porous tantalum implants. Results showed the sustained released of doxorubicin from the functionalized porous tantalum implants for up to 1 month. The drug release solutions in 1 month all had inhibitory effects on the proliferation of chondrosarcoma cell line SW1353. These results suggest that this functionalized implant could be used in reconstructive surgery for the treatment of bone tumor as a local, sustained drug delivery system.

  20. Supramolecular Assembly of Water-Soluble Poly(ferrocenylsilanes): Multilayer Structures on Flat Interfaces and Permeability of Microcapsules

    NARCIS (Netherlands)

    Ma, Y.; Dong, Wen-Fei; Kooij, Ernst S.; Hempenius, Mark A.; Mohwald, Helmuth; Vancso, Gyula J.

    2007-01-01

    We report on the layer-by-layer (LBL) supramolecular assembly of redox responsive, organometallic polyion films on planar and curved (spherical) substrates. Organometallic poly(ferrocenylsilane) (PFS) polyanions and polycations were first used to assemble multilayers on planar quartz, silicon and

  1. Protein adsorption and biomimetic mineralization behaviors of PLL-DNA multilayered films assembled onto titanium

    Energy Technology Data Exchange (ETDEWEB)

    Gao Wenli [Key Laboratory of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China); Feng Bo, E-mail: fengbo@swjtu.edu.cn [Key Laboratory of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China); Ni Yuxiang [Key Laboratory of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China); Yang Yongli [College of Material Science and Engineering, Sichuan University, Chengdu 610054 (China); Lu Xiong; Weng Jie [Key Laboratory of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China)

    2010-11-01

    Titanium and its alloys are frequently used as surgical implants in load bearing situations, such as hip prostheses and dental implants, owing to their biocompatibility, mechanical and physical properties. In this paper, a layer-by-layer (LBL) self-assembly technique, based on the polyelectrolyte-mediated electrostatic adsorption of poly-L-lysine (PLL) and DNA, was used to the formation of multilayer on titanium surfaces. Then bovine serum albumin (BSA) adsorption and biomimetic mineralization of modified surfaces were studied. The chemical composition and wettability of assembled substrates were investigated by X-ray photoelectron spectroscopy (XPS), fluorescence microscopy and water contact angle measurement, respectively. The XPS analysis indicated that the layers were assembled successfully through electrostatic attractions. The measurement with ultraviolet (UV) spectrophotometer revealed that the LBL films enhanced ability of BSA adsorption onto titanium. The adsorption quantity of BSA on the surface terminated with PLL was higher than that of the surface terminated with DNA, and the samples of TiOH/P/D/P absorbed BSA most. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) showed that samples of assembled PLL or/and DNA had better bioactivity in inducing HA formation. Thus the assembling of PLL and DNA onto the surface of titanium in turn via a layer-by-layer self-assembly technology can improve the bioactivity of titanium.

  2. Self-assembled multilayer films based on a Keggin-type polyoxometalate and polyaniline.

    Science.gov (United States)

    Wang, Yonghui; Guo, Caixin; Chen, Yanwei; Hu, Changwen; Yu, Wenhua

    2003-08-01

    Multilayer ultrathin films were fabricated from partially doped polyaniline (PAN) and a Keggin-type polyoxometalate [alpha-SiW(12)O(40)](4-) (alpha-SiW(12)) in aqueous solution via the layer-by-layer self-assembly technique and characterized by UV-vis, FTIR, and X-ray photoelectron spectra (XPS), ellipsometry, scanning electron microscopy (SEM), and atomic force microscopy (AFM). UV-vis spectroscopy shows that the absorbance values at characteristic wavelengths of the multilayer films increase almost linearly with the number of PAN/alpha-SiW(12) bilayers, suggesting that the deposition process is regular and highly reproducible from layer to layer. FTIR and XPS spectra confirm the incorporation of alpha-SiW(12) and PAN into the films. Ellipsometric measurements show that the PAN/alpha-SiW(12) bilayer thickness increases with the increasing PAN solution concentration. SEM and AFM images indicate that the film surface is relatively uniform and smooth. In addition, the electrical conductivities of the multilayer films doped with hydrochloric acid were also measured.

  3. One-step synthesis and stabilization of gold nanoparticles and multilayer film assembly

    Science.gov (United States)

    Bao, Ya-Yan; Bi, Li-Hua; Wu, Li-Xin

    2011-03-01

    Au nanoparticles (NPs) were synthesized in the one-pot procedure in water at room temperature with the wheel-shaped V V-V IV mixed-valence tungstovanadate [P 8W 48O 184{V 4VV 2IVO 12(H 2O) 2} 2] 32- (V12) acting as both reducing and stabilizing agents. The V12 stabilized Au NPs (Au@V12 NPs) were characterized by SEM, TEM, DLS, UV-vis spectroscopy, XPS, and XRD analyses and the negatively charged surface of the Au@V12 NPs was proved by the zeta potential analysis. Based on the layer-by-layer assembly (LbL), the Au@V12 NPs-containing multilayer films have been fabricated on ITO-coated glass slide and quartz substrates with poly(ethyleneimine) (PEI). The regular growth of the multilayer films was monitored by UV-vis spectroscopy and cyclic voltammetry, the composition was characterized by XPS. The Au@V12 NPs based composite films showed electrocatalytic activities towards the reduction of dioxygen and the oxidation of methanol. This approach is expected to open the way towards procedures aimed at the one-step fabrication of Au NPs and polyoxometalates (POMs) into the multilayer films.

  4. Approximate Green's function methods for HZE transport in multilayered materials

    Science.gov (United States)

    Wilson, John W.; Badavi, Francis F.; Shinn, Judy L.; Costen, Robert C.

    1993-01-01

    A nonperturbative analytic solution of the high charge and energy (HZE) Green's function is used to implement a computer code for laboratory ion beam transport in multilayered materials. The code is established to operate on the Langley nuclear fragmentation model used in engineering applications. Computational procedures are established to generate linear energy transfer (LET) distributions for a specified ion beam and target for comparison with experimental measurements. The code was found to be highly efficient and compared well with the perturbation approximation.

  5. Fiber Optic pH Sensor with Self-Assembled Polymer Multilayer Nanocoatings

    Directory of Open Access Journals (Sweden)

    Hwa-Yaw Tam

    2013-01-01

    Full Text Available A fiber-optic pH sensor based on a tilted fiber Bragg grating (TFBG with electrostatic self-assembly multilayer sensing film is presented. The pH sensitive polymeric film, poly(diallyldimethylammonium chloride (PDDA and poly(acrylic acid (PAA was deposited on the circumference of the TFBG with the layer-by-layer (LbL electrostatic self-assembly technique. The PDDA/PAA film exhibits a reduction in refractive index by swelling in different pH solutions. This effect results in wavelength shifts and transmission changes in the spectrum of the TFBG. The peak amplitude of the dominant spectral fringes over a certain window of the transmission spectrum, obtained by FFT analysis, has a near-linear pH sensitivity of 117 arbitrary unit (a.u./pH unit and an accuracy of ±1 a.u. (in the range of pH 4.66 to pH 6.02. The thickness and surface morphology of the sensing multilayer film were characterized to investigate their effects on the sensor’s performance. The dynamic response of the sensor also has been studied (10 s rise time and 18 s fall time for a sensor with six bilayers of PDDA/PAA.

  6. Carbon and nitrogen co-doping self-assembled MoS2 multilayer films

    Science.gov (United States)

    Zhang, Xiaoqin; Xu, Jiao; Chai, Liqiang; He, Tengfei; Yu, Fucheng; Wang, Peng

    2017-06-01

    Mo-S-C-N composite films were prepared using reactive magnetron sputtering of graphite and MoS2 targets in argon and nitrogen atmospheres. The effects of carbon/nitrogen co-doping and carbon concentration on the composition, microstructure, mechanical and tribological properties of deposited films have been investigated by various characterization techniques. The results show that the deposited films comprise MoS2 nanocrystalline and amorphous carbon, and the incorporating nitrogen forms Mo-N and C-N chemical bonds. Increasing carbon concentration leads to the increase of sp2 carbon fraction in the films. Furthermore, the high-resolution transmission electron microscopy reveals that a self-assembled multilayer structure with periodicity in the nanometer scale is formed in the Mo-S-C-N film. Benefiting from the composite and self-assembled multilayer structures, the hardness of Mo-S-C-N film deposited at optimized parameter reaches up to 9.76 GPa, and corresponding friction experiment indicates that this composite films display low friction coefficient and high wear resistance both in vacuum and ambient air conditions.

  7. Layer-by-Layer Self-Assembled Ferrite Multilayer Nanofilms for Microwave Absorption

    Directory of Open Access Journals (Sweden)

    Jiwoong Heo

    2015-01-01

    Full Text Available We demonstrate a simple method for fabricating multilayer thin films containing ferrite (Co0.5Zn0.5Fe2O4 nanoparticles, using layer-by-layer (LbL self-assembly. These films have microwave absorbing properties for possible radar absorbing and stealth applications. To demonstrate incorporation of inorganic ferrite nanoparticles into an electrostatic-interaction-based LbL self-assembly, we fabricated two types of films: (1 a blended three-component LbL film consisting of a sequential poly(acrylic acid/oleic acid-ferrite blend layer and a poly(allylamine hydrochloride layer and (2 a tetralayer LbL film consisting of sequential poly(diallyldimethylammonium chloride, poly(sodium-4-sulfonate, bPEI-ferrite, and poly(sodium-4-sulfonate layers. We compared surface morphologies, thicknesses, and packing density of the two types of ferrite multilayer film. Ferrite nanoparticles (Co0.5Zn0.5Fe2O4 were prepared via a coprecipitation method from an aqueous precursor solution. The structure and composition of the ferrite nanoparticles were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, transmission electron microscopy, and scanning electron microscopy. X-ray diffraction patterns of ferrite nanoparticles indicated a cubic spinel structure, and energy dispersive X-ray spectroscopy revealed their composition. Thickness growth and surface morphology were measured using a profilometer, atomic force microscope, and scanning electron microscope.

  8. Fiber optic pH sensor with self-assembled polymer multilayer nanocoatings.

    Science.gov (United States)

    Shao, Li-Yang; Yin, Ming-Jie; Tam, Hwa-Yaw; Albert, Jacques

    2013-01-24

    A fiber-optic pH sensor based on a tilted fiber Bragg grating (TFBG) with electrostatic self-assembly multilayer sensing film is presented. The pH sensitive polymeric film, poly(diallyldimethylammonium chloride) (PDDA) and poly(acrylic acid) (PAA) was deposited on the circumference of the TFBG with the layer-by-layer (LbL) electrostatic self-assembly technique. The PDDA/PAA film exhibits a reduction in refractive index by swelling in different pH solutions. This effect results in wavelength shifts and transmission changes in the spectrum of the TFBG. The peak amplitude of the dominant spectral fringes over a certain window of the transmission spectrum, obtained by FFT analysis, has a near-linear pH sensitivity of 117 arbitrary unit (a.u.)/pH unit and an accuracy of ±1 a.u. (in the range of pH 4.66 to pH 6.02). The thickness and surface morphology of the sensing multilayer film were characterized to investigate their effects on the sensor's performance. The dynamic response of the sensor also has been studied (10 s rise time and 18 s fall time for a sensor with six bilayers of PDDA/PAA).

  9. A functional protein retention and release multilayer with high stability

    Science.gov (United States)

    Nie, Kun; An, Qi; Zhang, Yihe

    2016-04-01

    Effective and robust interfacial protein retention lies at the heart of the fabrication of protein-based functional interfaces, which is potentially applicable in catalysis, medical therapy, antifouling, and smart devices, but remains challenging due to the sensitive nature of proteins. This study reports a general protein retention strategy to spatial-temporally confine various types of proteins at interfacial regions. The proteins were preserved in mesoporous silica nanoparticles embedded in covalently woven multilayers. It is worth noting that the protein retention strategy effectively preserves the catalytic capabilities of the proteins, and the multilayer structure is robust enough to withstand the bubbling catalytic reactions and could be repeatedly used due to conservation of proteins. The spatiotemporal retention of proteins could be adjusted by varying the number of capping layers. Furthermore, we demonstrate that the protein-loaded interfacial layers could not only be used to construct catalytic-active interfaces, but also be integrated as the power-generating unit to propel a macroscopic floating device.Effective and robust interfacial protein retention lies at the heart of the fabrication of protein-based functional interfaces, which is potentially applicable in catalysis, medical therapy, antifouling, and smart devices, but remains challenging due to the sensitive nature of proteins. This study reports a general protein retention strategy to spatial-temporally confine various types of proteins at interfacial regions. The proteins were preserved in mesoporous silica nanoparticles embedded in covalently woven multilayers. It is worth noting that the protein retention strategy effectively preserves the catalytic capabilities of the proteins, and the multilayer structure is robust enough to withstand the bubbling catalytic reactions and could be repeatedly used due to conservation of proteins. The spatiotemporal retention of proteins could be adjusted by

  10. Layer-by-layer self-assembly of minocycline-loaded chitosan/alginate multilayer on titanium substrates to inhibit biofilm formation.

    Science.gov (United States)

    Lv, Hongbin; Chen, Zhen; Yang, Xiaoping; Cen, Lian; Zhang, Xu; Gao, Ping

    2014-11-01

    Bacteria adhesion and subsequent biofilm formation are primary causes of implant associated infection. The biofilm makes the bacteria highly resistant to the host defense and antimicrobial treatment. Antibacterial coatings on the surface of titanium implant can prevent biofilm formation effectively, but it is still a challenge to accomplish relatively long lasting antibacterial effects before wound healing or formation of biological seal. The purpose of our work was to construct antibacterial multilayer coatings loaded with minocycline on surface of Ti substrates using chitosan and alginate based on layer-by-layer (LbL) self-assembly technique. In this study, the surfaces of Ti substrates were first hydroxylated and then treated with 3-aminopropyltriethoxysilane (ATPES) to obtain amino-functionalized Ti substrates. Next, the precursor layer of chitosan was covalently conjugated to amino-functionalized Ti substrates. The following alternately coating alginate loaded with minocycline and chitosan onto the precursor layer of chitosan was carried out via LbL self-assembly technique to construct the multilayer coatings on Ti substrates. The multilayer coatings loaded more minocycline and improved sustainability of minocycline release to kill planktonic and adherent bacteria. Moreover, surface charge and hydrophilicity of the coatings and antibacterial ability of chitosan itself also played roles in the antibacterial performance, which can keep the antibacterial ability of the multilayer coatings after minocycline release ceases. In conclusion, LbL self-assembly method provides a promising strategy to fabricate long-term antibacterial surfaces, which is especially effective in preventing implant associated infections in the early stage. Loading minocycline on the surface of implants based on LbL self-assembly strategy can endow implants with sustained antibacterial property. This can inhabit the immediate colonization of bacteria onto the surface of implants in the

  11. Multiparametric characterisation of metal-chalcogen atomic multilayer assembly by potentiodynamic electrochemical impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ragoisha, G.A. [Physico-Chemical Research Institute, Belarusian State University, Minsk 220050 (Belarus)], E-mail: ragoishag@bsu.by; Bondarenko, A.S. [Physico-Chemical Research Institute, Belarusian State University, Minsk 220050 (Belarus); Faculty of Science and Technology, University of Twente, P.O. Box 217, 7500 AE, Enschede (Netherlands); Osipovich, N.P. [Physico-Chemical Research Institute, Belarusian State University, Minsk 220050 (Belarus); Rabchynski, S.M.; Streltsov, E.A. [Chemistry Department, Belarusian State University, Minsk 220050 (Belarus)

    2008-04-20

    An approach to multiparametric characterisation of variable electroactive interfaces based on potentiodynamic electrochemical impedance spectroscopy (PDEIS) [G.A. Ragoisha, A.S. Bondarenko, Electrochim. Acta 50 (2005) 1553] has been extended to atomic multilayer assembly monitoring. The multilayers were formed by successive underpotential deposition of Te, Se and Pb or Cu adlayers on Au, and also by cadmium adlayer deposition on tellurium underlayer supported by gold. These multilayers were characterised in potentiodynamic mode by dependences of ac equivalent circuit parameters on electrode potential. The dependences disclose variations of interfacial double electric layer, charge transfer and diffusion. The dependencies of the characteristic parameters of the Au/Te{sub ad}/Se{sub ad}/Pb{sub ad} composite three-layer have been found to be significantly different from the corresponding dependences of Au/Te{sub ad}/Pb{sub ad} and Au/Se{sub ad}/Pb{sub ad} bilayers, while Au/Te{sub ad}/Se{sub ad}/Cu{sub ad} has shown much similarity with Au/Se{sub ad}/Cu{sub ad} in Faradaic part of ac response. Upd of Pb, Cu and Cd on the chalcogen adlayers has shown irreversibility with especially strong potential shift of adlayer oxidation potential in the case of lead deposition on bi-chalcogen Au/Te{sub ad}/Se{sub ad} underlayer. Unlike Pb adlayer, which is formed locally on top of tellurium-selenium bilayer and could be fully dissolved in the anodic scan in the potential range of stability of the chalcogen composite underlayer, copper penetrated into the Au/Te{sub ad}/Se{sub ad} bilayer and dissolved incompletely at Cu adlayer oxidation potential. The self-descriptiveness of potential dependences of circuit parameters suggests PDEIS to be a handy tool for layer-by-layer deposition monitoring in electrochemical nanotechnologies.

  12. Dyadic Green's functions for multi-layer SAW substrates.

    Science.gov (United States)

    Smith, P M

    2001-01-01

    Recent formulations of the dyadic (or generalized) Green's function describe the relationship between sources (both mechanical stresses and electrical charge) and waves (both mechanical displacements and acoustic potential) on the surface of a substrate. The 16 elements of the function intrinsically describe all propagation modes, whether Rayleigh or leaky, and are therefore, extremely useful in the design of surface acoustic wave devices. In addition to requiring little computational effort, the dyadic Green's function provides much more information than the traditional effective permittivity function. In this paper, we extend the calculation of the dyadic Green's function to multi-layer substrates. We show that its computation involves a simple cascaded matrix multiplication. The resulting function fully contains the substrate characteristics and, once obtained, can be used to describe the surface behavior with no further regard to the substrate's composition.

  13. Crystalline mono- and multilayer self-assemblies of oligothiophenes at the air-water interface

    DEFF Research Database (Denmark)

    Isz, S.; Weissbuch, I.; Kjær, K.

    1997-01-01

    The formation of Langmuir monolayers at the air-water interface has long been believed to be limited to amphiphilic molecules containing a hydrophobic chain and a hydrophilic headgroup. Here we report the formation of crystalline mono- and multilayer self-assemblies of oligothiophenes, a class...... of aromatic nonamphiphilic molecules, self-aggregated at the air-water interface. As model systems we have examined the deposition of quaterthiophene (S-4), quinquethiophene (S-5). and sexithiophene (S-6) from chloroform solutions on the water surface. The structures of the films were determined by surface...... pressure-area isotherms, by scanning force microscopy (SFM) after transfer of the films onto atomically smooth mica, by cryo-transmission electron microscopy (Cryo-TEM) on vitreous ice, and by grazing incidence synchrotron X-ray diffraction (GID) directly on the water surface. S-4 forms two polymorphic...

  14. Multi-layer canard cycles and translated power functions

    OpenAIRE

    Dumortier, Freddy; Roussarie, Robert

    2008-01-01

    The paper deals with two-dimensional slow-fast systems and more specifically with multi-layer canard cycles. These are canard cycles passing through n layers of fast orbits, with n >= 2. The canard cycles are subject to n generic breaking mechanisms and we study the limit cycles that can be perturbed from the generic canard cycles of codimension n. We prove that this study can be reduced to the investigation of the fixed points of iterated translated power functions. (c) 2007 El...

  15. Self-assembled iron oxide nanoparticle multilayer: x-ray and polarized neutron reflectivity.

    Science.gov (United States)

    Mishra, D; Benitez, M J; Petracic, O; Badini Confalonieri, G A; Szary, P; Brüssing, F; Theis-Bröhl, K; Devishvili, A; Vorobiev, A; Konovalov, O; Paulus, M; Sternemann, C; Toperverg, B P; Zabel, H

    2012-02-10

    We have investigated the structure and magnetism of self-assembled, 20 nm diameter iron oxide nanoparticles covered by an oleic acid shell for scrutinizing their structural and magnetic correlations. The nanoparticles were spin-coated on an Si substrate as a single monolayer and as a stack of 5 ML forming a multilayer. X-ray scattering (reflectivity and grazing incidence small-angle scattering) confirms high in-plane hexagonal correlation and a good layering property of the nanoparticles. Using polarized neutron reflectivity we have also determined the long range magnetic correlations parallel and perpendicular to the layers in addition to the structural ones. In a field of 5 kOe we determine a magnetization value of about 80% of the saturation value. At remanence the global magnetization is close to zero. However, polarized neutron reflectivity reveals the existence of regions in which magnetic moments of nanoparticles are well aligned, while losing order over longer distances. These findings confirm that in the nanoparticle assembly the magnetic dipole-dipole interaction is rather strong, dominating the collective magnetic properties at room temperature.

  16. Layer-by-layer self-assembly of multilayer films based on humic acid

    Energy Technology Data Exchange (ETDEWEB)

    Xu Zhengxia; Hu Chenyang; Guoxin Hu, E-mail: hugx@sjtu.edu.c

    2011-04-29

    Multilayer films consisting of negatively charged humic acid and positively charged polyelectrolyte have been fabricated on various substrates using the layer-by-layer self-assembly technique. The thickness (linearly increasing with the square root of NaCl concentration) and refractive index of the films determined by ellipsometry can be regulated by ionic strength through adjusting the coiling of the polyelectrolyte chains for assembly. The cone-shaped features on surface obtained by atomic force microscope are derived from the negatively charged colloidal humic acid binding with polyelectrolyte cation. The smooth features are corresponding to the dissociated humic acid with carboxylate ion (-COO{sup -}) electrostatically attracted on polyelectrolyte cation. These results are verified by Fourier transform infrared spectra. The linear dependence of the peak current on the square root of the scan rate revealed by the cyclic voltammetry indicates that the redox process at the electrode surface is diffusion-limited and the charge transport does not involve the film itself.

  17. Linear and Star Poly(ionic liquid) Assemblies: Surface Monolayers and Multilayers.

    Science.gov (United States)

    Erwin, Andrew J; Xu, Weinan; He, Hongkun; Matyjaszewski, Krzysztof; Tsukruk, Vladimir V

    2017-04-04

    The surface morphology and organization of poly(ionic liquid)s (PILs), poly[1-(4-vinylbenzyl)-3-butylimidazolium bis(trifluoromethylsulfonyl)imide] are explored in conjunction with their molecular architecture, adsorption conditions, and postassembly treatments. The formation of stable PIL Langmuir and Langmuir-Blodgett (LB) monolayers at the air-water and air-solid interfaces is demonstrated. The hydrophobic bis(trifluoromethylsulfonyl)imide (Tf2N-) is shown to be a critical agent governing the assembly morphology, as observed in the reversible condensation of LB monolayers into dense nanodroplets. The PIL is then incorporated as an unconventional polyelectrolyte component in the layer-by-layer (LbL) films of hydrophobic character. We demonstrate that the interplay of capillary forces, macromolecular mobility, and structural relaxation of the polymer chains influence the dewetting mechanisms in the PIL multilayers, thereby enabling access to a diverse set of highly textured, porous, and interconnected network morphologies for PIL LbL films that would otherwise be absent in conventional LbL films. Their compartmentalized internal structure is relevant to molecular separation membranes, ultrathin hydrophobic coatings, targeted cargo delivery, and highly conductive films.

  18. Properties of Self-Assembled Hybrid Organic Molecule/Quantum Dot Multilayered Structures

    NARCIS (Netherlands)

    Cohen, E.; Gruber, M.; Romero, E.; Yochelis, S.; van Grondelle, R.; Paltiel, Y.

    2014-01-01

    Hybrid nanostructures are attractive for future use in a variety of electronic components. Self-assembled hybrid organic/nanocrystals can couple quantum properties to semiconductor working devices and modify their functionality. For example, light absorption in some core quantum dot (QD)-based

  19. Unconventional layer-by-layer assembly of graphene multilayer films for enzyme-based glucose and maltose biosensing.

    Science.gov (United States)

    Zeng, Guanghong; Xing, Yibo; Gao, Jian; Wang, Zhiqiang; Zhang, Xi

    2010-09-21

    We have developed an unconventional method for the layer-by-layer (LbL) assembly of graphene multilayer films. Unconventional LbL assembly was achieved by the following two-step process. Graphene sheets were modified by pyrene-grafted poly(acrylic acid) (PAA) in aqueous solution, and then the modified graphene sheets were used for layer-by-layer alternating deposition with poly(ethyleneimine) (PEI). The graphene-multilayer-film-modified electrode shows enhanced electron transfer for the redox reactions of Fe(CN)(6)(3-) and excellent electrocatalytic activity of H(2)O(2). On the basis of this property, a bienzyme biosensing system for the detection of maltose was fabricated by successive LbL assembly of graphene, glucose oxidase (GOx), and glucoamylase (GA). LbL assembly of graphene combines the excellent electrochemical properties of graphene and the versatility of LbL assembly, showing great promise in highly efficient sensors and advanced biosensing systems.

  20. Supramolecular self-assembly of graphene oxide and metal nanoparticles into stacked multilayers by means of a multitasking protein ring.

    Science.gov (United States)

    Ardini, Matteo; Golia, Giordana; Passaretti, Paolo; Cimini, Annamaria; Pitari, Giuseppina; Giansanti, Francesco; Di Leandro, Luana; Ottaviano, Luca; Perrozzi, Francesco; Santucci, Sandro; Morandi, Vittorio; Ortolani, Luca; Christian, Meganne; Treossi, Emanuele; Palermo, Vincenzo; Angelucci, Francesco; Ippoliti, Rodolfo

    2016-03-28

    Graphene oxide (GO) is rapidly emerging worldwide as a breakthrough precursor material for next-generation devices. However, this requires the transition of its two-dimensional layered structure into more accessible three-dimensional (3D) arrays. Peroxiredoxins (Prx) are a family of multitasking redox enzymes, self-assembling into ring-like architectures. Taking advantage of both their symmetric structure and function, 3D reduced GO-based composites are hereby built up. Results reveal that the "double-faced" Prx rings can adhere flat on single GO layers and partially reduce them by their sulfur-containing amino acids, driving their stacking into 3D multi-layer reduced GO-Prx composites. This process occurs in aqueous solution at a very low GO concentration, i.e. 0.2 mg ml(-1). Further, protein engineering allows the Prx ring to be enriched with metal binding sites inside its lumen. This feature is exploited to both capture presynthesized gold nanoparticles and grow in situ palladium nanoparticles paving the way to straightforward and "green" routes to 3D reduced GO-metal composite materials.

  1. Transition mode long period grating biosensor with functional multilayer coatings.

    Science.gov (United States)

    Pilla, Pierluigi; Malachovská, Viera; Borriello, Anna; Buosciolo, Antonietta; Giordano, Michele; Ambrosio, Luigi; Cutolo, Antonello; Cusano, Andrea

    2011-01-17

    We report our latest research results concerning the development of a platform for label-free biosensing based on overlayered Long Period Gratings (LPGs) working in transition mode. The main novelty of this work lies in a multilayer design that allows to decouple the problem of an efficient surface functionalization from that of the tuning in transition region of the cladding modes. An innovative solvent/nonsolvent strategy for the dip-coating technique was developed in order to deposit on the LPG multiple layers of transparent polymers. In particular, a primary coating of atactic polystyrene was used as high refractive index layer to tune the working point of the device in the so-called transition region. In this way, state-of-the-art-competitive sensitivity to surrounding medium refractive index changes was achieved. An extremely thin secondary functional layer of poly(methyl methacrylate-co-methacrylic acid) was deposited onto the primary coating by means of an original identification of selective solvents. This approach allowed to obtain desired functional groups (carboxyls) on the surface of the device for a stable covalent attachment of bioreceptors and minimal perturbation of the optical design. Standard 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide / N-hydrosuccinimide (EDC / NHS) coupling chemistry was used to link streptavidin on the surface of the coated LPG. Highly sensitive real-time monitoring of multiple affinity assays between streptavidin and biotinylated bovine serum albumin was performed by following the shift of the LPGs attenuation bands.

  2. Layer-by-layer assembled multilayer of graphene/Prussian blue toward simultaneous electrochemical and SPR detection of H2O2

    DEFF Research Database (Denmark)

    Mao, Yan; Bao, Yu; Wang, Wei

    2011-01-01

    A new type of chemically converted graphene sheets, cationic polyelectrolyte-functionalized ionic liquid decorated graphene sheets (PFIL–GS) composite, was synthesized and characterized by Ultraviolet–visible (UV–vis) absorption, Fourier transform infrared, and Raman spectroscopy. It was found...... that the presence of PFIL enabled the formation of a very stable aqueous dispersion due to the electrostatic repulsion between PFIL modified graphene sheets. With respect to the excellent dispersibility of this material, we have fabricated a novel PFIL–GS/Prussian blue (PB) nanocomposite multilayer film via classic...... layer-by-layer (LBL) assembly. The assembly process was confirmed by UV–vis spectroscopy and surface plasmon resonance (SPR) spectroscopy, which showed linear responses to the numbers of the deposited PFIL–GS/PB bilayers. Moreover, the as-prepared composite films were used to detect hydrogen peroxide (H...

  3. Anticoagulant surface modification of titanium via layer-by-layer assembly of collagen and sulfated chitosan multilayers.

    Science.gov (United States)

    Li, Quan-Li; Huang, Nan; Chen, Jialong; Wan, Guojiang; Zhao, Ansa; Chen, Junying; Wang, Jin; Yang, Ping; Leng, Yongxiang

    2009-06-01

    Extracellular matrix (ECM)-like biomimetic surface modification of cardiovascular implants is a promising method for improving hemocompatibility. In the present work, collagen (Col) and sulfated chitosan (SCS) multilayers were coated on pure titanium using a layer-by-layer (LBL) self-assembly technique. The Col-SCS multilayer growth was carried out by first depositing a single layer of positively charged poly-L-lysine (PLL) on the NaOH-treated titanium substrate (negatively charged surface), followed by alternate deposition of negatively charged SCS and positively charged Col, and terminated by an outermost layer of SCS. Platelet adhesion in vitro, partial activated thromboplastin time (APTT) and prothrombin time (PT) assays were used to evaluate the hemocompatibility of the Col-SCS multilayer coated titanium. The multilayer processed surfaces displayed reduced platelet adhesion and activation, and prolonged clotting time of APTT and PT compared with untreated titanium. Thus, the approach described here may provide a basis for the preparation of modified titanium surfaces for application in cardiovascular implants. 2008 Wiley Periodicals, Inc.

  4. Titanium Surface Priming with Phase-Transited Lysozyme to Establish a Silver Nanoparticle-Loaded Chitosan/Hyaluronic Acid Antibacterial Multilayer via Layer-by-Layer Self-Assembly.

    Directory of Open Access Journals (Sweden)

    Xue Zhong

    Full Text Available The formation of biofilm around implants, which is induced by immediate bacterial colonization after installation, is the primary cause of post-operation infection. Initial surface modification is usually required to incorporate antibacterial agents on titanium (Ti surfaces to inhibit biofilm formation. However, simple and effective priming methods are still lacking for the development of an initial functional layer as a base for subsequent coatings on titanium surfaces. The purpose of our work was to establish a novel initial layer on Ti surfaces using phase-transited lysozyme (PTL, on which multilayer coatings can incorporate silver nanoparticles (AgNP using chitosan (CS and hyaluronic acid (HA via a layer-by-layer (LbL self-assembly technique.In this study, the surfaces of Ti substrates were primed by dipping into a mixture of lysozyme and tris(2-carboxyethylphosphine (TCEP to obtain PTL-functionalized Ti substrates. The subsequent alternating coatings of HA and chitosan loaded with AgNP onto the precursor layer of PTL were carried out via LbL self-assembly to construct multilayer coatings on Ti substrates.The results of SEM and XPS indicated that the necklace-like PTL and self-assembled multilayer were successfully immobilized on the Ti substrates. The multilayer coatings loaded with AgNP can kill planktonic and adherent bacteria to 100% during the first 4 days. The antibacterial efficacy of the samples against planktonic and adherent bacteria achieved 65%-90% after 14 days. The sustained release of Ag over 14 days can prevent bacterial invasion until mucosa healing. Although the AgNP-containing structure showed some cytotoxicity, the toxicity can be reduced by controlling the Ag release rate and concentration.The PTL priming method provides a promising strategy for fabricating long-term antibacterial multilayer coatings on titanium surfaces via the LbL self-assembly technique, which is effective in preventing implant-associated infections

  5. Titanium Surface Priming with Phase-Transited Lysozyme to Establish a Silver Nanoparticle-Loaded Chitosan/Hyaluronic Acid Antibacterial Multilayer via Layer-by-Layer Self-Assembly.

    Science.gov (United States)

    Zhong, Xue; Song, Yunjia; Yang, Peng; Wang, Yao; Jiang, Shaoyun; Zhang, Xu; Li, Changyi

    2016-01-01

    The formation of biofilm around implants, which is induced by immediate bacterial colonization after installation, is the primary cause of post-operation infection. Initial surface modification is usually required to incorporate antibacterial agents on titanium (Ti) surfaces to inhibit biofilm formation. However, simple and effective priming methods are still lacking for the development of an initial functional layer as a base for subsequent coatings on titanium surfaces. The purpose of our work was to establish a novel initial layer on Ti surfaces using phase-transited lysozyme (PTL), on which multilayer coatings can incorporate silver nanoparticles (AgNP) using chitosan (CS) and hyaluronic acid (HA) via a layer-by-layer (LbL) self-assembly technique. In this study, the surfaces of Ti substrates were primed by dipping into a mixture of lysozyme and tris(2-carboxyethyl)phosphine (TCEP) to obtain PTL-functionalized Ti substrates. The subsequent alternating coatings of HA and chitosan loaded with AgNP onto the precursor layer of PTL were carried out via LbL self-assembly to construct multilayer coatings on Ti substrates. The results of SEM and XPS indicated that the necklace-like PTL and self-assembled multilayer were successfully immobilized on the Ti substrates. The multilayer coatings loaded with AgNP can kill planktonic and adherent bacteria to 100% during the first 4 days. The antibacterial efficacy of the samples against planktonic and adherent bacteria achieved 65%-90% after 14 days. The sustained release of Ag over 14 days can prevent bacterial invasion until mucosa healing. Although the AgNP-containing structure showed some cytotoxicity, the toxicity can be reduced by controlling the Ag release rate and concentration. The PTL priming method provides a promising strategy for fabricating long-term antibacterial multilayer coatings on titanium surfaces via the LbL self-assembly technique, which is effective in preventing implant-associated infections in the

  6. Heparin-mimicking multilayer coating on polymeric membrane via LbL assembly of cyclodextrin-based supramolecules.

    Science.gov (United States)

    Deng, Jie; Liu, Xinyue; Ma, Lang; Cheng, Chong; Shi, Wenbin; Nie, Chuanxiong; Zhao, Changsheng

    2014-12-10

    In this study, multifunctional and heparin-mimicking star-shaped supramolecules-deposited 3D porous multilayer films with improved biocompatibility were fabricated via a layer-by-layer (LbL) self-assembly method on polymeric membrane substrates. Star-shaped heparin-mimicking polyanions (including poly(styrenesulfonate-co-sodium acrylate; Star-PSS-AANa) and poly(styrenesulfonate-co-poly(ethylene glycol)methyl ether methacrylate; Star-PSS-EGMA)) and polycations (poly(methyl chloride-quaternized 2-(dimethylamino)ethyl methacrylate; Star-PMeDMA) were first synthesized by atom transfer radical polymerization (ATRP) from β-cyclodextrin (β-CD) based cores. Then assembly of 3D porous multilayers onto polymeric membrane surfaces was carried out by alternating deposition of the polyanions and polycations via electrostatic interaction. The surface morphology and composition, water contact angle, blood activation, and thrombotic potential as well as cell viability for the coated heparin-mimicking films were systematically investigated. The results of surface ATR-FTIR spectra and XPS spectra verified successful deposition of the star-shaped supramolecules onto the biomedical membrane surfaces; scanning electron microscopy (SEM) and atomic force microscopy (AFM) observations revealed that the modified substrate had 3D porous surface morphology, which might have a great biological influence on the biointerface. Furthermore, systematic in vitro investigation of protein adsorption, platelet adhesion, human platelet factor 4 (PF4, indicates platelet activation), activate partial thromboplastin time (APTT), thrombin time (TT), coagulation activation (thrombin-antithrombin III complex (TAT, indicates blood coagulant)), and blood-related complement activation (C3a and C5a, indicates inflammation potential) confirmed that the heparin-mimicking multilayer coated membranes exhibited ultralow blood component activations and excellent hemocompatibility. Meanwhile, after surface coating

  7. Layer-by-layer self-assembled multilayers on PEEK implants improve osseointegration in an osteoporosis rabbit model.

    Science.gov (United States)

    Liu, Xilin; Han, Fei; Zhao, Peng; Lin, Chao; Wen, Xuejun; Ye, Xiaojian

    2017-05-01

    This study aims to fabricate and deposit nanoscale multilayers on polyetheretherketone (PEEK) to improve cell adhesion and osseointegration. Bio-activated PEEK constructs were designed with prepared surface of different layers of polystyrene sulfonate (PSS) and polyallylamine hydrochloride (PAH) multilayers. Irregular morphology was found on the 5 and 10-layer PEEK surfaces, while "island-like" clusters were observed for 20-layer (20 L) multilayers. Besides, the 20 L PEEK showed more hydrophilic feature than native PEEK, and the surface contact angle reduced from 39.7° to 21.7° as layers increased from 5 to 20. In vitro, modified PEEK allowed excellent adhesion and proliferation of bone marrow stromal cells, and induced higher cell growth rate and alkaline phosphatase level. In vivo, this bio-active PEEK exhibited significantly enhanced integration with bone tissue in an osteoporosis rabbit model. This work highlights layer-by-layer self-assembly as a practical method to construct bio-active PEEK implants for enhanced osseointegration. Copyright © 2017 Elsevier Inc. All rights reserved.

  8. [Method of multilayer assembly as alternative to antibacterial coverings of medicobiological implants].

    Science.gov (United States)

    Ospanova, A K; Omarova, R A; Abdurazakov, U A; Zhartybaev, R N; Iskakova, M K; Savdenbekova, B E; Amkhadova, M A

    2016-01-01

    Department of Traumatology and Orthopedics Almaty Kazakh Medical University of Continuing Education; 4. Moscow Regional Research Clinical Institute, Russia Resume: in this report we present the results on the use of the method of layer-by-layer (LbL) for obtaining antimicrobial coatings for biomedical implants. As the substrates were used silicon titanium implants and silicon plate. For the obtaining multilayer coatings on the surfaces of the samples were used as the polycation--chitosan and polyanion--carboxymethylcellulose sodium. On the surface multilayer were deposited antibacterial preparations: Triclosan-2,4,4'trichloro-2' hydroxyphenyl ether, silver ions and iodine. Microbiological studies were conducted on the museum strains: E. coli, Candida and Staf. Preliminary antibacterial studies on these microorganisms showed high activity multilayer coating containing triclosan.

  9. Transfer function method for frequency response and damping effect of multilayer PCLD on cylindrical shell

    Science.gov (United States)

    Qiu, Q.; Fang, Z. P.; Wan, H. C.; Zheng, L.

    2013-07-01

    Based on the Donnell assumptions and linear visco-elastic theory, the constitutive equations of the cylindrical shell with multilayer Passive Constrained Layer Damping (PCLD) treatments are described. The motion equations and boundary conditions are derived by Hamilton principle. After trigonometric series expansion and Laplace transform, the state vector is introduced and the dynamic equations in state space are established. The transfer function method is used to solve the state equation. The dynamic performance including the natural frequency, the loss factor and the frequency response of clamped-clamped multi-layer PCLD cylindrical shell is obtained. The results show that multi-layer PCLD cylindrical shell is more effective than the traditional three-layer PCLD cylindrical shell in suppressing vibration and noise if the same amount of material is applied. It demonstrates a potential application of multi-layer PCLD treatments in many critical structures such as cabins of aircrafts, hulls of submarines and bodies of rockets and missiles.

  10. Can we neglect the multi-layer structure of functional networks?

    Science.gov (United States)

    Zanin, Massimiliano

    2015-07-01

    Functional networks, i.e. networks representing dynamic relationships between the components of a complex system, have been instrumental for our understanding of, among others, the human brain. Due to limited data availability, the multi-layer nature of numerous functional networks has hitherto been neglected, and nodes are endowed with a single type of links even when multiple relationships coexist at different physical levels. A relevant problem is the assessment of the benefits yielded by studying a multi-layer functional network, against the simplicity guaranteed by the reconstruction and use of the corresponding single layer projection. Here, I tackle this issue by using as a test case, the functional network representing the dynamics of delay propagation through European airports. Neglecting the multi-layer structure of a functional network has dramatic consequences on our understanding of the underlying system, a fact to be taken into account when a projection is the only available information.

  11. Electrochemical Detection of Hydrazine and 4-Nitrophenol Based on Layer-by-Layer Assembled Multilayer Films of Reduced Graphene Oxide/Gold Nanoparticles

    Directory of Open Access Journals (Sweden)

    Shuohan HUANG

    2015-05-01

    Full Text Available Based on poly sodium 4-styrenesulfonate (PSS functionalized reduced graphene oxide (RGO and polyamidoamine (PAMAM dendrimer protected gold nanoparticles (AuNPs, a novel electrochemical sensing platform for sensitive detection of 4-nitrophenol and hydrazine was fabricated via electrostatic layer-by-layer (LBL self-assembly on a gold electrode modified with a first layer of poly (diallyldimethylammonium chloride (PDDA. The resulting nanocomposites were characterized by Raman and UV-Vis spectroscopes. Besides, electrochemical measurements were employed to investigate the electrocatalytic and sensing properties of the as-prepared modified electrode. The results indicate that the LBL assembled PSS-RGO/PAMAM-AuNPs multilayer films possess excellent electrocatalytic activities towards the reduction of 4-nitrophenol (4-NP and the oxidation of hydrazine and also show good analytical performance for the amperometric detection of the potential poisonous substances. In addition, the combination of the reduced graphene oxide and gold nanoparticles in the LBL assembly films and their synergistic effect may account for the increased electrochemical activities.

  12. Interface and surface formation in self-assembled polymer multilayers by off-specular neutron scattering

    CERN Document Server

    Lauter-Pasyuk, V; Toperverg, B P; Petrenko, A; Aksenov, V; Schubert, D; Schreiber, J; Burcin, M

    2002-01-01

    Free-surface and interface properties of a polystyrene-polybuthylmethacrylate multilayer film are studied by neutron specular reflection and off-specular scattering. Experimental data collected over a broad range of incoming and outgoing wave vectors are fitted by a theoretical model that delivers a set of parameters characterizing the state of the outermost layer as well as the conformal roughness of the interfaces. (orig.)

  13. ITO electrode modified by self-assembling multilayer film of polyoxometallate on poly(vinyl alcohol) nanofibers and its electrocatalytic behavior

    Energy Technology Data Exchange (ETDEWEB)

    Shan, Yuping; Sun, Yongling; Gong, Jian; Su, Zhongmin; Qu, Lunyu [Northeast Normal University, Changchun (China). Key Laboratory of Polyoxometalates Science of Ministry of Education; Yang, Guocheng [Northeast Normal University, Changchun (China). Key Laboratory of Polyoxometalates Science of Ministry of Education; Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun (China). State Key Laboratory of Electroanalytical Chemistry; Pang, Shujie [Jilin University, Changchun (China). College of Chemistry, Key Lab of Supramolecular Structure and Materials

    2007-12-01

    Poly(vinyl alcohol) (PVA) nanofiber mats were collected on indium tin oxide (ITO) substrate by electrospinning method. A multilayer film composed of {alpha}-[P{sub 2}W{sub 18}O{sub 62}]{sup 6-} (abbr. P{sub 2}W{sub 18}), a polyoxometallate (POM) anion, and poly(diallymethylammonium chloride) (abbr. PDDA) was fabricated by layer-by-layer (LBL) self-assembly technique on the PVA/ITO electrode. The PDDA/P{sub 2}W{sub 18} multilayer film could be unselectively or selectively deposited on the PVA/ITO electrode via changing the amount of PVA nanofibers on the ITO substrate. The scanning electron microscope (SEM) images showed that when the electrospun time was short the PDDA/P{sub 2}W{sub 18} multilayer film was unselectively deposited on PVA nanofiber mats because the amount of PVA nanofibers was too little to cover most of the ITO substrate. However, when the electrospun time was long enough, the PDDA/P{sub 2}W{sub 18} multilayer film was selectively deposited on PVA nanofiber mats because of the larger surface area and higher surface energy of PVA nanofibers in comparison with the flat ITO substrate. Growth process of the multilayer film was determined by cyclic voltammetry (CV). Electrocatalytic effects of the PDDA/P{sub 2}W{sub 18} multilayer film unselectively and selectively deposited on the PVA/ITO electrode on NO{sub 2}{sup -} were observed. (author)

  14. ITO electrode modified by self-assembling multilayer film of polyoxometallate on poly(vinyl alcohol) nanofibers and its electrocatalytic behavior

    Energy Technology Data Exchange (ETDEWEB)

    Shan Yuping [Key Laboratory of Polyoxometalates Science of Ministry of Education, Northeast Normal University, Changchun 130024 (China); Yang Guocheng [Key Laboratory of Polyoxometalates Science of Ministry of Education, Northeast Normal University, Changchun 130024 (China); State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Sun Yongling [Key Laboratory of Polyoxometalates Science of Ministry of Education, Northeast Normal University, Changchun 130024 (China); Pang Shujie [Key Lab of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130023 (China); Gong Jian [Key Laboratory of Polyoxometalates Science of Ministry of Education, Northeast Normal University, Changchun 130024 (China)], E-mail: gongj823@nenu.edu.cn; Su Zhongmin; Qu Lunyu [Key Laboratory of Polyoxometalates Science of Ministry of Education, Northeast Normal University, Changchun 130024 (China)

    2007-12-01

    Poly(vinyl alcohol) (PVA) nanofiber mats were collected on indium tin oxide (ITO) substrate by electrospinning method. A multilayer film composed of {alpha}-[P{sub 2}W{sub 18}O{sub 62}]{sup 6-} (abbr. P{sub 2}W{sub 18}), a polyoxometallate (POM) anion, and poly(diallymethylammonium chloride) (abbr. PDDA) was fabricated by layer-by-layer (LBL) self-assembly technique on the PVA/ITO electrode. The PDDA/P{sub 2}W{sub 18} multilayer film could be unselectively or selectively deposited on the PVA/ITO electrode via changing the amount of PVA nanofibers on the ITO substrate. The scanning electron microscope (SEM) images showed that when the electrospun time was short the PDDA/P{sub 2}W{sub 18} multilayer film was unselectively deposited on PVA nanofiber mats because the amount of PVA nanofibers was too little to cover most of the ITO substrate. However, when the electrospun time was long enough, the PDDA/P{sub 2}W{sub 18} multilayer film was selectively deposited on PVA nanofiber mats because of the larger surface area and higher surface energy of PVA nanofibers in comparison with the flat ITO substrate. Growth process of the multilayer film was determined by cyclic voltammetry (CV). Electrocatalytic effects of the PDDA/P{sub 2}W{sub 18} multilayer film unselectively and selectively deposited on the PVA/ITO electrode on NO{sub 2}{sup -} were observed.

  15. An electrochemical aptasensor for chiral peptide detection using layer-by-layer assembly of polyelectrolyte-methylene blue/polyelectrolyte-graphene multilayer

    Energy Technology Data Exchange (ETDEWEB)

    Qin Haixia; Liu Jiyang; Chen Chaogui [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Wang Jiahi, E-mail: jhwang@ciac.jl.cn [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Wang Erkang, E-mail: ekwang@ciac.jl.cn [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)

    2012-01-27

    Highlights: Black-Right-Pointing-Pointer An electrochemical aptasensor for selective detection of peptide is constructed. Black-Right-Pointing-Pointer This aptasensor is based on grapheme multilayer via layer-by-layer assembly. Black-Right-Pointing-Pointer Such multilayer facilitates electron transfer and provides more adsorption sites. - Abstract: Here we demonstrate for the first time that by physically adsorbing aptamer onto conductive film assembled via alternate adsorption of graphene/polyelectrolyte and methylene blue/polyelectrolyte, a label-free electrochemical aptasensor with high sensitivity and selectivity for peptide detection is constructed. Graphene multilayer derived from layer-by-layer assembly has played significant roles in this sensing strategy: allowing accumulation of methylene blue, facilitating electron transfer and providing much more adsorption site. As compared to previous electrochemical aptasensors, the current sensor based on graphene multilayer alternated with electroactive molecule layer offers extremely high capability for sensitive detection of target without interference of environmental surrounding. This electroactive probe-confined graphene multilayer confers great flexibility to combine with differential pulse voltammetry (DPV) together. In the presence of target D entiomer of arginine vasopressin (D-VP), the binding of peptide to aptamer block the electron transfer process of MB, leading to decreased current peak of DPV. By this way, this electrochemical aptasensor based on electroactive molecule-intercalated graphene multilayer provide highly sensitive and specific detection of D-VP with the lowest detectable concentration of 1 ng mL{sup -1} and a wide detection range from 1 to 265 ng mL{sup -1}.

  16. Functional connectivity in in vitro neuronal assemblies

    Science.gov (United States)

    Poli, Daniele; Pastore, Vito P.; Massobrio, Paolo

    2015-01-01

    Complex network topologies represent the necessary substrate to support complex brain functions. In this work, we reviewed in vitro neuronal networks coupled to Micro-Electrode Arrays (MEAs) as biological substrate. Networks of dissociated neurons developing in vitro and coupled to MEAs, represent a valid experimental model for studying the mechanisms governing the formation, organization and conservation of neuronal cell assemblies. In this review, we present some examples of the use of statistical Cluster Coefficients and Small World indices to infer topological rules underlying the dynamics exhibited by homogeneous and engineered neuronal networks. PMID:26500505

  17. Metal-molecular assembly for functional materials

    CERN Document Server

    Matsuo, Yutaka; Negishi, Yuichi; Yoshizawa, Michito; Uemura, Takashi; Takaya, Hikaru; Takeuchi, Masayuki; Yoshimoto, Soichiro

    2013-01-01

    This book focuses on modern coordination chemistry, covering porous coordination polymers, metalloproteins, metallopeptides, nanoclusters, nanocapsules, aligned polymers, and fullerenes. As well, it deals with applications to electronic devices and surface characterization. These wide-ranging topics are integrally described from the perspectives of dimensionality (one-, two-, and three-dimension), new materials design, synthesis, molecular assembly, function and application. The nine chapters making up this book have been authored by scientists who are at the cutting edge of research in this p

  18. Modelling of migration from multi-layers and functional barriers: Estimation of parameters

    NARCIS (Netherlands)

    Dole, P.; Voulzatis, Y.; Vitrac, O.; Reynier, A.; Hankemeier, T.; Aucejo, S.; Feigenbaum, A.

    2006-01-01

    Functional barriers form parts of multi-layer packaging materials, which are deemed to protect the food from migration of a broad range of contaminants, e.g. those associated with reused packaging. Often, neither the presence nor the identity of the contaminants is known, so that safety assessment

  19. Self-assembled Multilayers of Silica Nanospheres for Defect Reduction in Non- and Semipolar Gallium Nitride Epitaxial Layers.

    Science.gov (United States)

    Zhu, Tongtong; Ding, Tao; Tang, Fengzai; Han, Yisong; Ali, Muhammad; Badcock, Tom; Kappers, Menno J; Shields, Andrew J; Smoukov, Stoyan K; Oliver, Rachel A

    2016-02-03

    Non- and semipolar GaN have great potential to improve the efficiency of light emitting devices due to much reduced internal electric fields. However, heteroepitaxial GaN growth in these crystal orientations suffers from very high dislocation and stacking faults densities. Here, we report a facile method to obtain low defect density non- and semipolar heteroepitaxial GaN via selective area epitaxy using self-assembled multilayers of silica nanospheres (MSN). Nonpolar (11-20) and semipolar (11-22) GaN layers with high crystal quality have been achieved by epitaxial integration of the MSN and a simple one-step overgrowth process, by which both dislocation and basal plane stacking fault densities can be significantly reduced. The underlying defect reduction mechanisms include epitaxial growth through the MSN covered template, island nucleation via nanogaps in the MSN, and lateral overgrowth and coalescence above the MSN. InGaN/GaN multiple quantum wells structures grown on a nonpolar GaN/MSN template show more than 30-fold increase in the luminescence intensity compared to a control sample without the MSN. This self-assembled MSN technique provides a new platform for epitaxial growth of nitride semiconductors and offers unique opportunities for improving the material quality of GaN grown on other orientations and foreign substrates or heteroepitaxial growth of other lattice-mismatched materials.

  20. Functionalized fullerenes in self-assembled monolayers.

    Science.gov (United States)

    Gimenez-Lopez, Maria del Carmen; Räisänen, Minna T; Chamberlain, Thomas W; Weber, Uli; Lebedeva, Maria; Rance, Graham A; Briggs, G Andrew D; Pettifor, David; Burlakov, Victor; Buck, Manfred; Khlobystov, Andrei N

    2011-09-06

    Anisotropy of intermolecular and molecule-substrate interactions holds the key to controlling the arrangement of fullerenes into 2D self-assembled monolayers (SAMs). The chemical reactivity of fullerenes allows functionalization of the carbon cages with sulfur-containing groups, thiols and thioethers, which facilitates the reliable adsorption of these molecules on gold substrates. A series of structurally related molecules, eight of which are new fullerene compounds, allows systematic investigation of the structural and functional parameters defining the geometry of fullerene SAMs. Scanning tunnelling microscopy (STM) measurements reveal that the chemical nature of the anchoring group appears to be crucial for the long-range order in fullerenes: the assembly of thiol-functionalized fullerenes is governed by strong molecule-surface interactions, which prohibit formation of ordered molecular arrays, while thioether-functionalized fullerenes, which have a weaker interaction with the surface than the thiols, form a variety of ordered 2D molecular arrays owing to noncovalent intermolecular interactions. A linear row of fullerene molecules is a recurring structural feature of the ordered SAMs, but the relative alignment and the spacing between the fullerene rows is strongly dependent on the size and shape of the spacer group linking the fullerene cage and the anchoring group. Careful control of the chemical functionality on the carbon cages enables positioning of fullerenes into at least four different packing arrangements, none of which have been observed before. Our new strategy for the controlled arrangement of fullerenes on surfaces at the molecular level will advance the development of practical applications for these nanomaterials. © 2011 American Chemical Society

  1. Unlocking Function of Aramid Fibers in Multilayered Ballistic Armor

    Science.gov (United States)

    Monteiro, Sergio N.; Lima, Édio P.; Louro, Luis Henrique L.; da Silva, Luis Carlos; Drelich, Jaroslaw W.

    2015-01-01

    Aramid fabric plies were ballistic tested using high impact 7.62 × 51 mm ammunition in two distinct conditions: (1) as a common multilayered armor system (MAS) component backing a front Al2O3-based tile, and (2) with the same plies thickness, as a single target. Single targets of the ceramic tile and the aluminum sheet (MAS third layer) were also tested. In the MAS, the aramid dissipated more than 36 pct of the impact energy during the test compared with only ~2 pct when separated from the MAS. Microscopic examination of aramid fabric revealed many ceramic fragments with a size of a few micrometers that coated surfaces of fibers. It is shown for the first time that, in addition to already reported fabric rupture, debonding, and stretching, a massive incrustation of ceramic fragments onto the fabric fibers might be responsible for the comparatively high aramid ballistic performance as the MAS component. Besides the mechanical incrustation and van der Waals forces on the harder ceramic fragments, it is proposed that short-living surface static charges generated on the aramid fibers could contribute to the capturing process.

  2. Protective Coatings for Space System Components Fabricated Using Ionic Self Assembled Monolayer Processes

    National Research Council Canada - National Science Library

    Miler, Mike

    1997-01-01

    Self-assembled multilayer thin film fabrication methods offer unique opportunities to incorporate multiple functionalities into coatings for space system materials and structures as well as consumer products...

  3. Functional, Responsive Materials Assembled from Recombinant Oleosin

    Science.gov (United States)

    Hammer, Daniel

    Biological cells are surrounded by a plasma membrane made primarily of phospholipids that form a bilayer. This membrane is permselective and compartmentalizes the cell. A simple form of artificial cell is the vesicle, in which a phospholipid bilayer membrane surrounds an aqueous solution. However, there is no a priori reason why a membrane needs to be made of phospholipids. It could be made of any surfactant that forms a bilayer. We have assembled membranes and other structures from the recombinant plant protein oleosin. The ability to assemble from a recombinant protein means that every molecule is identical, we have complete control over the sequence, and hence can build in designer functionality with high fidelity, including adhesion and enzymatic activity. Such incorporation is trivial using the tools of molecular biology. We find that while many variants of oleosin make membranes, others make micelles and sheets. We show how the type of supramolecular structure can be altered by the conditions of solvent, such as ionic strength, and the architecture of the surfactant itself. We show that protease cleavable domains can be incorporated within oleosin, and be engineered to protect other functional domains such as adhesive motifs, to make responsive materials whose activity and shape depend on the action of proteases. We will also present the idea of making ``Franken''-oleosins, where large domains of native oleosin are replaced with domains from other functional proteins, to make hybrids conferred by the donor protein. Thus, we can view oleosin as a template upon which a vast array of designer functionalities can be imparted..

  4. Multilayered Films Produced by Layer-by-Layer Assembly of Chitosan and Alginate as a Potential Platform for the Formation of Human Adipose-Derived Stem Cell aggregates

    Directory of Open Access Journals (Sweden)

    Javad Hatami

    2017-09-01

    Full Text Available The construction of multilayered films with tunable properties could offer new routes to produce biomaterials as a platform for 3D cell cultivation. In this study, multilayered films produced with five bilayers of chitosan and alginate (CHT/ALG were built using water-soluble modified mesyl and tosyl–CHT via layer-by-layer (LbL self-assembly. NMR results demonstrated the presences of mesyl (2.83 ppm and tosyl groups (2.39, 7.37 and 7.70 ppm in the chemical structure of modified chitosans. The buildup of multilayered films was monitored by quartz-crystal-microbalance (QCM-D and film thickness was estimated using the Voigt-based viscoelastic model. QCM-D results demonstrated that CHT/ALG films constructed using mesyl or tosyl modifications (mCHT/ALG were significantly thinner in comparison to the CHT/ALG films constructed with unmodified chitosan (p < 0.05. Adhesion analysis demonstrated that human adipose stem cells (hASCs did not adhere to the mCHT/ALG multilayered films and formed aggregates with sizes between ca. 100–200 µm. In vitro studies on cell metabolic activity and live/dead staining suggested that mCHT/ALG multilayered films are nontoxic toward hACSs. Multilayered films produced via LbL assembly of ALG and off-the-shelf, water-soluble modified chitosans could be used as a scaffold for the 3D aggregates formation of hASCs in vitro.

  5. Anisotropic nanomaterials: structure, growth, assembly, and functions

    Science.gov (United States)

    Sajanlal, Panikkanvalappil R.; Sreeprasad, Theruvakkattil S.; Samal, Akshaya K.; Pradeep, Thalappil

    2011-01-01

    Comprehensive knowledge over the shape of nanomaterials is a critical factor in designing devices with desired functions. Due to this reason, systematic efforts have been made to synthesize materials of diverse shape in the nanoscale regime. Anisotropic nanomaterials are a class of materials in which their properties are direction-dependent and more than one structural parameter is needed to describe them. Their unique and fine-tuned physical and chemical properties make them ideal candidates for devising new applications. In addition, the assembly of ordered one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) arrays of anisotropic nanoparticles brings novel properties into the resulting system, which would be entirely different from the properties of individual nanoparticles. This review presents an overview of current research in the area of anisotropic nanomaterials in general and noble metal nanoparticles in particular. We begin with an introduction to the advancements in this area followed by general aspects of the growth of anisotropic nanoparticles. Then we describe several important synthetic protocols for making anisotropic nanomaterials, followed by a summary of their assemblies, and conclude with major applications. PMID:22110867

  6. The effect of polysaccharide types on adsorption properties of LbL assembled multilayer films.

    Science.gov (United States)

    Xu, Jie; Yang, Lixing; Hu, Xiaoxia; Xu, Shimei; Wang, Jide; Feng, Shun

    2015-03-07

    Three types of biocompatible films were fabricated via electrostatic layer-by-layer (LbL) adsorption of oppositely charged cationic polyurethane and anionic polysaccharides with different primary structures, including sodium hyaluronate, sodium carboxymethyl cellulose and sodium alginate. The adsorption behaviors of films were investigated by using the cationic dye methylene blue (MB) as a model drug at various pH values and salt concentrations. The relationship between the type of polysaccharide and the adsorption behavior of LbL films was comparatively studied. It was found that the adsorption capacity increased with an increase of the initial concentration of MB in the concentration range of the experiment to all of the films, and the pH of environment ranged from 3.0 to 9.0. The Langmuir equation fit perfectly to the experiment data. In addition, a pseudo second-order adsorption model can well describe the adsorption behaviors of MB for three films. The results showed that the type of side chains and the charge density of the polysaccharides played key roles in the adsorption properties of the PU/polysaccharide multilayer films.

  7. Fabrication of dopamine-modified hyaluronic acid/chitosan multilayers on titanium alloy by layer-by-layer self-assembly for promoting osteoblast growth

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xinming, E-mail: xmzhang@tju.edu.cn [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Li, Zhaoyang, E-mail: zyli@tju.edu.cn [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Tianjin Key Laboratory of Composite and Functional Materials, Tianjin 300072 (China); Yuan, Xubo [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Cui, Zhenduo; Yang, Xianjin [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Tianjin Key Laboratory of Composite and Functional Materials, Tianjin 300072 (China)

    2013-11-01

    The bare inert surface of titanium (Ti) alloy typically causes early failures in implants. Layer-by-layer self-assembly is one of the simple methods for fabricating bioactive multilayer coatings on titanium implants. In this study, a dopamine-modified hyaluronic acid/chitosan (DHA/CHI) bioactive multilayer was built on the surface of Ti–24Nb–2Zr (TNZ) alloy. Zeta potential oscillated between −2 and 17 mV for DHA- and CHI-ending layers during the assembly process, respectively. The DHA/CHI multilayer considerably decreased the contact angle and dramatically improved the wettability of TNZ alloy. Atomic force microscopy results revealed a rough surface on the original TNZ alloy, while the surface became smoother and more homogeneous after the deposition of approximately 5 bilayers (TNZ/(DHA/CHI){sub 5}). X-ray photoelectron spectroscopy analysis indicated that the TNZ/(DHA/CHI){sub 5} sample was completely covered by polyelectrolytes. Pre-osteoblast MC3T3-E1 cells were cultured on the original TNZ alloy and TNZ/(DHA/CHI){sub 5} to evaluate the effects of DHA/CHI multilayer on osteoblast proliferation in vitro. The proliferation of osteoblasts on TNZ/(DHA/CHI){sub 5} was significantly higher than that on the original TNZ alloy. The results of this study indicate that the proposed technique improves the biocompatibility of TNZ alloy and can serve as a potential modification method in orthopedic applications.

  8. Nanopatterning of Co/Pt-multilayers via self-assembled block-copolymer micelles; Magnetische Nanostrukturen basierend auf Co/Pt-Multilagen, hergestellt mittels selbstorganisierter Masken aus Blockcopolymer-Micellen

    Energy Technology Data Exchange (ETDEWEB)

    Stillrich, H.

    2007-07-01

    The production and characterization of magnetic nanostructures based on Co/Ptmultilayers are described in this thesis. Nanostructure arrays of Co/Pt multilayer films are generated utilizing the self-assembly of block copolymer micelles with a few 10nm diameter. For an understanding of the magnetic properties of nanostructures the properties of Co/Pt-multilayer films are examined first. The films are grown via different sputter techniques. The structural and magnetic properties are investigated depending on the deposition technique. The sources of magnetic anisotropy are discussed based on these investigations. One major topic concerning Co/Pt-multilayers is the reorientation of the easy axis of magnetization from perpendicular to in-plane as a function of the cobalt and platinum layer thicknesses. Combining averaging magnetization measurements and high resolution magnetic imaging, the canting of magnetization within the reorientation transition and a canted domain structure were found. The basis for magnetic nanostructures are Co/Pt-multilayers that were optimized for strong magnetic anisotropy. Magnetic antidot and dot arrays are generated from Co/Pt-multilayers via novel methods utilizing block copolymer micelle masks and ion milling. The generation of nanostructure arrays is proven by the morphologic and topographic properties, combined with the evolution of magneto-optic signals. Two different approaches for the generation of antidot arrays are shown. The magnetic properties of antidot arrays with perpendicular and in-plane easy magnetization are investigated. Magnetic dot arrays are produced utilizing the cores of SiO{sub 2} filled block copolymer micelles. The dot arrays consist of single domain particles. The switching field distribution of the dot arrays is analysed and described using the size distribution of the magnetic particles. Magnetic nanostructures in the region of the superparamagnetic limit are investigated. (orig.)

  9. Surface Modification and Characterisation of Silk Fibroin Fabric Produced by the Layer-by-Layer Self-Assembly of Multilayer Alginate/Regenerated Silk Fibroin.

    Directory of Open Access Journals (Sweden)

    Gaotian Shen

    Full Text Available Silk-based medical products have a long history of use as a material for surgical sutures because of their desirable mechanical properties. However, silk fibroin fabric has been reported to be haemolytic when in direct contact with blood. The layer-by-layer self-assembly technique provides a method for surface modification to improve the biocompatibility of silk fibroin fabrics. Regenerated silk fibroin and alginate, which have excellent biocompatibility and low immunogenicity, are outstanding candidates for polyelectrolyte deposition. In this study, silk fabric was degummed and positively charged to create a silk fibroin fabric that could undergo self-assembly. The multilayer self-assembly of the silk fibroin fabric was achieved by alternating the polyelectrolyte deposition of a negatively charged alginate solution (pH = 8 and a positively charged regenerated silk fibroin solution (pH = 2. Finally, the negatively charged regenerated silk fibroin solution (pH = 8 was used to assemble the outermost layer of the fabric so that the surface would be negatively charged. A stable structural transition was induced using 75% ethanol. The thickness and morphology were characterised using atomic force microscopy. The properties of the self-assembled silk fibroin fabric, such as the bursting strength, thermal stability and flushing stability, indicated that the fabric was stable. In addition, the cytocompatibility and haemocompatibility of the self-assembled silk fibroin fabrics were evaluated. The results indicated that the biocompatibility of the self-assembled multilayers was acceptable and that it improved markedly. In particular, after the self-assembly, the fabric was able to prevent platelet adhesion. Furthermore, other non-haemolytic biomaterials can be created through self-assembly of more than 1.5 bilayers, and we propose that self-assembled silk fibroin fabric may be an attractive candidate for anticoagulation applications and for promoting

  10. Study and Optimization of Self-Assembled Polymeric Multilayer Structures with Neutral Red for pH Sensing Applications

    Directory of Open Access Journals (Sweden)

    Javier Goicoechea

    2008-01-01

    Full Text Available The characterization of nanostructured thin films is critical in the design and fabrication of optical sensors. Particularly, this work is a detailed study of the properties of layer-by-layer electrostatic self-assembled multilayer (LbL structures fabricated using poly(allylamine hydrochloride (PAH and Neutral Red (NR as cations, and poly(acrylic acid (PAA as polyanion. These LbL films, due to the colorimetric properties of the NR, are suitable for sensor applications such as pH sensing in the physiological range. In the (PAH+NR/PAA LbL structure, it has been observed a very important influence of the pH of the solutions in the properties of the resultant films. Different techniques such as spectroscopy and atomic force microscopy (AFM are combined to characterize the films, and the results are analyzed showing coherence with previous works. The LbL structure is finally optimized and dramatically improved nanostructured films were fabricated, showing good sensing properties, short response times, and good stability.

  11. Functional Self-Assembled Nanofibers by Electrospinning

    Science.gov (United States)

    Greiner, A.; Wendorff, J. H.

    Electrospinning constitutes a unique technique for the production of nanofibers with diameters down to the range of a few nanometers. In strong contrast to conventional fiber producing techniques, it relies on self-assembly processes driven by the Coulomb interactions between charged elements of the fluids to be spun to nanofibers. The transition from a macroscopic fluid object such as a droplet emerging from a die to solid nanofibers is controlled by a set of complex physical instability processes. They give rise to extremely high extensional deformations and strain rates during fiber formation causing among others a high orientational order in the nanofibers as well as enhanced mechanical properties. Electrospinning is predominantly applied to polymer based materials including natural and synthetic polymers, but, more recently, its use has been extended towards the production of metal, ceramic and glass nanofibers exploiting precursor routes. The nanofibers can be functionalized during electrospinning by introducing pores, fractal surfaces, by incorporating functional elements such as catalysts, quantum dots, drugs, enzymes or even bacteria. The production of individual fibers, random nonwovens, or orientationally highly ordered nonwovens is achieved by an appropriate selection of electrode configurations. Broad areas of application exist in Material and Life Sciences for such nanofibers, including not only optoelectronics, sensorics, catalysis, textiles, high efficiency filters, fiber reinforcement but also tissue engineering, drug delivery, and wound healing. The basic electrospinning process has more recently been extended towards compound co-electrospinning and precision deposition electrospinning to further broaden accessible fiber architectures and potential areas of application.

  12. Multi-layer canard cycles and translated power functions (vol 244, pg 1329, 2008) Correction

    OpenAIRE

    Dumortier, Freddy; Roussarie, Robert

    2008-01-01

    The paper deals with two-dimensional slow-fast systems and more specifically with multi-layer canard cycles. These are canard cycles passing through n layers of fast orbits, with n⩾2. The canard cycles are subject to n generic breaking mechanisms and we study the limit cycles that can be perturbed from the generic canard cycles of codimension n. We prove that this study can be reduced to the investigation of the fixed points of iterated translated power functions.

  13. A three-dimensional vertically aligned functionalized multilayer graphene architecture: an approach for graphene-based thermal interfacial materials.

    Science.gov (United States)

    Liang, Qizhen; Yao, Xuxia; Wang, Wei; Liu, Yan; Wong, Ching Ping

    2011-03-22

    Thermally conductive functionalized multilayer graphene sheets (fMGs) are efficiently aligned in large-scale by a vacuum filtration method at room temperature, as evidenced by SEM images and polarized Raman spectroscopy. A remarkably strong anisotropy in properties of aligned fMGs is observed. High electrical (∼386 S cm(-1)) and thermal conductivity (∼112 W m(-1) K(-1) at 25 °C) and ultralow coefficient of thermal expansion (∼-0.71 ppm K(-1)) in the in-plane direction of A-fMGs are obtained without any reduction process. Aligned fMGs are vertically assembled between contacted silicon/silicon surfaces with pure indium as a metallic medium. Thus-constructed three-dimensional vertically aligned fMG thermal interfacial material (VA-fMG TIM) architecture has significantly higher equivalent thermal conductivity (75.5 W m(-1) K(-1)) and lower contact thermal resistance (5.1 mm2 K W(-1)), compared with their counterpart from A-fMGs that are recumbent between silicon surfaces. This finding provides a throughout approach for a graphene-based TIM assembly as well as knowledge of vertically aligned graphene architectures, which may not only facilitate graphene's application in current demanding thermal management but also promote its widespread applications in electrodes of energy storage devices, conductive polymeric composites, etc.

  14. Master stability functions reveal diffusion-driven instabilities in multi-layer networks

    CERN Document Server

    Brechtel, Andreas; Ritterskamp, Daniel; Drossel, Barbara; Gross, Thilo

    2016-01-01

    Many systems in science and technology can be described as multilayer networks, which are known to exhibit phenomena such as catastrophic failure cascades and pattern-forming instabilities. A particular class of multilayer networks describes systems where different interacting copies of a local network exist in different spatial locations, including for instance regulatory and metabolic networks of identical cells and interacting habitats of ecological populations. Here, we show that such systems can be analyzed by a master stability function (MSF) approach, which reveals conditions for diffusion-driven instabilities (DDIs). We demonstrate the methodology on the example of state-of-the-art meta-foodweb models, where it reveals diffusion-driven instabilities that lead to localized dynamics and spatial patterns. This type of approach can be applied to a variety of systems from nature, science and engineering to aid the understanding and design of complex self-organizing systems.

  15. Multi-layer service function chaining scheduling based on auxiliary graph in IP over optical network

    Science.gov (United States)

    Li, Yixuan; Li, Hui; Liu, Yuze; Ji, Yuefeng

    2017-10-01

    Software Defined Optical Network (SDON) can be considered as extension of Software Defined Network (SDN) in optical networks. SDON offers a unified control plane and makes optical network an intelligent transport network with dynamic flexibility and service adaptability. For this reason, a comprehensive optical transmission service, able to achieve service differentiation all the way down to the optical transport layer, can be provided to service function chaining (SFC). IP over optical network, as a promising networking architecture to interconnect data centers, is the most widely used scenarios of SFC. In this paper, we offer a flexible and dynamic resource allocation method for diverse SFC service requests in the IP over optical network. To do so, we firstly propose the concept of optical service function (OSF) and a multi-layer SFC model. OSF represents the comprehensive optical transmission service (e.g., multicast, low latency, quality of service, etc.), which can be achieved in multi-layer SFC model. OSF can also be considered as a special SF. Secondly, we design a resource allocation algorithm, which we call OSF-oriented optical service scheduling algorithm. It is able to address multi-layer SFC optical service scheduling and provide comprehensive optical transmission service, while meeting multiple optical transmission requirements (e.g., bandwidth, latency, availability). Moreover, the algorithm exploits the concept of Auxiliary Graph. Finally, we compare our algorithm with the Baseline algorithm in simulation. And simulation results show that our algorithm achieves superior performance than Baseline algorithm in low traffic load condition.

  16. Antimicrobial Hyaluronic Acid/Poly(amidoamine) Dendrimer Multilayer on Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) Prepared by a Layer-by-Layer Self-Assembly Method.

    Science.gov (United States)

    Zhan, Jiezhao; Wang, Lin; Liu, Sa; Chen, Junjian; Ren, Li; Wang, Yingjun

    2015-07-01

    In this article, we prepared hyaluronic acid/poly(amidoamine) dendrimer (HA/PAMAM) multilayers on a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-4HB)] substrate by a layer-by-layer self-assembly method for antimicrobial biomaterials. The results of ζ potential and quartz crystal microbalance with dissipation (QCM-D) showed that HA/PAMAM multilayers could be formed on the substrate layer by layer. We used QCM-D to show that both the HA outer layer and the PAMAM outer layer exhibited good protein-resistant activity to bovine serum albumin and bacterial antiadhesion activity to Escherichia coli. By a live/dead assay and the colony counting method, we found that the PAMAM outer layer could also exhibit bactericidal activity against E. coli, while the HA outer layer had no bactericidal activity. Both the bacterial antiadhesion activity and the bactericidal activity of the samples could be maintained even after storage in phosphate-buffered saline for up to 14 days. An in vitro MTT assay showed that the multilayers had no cytotoxicity to L929 cells, and HA molecules in the multilayers could improve the biocompatibility of the film.

  17. Fabrication and characterization of novel multilayered structures by stereocomplexion of poly(D-lactic acid/poly(L-lactic acid and self-assembly of polyelectrolytes

    Directory of Open Access Journals (Sweden)

    Elena Dellacasa

    2016-01-01

    Full Text Available The enantiomers poly(D-lactic acid (PDLA and poly(L-lactic acid (PLLA were alternately adsorbed directly on calcium carbonate (CaCO3 templates and on poly(styrene sulfonate (PSS and poly(allylamine hydrochloride (PAH multilayer precursors in order to fabricate a novel layer-by-layer (LBL assembly. A single layer of poly(L-lysine (PLL was used as a linker between the (PDLA/PLLAn stereocomplex and the cores with and without the polymeric (PSS/PAHn/PLL multilayer precursor (PEM. Nuclear magnetic resonance (NMR and gel permeation chromatography (GPC were used to characterize the chemical composition and molecular weight of poly(lactic acid polymers. Both multilayer structures, with and without polymeric precursor, were firstly fabricated and characterized on planar supports. A quartz crystal microbalance (QCM, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR and ellipsometry were used to evaluate the thickness and mass of the multilayers. Then, hollow, spherical microcapsules were obtained by the removal of the CaCO3 sacrificial template. The chemical composition of the obtained microcapsules was confirmed by differential scanning calorimetry (DSC and wide X-ray diffraction (WXRD analyses. The microcapsule morphology was evaluated by scanning electron microscopy (SEM and transmission electron microscopy (TEM measurements. The experimental results confirm the successful fabrication of this innovative system, and its full biocompatibility makes it worthy of further characterization as a promising drug carrier for sustained release.

  18. Enzyme-polyelectrolyte multilayer assemblies on reduced graphene oxide field-effect transistors for biosensing applications.

    Science.gov (United States)

    Piccinini, Esteban; Bliem, Christina; Reiner-Rozman, Ciril; Battaglini, Fernando; Azzaroni, Omar; Knoll, Wolfgang

    2017-06-15

    We present the construction of layer-by-layer (LbL) assemblies of polyethylenimine and urease onto reduced-graphene-oxide based field-effect transistors (rGO FETs) for the detection of urea. This versatile biosensor platform simultaneously exploits the pH dependency of liquid-gated graphene-based transistors and the change in the local pH produced by the catalyzed hydrolysis of urea. The use of an interdigitated microchannel resulted in transistors displaying low noise, high pH sensitivity (20.3µA/pH) and transconductance values up to 800 µS. The modification of rGO FETs with a weak polyelectrolyte improved the pH response because of its transducing properties by electrostatic gating effects. In the presence of urea, the urease-modified rGO FETs showed a shift in the Dirac point due to the change in the local pH close to the graphene surface. Markedly, these devices operated at very low voltages (less than 500mV) and were able to monitor urea in the range of 1-1000µm, with a limit of detection (LOD) down to 1µm, fast response and good long-term stability. The urea-response of the transistors was enhanced by increasing the number of bilayers due to the increment of the enzyme surface coverage onto the channel. Moreover, quantification of the heavy metal Cu2+(with a LOD down to 10nM) was performed in aqueous solution by taking advantage of the urease specific inhibition. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  19. Structured multilayered electrodes of proton/electron conducting polymer for polymer electrolyte membrane fuel cells assembled by spray coating

    Energy Technology Data Exchange (ETDEWEB)

    Wolz, Andre; Zils, Susanne; Roth, Christina [Institute for Materials Science, TU Darmstadt, Petersenstr. 23, D-64287 Darmstadt (Germany); Michel, Marc [Department of Advanced Materials and Structures, CRP Henri Tudor, 66 Rue de Luxembourg, L-4002 Esch-sur-Alzette (Luxembourg)

    2010-12-15

    Membrane electrode assemblies (MEAs) for fuel cell applications consist of electron conductive support materials, proton conductive ionomer, and precious metal nanoparticles to enhance the catalytic activity towards H{sub 2} oxidation and O{sub 2} reduction. An optimized connection of all three phases is required to obtain a high noble metal utilization, and accordingly a good performance. Using polyaniline (PANI) as an alternative support material, the generally used ionomer Nafion {sup registered} could be replaced in the catalyst layer. PANI has the advantage to be electron and proton conductive at the same time, and can be used as a catalyst support as well. In this study, a new technique building up alternating layers of PANI supported catalyst and single-walled carbon nanotubes (SWCNT) supported catalyst is introduced. Multilayers of PANI and SWCNT catalysts are used on the cathode side, whereas the anode side is composed of commercial platinum/carbon black catalyst and Nafion {sup registered}, applied by an airbrush. No additional Nafion {sup registered} ionomer is used for proton conductivity of the cathode. The so called spray coating method results in high power densities up to 160 mW cm{sup -2} with a Pt loading of 0.06 mg cm{sup -2} at the cathode, yielding a Pt utilization of 2663 mW mg{sub Pt}{sup -1}. As well as PANI, supports of SWCNTs have the advantage to have a fibrous structure and additional, they provide high electron conductivity. The combination of the new technique and the fibrous 1-dimensional support materials leads to a porous 3-dimensional electrode network which could enhance the gas transport through the electrode as well as the Pt utilization. The spray coating method could be upgraded to an in-line process and is not restricted to batch production. (author)

  20. On the effect of thermodynamic equilibrium on the assembly efficiency of complex multi-layered virus-like particles (VLP: the case of rotavirus VLP.

    Directory of Open Access Journals (Sweden)

    António Roldão

    Full Text Available Previous studies have reported the production of malformed virus-like-particles (VLP in recombinant host systems. Here we computationally investigate the case of a large triple-layered rotavirus VLP (RLP. In vitro assembly, disassembly and reassembly data provides strong evidence of microscopic reversibility of RLP assembly. Light scattering experimental data also evidences a slow and reversible assembly untypical of kinetic traps, thus further strengthening the fidelity of a thermodynamically controlled assembly. In silico analysis further reveals that under favourable conditions particles distribution is dominated by structural subunits and completely built icosahedra, while other intermediates are present only at residual concentrations. Except for harshly unfavourable conditions, assembly yield is maximised when proteins are provided in the same VLP protein mass composition. The assembly yield decreases abruptly due to thermodynamic equilibrium when the VLP protein mass composition is not obeyed. The latter effect is more pronounced the higher the Gibbs free energy of subunit association is and the more complex the particle is. Overall this study shows that the correct formation of complex multi-layered VLPs is restricted to a narrow range of association energies and protein concentrations, thus the choice of the host system is critical for successful assembly. Likewise, the dynamic control of intracellular protein expression rates becomes very important to minimize wasted proteins.

  1. Dispersal-Based Microbial Community Assembly Decreases Biogeochemical Function

    Energy Technology Data Exchange (ETDEWEB)

    Graham, Emily B.; Stegen, James C.

    2017-11-01

    Much research has focused on improving ecosystem models by incorporating microbial regulation of biogeochemistry. However, models still struggle to predict biogeochemical function in future scenarios linked to accelerating global environmental change. Ecological mechanisms may influence the relationship between microbial communities and biogeochemistry, and here, we show that stochastic dispersal processes (e.g., wind-driven or hydrologic transport) can suppress biogeochemical function. Microbial communities are assembled by deterministic (e.g., selection) and stochastic (e.g., dispersal) processes, and the balance of these two processes is hypothesized to influence how microbial communities correspond to biogeochemical function. We explore the theoretical basis for this hypothesis and use ecological simulation models to demonstrate potential influences of assembly processes on ecosystem function. We assemble ‘receiving’ communities under different levels of dispersal from a source community (selection-only, moderate dispersal, and homogenizing dispersal). We then calculate the degree to which assembled individuals are adapted to their environment and relate the level of adaptation to biogeochemical function. We also use ecological null models to further link assembly the level of deterministic assembly to function. We find that dispersal can decrease biogeochemical function by increasing the proportion of maladapted taxa, outweighing selection. The niche breadth of taxa is also a key determinant of biogeochemical function, suggesting a tradeoff between the function of generalist and specialist species. Together, our results highlight the importance of considering ecological assembly processes to reduce uncertainty in predictions of biogeochemical cycles under future environmental scenarios.

  2. A surface-mediated siRNA delivery system developed with chitosan/hyaluronic acid-siRNA multilayer films through layer-by-layer self-assembly

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Lijuan [Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai 200062 (China); Suzhou Novovita Bio-products Co., Ltd., Suzhou 215300 (China); Wu, Changlin, E-mail: Ph.Dclwu1314@sina.cn [Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai 200062 (China); Suzhou Novovita Bio-products Co., Ltd., Suzhou 215300 (China); Liu, Guangwan [Suzhou Novovita Bio-products Co., Ltd., Suzhou 215300 (China); Liao, Nannan [Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai 200062 (China); Suzhou Novovita Bio-products Co., Ltd., Suzhou 215300 (China); Zhao, Fang; Yang, Xuxia; Qu, Hongyuan [Suzhou Novovita Bio-products Co., Ltd., Suzhou 215300 (China); Peng, Bo [Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai 200062 (China); Chen, Li [Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai 200062 (China); Suzhou Novovita Bio-products Co., Ltd., Suzhou 215300 (China); Yang, Guang [Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai 200062 (China)

    2016-12-15

    Highlights: • We prepared Chitosan/Hyaluronic acid-siRNA multilayer as carrier to effectively load and protect siRNAs. • The stability and integrity of the siRNA was verified in the siRNA-loaded films. • The siRNA-loaded films showed good cells adhesion and gene silencing effect in eGFP-HEK 293T cells. • This is a new type of surface-mediated non-viral multilayer films. - Abstract: siRNA delivery remains highly challenging because of its hydrophilic and anionic nature and its sensitivity to nuclease degradation. Effective siRNA loading and improved transfection efficiency into cells represents a key problem. In our study, we prepared Chitosan/Hyaluronic acid-siRNA multilayer films through layer-by-layer self-assembly, in which siRNAs can be effectively loaded and protected. The construction process was characterized by FTIR, {sup 13}C NMR (CP/MAS), UV–vis spectroscopy, and atomic force microscopy (AFM). We presented the controlled-release performance of the films during incubation in 1 M NaCl solution for several days through UV–vis spectroscopy and polyacrylamide gel electrophoresis (PAGE). Additionally, we verified the stability and integrity of the siRNA loaded on multilayer films. Finally, the biological efficacy of the siRNA delivery system was evaluated via cells adhesion and gene silencing analyses in eGFP-HEK 293T cells. This new type of surface-mediated non-viral multilayer films may have considerable potential in the localized and controlled-release delivery of siRNA in mucosal tissues, and tissue engineering application.

  3. Multifunctional weak polyelectrolyte multilayers for membrane applications

    NARCIS (Netherlands)

    Ilyas, Shazia

    2017-01-01

    Thin polymer coatings in the form of polyelectrolyte multilayers (PEM) are an interesting class of coatings for the surface modification of materials to provide functional interfaces. These layers are prepared by layer-by-layer (LbL) assembly, an attractive technique with control over the thickness

  4. FunTAL: Reasonably Mixing a Functional Language with Assembly

    OpenAIRE

    Patterson, Daniel; Perconti, Jamie; Dimoulas, Christos; Ahmed, Amal

    2017-01-01

    We present FunTAL, the first multi-language system to formalize safe interoperability between a high-level functional language and low-level assembly code while supporting compositional reasoning about the mix. A central challenge in developing such a multi-language is bridging the gap between assembly, which is staged into jumps to continuations, and high-level code, where subterms return a result. We present a compositional stack-based typed assembly language that supports components, compr...

  5. Structural basis for ebolavirus matrix assembly and budding; protein plasticity allows multiple functions

    Science.gov (United States)

    Bornholdt, Zachary A.; Noda, Takeshi; Abelson, Dafna M.; Halfmann, Peter; Wood, Malcolm; Kawaoka, Yoshihiro; Saphire, Erica Ollmann

    2014-01-01

    Summary Proteins, particularly viral proteins, can be multifunctional, but the mechanism(s) behind this trait are not fully understood. Here, we illustrate through multiple crystal structures, biochemistry and cellular microscopy that VP40 rearranges into different structures, each with a distinct function required for the ebolavirus life cycle. A butterfly-shaped VP40 dimer trafficks to the cellular membrane. There, electrostatic interactions trigger rearrangement of the polypeptide into a linear hexamer. These hexamers construct a multi-layered, filamentous matrix structure that is critical for budding and resembles tomograms of authentic virions. A third structure of VP40, formed by a different rearrangement, is not involved in virus assembly, but instead uniquely binds RNA to regulate viral transcription inside infected cells. These results provide a functional model for ebolavirus matrix assembly and the other roles of VP40 in the virus life cycle, and demonstrate how a single, wild-type, unmodified polypeptide can assemble into different structures for different functions. PMID:23953110

  6. Functional self-assembled lipidic systems derived from renewable resources.

    Science.gov (United States)

    Silverman, Julian R; Samateh, Malick; John, George

    2016-01-01

    Self-assembled lipidic amphiphile systems can create a variety of multi-functional soft materials with value-added properties. When employing natural reagents and following biocatalytic syntheses, self-assembling monomers may be inherently designed for degradation, making them potential alternatives to conventional and persistent polymers. By using non-covalent forces, self-assembled amphiphiles can form nanotubes, fibers, and other stimuli responsive architectures prime for further applied research and incorporation into commercial products. By viewing these lipid derivatives under a lens of green principles, there is the hope that in developing a structure-function relationship and functional smart materials that research may remain safe, economic, and efficient.

  7. A multilayered plate theory with transverse shear and normal warping functions

    CERN Document Server

    Loredo, A

    2014-01-01

    A multilayered plate theory which takes into account transverse shear and normal stretching is presented. The theory is based on a seven-unknowns kinematic field with five warping functions. Four warping functions are related to the transverse shear behaviour, the fifth is related to the normal stretching. The warping functions are issued from exact three-dimensional solutions. They are related to the variations of transverse shear and normal stresses computed at specific points for a simply supported bending problem. Reddy, Cho-Parmerter and (a modified version of) Beakou-Touratier theories have been retained for comparisons. Extended versions of these theories, able to manage the normal stretching, are also considered. All these theories can be emulated by the kinematic field of the present model thanks to the adaptation of the five warping functions. Results of all these theories are confronted and compared to analytical solutions, for the bending of simply supported plates. Various plates are considered, ...

  8. Functional Molecular Junctions Derived from Double Self-Assembled Monolayers.

    Science.gov (United States)

    Seo, Sohyeon; Hwang, Eunhee; Cho, Yunhee; Lee, Junghyun; Lee, Hyoyoung

    2017-09-25

    Information processing using molecular junctions is becoming more important as devices are miniaturized to the nanoscale. Herein, we report functional molecular junctions derived from double self-assembled monolayers (SAMs) intercalated between soft graphene electrodes. Newly assembled molecular junctions are fabricated by placing a molecular SAM/(top) electrode on another molecular SAM/(bottom) electrode by using a contact-assembly technique. Double SAMs can provide tunneling conjugation across the van der Waals gap between the terminals of each monolayer and exhibit new electrical functions. Robust contact-assembled molecular junctions can act as platforms for the development of equivalent contact molecular junctions between top and bottom electrodes, which can be applied independently to different kinds of molecules to enhance either the structural complexity or the assembly properties of molecules. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Growth and characteristics of self-assembled MoS2/Mo-S-C nanoperiod multilayers for enhanced tribological performance

    Science.gov (United States)

    Xu, Jiao; He, TengFei; Chai, LiQiang; Qiao, Li; Wang, Peng; Liu, WeiMin

    2016-01-01

    Highly ordered MoS2/Mo-S-C nanoperiod multilayers are synthesized by a novel self-assembling mechanism in simultaneous sputtering of MoS2 and graphite targets. The sequential formation of MoS2-riched domain layers and Mo-S-C compositional mixed capping layers reveals no correspondence to the sample stage rotation but is caused by the low energy ion bombardment enhanced interdiffusion. The HRTEM observation shows that the phase segregation normal to the film surface is initiated from substrate-film interlayer with clear contrasts in the first few bi-layers, and then diffuses mutually in a quasiperiodic pattern between two altered sub-layers. Compared with sputtered MoS2 film, the bulk film of multilayers exhibit largely improved toughness under a normal load, and the preferential orientation of sputtered MoS2 in (002) basal planes is significantly enhanced, both of which render the film excellent loads-bearing capacity and lubricant properties. The nano-scratching tests performed on a nanoindentation system suggest that the nano-tribological performance of multilayers is directly determined by the altered structure and properties of neighboring sub-layers until stable tribofilms are formed. Meanwhile, the pin-on-disk tribotests in ambient air, low vacuum and high vacuum provide comparably low friction coefficient yet distinct wear lives in different atmospheres due to the partially restricted humid-sensitivity of sputtered MoS2 phase. PMID:27137707

  10. A surface-mediated siRNA delivery system developed with chitosan/hyaluronic acid-siRNA multilayer films through layer-by-layer self-assembly

    Science.gov (United States)

    Wu, Lijuan; Wu, Changlin; Liu, Guangwan; Liao, Nannan; Zhao, Fang; Yang, Xuxia; Qu, Hongyuan; Peng, Bo; Chen, Li; Yang, Guang

    2016-12-01

    siRNA delivery remains highly challenging because of its hydrophilic and anionic nature and its sensitivity to nuclease degradation. Effective siRNA loading and improved transfection efficiency into cells represents a key problem. In our study, we prepared Chitosan/Hyaluronic acid-siRNA multilayer films through layer-by-layer self-assembly, in which siRNAs can be effectively loaded and protected. The construction process was characterized by FTIR, 13C NMR (CP/MAS), UV-vis spectroscopy, and atomic force microscopy (AFM). We presented the controlled-release performance of the films during incubation in 1 M NaCl solution for several days through UV-vis spectroscopy and polyacrylamide gel electrophoresis (PAGE). Additionally, we verified the stability and integrity of the siRNA loaded on multilayer films. Finally, the biological efficacy of the siRNA delivery system was evaluated via cells adhesion and gene silencing analyses in eGFP-HEK 293T cells. This new type of surface-mediated non-viral multilayer films may have considerable potential in the localized and controlled-release delivery of siRNA in mucosal tissues, and tissue engineering application.

  11. Construction of a fucoidan/laminin functional multilayer to direction vascular cell fate and promotion hemocompatibility

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Changrong; Wang, Yan; Su, Hong; Yang, Ping; Huang, Nan [Key Laboratory of Advanced Materials Technology of Ministry of Education, Department of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China); Maitz, Manfred F. [Leibniz Institute of Polymer Research Dresden, Max Bergmann Center of Biomaterials Dresden, Dresden 01069 (Germany); Zhao, Anshan [Key Laboratory of Advanced Materials Technology of Ministry of Education, Department of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China)

    2016-07-01

    Surface biofunctional modification of cardiovascular stents is a versatile approach to reduce the adverse effects after implantation. In this work, a novel multifunctional coating was fabricated by coimmobilization of the sulfated polysaccharide of brown algae fucoidan and laminin to biomimic the vascular intimal conditions in order to support rapid endothelialization, prevent restenosis and improve hemocompatibility. The surface properties of the coating such as hydrophilicity, bonding density of biomolecules and stability were evaluated and optimized. According to the biocompatibility tests, the fucoidan/laminin multilayer coated surface displayed less platelet adhesion with favorable anticoagulant property. In addition, the fucoidan/laminin complex showed function to selectively regulate vascular cells growth behavior. The proliferation of endothelial cells (ECs) on the fucoidan/laminin biofunctional coating was significantly promoted. For the smooth muscle cells (SMCs), inhibitory effects on cell adhesion and proliferation were observed. In conclusion, the fucoidan/laminin biofunctional coating was successfully fabricated with desirable anticoagulant and endothelialization properties which show a promising application in the vascular devices such as vascular stents or grafts surface modification. - Highlights: • Construction of fucoidan/laminin functional multilayer to biomimic the basement membrane of vascular • The fucoidan/laminin complex demonstrates anti-coagulation property. • The fucoidan/laminin complex can selectively regulate EC and SMC growth behavior to prevent restenosis.

  12. Self-assembly of polyoxometalate-azure A multilayer films and their photocatalytic properties for degradation of methyl orange under visible light irradiation.

    Science.gov (United States)

    You, Yanglijun; Gao, Shuiying; Xu, Bo; Li, Guoliang; Cao, Rong

    2010-10-15

    Multilayer films (PW(12)-AA)(n) (PW(12)=PW(12)O(40)(3-), AA=azure A, n is the number of PW(12)-AA bilayers) were prepared on solid slides via a layer-by-layer (LbL) self-assembly method. The growth of the films was characterized by UV-vis spectra, FTIR spectra, and atomic force microscopy (AFM). The results show that the deposition process is linear and reproducible from layer to layer and the PW(12) is intact during the self-assembly process. AFM images indicate that the film surface is smooth and uniform. Moreover, the photocatalytic property of the films was investigated by the decomposition of methyl orange (MO) under visible light irradiation (lambda>420 nm). The multilayer films show photocatalytic activity for the degradation of MO under visible light irradiation using a xenon lamp and sunlight. The kinetics of the photodecomposition follows the first-order reaction. Copyright 2010 Elsevier Inc. All rights reserved.

  13. Aspects of Integrating Functional Electroceramic Material in Multilayer Thin Films for Image Sensing: Modeling and Experiment

    Science.gov (United States)

    Matin, M. A.; Oishi, K.; Katsuta, A.; Akai, D.; Sawada, K.; Ishida, M.

    2015-07-01

    Using combined experimental and simulation techniques, this study addresses the critical stress for peeling off crucial layer(s) in multilayered epitaxial functional thin films on n-Si(001) substrate. The thickness of platinum (Pt) and PZT thin films was varied from 22 nm to 142 nm and 90 nm to 450 nm, respectively. Residual stresses were measured by analyzing captured fringes using Newton's rings technique. Advanced finite element computation was next conducted to predict the evolution of residual stresses. Induced stresses in Pt thin film were found to be decreased with decreasing the thickness of film from 72 nm to 40 nm. In contrast, stresses are shown to be decreased with increasing the thickness of PZT film from 240 nm to 450 nm. The design of the pyroelectric multilayered sensors was thus optimized employing finite element (FE) simulation. Computed stresses were found to correlate well with that observed in experiments. FE simulations can thus be used as a tool to a priori predict the evolution of residual stresses, which may allow a fail-safe design before the fabrication of pyroelectric image sensors.

  14. Ingredient Functionality in Multilayered Dough-margarine Systems and the Resultant Pastry Products: A Review.

    Science.gov (United States)

    Ooms, Nand; Pareyt, Bram; Brijs, Kristof; Delcour, Jan A

    2016-10-02

    Pastry products are produced from heterogeneous multilayered dough systems. The main ingredients are flour, water, fat and sugar for puff pastry, and the same plus yeast for fermented pastry. Key aspects in pastry production are (i) building laminated dough containing alternating layers of dough and bakery fat and (ii) maintaining this multilayered structure during processing to allow for steam entrapment for proper dough lift during baking. Although most authors agree on the importance of gluten and fat for maintaining the integrity of the different layers, detailed studies on their specific function are lacking. The exact mechanism of steam entrapment during dough lift and the relative contribution of water set free from the fat phase during baking also remain unclear. This review brings together current knowledge on pastry products and the factors determining (intermediate) product quality. Its focus is on flour constituents, fat, water, and (where applicable) yeast during the different production stages of pastry products. Future research needs are addressed as the knowledge on biochemical and physical changes occurring in flour constituents and other ingredients during pastry production and their effect on product quality is currently inadequate.

  15. Self-assembled Li3V2(PO4)3/reduced graphene oxide multilayer composite prepared by sequential adsorption

    Science.gov (United States)

    Kim, Myeong-Seong; Bak, Seong-Min; Lee, Suk-Woo; Cho, Byung-Won; Roh, Kwang Chul; Kim, Kwang-Bum

    2017-11-01

    Herein, we report on Li3V2(PO4)3 (LVP)/reduced graphene oxide (rGO) multilayer composites prepared via a sequential adsorption method and subsequent heat treatment, and their use as cathodes for high-rate lithium-ion batteries. The sequential adsorption process includes adsorbing oppositely charged components of anionic inorganic species and cationic head of a surfactant adsorbed to graphite oxide sheets, which is a key step in the fabrication of the LVP/rGO multilayer composites. The multilayer structure has open channels between the highly conductive rGO layers while achieving a relatively high tap density, which could effectively improve the rate capability. Consequently, the LVP/rGO multilayer composites exhibit a high tap density (0.6 g cm-3) and good electrochemical properties. Specifically, in the voltage range of 3.0-4.3 V, the composite exhibits a specific capacity of 131 mAh g-1 at 0.1C, a good rate capabilities (88% capacity retention at 60C), and long cycling performance (97% capacity retention after 500 cycles at 10C). Moreover, in the extended voltage range of 3.0-4.8 V, it exhibits a high specific capacity of 185 mAh g-1 at 0.2C, a good rate capability (66% capacity retention at 30C), and stable cycling performance (96% capacity retention after 500 cycles at 10C).

  16. Nanoarchitectonics of biomolecular assemblies for functional applications

    Science.gov (United States)

    Avinash, M. B.; Govindaraju, T.

    2014-10-01

    The stringent processes of natural selection and evolution have enabled extraordinary structure-function properties of biomolecules. Specifically, the archetypal designs of biomolecules, such as amino acids, nucleobases, carbohydrates and lipids amongst others, encode unparalleled information, selectivity and specificity. The integration of biomolecules either with functional molecules or with an embodied functionality ensures an eclectic approach for novel and advanced nanotechnological applications ranging from electronics to biomedicine, besides bright prospects in systems chemistry and synthetic biology. Given this intriguing scenario, our feature article intends to shed light on the emerging field of functional biomolecular engineering.

  17. Microstructural and component evolution of self-assembled nanoperiod multilayered carbon-copper films with deposition pressure

    Science.gov (United States)

    Wang, Weiqi; Ji, Li; Li, Hongxuan; Zhao, Yiman; Zhou, Huidi; Chen, Jianmin

    2017-04-01

    Here, we report a facile synthesis method for the fabrication of various nanoperiod multilayers in carbon-copper films only by conveniently changing the deposition pressure from the reactive magnetron sputter process. To obtain the nano-multilayered structure with different number of layers, only one single sputtering target of copper is used at gas pressure varied from 0.4 Pa to 1.2 Pa by flowing gas mixture of argon and methane, while 600W DC input power is applied to a copper target. The influence of deposition pressure on the microstructure and constitution of the films are investigated by X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM). The results show that carbon-rich layers and copper-rich layers are alternately arranged to self-organize the multilayered structure in the carbon-copper films, both of the carbon-rich layer and copper-rich layer constitute a period. The amount of layers in the multilayered structure is found to decrease with the deposition pressure, the film deposited with 0.4 Pa has the maximum layers and the highest copper content compared with the other deposition pressure. Effects of the growth condition on the growth rate, the number of the layers and the energy of plasmas during deposition process are discussed. Based on the (a) influence of the effect of carbon absorbed on the copper target leading to target poisoning, (b) influence of deposition pressure on the energy of etching ions and (c) the energetic ions bombardment enhanced inter diffusion of deposition ions, the mechanism of self-organized formation of nano-multilayer in the carbon-copper films with various number of layer is proposed.

  18. Using human artificial chromosomes to study centromere assembly and function.

    Science.gov (United States)

    Molina, Oscar; Kouprina, Natalay; Masumoto, Hiroshi; Larionov, Vladimir; Earnshaw, William C

    2017-10-01

    Centromeres are the site of assembly of the kinetochore, which directs chromosome segregation during cell division. Active centromeres are characterized by the presence of nucleosomes containing CENP-A and a specific chromatin environment that resembles that of active genes. Recent work using human artificial chromosomes (HAC) sheds light on the fine balance of different histone post-translational modifications and transcription that exists at centromeres for kinetochore assembly and maintenance. Here, we review the use of HAC technology to understand centromere assembly and function. We put particular emphasis on studies using the alphoidtetO HAC, whose centromere can be specifically modified for epigenetic engineering studies.

  19. Determination of crystallization as a function of Mo layer thickness in Mo/Si multilayers

    DEFF Research Database (Denmark)

    Abdali, Salim; Gerward, Leif; Yakshin, A.E.

    2002-01-01

    information on the crystalline phases, average size and crystallite formation. Comparison of these parameters for the samples examined provided novel results, especially regarding the in-plane and in-depth average sizes of the crystallites. The most important result is that crystallization takes place already......Mo/Si multilayer samples with different Mo layer thickness were deposited by electron beam evaporation, while Kr+ ions (300 eV) were used for polishing the Si layers. Crystallization as a function of the Mo layer thickness deposited was investigated by grazing incidence X-ray diffraction, giving...... when a 1 nm thick Mo layer has been deposited. Moreover, the average in-plane size of the crystallites was found to be independent of the layer thickness, while the average in-depth size corresponded to the thickness of the Mo layer. Depositions consist of polished Si layers were found to give a larger...

  20. An Intelligent Approach to Educational Data: Performance Comparison of the Multilayer Perceptron and the Radial Basis Function Artificial Neural Networks

    Science.gov (United States)

    Kayri, Murat

    2015-01-01

    The objective of this study is twofold: (1) to investigate the factors that affect the success of university students by employing two artificial neural network methods (i.e., multilayer perceptron [MLP] and radial basis function [RBF]); and (2) to compare the effects of these methods on educational data in terms of predictive ability. The…

  1. Light source distribution and scattering phase function influence light transport in diffuse multi-layered media

    Science.gov (United States)

    Vaudelle, Fabrice; L'Huillier, Jean-Pierre; Askoura, Mohamed Lamine

    2017-06-01

    Red and near-Infrared light is often used as a useful diagnostic and imaging probe for highly scattering media such as biological tissues, fruits and vegetables. Part of diffusively reflected light gives interesting information related to the tissue subsurface, whereas light recorded at further distances may probe deeper into the interrogated turbid tissues. However, modelling diffusive events occurring at short source-detector distances requires to consider both the distribution of the light sources and the scattering phase functions. In this report, a modified Monte Carlo model is used to compute light transport in curved and multi-layered tissue samples which are covered with a thin and highly diffusing tissue layer. Different light source distributions (ballistic, diffuse or Lambertian) are tested with specific scattering phase functions (modified or not modified Henyey-Greenstein, Gegenbauer and Mie) to compute the amount of backscattered and transmitted light in apple and human skin structures. Comparisons between simulation results and experiments carried out with a multispectral imaging setup confirm the soundness of the theoretical strategy and may explain the role of the skin on light transport in whole and half-cut apples. Other computational results show that a Lambertian source distribution combined with a Henyey-Greenstein phase function provides a higher photon density in the stratum corneum than in the upper dermis layer. Furthermore, it is also shown that the scattering phase function may affect the shape and the magnitude of the Bidirectional Reflectance Distribution (BRDF) exhibited at the skin surface.

  2. Self-assembly of polyoxometalate-thionine multilayer films on magnetic microspheres as photocatalyst for methyl orange degradation under visible light irradiation.

    Science.gov (United States)

    Li, Hongfang; Gao, Shuiying; Cao, Minna; Cao, Rong

    2013-03-15

    (PW(12)-TH)(n) multilayer films (PW(12)=PW(12)O(40)(3-), TH=thionine) were deposited successfully on core-shell structured Fe(3)O(4)@SiO(2) magnetic microspheres through layer-by-layer (LbL) self-assembly method. The physical and photocatalytic properties of such magnetic microspheres coated with (PW(12)-TH)(n) films have been characterized by SEM, FTIR, and UV-vis spectra. The microspheres exhibit better photocatalytic activity toward the degradation of methyl orange (MO) under visible light irradiation than the quartz slides support. In addition, the use of magnetic support guarantees facile, clean, fast, and efficient separation of the photocatalyst after the degradation of MO. Such catalysts can be reused several times and display good reproducibility by magnetic separation. Copyright © 2012 Elsevier Inc. All rights reserved.

  3. Pigment-dependence of LHC assembly, structure, and function

    Energy Technology Data Exchange (ETDEWEB)

    Plumley, F.G.; Weston, B.; Stafford, R.A. (Univ. of Alaska, Fairbanks (United States)); Schmidt, G.W. (Univ. of Georgia, Athens (United States))

    1993-05-01

    The role of pigments in the assembly and function of light-harvesting complexes in incompletely understood. A Chl b- and neoxanthin-deficient Chlamydomonas mutant (GE2.27) was isolated. Surprisingly, the rate of PSII-dependent O[sub 2] evolution at light-limiting conditions in mutant GE2.27 is reduced to the same extent as in another Chlamydomonas mutant completely devoid of LHC apoproteins. Thus, the partially assembled LHCs of GE2,27 do not functionally interact with PSII. Protease treatments of thylakoids reveal that the LHC proteins of GE2.27 are both hypersensitive and digested at unique sites indicating that the partially assembled LHC proteins of GE2.27 have an altered topological organization. Because thylakoid proteins from both PSI- and PSII-deficient mutants do not exhibit alterations in their susceptibility to exogenous proteases, the topological changes observed in GE2.27 LHC proteins are not a result of their propensity to associate with PSI or their apparent inability to functionally associate with PSII.Partially assembled LHCs, containing only Chl a, lutein, loroxanthin and violaxanthin were purified from GE2.27 thylakoids. the data indicate the altered topology as assessed by protease digestion assays are not simply due to the absence of Chl b and/or neoxanthin as proteolytic shields. We suggest that assembly of Chl b is required for proper folding of LHC proteins in thylakoid membranes and the conformational changes facilitate assembly and, therefore, accumulation of neoxanthin. Finally, neither Chl b nor neoxanthin is required for LHC association with PSI but one or more of these pigments is necessary to promote LHC association with PSII reaction centers. This is the first demonstration of pigment-dependent modulation of thylakoid protein conformation and function.

  4. A robust formulation of SAW Green's functions for arbitrarily thick multilayers at high frequencies.

    Science.gov (United States)

    Tan, Eng Leong

    2002-07-01

    This paper presents a robust formulation of SAW Green's functions for arbitrarily thick multilayers at high frequencies. The formulation is an alternative to that based on the transfer matrix method, which suffers from numerical instabilities when the frequency and/or thickness parameters become large. This numerical difficulty can be attributed to the mixture of exponentially growing and decaying terms during the transfer matrix calculations. To be more instructive, the numerical instability is delineated in terms of upward-bounded and downward-bounded waves within each layer. In accordance with such boundedness association, a recursive scheme not involving any growing terms is developed based on the scattering matrices to eliminate the instability. The resulting reflection matrix method is extremely concise and preserves the simplicity and convenience of the transfer matrix method. Using the reflection matrices, the generalized Green's functions that relate the particle velocity and the rate of electric potential change to the surface stress and charge are formulated succinctly. These Green's functions are useful for having incorporated the electrical properties of the vacuum above the surface. Numerical computations are exemplified to demonstrate the instabilities of the transfer matrix method and to justify the robustness of the reflection matrix formula.

  5. Functional materials derived from block copolymer self-assembly

    DEFF Research Database (Denmark)

    Li, Tao

    The main objective of this project is to explore block copolymer self-assembly for generating functional materials with well-defined morphology on sub-20 nanometer length scale, which can be utilized in many important applications such as solar cells and nanolithography. One of the specific targe...

  6. Tuning of metal work functions with self-assembled monolayers

    NARCIS (Netherlands)

    de Boer, B; Hadipour, A; Mandoc, MM; van Woudenbergh, T; Blom, PWM

    2005-01-01

    Work functions of gold and silver are varied by over 1.4 and 1.7 eV, respectively, by using self-assembled monolayers. Using these modified electrodes, the hole current in a poly(2-methoxy-5-(2'-ethylhexyloxy)- 1,4-phenylene vinylene) light-emitting diode is tuned by more than six orders of

  7. Investigating organic multilayers by spectroscopic ellipsometry: specific and non-specific interactions of polyhistidine with NTA self-assembled monolayers

    Directory of Open Access Journals (Sweden)

    Ilaria Solano

    2016-04-01

    Full Text Available Background: A versatile strategy for protein–surface coupling in biochips exploits the affinity for polyhistidine of the nitrilotriacetic acid (NTA group loaded with Ni(II. Methods based on optical reflectivity measurements such as spectroscopic ellipsometry (SE allow for label-free, non-invasive monitoring of molecule adsorption/desorption at surfaces.Results: This paper describes a SE study about the interaction of hexahistidine (His6 on gold substrates functionalized with a thiolate self-assembled monolayer bearing the NTA end group. By systematically applying the difference spectra method, which emphasizes the small changes of the ellipsometry spectral response upon the nanoscale thickening/thinning of the molecular film, we characterized different steps of the process such as the NTA-functionalization of Au, the adsorption of the His6 layer and its eventual displacement after reaction with competitive ligands. The films were investigated in liquid, and ex situ in ambient air. The SE investigation has been complemented by AFM measurements based on nanolithography methods (nanografting mode.Conclusion: Our approach to the SE data, exploiting the full spectroscopic potential of the method and basic optical models, was able to provide a picture of the variation of the film thickness along the process. The combination of δΔi+1,i(λ, δΨi+1,i(λ (layer-addition mode and δΔ†i',i+1(λ, δΨ†i',i+1(λ (layer-removal mode difference spectra allowed us to clearly disentangle the adsorption of His6 on the Ni-free NTA layer, due to non specific interactions, from the formation of a neatly thicker His6 film induced by the Ni(II-loading of the NTA SAM.

  8. Ionic self-assembly for functional hierarchical nanostructured materials.

    Science.gov (United States)

    Faul, Charl F J

    2014-12-16

    CONSPECTUS: The challenge of constructing soft functional materials over multiple length scales can be addressed by a number of different routes based on the principles of self-assembly, with the judicious use of various noncovalent interactions providing the tools to control such self-assembly processes. It is within the context of this challenge that we have extensively explored the use of an important approach for materials construction over the past decade: exploiting electrostatic interactions in our ionic self-assembly (ISA) method. In this approach, cooperative assembly of carefully chosen charged surfactants and oppositely charged building blocks (or tectons) provides a facile noncovalent route for the rational design and production of functional nanostructured materials. Generally, our research efforts have developed with an initial focus on establishing rules for the construction of novel noncovalent liquid-crystalline (LC) materials. We found that the use of double-tailed surfactant species (especially branched double-tailed surfactants) led to the facile formation of thermotropic (and, in certain cases, lyotropic) phases, as demonstrated by extensive temperature-dependent X-ray and light microscopy investigations. From this core area of activity, research expanded to cover issues beyond simple construction of anisotropic materials, turning to the challenge of inclusion and exploitation of switchable functionality. The use of photoactive azobenzene-containing ISA materials afforded opportunities to exploit both photo-orientation and surface relief grating formation. The preparation of these anisotropic LC materials was of interest, as the aim was the facile production of disposable and low-cost optical components for display applications and data storage. However, the prohibitive cost of the photo-orientation processes hampered further exploitation of these materials. We also expanded our activities to explore ISA of biologically relevant tectons

  9. Multilayer core-shell structured composite paper electrode consisting of copper, cuprous oxide and graphite assembled on cellulose fibers for asymmetric supercapacitors

    Science.gov (United States)

    Wan, Caichao; Jiao, Yue; Li, Jian

    2017-09-01

    An easily-operated and inexpensive strategy (pencil-drawing-electrodeposition-electro-oxidation) is proposed to synthesize a novel class of multilayer core-shell structured composite paper electrode, which consists of copper, cuprous oxide and graphite assembled on cellulose fibers. This interesting electrode structure plays a pivotal role in providing more active sites for electrochemical reactions, facilitating ion and electron transport and shorting their diffusion pathways. This electrode demonstrates excellent electrochemical properties with a high specific capacitance of 601 F g-1 at 2 A g-1 and retains 83% of this capacitance when operated at an ultrahigh current density of 100 A g-1. In addition, a high energy density of 13.4 W h kg-1 at the power density of 0.40 kW kg-1 and a favorable cycling stability (95.3%, 8000 cycles) were achieved for this electrode. When this electrode was assembled into an asymmetric supercapacitor with carbon paper as negative electrode, the device displays remarkable electrochemical performances with a large areal capacitances (122 mF cm-2 at 1 mA cm-2), high areal energy density (10.8 μW h cm-2 at 402.5 μW cm-2) and outstanding cycling stability (91.5%, 5000 cycles). These results unveil the potential of this composite electrode as a high-performance electrode material for supercapacitors.

  10. Electronic functionalization of organic semiconductors with self-assembled monolayers

    Science.gov (United States)

    Podzorov, Vitaly

    2008-03-01

    Self-assembled monolayers (SAM) are widely used in a variety of emerging applications for surface modification of metals and oxides. Here, we demonstrate a new type of molecular self-assembly: the growth of organosilane SAMs at the surface of organic semiconductors. Remarkably, SAM growth results in a pronounced increase of surface conductivity of organic materials, which can be very large for SAMs with a strong electron withdrawing ability. For example, the conductivity induced by perfluorinated alkyl silanes in organic molecular crystals approaches 10̂-5 S per square, two orders of magnitude greater than the maximum conductivity typically achieved in organic field-effect transistors (OFETs). The observed large electronic effect opens new opportunities for nanoscale surface functionalization of organic semiconductors with molecular self-assembly. In particular, SAM-induced conductivity exhibits sensitivity to different molecular species present in the environment, which makes this system very attractive for chemical sensing applications [1]. [1]. M. F. Calhoun, J. Sanchez, D. Olaya, M. E. Gershenson and V. Podzorov, ``Electronic functionalization of the surface of organic semiconductors with self-assembled monolayers'', Nature Materials, Nov. 18, (2007).

  11. Chromosomal-Level Assembly of the Asian Seabass Genome Using Long Sequence Reads and Multi-layered Scaffolding.

    Directory of Open Access Journals (Sweden)

    Shubha Vij

    2016-04-01

    Full Text Available We report here the ~670 Mb genome assembly of the Asian seabass (Lates calcarifer, a tropical marine teleost. We used long-read sequencing augmented by transcriptomics, optical and genetic mapping along with shared synteny from closely related fish species to derive a chromosome-level assembly with a contig N50 size over 1 Mb and scaffold N50 size over 25 Mb that span ~90% of the genome. The population structure of L. calcarifer species complex was analyzed by re-sequencing 61 individuals representing various regions across the species' native range. SNP analyses identified high levels of genetic diversity and confirmed earlier indications of a population stratification comprising three clades with signs of admixture apparent in the South-East Asian population. The quality of the Asian seabass genome assembly far exceeds that of any other fish species, and will serve as a new standard for fish genomics.

  12. Study on spontaneous emission in complex multilayered plasmonic system via surface integral equation approach with layered medium Green's function.

    Science.gov (United States)

    Chen, Yongpin P; Sha, Wei E I; Choy, Wallace C H; Jiang, Lijun; Chew, Weng Cho

    2012-08-27

    A rigorous surface integral equation approach is proposed to study the spontaneous emission of a quantum emitter embedded in a multilayered plasmonic structure with the presence of arbitrarily shaped metallic nanoscatterers. With the aid of the Fermi's golden rule, the spontaneous emission of the emitter can be calculated from the local density of states, which can be further expressed by the imaginary part of the dyadic Green's function of the whole electromagnetic system. To obtain this Green's function numerically, a surface integral equation is established taking into account the scattering from the metallic nanoscatterers. Particularly, the modeling of the planar multilayered structure is simplified by applying the layered medium Green's function to reduce the computational domain and hence the memory requirement. Regarding the evaluation of Sommerfeld integrals in the layered medium Green's function, the discrete complex image method is adopted to accelerate the evaluation process. This work offers an accurate and efficient simulation tool for analyzing complex multilayered plasmonic system, which is commonly encountered in the design of optical elements and devices.

  13. The Functionally-Assembled Terrestrial Ecosystem Simulator Version 1

    Energy Technology Data Exchange (ETDEWEB)

    2017-06-02

    The Functionally-Assembled Terrestrial Ecosystem Simulator (FATES) is a vegetation model for use in Earth system models (ESMs). The model includes a size- and age-structured representation of tree dynamics, competition between functionally diverse plant functional types, and the biophysics underpinning plant growth, competition, mortality, as well as the carbon, water, and energy exchange with the atmosphere. The FATES model is designed as a modular vegetation model that can be integrated within a host land model for inclusion in ESMs. The model is designed for use in global change studies to understand and project the responses and feedbacks between terrestrial ecosystems and the Earth system under changing climate and other forcings.

  14. Layer-by-Layer Self-Assembled Graphene Multilayers as Pt-Free Alternative Counter Electrodes in Dye-Sensitized Solar Cells.

    Science.gov (United States)

    Rani, Adila; Chung, Kyungwha; Kwon, Jeong; Kim, Sung June; Jang, Yoon Hee; Jang, Yu Jin; Quan, Li Na; Yoon, Minji; Park, Jong Hyeok; Kim, Dong Ha

    2016-05-11

    Low cost, charged, and large scale graphene multilayers fabricated from nitrogen-doped reduced graphene oxide N-rGO(+), nitrogen and sulfur codoped reduced graphene oxide NS-rGO(+), and undoped reduced graphene oxide rGO(-) were applied as alternative counter electrodes in dye-sensitized solar cells (DSSCs). The neat rGO-based counter electrodes were developed via two types of layer-by-layer (LBL) self-assembly (SA) methods: spin coating and spray coating methods. In the spin coating method, two sets of multilayer films were fabricated on poly(diallyldimethylammonium chloride) (PDDA)-coated fluorine-doped tin oxide (FTO) substrates using GO(-) combined with N-GO(+) followed by annealing and denoted as [rGO(-)/N-rGO(+)]n or with NS-GO(+) and denoted as [rGO(-)/NS-rGO(+)]n for counter electrodes in DSSCs. The DSSCs employing new types of counter electrodes exhibited ∼7.0% and ∼6.2% power conversion efficiency (PCE) based on ten bilayers of [rGO(-)/N-rGO(+)]10 and [rGO(-)/NS-rGO(+)]10, respectively. The DSSCs equipped with a blend of one bilayer of [rGO(-):N-rGO(+)] and [rGO(-):NS-rGO(+)] on PDDA-coated FTO substrates were prepared from a spray coating and showed ∼6.4% and ∼5.6% PCE, respectively. Thus, it was demonstrated that a combination of undoped, nitrogen-doped, and nitrogen and sulfur codoped reduced graphene oxides can be considered as potentially powerful Pt-free electrocatalysts and alternative electrodes in conventional photovoltaic devices.

  15. Functional assembly of protein fragments induced by spatial confinement.

    Directory of Open Access Journals (Sweden)

    Yongsheng Yu

    Full Text Available Natural proteins are often confined within their local microenvironments, such as three-dimensional confinement in organelles or two-dimensional confinement in lipid rafts on cytoplasmic membrane. Spatial confinement restricts proteins' entropic freedom, forces their lateral interaction, and induces new properties that the same proteins lack at the soluble state. So far, the phenomenon of environment-induced protein functional alteration still lacks a full illustration. We demonstrate here that engineered protein fragments, although being non-functional in solution, can be re-assembled within the nanometer space to give the full activity of the whole protein. Specific interaction between hexahistidine-tag (His-tag and NiO surface immobilizes protein fragments on NiO nanoparticles to form a self-assembled protein "corona" on the particles inside the nanopores of mesoporous silica. Site-specific assembly forces a shoulder-by-shoulder orientation and promotes fragment-fragment interaction; this interaction together with spatial confinement of the mesopores results in functional re-assembly of the protein half fragments. To our surprise, a single half fragment of luciferase (non-catalytic in solution exhibited luciferase activity when immobilized on NiO in the mesopores, in the absence of the complimentary half. This shows for the first time that spatial confinement can induce the folding of a half fragment, reconstitute the enzyme active site, and re-gain the catalytic capability of the whole protein. Our work thereby highlights the under-documented notion that aside from the chemical composition such as primary sequence, physical environment of a protein also determines its function.

  16. Axial postbuckling analysis of multilayer functionally graded composite nanoplates reinforced with GPLs based on nonlocal strain gradient theory

    Science.gov (United States)

    Sahmani, S.; Aghdam, M. M.

    2017-11-01

    In this paper, a new size-dependent inhomogeneous plate model is constructed to analyze the nonlinear buckling and postbuckling characteristics of multilayer functionally graded composite nanoplates reinforced with graphene platelet (GPL) nanofillers under axial compressive load. To this purpose, the nonlocal strain gradient theory of elasticity is implemented into a refined hyperbolic shear deformation plate theory. The mechanical properties of multilayer graphene platelet-reinforced composite (GPLRC) nanoplates are evaluated based upon the Halpin-Tsai micromechanical scheme. The weight fraction of randomly dispersed GPLs remain constant in each individual layer, which results in U-GPLRC nanoplate, or changes layerwise in accordance with three different functionally graded patterns, which make X-GPLRC, O-GPLRC and A-GPLRC nanoplates. Via a two-stepped perturbation technique, explicit analytical expressions for nonlocal strain gradient stability paths are established for layerwise functionally graded GPLRC nanoplates. It is demonstrated that both the nonlocal and strain gradient size dependencies are more significant for multilayer GPLRC nanoplates filling by GPL nanofillers with higher length-to-thickness and width-to-thickness ratios.

  17. Layer-by-layer assembly of functionalized reduced graphene oxide for direct electrochemistry and glucose detection.

    Science.gov (United States)

    Mascagni, Daniela Branco Tavares; Miyazaki, Celina Massumi; da Cruz, Nilson Cristino; de Moraes, Marli Leite; Riul, Antonio; Ferreira, Marystela

    2016-11-01

    We report an electrochemical glucose biosensor made with layer-by-layer (LbL) films of functionalized reduced graphene oxide (rGO) and glucose oxidase (GOx). The LbL assembly using positively and negatively charged rGO multilayers represents a simple approach to develop enzymatic biosensors. The electron transport properties of graphene were combined with the specificity provided by the enzyme. rGO was obtained and functionalized using chemical methods, being positively charged with poly(diallyldimethylammonium chloride) to form GPDDA, and negatively charged with poly(styrene sulfonate) to form GPSS. Stable aqueous dispersions of GPDDA and GPSS are easily obtained, enabling the growth of LbL films on various solid supports. The use of graphene in the immobilization of GOx promoted Direct Electron Transfer, which was evaluated by Cyclic Voltammetry. Amperometric measurements indicated a detection limit of 13.4μmol·L(-1) and sensitivity of 2.47μA·cm(-2)·mmol(-1)·L for glucose with the (GPDDA/GPSS)1/(GPDDA/GOx)2 architecture, whose thickness was 19.80±0.28nm, as determined by Surface Plasmon Resonance (SPR). The sensor may be useful for clinical analysis since glucose could be detected even in the presence of typical interfering agents and in real samples of a lactose-free milk and an electrolyte solution to prevent dehydration. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Integrating community assembly and biodiversity to better understand ecosystem function: the Community Assembly and the Functioning of Ecosystems (CAFE) approach.

    Science.gov (United States)

    Bannar-Martin, Katherine H; Kremer, Colin T; Ernest, S K Morgan; Leibold, Mathew A; Auge, Harald; Chase, Jonathan; Declerck, Steven A J; Eisenhauer, Nico; Harpole, Stanley; Hillebrand, Helmut; Isbell, Forest; Koffel, Thomas; Larsen, Stefano; Narwani, Anita; Petermann, Jana S; Roscher, Christiane; Cabral, Juliano Sarmento; Supp, Sarah R

    2018-02-01

    The research of a generation of ecologists was catalysed by the recognition that the number and identity of species in communities influences the functioning of ecosystems. The relationship between biodiversity and ecosystem functioning (BEF) is most often examined by controlling species richness and randomising community composition. In natural systems, biodiversity changes are often part of a bigger community assembly dynamic. Therefore, focusing on community assembly and the functioning of ecosystems (CAFE), by integrating both species richness and composition through species gains, losses and changes in abundance, will better reveal how community changes affect ecosystem function. We synthesise the BEF and CAFE perspectives using an ecological application of the Price equation, which partitions the contributions of richness and composition to function. Using empirical examples, we show how the CAFE approach reveals important contributions of composition to function. These examples show how changes in species richness and composition driven by environmental perturbations can work in concert or antagonistically to influence ecosystem function. Considering how communities change in an integrative fashion, rather than focusing on one axis of community structure at a time, will improve our ability to anticipate and predict changes in ecosystem function. © 2017 The Authors. Ecology Letters published by CNRS and John Wiley & Sons Ltd.

  19. Synthesis of Nanostructured Nanoclay-Zirconia Multilayers: a Feasibility Study

    Directory of Open Access Journals (Sweden)

    Hao Chen

    2008-01-01

    Full Text Available This paper reports the first effort to synthesize a new class of inorganic nanostructured materials consisting of alternating ultrathin layers of nanoclays and oxide ceramics. A novel solution-based layer-by-layer (LBL deposition technique was developed to prepare multilayers of hydrated Zr cations and nanoclays. This LBL deposition technique is devised by integrating an electrostatic-mediated dip coating method for making nanoclay-polymer multilayers with a successive ionic layer adsorption and reaction method for making ultrathin oxide films. Nanostructured clay-zirconia multilayer composites formed through subsequent annealing. Characterization by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction confirmed that these films are uniform and crack-free, consist of no detectable impurities, and possess nanoscale-layered structure. The incorporation of nanoclays facilitates the electrostatic-mediated assembling of multilayers, enhances the structural integrity, and provides a generic framework to construct functionally graded materials. Potential applications are envisaged.

  20. Photochemical properties and interfacial fluorescence sensing for homocysteine of triptycene orthoquinone layer-by-layer-assembled multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Xiangying, E-mail: sunxy@hqu.edu.cn; Liu, Bin; Wu, Qiong; Li, Fang

    2014-07-01

    In the present work, the properties of triptycene orthoquinone derivatives were studied. As a kind of good electron-transfer platform, triptycene derivatives with different electron donors or electron acceptors behave distinctively with their luminescent properties. The intensity ratio of fluorescence peaks can be controlled by the number of methoxy groups (electron donor) and orthoquinone groups (electron acceptor) simultaneously. We have assembled 6,7,12,13-4-methoxyl-2, 3-2-orthoquinone triptycene onto self-assembled monolayers (SAMs) to create a probe for detecting biological thiols. The SAMs exhibited higher selectivity toward homocysteine than to other thiol-containing compounds with a fast response and a stable signal over a wide liner range from 2.0 μmol/L to 1.0 mmol/L with the detection limit of 0.52 μmol/L. - Highlights: • A dual fluorescence probe for biological thiols was reported. • This probe is based on triptycene orthoquinones self-assembled mutilayers. • The sensor exhibits higher selectivity toward homocysteine than other thiol compounds.

  1. Molecular Motions in Functional Self-Assembled Nanostructures

    Directory of Open Access Journals (Sweden)

    Jean-Marc Saiter

    2013-01-01

    Full Text Available The construction of “smart” materials able to perform specific functions at the molecular scale through the application of various stimuli is highly attractive but still challenging. The most recent applications indicate that the outstanding flexibility of self-assembled architectures can be employed as a powerful tool for the development of innovative molecular devices, functional surfaces and smart nanomaterials. Structural flexibility of these materials is known to be conferred by weak intermolecular forces involved in self-assembly strategies. However, some fundamental mechanisms responsible for conformational lability remain unexplored. Furthermore, the role played by stronger bonds, such as coordination, ionic and covalent bonding, is sometimes neglected while they can be employed readily to produce mechanically robust but also chemically reversible structures. In this review, recent applications of structural flexibility and molecular motions in self-assembled nanostructures are discussed. Special focus is given to advanced materials exhibiting significant performance changes after an external stimulus is applied, such as light exposure, pH variation, heat treatment or electromagnetic field. The crucial role played by strong intra- and weak intermolecular interactions on structural lability and responsiveness is highlighted.

  2. Assembly and Function of the Bacillus anthracis S-Layer.

    Science.gov (United States)

    Missiakas, Dominique; Schneewind, Olaf

    2017-09-08

    Bacillus anthracis, the anthrax agent, is a member of the Bacillus cereus sensu lato group, which includes invasive pathogens of mammals or insects as well as nonpathogenic environmental strains. The genes for anthrax pathogenesis are located on two large virulence plasmids. Similar virulence plasmids have been acquired by other B. cereus strains and enable the pathogenesis of anthrax-like diseases. Among the virulence factors of B. anthracis is the S-layer-associated protein BslA, which endows bacilli with invasive attributes for mammalian hosts. BslA surface display and function are dependent on the bacterial S-layer, whose constituents assemble by binding to the secondary cell wall polysaccharide (SCWP) via S-layer homology (SLH) domains. B. anthracis and other pathogenic B. cereus isolates harbor genes for the secretion of S-layer proteins, for S-layer assembly, and for synthesis of the SCWP. We review here recent insights into the assembly and function of the S-layer and the SCWP.

  3. Desktop aligner for fabrication of multilayer microfluidic devices

    Science.gov (United States)

    Li, Xiang; Yu, Zeta Tak For; Geraldo, Dalton; Weng, Shinuo; Alve, Nitesh; Dun, Wu; Kini, Akshay; Patel, Karan; Shu, Roberto; Zhang, Feng; Li, Gang; Jin, Qinghui; Fu, Jianping

    2015-07-01

    Multilayer assembly is a commonly used technique to construct multilayer polydimethylsiloxane (PDMS)-based microfluidic devices with complex 3D architecture and connectivity for large-scale microfluidic integration. Accurate alignment of structure features on different PDMS layers before their permanent bonding is critical in determining the yield and quality of assembled multilayer microfluidic devices. Herein, we report a custom-built desktop aligner capable of both local and global alignments of PDMS layers covering a broad size range. Two digital microscopes were incorporated into the aligner design to allow accurate global alignment of PDMS structures up to 4 in. in diameter. Both local and global alignment accuracies of the desktop aligner were determined to be about 20 μm cm-1. To demonstrate its utility for fabrication of integrated multilayer PDMS microfluidic devices, we applied the desktop aligner to achieve accurate alignment of different functional PDMS layers in multilayer microfluidics including an organs-on-chips device as well as a microfluidic device integrated with vertical passages connecting channels located in different PDMS layers. Owing to its convenient operation, high accuracy, low cost, light weight, and portability, the desktop aligner is useful for microfluidic researchers to achieve rapid and accurate alignment for generating multilayer PDMS microfluidic devices.

  4. A Cost-Effective Culture System for the In Vitro Assembly, Maturation, and Stimulation of Advanced Multilayered Multiculture Tubular Tissue Models.

    Science.gov (United States)

    Loy, Caroline; Pezzoli, Daniele; Candiani, Gabriele; Mantovani, Diego

    2018-01-01

    The development of tubular engineered tissues is a challenging research area aiming to provide tissue substitutes but also in vitro models to test drugs, medical devices, and even to study physiological and pathological processes. In this work, the design, fabrication, and validation of an original cost-effective tubular multilayered-tissue culture system (TMCS) are reported. By exploiting cellularized collagen gel as scaffold, a simple moulding technique and an endothelialization step on a rotating system, TMCS allowed to easily prepare in 48 h, trilayered arterial wall models with finely organized cellular composition and to mature them for 2 weeks without any need of manipulation. Multilayered constructs incorporating different combinations of vascular cells are compared in terms of cell organization and viscoelastic mechanical properties demonstrating that cells always progressively aligned parallel to the longitudinal direction. Also, fibroblast compacted less the collagen matrix and appeared crucial in term of maturation/deposition of elastic extracellular matrix. Preliminary studies under shear stress stimulation upon connection with a flow bioreactor are successfully conducted without damaging the endothelial monolayer. Altogether, the TMCS herein developed, thanks to its versatility and multiple functionalities, holds great promise for vascular tissue engineering applications, but also for other tubular tissues such as trachea or oesophagus. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Paradigm shift from self-assembly to commanded assembly of functional materials: recent examples in porphyrin/fullerene supramolecular systems

    Science.gov (United States)

    Li, Mao; Ishihara, Shinsuke; Ji, Qingmin; Akada, Misaho; Hill, Jonathan P.; Ariga, Katsuhiko

    2012-10-01

    Current nanotechnology based on top-down nanofabrication may encounter a variety of drawbacks in the near future so that development of alternative methods, including the so-called bottom-up approach, has attracted considerable attention. However, the bottom-up strategy, which often relies on spontaneous self-assembly, might be inefficient in the development of the requisite functional materials and systems. Therefore, assembly processes controlled by external stimuli might be a plausible strategy for the development of bottom-up nanotechnology. In this review, we demonstrate a paradigm shift from self-assembly to commanded assembly by describing several examples of assemblies of typical functional molecules, i.e. porphyrins and fullerenes. In the first section, we describe recent progress in the design and study of self-assembled and co-assembled supramolecular architectures of porphyrins and fullerenes. Then, we show examples of assembly induced by external stimuli. We emphasize the paradigm shift from self-assembly to commanded assembly by describing the recently developed electrochemical-coupling layer-by-layer (ECC-LbL) methodology.

  6. Paradigm shift from self-assembly to commanded assembly of functional materials: recent examples in porphyrin/fullerene supramolecular systems

    Directory of Open Access Journals (Sweden)

    Mao Li, Shinsuke Ishihara, Qingmin Ji, Misaho Akada, Jonathan P Hill and Katsuhiko Ariga

    2012-01-01

    Full Text Available Current nanotechnology based on top-down nanofabrication may encounter a variety of drawbacks in the near future so that development of alternative methods, including the so-called bottom-up approach, has attracted considerable attention. However, the bottom-up strategy, which often relies on spontaneous self-assembly, might be inefficient in the development of the requisite functional materials and systems. Therefore, assembly processes controlled by external stimuli might be a plausible strategy for the development of bottom-up nanotechnology. In this review, we demonstrate a paradigm shift from self-assembly to commanded assembly by describing several examples of assemblies of typical functional molecules, i.e. porphyrins and fullerenes. In the first section, we describe recent progress in the design and study of self-assembled and co-assembled supramolecular architectures of porphyrins and fullerenes. Then, we show examples of assembly induced by external stimuli. We emphasize the paradigm shift from self-assembly to commanded assembly by describing the recently developed electrochemical-coupling layer-by-layer (ECC-LbL methodology.

  7. Controlled short-linkage assembly of functional nano-objects

    Energy Technology Data Exchange (ETDEWEB)

    Chaudhary, Shilpi; Kamra, Tripta [Division of Pure and Applied Biochemistry, Lund University, Box 124, 221 00 Lund (Sweden); ENI AB, Malmö (Sweden); Division of Synchrotron Radiation Research, Lund University, Box 118, 221 00 Lund (Sweden); Uddin, Khan Mohammad Ahsan [Division of Pure and Applied Biochemistry, Lund University, Box 124, 221 00 Lund (Sweden); Snezhkova, Olesia [Division of Synchrotron Radiation Research, Lund University, Box 118, 221 00 Lund (Sweden); Jayawardena, H. Surangi N. [Department of Chemistry, University of Massachusetts Lowell, 1 University Ave., Lowell, MA 01854 (United States); Yan, Mingdi [Department of Chemistry, University of Massachusetts Lowell, 1 University Ave., Lowell, MA 01854 (United States); Department of Chemistry, KTH – Royal Institute of Technology, Teknikringen 30, S-10044 Stockholm (Sweden); Montelius, Lars [ENI AB, Malmö (Sweden); Schnadt, Joachim, E-mail: joachim.schnadt@sljus.lu.se [Division of Synchrotron Radiation Research, Lund University, Box 118, 221 00 Lund (Sweden); Ye, Lei, E-mail: lei.ye@tbiokem.lth.se [Division of Pure and Applied Biochemistry, Lund University, Box 124, 221 00 Lund (Sweden)

    2014-05-01

    Graphical abstract: - Highlights: • Fast photoconjugation of nanoparticles on surface. • Non-destructive feature guarantees intact function of nanoparticles. • Direct contact between nano-objects allows efficient photon and electron transfer. • Possibility of generating patterned nanoparticle assemblies on surface. • Open new opportunities for assembling chemical sensors. - Abstract: In this work, we report a method that allows the deterministic, photo-controlled covalent assembly of nanoparticles directly on surface. As a model system, we study the conjugation of molecularly imprinted polymer (MIP) nanoparticles on a glass surface and confirm that the immobilized nanoparticles maintain their molecular recognition functionality. The glass slide was first modified with perfluorophenylazide and then used to bind MIP nanoparticles under UV irradiation. After each step the surface was analyzed by water contact angle measurement, fluorescence microscopy, scanning electron microscopy, and/or synchrotron-based X-ray photoelectron spectroscopy. The MIP nanoparticles immobilized on the glass surface remained stable and maintained specific binding for the template molecule, propranolol. The method developed in this work allows MIP nanoparticles to be directly coupled to a flat surface, offering a straightforward means to construct robust chemical sensors. Using the reported photo conjugation method, it is possible to generate patterned assembly of nanoparticles using a photomask. Since perfluorophenylazide-based photochemistry works with all kinds of organic material, the method developed in this work is expected to enable immobilization of not only MIPs but also other kinds of organic and inorganic–organic core–shell particles for various applications involving photon or electron transfer.

  8. Systematic study on the sensitivity enhancement in graphene plasmonic sensors based on layer-by-layer self-assembled graphene oxide multilayers and their reduced analogues.

    Science.gov (United States)

    Chung, Kyungwha; Rani, Adila; Lee, Ji-Eun; Kim, Ji Eun; Kim, Yonghwi; Yang, Heejin; Kim, Sang Ouk; Kim, Donghyun; Kim, Dong Ha

    2015-01-14

    The use of graphene in conventional plasmonic devices was suggested by several theoretic research studies. However, the existing theoretic studies are not consistent with one another and the experimental studies are still at the initial stage. To reveal the role of graphenes on the plasmonic sensors, we deposited graphene oxide (GO) and reduced graphene oxide (rGO) thin films on Au films and their refractive index (RI) sensitivity was compared for the first time in SPR-based sensors. The deposition of GO bilayers with number of deposition L from 1 to 5 was carried out by alternative dipping of Au substrate in positively- and negatively charged GO solutions. The fabrication of layer-by-layer self-assembly of the graphene films was monitored in terms of the SPR angle shift. GO-deposited Au film was treated with hydrazine to reduce the GO. For the rGO-Au sample, 1 bilayer sample showed a higher RI sensitivity than bare Au film, whereas increasing the rGO film from 2 to 5 layers reduced the RI sensitivity. In the case of GO-deposited Au film, the 3 bilayer sample showed the highest sensitivity. The biomolecular sensing was also performed for the graphene multilayer systems using BSA and anti-BSA antibody.

  9. Silver nanoprisms self-assembly on differently functionalized silica surface

    Science.gov (United States)

    Pilipavicius, J.; Chodosovskaja, A.; Beganskiene, A.; Kareiva, A.

    2015-03-01

    In this work colloidal silica/silver nanoprisms (NPRs) composite coatings were made. Firstly colloidal silica sols were synthesized by sol-gel method and produced coatings on glass by dip-coating technique. Next coatings were silanized by (3-Aminopropyl)triethoxysilane (APTES), N-[3-(Trimethoxysilyl)propyl]ethylenediamine (AEAPTMS), (3- Mercaptopropyl)trimethoxysilane (MPTMS). Silver NPRs where synthesized via seed-mediated method and high yield of 94±15 nm average edge length silver NPRs were obtained with surface plasmon resonance peak at 921 nm. Silica-Silver NPRs composite coatings obtained by selfassembly on silica coated-functionalized surface. In order to find the most appropriate silanization way for Silver NPRs self-assembly, the composite coatings were characterized by scanning electron microscopy (SEM), dynamic light scattering (DLS), water contact angle (CA) and surface free energy (SFE) methods. Results have showed that surface functionalization is necessary to achieve self-assembled Ag NPRs layer. MPTMS silanized coatings resulted sparse distribution of Ag NPRs. Most homogeneous, even distribution composite coatings obtained on APTES functionalized silica coatings, while AEAPTMS induced strong aggregation of Silver NPRs.

  10. Sequenced defined biomolecules for nanomaterial synthesis, functionalization, and assembly.

    Science.gov (United States)

    Slocik, Joseph M; Naik, Rajesh R

    2017-08-01

    Biomolecules represent an invaluable resource to nanotechnology by providing a large diversity of highly functional biomolecular templates. As a result, these have been extensively used for controlling the synthesis, functionalization, and assembly of nanomaterials, while also creating materials with new properties and structures. In the following, we focus on the use of peptides to achieve these goals and describe their general utility, sequence programmability, and use as templates. Also, we highlight several recent advances in the identification and selection of high affinity nanomaterial-binding peptides, provide a few examples of peptide functionalized surfaces and peptide templated materials, and describe how simple modifications to well characterized nanomaterial-binding peptides can be used to manipulate interactions and physiochemical properties. Published by Elsevier Ltd.

  11. Impact of plant domestication on rhizosphere microbiome assembly and functions.

    Science.gov (United States)

    Pérez-Jaramillo, Juan E; Mendes, Rodrigo; Raaijmakers, Jos M

    2016-04-01

    The rhizosphere microbiome is pivotal for plant health and growth, providing defence against pests and diseases, facilitating nutrient acquisition and helping plants to withstand abiotic stresses. Plants can actively recruit members of the soil microbial community for positive feedbacks, but the underlying mechanisms and plant traits that drive microbiome assembly and functions are largely unknown. Domestication of plant species has substantially contributed to human civilization, but also caused a strong decrease in the genetic diversity of modern crop cultivars that may have affected the ability of plants to establish beneficial associations with rhizosphere microbes. Here, we review how plants shape the rhizosphere microbiome and how domestication may have impacted rhizosphere microbiome assembly and functions via habitat expansion and via changes in crop management practices, root exudation, root architecture, and plant litter quality. We also propose a "back to the roots" framework that comprises the exploration of the microbiome of indigenous plants and their native habitats for the identification of plant and microbial traits with the ultimate goal to reinstate beneficial associations that may have been undermined during plant domestication.

  12. Multilayer Brain Networks

    Science.gov (United States)

    Vaiana, Michael; Muldoon, Sarah Feldt

    2018-01-01

    The field of neuroscience is facing an unprecedented expanse in the volume and diversity of available data. Traditionally, network models have provided key insights into the structure and function of the brain. With the advent of big data in neuroscience, both more sophisticated models capable of characterizing the increasing complexity of the data and novel methods of quantitative analysis are needed. Recently, multilayer networks, a mathematical extension of traditional networks, have gained increasing popularity in neuroscience due to their ability to capture the full information of multi-model, multi-scale, spatiotemporal data sets. Here, we review multilayer networks and their applications in neuroscience, showing how incorporating the multilayer framework into network neuroscience analysis has uncovered previously hidden features of brain networks. We specifically highlight the use of multilayer networks to model disease, structure-function relationships, network evolution, and link multi-scale data. Finally, we close with a discussion of promising new directions of multilayer network neuroscience research and propose a modified definition of multilayer networks designed to unite and clarify the use of the multilayer formalism in describing real-world systems.

  13. Comparison of Multilayer Perceptron and Radial Basis Function Neural Networks in Predicting the Success of New Product Development

    Directory of Open Access Journals (Sweden)

    G. S. Fesghandis

    2017-02-01

    Full Text Available Given that the new product failure in practice entails huge costs for organizations, the need for competitive planning has led organizations to apply appropriate approaches; one of these approaches is to predict new product success before market entry. Accordingly, this study predicts NPD success by comparing two techniques, the Multilayer Perceptron (MLP and the Radial Basis Function (RBF in the clothing industry of Tabriz. In order to collect data, a questionnaire with good validity and reliability was distributed among the population. MLP and RBF were used to analyze data. Based on MSE, RMSE and R2, data analysis showed that MLP had lower error than RBF in predicting NPD success.

  14. Simplified calculation of dipole energy transport in a multilayer stack using dyadic Green's functions.

    Science.gov (United States)

    Celebi, K; Heidel, T D; Baldo, M A

    2007-02-19

    We extend the model of Chance, Prock and Silbey [1] and analytically determine the Poynting vector in the direction perpendicular to the plane of a multilayer organic device. The result is used to predict the spatial profile of Förster energy transfer, the radiative output of an organic light emitting device, and to calculate the efficiency of surface plasmon polariton-mediated energy transfer across a thin silver film.

  15. A simple visible light photo-assisted method for assembling and curing multilayer GO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Pinheiro da Silva, Mauro Francisco, E-mail: mfps@usp.br [Escola Politécnica da Universidade de São Paulo, Departamento de Engenharia Metalúrgica e de Materiais, PMT-EPUSP e Departamento de Engenharia de Sistemas Eletrônicos, PSI-EPUSP, Av. Professor Mello Moraes, n° 2463, Cidade Universitária, CEP 05508-030, São Paulo, SP (Brazil); Pontifícia Universidade de São Paulo, Faculdade de Ciências Exatas e Tecnologia, Rua Marquês de Paranaguá, 111, CEP 01303-050, São Paulo, SP (Brazil); Oliveira, Débora Rose de [Instituto de Criminalística da Secretaria de Segurança do Estado de São Paulo, Núcleo de Química, Rua Moncorvo Filho, CEP 05507-060, São Paulo, SP (Brazil); Pontifícia Universidade de São Paulo, Faculdade de Ciências Exatas e Tecnologia, Rua Marquês de Paranaguá, 111, CEP 01303-050, São Paulo, SP (Brazil); and others

    2015-09-01

    A simple and efficient method for deposition of reduced graphene oxide (RGO) thin films onto arbitrary substrates is described. The present protocol consists in the application of radial compression to a thin layer of graphene oxide (GO) formed at the air–liquid interface of an ammoniacal dispersion of graphene oxide by continuous irradiation with visible light, that drives both the formation and curing of the film. Both infrared and near infrared luminescence spectroscopies were used for the proposition of a chemical mechanism in which the in situ singlet oxygen Δ{sup 1}O{sub 2}, generated by the photosensitization of molecular oxygen to visible light, initiates the formation and curing of the film. The GO and RGO films display Raman spectral signatures typical of graphene – based materials, with thickness of ca. 20 nm as evaluated by atomic force microscopy. The deposited films exhibited good transparency to visible light (max. 85%; 550 ± 2 nm), electrical resistivity equals to 14 ± 0.02 Ω m, sheet resistance equals to 5 kΩ sq{sup −1} with associated charge carrier mobility of 200 cm{sup 2}/V s. - Highlights: • Visible light photochemical assembly of self-supported graphene oxide thin films. • Graphene oxide photosensitizer for in situ production of singlet oxygen Δ{sup 1}O{sub 2}. • Δ{sup 1}O{sub 2}, as initiator of formation and curing of graphene oxide thin film. • Deposition of colloidal graphene oxide thin film by radial compression. • Deposition of graphene oxide thin film in arbitrary solid substrate.

  16. Polymeric multilayer capsules in drug delivery.

    Science.gov (United States)

    De Cock, Liesbeth J; De Koker, Stefaan; De Geest, Bruno G; Grooten, Johan; Vervaet, Chris; Remon, Jean Paul; Sukhorukov, Gleb B; Antipina, Maria N

    2010-09-17

    Recent advances in medicine and biotechnology have prompted the need to develop nanoengineered delivery systems that can encapsulate a wide variety of novel therapeutics such as proteins, chemotherapeutics, and nucleic acids. Moreover, these delivery systems should be "intelligent", such that they can deliver their payload at a well-defined time, place, or after a specific stimulus. Polymeric multilayer capsules, made by layer-by-layer (LbL) coating of a sacrificial template followed by dissolution of the template, allow the design of microcapsules in aqueous conditions by using simple building blocks and assembly procedures, and provide a previously unmet control over the functionality of the microcapsules. Polymeric multilayer capsules have recently received increased interest from the life science community, and many interesting systems have appeared in the literature with biodegradable components and biospecific functionalities. In this Review we give an overview of the recent breakthroughs in their application for drug delivery.

  17. Laccase-Functionalized Graphene Oxide Assemblies as Efficient Nanobiocatalysts for Oxidation Reactions

    NARCIS (Netherlands)

    Patila, Michaela; Kouloumpis, Antonios; Gournis, Dimitrios; Rudolf, Petra; Stamatis, Haralambos

    Multi-layer graphene oxide-enzyme nanoassemblies were prepared through the multi-point covalent immobilization of laccase from Trametes versicolor (TvL) on functionalized graphene oxide (fGO). The catalytic properties of the fGO-TvL nanoassemblies were found to depend on the number of the graphene

  18. Construction of antibacterial multilayer films containing nanosilver via layer-by-layer assembly of heparin and chitosan-silver ions complex.

    Science.gov (United States)

    Fu, Jinhong; Ji, Jian; Fan, Dezeng; Shen, Jiacong

    2006-12-01

    Antibacterial multilayer films containing nanosilver were prepared via layer-by-layer fashion. PET film was aminolyzed with 1,6-hexanediamine to introduce amino groups on PET film surface; chitosan-silver nitrate complex and heparin were alternately deposited onto an aminolyzed PET film surface, and subsequently, the silver ions within the multilayer films were reduced with ascorbic acid to form silver nanoparticles. UV-visible spectroscopy and transmission electron microscopy confirmed the formation of well-dispersed nanosilver particles with sizes (10-40 nm) that depended on the initial concentration of silver ions in chitosan solution and the pH of ascorbic acid solution. The chitosan/heparin multilayer films were possessed of bactericidal effect on Escherichia coli (E. coli), and this antibacterial effect could be significantly enhanced by the incorporation of silver nanoparticles into the multilayer films. The multilayer films containing nanosilver were not only effective as antibacterial but also as anticoagulant coating. And cell toxicity evaluation suggested that the multilayer films containing nanosilver did not show any cytotoxicity. The multilayer films containing nanosilver may have good potentials for surface modification of medical devices, especially for cardiovascular implants.

  19. Amazonian functional diversity from forest canopy chemical assembly.

    Science.gov (United States)

    Asner, Gregory P; Martin, Roberta E; Tupayachi, Raul; Anderson, Christopher B; Sinca, Felipe; Carranza-Jiménez, Loreli; Martinez, Paola

    2014-04-15

    Patterns of tropical forest functional diversity express processes of ecological assembly at multiple geographic scales and aid in predicting ecological responses to environmental change. Tree canopy chemistry underpins forest functional diversity, but the interactive role of phylogeny and environment in determining the chemical traits of tropical trees is poorly known. Collecting and analyzing foliage in 2,420 canopy tree species across 19 forests in the western Amazon, we discovered (i) systematic, community-scale shifts in average canopy chemical traits along gradients of elevation and soil fertility; (ii) strong phylogenetic partitioning of structural and defense chemicals within communities independent of variation in environmental conditions; and (iii) strong environmental control on foliar phosphorus and calcium, the two rock-derived elements limiting CO2 uptake in tropical forests. These findings indicate that the chemical diversity of western Amazonian forests occurs in a regionally nested mosaic driven by long-term chemical trait adjustment of communities to large-scale environmental filters, particularly soils and climate, and is supported by phylogenetic divergence of traits essential to foliar survival under varying environmental conditions. Geographically nested patterns of forest canopy chemical traits will play a role in determining the response and functional rearrangement of western Amazonian ecosystems to changing land use and climate.

  20. Light-controlled drug releasing polymer films combining LbL self-assembly and host-guest interactions

    OpenAIRE

    Li, J; He, L.; J. Wang; Zhang, Z. T.; Shi, J.; X. Z. Zhang(Department of Nuclear Physics and Beijing Tandem Accelerator National Laboratory, Beijing, China); Cao, Y.P.; Y. Chen

    2014-01-01

    By combining LbL (layer-by-layer) self-assembly approach and host-guest interactions, a unique multilayer film was constructed and employed for a light-controlled drug release system. The drug molecules can be loaded and released into the resulting polyelectrolyte multilayers containing azobenzene (Azo) function groups by using the irradiation of visible light and UV light alternately. The photo-sensitivity of the multilayer films was studied through UV-vis spectrum, fluorescence spectrum and...

  1. Modulating Hole Transport in Multilayered Photocathodes with Derivatized p-Type Nickel Oxide and Molecular Assemblies for Solar-Driven Water Splitting

    Energy Technology Data Exchange (ETDEWEB)

    Shan, Bing [Department; Sherman, Benjamin D. [Department; Klug, Christina M. [Center; Nayak, Animesh [Department; Marquard, Seth L. [Department; Liu, Qing [Department; Bullock, R. Morris [Center; Meyer, Thomas J. [Department

    2017-08-31

    We report here a new photocathode composed of a bi-layered doped NiO film topped by a macro-mesoporous ITO (ioITO) layer with molecular assemblies attached to the ioITO surface. The NiO film containing a 2% K+ doped NiO inner layer and a 2% Cu2+ doped NiO outer layer provides sufficient driving force for hole transport after injection to NiO by the molecular assembly. The tri-layered oxide, NiK0.02O | NiCu0.02O | ioITO, sensitized by a ruthenium polypyridyl dye and functionalized with a nickel-based hydrogen evolution catalyst, outperforms its counterpart, NiO | NiO | ioITO, in photocatalytic hydrogen evolution from water over a period of several hours with a Faradaic yield of ~90%.

  2. Vibroacoustic study on a multilayered functionally graded cylindrical shell with poroelastic core and bonded-unbonded configuration

    Science.gov (United States)

    Daneshjou, K.; Talebitooti, R.; Kornokar, M.

    2017-04-01

    This paper presents an analytical solution for sound transmission through a multilayered cylindrical shell with bonded-unbonded (BU) configuration. The multilayered cylindrical shell, which is composed of an outer layer of functionally graded material (FGM) and an inner isotropic layer with a poroelastic core and an air gap, is assumed to be infinitely long and is subjected to a plane wave on its external sidewall. To describe the poroelastic core, the extended full method (EFM) is applied based on Biot's theory. Contrary to previous methods, the EFM completely models the poroelastic cylindrical shell in three dimensions. In addition, the motions of both FGM and isotropic shells are described with the first order shear deformation theory (FSDT). Unlike the simplified method, the EFM does not need to identify the frequency ranges where one of the airborne or frame waves is dominant in BU configuration. In fact, utilizing the EFM for BU configuration permits obtaining the sound transmission loss (TL) irrespective of the dominant wave, which significantly reduces the computational work. Moreover, comparing with the previous models, the EFM provides more accurate results as it does not ignore any term in the modeling. Furthermore, the advantages of the BU-FGM shell in enhancing the TL are demonstrated with respect to the BB-isotropic configuration. It is shown that presence of the FGM in addition to the poroelastic material in a structure yields thermal insulation and improves soundproofing characteristics in a broadband frequency range.

  3. Investigation of functionalized silicon nanowires by self-assembled monolayer

    Energy Technology Data Exchange (ETDEWEB)

    Hemed, Nofar Mintz [Dept. of Physical Electronics, Eng. Faculty, and the University Res. Inst. for Nano Science and Nano-Technologies, Tel-Aviv University, Ramat-Aviv 69978 (Israel); Convertino, Annalisa [Istituto per la Microelettronica e i Microsistemi C.N.R.-Area della Ricerca di Roma, via del Fosso del Cavaliere 100, I-00133 Roma (Italy); Shacham-Diamand, Yosi [Dept. of Physical Electronics, Eng. Faculty, and the University Res. Inst. for Nano Science and Nano-Technologies, Tel-Aviv University, Ramat-Aviv 69978 (Israel); The Department of Applied Chemistry, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan)

    2016-03-30

    Graphical abstract: - Highlights: • We characterize and verify the existence of self-assembled monolayer (SAM) on silicon nanowires and α-Si:H. • We define the term “electrical coverage” and find the formula for both cases. • The SAM's electrical coverage on silicon nanowires is found to be ∼63%. • The SAM's electrical coverage on α-Si:H is found to be ∼65 ± 3%. • The amount of SAM on the SiNWs is sufficient and it can serve as a linker to biological molecules. - Abstract: The functionalization using self assembled monolayer (SAM) of silicon nanowires (SiNW) fabricated by plasma enhanced chemical vapor deposition (PECVD) is reported here. The SAM is being utilized as the first building block in the functionalization process. The morphology of the SiNW comprises a polycrystalline core wrapped by an hydrogenated amorphous silicon (α-Si:H) shell. Since most of the available methods for SAM verification and characterization are suitable only for flat substrates; therefore, in addition to the SiNW α-Si:H on flat samples were produced in the same system as the SiNWs. First we confirmed the SAM's presence on the flat α-Si:H samples using the following methods: contact angle measurement to determine the change in surface energy; atomic force microscopy (AFM) to determine uniformity and molecular coverage. Spectroscopic ellipsometry and X-ray reflectivity (XRR) were performed to measure SAM layer thickness and density. X-ray photoelectron spectroscopy (XPS) was applied to study the chemical states of the surface. Next, SiNW/SAM were tested by electrochemical impedance spectroscopy (EIS), and the results were compared to α-Si:H/SAM. The SAM electrical coverage on SiNW and α-Si:H was found to be ∼37% and ∼65 ± 3%, respectively. A model, based on transmission line theory for the nanowires is presented to explain the disparity in results between the nanowires and flat surface of the same materials.

  4. Functional self-assembling bolaamphiphilic polydiacetylenes as colorimetric sensor scaffolds

    Energy Technology Data Exchange (ETDEWEB)

    Song, Jie; Cisar, Justin S.; Bertozzi, Carolyn R.

    2004-05-28

    Conjugated polymers capable of responding to external stimuli by changes in optical, electrical or electrochemical properties can be used for the construction of direct sensing devices. Polydiacetylene-based systems are attractive for sensing applications due to their colorimetric response to changes in the local environment. Here we present the design, preparation and characterization of self-assembling functional bolaamphiphilic polydiacetylenes (BPDAs) inspired by Nature's strategy for membrane stabilization. We show that by placing polar headgroups on both ends of the diacetylene lipids in a transmembranic fashion, and altering the chemical nature of the polar surface residues, the conjugated polymers can be engineered to display a range of radiation-, thermal- and pH-induced colorimetric responses. We observed dramatic nanoscopic morphological transformations accompanying charge-induced chromatic transitions, suggesting that both side chain disordering and main chain rearrangement play important roles in altering the effective conjugation lengths of the poly(ene-yne). These results establish the foundation for further development of BPDA-based colorimetric sensors.

  5. Probing the surface microstructure of layer-by-layer self-assembly chitosan/poly(L-glutamic acid) multilayers: A grazing-incidence small-angle X-ray scattering study

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Nie; Yang, Chunming, E-mail: yangchunming@sinap.ac.cn; Wang, Yuzhu; Zhao, Binyu; Bian, Fenggang; Li, Xiuhong; Wang, Jie, E-mail: wangjie@sinap.ac.cn

    2016-01-01

    This study characterized the surface structure of layer-by-layer self-assembly chitosan/poly(L-glutamic acid) multilayers through grazing-incidence small-angle X-ray scattering (GISAXS), X-ray reflectivity (XRR), and atomic force microscopy (AFM). A weakly long-period ordered structure along the in-plane direction was firstly observed in the polyelectrolyte multilayer by the GISAXS technique. This structure can be attributed to the specific domains on the film surface. In the domain, nanodroplets that were formed by polyelectrolyte molecules were orderly arranged along the free surface of the films. This ordered structure gradually disappeared with the increasing bilayer number because of the complex merging behavior of nanodroplets into large islands. Furthermore, resonant diffuse scattering became evident in the GISAXS patterns as the number of bilayers in the polyelectrolyte multilayer was increased. Notably, the lateral cutoff length of resonant diffuse scattering for these polyelectrolyte films was comparable with the long-period value of the ordered nanodroplets in the polyelectrolyte multilayer. Therefore, the nanodroplets could be considered as a basic transmission unit for structure propagation from the inner interface to the film surface. It suggests that the surface structure with length scale larger than the size of nanodroplets was partially complicated from the interface structure near the substrate, but surface structure smaller than the cutoff length was mainly depended on the conformation of nanodroplets. - Highlights: • The growth of ordered nanodroplets in PEMs was characterized by the GISAXS technique. • The basic transmission units for structure propagation within PEMs were nanodroplets. • High-performance of wave-guiding devices prepared by PEMs was predicted.

  6. Functionalization and Self-Assembly of DNA Bidimensional Arrays

    Directory of Open Access Journals (Sweden)

    Ramon Eritja

    2011-09-01

    Full Text Available Oligonucleotides carrying amino, thiol groups, as well as fluorescein, c-myc peptide sequence and nanogold at internal positions were prepared and used for the assembly of bidimensional DNA arrays.

  7. Block copolymer self-assembly and co-assembly : shape function and application

    NARCIS (Netherlands)

    Li, F.

    2009-01-01

    Amphiphilic block copolymers can, in selective solvents such as water, assemble into various shapes and architectures. Among those, polymer vesicles, polymer micelles and polymer fibers are very popular structures in current nanotechnology. These objects each have their own particular properties and

  8. Preservation of the morphology of a self-encapsulated thin titania film in a functional multilayer stack: an X-ray scattering study.

    Science.gov (United States)

    Perlich, Jan; Memesa, Mine; Diethert, Alexander; Metwalli, Ezzeldin; Wang, Weinan; Roth, Stephan V; Timmann, Andreas; Gutmann, Jochen S; Müller-Buschbaum, Peter

    2009-03-23

    Tailoring of the titania morphology is achieved by the combination of a triblock copolymer, acting as structure-directing agent, and a sol-gel chemistry enabling the incorporation of the provided inorganic material (titania) into the selected phase of the triblock copolymer. Spin-coating of the solution on FTO-coated glass, followed by plasma etching and calcination of the thin film results in the formation of self-encapsulated crystalline titania nanostructures. The fabricated nanostructures are coated stepwise with dye, conductive polymers and gold forming a functional multilayer stack. An advanced small-angle scattering technique probing the sample with X-ray synchrotron radiation under grazing incidence (GISAXS) is employed for the characterization of the preparation route, as scattering allows accessing the structure inside the multilayers. The tailored titania morphology is preserved during the preparation route towards the functional multilayer stack of a photovoltaic demonstration cell. Two clearly distinguishable structures originate from the substrate and the titania templated by the triblock copolymer; hence the other layers induce no additional structures. Therefore, this investigation provides the evidence that the effort spent to tailor the morphology is justified by the preservation of the self-encapsulated titania morphology that is created by the structure-directing agent throughout the functional multilayer stack build-up.

  9. Multilayered Magnetic Gelatin Membrane Scaffolds

    Science.gov (United States)

    Samal, Sangram K.; Goranov, Vitaly; Dash, Mamoni; Russo, Alessandro; Shelyakova, Tatiana; Graziosi, Patrizio; Lungaro, Lisa; Riminucci, Alberto; Uhlarz, Marc; Bañobre-López, Manuel; Rivas, Jose; Herrmannsdörfer, Thomas; Rajadas, Jayakumar; De Smedt, Stefaan; Braeckmans, Kevin; Kaplan, David L.; Dediu, V. Alek

    2016-01-01

    A versatile approach for the design and fabrication of multilayer magnetic scaffolds with tunable magnetic gradients is described. Multilayer magnetic gelatin membrane scaffolds with intrinsic magnetic gradients were designed to encapsulate magnetized bioagents under an externally applied magnetic field for use in magnetic-field-assisted tissue engineering. The temperature of the individual membranes increased up to 43.7 °C under an applied oscillating magnetic field for 70 s by magnetic hyperthermia, enabling the possibility of inducing a thermal gradient inside the final 3D multilayer magnetic scaffolds. On the basis of finite element method simulations, magnetic gelatin membranes with different concentrations of magnetic nanoparticles were assembled into 3D multilayered scaffolds. A magnetic-gradient-controlled distribution of magnetically labeled stem cells was demonstrated in vitro. This magnetic biomaterial–magnetic cell strategy can be expanded to a number of different magnetic biomaterials for various tissue engineering applications. PMID:26451743

  10. Symposium Supramolecular Assemblies on Surface: Nanopatterning, Functionality and Reactivity

    Science.gov (United States)

    2016-05-19

    describe the self- assembly of organic semiconductors on graphene surface for high performance vertical transistors. 2268 - On-surface polymerization – a...1,2 Graphene nanoribbon (GNR) which is predicted to behave as semiconductor , is a promising material for many applications. Compared with top-down...Presenter Institution Start End Time Day Dura De Feyter, Steven Molecular self‐assembly on  graphene  and graphite: from fundamentals to applic KU Leuven 8:05

  11. Influence of persistent monodominance on functional diversity and functional community assembly in African tropical forests.

    Science.gov (United States)

    Kearsley, Elizabeth; Verbeeck, Hans; Hufkens, Koen; Beeckman, Hans; Steppe, Kathy; Boeckx, Pascal; Huygens, Dries

    2015-04-01

    Lowland tropical rainforest are taxonomically diverse and complex systems, although not all tropical communities are equally diverse. Naturally occuring monodominant patches of Gilbertiodendron dewevrei are commonly found across Central Africa alongside higher diversity forests. Nevertheless, a low taxonomical diversity does not necessarily indicate an equivalently low functional diverse system. We investigate the functional diversity and functional community assembly of mixed and monodominant tropical forests in a central region of the Congo Basin in D. R. Congo using 15 leaf and wood traits covering 95% of all species within each community. This unique dataset allows us to investigate differences in functional diversity and ecosystem functioning between mixed and monodominant forest types. Functional richness, functional divergence and functional evenness are three functional diversity measures providing different aspects of functional diversity. The largest difference between the two forest types was found for functional richness, with a lower functional richness in the monodominant forest indicating a higher amount of niche space filled in the mixed forest. The mixed forest also had a higher species richness and Simpson diversity index, indicating that the higher species richness increases the functional niche space. Subsequently, we identified whole community trait shifts within the monodominant forest compared to the mixed forest. The dominance of Gilbertiodendron dewevrei, for which a distinct niche is found for most traits, presented a significant influence on the entire (trait) community expressing fundamental differences in ecosystem functioning. More detailed investigation of species unique within the monodominant forest and species occurring in both forest types provide more insight into the influence of Gilbertiodendron dewevrei. Both the unique and the shared species showed significant shifts in leaf nutrients, specific leaf area and water use

  12. Effects of vacuum heat treatment on the photoelectric work function and surface morphology of multilayered silver–metal electrical contacts

    Energy Technology Data Exchange (ETDEWEB)

    Akbi, Mohamed, E-mail: akbi_mohamed@umbb.dz [Laboratoire “Arc Electrique et Plasmas Thermiques”, CNRS, UPRES-A 6069, 24, Avenue des Landais, F-63177 Aubière Cedex (France); Department of Physics, Faculty of Sciences, University of Boumerdes (UMBB), Independence Avenue, 35000 Boumerdes (Algeria); Bouchou, Aïssa [Faculty of Physics, University of Algiers (USTHB), B.P. 32, El-Alia, Bab-Ezzouar, 16111 Algiers (Algeria); Zouache, Noureddine [Laboratoire “Arc Electrique et Plasmas Thermiques”, CNRS, UPRES-A 6069, 24, Avenue des Landais, F-63177 Aubière Cedex (France)

    2014-06-01

    Contact materials used for electrical breakers are often made with silver alloys. Mechanical and thermodynamical properties as well as electron emission of such complicated alloys present a lack of reliable and accurate experimental data. This paper deals mainly with electron work function (EWF) measurements about silver–metal (Ag–Me) electrical contacts (Ag–Ni (60/40) and Ag–W (50/50)), before and after surface heat treatments at 513 K–873 K, under UHV conditions (residual gas pressure of 1.4 × 10{sup −7} mbar). The electron work function (EWF) of silver alloyed contacts was measured photoelectrically, using both Fowler's method of isothermal curves and linearized Fowler plots. An interesting fact brought to light by this investigation is that after vacuum heat treatments, the diffusion and/or evaporation phenomena, affecting the atomic composition of the alloy surface, somehow confine the EWF of the silver–nickel alloy, Φ(Ag–Ni), determined at room temperature in interval]Φ(Ag), Φ(Ni) [=] 4.26 eV, 4.51 eV[. Surface analysis of two specimens before and after heating showed a significant increase of tungsten atomic proportion on the contact surface for Ag–W contacts after VH treatments. A multilayer model, taking into account the strong intergranular and volume segregation gives a good interpretation of the obtained results.

  13. Biocompatible and Biomimetic Self-Assembly of Functional Nanostructures

    Science.gov (United States)

    2010-02-28

    and C. J. Brinker, "Photoresponsive nanocomposite formed by self-assembly of an azobenzene -modified silane," Angew. Chem.-Int. Edit. 42 (15), 1731...Responsive Materials: Azobenzene Containing Polymers and Liquid Crystals,U Yue Zhao and Tomiki Ikeda, eds., John Wiley & Sons, Inc., Hoboken, NJ...phagocyte- derived oxidants: New role for the NADPH oxidase in host defense. Proc Natl Acad Sci U S A. 101, 13867-13872 (2004). xviii. Iler, R.K

  14. Mussel-inspired nano-building block assemblies for mimicking extracellular matrix microenvironments with multiple functions.

    Science.gov (United States)

    Wang, Zhenming; Jia, Zhanrong; Jiang, Yanan; Li, Pengfei; Han, Lu; Lu, Xiong; Ren, Fuzeng; Wang, Kefeng; Yuan, Huiping

    2017-08-03

    The assembly of nano-building blocks is an effective way to produce artificial extracellular matrix microenvironments with hierarchical micro/nano structures. However, it is hard to assemble different types of nano-building blocks, to form composite coatings with multiple functions, by traditional layer-by-layer (LbL) self-assembly methods. Inspired by the mussel adhesion mechanism, we developed polydopamine (PDA)-decorated bovine serum albumin microspheres (BSA-MS) and nano-hydroxyapatite (nano-HA), and assembled them to form bioactive coatings with micro/nano structures encapsulating bone morphogenetic protein-2 (BMP-2). First, PDA-decorated nano-HA (nano-pHA) was obtained by oxidative polymerization of dopamine on nano-HA. Second, BMP-2-encapsulated BSA microspheres were prepared through desolvation, and then were also decorated by PDA (pBSA-MS). Finally, the nano-pHA and pBSA-MS were assembled using the adhesive properties of PDA. Bone marrow stromal cell cultures and in vivo implantation, showed that the pHA/pBSA (BMP-2) coatings can promote cell adhesion, proliferation, and benefited for osteoinductivity. PDA decoration was also applied to assemble various functional nanoparticles, such as nano-HA, polystyrene, and Fe3O4 nanoparticles. In summary, this study provides a novel strategy for the assembly of biofunctional nano-building blocks, which surpasses traditional LbL self-assembly of polyelectrolytes, and can find broad applications in bioactive agents delivery or multi-functional coatings.

  15. A study on the role and function of the national assembly in the nuclear policy process

    Energy Technology Data Exchange (ETDEWEB)

    Lee, J. H.; Yoon, Y. J.; Lim, I. S.; Park, Y. S.; Han, C. S.; Kim, Y. T.; Gong, J. S

    2005-03-15

    This report provides that the systemic understanding on the role and function of National assembly in the nuclear policy making processes. Public are growing more and more interested and have a voice in nuclear policy. However, the expansion of public participation has the risk of falling into the deadlock of unreasonable populism, so the course and procedures of public participation need to be included in the rational institutional process of nuclear policy making. Accordingly, this report proposes that strategic response methods in political process in the National assembly. First, we are to establish scenario and its respond strategy for the sudden change of regulatory system. Second, we are to understand institutional role and functional properties of national assembly and have a contact point to national subcommittee. Finally, Because Term of a member the National Assembly is 4 years, we struggle to keep up good relationship with National assembly subcommittee members.

  16. RPA binds histone H3-H4 and functions in DNA replication-coupled nucleosome assembly.

    Science.gov (United States)

    Liu, Shaofeng; Xu, Zhiyun; Leng, He; Zheng, Pu; Yang, Jiayi; Chen, Kaifu; Feng, Jianxun; Li, Qing

    2017-01-27

    DNA replication-coupled nucleosome assembly is essential to maintain genome integrity and retain epigenetic information. Multiple involved histone chaperones have been identified, but how nucleosome assembly is coupled to DNA replication remains elusive. Here we show that replication protein A (RPA), an essential replisome component that binds single-stranded DNA, has a role in replication-coupled nucleosome assembly. RPA directly binds free H3-H4. Assays using a synthetic sequence that mimics freshly unwound single-stranded DNA at replication fork showed that RPA promotes DNA-(H3-H4) complex formation immediately adjacent to double-stranded DNA. Further, an RPA mutant defective in H3-H4 binding exhibited attenuated nucleosome assembly on nascent chromatin. Thus, we propose that RPA functions as a platform for targeting histone deposition to replication fork, through which RPA couples nucleosome assembly with ongoing DNA replication. Copyright © 2017, American Association for the Advancement of Science.

  17. Microbial community assembly and metabolic function during mammalian corpse decomposition

    Energy Technology Data Exchange (ETDEWEB)

    Metcalf, J. L.; Xu, Z. Z.; Weiss, S.; Lax, S.; Van Treuren, W.; Hyde, E. R.; Song, S. J.; Amir, A.; Larsen, P.; Sangwan, N.; Haarmann, D.; Humphrey, G. C.; Ackermann, G.; Thompson, L. R.; Lauber, C.; Bibat, A.; Nicholas, C.; Gebert, M. J.; Petrosino, J. F.; Reed, S. C.; Gilbert, J. A.; Lynne, A. M.; Bucheli, S. R.; Carter, D. O.; Knight, R.

    2015-12-10

    Vertebrate corpse decomposition provides an important stage in nutrient cycling in most terrestrial habitats, yet microbially mediated processes are poorly understood. Here we combine deep microbial community characterization, community-level metabolic reconstruction, and soil biogeochemical assessment to understand the principles governing microbial community assembly during decomposition of mouse and human corpses on different soil substrates. We find a suite of bacterial and fungal groups that contribute to nitrogen cycling and a reproducible network of decomposers that emerge on predictable time scales. Our results show that this decomposer community is derived primarily from bulk soil, but key decomposers are ubiquitous in low abundance. Soil type was not a dominant factor driving community development, and the process of decomposition is sufficiently reproducible to offer new opportunities for forensic investigations.

  18. Microbial community assembly and metabolic function during mammalian corpse decomposition

    Science.gov (United States)

    Metcalf, Jessica L; Xu, Zhenjiang Zech; Weiss, Sophie; Lax, Simon; Van Treuren, Will; Hyde, Embriette R.; Song, Se Jin; Amir, Amnon; Larsen, Peter; Sangwan, Naseer; Haarmann, Daniel; Humphrey, Greg C; Ackermann, Gail; Thompson, Luke R; Lauber, Christian; Bibat, Alexander; Nicholas, Catherine; Gebert, Matthew J; Petrosino, Joseph F; Reed, Sasha C.; Gilbert, Jack A; Lynne, Aaron M; Bucheli, Sibyl R; Carter, David O; Knight, Rob

    2016-01-01

    Vertebrate corpse decomposition provides an important stage in nutrient cycling in most terrestrial habitats, yet microbially mediated processes are poorly understood. Here we combine deep microbial community characterization, community-level metabolic reconstruction, and soil biogeochemical assessment to understand the principles governing microbial community assembly during decomposition of mouse and human corpses on different soil substrates. We find a suite of bacterial and fungal groups that contribute to nitrogen cycling and a reproducible network of decomposers that emerge on predictable time scales. Our results show that this decomposer community is derived primarily from bulk soil, but key decomposers are ubiquitous in low abundance. Soil type was not a dominant factor driving community development, and the process of decomposition is sufficiently reproducible to offer new opportunities for forensic investigations.

  19. Supramolecular Langmuir monolayers and multilayered vesicles of self-assembling DNA–lipid surface structures and their further implications in polyelectrolyte-based cell transfections

    Energy Technology Data Exchange (ETDEWEB)

    Demirsoy, Fatma Funda Kaya [Ankara University, The Central Laboratory of The Institute of Biotechnology (Turkey); Eruygur, Nuraniye [Gazi University, Department of Pharmacognosy, Faculty of Pharmacy (Turkey); Süleymanoğlu, Erhan, E-mail: erhans@mail.ru [Gazi University, Department of Pharmaceutical Chemistry, Faculty of Pharmacy (Turkey)

    2015-01-15

    The basic interfacial characteristics of DNA–lipid recognitions have been studied. The complex structures of individual unbound DNA molecules and their binary and ternary complexes with zwitterionic lipids and divalent cations were followed by employing lipid monolayers at the air–liquid interfaces, as well as by performing various microscopic, spectroscopic, and thermodynamic measurements with multilayered vesicles. The pressure-area isotherms depicted that Mg{sup 2+}-ions increase the surface pressure of lipid films and thus give rise to electrostatic and hydrophobic lipid–DNA interactions in terms of DNA adsorption, adhesion, and compaction. These features were further approached by using multilamellar vesicles with a mean diameter of 850 nm, where a metal ion-directed nucleic acid compaction and condensation effects were shown. The data obtained show the effectiveness of Langmuir monolayers and lipid multilayers in studying nucleic acid–lipid recognitions. The data provide with further details and support previous reports on mainly structural features of these recognitions. Biomolecular surface recognition events were presented in direct link with spectral and thermodynamic features of lipid vesicle–polynucleotide complex formations. The results serve to build a theoretical model considering the use of neutral lipids in lipoplex designs as a polyelectrolyte alternatives to the currently employed cytotoxic cationic liposomes. The supramolecular structures formed and their possible roles in interfacial electrostatic and hydrophobic mechanisms of endosomal escape in relevant cell transfection assays are particularly emphasized.

  20. Self-assembly of a functional electronic circuit directed by capillary interactions

    Science.gov (United States)

    Reynolds, K.; O'Riordan, A.; Redmond, G.

    2010-01-01

    We report on the use of capillary interactions to drive the self-assembly of an electronic circuit based on mesoscale building blocks. The specific target structure is a linear heterotetramer comprising non-identical millimetre-scale cubic blocks that, following assembly, forms a functioning astable multivibrator circuit. Importantly, the self-assembly process is designed to be unconstrained, i.e., each of the blocks are free to move in any way during assembly. To this end, solder droplets are selectively patterned on the block faces. On contact, capillary interactions between shape complimentary solder patterns on the blocks cause the molten solder droplets to coalesce and the blocks to self-assemble. In this way, capillary forces direct the alignment, registration, linking and electrical interconnection of each block during the assembly process. This demonstration of mesoscale self-assembly mediated by capillary interactions illustrates that the application of unconventional assembly paradigms to complex structure fabrication is feasible and that these approaches may yet yield viable strategies for fabrication of highly integrated systems.

  1. Self-Assembly and Surface-Patterning of Polymer-Functionalized Nanoparticles

    Science.gov (United States)

    Choueiri, Rachel

    This thesis explores the preparation of polymer-functionalized nanoparticles, the surface-segregation of their polymer ligands to generate patchy nanocolloids, and the use of patchy and non-patchy polymer-functionalized nanoparticles as building blocks for self-assembly. In Chapter 3, the self-assembly of nanospheres uniformly functionalized with polymer was explored. Both chain-like and globular structures were generated from the same spherical nanoparticle building blocks by tuning the interplay of nanoscale forces. The molecular weight of polymer ligands and the polarity and ionic strength of the self-assembly medium were changed to adjust the interparticle hydrophobic attraction and electrostatic repulsion in order to obtain the desired self-assembled structure. The experimental results were in agreement with theoretical predictions for the most thermodynamically favourable self-assemblies. Hierarchical structures made from assembled globules of nanospheres were also generated and the reversibility of the self-assemblies was demonstrated. In Chapter 4, the segregation of polymer ligands into pinned micelles on the surface of nanospheres was explored. Single and multi-patch nanospheres were generated by studying the interplay of nanosphere curvature and polymer molecular weight. The statistics of patchy nanosphere species was quantified and compared to theoretical predictions. Permanent crosslinking of polymer patches was achieved in addition to tomography of the generated colloids to further characterize the morphology. In Chapter 5, the surface segregation of polymer ligands on nanoparticles with different shapes and composition such as spherocylindrical nanorods, nanorods with a dumbbell shape, and nanocubes was demonstrated. The surface segregation of different polymers (including pH-responsive and conductive polymers) on nanospheres was also achieved demonstrating the versatility of the polymer segregation approach for nanopatterning. In addition, the self-assembly

  2. Assembly of a functional Machupo virus polymerase complex.

    Science.gov (United States)

    Kranzusch, Philip J; Schenk, Andreas D; Rahmeh, Amal A; Radoshitzky, Sheli R; Bavari, Sina; Walz, Thomas; Whelan, Sean P J

    2010-11-16

    Segmented negative-sense viruses of the family Arenaviridae encode a large polymerase (L) protein that contains all of the enzymatic activities required for RNA synthesis. These activities include an RNA-dependent RNA polymerase (RdRP) and an RNA endonuclease that cleaves capped primers from cellular mRNAs to prime transcription. Using purified catalytically active Machupo virus L, we provide a view of the overall architecture of this multifunctional polymerase and reconstitute complex formation with an RNA template in vitro. The L protein contains a central ring domain that is similar in appearance to the RdRP of dsRNA viruses and multiple accessory appendages that may be responsible for 5' cap formation. RNA template recognition by L requires a sequence-specific motif located at positions 2-5 in the 3' terminus of the viral genome. Moreover, L-RNA complex formation depends on single-stranded RNA, indicating that inter-termini dsRNA interactions must be partially broken for complex assembly to occur. Our results provide a model for arenavirus polymerase-template interactions and reveal the structural organization of a negative-strand RNA virus L protein.

  3. Micro-/nanostructured multicomponent molecular materials: design, assembly, and functionality.

    Science.gov (United States)

    Yan, Dongpeng

    2015-03-23

    Molecule-based micro-/nanomaterials have attracted considerable attention because their properties can vary greatly from the corresponding macro-sized bulk systems. Recently, the construction of multicomponent molecular solids based on crystal engineering principles has emerged as a promising alternative way to develop micro-/nanomaterials. Unlike single-component materials, the resulting multicomponent systems offer the advantages of tunable composition, and adjustable molecular arrangement, and intermolecular interactions within their solid states. The study of these materials also supplies insight into how the crystal structure, molecular components, and micro-/nanoscale effects can influence the performance of molecular materials. In this review, we describe recent advances and current directions in the assembly and applications of crystalline multicomponent micro-/nanostructures. Firstly, the design strategies for multicomponent systems based on molecular recognition and crystal engineering principles are introduced. Attention is then focused on the methods of fabrication of low-dimensional multicomponent micro-/nanostructures. Their new applications are also outlined. Finally, we briefly discuss perspectives for the further development of these molecular crystalline micro-/nanomaterials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Programming function into mechanical forms by directed assembly of silk bulk materials.

    Science.gov (United States)

    Marelli, Benedetto; Patel, Nereus; Duggan, Thomas; Perotto, Giovanni; Shirman, Elijah; Li, Chunmei; Kaplan, David L; Omenetto, Fiorenzo G

    2017-01-17

    We report simple, water-based fabrication methods based on protein self-assembly to generate 3D silk fibroin bulk materials that can be easily hybridized with water-soluble molecules to obtain multiple solid formats with predesigned functions. Controlling self-assembly leads to robust, machinable formats that exhibit thermoplastic behavior consenting material reshaping at the nanoscale, microscale, and macroscale. We illustrate the versatility of the approach by realizing demonstrator devices where large silk monoliths can be generated, polished, and reshaped into functional mechanical components that can be nanopatterned, embed optical function, heated on demand in response to infrared light, or can visualize mechanical failure through colorimetric chemistries embedded in the assembled (bulk) protein matrix. Finally, we show an enzyme-loaded solid mechanical part, illustrating the ability to incorporate biological function within the bulk material with possible utility for sustained release in robust, programmably shapeable mechanical formats.

  5. Assembling Appliances Standards from a Basket of Functions

    Energy Technology Data Exchange (ETDEWEB)

    Siderious, Hans-Paul; Meier, Alan

    2014-08-11

    Rapid innovation in product design challenges the current methodology for setting standards and labels, especially for electronics, software and networking. Major problems include defining the product, measuring its energy consumption, and choosing the appropriate metric and level for the standard. Most governments have tried to solve these problems by defining ever more specific product subcategories, along with their corresponding test methods and metrics. An alternative approach would treat each energy-using product as something that delivers a basket of functions. Then separate standards would be constructed for the individual functions that can be defined, tested, and evaluated. Case studies of thermostats, displays and network equipment are presented to illustrate the problems with the classical approach for setting standards and indicate the merits and drawbacks of the alternative. The functional approach appears best suited to products whose primary purpose is processing information and that have multiple functions.

  6. Fabrication of Multi-layered Shock Wave Tube for Hydrodynamic Instability Experiment

    Science.gov (United States)

    Zhu, Xiurong; Zhou, Bin; Xu, Xiang; Zhong, Yanhong; Du, Ai; Li, Yunong; Zhang, Zhihua; Shen, Jun; Wu, Guangming; Ni, Xingyuan

    2011-12-01

    In inertial confinement fusion (ICF) experiments, the growth of hydrodynamic instability occurred at the layer-to-layer interface of multilayer capsule is of the main importance to obtain ignition and high gain. In order to investigate and simulate the growth of hydrodynamic instability at "SG II"laser facility, we designed and fabricated a multi-layered shock wave tube (MSWT) in this article. The MSWT consisted of four functional units: planar polystyrene (CH) film, Al film with perturbation patterns, polyimide (PI) plastic and cylindrical carbonized-resorcinol-formaldehyde (CRF) aerogel, which were assembled into a cylindrical CH tube. The design, preparation process and assembly process of MSWT were detailed described. The assembly deviations and packaging material were discussed.

  7. Region-selective self-assembly of functionalized carbon allotropes from solution.

    Science.gov (United States)

    Wang, Zhenxing; Mohammadzadeh, Saeideh; Schmaltz, Thomas; Kirschner, Johannes; Khassanov, Artoem; Eigler, Siegfried; Mundloch, Udo; Backes, Claudia; Steinrück, Hans-Georg; Magerl, Andreas; Hauke, Frank; Hirsch, Andreas; Halik, Marcus

    2013-12-23

    Approaches for the selective self-assembly of functionalized carbon allotropes from solution are developed and validated for 0D-fullerenes, 1D-carbon nanotubes and 2D-graphene. By choosing the right molecular interaction of self-assembled monolayers (serving the surface) with the functionalization features of carbon materials, which provide the solubility but also serve the driving force for assembly, we demonstrate a region-selective and self-terminating assembly of the materials. Active layers of the carbon allotropes can be selectively deposited in the channel region of thin-film transistor (TFT) devices by this approach. As an example for a 0D system, molecules of C60 functionalized octadecylphosphonic acids are used to realize self-assembled monolayer field-effect transistors (SAMFETs) based on a selective molecular exchange reaction of stearic acid in the channel region. For noncovalently functionalized single-walled carbon nanotubes (SWCNTs) and graphene oxide (GO) flakes, the electrostatic Coulomb interactions between the functional groups of the carbon allotropes and the charged head groups of a SAM dielectric layer are utilized to implement the selective deposition.

  8. Functionally graded Ti-TiC multilayers: the effect of a graded profile on adhesion to substrate

    Energy Technology Data Exchange (ETDEWEB)

    Dahan, I.; Admon, U.; Sariel, J.; Yahav, B.; Amar, M.; Frage, N.; Dariel, M.P. [Ben-Gurion Univ. of the Negev, Beersheba (Israel). Dept. of Materials Engineering

    1999-10-01

    Thin Ti-TiC multilayer coatings on silicon substrates, when sputtered under bias, are in a state of compressive stress due to the incorporation of argon into the deposited layer. Under certain conditions, the compressive stresses lead to spontaneous delamination of the coating. The delamination process takes place by the propagation of a front of concentrated stress that produces local interface separation. The delamination process is characterized by outward buckling of the coating that propagates with relatively well-defined wavelengths of the order of 30 to 70 nm. Ultimately the delamination grows into a complex wrinkling pattern of the coating. The Ti-TiC graded multilayers were deposited with pre-designed composition profiles that affect the state of stress within the coating. The profile reflects the variation of the TiC/Ti ratio along the z-direction, perpendicular to the coating. Elementary composition profiles are characterized by one single parameter, k, that defines whether the TiC/Ti ratio is concave (for k<1) or convex (k>1) with respect to z. Graded multilayers with different values of k display delamination patterns that vary both by their kinetics and by the final morphology of the coating. In particular, graded multilayers with k{>=}3, display long term stability. The results illustrate the potential of graded coatings to reduce intrinsic stresses leading to delamination and failure. (orig.) 4 refs.

  9. Self-Assembly of Colloidal Nanocrystals: From Intricate Structures to Functional Materials.

    Science.gov (United States)

    Boles, Michael A; Engel, Michael; Talapin, Dmitri V

    2016-09-28

    Chemical methods developed over the past two decades enable preparation of colloidal nanocrystals with uniform size and shape. These Brownian objects readily order into superlattices. Recently, the range of accessible inorganic cores and tunable surface chemistries dramatically increased, expanding the set of nanocrystal arrangements experimentally attainable. In this review, we discuss efforts to create next-generation materials via bottom-up organization of nanocrystals with preprogrammed functionality and self-assembly instructions. This process is often driven by both interparticle interactions and the influence of the assembly environment. The introduction provides the reader with a practical overview of nanocrystal synthesis, self-assembly, and superlattice characterization. We then summarize the theory of nanocrystal interactions and examine fundamental principles governing nanocrystal self-assembly from hard and soft particle perspectives borrowed from the comparatively established fields of micrometer colloids and block copolymer assembly. We outline the extensive catalog of superlattices prepared to date using hydrocarbon-capped nanocrystals with spherical, polyhedral, rod, plate, and branched inorganic core shapes, as well as those obtained by mixing combinations thereof. We also provide an overview of structural defects in nanocrystal superlattices. We then explore the unique possibilities offered by leveraging nontraditional surface chemistries and assembly environments to control superlattice structure and produce nonbulk assemblies. We end with a discussion of the unique optical, magnetic, electronic, and catalytic properties of ordered nanocrystal superlattices, and the coming advances required to make use of this new class of solids.

  10. Non-random food-web assembly at habitat edges increases connectivity and functional redundancy.

    Science.gov (United States)

    Peralta, Guadalupe; Frost, Carol M; Didham, Raphael K; Rand, Tatyana A; Tylianakis, Jason M

    2017-04-01

    Habitat fragmentation dramatically alters the spatial configuration of landscapes, with the creation of artificial edges affecting community structure and dynamics. Despite this, it is not known how the different food webs in adjacent habitats assemble at their boundaries. Here we demonstrate that the composition and structure of herbivore-parasitoid food webs across edges between native and plantation forests are not randomly assembled from those of the adjacent communities. Rather, elevated proportions of abundant, interaction-generalist parasitoid species at habitat edges allowed considerable interaction rewiring, which led to higher linkage density and less modular networks, with higher parasitoid functional redundancy. This was despite high overlap in host composition between edges and interiors. We also provide testable hypotheses for how food webs may assemble between habitats with lower species overlap. In an increasingly fragmented world, non-random assembly of food webs at edges may increasingly affect community dynamics at the landscape level. © 2016 by the Ecological Society of America.

  11. Immunophilins and their function in photosystem II assembly

    Energy Technology Data Exchange (ETDEWEB)

    Sheng Luan

    2012-11-27

    In the past funding period, the following lines of experiments have been conducted: to identify the partner proteins for FKBP20-2; to identify the mechanism of CYP38 function; studies on other FKBPs in the thylakoid lumen; to identify the partner proteins for FKBP20-2 using yeast two hybrid and transgenic lines expressing HA-FKBP20-2; to identify the partner protein of CYP38; studies on other FKBPs in the chloroplast.

  12. The Prp19 complex directly functions in mitotic spindle assembly.

    Science.gov (United States)

    Hofmann, Jennifer C; Tegha-Dunghu, Justus; Dräger, Stefanie; Will, Cindy L; Lührmann, Reinhard; Gruss, Oliver J

    2013-01-01

    The conserved Prp19 (pre-RNA processing 19) complex is required for pre-mRNA splicing in eukaryotic nuclei. Recent RNAi screens indicated that knockdown of Prp19 complex subunits strongly delays cell proliferation. Here we show that knockdown of the smallest subunit, BCAS2/Spf27, destabilizes the entire complex and leads to specific mitotic defects in human cells. These could result from splicing failures in interphase or reflect a direct function of the complex in open mitosis. Using Xenopus extracts, in which cell cycle progression and spindle formation can be reconstituted in vitro, we tested Prp19 complex functions during a complete cell cycle and directly in open mitosis. Strikingly, immunodepletion of the complex either before or after interphase significantly reduces the number of intact spindles, and increases the percentage of spindles with lower microtubule density and impaired metaphase alignment of chromosomes. Our data identify the Prp19 complex as the first spliceosome subcomplex that directly contributes to mitosis in vertebrates independently of its function in interphase.

  13. The Prp19 complex directly functions in mitotic spindle assembly.

    Directory of Open Access Journals (Sweden)

    Jennifer C Hofmann

    Full Text Available The conserved Prp19 (pre-RNA processing 19 complex is required for pre-mRNA splicing in eukaryotic nuclei. Recent RNAi screens indicated that knockdown of Prp19 complex subunits strongly delays cell proliferation. Here we show that knockdown of the smallest subunit, BCAS2/Spf27, destabilizes the entire complex and leads to specific mitotic defects in human cells. These could result from splicing failures in interphase or reflect a direct function of the complex in open mitosis. Using Xenopus extracts, in which cell cycle progression and spindle formation can be reconstituted in vitro, we tested Prp19 complex functions during a complete cell cycle and directly in open mitosis. Strikingly, immunodepletion of the complex either before or after interphase significantly reduces the number of intact spindles, and increases the percentage of spindles with lower microtubule density and impaired metaphase alignment of chromosomes. Our data identify the Prp19 complex as the first spliceosome subcomplex that directly contributes to mitosis in vertebrates independently of its function in interphase.

  14. Flame-Retardant Paper from Wood Fibers Functionalized via Layer-by-Layer Assembly.

    Science.gov (United States)

    Köklükaya, Oruç; Carosio, Federico; Grunlan, Jaime C; Wågberg, Lars

    2015-10-28

    The highly flammable character of cellulose-rich fibers from wood limits their use in some advanced materials. To suppress the flammability and introduce flame-retardant properties to individual pulp fibers, we deposited nanometer thin films consisting of cationic chitosan (CH) and anionic poly(vinylphosphonic acid) (PVPA) on fibers using the layer-by-layer (LbL) technique. The buildup of the multilayer film was investigated in the presence and absence of salt (NaCl) using model cellulose surfaces and a quartz crystal microbalance technique. Fibers were then treated with the same strategy, and the treated fibers were used to prepare paper sheets. A horizontal flame test (HFT) and cone calorimetry were conducted to evaluate the combustion behavior of paper sheets as a function of the number of bilayers deposited on fibers. In HFT, paper made of fibers coated with 20 CH/PVPA bilayers (BL), self-extinguished the flame, while uncoated fibers were completely consumed. Scanning electron microscopy of charred paper after HFT revealed that a thin shell of the charred polymeric multilayer remained after the cellulose fibers had been completely oxidized. Cone calorimetry demonstrated that the phosphorus-containing thin films (20 BL is ∼25 nm) reduced the peak heat release rate by 49%. This study identifies a unique and highly effective way to impart flame-retardant characteristic to pulp fibers and the papers made from these fibers.

  15. Photoligation of self-assembled DNA constructs containing anthracene-functionalized 2'-amino-LNA monomers

    DEFF Research Database (Denmark)

    Pasternak, Karol; Pasternak, Anna; Gupta, Pankaj

    2011-01-01

    Efficient synthesis of a novel anthracene-functionalized 2'-amino-LNA phosphoramidite derivative is described together with its incorporation into oligodeoxynucleotides. Two DNA strands with the novel 2'-N-anthracenylmethyl-2'-amino-LNA monomers can be effectively cross-linked by photoligation...... at 366nm in various types of DNA constructs. Successful application of three differently functionalized 2'-amino-LNA monomers in self-assembled higher ordered structures for simultaneous cross-linking and monitoring of assembly formation is furthermore demonstrated....

  16. Structural insights shed light onto septin assemblies and function.

    Science.gov (United States)

    Barral, Yves; Kinoshita, Makoto

    2008-02-01

    While the original septin mutants were identified more than 30 years ago for their role in cytokinesis [Hartwell, LH: Genetic control of the cell division cycle in yeast. IV. Genes controlling bud emergence and cytokinesis. Exp Cell Res 1971, 69: 265-276], the architecture of septin complexes and higher order structures has remained a mystery up until very recently. Over the last few months a number of converging approaches have suddenly provided a wealth of structural information about the different levels of septin organization. Here, we review these advancements and highlight their functional consequences.

  17. Sustained delivery of VEGF from designer self-assembling peptides improves cardiac function after myocardial infarction

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Hai-dong [Department of Anatomy, School of Basic Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai 201203 (China); Cui, Guo-hong; Yang, Jia-jun [Department of Neurology, Shanghai No. 6 People' s Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200233 (China); Wang, Cun [Institutes of Biomedical Sciences, Fudan University, Shanghai 200032 (China); Zhu, Jing; Zhang, Li-sheng; Jiang, Jun [Department of Anatomy, School of Basic Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai 201203 (China); Shao, Shui-jin, E-mail: shaoshuijin@163.com [Department of Anatomy, School of Basic Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai 201203 (China)

    2012-07-20

    Highlights: Black-Right-Pointing-Pointer The designer peptide LRKKLGKA could self-assemble into nanofibers. Black-Right-Pointing-Pointer Injection of LRKKLGKA peptides could promote the sustained delivery of VEGF. Black-Right-Pointing-Pointer Injection of VEGF with LRKKLGKA peptides lead to sufficient angiogenesis. Black-Right-Pointing-Pointer Injection of VEGF with LRKKLGKA peptides improves heart function. -- Abstract: Poor vascularization and insufficient oxygen supply are detrimental to the survival of residual cardiomyocytes or transplanted stem cells after myocardial infarction. To prolong and slow the release of angiogenic factors, which stimulate both angiogenesis and vasculogenesis, we constructed a novel self-assembling peptide by attaching the heparin-binding domain sequence LRKKLGKA to the self-assembling peptide RADA16. This designer self-assembling peptide self-assembled into nanofiber scaffolds under physiological conditions, as observed by atomic force microscopy. The injection of designer self-assembling peptides can efficiently provide the sustained delivery of VEGF for at least 1 month. At 4 weeks after transplantation, cardiac function was improved, and scar size and collagen deposition were markedly reduced in the group receiving VEGF with the LRKKLGKA scaffolds compared with groups receiving VEGF alone, LRKKLGKA scaffolds alone or VEGF with RADA16 scaffolds. The microvessel density in the VEGF with LRKKLGKA group was higher than that in the VEGF with RADA16 group. TUNEL and cleaved caspase-3 expression assays showed that the transplantation of VEGF with LRKKLGKA enhanced cell survival in the infarcted heart. These results present the tailor-made peptide scaffolds as a new generation of sustained-release biomimetic biomaterials and suggest that the use of angiogenic factors along with designer self-assembling peptides can lead to myocardial protection, sufficient angiogenesis, and improvement in cardiac function.

  18. Functional Profiling of Unfamiliar Microbial Communities Using a Validated De Novo Assembly Metatranscriptome Pipeline.

    Directory of Open Access Journals (Sweden)

    Mark Davids

    Full Text Available Metatranscriptomic landscapes can provide insights in functional relationships within natural microbial communities. Analysis of complex metatranscriptome datasets of these communities poses a considerable bioinformatic challenge since they are non-restricted with a varying number of participating strains and species. For RNA-Seq data a standard approach is to align the generated reads to a set of closely related reference genomes. This only works well for microbial communities for which a near complete catalogue of reference genomes is available at a small evolutionary distance. In this study, we focus on the design of a validated de novo metatranscriptome assembly pipeline for single-end Illumina RNA-Seq data to obtain functional and taxonomic profiles of murine microbial communities.The here developed de novo assembly metatranscriptome pipeline combined rRNA removal, IDBA-UD assembler, functional annotation and taxonomic classification. Different assemblers were tested and validated using RNA-Seq data from an in silico generated mock community and in vivo RNA-Seq data from a restricted microbial community taken from a mouse model colonized with Altered Schaedler Flora (ASF. Precision and recall of resulting gene expression, functional and taxonomic profiles were compared to those obtained with a standard alignment method. The validated pipeline was subsequently used to generate expression profiles from non-restricted cecal communities of four C57BL/6J mice fed on a high-fat high-protein diet spiked with an RNA-Seq data set from a well-characterized human sample. The spike in control was used to estimate precision and recall at assembly, functional and taxonomic level of non-restricted communities.A generic de novo assembly pipeline for metatranscriptome data analysis was designed for microbial ecosystems, which can be applied for microbial metatranscriptome analysis in any chosen niche.

  19. Architecture, Function, and Assembly of the Mouse Visual System.

    Science.gov (United States)

    Seabrook, Tania A; Burbridge, Timothy J; Crair, Michael C; Huberman, Andrew D

    2017-07-25

    Vision is the sense humans rely on most to navigate the world, make decisions, and perform complex tasks. Understanding how humans see thus represents one of the most fundamental and important goals of neuroscience. The use of the mouse as a model for parsing how vision works at a fundamental level started approximately a decade ago, ushered in by the mouse's convenient size, relatively low cost, and, above all, amenability to genetic perturbations. In the course of that effort, a large cadre of new and powerful tools for in vivo labeling, monitoring, and manipulation of neurons were applied to this species. As a consequence, a significant body of work now exists on the architecture, function, and development of mouse central visual pathways. Excitingly, much of that work includes causal testing of the role of specific cell types and circuits in visual perception and behavior-something rare to find in studies of the visual system of other species. Indeed, one could argue that more information is now available about the mouse visual system than any other sensory system, in any species, including humans. As such, the mouse visual system has become a platform for multilevel analysis of the mammalian central nervous system generally. Here we review the mouse visual system structure, function, and development literature and comment on the similarities and differences between the visual system of this and other model species. We also make it a point to highlight the aspects of mouse visual circuitry that remain opaque and that are in need of additional experimentation to enrich our understanding of how vision works on a broad scale.

  20. Final Closeout report for grant FG36-08GO18018, titled: Functional Multi-Layer Solution Processable Polymer Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Adam J. Moule

    2012-05-01

    The original objectives were: (1) Develop a method to deposit multiple conjugated polymer film layers and avoid the problem of dissolution from mutually solubility; (2) Use this deposition method to develop multi-layer polymer based solar cells with layers that are function specific; (3) characterize these layers and devices; (4) develop electrical and optical models that describe and predict the properties of the multi-layers; and (5) Ultimate efficiency goals are {approx}6.75% with J{sub sc} = 12 mA/cm{sup 2}, FF = 0.75, and V{sub oc} = 0.75. The question of whether photovoltaic (PV) cells will ever be able to replace fossil fuels as the main provider of electrical power is not just a question of device efficiency; it is a question of how much power can be provided for what price. It has been well documented that PV devices at 10% power efficiency can provide for all of the world's power needs without covering too much of the earth's surface. Assuming desert like cloud coverage, an area equivalent to the land area of Texas would have to be covered. However, it has also been shown that using the current state-of-the-art silicon devices, the price-per-Watt will never be low enough to be economically feasible for large-scale development. Solution-processable PV devices based on polymers are a very attractive alternative to traditional Silicon PV because this technology is much lower in materials cost and in environmentally toxic waste production. Solution-based polymers can be rapidly deposited using printing technologies and are compatible with light-weight flexible substrates that can increase the range of available PV applications. In the past ten years, the efficiency of polymer based PV devices has increased from {approx}1% to over 10%. The highest efficiency organic solar cells are based upon a single layer than consists of a mixture of donor and acceptor moieties. This one layer has multiple optical and electrical functions, so the design of a

  1. Filovirus proteins for antiviral drug discovery: Structure/function of proteins involved in assembly and budding.

    Science.gov (United States)

    Martin, Baptiste; Reynard, Olivier; Volchkov, Viktor; Decroly, Etienne

    2018-02-01

    There are no approved medications for the treatment of Marburg or Ebola virus infection. In two previous articles (Martin et al., 2016, Martin et al., 2017), we reviewed surface glycoprotein and replication proteins structure/function relationship to decipher the molecular mechanisms of filovirus life cycle and identify antiviral strategies. In the present article, we recapitulate knowledge about the viral proteins involved in filovirus assembly and budding. First we describe the structural data available for viral proteins associated with virus assembly and virion egress and then, we integrate the structural features of these proteins in the functional context of the viral replication cycle. Finally, we summarize recent advances in the development of innovative antiviral strategies to target filovirus assembly and egress. The development of such prophylactic or post-exposure treatments could help controlling future filovirus outbreaks. Copyright © 2018 Elsevier B.V. All rights reserved.

  2. Self-assembly of diphenylalanine backbone homologues and their combination with functionalized carbon nanotubes.

    Science.gov (United States)

    Dinesh, Bhimareddy; Squillaci, Marco A; Ménard-Moyon, Cécilia; Samorì, Paolo; Bianco, Alberto

    2015-10-14

    The integration of carbon nanotubes (CNTs) into organized nanostructures is of great interest for applications in materials science and biomedicine. In this work we studied the self-assembly of β and γ homologues of diphenylalanine peptides under different solvent and pH conditions. We aimed to investigate the role of peptide backbone in tuning the formation of different types of nanostructures alone or in combination with carbon nanotubes. In spite of having the same side chain, β and γ peptides formed distinctively different nanofibers, a clear indication of the role played by the backbone homologation on the self-assembly. The variation of the pH allowed to transform the nanofibers into spherical structures. Moreover, the co-assembly of β and γ peptides with carbon nanotubes covalently functionalized with the same peptide generated unique dendritic assemblies. This comparative study on self-assembly using diphenylalanine backbone homologues and of the co-assembly with CNT covalent conjugates is the first example exploring the capacity of β and γ peptides to adopt precise nanostructures, particularly in combination with carbon nanotubes. The dendritic organization obtained by mixing carbon nanotubes and peptides might find interesting applications in tissue engineering and neuronal interfacing.

  3. Integrative self-assembly of functional hybrid nanoconstructs by inorganic wrapping of single biomolecules, biomolecule arrays and organic supramolecular assemblies

    Science.gov (United States)

    Patil, Avinash J.; Li, Mei; Mann, Stephen

    2013-07-01

    Synthesis of functional hybrid nanoscale objects has been a core focus of the rapidly progressing field of nanomaterials science. In particular, there has been significant interest in the integration of evolutionally optimized biological systems such as proteins, DNA, virus particles and cells with functional inorganic building blocks to construct mesoscopic architectures and nanostructured materials. However, in many cases the fragile nature of the biomolecules seriously constrains their potential applications. As a consequence, there is an on-going quest for the development of novel strategies to modulate the thermal and chemical stabilities, and performance of biomolecules under adverse conditions. This feature article highlights new methods of ``inorganic molecular wrapping'' of single or multiple protein molecules, individual double-stranded DNA helices, lipid bilayer vesicles and self-assembled organic dye superstructures using inorganic building blocks to produce bio-inorganic nanoconstructs with core-shell type structures. We show that spatial isolation of the functional biological nanostructures as ``armour-plated'' enzyme molecules or polynucleotide strands not only maintains their intact structure and biochemical properties, but also enables the fabrication of novel hybrid nanomaterials for potential applications in diverse areas of bionanotechnology.

  4. Nanostructured functional hybrid materials via self-assembly of brush block copolymers

    Science.gov (United States)

    Song, Dong-Po; Gai, Yue; Yavitt, Benjamin; Watkins, James

    The self-assembly of well-ordered nanoparticle (NP) / block copolymer (BCP) composites enables precise control over the spatial distribution of NP arrays, providing a simple route to the low-cost ``bottom-up'' fabrication of hybrid materials with enhanced mechanical, optical and electric properties. Here we summarize the fabrication of nanocomposites via the self-assembly of brush BCPs (BBCPs). In comparison to conventional materials based on linear BCPs, the BBCP hybrids exhibit many attractive features, including rapid supramolecular self-assembly (100 nm), and high loading of functional additives (>70 wt%). Both the self-assembled structures and the compositions of the nanocomposites can be widely tuned for applications such as photonic crystals or coatings, nonlinear optics, and metamaterials. In addition, BBCPs were employed as templates for the mesoporous hybrid materials that have large mesopores (up to 40 nm) and high loadings of functional NPs (up to 50 wt%). Simple solutionbased processing and rapid self-assembly of brush BCP nanocomposites are promising for roll-to-roll manufacturing of low-cost and flexible devices. This work was supported by NSF Center for Hierarchical Manufacturing at the University of Massachusetts, Amherst.

  5. Self-Assembled Functional Organic Monolayers on Oxide-Free Copper

    NARCIS (Netherlands)

    Caipa Campos, M.A.; Trilling, A.K.; Yang, M.; Giesbers, M.; Beekwilder, J.; Paulusse, J.M.J.; Zuilhof, H.

    2011-01-01

    The preparation and characterization of self-assembled monolayers on copper with n-alkyl and functional thiols was investigated. Well-ordered monolayers were obtained, while the copper remained oxide-free. Direct attachment of N-succinimidyl mercaptoundecanoate (NHS-MUA) onto the copper surface

  6. Functional materials based on self-assembled comb-shaped supramolecules

    NARCIS (Netherlands)

    ten Brinke, G; Ikkala, O; KorugicKarasz, LS; MacKnight, WJ; Martuscelli, E

    2005-01-01

    In this paper we will review the main features of our approach to create functional materials using self-assembly of hydrogenbonded comb-shaped supramolecules. Typically, the supramolecules consist of homopolymers or diblock copolymers, where short chain amphiphiles are hydrogenbonded to the

  7. Endgroups of Functionalized Siloxane Oligomers Direct Block Copolymeric or Liquid Crystalline Self-Assembly Behavior

    NARCIS (Netherlands)

    Zha, R. Helen; De Waal, Bas; Lutz, Martin|info:eu-repo/dai/nl/304828971; Teunissen, Abraham J.p.; Meijer, E. W.

    2016-01-01

    Monodisperse oligodimethylsiloxanes end-functionalized with the hydrogen-bonding ureidopyrimidinone (UPy) motif undergo phase separation between their aromatic end groups and dimethylsiloxane midblocks to form ordered nanostructures with domain spacings of <5 nm. The self-assembly behavior of these

  8. The assembly of ecological communities inferred from taxonomic and functional composition

    Science.gov (United States)

    Eric R. Sokol; E.F. Benfield; Lisa K. Belden; H. Maurice. Valett

    2011-01-01

    Among-site variation in metacommunities (beta diversity) is typically correlated with the distance separating the sites (spatial lag). This distance decay in similarity pattern has been linked to both niche-based and dispersal-based community assembly hypotheses. Here we show that beta diversity patterns in community composition, when supplemented with functional-trait...

  9. Electronic functionalization of the surface of organic semiconductors with self-assembled monolayers

    Science.gov (United States)

    Calhoun, M. F.; Sanchez, J.; Olaya, D.; Gershenson, M. E.; Podzorov, V.

    2008-01-01

    Self-assembled monolayers (SAMs) are widely used in a variety of emerging applications for surface modification of metals and oxides. Here, we demonstrate a new type of molecular self-assembly: the growth of organosilane SAMs at the surface of organic semiconductors. Remarkably, SAM growth results in a pronounced increase of the surface conductivity of organic materials, which can be very large for SAMs with a strong electron-withdrawing ability. For example, the conductivity induced by perfluorinated alkyl silanes in organic molecular crystals approaches 10-5S per square, two orders of magnitude greater than the maximum conductivity typically achieved in organic field-effect transistors. The observed large electronic effect opens new opportunities for nanoscale surface functionalization of organic semiconductors with molecular self-assembly. In particular, SAM-induced conductivity shows sensitivity to different molecular species present in the environment, which makes this system very attractive for chemical sensing applications.

  10. Electrical-pulse-induced resistivity modulation in Pt/TiO2-δ/Pt multilayer device related to nanoionics-based neuromorphic function

    Science.gov (United States)

    Kawamura, Kinya; Tsuchiya, Takashi; Takayanagi, Makoto; Terabe, Kazuya; Higuchi, Tohru

    2017-06-01

    Resistivity modulation behavior in Pt/TiO2-δ/Pt multilayer devices was investigated in terms of nanoionics-based neuromorphic function. The current relaxation behavior, which corresponds to short-term and long-term memorization in neuromorphic function, was analyzed using electrical pulses. In contrast to the huge difference in ionic conductivity for bulk crystal materials of TiO2-δ and WO3, the difference in the relaxation behavior was small. Rutherford backscattering spectrometry and hydrogen forward scattering spectrometry revealed that the TiO2-δ thin film contained 5.6 at. % of protons. This indicates that the neuromorphic function in TiO2-δ-based devices is caused by extrinsic proton transport, presumably through the grain boundary.

  11. Self-assembling functionalized nanopeptides for immediate hemostasis and accelerative liver tissue regeneration

    Science.gov (United States)

    Cheng, Tzu-Yun; Wu, Hsi-Chin; Huang, Ming-Yuan; Chang, Wen-Han; Lee, Chao-Hsiung; Wang, Tzu-Wei

    2013-03-01

    Traumatic injury or surgery may trigger extensive bleeding. However, conventional hemostatic methods have limited efficacy and may cause surrounding tissue damage. In this study, we use self-assembling peptides (SAPs) and specifically extend fragments of functional motifs derived from fibronectin and laminin to evaluate the capability of these functionalized SAPs in the effect of hemostasis and liver tissue regeneration. From the results, these peptides can self-assemble into nanofibrous network structure and gelate into hydrogel with pH adjustment. In animal studies, the efficacy of hemostasis is achieved immediately within seconds in a rat liver model. The histological analyses by hematoxylin-eosin stain and immunohistochemistry reveal that SAPs with these functionalized motifs significantly enhance liver tissue regeneration. In brief, these SAPs may have potential as pharmacological tools to extensively advance clinical therapeutic applications in hemostasis and tissue regeneration in the field of regenerative medicine.Traumatic injury or surgery may trigger extensive bleeding. However, conventional hemostatic methods have limited efficacy and may cause surrounding tissue damage. In this study, we use self-assembling peptides (SAPs) and specifically extend fragments of functional motifs derived from fibronectin and laminin to evaluate the capability of these functionalized SAPs in the effect of hemostasis and liver tissue regeneration. From the results, these peptides can self-assemble into nanofibrous network structure and gelate into hydrogel with pH adjustment. In animal studies, the efficacy of hemostasis is achieved immediately within seconds in a rat liver model. The histological analyses by hematoxylin-eosin stain and immunohistochemistry reveal that SAPs with these functionalized motifs significantly enhance liver tissue regeneration. In brief, these SAPs may have potential as pharmacological tools to extensively advance clinical therapeutic applications

  12. Functional metagenomics of spacecraft assembly cleanrooms: Presence of virulence factors associated with human pathogens.

    Directory of Open Access Journals (Sweden)

    Mina Bashir

    2016-09-01

    Full Text Available Strict planetary protection practices are implemented during spacecraft assembly to prevent inadvertent transfer of earth microorganisms to other planetary bodies. Therefore, spacecraft are assembled in cleanrooms, which undergo strict cleaning and decontamination procedures to reduce total microbial bioburden. We wanted to evaluate if these practices selectively favor survival and growth of hardy microorganisms, such as pathogens. Three geographically distinct cleanrooms were sampled during the assembly of three NASA spacecraft: The Lockheed Martin Aeronautics’ Multiple Testing Facility during DAWN, the Kennedy Space Center’s Payload Hazardous Servicing Facility (KSC-PHSF during Phoenix, and the Jet Propulsion Laboratory’s Spacecraft Assembly Facility during Mars Science Laboratory. Sample sets were collected from the KSC-PHSF cleanroom at three time points: before arrival of the Phoenix spacecraft, during the assembly and testing of the Phoenix spacecraft, and after removal of the spacecraft from the KSC-PHSF facility. All samples were subjected to metagenomic shotgun sequencing on an Illumina HiSeq 2500 platform. Strict decontamination procedures had a greater impact on microbial communities than sampling location Samples collected during spacecraft assembly were dominated by Acinetobacter spp. We found pathogens and potential virulence factors, which determine pathogenicity in all the samples tested during this study. Though the relative abundance of pathogens was lowest during the Phoenix assembly, potential virulence factors were higher during assembly compared to before and after assembly, indicating a survival advantage. Decreased phylogenetic and pathogenic diversity indicates that decontamination and preventative measures were effective against the majority of microorganisms and well implemented, however, pathogen abundance still increased over time. Four potential pathogens, Acinetobacter baumannii, Acinetobacter lwoffii

  13. Ligand functionality as a versatile tool to control the assembly behavior of preformed titania nanocrystals.

    Science.gov (United States)

    Polleux, Julien; Pinna, Nicola; Antonietti, Markus; Hess, Christian; Wild, Ute; Schlögl, Robert; Niederberger, Markus

    2005-06-06

    Nanoparticle powders composed of surface-functionalized anatase crystals with diameters of about 3 nm self-organize into different structures upon redispersion in water. The assembly is directed by a small amount of a low-molecular-weight functional ligand (the "assembler") adsorbed on the surface of the nanoparticles. The ligand functionality determines the anisotropy of the resulting structures. Multidentate ligands, such as trizma ((HOCH(2))(3)CNH(2)) and serinol ((HOCH(2))(2)CNH(2)), with a chargeable terminal group preferentially induce the formation of anisotropic nanostructures several hundreds of nanometers in total length, whereas all the other investigated ligands (ethanolamine H(2)N(CH(2))(2)OH, glycine hydroxamate H(2)NCH(2)CONHOH, dopamine (OH)(2)C(6)H(3)(CH(2))(2)NH(3)Cl, tris (HOCH(2))(3)CCH(3)) mainly lead to uncontrolled agglomeration. Experimental data suggests that the anisotropic assembly is a consequence of the water-promoted desorption of the organic ligands from the {001} faces of the crystalline building blocks together with the dissociative adsorption of water on these crystal faces. Both processes induce the preferred attachment of the titania nanoparticles along the [001] direction. The use of polydentate and charged ligands to functionalize the surface of nanoparticles thus provides a versatile tool to control their arrangement on the nanoscale.

  14. Self-assembly behaviors of molecular designer functional RADA16-I peptides: influence of motifs, pH, and assembly time.

    Science.gov (United States)

    Sun, Yuqiao; Zhang, Yongnu; Tian, Lingling; Zhao, Yuyuan; Wu, Dongni; Xue, Wei; Ramakrishna, Seeram; Wu, Wutian; He, Liumin

    2016-12-09

    In the current study, we present three designer self-assembling peptides (SAPs) by appending RADA 16-I with epitopes IKVAV, RGD, and YIGSR, which have different net charges and amphiphilic properties at neutral pH. The self-assembly of the designer SAPs is intensively investigated as a function of pH, canion type, and assembly time. The morphologies of the designer SAPs were studied by atomic force microscope. The secondary structure was investigated by circular dichroism. The dynamic viscoelasticity of designer SAP solutions was examined during titration with different alkaline reagents. Our study indicated that both electrostatic and hydrophilic/hydrophobic interactions of the motifs exhibited influences on the self-assembly, consequentially affecting the fiber morphologies and rheological properties. Moreover, NaOH induced a quicker assembly/reassembly of the designer SAPs than Tris because of its strong ionic strength. Therefore, our study gained comprehensive insight into the self-assembling mechanism as references for developing RADA 16-I-based functional SAPs.

  15. Building functional groups of marine benthic macroinvertebrates on the basis of general community assembly mechanisms

    Science.gov (United States)

    Alexandridis, Nikolaos; Bacher, Cédric; Desroy, Nicolas; Jean, Fred

    2017-03-01

    The accurate reproduction of the spatial and temporal dynamics of marine benthic biodiversity requires the development of mechanistic models, based on the processes that shape macroinvertebrate communities. The modelled entities should, accordingly, be able to adequately represent the many functional roles that are performed by benthic organisms. With this goal in mind, we applied the emergent group hypothesis (EGH), which assumes functional equivalence within and functional divergence between groups of species. The first step of the grouping involved the selection of 14 biological traits that describe the role of benthic macroinvertebrates in 7 important community assembly mechanisms. A matrix of trait values for the 240 species that occurred in the Rance estuary (Brittany, France) in 1995 formed the basis for a hierarchical classification that generated 20 functional groups, each with its own trait values. The functional groups were first evaluated based on their ability to represent observed patterns of biodiversity. The two main assumptions of the EGH were then tested, by assessing the preservation of niche attributes among the groups and the neutrality of functional differences within them. The generally positive results give us confidence in the ability of the grouping to recreate functional diversity in the Rance estuary. A first look at the emergent groups provides insights into the potential role of community assembly mechanisms in shaping biodiversity patterns. Our next steps include the derivation of general rules of interaction and their incorporation, along with the functional groups, into mechanistic models of benthic biodiversity.

  16. Architecture and Assembly of the Bacillus subtilis Spore Coat

    Science.gov (United States)

    Plomp, Marco; Carroll, Alicia Monroe; Setlow, Peter; Malkin, Alexander J.

    2014-01-01

    Bacillus spores are encased in a multilayer, proteinaceous self-assembled coat structure that assists in protecting the bacterial genome from stresses and consists of at least 70 proteins. The elucidation of Bacillus spore coat assembly, architecture, and function is critical to determining mechanisms of spore pathogenesis, environmental resistance, immune response, and physicochemical properties. Recently, genetic, biochemical and microscopy methods have provided new insight into spore coat architecture, assembly, structure and function. However, detailed spore coat architecture and assembly, comprehensive understanding of the proteomic composition of coat layers, and specific roles of coat proteins in coat assembly and their precise localization within the coat remain in question. In this study, atomic force microscopy was used to probe the coat structure of Bacillus subtilis wild type and cotA, cotB, safA, cotH, cotO, cotE, gerE, and cotE gerE spores. This approach provided high-resolution visualization of the various spore coat structures, new insight into the function of specific coat proteins, and enabled the development of a detailed model of spore coat architecture. This model is consistent with a recently reported four-layer coat assembly and further adds several coat layers not reported previously. The coat is organized starting from the outside into an outermost amorphous (crust) layer, a rodlet layer, a honeycomb layer, a fibrous layer, a layer of “nanodot” particles, a multilayer assembly, and finally the undercoat/basement layer. We propose that the assembly of the previously unreported fibrous layer, which we link to the darkly stained outer coat seen by electron microscopy, and the nanodot layer are cotH- and cotE- dependent and cotE-specific respectively. We further propose that the inner coat multilayer structure is crystalline with its apparent two-dimensional (2D) nuclei being the first example of a non-mineral 2D nucleation crystallization

  17. Architecture and assembly of the Bacillus subtilis spore coat.

    Science.gov (United States)

    Plomp, Marco; Carroll, Alicia Monroe; Setlow, Peter; Malkin, Alexander J

    2014-01-01

    Bacillus spores are encased in a multilayer, proteinaceous self-assembled coat structure that assists in protecting the bacterial genome from stresses and consists of at least 70 proteins. The elucidation of Bacillus spore coat assembly, architecture, and function is critical to determining mechanisms of spore pathogenesis, environmental resistance, immune response, and physicochemical properties. Recently, genetic, biochemical and microscopy methods have provided new insight into spore coat architecture, assembly, structure and function. However, detailed spore coat architecture and assembly, comprehensive understanding of the proteomic composition of coat layers, and specific roles of coat proteins in coat assembly and their precise localization within the coat remain in question. In this study, atomic force microscopy was used to probe the coat structure of Bacillus subtilis wild type and cotA, cotB, safA, cotH, cotO, cotE, gerE, and cotE gerE spores. This approach provided high-resolution visualization of the various spore coat structures, new insight into the function of specific coat proteins, and enabled the development of a detailed model of spore coat architecture. This model is consistent with a recently reported four-layer coat assembly and further adds several coat layers not reported previously. The coat is organized starting from the outside into an outermost amorphous (crust) layer, a rodlet layer, a honeycomb layer, a fibrous layer, a layer of "nanodot" particles, a multilayer assembly, and finally the undercoat/basement layer. We propose that the assembly of the previously unreported fibrous layer, which we link to the darkly stained outer coat seen by electron microscopy, and the nanodot layer are cotH- and cotE- dependent and cotE-specific respectively. We further propose that the inner coat multilayer structure is crystalline with its apparent two-dimensional (2D) nuclei being the first example of a non-mineral 2D nucleation crystallization

  18. Surface modification of titanium substrates with silver nanoparticles embedded sulfhydrylated chitosan/gelatin polyelectrolyte multilayer films for antibacterial application.

    Science.gov (United States)

    Li, Wen; Xu, Dawei; Hu, Yan; Cai, Kaiyong; Lin, Yingcheng

    2014-06-01

    To develop Ti implants with potent antibacterial activity, a novel "sandwich-type" structure of sulfhydrylated chitosan (Chi-SH)/gelatin (Gel) polyelectrolyte multilayer films embedding silver (Ag) nanoparticles was coated onto titanium substrate using a spin-assisted layer-by-layer assembly technique. Ag ions would be enriched in the polyelectrolyte multilayer films via the specific interactions between Ag ions and -HS groups in Chi-HS, thus leading to the formation of Ag nanoparticles in situ by photo-catalytic reaction (ultraviolet irradiation). Contact angle measurement and field emission scanning electron microscopy equipped with energy dispersive X-ray spectroscopy were employed to monitor the construction of Ag-containing multilayer on titanium surface, respectively. The functional multilayered films on titanium substrate [Ti/PEI/(Gel/Chi-SH/Ag) n /Gel] could efficiently inhibit the growth and activity of Bacillus subtitles and Escherichia coli onto titanium surface. Moreover, studies in vitro confirmed that Ti substrates coating with functional multilayer films remained the biological functions of osteoblasts, which was reflected by cell morphology, cell viability and ALP activity measurements. This study provides a simple, versatile and generalized methodology to design functional titanium implants with good cyto-compatibility and antibacterial activity for potential clinical applications.

  19. Self-assembly strategies for the synthesis of functional nanostructured materials

    Science.gov (United States)

    Perego, M.; Seguini, G.

    2016-06-01

    Self-assembly is the autonomous organization of components into patterns or structures without human intervention. This is the approach followed by nature to generate living cells and represents one of the practical strategies to fabricate ensembles of nanostructures. In static self-assembly the formation of ordered structures could require energy but once formed the structures are stable. The introduction of additional regular features in the environment could be used to template the self-assembly guiding the organization of the components and determining the final structure they form. In this regard self-assembly of block copolymers represents a potent platform for fundamental studies at the nanoscale and for application-driven investigation as a tool to fabricate functional nanostructured materials. Block copolymers can hierarchically assemble into chemically distinct domains with size and periodicity on the order of 10nm or below, offering a potentially inexpensive route to generate large-area nanostructured materials. The final structure characteristics of these materials are dictated by the properties of the elementary block copolymers, like chain length, volume fraction or degree of block incompatibility. Modern synthetic chemistry offers the possibility to design these macromolecules with very specific length scales and geometries, directly embodying in the block copolymers the code that drives their self- assembling process. The understanding of the kinetics and thermodynamics of the block copolymer self-assembly process in the bulk phase as well as in thin films represents a fundamental prerequisite toward the exploitation of these materials. Incorporating block copolymer into device fabrication procedures or directly into devices, as active elements, will lead to the development of a new generation of devices fabricated using the fundamental law of nature to our advantage in order to minimize cost and power consumption in the fabrication process

  20. Facile functionalization and assembly of live cells with microcontact-printed polymeric biomaterials.

    Science.gov (United States)

    Wang, Zhibin; Xia, Junfei; Yan, Yuanwei; Tsai, Ang-Chen; Li, Yan; Ma, Teng; Guan, Jingjiao

    2015-01-01

    The functionalization and assembly of live cells with microfabricated polymeric biomaterials have attracted considerable interest in recent years, but the conventional methods suffer from high cost, high complexity, long processing time or inadequate capability. The present study reports on the development of a novel method for functionalizing and assembling live cells by integrating microcontact printing of polymeric biomaterials with a temperature-sensitive sacrificial layer prepared by spin-coating. This method has been used not only to functionalize live cells with microscopic polyelectrolyte and thermoplastic structures of various sizes and shapes, but also to assemble the cells into macroscopic stripes and sheets. The method is applicable to multiple types of cells, including human leukemic cells, mouse embryonic stem cells and human mesenchymal stem cells in the forms of single cells and cell aggregates. In addition, the microcontact-printed structures can be prepared using biodegradable and biocompatible polyelectrolytes and thermoplastic. The unique combination of low cost, ease of use and high versatility renders this method potentially useful for diverse biomedical applications, including drug delivery, cell tracking and tissue engineering. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  1. Light Irradiation as Key to Shape and Function of Nano-Assemblies in Solution

    Science.gov (United States)

    Groehn, Franziska

    Developing strategies to exploit solar energy become more and more important. Inspired by natural systems it is highly promising to self-assemble functional species into effective tailored supramolecular units. Here we report self-assembled polymer structures in solution, taking advantage of optical properties of hybrid structures and light responsiveness. A new type of photocatalytically active self-assembled polymer structure in aqueous solution consists of supramolecular nano-objects obtained from macroions and multivalent inorganic ``counterions'' such as nanoparticles or clusters. These can exhibit expressed selectivity or even allow catalytic reactions in solution that are not possible with the building blocks only. Further, polyelectrolyte-porphyrin nanoscale assemblies exhibit tunable optical properties including strong fluorescence and an up to 20-fold higher photocatalytic activity than without polymeric template. A different approach is to transfer light energy into mechanical energy. Here, light energy is converted into nanoscale shape changes. This route for the conversion of light is highly promising for applications in drug delivery, nanosensors and solar energy conversion. Membership of DPG, Germany ID 153159-.

  2. Re-Assembled Botulinum Neurotoxin Inhibits CNS Functions without Systemic Toxicity

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    Bazbek Davletov

    2011-03-01

    Full Text Available The therapeutic potential of botulinum neurotoxin type A (BoNT/A has recently been widely recognized. BoNT/A acts to silence synaptic transmission via specific proteolytic cleavage of an essential neuronal protein, SNAP25. The advantages of BoNT/A-mediated synaptic silencing include very long duration, high potency and localized action. However, there is a fear of possible side-effects of BoNT/A due to its diffusible nature which may lead to neuromuscular blockade away from the injection site. We recently developed a “protein-stapling” technology which allows re-assembly of BoNT/A from two separate fragments. This technology allowed, for the first time, safe production of this popular neuronal silencing agent. Here we evaluated the re-assembled toxin in several CNS assays and assessed its systemic effects in an animal model. Our results show that the re-assembled toxin is potent in inhibiting CNS function at 1 nM concentration but surprisingly does not exhibit systemic toxicity after intraperitoneal injection even at 200 ng/kg dose. This shows that the re-assembled toxin represents a uniquely safe tool for neuroscience research and future medical applications.

  3. The spindle assembly function of Caenorhabditis elegans katanin does not require microtubule-severing activity

    Science.gov (United States)

    McNally, Karen Perry; McNally, Francis J.

    2011-01-01

    Katanin is a heterodimeric microtubule-severing protein that is conserved among eukaryotes. Loss-of-function mutations in the Caenorhabditis elegans katanin catalytic subunit, MEI-1, cause specific defects in female meiotic spindles. To determine the relationship between katanin’s microtubule-severing activity and its role in meiotic spindle formation, we analyzed the MEI-1(A338S) mutant. Unlike wild-type MEI-1, which mediated disassembly of microtubule arrays in Xenopus fibroblasts, MEI-1(A338S) had no effect on fibroblast microtubules, indicating a lack of microtubule-severing activity. In C. elegans, MEI-1(A338S) mediated assembly of extremely long bipolar meiotic spindles. In contrast, a nonsense mutation in MEI-1 caused assembly of meiotic spindles without any poles as assayed by localization of the spindle-pole protein, ASPM-1. These results indicated that katanin protein, but not katanin’s microtubule-severing activity, is required for assembly of acentriolar meiotic spindle poles. To understand the nonsevering activities of katanin, we characterized the N-terminal domain of the katanin catalytic subunit. The N-terminal domain was necessary and sufficient for binding to the katanin regulatory subunit. The katanin regulatory subunit in turn caused a dramatic change in the microtubule-binding properties of the N-terminal domain of the catalytic subunit. This unique bipartite microtubule-binding structure may mediate the spindle-pole assembly activity of katanin during female meiosis. PMID:21372175

  4. Re-Assembled Botulinum Neurotoxin Inhibits CNS Functions without Systemic Toxicity

    Science.gov (United States)

    Ferrari, Enrico; Maywood, Elizabeth S.; Restani, Laura; Caleo, Matteo; Pirazzini, Marco; Rossetto, Ornella; Hastings, Michael H.; Niranjan, Dhevahi; Schiavo, Giampietro; Davletov, Bazbek

    2011-01-01

    The therapeutic potential of botulinum neurotoxin type A (BoNT/A) has recently been widely recognized. BoNT/A acts to silence synaptic transmission via specific proteolytic cleavage of an essential neuronal protein, SNAP25. The advantages of BoNT/A-mediated synaptic silencing include very long duration, high potency and localized action. However, there is a fear of possible side-effects of BoNT/A due to its diffusible nature which may lead to neuromuscular blockade away from the injection site. We recently developed a “protein-stapling” technology which allows re-assembly of BoNT/A from two separate fragments. This technology allowed, for the first time, safe production of this popular neuronal silencing agent. Here we evaluated the re-assembled toxin in several CNS assays and assessed its systemic effects in an animal model. Our results show that the re-assembled toxin is potent in inhibiting CNS function at 1 nM concentration but surprisingly does not exhibit systemic toxicity after intraperitoneal injection even at 200 ng/kg dose. This shows that the re-assembled toxin represents a uniquely safe tool for neuroscience research and future medical applications. PMID:22069712

  5. Molecular Dynamics Studies of Self-Assembling Biomolecules and DNA-functionalized Gold Nanoparticles

    Science.gov (United States)

    Cho, Vince Y.

    This thesis is organized as following. In Chapter 2, we use fully atomistic MD simulations to study the conformation of DNA molecules that link gold nanoparticles to form nanoparticle superlattice crystals. In Chapter 3, we study the self-assembly of peptide amphiphiles (PAs) into a cylindrical micelle fiber by using CGMD simulations. Compared to fully atomistic MD simulations, CGMD simulations prove to be computationally cost-efficient and reasonably accurate for exploring self-assembly, and are used in all subsequent chapters. In Chapter 4, we apply CGMD methods to study the self-assembly of small molecule-DNA hybrid (SMDH) building blocks into well-defined cage-like dimers, and reveal the role of kinetics and thermodynamics in this process. In Chapter 5, we extend the CGMD model for this system and find that the assembly of SMDHs can be fine-tuned by changing parameters. In Chapter 6, we explore superlattice crystal structures of DNA-functionalized gold nanoparticles (DNA-AuNP) with the CGMD model and compare the hybridization.

  6. Hanoi tower-like multilayered ultrathin palladium nanosheets.

    Science.gov (United States)

    Yin, Xi; Liu, Xinhong; Pan, Yung-Tin; Walsh, Kathleen A; Yang, Hong

    2014-12-10

    This paper describes the synthesis, formation mechanism, and mechanical property of multilayered ultrathin Pd nanosheets. An anisotropic, Hanoi Tower-like assembly of Pd nanosheets was identified by transmission electron microscopy and atomic force microscopy (AFM). These nanosheets may contain ultrathin Pd layers, down to single unit cell thickness. Selected area electron diffraction and scanning transmission electron microscopy data show the interconnected atomically thick layers stacking vertically with rotational mismatches, resulting in unique diffractions and Moiré patterns. Density functional theory (DFT) calculation with van der Waals correction (DFT+vdW) shows the adsorption of Pd4(CO)4(OAc)4 on Pd(110) surface (Ead = -5.68 eV) is much stronger than that on Pd(100) (Ead = -4.72 eV) or on Pd(111) (Ead = -3.80 eV). The adsorption strength of this Pd complex is significantly stronger than that of CO on the same Pd surfaces. The DFT+vdW calculation results suggest a new mechanism for the observed anisotropic growth of nanosheets with unusually high aspect ratio, in which the competitive adsorptions between Pd4(CO)4(OAc)4 complex and CO on various surfaces result in a favored growth along the ⟨110⟩ directions and inhibition along ⟨111⟩ directions. The mechanical property of these multilayered Pd nanosheets was studied using AFM and nanoindentation techniques, which indicate multilayered nanosheets show more plastic deformation than the bulk in response to an applied force.

  7. Saccharomyces cerevisiae Ribosomal Protein L26 Is Not Essential for Ribosome Assembly and Function

    Science.gov (United States)

    Babiano, Reyes; Gamalinda, Michael

    2012-01-01

    Ribosomal proteins play important roles in ribosome biogenesis and function. Here, we study the evolutionarily conserved L26 in Saccharomyces cerevisiae, which assembles into pre-60S ribosomal particles in the nucle(ol)us. Yeast L26 is one of the many ribosomal proteins encoded by two functional genes. We have disrupted both genes; surprisingly, the growth of the resulting rpl26 null mutant is apparently identical to that of the isogenic wild-type strain. The absence of L26 minimally alters 60S ribosomal subunit biogenesis. Polysome analysis revealed the appearance of half-mers. Analysis of pre-rRNA processing indicated that L26 is mainly required to optimize 27S pre-rRNA maturation, without which the release of pre-60S particles from the nucle(ol)us is partially impaired. Ribosomes lacking L26 exhibit differential reactivity to dimethylsulfate in domain I of 25S/5.8S rRNAs but apparently are able to support translation in vivo with wild-type accuracy. The bacterial homologue of yeast L26, L24, is a primary rRNA binding protein required for 50S ribosomal subunit assembly in vitro and in vivo. Our results underscore potential differences between prokaryotic and eukaryotic ribosome assembly. We discuss the reasons why yeast L26 plays such an apparently nonessential role in the cell. PMID:22688513

  8. Species divergence vs functional convergence characterizes crude oil microbial community assembly

    Directory of Open Access Journals (Sweden)

    Yong Nie

    2016-08-01

    Full Text Available Oil reservoirs exhibit extreme environmental conditions such as high salinity and high temperature. Insights into microbial community assemblages in oil reservoirs and their functional potentials are important for understanding biogeochemical cycles in the subterranean biosphere. In this study, we performed shotgun metagenomic sequencing of crude oil samples from two geographically distant oil reservoirs in China, and compared them with all the 948 available environmental metagenomes deposited in IMG database (until October 2013. Although the dominant bacteria and the proportion of hydrogenotrophic and acetoclastic methanogens were different among oil metagenomes, compared with the metagenomes from other environments, all the oil metagenomes contained higher abundances of genes involved in methanogenic hydrocarbon degradation and stress response systems. In addition, a shape-sorting manner was proposed for the assembly of microbial communities in oil reservoirs, with the oil reservoir acting as a function sorter to select microbes with special functions from its endemic pool of microorganisms. At the functional level, we found that environmental metagenomes were generally clustered according to their isolation environments but not their geographical locations, suggesting selective processes to be involved in the assembly of microbial communities based on functional gene composition.

  9. Stress Compensating Multilayers

    Science.gov (United States)

    Broadway, David M.; Ramsey, Brian D.; O'dell, Stephen; Gurgew, Danielle

    2017-01-01

    We present in-situ stress measurement results for single and multilayer thin-films deposited by magnetron sputtering. In particular, we report on the influence of the material interfaces on the ensuing stress in both the transient and steady-state regimes of film growth. This behavior is used to determine the appropriate thicknesses of the constituent layers that will result in a net tensile stress in multilayers composed of various material combinations. These multilayers can then be used to compensate the compressive integrated stress in single and multilayer EUV and x-ray optical coatings. The use of multilayers to compensate the integrated stress might be advantageous because, unlike single layers of chromium, the roughness is not expected to increase with the total thickness of the multilayer. In this paper, we demonstrate the technique for W/Si and Mo/Si multilayers and discuss its application to other material combinations.

  10. Controlled deposition of functionalized silica coated zinc oxide nano-assemblies at the air/water interface for blood cancer detection

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, Chandra Mouli [Biomedical Instrumentation Section, CSIR-National Physical Laboratory, New Delhi 110012 (India); Nanobioelectronics Laboratory, Department of Biotechnology, Delhi Technological University, Delhi 110042 (India); Dewan, Srishti [Biomedical Instrumentation Section, CSIR-National Physical Laboratory, New Delhi 110012 (India); Biomedical Engineering Department, Deenbandhu Chhotu Ram University of Science & Technology, Haryana 131039 (India); Chawla, Seema [Biomedical Engineering Department, Deenbandhu Chhotu Ram University of Science & Technology, Haryana 131039 (India); Yadav, Birendra Kumar [Rajiv Gandhi Cancer Institute and Research Centre, Rohini, Delhi 110085 (India); Sumana, Gajjala, E-mail: sumanagajjala@gmail.com [Biomedical Instrumentation Section, CSIR-National Physical Laboratory, New Delhi 110012 (India); Malhotra, Bansi Dhar, E-mail: bansi.malhotra@gmail.com [Biomedical Instrumentation Section, CSIR-National Physical Laboratory, New Delhi 110012 (India); Nanobioelectronics Laboratory, Department of Biotechnology, Delhi Technological University, Delhi 110042 (India)

    2016-09-21

    We report results of the studies relating to controlled deposition of the amino-functionalized silica-coated zinc oxide (Am-Si@ZnO) nano-assemblies onto an indium tin oxide (ITO) coated glass substrate using Langmuir-Blodgett (LB) technique. The monolayers have been deposited by transferring the spread solution of Am-Si@ZnO stearic acid prepared in chloroform at the air-water interface, at optimized pressure (16 mN/m), concentration (10 mg/ml) and temperature (23 °C). The high-resolution transmission electron microscopic studies of the Am-Si@ZnO nanocomposite reveal that the nanoparticles have a microscopic structure comprising of hexagonal assemblies of ZnO with typical dimensions of 30 nm. The surface morphology of the LB multilayer observed by scanning electron microscopy shows uniform surface of the Am-Si@ZnO film in the nanometer range (<80 nm). These electrodes have been utilized for chronic myelogenous leukemia (CML) detection by covalently immobilizing the amino-terminated oligonucleotide probe sequence via glutaraldehyde as a crosslinker. The response studies of these fabricated electrodes carried out using electrochemical impedance spectroscopy show that this Am-Si@ZnO LB film based nucleic acid sensor exhibits a linear response to complementary DNA (10{sup −6}–10{sup −16} M) with a detection limit of 1 × 10{sup −16} M. This fabricated platform is validated with clinical samples of CML positive patients and the results demonstrate its immense potential for clinical diagnosis. - Graphical abstract: Controlled deposition of functionalized silica coated zinc oxide nano-assemblies at the air/water interface for label free electrochemical detection of chronic myelogenous leukemia. - Highlights: • Stable and controlled deposition of Am-Si@ZnO nano-assemblies using LB technique. • Uniform monolayer deposition of the Am-Si@ZnO LB film within the nanometer range. • Am-Si@ZnO LB film shows enhanced electrochemical properties. • Fabricated

  11. Synthesis and Self-Assembly of Chiral Cylindrical Molecular Complexes: Functional Heterogeneous Liquid-Solid Materials Formed by Helicene Oligomers

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    Nozomi Saito

    2018-01-01

    Full Text Available Chiral cylindrical molecular complexes of homo- and hetero-double-helices derived from helicene oligomers self-assemble in solution, providing functional heterogeneous liquid-solid materials. Gels and liotropic liquid crystals are formed by fibril self-assembly in solution; molecular monolayers and fibril films are formed by self-assembly on solid surfaces; gels containing gold nanoparticles emit light; silica nanoparticles aggregate and adsorb double-helices. Notable dynamics appears during self-assembly, including multistep self-assembly, solid surface catalyzed double-helix formation, sigmoidal and stairwise kinetics, molecular recognition of nanoparticles, discontinuous self-assembly, materials clocking, chiral symmetry breaking and homogeneous-heterogeneous transitions. These phenomena are derived from strong intercomplex interactions of chiral cylindrical molecular complexes.

  12. Single-Molecule Transistor from Graphene Nanoelectrodes and Novel Functional Materials From Self-assembly

    Science.gov (United States)

    Xu, Qizhi

    This thesis introduces a new strategy to fabricate single molecular transistor by utilizing the covalent chemistry to reconnect the molecule with the electroburnt graphene nanogap. We studied the effect of coupling chemistry and molecular length on the efficiency of reconnection between the molecule and the graphene. With this technique, we are also able to observe the Coulomb Blockade phenomenon, which is a characteristics of single-electron transistors. The high yield and versatility of this approach augur well for creating a new generation of sensors, switches, and other functional devices using graphene contacts. This thesis also introduces a new type of organic single-crystal p-n heterojunction inspired from the ball-and-socket shape-complementarity between fullerene and contorted dibenzotetrathienocoronene (c-DBTTC). We studied the influence of temperature, pressure, and time on the self-assembly process of contorted dibenzotetrathienocoronene on the as-grown fullerene crystals. We also utilized fluorescence microscopy to investigate the charge transfer in this type of p-n heterojunction. Finally, this thesis introduces one-dimensional and two-dimensional programming in solid-state materials from superatom macrocycles. We find that the linkers that bridges the two superatoms determine the distance and electronic coupling between the two superatoms in the macrocycle, which in turn determines the way they self-assembled in the solid-state materials. The thesis is composed of four chapters. The first chapter introduces why we are in terested in molecular transistors and new functional materials, and what has been done so far. The second chapter described the approach we developed to assemble single molecule into circuits with graphene electrodes. The third chapter details the method to fabricate the organic single-crystal C60-DBTTC p-n heterojunction, which is of great importance to understand their charge transfer process. The last chapter introduced a new

  13. De novo assembly, characterization and functional annotation of pineapple fruit transcriptome through massively parallel sequencing.

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    Wen Dee Ong

    Full Text Available BACKGROUND: Pineapple (Ananas comosus var. comosus, is an important tropical non-climacteric fruit with high commercial potential. Understanding the mechanism and processes underlying fruit ripening would enable scientists to enhance the improvement of quality traits such as, flavor, texture, appearance and fruit sweetness. Although, the pineapple is an important fruit, there is insufficient transcriptomic or genomic information that is available in public databases. Application of high throughput transcriptome sequencing to profile the pineapple fruit transcripts is therefore needed. METHODOLOGY/PRINCIPAL FINDINGS: To facilitate this, we have performed transcriptome sequencing of ripe yellow pineapple fruit flesh using Illumina technology. About 4.7 millions Illumina paired-end reads were generated and assembled using the Velvet de novo assembler. The assembly produced 28,728 unique transcripts with a mean length of approximately 200 bp. Sequence similarity search against non-redundant NCBI database identified a total of 16,932 unique transcripts (58.93% with significant hits. Out of these, 15,507 unique transcripts were assigned to gene ontology terms. Functional annotation against Kyoto Encyclopedia of Genes and Genomes pathway database identified 13,598 unique transcripts (47.33% which were mapped to 126 pathways. The assembly revealed many transcripts that were previously unknown. CONCLUSIONS: The unique transcripts derived from this work have rapidly increased of the number of the pineapple fruit mRNA transcripts as it is now available in public databases. This information can be further utilized in gene expression, genomics and other functional genomics studies in pineapple.

  14. Functional diversity and community assembly of river invertebrates show globally consistent responses to decreasing glacier cover.

    Science.gov (United States)

    Brown, Lee E; Khamis, Kieran; Wilkes, Martin; Blaen, Phillip; Brittain, John E; Carrivick, Jonathan L; Fell, Sarah; Friberg, Nikolai; Füreder, Leopold; Gislason, Gisli M; Hainie, Sarah; Hannah, David M; James, William H M; Lencioni, Valeria; Olafsson, Jon S; Robinson, Christopher T; Saltveit, Svein J; Thompson, Craig; Milner, Alexander M

    2018-02-01

    Global change threatens invertebrate biodiversity and its central role in numerous ecosystem functions and services. Functional trait analyses have been advocated to uncover global mechanisms behind biodiversity responses to environmental change, but the application of this approach for invertebrates is underdeveloped relative to other organism groups. From an evaluation of 363 records comprising >1.23 million invertebrates collected from rivers across nine biogeographic regions on three continents, consistent responses of community trait composition and diversity to replicated gradients of reduced glacier cover are demonstrated. After accounting for a systematic regional effect of latitude, the processes shaping river invertebrate functional diversity are globally consistent. Analyses nested within individual regions identified an increase in functional diversity as glacier cover decreases. Community assembly models demonstrated that dispersal limitation was the dominant process underlying these patterns, although environmental filtering was also evident in highly glacierized basins. These findings indicate that predictable mechanisms govern river invertebrate community responses to decreasing glacier cover globally.

  15. Click functionalization of phenyl-capped bithiophene on azide-terminated self-assembled monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Yijun; Cui, Jiaxi [Max Planck Institute for Polymer Research (MPIP), Ackermannweg 10, Mainz 55128 (Germany); Ikeda, Taichi, E-mail: IKEDA.Taichi@nims.go.jp [Max Planck Institute for Polymer Research (MPIP), Ackermannweg 10, Mainz 55128 (Germany); Polymer Materials Unit, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044 (Japan)

    2015-11-15

    Graphical abstract: - Highlights: • Electrochemically-active self-assembled monolayers with phenyl-capped bithiophene were prepared. • Post-functionalization method based on click chemistry solved the solubility issue of phenyl-capped thiophene alkanethiol. • The capture and release of the counter anions during the redox reaction were detectable by E-QCM. - Abstract: We immobilized tetra(ethylene glycol)-substituted phenyl-capped bithiophene with alkyne terminals (Ph2TPh-alkyne) on azide-terminated self-assembled monolayers (N{sub 3}-SAMs) by Cu-catalyzed azide-alkyne cycloaddition reaction. Ph2TPh-functionalized SAMs on a gold substrate showed reversible electrochemical response. The surface densities of the azide groups in N{sub 3}-SAMs and Ph2TPh units in Ph2TPh-functionalized SAMs were estimated to be 7.3 ± 0.3 × 10{sup −10} mol cm{sup −2} and 4.6 ± 0.3 × 10{sup −10} mol cm{sup −2}, respectively, by quartz crystal microbalance (QCM). Most of Ph2TPh-alkynes are considered to be anchored on N{sub 3}-SAMs via both terminal groups. Ph2TPh-functionalized SAMs exhibited reversible redox peaks in cyclic voltammetry (CV). In redox reaction, reversible capture and release of the counter anion could be monitored by electrochemical QCM (E-QCM).

  16. Deformation Mechanism Map of Cu/Nb Nanoscale Metallic Multilayers as a Function of Temperature and Layer Thickness

    Science.gov (United States)

    Snel, J.; Monclús, M. A.; Castillo-Rodríguez, M.; Mara, N.; Beyerlein, I. J.; Llorca, J.; Molina-Aldareguía, J. M.

    2017-11-01

    The mechanical properties and deformation mechanisms of Cu/Nb nanoscale metallic multilayers (NMMs) manufactured by accumulative roll bonding are studied at 25°C and 400°C. Cu/Nb NMMs with individual layer thicknesses between 7 nm and 63 nm were tested by in situ micropillar compression inside a scanning electron microscope. Yield strength, strain-rate sensitivities and activation volumes were obtained from the pillar compression tests. The deformed micropillars were examined under scanning and transmission electron microscopy in order to examine the deformation mechanisms active for different layer thicknesses and temperatures. The analysis suggests that room temperature deformation was determined by dislocation glide at larger layer thicknesses and interface-related mechanisms at the thinner layer thicknesses. The high-temperature compression tests, in contrast, revealed superior thermo-mechanical stability and strength retention for the NMMs with larger layer thicknesses with deformation controlled by dislocation glide. A remarkable transition in deformation mechanism occurred as the layer thickness decreased, to a deformation response controlled by diffusion processes along the interfaces, which resulted in temperature-induced softening. A deformation mechanism map, in terms of layer thickness and temperature, is proposed from the results obtained in this investigation.

  17. Ebp2 and Brx1 function cooperatively in 60S ribosomal subunit assembly in Saccharomyces cerevisiae

    Science.gov (United States)

    Shimoji, Kaori; Jakovljevic, Jelena; Tsuchihashi, Kanako; Umeki, Yuka; Wan, Kun; Kawasaki, Suzuka; Talkish, Jason; Woolford, John L.; Mizuta, Keiko

    2012-01-01

    The yeast protein Ebp2 is required for early steps in production of 60S ribosomal subunits. To search for cofactors with which Ebp2 functions, or substrates on which it acts, we screened for mutants that were synthetically lethal (sl) with the ebp2-14 mutation. Four different mutant alleles of the 60S ribosomal subunit assembly factor Brx1 were found. To investigate defects of the double mutant, we constructed strains conditional for the ebp2-14 brx1- synthetic lethal phenotype. These ebp2-14 brx1 mutants were defective in processing of 27S pre-rRNA and production of 60S subunits, under conditions where each single mutant was not. Ebp2 and Brx1 exhibit a strong two-hybrid interaction, which is eliminated by some combinations of brx1 and ebp2 mutations. In one such mutant, Ebp2 and Brx1 can still associate with pre-ribosomes, but subunit maturation is perturbed. Depletion of either Ebp2 or Brx1 revealed that Brx1 requires Ebp2 for its stable association with pre-ribosomes, but Ebp2 does not depend on the presence of Brx1 to enter pre-ribosomes. These results suggest that assembly of 60S ribosomal subunits requires cooperation of Ebp2 with Brx1, together with other molecules present in pre-ribosomes, potentially including several found in assembly subcomplexes with Brx1 and Ebp2. PMID:22319211

  18. Functional analysis of the accessory protein TapA in Bacillus subtilis amyloid fiber assembly.

    Science.gov (United States)

    Romero, Diego; Vlamakis, Hera; Losick, Richard; Kolter, Roberto

    2014-04-01

    Bacillus subtilis biofilm formation relies on the assembly of a fibrous scaffold formed by the protein TasA. TasA polymerizes into highly stable fibers with biochemical and morphological features of functional amyloids. Previously, we showed that assembly of TasA fibers requires the auxiliary protein TapA. In this study, we investigated the roles of TapA sequences from the C-terminal and N-terminal ends and TapA cysteine residues in its ability to promote the assembly of TasA amyloid-like fibers. We found that the cysteine residues are not essential for the formation of TasA fibers, as their replacement by alanine residues resulted in only minor defects in biofilm formation. Mutating sequences in the C-terminal half had no effect on biofilm formation. However, we identified a sequence of 8 amino acids in the N terminus that is key for TasA fiber formation. Strains expressing TapA lacking these 8 residues were completely defective in biofilm formation. In addition, this TapA mutant protein exhibited a dominant negative effect on TasA fiber formation. Even in the presence of wild-type TapA, the mutant protein inhibited fiber assembly in vitro and delayed biofilm formation in vivo. We propose that this 8-residue sequence is crucial for the formation of amyloid-like fibers on the cell surface, perhaps by mediating the interaction between TapA or TapA and TasA molecules.

  19. Functionalization, self-assembly, and photoswitching quenching for azobenzene derivatives adsorbed on Au(111).

    Science.gov (United States)

    Cho, Jongweon; Berbil-Bautista, L; Levy, Niv; Poulsen, Daniel; Fréchet, Jean M J; Crommie, Michael F

    2010-12-21

    We have used scanning tunneling microscopy to investigate the structure and photoswitching behavior of azobenzene molecules functionalized with bulky spacer groups and adsorbed onto Au(111). We find that positioning tert-butyl "legs" in a canted arrangement on the azobenzene phenyl rings quenches photoisomerizability of the molecule on Au(111). Addition of cyano groups at the para positions changes the molecular self-assembly significantly, but does not alter the quenched photoisomerizability. This behavior likely arises from a combination of molecule-surface interactions, molecule-molecule interactions, and alteration of azobenzene electronic structure resulting from the position-specific addition of tert-butyl groups.

  20. 3D assembly of preformed colloidal nanoparticles into gels and aerogels: function-led design.

    Science.gov (United States)

    Wen, Dan; Eychmüller, Alexander

    2017-11-23

    Gels and aerogels derived from colloidal nanoparticles not only own the advantages of the traditional aerogels like ultra-low density, large surface area and high porosity, but also retain some of the unique properties of the nanoparticles. These characteristics endow such new types of materials with the possibility of promising applications. In this review, we focus on the function-led design of aerogels from the 3D assembly of 0D spherical particles, 1D nanowires, and 2D nanosheets, and especially their applications in catalysis, sensing, optoelectronics, pollutant adsorbents/filtration, and beyond.

  1. Functional redundancy patterns reveal non-random assembly rules in a species-rich marine assemblage.

    Directory of Open Access Journals (Sweden)

    Nicolas Guillemot

    Full Text Available The relationship between species and the functional diversity of assemblages is fundamental in ecology because it contains key information on functional redundancy, and functionally redundant ecosystems are thought to be more resilient, resistant and stable. However, this relationship is poorly understood and undocumented for species-rich coastal marine ecosystems. Here, we used underwater visual censuses to examine the patterns of functional redundancy for one of the most diverse vertebrate assemblages, the coral reef fishes of New Caledonia, South Pacific. First, we found that the relationship between functional and species diversity displayed a non-asymptotic power-shaped curve, implying that rare functions and species mainly occur in highly diverse assemblages. Second, we showed that the distribution of species amongst possible functions was significantly different from a random distribution up to a threshold of ∼90 species/transect. Redundancy patterns for each function further revealed that some functions displayed fast rates of increase in redundancy at low species diversity, whereas others were only becoming redundant past a certain threshold. This suggested non-random assembly rules and the existence of some primordial functions that would need to be fulfilled in priority so that coral reef fish assemblages can gain a basic ecological structure. Last, we found little effect of habitat on the shape of the functional-species diversity relationship and on the redundancy of functions, although habitat is known to largely determine assemblage characteristics such as species composition, biomass, and abundance. Our study shows that low functional redundancy is characteristic of this highly diverse fish assemblage, and, therefore, that even species-rich ecosystems such as coral reefs may be vulnerable to the removal of a few keystone species.

  2. Simple micropatterning of proteins using polyelectrolyte multilayers and microcontact printing

    Science.gov (United States)

    Lee, Ji-Hye; Choi, Chang-Hyung; Lee, Chang-Soo

    2007-12-01

    The selective immobilization of various biomolecules in well-defined area is important technique for the development of biosensors and biochips. Especially, the fabrication of protein micropatterns preserving their functional activity on the desired surface is critical issue for the development of medical diagnostic devices and basic protein studies. In this study, we have introduced a simple but reliable method of protein patterning on functionalized polyelectrolyte thin films (PEL) through consecutive layer-by-layer adsorption of polyelectrolytes via self-assembly technique and microcontact printing (μCP). For the selection of appropriate surface, several representative surfaces modified with various functional materials including aldehyde, epoxide, poly-L-lysine, amine, and self-assembled polyelectrolyte multilayers (PEL) were investigated. The PEL surface providing electrostatic interaction force showed most high functionality in point of homogeneous patterning of proteins with high density and preservation of inherent 3-dimensional structure of proteins. Immunoassay as a model system of protein-protein interaction showed good linearity, indicating the feasibility of a quantitative measurement of the concentration of target proteins in sample. Our proposed approach based on PEL constructed by self-assembly technique in aqueous solution is green chemistry and cost-effective method to generate stable 3-D thin film on surface. The demand for strict control over the positioning and the stable immobilization of several kinds of biomolecules in fabricated structures can result in many applications.

  3. An essential role for DYF-11/MIP-T3 in assembling functional intraflagellar transport complexes.

    Directory of Open Access Journals (Sweden)

    Chunmei Li

    2008-03-01

    Full Text Available MIP-T3 is a human protein found previously to associate with microtubules and the kinesin-interacting neuronal protein DISC1 (Disrupted-in-Schizophrenia 1, but whose cellular function(s remains unknown. Here we demonstrate that the C. elegans MIP-T3 ortholog DYF-11 is an intraflagellar transport (IFT protein that plays a critical role in assembling functional kinesin motor-IFT particle complexes. We have cloned a loss of function dyf-11 mutant in which several key components of the IFT machinery, including Kinesin-II, as well as IFT subcomplex A and B proteins, fail to enter ciliary axonemes and/or mislocalize, resulting in compromised ciliary structures and sensory functions, and abnormal lipid accumulation. Analyses in different mutant backgrounds further suggest that DYF-11 functions as a novel component of IFT subcomplex B. Consistent with an evolutionarily conserved cilia-associated role, mammalian MIP-T3 localizes to basal bodies and cilia, and zebrafish mipt3 functions synergistically with the Bardet-Biedl syndrome protein Bbs4 to ensure proper gastrulation, a key cilium- and basal body-dependent developmental process. Our findings therefore implicate MIP-T3 in a previously unknown but critical role in cilium biogenesis and further highlight the emerging role of this organelle in vertebrate development.

  4. Building up Functional Bionanocomposites from the Assembly of Clays and Biopolymers.

    Science.gov (United States)

    Alcântara, Ana C S; Darder, Margarita

    2018-01-04

    Functional bionanocomposites are developed from the assembly of naturally occurring polymers and inorganic solids that show at least one dimension at the nanoscale. Our research group focused on the development of bionanocomposites based on clay minerals, including smectites and fibrous silicates, as well as layered double hydroxides. The resulting materials show interesting properties regarding biocompatibility and biodegradability, together with improved mechanical and thermal properties in comparison to the pristine biopolymer. Besides these characteristics, they offer also other interesting functional properties that allow their potential use in a wide range of applications, including sensors, drug delivery and other health care applications, bioplastics and environmental remediation. For these materials, nature provides not only the components but also the inspiration to develop new combinations that may give rise to nanostructured biomaterials with exceptional features. © 2018 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Functionalization of reactive polymer multilayers with RGD and an anti-fouling motif: RGD density provides control over human corneal epithelial cell-substrate interactions

    Science.gov (United States)

    Tocce, Elizabeth J.; Broderick, Adam H.; Murphy, Kaitlin C.; Liliensiek, Sara J.; Murphy, Christopher J.; Lynn, David M.; Nealey, Paul F.

    2011-01-01

    Our study demonstrates that substrates fabricated using a ‘reactive’ layer-by-layer approach promote well-defined cell-substrate interactions of human corneal epithelial cells. Specifically, crosslinked and amine-reactive polymer multilayers were produced by alternating ‘reactive’ deposition of an azlactone-functionalized polymer [poly(2-vinyl-4,4-dimethylazlactone)] and a primary amine-containing polymer [branched poly(ethylene imine)]. Advantages of our system include a 5 to 30-fold decrease in deposition time compared to traditional polyelectrolyte films and direct modification of the films with peptides. Our films react with mixtures of an adhesion-promoting peptide containing Arg-Gly-Asp (RGD) and the small molecule d-glucamine, a chemical motif which is non-fouling. Resulting surfaces prevent protein adsorption and promote cell attachment through specific peptide interactions. The specificity of cell attachment via immobilized RGD sequences was verified using both a scrambled RDG peptide control as well as soluble-RGD competitive assays. Films were functionalized with monotonically increasing surface densities of RGD which resulted in both increased cell attachment and the promotion of a tri-phasic proliferative response of a human corneal epithelial cell line (hTCEpi). The ability to treat PEI/PVDMA films with peptides for controlled cell-substrate interactions enables the use of these films in a wide range of biological applications. PMID:21972074

  6. Tuning the self-assembly of oligothiophenes on chemical vapor deposition graphene: effect of functional group, solvent, and substrate.

    Science.gov (United States)

    Sun, Xiuling; Mu, Youbing; Zhang, Jia; Wang, Xiaona; Hu, Pingan; Wan, Xiaobo; Guo, Zongxia; Lei, Shengbin

    2014-07-01

    Tuning and characterizing the interfacial structure of organic semiconductors on graphene is essential for graphene-based devices. Regulation of the supramolecular assembling structure of oligothiophenes on graphene by changing functional groups attached to the backbone of oligothiophenes is described and the assembling behavior is compared with that on the basal plane of highly oriented pyrolytic graphite. It reveals that terminal functional groups attached to the conjugated backbone of oligothiophene can entirely change the assembling structures. Significant solvent and substrate effects have also been confirmed by comparing the assembling structures of oligothiophenes deposited from tetrahydrofuran, 1,2,4-trichlorobenzene, and octanoic acid onto graphene and graphite. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Dual Function of a Tip Fimbrillin of Actinomyces in Fimbrial Assembly and Receptor Binding▿

    Science.gov (United States)

    Wu, Chenggang; Mishra, Arunima; Yang, Jinghua; Cisar, John O.; Das, Asis; Ton-That, Hung

    2011-01-01

    Interaction of Actinomyces oris with salivary proline-rich proteins (PRPs), which serve as fimbrial receptors, involves type 1 fimbriae. Encoded by the gene locus fimQ-fimP-srtC1, the type 1 fimbria is comprised of the fimbrial shaft FimP and the tip fimbrillin FimQ. Fimbrial polymerization requires the fimbria-specific sortase SrtC1, which catalyzes covalent linkage of fimbrial subunits. Using genetics, biochemical methods, and electron microscopy, we provide evidence that the tip fimbrillin, FimQ, is involved in fimbrial assembly and interaction with PRPs. Specifically, while deletion of fimP completely abolished the type 1 fimbrial structures, surface display of monomeric FimQ was not affected by this mutation. Surprisingly, deletion of fimQ significantly reduced surface assembly of the type 1 fimbriae. This defect was rescued by recombinant FimQ ectopically expressed from a plasmid. In agreement with the role of type 1 fimbriae in binding to PRPs, aggregation of A. oris with PRP-coated beads was abrogated in cells lacking srtC1 or fimP. This aggregation defect of the ΔfimP mutant was mainly due to significant reduction of FimQ on the bacterial surface, as the aggregation was not observed in a strain lacking fimQ. Increasing expression of FimQ in the ΔfimP mutant enhanced aggregation, while overexpression of FimP in the ΔfimQ mutant did not. Furthermore, recombinant FimQ, not FimP, bound surface-associated PRPs in a dose-dependent manner. Thus, not only does FimQ function as the major adhesin of the type 1 fimbriae, it also plays an important role in fimbrial assembly. PMID:21531799

  8. Assembly of a functional 3D primary cardiac construct using magnetic levitation

    Directory of Open Access Journals (Sweden)

    Glauco Souza

    2016-07-01

    Full Text Available Easily assembled organotypic co-cultures have long been sought in medical research. In vitro tissue constructs with faithful representation of in vivo tissue characteristics are highly desirable for screening and characteristic assessment of a variety of tissue types. Cardiac tissue analogs are particularly sought after due to the phenotypic degradation and difficulty of culture of primary cardiac myocytes. This study utilized magnetic nanoparticles and primary cardiac myocytes in order to levitate and culture multicellular cardiac aggregates (MCAs. Cells were isolated from 2 day old Sprague Dawley rat hearts and subsequently two groups were incubated with either C1: 33 µL nanoshell/million cells or C2: 50 µL nanoshell/million cells. Varying numbers of cells for each concentration were cultured in a magnetic field in a 24 well plate and observed over a period of 12 days. Constructs generally formed spherical structures. Masson’s trichrome staining of a construct shows the presence of extracellular matrix protein, indicating the presence of functional fibroblasts. Many constructs exhibited noticeable contraction after 4 days of culture and continued contracting noticeably past day 9 of culture. Noticeable contractility indicates the presence of functional primary cardiac myocytes in culture. Phenotypic conservation of cardiac cells was ascertained using IHC staining by α-actinin and collagen. CD31 and fibrinogen were probed in order to assess localization of fibroblasts and endothelial cells. The study verifies a protocol for the use of magnetic levitation in order to rapidly assemble 3D cardiac like tissue with phenotypic and functional stability.

  9. Aldehyde-functionalized chitosan-montmorillonite films as dynamically-assembled, switchable-chemical release bioplastics.

    Science.gov (United States)

    Chabbi, Jamal; Jennah, Oumayma; Katir, Nadia; Lahcini, Mohamed; Bousmina, Mosto; El Kadib, Abdelkrim

    2018-03-01

    Temporal release of synergistic and/or complementary chemicals (e.g.: drugs) is recognized as extremely challenging because of their frequently intertwined kinetic delivery and presently, straightforward concepts enabling to circumvent this bottleneck are missing in the open literature. In this framework, we report herein on aldehyde-functionalized, transparent and flexible chitosan-montmorillonite hybrid films that act as a new generation of eco-friendly, controlled-chemical release bioplastics. These dynamically-assembled nanomaterials are designed by a ternary assembly from biowaste derived chitin biopolymer, aromatic aldehydes and layered clay nanoparticles. On the basis of their geometrical and conformational properties, the oxygenated groups on the grafted aromatics interact preferentially with either the base Schiff belonging to the carbohydrate (via intramolecular CNHO-Ar known as "imine clip") or with the hydroxyl groups belonging to the clay surface (via intermolecular Si-OHO-Ar). The exfoliated clay nanoparticles within the carbohydrate polymer enables either accelerating or slowing down of the imine (CN) hydrolysis depending on the interaction of the conjugated aromatics. This provides the driving force for fine tuning host-guest interactions at the molecular level and constitutes an entry toward subtle discrimination of different chemicals (e.g. complementary fertilizers, synergistic drugs) during their sequential release. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Dynamic Covalent Functionalization as a route to Controlling Self Assembly of Organic Molecules

    Science.gov (United States)

    Pentzer, Emily

    Efforts to optimize the optoelectronic properties of conjugated organic materials are ongoing across many fields of science and engineering. For example, in bulk heterojunction polymer solar cells, researchers seek to optimize absorption of the solar spectrum by the active materials, form interpenetrating domains of p-type and n-type materials to facilitate exciton dissociation, and improve interactions between electrode, charge blocking layers, and active layers to ensure rapid charge transport. One advantage of organic polymers compared to inorganic materials (e.g., silicon), is the low cost and ability process the materials in solution. Moreover, assembly of conjugated organic materials in solution or in the solid state (i.e., films) can be used to optimize both a material's optoelectronic properties and its interface with surfaces and other materials, addressing many of the concerns listed above. Unfortunately, such solution processability requires appendage of insulating alkyl chains to the conjugated frameworks, which don solubility, but are also insulating and thus can hurt device performance. This presentation will report recent results from the Pentzer Lab from Case Western Reserve University on using functional alkyl chains that serve to control self-assembly, control interfaces with other materials, or can be removed by an external stimulus as a route to optimizing the materials for solar cell applications.

  11. Synthesis and Functionalization of 3D Nano-graphene Materials: Graphene Aerogels and Graphene Macro Assemblies.

    Science.gov (United States)

    Campbell, Patrick G; Worsley, Marcus A; Hiszpanski, Anna M; Baumann, Theodore F; Biener, Juergen

    2015-11-05

    Efforts to assemble graphene into three-dimensional monolithic structures have been hampered by the high cost and poor processability of graphene. Additionally, most reported graphene assemblies are held together through physical interactions (e.g., van der Waals forces) rather than chemical bonds, which limit their mechanical strength and conductivity. This video method details recently developed strategies to fabricate mass-producible, graphene-based bulk materials derived from either polymer foams or single layer graphene oxide. These materials consist primarily of individual graphene sheets connected through covalently bound carbon linkers. They maintain the favorable properties of graphene such as high surface area and high electrical and thermal conductivity, combined with tunable pore morphology and exceptional mechanical strength and elasticity. This flexible synthetic method can be extended to the fabrication of polymer/carbon nanotube (CNT) and polymer/graphene oxide (GO) composite materials. Furthermore, additional post-synthetic functionalization with anthraquinone is described, which enables a dramatic increase in charge storage performance in supercapacitor applications.

  12. Stimuli-Responsive Directional Vesicular Assembly with Tunable Surface Functionality and Impact on Enzyme Inhibition.

    Science.gov (United States)

    Sikder, Amrita; Ray, Debes; Aswal, Vinod K; Ghosh, Suhrit

    2017-08-08

    The article describes the self-assembly of a series of unsymmetrical bola-shaped π-amphiphiles (NDI-1, NDI-1a, NDI-2, NDI-3, and NDI-4) consisting of a hydrophobic naphthalene-diimide (NDI) chromophore attached to a nonionic hydrophilic wedge and an anionic headgroup in the two opposite arms of the central NDI. By design, only a single hydrazide group is linked either on the ionic or nonionic arm of the NDI. NDI-1 and NDI-1a are regioisomers differing only in the location of the hydrazide group, placed in the nonionic or ionic arm, respectively. NDI-2, NDI-3, and NDI-4 are similar to NDI-1 in the placement of the hydrazide group but differ in the nature of the ionic headgroups. Except for NDI-2, all of them exhibit spontaneous vesicle structures in water (pH 9.0) as established by electron microscopy, small-angle neutron scattering, dynamic light scattering, and spectroscopy studies. Supramolecularly assembled oligo-oxyethylene chains of the hydrophobic wedge exhibited a lower critical solution temperature (LCST) at ∼40 °C, similar to that of covalent polymers. Consequently, above the LCST, the bola-amphiphile was converted to a single headgroup surfactant, resulting in the collapse of the vesicular structure to nanoparticles. In all examples, the dominant H-bonding force among the hydrazide groups resulted in unidirectional orientation, leading to the formation of a nonsymmetric membrane with the H-bonded chain located at the inner wall. Therefore, the functional group displayed in these vesicles could be fully dictated by the location of the hydrazide group. Thus, for NDI-1, NDI-3, or NDI-4, the hydrazide group, located at the nonionic arm, directed the nonionic wedge to converge at the inner wall of the vesicle by displaying the anionic headgroups toward the outer surface. In contrast, NDI-1a formed a nonionic vesicle because in this case anionic headgroups were located at the inner wall of the membrane. Furthermore, among NDI-1, NDI-3, and NDI-4, the charge

  13. Soft X-ray multilayers and filters

    CERN Document Server

    Wang Zhan Shan; Tang Wei Xing; Qin Shuji; Zhou Bing; Chen Ling Ya

    2002-01-01

    The periodic and non-periodic multilayers were designed by using a random number to change each layer and a suitable merit function. Ion beam sputtering and magnetron sputtering were used to fabricate various multilayers and beam splitters in soft X-ray range. The characterization of multilayers by small angle X-ray diffraction, Auger electron spectroscopy, Rutherford back scattering spectroscopy and reflectivity illustrated the multilayers had good structures and smooth interlayers. The reflectivity and transmission of a beam splitter is about 5%. The fabrication and transmission properties of Ag, Zr were studied. The Rutherford back scattering spectroscopy and auger electron spectroscopy were used to investigate the contents and distributions of impurities and influence on qualities of filters. The attenuation coefficients were corrected by the data obtained by measurements

  14. Advances in polyelectrolyte multilayer nanofilms as tunable drug delivery systems

    Directory of Open Access Journals (Sweden)

    Bingbing Jiang

    2009-08-01

    Full Text Available Bingbing Jiang1, John B Barnett2,3, Bingyun Li1,4,5#1Biomaterials, Bioengineering and Nanotechnology Laboratory, Department of Orthopaedics, School of Medicine, 2Department of Microbiology, Immunology, and Cell Biology, 3Center for Immunopathology and Microbial Pathogenesis, School of Medicine, 5Department of Chemical Engineering, College of Engineering and Mineral Resources, West Virginia University, Morgantown, WV, USA; 4WVNano Initiative, Morgantown, WV, USA; #Aided by a grant from Osteosynthesis and Trauma Care (OTC FoundationAbstract: There has been considerable interest in polyelectrolyte multilayer nanofilms, which have a variety of applications ranging from optical and electrochemical materials to biomedical devices. Polyelectrolyte multilayer nanofilms are constructed from aqueous solutions using electrostatic layer-by-layer self-assembly of oppositely-charged polyelectrolytes on a solid substrate. Multifunctional polyelectrolyte multilayer nanofilms have been studied using charged dyes, metal and inorganic nanoparticles, DNA, proteins, and viruses. In the past few years, there has been increasing attention to developing polyelectrolyte multilayer nanofilms as drug delivery vehicles. In this mini-review, we present recent developments in polyelectrolyte multilayer nanofilms with tunable drug delivery properties, with particular emphasis on the strategies in tuning the loading and release of drugs in polyelectrolyte multilayer nanofilms as well as their applications.Keywords: nanofilm, polyelectrolyte multilayer, drug delivery, electrostatic layer-by-layer self-assembly, biomedical device, surface modification

  15. Multilayered Polymer Coated Carbon Nanotubes to Deliver Dasatinib

    OpenAIRE

    Moore, Thomas L.; Grimes, Stuart W.; Lewis, Robert L.; Alexis, Frank

    2013-01-01

    Multilayered, multifunctional polymer coatings were grafted onto carbon nanotubes (CNT) using a one-pot, ring-opening polymerization in order to control the release kinetic and therapeutic efficacy of dasatinib. Biocompatible, biodegradable multilayered coatings composed of poly(glycolide) (PGA), and poly(lactide) (PLA) were polymerized directly onto hydroxyl-functionalized CNT surfaces. Sequential addition of monomers into the reaction vessel enabled multilayered coatings of PLA-PGA, or PGA-...

  16. Light-controlled drug releasing polymer films combining LbL self-assembly and host-guest interactions

    Directory of Open Access Journals (Sweden)

    J. Li

    2014-03-01

    Full Text Available By combining LbL (layer-by-layer self-assembly approach and host-guest interactions, a unique multilayer film was constructed and employed for a light-controlled drug release system. The drug molecules can be loaded and released into the resulting polyelectrolyte multilayers containing azobenzene (Azo function groups by using the irradiation of visible light and UV light alternately. The photo-sensitivity of the multilayer films was studied through UV-vis spectrum, fluorescence spectrum and confocal microscopy. The target molecules could be rapidly released from the multilayers after 300 W UV light irradiation for 20 minutes. Moreover, they could be readsorbed into the multilayers uniformly when illuminated under the 300 W visible light for 10 minutes confirmed by the observation of confocal microscopy, and the readsorption ratio exceeds 100% evidenced from UV–vis spectroscopy. After several cycles of the above-mentioned process, the multilayer films show good fatigue resistance. All these results indicate the photo-sensitivity and high-efficiency of the multilayer films, which have great potential in controlled drug delivery platform and biomedical applications.

  17. Namib Desert Soil Microbial Community Diversity, Assembly, and Function Along a Natural Xeric Gradient.

    Science.gov (United States)

    Scola, Vincent; Ramond, Jean-Baptiste; Frossard, Aline; Zablocki, Olivier; Adriaenssens, Evelien M; Johnson, Riegardt M; Seely, Mary; Cowan, Don A

    2018-01-01

    The hyperarid Namib desert is a coastal desert in southwestern Africa and one of the oldest and driest deserts on the planet. It is characterized by a west/east increasing precipitation gradient and by regular coastal fog events (extending up to 75 km inland) that can also provide soil moisture. In this study, we evaluated the role of this natural aridity and xeric gradient on edaphic microbial community structure and function in the Namib desert. A total of 80 individual soil samples were collected at 10-km intervals along a 190-km transect from the fog-dominated western coastal region to the eastern desert boundary. Seventeen physicochemical parameters were measured for each soil sample. Soil parameters reflected the three a priori defined climatic/xeric zones along the transect ("fog," "low rain," and "high rain"). Microbial community structures were characterized by terminal restriction fragment length polymorphism fingerprinting and shotgun metaviromics, and their functional capacities were determined by extracellular enzyme activity assays. Both microbial community structures and activities differed significantly between the three xeric zones. The deep sequencing of surface soil metavirome libraries also showed shifts in viral composition along the xeric transect. While bacterial community assembly was influenced by soil chemistry and stochasticity along the transect, variations in community "function" were apparently tuned by xeric stress.

  18. Human condensin function is essential for centromeric chromatin assembly and proper sister kinetochore orientation.

    Directory of Open Access Journals (Sweden)

    Alexander Samoshkin

    Full Text Available Condensins I and II in vertebrates are essential ATP-dependent complexes necessary for chromosome condensation in mitosis. Condensins depletion is known to perturb structure and function of centromeres, however the mechanism of this functional link remains elusive. Depletion of condensin activity is now shown to result in a significant loss of loading of CENP-A, the histone H3 variant found at active centromeres and the proposed epigenetic mark of centromere identity. Absence of condensins and/or CENP-A insufficiency produced a specific kinetochore defect, such that a functional mitotic checkpoint cannot prevent chromosome missegregation resulting from improper attachment of sister kinetochores to spindle microtubules. Spindle microtubule-dependent deformation of both inner kinetochores and the HEC1/Ndc80 microtubule-capturing module, then results in kinetochore separation from the Aurora B pool and ensuing reduced kinase activity at centromeres. Moreover, recovery from mitosis-inhibition by monastrol revealed a high incidence of merotelic attachment that was nearly identical with condensin depletion, Aurora B inactivation, or both, indicating that the Aurora B dysfunction is the key defect leading to chromosome missegregation in condensin-depleted cells. Thus, beyond a requirement for global chromosome condensation, condensins play a pivotal role in centromere assembly, proper spatial positioning of microtubule-capturing modules and positioning complexes of the inner centromere versus kinetochore plates.

  19. Bioadhesive lipid compositions: self-assembly structures, functionality, and medical applications.

    Science.gov (United States)

    Barauskas, Justas; Christerson, Lars; Wadsäter, Maria; Lindström, Fredrick; Lindqvist, Anna-Karin; Tiberg, Fredrik

    2014-03-03

    Lipid-based liquid crystalline compositions of phospholipids and diglycerides have unique bioadhesive properties with several medical applications, as exemplified by a lipid-based medical device indicated for management and relief of intraoral pain. The present paper describes the relation between self-assembly properties of phosphatidyl choline (PC) and glycerol dioleate (GDO) mixtures in the presence of aqueous fluids and functional attributes of the system, including: film formation and bioadhesion, intraoral coverage, acceptance by patients, and potential as a drug delivery system. The phase behavior of PC/GDO was characterized using synchrotron small-angle X-ray scattering. Functional properties, including the presence of study formulations at intraoral surfaces, ease of attachment, taste, and degree of and intraoral pain, were assessed in a crossover clinical pilot study in head and neck cancer patients. An optimum in functional properties was indicated for formulations with a PC/GDO weight ratio of about 35/65, where the lipids form a reversed cubic liquid crystalline micellar phase structure (Fd3m space group) over the relevant temperature range (25-40 °C).

  20. Improved stability and antidiabetic potential of insulin containing folic acid functionalized polymer stabilized multilayered liposomes following oral administration

    DEFF Research Database (Denmark)

    Agrawal, Ashish Kumar; Harde, Harshad; Thanki, Kaushik

    2014-01-01

    exhibited excellent stability in simulated biological fluids. Caco-2 cell and ex vivo intestinal uptake studies revealed higher uptake of folic acid functionalized layersomes in comparison with their plain counterparts. In vivo pharmacodynamic and pharmacokinetic studies further revealed almost double...... hypoglycemia and approximately 20% relative bioavailability in comparison with subcutaneously administered standard insulin solution. Overall the proposed strategy is expected to contribute significantly in the field of designing ligand-anchored, polyelectrolyte-based stable systems in drug delivery....

  1. Functionalized D-form self-assembling peptide hydrogels for bone regeneration

    Directory of Open Access Journals (Sweden)

    He B

    2016-04-01

    Full Text Available Bin He,1 Yunsheng Ou,1 Ao Zhou,1 Shuo Chen,1 Weikang Zhao,1 Jinqiu Zhao,2 Hong Li,3 Yong Zhu,1 Zenghui Zhao,1 Dianming Jiang1 1Department of Orthopedics, 2Department of Infectious Diseases, The First Affiliated Hospital of Chongqing Medical University, Chongqing, People’s Republic of China; 3School of Physical Science and Technology, Sichuan University, Chengdu, People’s Republic of China Abstract: Bone defects are very common in orthopedics, and there is great need to develop suitable bone grafts for transplantation in vivo. However, current bone grafts still encounter some limitations, including limited availability, immune rejection, poor osteoinduction and osteoconduction, poor biocompatibility and degradation properties, etc. Self-assembling peptide nanofiber scaffolds have emerged as an important substrate for cell culture and bone regeneration. We report on the structural features (eg, Congo red staining, circular dichroism spectroscopy, transmission electron microscopy, and rheometry assays and osteogenic ability of D-RADA16-RGD peptide hydrogels (with or without basic fibroblast growth factor due to the better stability of peptide bonds formed by these peptides compared with those formed by L-form peptides, and use them to fill the femoral condyle defect of Sprague Dawley rat model. The bone morphology change, two-dimensional reconstructions using microcomputed tomography, quantification of the microcomputed tomography analyses as well as histological analyses have demonstrated that RGD-modified D-form peptide scaffolds are able to enhance extensive bone regeneration. Keywords: bone defect, functionalized D-form self-assembling peptide, D-RADA16-RGD, peptide hydrogel, bone regeneration

  2. Self-assembly and omniphobic property of fluorinated unit end-functionalized poly(methyl methacrylate)

    Science.gov (United States)

    Junyan, Liang; Pingdi, Xu; Jingxian, Bao; Ling, He; Nan, Zhu

    2018-03-01

    The self-assembly behavior of fluorinated unit end-functionalized poly(methyl methacrylate) (PDFHM-ef-PMMA) in solution and its influence on the surface microstructure, elemental composition and omniphobic property of cast film was investigated in this work. Specifically, three mixed solutions of tetrahydrofuran (THF)/methanol (MeOH), THF/H2O and THF/H2O/MeOH in various compositions were employed separately as the selective solvents. In THF/MeOH solution, the aggregate morphologies of PDFHM-ef-PMMA changed gradually from core-shell spheres to worm, and then to elliptical vesicles as MeOH content increased. In THF/H2O solution, spherical and bowl-shaped aggregates with significantly larger sizes than those in THF/MeOH solution were favored despite lower H2O content. The further addition of MeOH to THF/H2O mixture could reduce the size of aggregate but hardly change original aggregate morphology. During the film formation process, those self-assembled aggregates in THF/MeOH solution fused with one another to form a smooth surface. When such surface was fully covered by fluorinated segments, the outstanding hexadecane and water slide-off properties and ink-resistant property required for antifouling application were demonstrated. Instead, the aggregates formed in THF/H2O/MeOH mixture were subjected to secondary aggregation of PDFHM-ef-PMMA chains during solvent evaporation, leading to the formation of a particulate film with poor adhesion towards glass plate and hexadecane-repellent property.

  3. Removal of micropollutants in biofilters: Hydrodynamic effects on biofilm assembly and functioning.

    Science.gov (United States)

    Carpenter, Corey M G; Helbling, Damian E

    2017-09-01

    Global water resources contain a variety of micropollutants (MPs), including pharmaceuticals, personal care products, and pesticides. This study investigated the removal of MPs during drinking water production by means of biofiltration. The objective of this work was to investigate the influence of hydrodynamics on biofilm growth and development in a biofiltration process and the consequent effect on MP biotransformation rates. We operated three groups of biofiltration columns continuously for 381 days under three distinct hydrodynamic regimes (superficial velocity: 10, 20, 40 cm h -1 ) and fed them a mixture of 29 micropollutants at low concentrations. Total protein concentrations were used as a surrogate measurement for attached biomass and periodic tracer experiments were conducted to estimate dispersivity and assess changes in the depth of the biological zone in each biofilter. These data revealed significant differences in biofilm assembly among the biofilters; higher superficial velocities led to less concentrated surface biomass but a deeper biological zone and more total biomass. Eleven of the 29 MPs were biotransformed and nine of those could be evaluated to estimate biotransformation rates. The second-order rate constants for all nine MPs were not significantly different among the hydrodynamic regimes. However, a depth-based analysis of biotransformation rates revealed significantly greater second-order rate constants for 5 of the MPs at increasing biofilter depths, suggesting that sparse microbial communities found in deeper and more oligotrophic biofilters had a greater activity for the biotransformation of these MPs. The identification of several transformation products at similar relative distributions suggests that the greater activity was not the result of changing metabolic processes under more oligotrophic conditions. These results improve our fundamental understanding of biofilm assembly and functioning in biofiltration processes. Copyright

  4. In-depth transcriptome analysis of Larimichthys polyactis, de novo assembly, functional annotation.

    Science.gov (United States)

    Liu, Lian-Wei; Sui, You-Zhen; Zhu, Wen-Bin; Guo, Ai; Xu, Kai-Da; Zhou, Yong-Dong

    2017-06-01

    Larimichthys polyactis (small yellow croaker) is a commercially important marine benthic fish, and is the main catching target of fisheries in China, Japan and Korea. Researches across different fields have progressed the understanding of this species; however, no genomics studies of this fish have been reported so far. In this study, we performed de novo transcriptome sequencing of eight cDNA libraries from brain, gill, heart, intestine, liver, muscle, ovary, and testis tissues of L. polyactis. A total of 182,227,948 paired-end reads (>200bp) were generated, from which 134,439 transcripts were assembled. These transcripts yielded a total of 93,990 non-redundant transcripts (unigenes) that were assigned functional annotations based on BlastX searches (E-value<1×10(-5)) against the following databases: NCBI NR, Swiss-Prot, TrEMBL, CDD, Pfam, and COG. In addition, 12,539 simple sequence repeats (SSRs) were identified. Our study provides a valuable resource of L. polyactis transcriptomic data that are expected to be useful for gene expression and functional studies of L. polyactis. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Functionalized Nanochannels from Self-Assembled and Photomodified Poly(Styrene-b-Butadiene-b-Styrene).

    Science.gov (United States)

    Sutisna, Burhannudin; Polymeropoulos, George; Musteata, Valentina; Sougrat, Rachid; Smilgies, Detlef-M; Peinemann, Klaus-Viktor; Hadjichristidis, Nikolaos; Nunes, Suzana P

    2017-10-04

    Membranes are prepared by self-assembly and casting of 5 and 13 wt% poly(styrene-b-butadiene-b-styrene) (PS-b-PB-b-PS) copolymers solutions in different solvents, followed by immersion in water or ethanol. By controlling the solution-casting gap, porous films of 50 and 1 µm thickness are obtained. A gradient of increasing pore size is generated as the distance from the surface increased. An ordered porous surface layer with continuous nanochannels can be observed. Its formation is investigated, by using time-resolved grazing incident small angle X-ray scattering, electron microscopy, and rheology, suggesting a strong effect of the air-solution interface on the morphology formation. The thin PS-b-PB-b-PS ordered films are modified, by promoting the photolytic addition of thioglycolic acid to the polybutadiene groups, adding chemical functionality and specific transport characteristics on the preformed nanochannels, without sacrificing the membrane morphology. Photomodification increases fivefold the water permeance to around 2 L m(-2) h(-1) bar(-1) , compared to that of the unmodified one. A rejection of 74% is measured for methyl orange in water. The membranes fabrication with tailored nanochannels and chemical functionalities can be demonstrated using relatively lower cost block copolymers. Casting on porous polyacrylonitrile supports makes the membranes even more scalable and competitive in large scale. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Supramolecular assemblies of nucleoside functionalized carbon nanotubes: synthesis, film preparation, and properties.

    Science.gov (United States)

    Micoli, Alessandra; Turco, Antonio; Araujo-Palomo, Elsie; Encinas, Armando; Quintana, Mildred; Prato, Maurizio

    2014-04-25

    Nucleoside-functionalized multi-walled carbon nanotubes (N-MWCNTs) were synthesized and characterized. A self-organization process using hydrogen bonding interactions was then used for the fabrication of self-assembled N-MWCNTs films free of stabilizing agents, polymers, or surfactants. Membranes were produced by using a simple water-dispersion-based vacuum-filtration method. Hydrogen-bond recognition was confirmed by analysis with IR spectroscopy and TEM images. Restoration of the electronic conduction properties in the N-MWCNTs membranes was performed by removing the organic portion by thermal treatment under an argon atmosphere to give d-N-MWCNTs. Electrical conductivity and thermal gravimetric analysis (TGA) measurements confirmed the efficiency of the annealing process. Finally, oxidative biodegradation of the films N-MWCNTs and d-N-MWCNTs was performed by using horseradish peroxidase (HRP) and low concentrations of H2 O2 . Our results confirm that functional groups play an important role in the biodegradation of CNT by HRP: N-MWCNTs films were completely biodegraded, whereas for d-N-MWCNTs films no degradation was observed, showing that the pristine CNT undergoes minimal enzyme-catalyzed oxidation This novel methodology offers a straightforward supramolecular strategy for the construction of conductive and biodegradable carbon nanotube films. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Multilayer Social Networks

    DEFF Research Database (Denmark)

    Dickison, Mark; Magnani, Matteo; Rossi, Luca

    Multilayer networks, in particular multilayer social networks, where users belong to and interact on different networks at the same time, are an active research area in social network analysis, computer science, and physics. These networks have traditionally been studied within these separate...... social network systems, the evolution of interconnected social networks, and dynamic processes such as information spreading. A single real dataset is used to illustrate the concepts presented throughout the book, demonstrating both the practical utility and the potential shortcomings of the various...... research communities, leading to the development of several independent models and methods to deal with the same set of problems. This book unifies and consolidates existing practical and theoretical knowledge on multilayer networks including data collection and analysis, modeling, and mining of multilayer...

  8. Multilayer Social Networks

    DEFF Research Database (Denmark)

    Dickison, Mark; Magnani, Matteo; Rossi, Luca

    social network systems, the evolution of interconnected social networks, and dynamic processes such as information spreading. A single real dataset is used to illustrate the concepts presented throughout the book, demonstrating both the practical utility and the potential shortcomings of the various......Multilayer networks, in particular multilayer social networks, where users belong to and interact on different networks at the same time, are an active research area in social network analysis, computer science, and physics. These networks have traditionally been studied within these separate...... research communities, leading to the development of several independent models and methods to deal with the same set of problems. This book unifies and consolidates existing practical and theoretical knowledge on multilayer networks including data collection and analysis, modeling, and mining of multilayer...

  9. Wedged multilayer Laue lens

    Science.gov (United States)

    Conley, Ray; Liu, Chian; Qian, Jun; Kewish, Cameron M.; Macrander, Albert T.; Yan, Hanfei; Kang, Hyon Chol; Maser, Jörg; Stephenson, G. Brian

    2008-05-01

    A multilayer Laue lens (MLL) is an x-ray focusing optic fabricated from a multilayer structure consisting of thousands of layers of two different materials produced by thin-film deposition. The sequence of layer thicknesses is controlled to satisfy the Fresnel zone plate law and the multilayer is sectioned to form the optic. An improved MLL geometry can be created by growing each layer with an in-plane thickness gradient to form a wedge, so that every interface makes the correct angle with the incident beam for symmetric Bragg diffraction. The ultimate hard x-ray focusing performance of a wedged MLL has been predicted to be significantly better than that of a nonwedged MLL, giving subnanometer resolution with high efficiency. Here, we describe a method to deposit the multilayer structure needed for an ideal wedged MLL and report our initial deposition results to produce these structures.

  10. Structural and functional insights into an archaeal L-asparaginase obtained through the linker-less assembly of constituent domains.

    Science.gov (United States)

    Tomar, Rachana; Sharma, Pankaj; Srivastava, Ankit; Bansal, Saurabh; Kundu, Bishwajit

    2014-12-01

    Covalent linkers bridging the domains of multidomain proteins are considered to be crucial for assembly and function. In this report, an exception in which the linker of a two-domain dimeric L-asparaginase from Pyrococcus furiosus (PfA) was found to be dispensable is presented. Domains of this enzyme assembled without the linker into a conjoined tetrameric form that exhibited higher activity than the parent enzyme. The global shape and quaternary structure of the conjoined PfA were also similar to the wild-type PfA, as observed by their solution scattering profiles and X-ray crystallographic data. Comparison of the crystal structures of substrate-bound and unbound enzymes revealed an altogether new active-site composition and mechanism of action. Thus, conjoined PfA is presented as a unique enzyme obtained through noncovalent, linker-less assembly of constituent domains that is stable enough to function efficiently at elevated temperatures.

  11. Self-assembly of "patchy" nanoparticles: a versatile approach to functional hierarchical materials

    National Research Council Canada - National Science Library

    Lunn, David J; Finnegan, John R; Manners, Ian

    2015-01-01

    The solution-phase self-assembly or "polymerization" of discrete colloidal building blocks, such as "patchy" nanoparticles and multicompartment micelles, is attracting growing attention with respect...

  12. Spatial isolation slows down directional plant functional group assembly in restored semi‐natural grasslands

    National Research Council Canada - National Science Library

    Helsen, Kenny; Hermy, Martin; Honnay, Olivier; Firn, Jennifer

    2013-01-01

    Ecological restoration schemes often assume that after reinstating appropriate abiotic conditions, plant communities will assemble following a single predictable pathway towards a fixed target state...

  13. Using phylogeny and functional traits for assessing community assembly along environmental gradients: A deterministic process driven by elevation.

    Science.gov (United States)

    Xu, Jinshi; Chen, Yu; Zhang, Lixia; Chai, Yongfu; Wang, Mao; Guo, Yaoxin; Li, Ting; Yue, Ming

    2017-07-01

    Community assembly processes is the primary focus of community ecology. Using phylogenetic-based and functional trait-based methods jointly to explore these processes along environmental gradients are useful ways to explain the change of assembly mechanisms under changing world. Our study combined these methods to test assembly processes in wide range gradients of elevation and other habitat environmental factors. We collected our data at 40 plots in Taibai Mountain, China, with more than 2,300 m altitude difference in study area and then measured traits and environmental factors. Variance partitioning was used to distinguish the main environment factors leading to phylogeny and traits change among 40 plots. Principal component analysis (PCA) was applied to colligate other environment factors. Community assembly patterns along environmental gradients based on phylogenetic and functional methods were studied for exploring assembly mechanisms. Phylogenetic signal was calculated for each community along environmental gradients in order to detect the variation of trait performance on phylogeny. Elevation showed a better explanatory power than other environment factors for phylogenetic and most traits' variance. Phylogenetic and several functional structure clustered at high elevation while some conserved traits overdispersed. Convergent tendency which might be caused by filtering or competition along elevation was detected based on functional traits. Leaf dry matter content (LDMC) and leaf nitrogen content along PCA 1 axis showed conflicting patterns comparing to patterns showed on elevation. LDMC exhibited the strongest phylogenetic signal. Only the phylogenetic signal of maximum plant height showed explicable change along environmental gradients. Synthesis. Elevation is the best environment factors for predicting phylogeny and traits change. Plant's phylogenetic and some functional structures show environmental filtering in alpine region while it shows different

  14. Control over Structure and Function of Peptide Amphiphile Supramolecular Assemblies through Molecular Design and Energy Landscapes

    Science.gov (United States)

    Tantakitti, Faifan

    Supramolecular chemistry is a powerful tool to create a material of a defined structure with tunable properties. This strategy has led to catalytically active, bioactive, and environment-responsive materials, among others, that are valuable in applications ranging from sensor technology to energy and medicine. Supramolecular polymers formed by peptide amphiphiles (PAs) have been especially relevant in tissue regeneration due to their ability to form biocompatible structures and mimic many important signaling molecules in biology. These supramolecular polymers can form nanofibers that create networks which mimic natural extracellular matrices. PA materials have been shown to induce growth of blood vessels, bone, cartilage, and nervous tissue, among others. The work described in this thesis not only studied the relationship between molecular structure and functions of PA assemblies, but also uncovered a powerful link between the energy landscape of their supramolecular self-assembly and the ability of PA materials to interact with cells. In chapter 2, it is argued that fabricating fibrous nanostructures with defined mechanical properties and decoration with bioactive molecules is not sufficient to create a material that can effectively communicate with cells. By systemically placing the fibronectin-derived RGDS epitope at increasing distances from the surface of PA nanofibers through a linker of one to five glycine residues, integrin-mediated RGDS signaling was enhanced. The results suggested that the spatial presentation of an epitope on PA nanofibers strongly influences the bioactivity of the PA substrates. In further improving functionality of a PA-based scaffold to effectively direct cell growth and differentiation, chapter 3 explored the use of a cell microcarrier to compartmentalize and simultaneously tune insoluble and soluble signals in a single matrix. PA nanofibers were incorporated at the surface of the microcarrier in order to promote cell adhesion, while

  15. Single layers and multilayers of GaN and AlN in square-octagon structure: Stability, electronic properties, and functionalization

    Science.gov (United States)

    Gürbüz, E.; Cahangirov, S.; Durgun, E.; Ciraci, S.

    2017-11-01

    Further to planar single-layer hexagonal structures, GaN and AlN can also form free-standing, single-layer structures constructed from squares and octagons. We performed an extensive analysis of dynamical and thermal stability of these structures in terms of ab initio finite-temperature molecular dynamics and phonon calculations together with the analysis of Raman and infrared active modes. These single-layer square-octagon structures of GaN and AlN display directional mechanical properties and have wide, indirect fundamental band gaps, which are smaller than their hexagonal counterparts. These density functional theory band gaps, however, increase and become wider upon correction. Under uniaxial and biaxial tensile strain, the fundamental band gaps decrease and can be closed. The electronic and magnetic properties of these single-layer structures can be modified by adsorption of various adatoms, or by creating neutral cation-anion vacancies. The single-layer structures attain magnetic moment by selected adatoms and neutral vacancies. In particular, localized gap states are strongly dependent on the type of vacancy. The energetics, binding, and resulting electronic structure of bilayer, trilayer, and three-dimensional (3D) layered structures constructed by stacking the single layers are affected by vertical chemical bonds between adjacent layers. In addition to van der Waals interaction, these weak vertical bonds induce buckling in planar geometry and enhance their binding, leading to the formation of stable 3D layered structures. In this respect, these multilayers are intermediate between van der Waals solids and wurtzite crystals, offering a wide range of tunability.

  16. Brittle Culm1, a COBRA-like protein, functions in cellulose assembly through binding cellulose microfibrils.

    Directory of Open Access Journals (Sweden)

    Lifeng Liu

    Full Text Available Cellulose represents the most abundant biopolymer in nature and has great economic importance. Cellulose chains pack laterally into crystalline forms, stacking into a complicated crystallographic structure. However, the mechanism of cellulose crystallization is poorly understood. Here, via functional characterization, we report that Brittle Culm1 (BC1, a COBRA-like protein in rice, modifies cellulose crystallinity. BC1 was demonstrated to be a glycosylphosphatidylinositol (GPI anchored protein and can be released into cell walls by removal of the GPI anchor. BC1 possesses a carbohydrate-binding module (CBM at its N-terminus. In vitro binding assays showed that this CBM interacts specifically with crystalline cellulose, and several aromatic residues in this domain are essential for binding. It was further demonstrated that cell wall-localized BC1 via the CBM and GPI anchor is one functional form of BC1. X-ray diffraction (XRD assays revealed that mutations in BC1 and knockdown of BC1 expression decrease the crystallite width of cellulose; overexpression of BC1 and the CBM-mutated BC1s caused varied crystallinity with results that were consistent with the in vitro binding assay. Moreover, interaction between the CBM and cellulose microfibrils was largely repressed when the cell wall residues were pre-stained with two cellulose dyes. Treating wild-type and bc1 seedlings with the dyes resulted in insensitive root growth responses in bc1 plants. Combined with the evidence that BC1 and three secondary wall cellulose synthases (CESAs function in different steps of cellulose production as revealed by genetic analysis, we conclude that BC1 modulates cellulose assembly by interacting with cellulose and affecting microfibril crystallinity.

  17. Brittle Culm1, a COBRA-Like Protein, Functions in Cellulose Assembly through Binding Cellulose Microfibrils

    Science.gov (United States)

    Zhang, Baocai; Liu, Xiangling; Yan, Meixian; Zhang, Lanjun; Shi, Yanyun; Zhang, Mu; Qian, Qian; Li, Jiayang; Zhou, Yihua

    2013-01-01

    Cellulose represents the most abundant biopolymer in nature and has great economic importance. Cellulose chains pack laterally into crystalline forms, stacking into a complicated crystallographic structure. However, the mechanism of cellulose crystallization is poorly understood. Here, via functional characterization, we report that Brittle Culm1 (BC1), a COBRA-like protein in rice, modifies cellulose crystallinity. BC1 was demonstrated to be a glycosylphosphatidylinositol (GPI) anchored protein and can be released into cell walls by removal of the GPI anchor. BC1 possesses a carbohydrate-binding module (CBM) at its N-terminus. In vitro binding assays showed that this CBM interacts specifically with crystalline cellulose, and several aromatic residues in this domain are essential for binding. It was further demonstrated that cell wall-localized BC1 via the CBM and GPI anchor is one functional form of BC1. X-ray diffraction (XRD) assays revealed that mutations in BC1 and knockdown of BC1 expression decrease the crystallite width of cellulose; overexpression of BC1 and the CBM-mutated BC1s caused varied crystallinity with results that were consistent with the in vitro binding assay. Moreover, interaction between the CBM and cellulose microfibrils was largely repressed when the cell wall residues were pre-stained with two cellulose dyes. Treating wild-type and bc1 seedlings with the dyes resulted in insensitive root growth responses in bc1 plants. Combined with the evidence that BC1 and three secondary wall cellulose synthases (CESAs) function in different steps of cellulose production as revealed by genetic analysis, we conclude that BC1 modulates cellulose assembly by interacting with cellulose and affecting microfibril crystallinity. PMID:23990797

  18. Influence of wetting-layer wave functions on phonon-mediated carrier capture into self-assembled quantum dots

    DEFF Research Database (Denmark)

    Markussen, Troels; Kristensen, Philip Trøst; Tromborg, Bjarne

    2006-01-01

    Models of carrier dynamics in quantum dots rely strongly on adequate descriptions of the carrier wave functions. In this work we numerically solve the one-band effective mass Schrodinger equation to calculate the capture times of phonon-mediated carrier capture into self-assembled quantum dots...

  19. MrpB Functions as the Terminator for Assembly of Proteus mirabilis Mannose-Resistant Proteus-Like Fimbriae

    OpenAIRE

    Li, Xin; Mobley, Harry L. T.

    1998-01-01

    Insertional mutagenesis studies of mrpB, a putative pilin-encoding open reading frame of the mrp gene cluster, which encodes mannose-resistant Proteus-like (MR/P) fimbriae of Proteus mirabilis, indicate that MrpB functions as the terminator for fimbrial assembly.

  20. High-density assembly of chemiluminescence functionalized gold nanodots on multiwalled carbon nanotubes and their application as biosensing platforms.

    Science.gov (United States)

    Zhang, Hongli; Cui, Hua

    2014-03-07

    A one-step strategy was developed for high-density assembly of N-(aminobutyl)-N-(ethylisoluminol) (ABEI) functionalized gold nanodots onto the sidewalls of chitosan-grafted multiwalled carbon nanotubes (cs-MWCNTs) via the reduction of HAuCl4 with ABEI in the presence of cs-MWCNTs, resulting in novel hybrid nanomaterials with excellent chemiluminescence and electrochemiluminescence properties.

  1. Integrated Ugi-based assembly of functionally, skeletally, and stereochemically diverse 1,4-benzodiazepin-2-ones.

    Science.gov (United States)

    Azuaje, Jhonny; Pérez-Rubio, José M; Yaziji, Vicente; El Maatougui, Abdelaziz; González-Gomez, José Carlos; Sánchez-Pedregal, Víctor M; Navarro-Vázquez, Armando; Masaguer, Christian F; Teijeira, Marta; Sotelo, Eddy

    2015-02-06

    A practical, integrated and versatile U-4CR-based assembly of 1,4-benzodiazepin-2-ones exhibiting functionally, skeletally, and stereochemically diverse substitution patterns is described. By virtue of its convergence, atom economy, and bond-forming efficiency, the methodology documented herein exemplifies the reconciliation of structural complexity and experimental simplicity in the context of medicinal chemistry projects.

  2. Noncovalent assembly of functional groups on calix[4]arene molecular boxes

    NARCIS (Netherlands)

    Timmerman, P.; Vreekamp, R.H.; Vreekamp, Remko H.; Hulst, A.J.R.L.; Verboom, Willem; Reinhoudt, David; Rissanen, Kari; Udachin, Konstatin A.; Ripmeester, John

    1997-01-01

    Calix[4]arenes diametrically substituted at the upper rim with two melamine units spontaneously form well-defined box-like assemblies in the presence of two equivalents of 5,5-diethylbarbituric acid. These assemblies, consisting of nine different components, are held together by 36 hydrogen bonds

  3. Host ESCRT proteins are required for bromovirus RNA replication compartment assembly and function.

    Directory of Open Access Journals (Sweden)

    Arturo Diaz

    2015-03-01

    Full Text Available Positive-strand RNA viruses genome replication invariably is associated with vesicles or other rearranged cellular membranes. Brome mosaic virus (BMV RNA replication occurs on perinuclear endoplasmic reticulum (ER membranes in ~70 nm vesicular invaginations (spherules. BMV RNA replication vesicles show multiple parallels with membrane-enveloped, budding retrovirus virions, whose envelopment and release depend on the host ESCRT (endosomal sorting complexes required for transport membrane-remodeling machinery. We now find that deleting components of the ESCRT pathway results in at least two distinct BMV phenotypes. One group of genes regulate RNA replication and the frequency of viral replication complex formation, but had no effect on spherule size, while a second group of genes regulate RNA replication in a way or ways independent of spherule formation. In particular, deleting SNF7 inhibits BMV RNA replication > 25-fold and abolishes detectable BMV spherule formation, even though the BMV RNA replication proteins accumulate and localize normally on perinuclear ER membranes. Moreover, BMV ESCRT recruitment and spherule assembly depend on different sets of protein-protein interactions from those used by multivesicular body vesicles, HIV-1 virion budding, or tomato bushy stunt virus (TBSV spherule formation. These and other data demonstrate that BMV requires cellular ESCRT components for proper formation and function of its vesicular RNA replication compartments. The results highlight growing but diverse interactions of ESCRT factors with many viruses and viral processes, and potential value of the ESCRT pathway as a target for broad-spectrum antiviral resistance.

  4. Software and Process Developments in the Functionally Assembled Terrestrial Ecosystem Simulator (FATES)

    Science.gov (United States)

    Knox, R. G.; Koven, C.; Fisher, R.; Andre, B. J.; Bisht, G.; Vertenstein, M.; Riley, W. J.; Sacks, W.; Kluzek, E. B.; Lawrence, D. M.

    2016-12-01

    The Functionally Assembled Terrestrial Ecosystem Simulator (FATES) represents processes related to the demographics and dynamics of aboveground vegetation, often in an earth systems model context. It serves as a focal component of the Model-Experiment (MODEX) approach to the Next Generation Ecosystem Experiment (NGEE-Tropics). This is a tool to probe our understanding of the terrestrial carbon sink and forest response to a changing climate and human activities. It is co-developed with scientific measurement experiments that are designed specifically to improve our understanding of model process and parameterization. FATES is a successor of the Ecosystem Demography model, and had originally been coupled with the Community Land Model, ie CLM-ED. The work presented here describes refactoring to isolate the FATES code into a standalone module and create a well documented public API. The API allows FATES to be incorporated into a range of host models, such as the land models in ACME and CESM, and the ATS. Some newly developed model processes and testing strategies for verifying model results are presented as well.

  5. Reducing Staphylococcus aureus biofilm formation on stainless steel 316L using functionalized self-assembled monolayers.

    Science.gov (United States)

    Kruszewski, Kristen M; Nistico, Laura; Longwell, Mark J; Hynes, Matthew J; Maurer, Joshua A; Hall-Stoodley, Luanne; Gawalt, Ellen S

    2013-05-01

    Stainless steel 316L (SS316L) is a common material used in orthopedic implants. Bacterial colonization of the surface and subsequent biofilm development can lead to refractory infection of the implant. Since the greatest risk of infection occurs perioperatively, strategies that reduce bacterial adhesion during this time are important. As a strategy to limit bacterial adhesion and biofilm formation on SS316L, self-assembled monolayers (SAMs) were used to modify the SS316L surface. SAMs with long alkyl chains terminated with hydrophobic (-CH3) or hydrophilic (oligoethylene glycol) tail groups were used to form coatings and in an orthogonal approach, SAMs were used to immobilize gentamicin or vancomycin on SS316L for the first time to form an "active" antimicrobial coating to inhibit early biofilm development. Modified SS316L surfaces were characterized using surface infrared spectroscopy, contact angles, MALDI-TOF mass spectrometry and atomic force microscopy. The ability of SAM-modified SS316L to retard biofilm development by Staphylococcus aureus was functionally tested using confocal scanning laser microscopy with COMSTAT image analysis, scanning electron microscopy and colony forming unit analysis. Neither hydrophobic nor hydrophilic SAMs reduced biofilm development. However, gentamicin-linked and vancomycin-linked SAMs significantly reduced S. aureus biofilm formation for up to 24 and 48 h, respectively. Copyright © 2013 Elsevier B.V. All rights reserved.

  6. Synergistic Action of Actinoporin Isoforms from the Same Sea Anemone Species Assembled into Functionally Active Heteropores.

    Science.gov (United States)

    Rivera-de-Torre, Esperanza; García-Linares, Sara; Alegre-Cebollada, Jorge; Lacadena, Javier; Gavilanes, José G; Martínez-Del-Pozo, Álvaro

    2016-07-01

    Among the toxic polypeptides secreted in the venom of sea anemones, actinoporins are the pore-forming toxins whose toxic activity relies on the formation of oligomeric pores within biological membranes. Intriguingly, actinoporins appear as multigene families that give rise to many protein isoforms in the same individual displaying high sequence identities but large functional differences. However, the evolutionary advantage of producing such similar isotoxins is not fully understood. Here, using sticholysins I and II (StnI and StnII) from the sea anemone Stichodactyla helianthus, it is shown that actinoporin isoforms can potentiate each other's activity. Through hemolysis and calcein releasing assays, it is revealed that mixtures of StnI and StnII are more lytic than equivalent preparations of the corresponding isolated isoforms. It is then proposed that this synergy is due to the assembly of heteropores because (i) StnI and StnII can be chemically cross-linked at the membrane and (ii) the affinity of sticholysin mixtures for the membrane is increased with respect to any of them acting in isolation, as revealed by isothermal titration calorimetry experiments. These results help us understand the multigene nature of actinoporins and may be extended to other families of toxins that require oligomerization to exert toxicity. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

  7. Synergistic Action of Actinoporin Isoforms from the Same Sea Anemone Species Assembled into Functionally Active Heteropores*

    Science.gov (United States)

    Rivera-de-Torre, Esperanza; García-Linares, Sara; Alegre-Cebollada, Jorge; Lacadena, Javier; Gavilanes, José G.

    2016-01-01

    Among the toxic polypeptides secreted in the venom of sea anemones, actinoporins are the pore-forming toxins whose toxic activity relies on the formation of oligomeric pores within biological membranes. Intriguingly, actinoporins appear as multigene families that give rise to many protein isoforms in the same individual displaying high sequence identities but large functional differences. However, the evolutionary advantage of producing such similar isotoxins is not fully understood. Here, using sticholysins I and II (StnI and StnII) from the sea anemone Stichodactyla helianthus, it is shown that actinoporin isoforms can potentiate each other's activity. Through hemolysis and calcein releasing assays, it is revealed that mixtures of StnI and StnII are more lytic than equivalent preparations of the corresponding isolated isoforms. It is then proposed that this synergy is due to the assembly of heteropores because (i) StnI and StnII can be chemically cross-linked at the membrane and (ii) the affinity of sticholysin mixtures for the membrane is increased with respect to any of them acting in isolation, as revealed by isothermal titration calorimetry experiments. These results help us understand the multigene nature of actinoporins and may be extended to other families of toxins that require oligomerization to exert toxicity. PMID:27129251

  8. Water-Based Assembly of Polymer-Metal Organic Framework (MOF) Functional Coatings

    Energy Technology Data Exchange (ETDEWEB)

    De, Souvik [Artie McFerrin Department of Chemical Engineering, Texas A& M University, 77843-3122 TAMU College Station TX 77843-3122 USA; Nandasiri, Manjula I. [Environmental Molecular Sciences Laboratory (EMSL), Pacific Northwest National Laboratory, Richland WA 99352 USA; Schaef, Herbert T. [Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland WA 99352 USA; McGrail, Benard Peter [Energy & Environment Directorate, Pacific Northwest National Laboratory, 902 Battelle Boulevard Richland WA 99352 USA; Nune, Satish K. [Energy & Environment Directorate, Pacific Northwest National Laboratory, 902 Battelle Boulevard Richland WA 99352 USA; Lutkenhaus, Jodie L. [Artie McFerrin Department of Chemical Engineering, Texas A& M University, 77843-3122 TAMU College Station TX 77843-3122 USA; Department of Materials Science & Engineering, Texas A& M University, 3122 TAMU College Station TX 77843-3122 USA

    2016-12-27

    Metal organic frameworks (MOFs) have gained tremendous attention for their porosity, size selectivity, and structural diversity. There is a need for MOF-based coatings, particularly in applications such as separations, electronics and energy; yet forming thin, functional, conformal coatings is prohibitive because MOFs exist as a powder. Layer-by- layer assembly, a versatile thin film coating approach, offers a unique solution to this problem, but this approach requires MOFs that are water-dispersible and bear a surface charge. Here, we address these issues by examining water-based dispersions of MIL-101(Cr) that facilitate the formation of robust polymer-MOF hybrid coatings. Specifically, the substrate to be coated is alternately exposed to an aqueous solution of poly(styrene sulfonate) and dispersion MIL-101(Cr), yielding linear film growth and coatings with a MOF content as high as 77 wt%.This approach is surface-agnostic, in which the coating is successfully applied to silicon, glass, flexible plastic, and even cotton fabric, conformally coating individual fibers. In contrast, prior attempts at forming MOF-coatings were severely limited to a handful of surfaces, required harsh chemical treatment, and were not conformal. The approach presented here unambiguously confirms that MOFs can be conformally coated onto complex and unusual surfaces, opening the door for a wide variety of applications.

  9. DNA damage response and spindle assembly checkpoint function throughout the cell cycle to ensure genomic integrity.

    Directory of Open Access Journals (Sweden)

    Katherine S Lawrence

    2015-04-01

    Full Text Available Errors in replication or segregation lead to DNA damage, mutations, and aneuploidies. Consequently, cells monitor these events and delay progression through the cell cycle so repair precedes division. The DNA damage response (DDR, which monitors DNA integrity, and the spindle assembly checkpoint (SAC, which responds to defects in spindle attachment/tension during metaphase of mitosis and meiosis, are critical for preventing genome instability. Here we show that the DDR and SAC function together throughout the cell cycle to ensure genome integrity in C. elegans germ cells. Metaphase defects result in enrichment of SAC and DDR components to chromatin, and both SAC and DDR are required for metaphase delays. During persistent metaphase arrest following establishment of bi-oriented chromosomes, stability of the metaphase plate is compromised in the absence of DDR kinases ATR or CHK1 or SAC components, MAD1/MAD2, suggesting SAC functions in metaphase beyond its interactions with APC activator CDC20. In response to DNA damage, MAD2 and the histone variant CENPA become enriched at the nuclear periphery in a DDR-dependent manner. Further, depletion of either MAD1 or CENPA results in loss of peripherally associated damaged DNA. In contrast to a SAC-insensitive CDC20 mutant, germ cells deficient for SAC or CENPA cannot efficiently repair DNA damage, suggesting that SAC mediates DNA repair through CENPA interactions with the nuclear periphery. We also show that replication perturbations result in relocalization of MAD1/MAD2 in human cells, suggesting that the role of SAC in DNA repair is conserved.

  10. Fabrication of graphene thin films based on layer-by-layer self-assembly of functionalized graphene nanosheets.

    Science.gov (United States)

    Park, Je Seob; Cho, Sung Min; Kim, Woo-Jae; Park, Juhyun; Yoo, Pil J

    2011-02-01

    In this study, we present a facile means of fabricating graphene thin films via layer-by-layer (LbL) assembly of charged graphene nanosheets (GS) based on electrostatic interactions. To this end, graphite oxide (GO) obtained from graphite powder using Hummers method is chemically reduced to carboxylic acid-functionalized GS and amine-functionalized GS to perform an alternate LbL deposition between oppositely charged GSs. Specifically, for successful preparation of positively charged GS, GOs are treated with an intermediate acyl-chlorination reaction by thionyl chloride and a subsequent amidation reaction in pyridine, whereby a stable GO dispersibility can be maintained within the polar reaction solvent. As a result, without the aid of additional hybridization with charged nanomaterials or polyelectrolytes, the oppositely charged graphene nanosheets can be electrostatically assembled to form graphene thin films in an aqueous environment, while obtaining controllability over film thickness and transparency. Finally, the electrical property of the assembled graphene thin films can be enhanced through a thermal treatment process. Notably, the introduction of chloride functions during the acyl-chlorination reaction provides the p-doping effect for the assembled graphene thin films, yielding a sheet resistance of 1.4 kΩ/sq with a light transmittance of 80% after thermal treatment. Since the proposed method allows for large-scale production as well as elaborate manipulation of the physical properties of the graphene thin films, it can be potentially utilized in various applications, such as transparent electrodes, flexible displays and highly sensitive biosensors.

  11. Electronic Properties of Graphene Multilayers

    Science.gov (United States)

    Sadeghi, Hamed; de Rojas, Julius; Bill, Andreas

    2012-11-01

    We determine numerically the tight-binding band structure, the density of states and the plasmon spectrum of N stacked graphene layers beyond the Dirac cone approximation. We calculate the polarizability in the random phase approximation and determine the dielectric function ɛ(q,φ). This allows to determine the acoustic and optical modes of the plasmon spectrum. Because we do not limit ourselves to the Dirac cone approximation we cannot use the semi-analytic approach usually proposed for graphene in the literature. Instead we use a combination of numerical procedures to determine the collective modes of graphene multilayer.

  12. Still Heart Encodes a Structural HMT, SMYD1b, with Chaperone-Like Function during Fast Muscle Sarcomere Assembly.

    Directory of Open Access Journals (Sweden)

    Kendal Prill

    Full Text Available The vertebrate sarcomere is a complex and highly organized contractile structure whose assembly and function requires the coordination of hundreds of proteins. Proteins require proper folding and incorporation into the sarcomere by assembly factors, and they must also be maintained and replaced due to the constant physical stress of muscle contraction. Zebrafish mutants affecting muscle assembly and maintenance have proven to be an ideal tool for identification and analysis of factors necessary for these processes. The still heart mutant was identified due to motility defects and a nonfunctional heart. The cognate gene for the mutant was shown to be smyd1b and the still heart mutation results in an early nonsense codon. SMYD1 mutants show a lack of heart looping and chamber definition due to a lack of expression of heart morphogenesis factors gata4, gata5 and hand2. On a cellular level, fast muscle fibers in homozygous mutants do not form mature sarcomeres due to the lack of fast muscle myosin incorporation by SMYD1b when sarcomeres are first being assembled (19hpf, supporting SMYD1b as an assembly protein during sarcomere formation.

  13. Silver nanoparticle aided self-healing of polyelectrolyte multilayers.

    Science.gov (United States)

    Huang, Xiayun; Bolen, Matthew J; Zacharia, Nicole S

    2014-06-14

    Self-healing is the ability of a material to repair mechanical damage. The lifetime of a coating or film might be lengthened with this capacity. Water enabled self-healing of polyelectrolyte multilayers has been reported, using systems that grow via the interdiffusion of polyelectrolyte chains. Due to high mobility of the polyelectrolyte chains within the assembly, it is possible for lateral diffusion to heal over scratches. The influence of metal ions and nanoparticles on this property has, however, not been previously studied. Here we demonstrate that the incorporation of silver nanoparticles reduced in situ within the branched poly(ethyleneimine)-poly(acrylic acid) polyelectrolyte multilayer structure speeds the ability of the multilayer assembly to self-heal. This enhancement of property seems to not be due to changes in mechanical properties but rather in enhanced affinity to water and plasticization that enables the film to better swell.

  14. 'One-component' ultrathin multilayer films based on poly(vinyl alcohol) as stabilizing coating for phenytoin-loaded liposomes.

    Science.gov (United States)

    Zasada, Katarzyna; Łukasiewicz-Atanasov, Magdalena; Kłysik, Katarzyna; Lewandowska-Łańcucka, Joanna; Gzyl-Malcher, Barbara; Puciul-Malinowska, Agnieszka; Karewicz, Anna; Nowakowska, Maria

    2015-11-01

    Ultrathin "one-component" multilayer polymeric films for potential biomedical applications were designed based on polyvinyl alcohol,-a non-toxic, fully degradable synthetic polymer. Good uniformity of the obtained film and adequate adsorption properties of the polymeric layers were achieved by functional modification of the polymer, which involved synthesis of cationic and anionic derivatives. Synthesized polymers were characterized by FTIR, NMR spectroscopy, dynamic light scattering measurements and elemental analysis. The layer by layer assembly technique was used to build up a multilayer film and this process was followed using UV-Vis spectroscopy and ellipsometry. The morphology and thickness of the obtained multilayered film material was evaluated by atomic force microscopy (AFM). Preliminary studies on the application of the obtained multilayer film for coating of liposomal nanocarriers containing phenytoin, an antiarrhythmic drug, were performed. The coating effectively stabilizes liposomes and the effect increases with an increasing number of deposited layers until the polymeric film reaches the optimal thickness. The obtained release profiles suggest that bilayer-coated liposomes release phenytoin less rapidly than uncoated ones. The cytotoxicity studies performed for all obtained nanocarriers confirmed that none of them has negative effect on cell viability. All of the performed experiments suggest that liposomes coated with ultrathin film obtained from PVA derivatives can be attractive drug nanocarriers. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Base Metal Co-Fired Multilayer Piezoelectrics

    Directory of Open Access Journals (Sweden)

    Lisheng Gao

    2016-03-01

    Full Text Available Piezoelectrics have been widely used in different kinds of applications, from the automobile industry to consumer electronics. The novel multilayer piezoelectrics, which are inspired by multilayer ceramic capacitors, not only minimize the size of the functional parts, but also maximize energy efficiency. Development of multilayer piezoelectric devices is at a significant crossroads on the way to achieving low costs, high efficiency, and excellent reliability. Concerning the costs of manufacturing multilayer piezoelectrics, the trend is to replace the costly noble metal internal electrodes with base metal materials. This paper discusses the materials development of metal co-firing and the progress of integrating current base metal chemistries. There are some significant considerations in metal co-firing multilayer piezoelectrics: retaining stoichiometry with volatile Pb and alkaline elements in ceramics, the selection of appropriate sintering agents to lower the sintering temperature with minimum impact on piezoelectric performance, and designing effective binder formulation for low pO2 burnout to prevent oxidation of Ni and Cu base metal.

  16. Balancing spatially regulated β-actin translation and dynamin-mediated endocytosis is required to assemble functional epithelial monolayers.

    Science.gov (United States)

    Cruz, Lissette A; Vedula, Pavan; Gutierrez, Natasha; Shah, Neel; Rodriguez, Steven; Ayee, Brian; Davis, Justin; Rodriguez, Alexis J

    2015-12-01

    Regulating adherens junction complex assembly/disassembly is critical to maintaining epithelial homeostasis in healthy epithelial tissues. Consequently, adherens junction structure and function is often perturbed in clinically advanced tumors of epithelial origin. Some of the most studied factors driving adherens junction complex perturbation in epithelial cancers are transcriptional and epigenetic down-regulation of E-cadherin expression. However, numerous reports demonstrate that post-translational regulatory mechanisms such as endocytosis also regulate early phases of epithelial-mesenchymal transition and metastatic progression. In already assembled healthy epithelia, E-cadherin endocytosis recycles cadherin-catenin complexes to regulate the number of mature adherens junctions found at cell-cell contact sites. However, following de novo epithelial cell-cell contact, endocytosis negatively regulates adherens junction assembly by removing E-cadherin from the cell surface. By contrast, following de novo epithelial cell-cell contact, spatially localized β-actin translation drives cytoskeletal remodeling and consequently E-cadherin clustering at cell-cell contact sites and therefore positively regulates adherens junction assembly. In this report we demonstrate that dynamin-mediated endocytosis and β-actin translation-dependent cadherin-catenin complex anchoring oppose each other following epithelial cell-cell contact. Consequently, the final extent of adherens junction assembly depends on which of these processes is dominant following epithelial cell-cell contact. We expressed β-actin transcripts impaired in their ability to properly localize monomer synthesis (Δ3'UTR) in MDCK cells to perturb actin filament remodeling and anchoring, and demonstrate the resulting defect in adherens junction structure and function is rescued by inhibiting dynamin mediated endocytosis. Therefore, we demonstrate balancing spatially regulated β-actin translation and dynamin

  17. Controlled hydrophobic functionalization of natural fibers through self-assembly of amphiphilic diblock copolymer micelles.

    Science.gov (United States)

    Aarne, Niko; Laine, Janne; Hänninen, Tuomas; Rantanen, Ville; Seitsonen, Jani; Ruokolainen, Janne; Kontturi, Eero

    2013-07-01

    The functionalization of natural fibers is an important task that has recently received considerable attention. We investigated the formation of a hydrophobic layer from amphiphilic diblock copolymer micelles [polystyrene-block-poly(N-methyl-4-vinyl pyridinium iodide)] on natural fibers and on a model surface (mica). A series of micelles were prepared. The micelles were characterized by using cryoscopic TEM and light scattering, and their hydrophobization capability was studied through contact angle measurements, water adsorption, and Raman imaging. Mild heat treatment (130 °C) was used to increase the hydrophobization capability of the micelles. The results showed that the micelles could not hydrophobize a model surface, but could render the natural fibers water repellent both with and without heat treatment. This effect was systematically studied by varying the composition of the constituent blocks. The results showed that the micelle size (and the molecular weight of the constituent diblock copolymers) was the most important parameter, whereas the cationic (hydrophilic) part played only a minor role. We hypothesized that the hydrophobization effect could be attributed to a combination of the micelle size and the shrinkage of the natural fibers upon drying. The shrinking caused the roughness to increase on the fiber surface, which resulted in a rearrangement of the self- assembled layer in the wet state. Consequently, the fibers became hydrophobic through the roughness effects at multiple length scales. Mild heat treatment melted the micelle core and decreased the minimum size necessary for hydrophobization. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Photochemical CVD of Ru on functionalized self-assembled monolayers from organometallic precursors

    Science.gov (United States)

    Johnson, Kelsea R.; Arevalo Rodriguez, Paul; Brewer, Christopher R.; Brannaka, Joseph A.; Shi, Zhiwei; Yang, Jing; Salazar, Bryan; McElwee-White, Lisa; Walker, Amy V.

    2017-02-01

    Chemical vapor deposition (CVD) is an attractive technique for the metallization of organic thin films because it is selective and the thickness of the deposited film can easily be controlled. However, thermal CVD processes often require high temperatures which are generally incompatible with organic films. In this paper, we perform proof-of-concept studies of photochemical CVD to metallize organic thin films. In this method, a precursor undergoes photolytic decomposition to generate thermally labile intermediates prior to adsorption on the sample. Three readily available Ru precursors, CpRu(CO)2Me, (η3-allyl)Ru(CO)3Br, and (COT)Ru(CO)3, were employed to investigate the role of precursor quantum yield, ligand chemistry, and the Ru oxidation state on the deposition. To investigate the role of the substrate chemistry on deposition, carboxylic acid-, hydroxyl-, and methyl-terminated self-assembled monolayers were used. The data indicate that moderate quantum yields for ligand loss (φ ≥ 0.4) are required for ruthenium deposition, and the deposition is wavelength dependent. Second, anionic polyhapto ligands such as cyclopentadienyl and allyl are more difficult to remove than carbonyls, halides, and alkyls. Third, in contrast to the atomic layer deposition, acid-base reactions between the precursor and the substrate are more effective for deposition than nucleophilic reactions. Finally, the data suggest that selective deposition can be achieved on organic thin films by judicious choice of precursor and functional groups present on the substrate. These studies thus provide guidelines for the rational design of new precursors specifically for selective photochemical CVD on organic substrates.

  19. Reducing Staphylococcus aureus biofilm formation on stainless steel 316L using functionalized self-assembled monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Kruszewski, Kristen M., E-mail: kruszewskik@duq.edu [Duquesne University, Department of Chemistry and Biochemistry, 600 Forbes Avenue, Pittsburgh, PA 15282 (United States); Nistico, Laura, E-mail: lnistico@wpahs.org [Allegheny General Hospital, Center for Genomic Sciences, Allegheny-Singer Research Institute, 320 East North Avenue, 11th floor, South Tower, Pittsburgh, PA 15212 (United States); Longwell, Mark J., E-mail: mlongwel@wpahs.org [Allegheny General Hospital, Center for Genomic Sciences, Allegheny-Singer Research Institute, 320 East North Avenue, 11th floor, South Tower, Pittsburgh, PA 15212 (United States); Hynes, Matthew J., E-mail: mjhynes@go.wustl.edu [Washington University in St. Louis, Department of Chemistry, One Brookings Drive, St. Louis, MO 63130 (United States); Maurer, Joshua A., E-mail: maurer@wustl.edu [Washington University in St. Louis, Department of Chemistry, One Brookings Drive, St. Louis, MO 63130 (United States); Hall-Stoodley, Luanne, E-mail: L.Hall-Stoodley@soton.ac.uk [Southampton Wellcome Trust Clinical Research Facility/NIHR Respiratory BRU, University of Southampton Faculty of Medicine, Southampton General Hospital, Tremona Road, Southampton, Hampshire SO16 6YD (United Kingdom); Gawalt, Ellen S., E-mail: gawalte@duq.edu [Duquesne University, Department of Chemistry and Biochemistry, McGowan Institute for Regenerative Medicine, 600 Forbes Avenue, Pittsburgh, PA 15282 (United States)

    2013-05-01

    Stainless steel 316L (SS316L) is a common material used in orthopedic implants. Bacterial colonization of the surface and subsequent biofilm development can lead to refractory infection of the implant. Since the greatest risk of infection occurs perioperatively, strategies that reduce bacterial adhesion during this time are important. As a strategy to limit bacterial adhesion and biofilm formation on SS316L, self-assembled monolayers (SAMs) were used to modify the SS316L surface. SAMs with long alkyl chains terminated with hydrophobic (− CH{sub 3}) or hydrophilic (oligoethylene glycol) tail groups were used to form coatings and in an orthogonal approach, SAMs were used to immobilize gentamicin or vancomycin on SS316L for the first time to form an “active” antimicrobial coating to inhibit early biofilm development. Modified SS316L surfaces were characterized using surface infrared spectroscopy, contact angles, MALDI-TOF mass spectrometry and atomic force microscopy. The ability of SAM-modified SS316L to retard biofilm development by Staphylococcus aureus was functionally tested using confocal scanning laser microscopy with COMSTAT image analysis, scanning electron microscopy and colony forming unit analysis. Neither hydrophobic nor hydrophilic SAMs reduced biofilm development. However, gentamicin-linked and vancomycin-linked SAMs significantly reduced S. aureus biofilm formation for up to 24 and 48 h, respectively. - Highlights: ► SS316L was modified with glycol terminated SAMs in order to reduce biofilm growth. ► Antibiotics gentamicin and vancomycin were immobilized on SS316L via SAMs. ► Only the antibiotic modifications reduced biofilm development on SS316L.

  20. Self-assembly of aromatic-functionalized amphiphiles: The role and consequences of aromatic-aromatic noncovalent interactions in building supramolecular aggregates and novel assemblies

    Energy Technology Data Exchange (ETDEWEB)

    Whitten, D.G.; Chen, L.; Geiger, H.C.; Perlstein, J.; Song, X. [Los Alamos National Lab., NM (United States). Chemical Science and Technology Div.]|[Univ. of Rochester, NY (United States)

    1998-12-10

    This feature article presents an overview of a study of several different aromatic-functionalized amphiphiles-fatty acid and phospholipid derivatives. These amphiphiles form organized assemblies when the fatty acids are spread as monolayers at the air-water interface or when the phospholipids are dispersed in aqueous solutions. For a wide range of aromatic chromophores--trans-stilbene derivatives and a series of vinylogues (1,4-diphenyl-1,3-butadiene and 1,6-diphenyl-1,3,5-hexatriene), diphenylacetylenes, and azobenzenes such as phenyl, biphenyl, and terphenyl derivatives and modified stilbenes (styryl thiophenes and styryl naphthalenes)--assembly formation is accompanied by formation of aggregates of the aromatic groups. Results of experimental studies and simulations indicate that in many cases the aromatics form a small, stable unit aggregate characterized by strong noncovalent edge-to-face interactions among adjacent aromatics. Although the unit aggregates exhibit characteristic spectral shifts and strong induced circular dichroism indicating a chiral pinwheel aggregate structure, they may be packed together in pure films or dispersions to form an extended glide or herringbone structure. Although the pinwheel unit aggregate and the extended glide or herringbone structure. Although the pinwheel unit aggregate and the extended glide structure is favored for the majority of aromatics studied, for certain aromatics (styrenes, styrylthiophenes, and {alpha}-styrylnaphthalenes) a translation layer, characterized by face-to-face noncovalent interactions, is preferred. The glide or herringbone aggregates are readily distinguished from the translation aggregates by different spectral signatures and different photochemical and photophysical behavior. Factors controlling the type of aggregate and hence extended structure formed from different aromatic functionalized aromatics include shape and steric factors and strength of the competing noncovalent edge-face and face

  1. Controlling light with plasmonic multilayers

    DEFF Research Database (Denmark)

    Orlov, Alexey A.; Zhukovsky, Sergei; Iorsh, Ivan V.

    2014-01-01

    Recent years have seen a new wave of interest in layered media - namely, plasmonic multilayers - in several emerging applications ranging from transparent metals to hyperbolic metamaterials. In this paper, we review the optical properties of such subwavelength metal-dielectric multilayered...... metamaterials and describe their use for light manipulation at the nanoscale. While demonstrating the recently emphasized hallmark effect of hyperbolic dispersion, we put special emphasis to the comparison between multilayered hyperbolic metamaterials and more broadly defined plasmonic-multilayer metamaterials...

  2. Magnetic studies of Fe/Cu multilayers

    Energy Technology Data Exchange (ETDEWEB)

    El Khiraoui, S. [Laboratoire de Physique et Mecanique des Materiaux, Universite Sultan Moulay Slimane, FST de Beni-Mellal, B.P. 523, 23000 Beni-Mellal (Morocco); Sajieddine, M. [Laboratoire de Physique et Mecanique des Materiaux, Universite Sultan Moulay Slimane, FST de Beni-Mellal, B.P. 523, 23000 Beni-Mellal (Morocco)], E-mail: sajieddinem@yahoo.fr; Hehn, M.; Robert, S.; Lenoble, O.; Bellouard, C. [Laboratoire de Physique des Materiaux, UMR-CNRS 7556, B.P. 239, 54506 Vandoeuvre-les-Nancy Cedex (France); Sahlaoui, M. [Laboratoire de Physique et Mecanique des Materiaux, Universite Sultan Moulay Slimane, FST de Beni-Mellal, B.P. 523, 23000 Beni-Mellal (Morocco); Benkirane, K. [Laboratoire des Materiaux, Micro-electronique, Automatique et Thermique, Faculte des Sciences Ain-Chock, Universite Hassan II, B.P. 5366 Maarif, Casablanca (Morocco)

    2008-07-01

    The structural and magnetic properties of sputtered Fe/Cu multilayers are examined as a function of Fe layer thickness t{sub Fe} by means of X-ray diffraction, Moessbauer spectrometry and superconducting quantum interference magnetometer. The temperature dependence of the spontaneous magnetization M(T) is well described by a T{sup 3/2} law in all multilayers in the temperature range 5-300 K. The interface anisotropy constant of Fe/Cu multilayers, K{sub s}, is found to be 0.31 and 0.45 erg/cm{sup 2} at 5 and 300 K, respectively. A spin-wave theory has been used to explain the temperature dependence of the magnetization and the approximate values for the bulk exchange interaction J{sub b}, surface exchange interaction J{sub s} and the interlayer coupling strength J{sub I} for various Fe layer thicknesses have been obtained.

  3. Multilayer Social Networks

    DEFF Research Database (Denmark)

    Dickison, Mark; Magnani, Matteo; Rossi, Luca

    Multilayer networks, in particular multilayer social networks, where users belong to and interact on different networks at the same time, are an active research area in social network analysis, computer science, and physics. These networks have traditionally been studied within these separate...... social network systems, the evolution of interconnected social networks, and dynamic processes such as information spreading. A single real dataset is used to illustrate the concepts presented throughout the book, demonstrating both the practical utility and the potential shortcomings of the various...

  4. Multilayer Social Networks

    DEFF Research Database (Denmark)

    Dickison, Mark; Magnani, Matteo; Rossi, Luca

    social network systems, the evolution of interconnected social networks, and dynamic processes such as information spreading. A single real dataset is used to illustrate the concepts presented throughout the book, demonstrating both the practical utility and the potential shortcomings of the various...... research communities, leading to the development of several independent models and methods to deal with the same set of problems. This book unifies and consolidates existing practical and theoretical knowledge on multilayer networks including data collection and analysis, modeling, and mining of multilayer...

  5. Langmuir Blodgett multilayers and related nanostructures

    Indian Academy of Sciences (India)

    Langmuir Blodgett (LB) process is an important route to the development of organized molecular layered structures of a variety of organic molecules with suitably designed architecture and functionality. LB multilayers have also been used as templates and precursors to develop nano-structured thin films. In this article ...

  6. Structure, Function, Self-Assembly and Origin of Simple Membrane Proteins

    Science.gov (United States)

    Pohorille, Andrew

    2003-01-01

    Integral membrane proteins perform such essential cellular functions as transport of ions, nutrients and waste products across cell walls, transduction of environmental signals, regulation of cell fusion, recognition of other cells, energy capture and its conversion into high-energy compounds. In fact, 30-40% of genes in modem organisms codes for membrane proteins. Although contemporary membrane proteins or their functional assemblies can be quite complex, their transmembrane fragments are usually remarkably simple. The most common structural motif for these fragments is a bundle of alpha-helices, but occasionally it could be a beta-barrel. In a series of molecular dynamics computer simulations we investigated self-organizing properties of simple membrane proteins based on these structural motifs. Specifically, we studied folding and insertion into membranes of short, nonpolar or amphiphatic peptides. We also investigated glycophorin A, a peptide that forms sequence-specific dimers, and a transmembrane aggregate of four identical alpha-helices that forms an efficient and selective voltage-gated proton channel was investigated. Many peptides are attracted to water-membrane interfaces. Once at the interface, nonpolar peptides spontaneously fold to a-helices. Whenever the sequence permits, peptides that contain both polar and nonpolar amino also adopt helical structures, in which polar and nonpolar amino acid side chains are immersed in water and membrane, respectively. Specific identity of side chains is less important. Helical peptides at the interface could insert into the membrane and adopt a transmembrane conformation. However, insertion of a single helix is unfavorable because polar groups in the peptide become completely dehydrated upon insertion. The unfavorable free energy of insertion can be regained by spontaneous association of peptides in the membrane. The first step in this process is the formation of dimers, although the most common are aggregates of 4

  7. Electrochemistry of ATP-capped silver nanoparticles in layer-by-layer multilayer films

    Science.gov (United States)

    Singh, Poonam; Solomon, Virgil C.; Buttry, Daniel A.

    2014-07-01

    Colloidal silver nanoparticles (Ag NPs) capped with adenosine triphosphate (ATP) were prepared using borohydride reduction of Ag+ in the presence of ATP. Subsequent characterization was done using transmission electron microscopy/high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, and non-contact atomic force microscopy (NcAFM) confirming the size and composition of the Ag NPs. This report focuses on two topics: (1) the change in NP size and properties as a function of molar ratios of Ag+ to ATP capping ligand to BH4 - reductant, and (2) the electrochemical behavior of the NPs in layer-by-layer (LbL) multilayer films. On the basis of electrostatic interaction between negatively charged phosphate groups on Ag NPs and positively charged poly(diallyldimethylammonium) hydrochloride, NPs were immobilized on 3-mercaptopropionic acid (MCP)-functionalized gold electrodes using LbL assembly method followed by characterization of the film using NcAFM. Furthermore, the redox chemistry for phase transformations of immobilized Ag NPs to AgCl or Ag2O in multilayer films was examined using cyclic voltammetry (CV) in NaOH and NaCl solutions. A non-linear increase of charge with an increase in the number of bilayers in the film was observed up to five layers. Underpotential deposition of Pb on multilayer film of Ag NPs confirmed the presence of Ag in multilayer films. The stability of the LbL film toward electrochemical cycling to higher potentials (i.e., +0.8 V) in NaOH solutions was evaluated.

  8. Towards functional bionanomaterials based on self-assembling cyclic peptide nanotubes.

    Science.gov (United States)

    Brea, Roberto J; Reiriz, César; Granja, Juan R

    2010-05-01

    In recent years, considerable effort has been devoted to the preparation of artificial nanotubular materials. One of the most successful approaches for the construction of noncovalently bonded nanotube entities is the self-assembly of cyclic polypeptides in stacks that are stabilized by hydrogen bonds. This tutorial review covers the history and current situation for synthetic organic nanostructures obtained from self-assembling cyclic peptides. In particular, we describe the evolution to cyclic peptides that not only allow the modification of the outer surface but also the inner cavity by paying special attention to peptide rings that contain cyclic gamma-amino acids. In this respect, we describe the synthesis, properties and application of a new class of homo- and heterodimeric supramolecular assemblies that are precursors of cyclic alpha,gamma-peptide nanotubes.

  9. Pre-initiation complex assembly functions as a molecular switch that splits the Mcm2-7 double hexamer.

    Science.gov (United States)

    Miyazawa-Onami, Mayumi; Araki, Hiroyuki; Tanaka, Seiji

    2017-10-01

    Initiation of chromosomal DNA replication in eukaryotes involves two steps: licensing and firing. In licensing, a core component of the replicative helicase, the Mcm2-7 complex, is loaded onto replication origins as an inactive double hexamer, which is activated in the firing step by firing factors. A reaction intermediate called the pre-initiation complex (pre-IC) has been proposed to assemble transiently during firing, but the existence of the pre-IC has not yet been confirmed. Here, we show, by systematic chromatin immunoprecipitation, that a distinct intermediate that fits the definition of the pre-IC assembles during firing in the budding yeast Saccharomyces cerevisiae Pre-IC assembly is observed in the absence of Mcm10, one of the firing factors, and is mutually dependent on all the firing factors whose association to replication origins is triggered by cyclin-dependent kinase. In the pre-IC, the Mcm2-7 double hexamer is separated into single hexamers, as in the active helicase. Our data indicate that pre-IC assembly functions as an all-or-nothing molecular switch that splits the Mcm2-7 double hexamer. © 2017 The Authors.

  10. First-principles investigation of the structural and electronic properties of self-assemblies of functional molecules on graphene

    Science.gov (United States)

    Quesne-Turin, Ambroise; Touzeau, Jeremy; Dappe, Yannick J.; Diawara, Boubakar; Maurel, François; Seydou, Mahamadou

    2017-05-01

    Graphene-based two-dimensional materials have attracted an increasing attention these last years. Among them, the system formed by molecular adsorption on, aim of modifying the conductivity of graphene and make it semiconducting, is of particular interest. We use here hierarchical first-principles simulations to investigate the energetic and electronic properties of an electron-donor, melamine, and an acceptor, NaphtaleneTetraCarboxylic DiImide (NTCDI), and the assembly of their complexes on graphene surface. In particular, the van der Waals-corrected density functional theory (DFT) method is used to compute the interaction and adsorption energies during assembly. The effect of dispersion interactions on both geometries and energies is investigated. Depending on the surface coverage and the molecular organization, there is a significant local deformation of the graphene surface. Self-assembly is driven by the competition between hydrogen bonds in the building blocks and their adsorption on the surface. The dispersion contribution accounts significantly in both intermolecular and adsorption energies. The electron transfer mechanism and density of states (DOS) calculations show the electron-donor and acceptor characters of melamine and NTCDI, respectively. Molecular adsorption affects differently the energy levels around the Fermi level differently, leading to band gap opening. These results provide information about the new materials obtained by controlling molecular assembly on graphene.

  11. Identifying key nodes in multilayer networks based on tensor decomposition

    Science.gov (United States)

    Wang, Dingjie; Wang, Haitao; Zou, Xiufen

    2017-06-01

    The identification of essential agents in multilayer networks characterized by different types of interactions is a crucial and challenging topic, one that is essential for understanding the topological structure and dynamic processes of multilayer networks. In this paper, we use the fourth-order tensor to represent multilayer networks and propose a novel method to identify essential nodes based on CANDECOMP/PARAFAC (CP) tensor decomposition, referred to as the EDCPTD centrality. This method is based on the perspective of multilayer networked structures, which integrate the information of edges among nodes and links between different layers to quantify the importance of nodes in multilayer networks. Three real-world multilayer biological networks are used to evaluate the performance of the EDCPTD centrality. The bar chart and ROC curves of these multilayer networks indicate that the proposed approach is a good alternative index to identify real important nodes. Meanwhile, by comparing the behavior of both the proposed method and the aggregated single-layer methods, we demonstrate that neglecting the multiple relationships between nodes may lead to incorrect identification of the most versatile nodes. Furthermore, the Gene Ontology functional annotation demonstrates that the identified top nodes based on the proposed approach play a significant role in many vital biological processes. Finally, we have implemented many centrality methods of multilayer networks (including our method and the published methods) and created a visual software based on the MATLAB GUI, called ENMNFinder, which can be used by other researchers.

  12. Emission properties of colloidal quantum dots on polyelectrolyte multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Komarala, Vamsi K [Semiconductor Photonics Group, School of Physics, Trinity College Dublin (Ireland); Rakovich, Yury P [Semiconductor Photonics Group, School of Physics, Trinity College Dublin (Ireland); Bradley, A Louise [Semiconductor Photonics Group, School of Physics, Trinity College Dublin (Ireland); Byrne, Stephen J [School of Chemistry, Trinity College Dublin, Republic of (Ireland); Corr, Serena A [School of Chemistry, Trinity College Dublin, Republic of (Ireland); Gun' ko, Yurii K [School of Chemistry, Trinity College Dublin (Ireland)

    2006-08-28

    We present steady state and time-resolved photoluminescence (PL) characteristics of differently charged CdTe quantum dots (QDs) adsorbed onto a polyelectrolyte (PE) multilayer. The PE multilayer is built up using a layer-by-layer assembly technique. We find that the diffusion of the QDs into the PE multilayer is an important factor in the case of 3-mercapto-1, 2-propanediol stabilized QDs (neutral surface charge), resulting in a {approx}31-fold enhancement in PL intensity accompanied by a blue shift in the PL spectra and an increase in decay lifetime from 3.74 ns to a maximum of 11.65 ns. These modified emission properties are attributed to the enhanced surface related emission resulting from the interaction of the QD's surface with the PE. We find that diffusion does not occur for thioglycolic acid (TGA) stabilized QDs (negative surface charge) or 2-mercaptoethylamine stabilized QDs (positive surface charge), indicating localization of the QDs on top of the PE multilayer. However, the PL lifetime of the TGA stabilized QDs decreases from 9.58 to 5.78 ns with increasing PE multilayer thickness. This provides evidence for increased intrinsic exciton recombination relative to surface related emission, which results in an overall reduction in the average lifetime. Our studies indicate the importance of the QD surface charge in determining the interaction with the PE multilayers and the subsequent modification of the QD emission properties.

  13. Stable MCC binding to the APC/C is required for a functional spindle assembly checkpoint

    DEFF Research Database (Denmark)

    Hein, Jamin B; Nilsson, Jakob

    2014-01-01

    The spindle assembly checkpoint (SAC) delays progression into anaphase until all chromosomes have aligned on the metaphase plate by inhibiting Cdc20, the mitotic co-activator of the APC/C. Mad2 and BubR1 bind and inhibit Cdc20, thereby forming the mitotic checkpoint complex (MCC), which can bind...

  14. Artificial muscle-like function from hierarchical supramolecular assembly of photoresponsive molecular motors.

    Science.gov (United States)

    Chen, Jiawen; Leung, Franco King-Chi; Stuart, Marc C A; Kajitani, Takashi; Fukushima, Takanori; van der Giessen, Erik; Feringa, Ben L

    2018-02-01

    A striking feature of living systems is their ability to produce motility by amplification of collective molecular motion from the nanoscale up to macroscopic dimensions. Some of nature's protein motors, such as myosin in muscle tissue, consist of a hierarchical supramolecular assembly of very large proteins, in which mechanical stress induces a coordinated movement. However, artificial molecular muscles have often relied on covalent polymer-based actuators. Here, we describe the macroscopic contractile muscle-like motion of a supramolecular system (comprising 95% water) formed by the hierarchical self-assembly of a photoresponsive amphiphilic molecular motor. The molecular motor first assembles into nanofibres, which further assemble into aligned bundles that make up centimetre-long strings. Irradiation induces rotary motion of the molecular motors, and propagation and accumulation of this motion lead to contraction of the fibres towards the light source. This system supports large-amplitude motion, fast response, precise control over shape, as well as weight-lifting experiments in water and air.

  15. Chaplins of Streptomyces coelicolor self-assemble into two distinct functional amyloids

    NARCIS (Netherlands)

    Bokhove, Marcel; Claessen, Dennis; de Jong, Wouter; Dijkhuizen, Lubbert; Boekema, Egbert J.; Oostergetel, Gert T.

    2013-01-01

    Chaplins are small, secreted proteins of streptomycetes that play instrumental roles in the formation of aerial hyphae and attachment of hyphae to surfaces. Here we show that the purified proteins self-assemble at a water/air interface into an asymmetric and amphipathic protein membrane that has an

  16. Mouse Sycp1 functions in synaptonemal complex assembly, meiotic recombination., and XY body formation

    NARCIS (Netherlands)

    Vries, de F.A.T.; Boer, de E.; Bosch, M.; Baarends, W.M.; Ooms, M.; Yuan, L.; Liu, J.G.; Zeeland, van A.A.; Heyting, C.; Pastink, A.

    2005-01-01

    In meiotic prophase, synaptonemal complexes (SCs) closely appose homologous chromosomes (homologs) along their length. SCs are assembled from two axial elements (AEs), one along each homolog, which are connected by numerous transverse filaments (TFs). We disrupted the mouse gene encoding TF protein

  17. Formation of functional super-helical assemblies by constrained single heptad repeat

    Science.gov (United States)

    Mondal, Sudipta; Adler-Abramovich, Lihi; Lampel, Ayala; Bram, Yaron; Lipstman, Sophia; Gazit, Ehud

    2015-10-01

    Inspired by the key role of super-helical motifs in molecular self-organization, several tandem heptad repeat peptides were used as building blocks to form well-ordered supramolecular nano-assemblies. However, the need for stable helical structures limits the length of the smallest described units to three heptad repeats. Here we describe the first-ever self-assembling single heptad repeat module, based on the ability of the non-coded α-aminoisobutyric acid to stabilize very short peptides in helical conformation. A conformationally constrained peptide comprised of aromatic, but not aliphatic, residues, at the first and fourth positions formed helical fibrillar assemblies. Single crystal X-ray analysis of the peptide demonstrates super-helical packing in which phenylalanine residues formed an `aromatic zipper' arrangement at the molecular interface. The modification of the minimal building block with positively charged residues results in tight DNA binding ascribed to the combined factors of helicity, hydrophobicity and charge. The design of these peptides defines a new direction for assembly of super-helical nanostructures by minimal molecular elements.

  18. Directed assembly of functional light harvesting antenna complexes onto chemically patterned surfaces

    NARCIS (Netherlands)

    Escalante Marun, M.; Maury, P.A.; Bruinink, C.M.; van der Werf, Kees; Olsen, John D.; Timney, A.; Huskens, Jurriaan; Hunter, C. Neil; Subramaniam, Vinod; Otto, Cornelis

    2008-01-01

    We report the directed assembly of the photosynthetic membrane proteins LH1 and LH2 isolated from the purple bacterium Rhodobacter sphaeroides onto chemically patterned substrates. Nanoimprint lithography was used to pattern discrete regions of amino- and fluoro-terminated or poly(ethylene glycol)

  19. RNA-seq analysis of Quercus pubescens Leaves: de novo transcriptome assembly, annotation and functional markers development.

    Directory of Open Access Journals (Sweden)

    Sara Torre

    Full Text Available Quercus pubescens Willd., a species distributed from Spain to southwest Asia, ranks high for drought tolerance among European oaks. Q. pubescens performs a role of outstanding significance in most Mediterranean forest ecosystems, but few mechanistic studies have been conducted to explore its response to environmental constrains, due to the lack of genomic resources. In our study, we performed a deep transcriptomic sequencing in Q. pubescens leaves, including de novo assembly, functional annotation and the identification of new molecular markers. Our results are a pre-requisite for undertaking molecular functional studies, and may give support in population and association genetic studies. 254,265,700 clean reads were generated by the Illumina HiSeq 2000 platform, with an average length of 98 bp. De novo assembly, using CLC Genomics, produced 96,006 contigs, having a mean length of 618 bp. Sequence similarity analyses against seven public databases (Uniprot, NR, RefSeq and KOGs at NCBI, Pfam, InterPro and KEGG resulted in 83,065 transcripts annotated with gene descriptions, conserved protein domains, or gene ontology terms. These annotations and local BLAST allowed identify genes specifically associated with mechanisms of drought avoidance. Finally, 14,202 microsatellite markers and 18,425 single nucleotide polymorphisms (SNPs were, in silico, discovered in assembled and annotated sequences. We completed a successful global analysis of the Q. pubescens leaf transcriptome using RNA-seq. The assembled and annotated sequences together with newly discovered molecular markers provide genomic information for functional genomic studies in Q. pubescens, with special emphasis to response mechanisms to severe constrain of the Mediterranean climate. Our tools enable comparative genomics studies on other Quercus species taking advantage of large intra-specific ecophysiological differences.

  20. Synthesis and Study of Molecular Assemblies Formed by 4,6-O-(2-Phenylethylidene)-Functionalized d-Glucosamine Derivatives.

    Science.gov (United States)

    Chen, Anji; Adhikari, Surya B; Mays, Kellie; Wang, Guijun

    2017-08-15

    Low-molecular-weight gelators are interesting small molecules with potential applications as advanced materials. Carbohydrate-based small molecular gelators are especially useful because they are derived from renewable resources and are more likely to be biocompatible and biodegradable. Various 4,6-benzylidene acetal protected α-methyl 2-d-glucosamine derivatives have been found to be effective low-molecular-weight gelators. To understand the influence of the 4,6-benzylidene acetal functional group toward molecular self-assembly and to obtain effective molecular gelators, we synthesized and analyzed a new series of d-glucosamine derivatives in which the phenyl group of the acetal is replaced by a benzyl group. The homologation of the acetal protection from aromatic to aliphatic functional groups allows us to probe the effect of increasing structural flexibility on molecular self-assembly and gelation. In this study, nine representative amides and nine urea analogs were synthesized, and their gelation properties were analyzed in a series of organic solvents and aqueous solutions. The resulting amide and urea derivatives are versatile organogelators forming gels in toluene, ethanol, isopropanol, ethylene glycol, and aqueous mixtures of organic solvents. More interestingly, the amide analogs are also effective gelators for pump oil and engine oil. NMR spectroscopy at variable temperatures was used to analyze the molecular assemblies and intermolecular forces. The selected gelators with several drug and dye molecules in DMSO and water were studied for their effectiveness of encapsulation and release of these agents.

  1. A reproducible SERS substrate based on electrostatically assisted APTES-functionalized surface-assembly of gold nanostars.

    Science.gov (United States)

    Su, Qianqian; Ma, Xiaoyuan; Dong, Jian; Jiang, Caiyun; Qian, Weiping

    2011-06-01

    A SERS active gold nanostar layer on the surface of ITO glass slip has been prepared by a low-cost electrostatically assisted APTES-functionalized surface-assembly method for SERS analysis. The two-dimensional morphology of the SERS substrate was examined by scanning electron microscopy. Comparative analysis revealed that the optical characteristics and SERS efficiency of these substrates varied as a function of nanostar morphology. It was found that the substrate assembled with the longest branches of nanostars generated the best SERS efficiency, whether the excitation source is 785 or 633 nm. The potential use of these substrates in detection applications was also investigated by using Nile blue A and Rhodamine 6G. The detection limits are 5 × 10(-11) M and 1 × 10(-9) M, respectively, when using the 785 nm excitation source. Apart from this high enhancement effect, the substrate here also shows extremely good reproducibility at the same time. All of these indicate that gold nanostars are a very good structure for SERS substrate assembly. © 2011 American Chemical Society

  2. Fluorescence turn-on recognition of chiral amino acids using dye incorporated β-CD functionalized AuNPs assembly

    Energy Technology Data Exchange (ETDEWEB)

    Aswathy, B., E-mail: aswathybv@gmail.com; Sony, G., E-mail: emailtosony@gmail.com

    2014-10-15

    An assembly of dye incorporated β-cyclodextrin (βCD) functionalized AuNPs for the fluorescent probing of chiral amino acids is presented. Gold nanoparticles (AuNPs) possessing a high extinction coefficient function can be used as excellent fluorescent quenchers in AuNP–fluorophore system. Inclusion of fluorescein (FL) into β-cyclodextrin (βCD) makes energy transfer to occur through the donor and quencher nearby. This energy transfer switches off by virtue of the analyte induced release of FL from β-CD cavity, which results in the fluorescence recovery of the quenched dye. Analysis suggests that the assembly of AuNPs–βCDs–FL is effective as a turn-on fluorescent probe for the chiroselective optical discrimination between D,L-tryptophan, D,L-phenyl alanine and D,L-tyrosine. The detection limits for analyzing L-tryptophan, L-phenyl alanine and L-tyrosine were found to be 0.59, 1.2 and 1.5 μM respectively. - Highlights: • Fluorescence quenching AuNP–βCD–dye assembly via energy transfer. • Energy transfer from dye to AuNPs is a SET process. • Fluorescence turn-on detection of amino acids by the competitive binding method. • Chiroselective discrimination between enantiomeric amino acids.

  3. A biomimetic colorimetric logic gate system based on multi-functional peptide-mediated gold nanoparticle assembly.

    Science.gov (United States)

    Li, Yong; Li, Wang; He, Kai-Yu; Li, Pei; Huang, Yan; Nie, Zhou; Yao, Shou-Zhuo

    2016-04-28

    In natural biological systems, proteins exploit various functional peptide motifs to exert target response and activity switch, providing a functional and logic basis for complex cellular activities. Building biomimetic peptide-based bio-logic systems is highly intriguing but remains relatively unexplored due to limited logic recognition elements and complex signal outputs. In this proof-of-principle work, we attempted to address these problems by utilizing multi-functional peptide probes and the peptide-mediated nanoparticle assembly system. Here, the rationally designed peptide probes function as the dual-target responsive element specifically responsive to metal ions and enzymes as well as the mediator regulating the assembly of gold nanoparticles (AuNPs). Taking advantage of Zn2+ ions and chymotrypsin as the model inputs of metal ions and enzymes, respectively, we constructed the peptide logic system computed by the multi-functional peptide probes and outputted by the readable colour change of AuNPs. In this way, the representative binary basic logic gates (AND, OR, INHIBIT, NAND, IMPLICATION) have been achieved by delicately coding the peptide sequence, demonstrating the versatility of our logic system. Additionally, we demonstrated that the three-input combinational logic gate (INHIBIT-OR) could also be successfully integrated and applied as a multi-tasking biosensor for colorimetric detection of dual targets. This nanoparticle-based peptide logic system presents a valid strategy to illustrate peptide information processing and provides a practical platform for executing peptide computing or peptide-related multiplexing sensing, implying that the controllable nanomaterial assembly is a promising and potent methodology for the advancement of biomimetic bio-logic computation.

  4. Structure and function of Enterotoxigenic Escherichia coli fimbriae from differing assembly pathways

    CERN Document Server

    Mortezaei, Narges; Shao, Paul P; Shirdel, Mariam; Singh, Bhupender; McVeigh, Annette; Uhlin, Bernt Eric; Savarino, Stephen J; Andersson, Magnus; Bullitt, Esther

    2014-01-01

    Pathogenic enterotoxigenic Escherichia coli (ETEC) are the major bacterial cause of diarrhea in young children in developing countries and in travelers, causing significant mortality in children. Adhesive fimbriae are a prime virulence factor for ETEC, initiating colonization of the small intestinal epithelium. Similar to other Gram-negative bacteria, ETEC express one or more diverse fimbriae, some assembled by the chaperone-usher pathway and others by the alternate chaperone pathway. Here we elucidate structural and biophysical aspects and adaptations of each fimbrial type to its respective host niche. CS20 fimbriae are compared to CFA/I fimbriae, which are two ETEC fimbriae assembled via different pathways, and to Pfimbriae from uropathogenic E. coli. Many fimbriae unwind from their native helical filament to an extended linear conformation under force, thereby sustaining adhesion by reducing load at the point of contact between the bacterium and the target cell. CFA/I fimbriae require the least force to un...

  5. Reducing Staphylococcus aureus biofilm formation on stainless steel 316L using functionalized self-assembled monolayers

    OpenAIRE

    Kruszewski, Kristen M; Nistico, Laura; Longwell, Mark J.; Hynes, Matthew J.; Maurer, Joshua A.; Hall-Stoodley, Luanne; Gawalt, Ellen S.

    2013-01-01

    Stainless steel 316L (SS316L) is a common material used in orthopedic implants. Bacterial colonization of the surface and subsequent biofilm development can lead to refractory infection of the implant. Since the greatest risk of infection occurs perioperatively, strategies that reduce bacterial adhesion during this time are important. As a strategy to limit bacterial adhesion and biofilm formation on SS316L, self-assembled monolayers (SAMs) were used to modify the SS316L surface. SAMs with lo...

  6. Fabrication, characterization, and biological assessment of multilayer laminin γ2 DNA coatings on titanium surfaces

    Science.gov (United States)

    Yang, Guoli; Zhang, Jing; Dong, Wenjing; Liu, Li; Shi, Jue; Wang, Huiming

    2016-01-01

    The purpose of this work was to fabricate a multilayer laminin γ2 DNA coating on a titanium surface and evaluate its biological properties. A multilayer laminin γ2 DNA coating was fabricated on titanium using a layer-by-layer assembly technique. The rate of coating degradation was evaluated by detecting the amount of cDNA remaining. Surface analysis using X-ray photoelectron spectroscopy, atomic force microscopy, and surface contact angle measurements revealed the multilayer structure to consist of cationic lipid and confirmed that a laminin γ2 DNA layer could be fabricated on titanium via the layer-by-layer assembly process. The transfection efficiency was highest for five layers in the multilayer structure. HEK293 cells cultured on the multilayer films displayed significantly higher adhesion activity than the control group. The expression of laminin γ2 and the co-localization of integrin β4 and plectin were more obvious in HN4 cells cultured on the multilayer laminin γ2 DNA coating, while weak immunoreactivities were observed in the control group. We concluded that the DNA-loaded multilayer provided a surface with good biocompatibility and that the multilayer laminin γ2 DNA coating might be effective in improving cell adhesion and the formation of hemidesmosomes on titanium surfaces. PMID:26996815

  7. Preparation, characterization and properties of amino-functionalized montmorillonite and composite layer-by-layer assembly with inorganic nanosheets

    Science.gov (United States)

    Huang, Guo-bo; Ge, Chang-hua; He, Bing-jing

    2011-06-01

    An amino-functionalized montmorillonite (APTMS-MMT) was prepared by the grafting of 3-aminopropyltrimethoxysilane (APTMS) on the surface of MMT via the ultrasonic synthesis process and characterized by a variety of techniques: FT-IR, thermogravimetic analysis (TGA), particles size analysis and ζ-potential measurement. The results showed the size and size distribution of APTMS-MMT particles were decreased, and the ζ-potential of particles was increased obviously via the ultrasonic synthesis process. The particles of 30% APTMS-MMT US (MMT modified with 30 wt% APTMS with ultrasonic synthesis process) had a z-average diameter of about 500 nm and a polydispersity index of 0.2. The resultant 30% APTMS-MMT US was dispersed uniformly and stably in water. The poly(acrylic acid) (PAA)/APTMS-MMT multilayer films were grown through layer-by-layer (LBL) deposition of PAA and APTMS-MMT. SEM results indicated that the ultrasonic synthesis of APTMS-MMT increased dispersability of clay sheets at high loadings. The thermal stability and mechanical properties of PAA/APTMS-MMT composites were investigated by TGA and tensile test respectively. The results showed the ultrasonic synthesis of APTMS-MMT enhanced the thermal stability and mechanical properties of PAA/APTMS-MMT composites significantly. PAA/30% APTMS-MMT US composite displayed 3 times higher strength and 6 times higher Young's modulus when compared with pure PAA polymer.

  8. Multilayer Optical Learning Networks

    Science.gov (United States)

    Wagner, Kelvin; Psaltis, Demetri

    1987-08-01

    In this paper we present a new approach to learning in a multilayer optical neural network which is based on holographically interconnected nonlinear Fabry-Perot etalons. The network can learn the interconnections that form a distributed representation of a desired pattern transformation operation. The interconnections are formed in an adaptive and self aligning fashion, as volume holographic gratings in photorefractive crystals. Parallel arrays of globally space integrated inner products diffracted by the interconnecting hologram illuminate arrays of nonlinear Fabry-Perot etalons for fast thresholding of the transformed patterns. A phase conjugated reference wave interferes with a backwards propagating error signal to form holographic interference patterns which are time integrated in the volume of the photorefractive crystal in order to slowly modify and learn the appropriate self aligning interconnections. A holographic implementation of a single layer perceptron learning procedure is presented that can be extendept ,to a multilayer learning network through an optical implementation of the backward error propagation (BEP) algorithm.

  9. Self-Assembled Functional Nanostructure of Plasmid DNA with Ionic Liquid [Bmim][PF₆]: Enhanced Efficiency in Bacterial Gene Transformation.

    Science.gov (United States)

    Soni, Sarvesh K; Sarkar, Sampa; Mirzadeh, Nedaossadat; Selvakannan, P R; Bhargava, Suresh K

    2015-04-28

    The electrostatic interaction between the negatively charged phosphate groups of plasmid DNA and the cationic part of hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6]), initiates spontaneous self-assembly to form the functional nanostructures made up of DNA and ionic liquid (IL). These functional nanostructures were demonstrated as promising synthetic nonviral vectors for the efficient bacterial pGFP gene transformation in cells. In particular, the functional nanostructures that were made up of 1 μL of IL ([Bmim][PF6]) and 1 μg of plasmid DNA can increase the transformation efficiency by 300-400% in microbial systems, without showing any toxicity for E. coli DH5α cells. (31)P nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron (XPS) spectroscopic analysis revealed that the electrostatic interaction between negatively charged phosphate oxygen and cationic Bmim(+) tends to initiate the self-assembly process. Thermogravimetric analysis of the DNA-IL functional nanostructures showed that these nanostructures consist of ∼16 wt % ionic liquid, which is considered to provide the stability to the plasmid DNA that eventually enhanced the transformation efficiency.

  10. Supramolecular helical nanofibers assembled from a pyridinium-functionalized methyl glycyrrhetate amphiphile

    Science.gov (United States)

    Gao, Yuxia; Hao, Jie; Wu, Jindan; Zhang, Xun; Hu, Jun; Ju, Yong

    2015-08-01

    A glycyrrhetate-containing amphiphile, MGP (1-[2-(methyl glycyrrhetate)-2-oxoethyl]pyridinium bromide), has been synthesized, and found to assemble into supramolecular helical nanofibers in chloroform/aromatic solvents, which are primarily driven by π-π stacking, van der Waals forces, and hydrophobic interactions. During the assembly process, MGP stacked into J-aggregates resulting in the sequestration of the hydrophilic pyridinium cation within the interior with the concomitant projection of its hydrophobic skeleton on the outside surface. Ultimately, this protrusion generated a staggered angle due to the steric hindrance between stacked molecules. This staggered angle further led to molecular misalignments and the formation of helical fibrils, which could twist with each other to fabricate larger helical fibers. Consequently, a gel was formed by intertwining these nanofibers into three-dimensional networks. Using this strategy, we found that other triterpenoid-tailored pyridinium amphiphiles are also potential scaffolds for supramolecular helical structures. This work provides a facile approach for the fabrication of supramolecular macroscopic chiral nanostructures that originate from natural products.A glycyrrhetate-containing amphiphile, MGP (1-[2-(methyl glycyrrhetate)-2-oxoethyl]pyridinium bromide), has been synthesized, and found to assemble into supramolecular helical nanofibers in chloroform/aromatic solvents, which are primarily driven by π-π stacking, van der Waals forces, and hydrophobic interactions. During the assembly process, MGP stacked into J-aggregates resulting in the sequestration of the hydrophilic pyridinium cation within the interior with the concomitant projection of its hydrophobic skeleton on the outside surface. Ultimately, this protrusion generated a staggered angle due to the steric hindrance between stacked molecules. This staggered angle further led to molecular misalignments and the formation of helical fibrils, which could

  11. Adhesion on Nanoorganized Multilayers

    Directory of Open Access Journals (Sweden)

    Yolla Kazzi

    2011-01-01

    Full Text Available Nanostructured multilayers composed of alternate organic (alkyldithiol and metallic (gold layers are grafted onto glass plates and prepared in order to modify the mechanical and local dissipative properties of a thin surface layer of the substrate. The adhesion phenomenon between a polyisoprene elastomer and these layers is presented and verified by two theories, namely, Johnson, Kendall, Roberts (JKR and linear elastic fracture mechanics. The increase in adhesion with contact time following a power law has been clearly noted.

  12. Structure and Self-Assembly of Oligocarbonate-Fluorene End Functionalized Poly (ethylene glycol) ABA Triblock Polymer

    Science.gov (United States)

    Wei, Guangmin; Prabhu, Vivek; Venkataraman, Shrinivas; Yang, Yi Yan; Hedrick, James; Vivek Prabhu Team; Shrinivas Venkataraman, Yi Yan Yang Collaboration; James Hedrick Collaboration

    Hierarchical structures of oligocarbonate-fluorene end-functionalized poly(ethylene glycol) triblock copolymer (P(F-TMC)m-PEG444-P(F-TMC)m) were characterized by light scattering, atomic force microscopy, and Ultraviolet-visible spectroscopy in dilute regime in water, a poor solvent of F-TMC block. The evidence for pai-pai stacked of F-TMC block in self-assembled structure was provided. The self-assembly behavior is highly dependent on concentration and F-TMC block length, m. The presence of clusters dominates the population of scatterers once m is larger than 2, where there is no clear evidence of a separation of micelles and clusters. The molecular aggregation driven by F-TMC groups appears too strong to permit labile micelle-cluster dynamics as observed with m = 2 and 1.2. The non-mean field scaling of the aggregation number, when compared to models for triblock copolymers, highlights the need for a molecular-based model to predict the self-assembly at low end-group numbers. In our case, the end-groups are oligomers, so the comparison to Flory scaling may not be justified.

  13. Axonal Membranes and Their Domains: Assembly and Function of the Axon Initial Segment and Node of Ranvier

    Directory of Open Access Journals (Sweden)

    Andrew D. Nelson

    2017-05-01

    Full Text Available Neurons are highly specialized cells of the nervous system that receive, process and transmit electrical signals critical for normal brain function. Here, we review the intricate organization of axonal membrane domains that facilitate rapid action potential conduction underlying communication between complex neuronal circuits. Two critical excitable domains of vertebrate axons are the axon initial segment (AIS and the nodes of Ranvier, which are characterized by the high concentrations of voltage-gated ion channels, cell adhesion molecules and specialized cytoskeletal networks. The AIS is located at the proximal region of the axon and serves as the site of action potential initiation, while nodes of Ranvier, gaps between adjacent myelin sheaths, allow rapid propagation of the action potential through saltatory conduction. The AIS and nodes of Ranvier are assembled by ankyrins, spectrins and their associated binding partners through the clustering of membrane proteins and connection to the underlying cytoskeleton network. Although the AIS and nodes of Ranvier share similar protein composition, their mechanisms of assembly are strikingly different. Here we will cover the mechanisms of formation and maintenance of these axonal excitable membrane domains, specifically highlighting the similarities and differences between them. We will also discuss recent advances in super resolution fluorescence imaging which have elucidated the arrangement of the submembranous axonal cytoskeleton revealing a surprising structural organization necessary to maintain axonal organization and function. Finally, human mutations in axonal domain components have been associated with a growing number of neurological disorders including severe cognitive dysfunction, epilepsy, autism, neurodegenerative diseases and psychiatric disorders. Overall, this review highlights the assembly, maintenance and function of axonal excitable domains, particularly the AIS and nodes of

  14. RNA-Seq analysis of Cocos nucifera: transcriptome sequencing and de novo assembly for subsequent functional genomics approaches.

    Directory of Open Access Journals (Sweden)

    Haikuo Fan

    Full Text Available BACKGROUND: Cocos nucifera (coconut, a member of the Arecaceae family, is an economically important woody palm grown in tropical regions. Despite its agronomic importance, previous germplasm assessment studies have relied solely on morphological and agronomical traits. Molecular biology techniques have been scarcely used in assessment of genetic resources and for improvement of important agronomic and quality traits in Cocos nucifera, mostly due to the absence of available sequence information. METHODOLOGY/PRINCIPAL FINDINGS: To provide basic information for molecular breeding and further molecular biological analysis in Cocos nucifera, we applied RNA-seq technology and de novo assembly to gain a global overview of the Cocos nucifera transcriptome from mixed tissue samples. Using Illumina sequencing, we obtained 54.9 million short reads and conducted de novo assembly to obtain 57,304 unigenes with an average length of 752 base pairs. Sequence comparison between assembled unigenes and released cDNA sequences of Cocos nucifera and Elaeis guineensis indicated that the assembled sequences were of high quality. Approximately 99.9% of unigenes were novel compared to the released coconut EST sequences. Using BLASTX, 68.2% of unigenes were successfully annotated based on the Genbank non-redundant (Nr protein database. The annotated unigenes were then further classified using the Gene Ontology (GO, Clusters of Orthologous Groups (COG and Kyoto Encyclopedia of Genes and Genomes (KEGG databases. CONCLUSIONS/SIGNIFICANCE: Our study provides a large quantity of novel genetic information for Cocos nucifera. This information will act as a valuable resource for further molecular genetic studies and breeding in coconut, as well as for isolation and characterization of functional genes involved in different biochemical pathways in this important tropical crop species.

  15. RNA-Seq Analysis of Cocos nucifera: Transcriptome Sequencing and De Novo Assembly for Subsequent Functional Genomics Approaches

    Science.gov (United States)

    Xia, Wei; Mason, Annaliese S.; Xia, Zhihui; Qiao, Fei; Zhao, Songlin; Tang, Haoru

    2013-01-01

    Background Cocos nucifera (coconut), a member of the Arecaceae family, is an economically important woody palm grown in tropical regions. Despite its agronomic importance, previous germplasm assessment studies have relied solely on morphological and agronomical traits. Molecular biology techniques have been scarcely used in assessment of genetic resources and for improvement of important agronomic and quality traits in Cocos nucifera, mostly due to the absence of available sequence information. Methodology/Principal Findings To provide basic information for molecular breeding and further molecular biological analysis in Cocos nucifera, we applied RNA-seq technology and de novo assembly to gain a global overview of the Cocos nucifera transcriptome from mixed tissue samples. Using Illumina sequencing, we obtained 54.9 million short reads and conducted de novo assembly to obtain 57,304 unigenes with an average length of 752 base pairs. Sequence comparison between assembled unigenes and released cDNA sequences of Cocos nucifera and Elaeis guineensis indicated that the assembled sequences were of high quality. Approximately 99.9% of unigenes were novel compared to the released coconut EST sequences. Using BLASTX, 68.2% of unigenes were successfully annotated based on the Genbank non-redundant (Nr) protein database. The annotated unigenes were then further classified using the Gene Ontology (GO), Clusters of Orthologous Groups (COG) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. Conclusions/Significance Our study provides a large quantity of novel genetic information for Cocos nucifera. This information will act as a valuable resource for further molecular genetic studies and breeding in coconut, as well as for isolation and characterization of functional genes involved in different biochemical pathways in this important tropical crop species. PMID:23555859

  16. Discovery of genes related to insecticide resistance in Bactrocera dorsalis by functional genomic analysis of a de novo assembled transcriptome.

    Directory of Open Access Journals (Sweden)

    Ju-Chun Hsu

    Full Text Available Insecticide resistance has recently become a critical concern for control of many insect pest species. Genome sequencing and global quantization of gene expression through analysis of the transcriptome can provide useful information relevant to this challenging problem. The oriental fruit fly, Bactrocera dorsalis, is one of the world's most destructive agricultural pests, and recently it has been used as a target for studies of genetic mechanisms related to insecticide resistance. However, prior to this study, the molecular data available for this species was largely limited to genes identified through homology. To provide a broader pool of gene sequences of potential interest with regard to insecticide resistance, this study uses whole transcriptome analysis developed through de novo assembly of short reads generated by next-generation sequencing (NGS. The transcriptome of B. dorsalis was initially constructed using Illumina's Solexa sequencing technology. Qualified reads were assembled into contigs and potential splicing variants (isotigs. A total of 29,067 isotigs have putative homologues in the non-redundant (nr protein database from NCBI, and 11,073 of these correspond to distinct D. melanogaster proteins in the RefSeq database. Approximately 5,546 isotigs contain coding sequences that are at least 80% complete and appear to represent B. dorsalis genes. We observed a strong correlation between the completeness of the assembled sequences and the expression intensity of the transcripts. The assembled sequences were also used to identify large numbers of genes potentially belonging to families related to insecticide resistance. A total of 90 P450-, 42 GST-and 37 COE-related genes, representing three major enzyme families involved in insecticide metabolism and resistance, were identified. In addition, 36 isotigs were discovered to contain target site sequences related to four classes of resistance genes. Identified sequence motifs were also

  17. Sequencing, de novo assembly, functional annotation and analysis of Phyllanthus amarus leaf transcriptome using the Illumina platform

    Directory of Open Access Journals (Sweden)

    Aparupa eBose Mazumdar

    2016-01-01

    Full Text Available Phyllanthus amarus Schum. & Thonn., a widely distributed annual medicinal herb has a long history of use in the traditional system of medicine for over 2000 years. However, the lack of genomic data for P. amarus, a non-model organism hinders research at the molecular level. In the present study, high-throughput sequencing technology has been employed to enhance better understanding of this herb and provide comprehensive genomic information for future work. Here P. amarus leaf transcriptome was sequenced using the Illumina Miseq platform. We assembled 85,927 non-redundant unitranscript sequences with an average length of 1548 bp, from 18,060,997 raw reads. Sequence similarity analyses and annotation of these unitranscripts were performed against databases like green plants non-redundant (nr protein database, Gene Ontology (GO, Clusters of Orthologous Groups (COG, PlnTFDB, KEGG databases. As a result, 69,394 GO terms, 583 enzyme codes, 134 KEGG maps and 59 Transcription Factor families were generated. Functional and comparative analyses of assembled unitranscripts were also performed with the most closely related species like Populus trichocarpa and Ricinus communis using TRAPID. KEGG analysis showed that a number of assembled unitranscripts were involved in secondary metabolites, mainly phenylpropanoid, flavonoid, terpenoids, alkaloids and lignan biosynthetic pathways that have significant medicinal attributes. Further, Fragments Per Kilobase of transcript per Million mapped reads (FPKM values of the identified secondary metabolite pathway genes were determined and Reverse Transcription PCR (RT-PCR of few of these genes were performed to validate the de novo assembled leaf transcriptome dataset. In addition 65,273 simple sequence repeats (SSRs were also identified. To the best of our knowledge this is the first transcriptomic dataset of P. amarus till date. Our study provides the largest genetic resource that will lead to drug development and

  18. Optimization of de novo transcriptome assembly from high-throughput short read sequencing data improves functional annotation for non-model organisms

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    Haznedaroglu Berat Z

    2012-07-01

    Full Text Available Abstract Background The k-mer hash length is a key factor affecting the output of de novo transcriptome assembly packages using de Bruijn graph algorithms. Assemblies constructed with varying single k-mer choices might result in the loss of unique contiguous sequences (contigs and relevant biological information. A common solution to this problem is the clustering of single k-mer assemblies. Even though annotation is one of the primary goals of a transcriptome assembly, the success of assembly strategies does not consider the impact of k-mer selection on the annotation output. This study provides an in-depth k-mer selection analysis that is focused on the degree of functional annotation achieved for a non-model organism where no reference genome information is available. Individual k-mers and clustered assemblies (CA were considered using three representative software packages. Pair-wise comparison analyses (between individual k-mers and CAs were produced to reveal missing Kyoto Encyclopedia of Genes and Genomes (KEGG ortholog identifiers (KOIs, and to determine a strategy that maximizes the recovery of biological information in a de novo transcriptome assembly. Results Analyses of single k-mer assemblies resulted in the generation of various quantities of contigs and functional annotations within the selection window of k-mers (k-19 to k-63. For each k-mer in this window, generated assemblies contained certain unique contigs and KOIs that were not present in the other k-mer assemblies. Producing a non-redundant CA of k-mers 19 to 63 resulted in a more complete functional annotation than any single k-mer assembly. However, a fraction of unique annotations remained (~0.19 to 0.27% of total KOIs in the assemblies of individual k-mers (k-19 to k-63 that were not present in the non-redundant CA. A workflow to recover these unique annotations is presented. Conclusions This study demonstrated that different k-mer choices result in various quantities

  19. Trinity: Transcriptome Assembly for Genetic and Functional Analysis of Cancer | Informatics Technology for Cancer Research (ITCR)

    Science.gov (United States)

    The cancer transcriptome is shaped by genetic changes, variation in gene transcription, mRNA processing, editing and stability, and the cancer microbiome. Deciphering this variation and understanding its implications on tumorigenesis requires sophisticated computational analyses. Most RNA-Seq analyses rely on methods that first map short reads to a reference genome, and then compare them to annotated transcripts or assemble them. However, this strategy can be limited when the cancer genome is substantially different than the reference or for detecting sequences from the cancer microbiome.

  20. Sulfamide chemistry applied to the functionalization of self-assembled monolayers on gold surfaces

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    Loïc Pantaine

    2017-04-01

    Full Text Available Aniline-terminated self-assembled monolayers (SAMs on gold surfaces have successfully reacted with ArSO2NHOSO2Ar (Ar = 4-MeC6H4 or 4-FC6H4 resulting in monolayers with sulfamide moieties and different end groups. Moreover, the sulfamide groups on the SAMs can be hydrolyzed showing the partial regeneration of the aniline surface. SAMs were characterized by water contact angle (WCA measurements, Fourier-transform infrared reflection absorption spectroscopy (IRRAS and X-ray photoelectron spectroscopy (XPS.

  1. Hydrogen-bonded rosettes comprising π-conjugated systems as building blocks for functional one-dimensional assemblies.

    Science.gov (United States)

    Adhikari, Bimalendu; Lin, Xu; Yamauchi, Mitsuaki; Ouchi, Hayato; Aratsu, Keisuke; Yagai, Shiki

    2017-08-29

    Hydrogen-bonded supermacrocycles (rosettes) are attractive disk-shaped noncovalent synthons for extended functional columnar nanoassemblies. They can serve not only as noncovalent monomer units for supramolecular polymers and discrete oligomers in a dilute solution but also as constituent entities for soft matters such as gels and lyotropic/thermotropic liquid crystals. However, what are the merits of using supramolecular rosettes instead of using expanded π-conjugated covalent molecules? This review covers the self-assembly of photochemically and electrochemically active π-conjugated molecules through the formation of supramolecular rosettes via directional complementary multiple hydrogen-bonding interactions. These rosettes comprising π-conjugated covalent functional units stack into columnar nanoassemblies with unique structures and properties. By overviewing the design principle, characterization, and properties and functionalities of various examples, we illustrate the merits of utilizing rosette motifs. Basically, one can easily access a well-defined expanded π-surface composed of multi-chromophoric systems, which can ultimately afford stable extended nanoassemblies even in a dilute solution due to the higher association constants of supermacrocyclized π-systems. Importantly, these columnar nanoassemblies exhibit unique features in self-assembly processes, chiroptical, photophysical and electrochemical properties, nanoscale morphologies, and bulk properties. Moreover, the stimuli responsiveness of individual building blocks can be amplified to a greater extent by exploiting rosette intermediates to organize them into one-dimensional columnar structures. In the latter parts of the review, we also highlight the application of rosettes in supramolecular polymer systems, photovoltaic devices, and others.

  2. Structural and functional features of self-assembling protein nanoparticles produced in endotoxin-free Escherichia coli.

    Science.gov (United States)

    Rueda, Fabián; Céspedes, María Virtudes; Sánchez-Chardi, Alejandro; Seras-Franzoso, Joaquin; Pesarrodona, Mireia; Ferrer-Miralles, Neus; Vázquez, Esther; Rinas, Ursula; Unzueta, Ugutz; Mamat, Uwe; Mangues, Ramón; García-Fruitós, Elena; Villaverde, Antonio

    2016-04-08

    Production of recombinant drugs in process-friendly endotoxin-free bacterial factories targets to a lessened complexity of the purification process combined with minimized biological hazards during product application. The development of nanostructured recombinant materials in innovative nanomedical activities expands such a need beyond plain functional polypeptides to complex protein assemblies. While Escherichia coli has been recently modified for the production of endotoxin-free proteins, no data has been so far recorded regarding how the system performs in the fabrication of smart nanostructured materials. We have here explored the nanoarchitecture and in vitro and in vivo functionalities of CXCR4-targeted, self-assembling protein nanoparticles intended for intracellular delivery of drugs and imaging agents in colorectal cancer. Interestingly, endotoxin-free materials exhibit a distinguishable architecture and altered size and target cell penetrability than counterparts produced in conventional E. coli strains. These variant nanoparticles show an eventual proper biodistribution and highly specific and exclusive accumulation in tumor upon administration in colorectal cancer mice models, indicating a convenient display and function of the tumor homing peptides and high particle stability under physiological conditions. The observations made here support the emerging endotoxin-free E. coli system as a robust protein material producer but are also indicative of a particular conformational status and organization of either building blocks or oligomers. This appears to be promoted by multifactorial stress-inducing conditions upon engineering of the E. coli cell envelope, which impacts on the protein quality control of the cell factory.

  3. Synthesis and photocatalytic property of multilayered Co3O4

    Science.gov (United States)

    Zhang, Dong En; Ren, Li Zheng; Hao, Xiao Yun; Pan, Bin Bin; Wang, Ming Yan; Ma, Juan Juan; Li, Feng; Li, Shu An; Tong, Zhi Wei

    2015-11-01

    Co3O4 multilayered structures were successfully synthesized by a facile poly (ethylene glycol 20000) (PEG-20000) assisted hydrothermal technique in combination with calcination method. The final Co3O4 multilayered structures inherited perfectly the morphology of the preliminarily hydrothermal products. Experimental results obtained from the different growth stages demonstrate that the as-prepared precursor exhibit an interesting time-dependent evolution of building blocks, from urchin to multilayer. The possible formation mechanism for the hierarchical structures with various architectures is presented on account of the self-assembled growth induced by Ostwald ripening. Because of the unique structured composed of slices, the photocatalytic activity of the products was examined by measuring the photodecolourisation of methyl violet solution with ultraviolet radiation. The result shows that our products have a good photocatalytic activity.

  4. How to build functional thylakoid membranes: from plastid transcription to protein complex assembly.

    Science.gov (United States)

    Lyska, Dagmar; Meierhoff, Karin; Westhoff, Peter

    2013-02-01

    Chloroplasts are the endosymbiotic descendants of cyanobacterium-like prokaryotes. Present genomes of plant and green algae chloroplasts (plastomes) contain ~100 genes mainly encoding for their transcription-/translation-machinery, subunits of the thylakoid membrane complexes (photosystems II and I, cytochrome b (6) f, ATP synthase), and the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase. Nevertheless, proteomic studies have identified several thousand proteins in chloroplasts indicating that the majority of the plastid proteome is not encoded by the plastome. Indeed, plastid and host cell genomes have been massively rearranged in the course of their co-evolution, mainly through gene loss, horizontal gene transfer from the cyanobacterium/chloroplast to the nucleus of the host cell, and the emergence of new nuclear genes. Besides structural components of thylakoid membrane complexes and other (enzymatic) complexes, the nucleus provides essential factors that are involved in a variety of processes inside the chloroplast, like gene expression (transcription, RNA-maturation and translation), complex assembly, and protein import. Here, we provide an overview on regulatory factors that have been described and characterized in the past years, putting emphasis on mechanisms regulating the expression and assembly of the photosynthetic thylakoid membrane complexes.

  5. Assembly and function of AsGlu2 fibrillar multimer of oat beta-glucosidase.

    Science.gov (United States)

    Kwak, Su-Nam; Kim, Sang-Yeob; Choi, Sa-Ra; Kim, In-Soo

    2009-03-01

    Oat beta-glucosidase in plastid exists as a long fibrillar structure of AsGlu1 homomultimer (type I) and heteromultimer of AsGlu1 and AsGlu2 (type II). In spite of the high amino acid sequence homology of AsGlu1 and AsGlu2, AsGlu1 assembles into the fibrillar multimers but AsGlu2 forms a dimer when expressed in E. coli. A swapping analysis of AsGlu2 cDNA with AsGlu1 cDNA indicated that the C-terminal segment of AsGlu1 was critical for the fibrillar multimerization. A single substitution of glutamic acid-495 of AsGlu2 in the C-terminal region with lysine, an AsGlu1 counterpart amino acid for the glutamic acid-495, assembled the AsGlu2 into fibrillar homomultimers. The mutant AsGlu2 homomultimer was highly stable and had relatively faster electric mobility in native gel than the AsGlu1 homomultimer. Multimerization increased enzyme affinity to substrates.

  6. Urea-Functionalized M4L6 Cage Receptors: Self-Assembly, Dynamics, and Anion Recognition in Aqueous Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Custelcean, Radu [ORNL; Bonnesen, Peter V [ORNL; Duncan, Nathan C [ORNL; Van Berkel, Gary J [ORNL; Hay, Benjamin [ORNL

    2012-01-01

    We present an extensive study of a novel class of de novo designed tetrahedral M{sub 4}L{sub 6} (M = Ni, Zn) cage receptors, wherein internal decoration of the cage cavities with urea anion-binding groups, via functionalization of the organic components L, led to selective encapsulation of tetrahedral oxoanions EO{sub 4}{sup -} (E = S, Se, Cr, Mo, W, n = 2; E = P, n = 3) from aqueous solutions, based on shape, size, and charge recognition. External functionalization with tBu groups led to enhanced solubility of the cages in aqueous methanol solutions, thereby allowing for their thorough characterization by multinuclear ({sup 1}H, {sup 13}C, {sup 77}Se) and diffusion NMR spectroscopies. Additional experimental characterization by electrospray ionization mass spectrometry, UV-vis spectroscopy, and single-crystal X-ray diffraction, as well as theoretical calculations, led to a detailed understanding of the cage structures, self-assembly, and anion encapsulation. We found that the cage self-assembly is templated by EO{sub 4}{sup -} oxoanions (n {ge} 2), and upon removal of the templating anion the tetrahedral M{sub 4}L{sub 6} cages rearrange into different coordination assemblies. The exchange selectivity among EO{sub 4}{sup -} oxoanions has been investigated with {sup 77}Se NMR spectroscopy using {sup 77}SeO{sub 4}{sup 2-} as an anionic probe, which found the following selectivity trend: PO{sub 4}{sup 3-} CrO{sub 4}{sup 2-} > SO{sub 4}{sup 2-} > SeO{sub 4}{sup 2-} > MoO{sub 4}{sup 2-} > WO{sub 4}{sup 2-}. In addition to the complementarity and flexibility of the cage receptor, a combination of factors have been found to contribute to the observed anion selectivity, including the anions charge, size, hydration, basicity, and hydrogen-bond acceptor abilities.

  7. Highly branched platinum nanolance assemblies by polyallylamine functionalization as superior active, stable, and alcohol-tolerant oxygen reduction electrocatalysts

    Science.gov (United States)

    Fu, Gengtao; Jiang, Xian; Gong, Mingxing; Chen, Yu; Tang, Yawen; Lin, Jun; Lu, Tianhong

    2014-06-01

    The chemical functionalization of platinum (Pt) nanostructures is becoming a new trend in electrocatalysts designs. Meanwhile, highly branched Pt nanostructures are highly exciting electrocatalysts with high activity and stability owing to their specific physical and chemical properties. In this work, the polyallylamine (PAH) functionalized Pt nanolance assemblies (Pt NLAs) have been successfully synthesized by chemical reduction of PAH-PtII complex using formaldehyde (HCHO) in a two-phase water-complex system. The as-prepared Pt NLAs are highly branched and three-dimensionally (3D) interconnected nanostructures, which are composed of many long Pt nanolances in various directions. PAH functionalization improves the electrocatalytic activity of the Pt NLAs for an oxygen reduction reaction (ORR) because of high interface proton concentration on the Pt surface and excellent anti-oxidation ability of the Pt nanolances. Meanwhile, the PAH molecules bound on the Pt NLAs surface act as barrier networks to restrain accessibility of alcohol, exhibiting a high ORR selectivity. In addition, the PAH functionalized Pt NLAs show excellent durability for the ORR due to their particular 3D interconnected structure. The work demonstrates that the PAH functionalized Pt NLAs are indeed promising cathodic electrocatalysts for practical application in direct alcohol fuel cells.The chemical functionalization of platinum (Pt) nanostructures is becoming a new trend in electrocatalysts designs. Meanwhile, highly branched Pt nanostructures are highly exciting electrocatalysts with high activity and stability owing to their specific physical and chemical properties. In this work, the polyallylamine (PAH) functionalized Pt nanolance assemblies (Pt NLAs) have been successfully synthesized by chemical reduction of PAH-PtII complex using formaldehyde (HCHO) in a two-phase water-complex system. The as-prepared Pt NLAs are highly branched and three-dimensionally (3D) interconnected nanostructures

  8. Transcriptomic Analysis of the Endangered Neritid Species Clithon retropictus: De Novo Assembly, Functional Annotation, and Marker Discovery

    Directory of Open Access Journals (Sweden)

    So Young Park

    2016-07-01

    Full Text Available An aquatic gastropod belonging to the family Neritidae, Clithon retropictus is listed as an endangered class II species in South Korea. The lack of information on its genomic background limits the ability to obtain functional data resources and inhibits informed conservation planning for this species. In the present study, the transcriptomic sequencing and de novo assembly of C. retropictus generated a total of 241,696,750 high-quality reads. These assembled to 282,838 unigenes with mean and N50 lengths of 736.9 and 1201 base pairs, respectively. Of these, 125,616 unigenes were subjected to annotation analysis with known proteins in Protostome DB, COG, GO, and KEGG protein databases (BLASTX; E ≤ 0.00001 and with known nucleotides in the Unigene database (BLASTN; E ≤ 0.00001. The GO analysis indicated that cellular process, cell, and catalytic activity are the predominant GO terms in the biological process, cellular component, and molecular function categories, respectively. In addition, 2093 unigenes were distributed in 107 different KEGG pathways. Furthermore, 49,280 simple sequence repeats were identified in the unigenes (>1 kilobase sequences. This is the first report on the identification of transcriptomic and microsatellite resources for C. retropictus, which opens up the possibility of exploring traits related to the adaptation and acclimatization of this species.

  9. Transcriptomic Analysis of the Endangered Neritid Species Clithon retropictus: De Novo Assembly, Functional Annotation, and Marker Discovery.

    Science.gov (United States)

    Park, So Young; Patnaik, Bharat Bhusan; Kang, Se Won; Hwang, Hee-Ju; Chung, Jong Min; Song, Dae Kwon; Sang, Min Kyu; Patnaik, Hongray Howrelia; Lee, Jae Bong; Noh, Mi Young; Kim, Changmu; Kim, Soonok; Park, Hong Seog; Lee, Jun Sang; Han, Yeon Soo; Lee, Yong Seok

    2016-07-22

    An aquatic gastropod belonging to the family Neritidae, Clithon retropictus is listed as an endangered class II species in South Korea. The lack of information on its genomic background limits the ability to obtain functional data resources and inhibits informed conservation planning for this species. In the present study, the transcriptomic sequencing and de novo assembly of C. retropictus generated a total of 241,696,750 high-quality reads. These assembled to 282,838 unigenes with mean and N50 lengths of 736.9 and 1201 base pairs, respectively. Of these, 125,616 unigenes were subjected to annotation analysis with known proteins in Protostome DB, COG, GO, and KEGG protein databases (BLASTX; E ≤ 0.00001) and with known nucleotides in the Unigene database (BLASTN; E ≤ 0.00001). The GO analysis indicated that cellular process, cell, and catalytic activity are the predominant GO terms in the biological process, cellular component, and molecular function categories, respectively. In addition, 2093 unigenes were distributed in 107 different KEGG pathways. Furthermore, 49,280 simple sequence repeats were identified in the unigenes (>1 kilobase sequences). This is the first report on the identification of transcriptomic and microsatellite resources for C. retropictus, which opens up the possibility of exploring traits related to the adaptation and acclimatization of this species.

  10. Density Functional Theory with Modified Dispersion Correction for Metals Applied to Self-Assembled Monolayers of Thiols on Au(111

    Directory of Open Access Journals (Sweden)

    M. P. Andersson

    2013-01-01

    Full Text Available Using sound physical principles we modify the DFT-D2 atom pairwise semiempirical dispersion correction to density functional theory to work for metallic systems and in particular self-assembled monolayers of thiols on gold surfaces. We test our approximation for two functionals PBE-D and revPBE-D for lattice parameters and cohesive energies for Ni, Pd, Pt, Cu, Ag, and Au, adsorption energies of CO on (111 surfaces of Pd, Pt, Cu, Ag, and Au, and adsorption energy of benzene on Ag(111 and Au(111. Agreement with experimental data is substantially improved. We apply the method to self-assembled monolayers of alkanethiols on Au(111 and find reasonable agreement for PBE-D and revPBE-D for both physisorption of n-alkanethiols as well as dissociative chemisorption of dimethyl disulfide as an Au-adatom-dithiolate complex. By modifying the C6 coefficient for Au, we obtain quantitative agreement for physisorption and chemisorption for both PBE-D and revPBE-D using the same set of parameters. Our results confirm that inclusion of dispersion forces is crucial for any quantitative analysis of the thiol and thiolate bonds to the gold surface using quantum chemical calculations.

  11. Assembly and function of the major histocompatibility complex (MHC) I peptide-loading complex are conserved across higher vertebrates.

    Science.gov (United States)

    Hinz, Andreas; Jedamzick, Johanna; Herbring, Valentina; Fischbach, Hanna; Hartmann, Jessica; Parcej, David; Koch, Joachim; Tampé, Robert

    2014-11-28

    Antigen presentation to cytotoxic T lymphocytes via major histocompatibility complex class I (MHC I) molecules depends on the heterodimeric transporter associated with antigen processing (TAP). For efficient antigen supply to MHC I molecules in the ER, TAP assembles a macromolecular peptide-loading complex (PLC) by recruiting tapasin. In evolution, TAP appeared together with effector cells of adaptive immunity at the transition from jawless to jawed vertebrates and diversified further within the jawed vertebrates. Here, we compared TAP function and interaction with tapasin of a range of species within two classes of jawed vertebrates. We found that avian and mammalian TAP1 and TAP2 form heterodimeric complexes across taxa. Moreover, the extra N-terminal domain TMD0 of mammalian TAP1 and TAP2 as well as avian TAP2 recruits tapasin. Strikingly, however, only TAP1 and TAP2 from the same taxon can form a functional heterodimeric translocation complex. These data demonstrate that the dimerization interface between TAP1 and TAP2 and the tapasin docking sites for PLC assembly are conserved in evolution, whereas elements of antigen translocation diverged later in evolution and are thus taxon specific. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

  12. A Synthetic Circuit for Mercury Bioremediation Using Self-Assembling Functional Amyloids.

    Science.gov (United States)

    Tay, Pei Kun R; Nguyen, Peter Q; Joshi, Neel S

    2017-10-20

    Synthetic biology approaches to bioremediation are a key sustainable strategy to leverage the self-replicating and programmable aspects of biology for environmental stewardship. The increasing spread of anthropogenic mercury pollution into our habitats and food chains is a pressing concern. Here, we explore the use of programmed bacterial biofilms to aid in the sequestration of mercury. We demonstrate that by integrating a mercury-responsive promoter and an operon encoding a mercury-absorbing self-assembling extracellular protein nanofiber, we can engineer bacteria that can detect and sequester toxic Hg 2+ ions from the environment. This work paves the way for the development of on-demand biofilm living materials that can operate autonomously as heavy-metal absorbents.

  13. De Novo Assembly, Characterization and Functional Annotation of Southern Hake (Merluccius australis Transcriptome

    Directory of Open Access Journals (Sweden)

    Daniela Reyes

    2016-11-01

    Full Text Available Southern hake (Merluccius australis is an ecological and economically important demersal fish in Chile and Argentina. Notwithstanding, genetic resource for genetic or ecological studies on this species are scarce. Consequently, here we present transcriptome sequencing results (RNA-Seq for spleen and liver tissues with the 454 FLX titanium platform. The de novo transcriptome assembly generated 10,314 unigenes, with an average length of 510 bp, N50 of 572 bp and 3,171 annotated sequences. A specific Gadiform BLAST search, with focus on immune genes, showed 186 (56% genes homologous to those of Atlantic cod. A total of 2,302 microsatellites were detected in 1,687 unigenes and 741 presented adequate flanking sequences for primer design. In total, these potential molecular markers and transcriptome characterization represent an important resource for genetic and ecological studies on southern hake.

  14. Characterization of Liaoning cashmere goat transcriptome: sequencing, de novo assembly, functional annotation and comparative analysis.

    Directory of Open Access Journals (Sweden)

    Hongliang Liu

    Full Text Available BACKGROUND: Liaoning cashmere goat is a famous goat breed for cashmere wool. In order to increase the transcriptome data and accelerate genetic improvement for this breed, we performed de novo transcriptome sequencing to generate the first expressed sequence tag dataset for the Liaoning cashmere goat, using next-generation sequencing technology. RESULTS: Transcriptome sequencing of Liaoning cashmere goat on a Roche 454 platform yielded 804,601 high-quality reads. Clustering and assembly of these reads produced a non-redundant set of 117,854 unigenes, comprising 13,194 isotigs and 104,660 singletons. Based on similarity searches with known proteins, 17,356 unigenes were assigned to 6,700 GO categories, and the terms were summarized into three main GO categories and 59 sub-categories. 3,548 and 46,778 unigenes had significant similarity to existing sequences in the KEGG and COG databases, respectively. Comparative analysis revealed that 42,254 unigenes were aligned to 17,532 different sequences in NCBI non-redundant nucleotide databases. 97,236 (82.51% unigenes were mapped to the 30 goat chromosomes. 35,551 (30.17% unigenes were matched to 11,438 reported goat protein-coding genes. The remaining non-matched unigenes were further compared with cattle and human reference genes, 67 putative new goat genes were discovered. Additionally, 2,781 potential simple sequence repeats were initially identified from all unigenes. CONCLUSION: The transcriptome of Liaoning cashmere goat was deep sequenced, de novo assembled, and annotated, providing abundant data to better understand the Liaoning cashmere goat transcriptome. The potential simple sequence repeats provide a material basis for future genetic linkage and quantitative trait loci analyses.

  15. Two-dimensional self-assembly of DNA-functionalized gold nanoparticles

    Science.gov (United States)

    Wang, Wenjie; Zhang, Honghu; Hagen, Noah; Kuzmenko, Ivan; Akinc, Mufit; Travesset, Alex; Mallapragada, Surya; Vaknin, David

    2D superlattices of nanoparticles (NPs) are promising candidates for nano-devices. It is still challenging to develop a simple yet efficient protocol to assemble NPs in a controlled manner. Here, we report on formation of 2D Gibbs monolayers of single-stranded DNA-coated gold nanoparticles (ssDNA-AuNPs) at the air-water interface by manipulation of salts contents. MgCl2 and CaCl2 in solutions facilitate the accumulation of the non-complementary ssDNA-AuNPs on aqueous surfaces. Grazing-incidence small-angle X-ray scattering (GISAXS) and X-ray reflectivity show that the surface AuNPs assembly forms a mono-particle layer and undergoes a transformation from short-range to long-range (hexagonal) order above a threshold of [MgCl2] or [CaCl2]. For solutions that include two kinds of ssDNA-AuNPs with complementary base-pairing, the surface AuNPs form a thicker film and only in-plane short-range order is observed. By using other salts (NaCl or LaCl3) at concentrations of similar ionic strength to those of MgCl2 or CaCl2, we find that surface adsorbed NPs lack any orders. X-ray fluorescence measurements provide direct evidence of surface enrichment of AuNPs and divalent ions (Ca2 +) . The work was supported by the Office of Basic Energy Sciences, USDOE under Contract No. DE-AC02-07CH11358 and DE-AC02-06CH11357.

  16. Quaternionic Multilayer Perceptron with Local Analyticity

    Directory of Open Access Journals (Sweden)

    Nobuyuki Matsui

    2012-11-01

    Full Text Available A multi-layered perceptron type neural network is presented and analyzed in this paper. All neuronal parameters such as input, output, action potential and connection weight are encoded by quaternions, which are a class of hypercomplex number system. Local analytic condition is imposed on the activation function in updating neurons’ states in order to construct learning algorithm for this network. An error back-propagation algorithm is introduced for modifying the connection weights of the network.

  17. Microfluidic perfusion culture system for multilayer artery tissue models.

    Science.gov (United States)

    Yamagishi, Yuka; Masuda, Taisuke; Matsusaki, Michiya; Akashi, Mitsuru; Yokoyama, Utako; Arai, Fumihito

    2014-11-01

    We described an assembly technique and perfusion culture system for constructing artery tissue models. This technique differed from previous studies in that it does not require a solid biodegradable scaffold; therefore, using sheet-like tissues, this technique allowed the facile fabrication of tubular tissues can be used as model. The fabricated artery tissue models had a multilayer structure. The assembly technique and perfusion culture system were applicable to many different sizes of fabricated arteries. The shape of the fabricated artery tissue models was maintained by the perfusion culture system; furthermore, the system reproduced the in vivo environment and allowed mechanical stimulation of the arteries. The multilayer structure of the artery tissue model was observed using fluorescent dyes. The equivalent Young's modulus was measured by applying internal pressure to the multilayer tubular tissues. The aim of this study was to determine whether fabricated artery tissue models maintained their mechanical properties with developing. We demonstrated both the rapid fabrication of multilayer tubular tissues that can be used as model arteries and the measurement of their equivalent Young's modulus in a suitable perfusion culture environment.

  18. Design and development of multilayer vascular graft

    Science.gov (United States)

    Madhavan, Krishna

    2011-07-01

    Vascular graft is a widely-used medical device for the treatment of vascular diseases such as atherosclerosis and aneurysm as well as for the use of vascular access and pediatric shunt, which are major causes of mortality and morbidity in this world. Dysfunction of vascular grafts often occurs, particularly for grafts with diameter less than 6mm, and is associated with the design of graft materials. Mechanical strength, compliance, permeability, endothelialization and availability are issues of most concern for vascular graft materials. To address these issues, we have designed a biodegradable, compliant graft made of hybrid multilayer by combining an intimal equivalent, electrospun heparin-impregnated poly-epsilon-caprolactone nanofibers, with a medial equivalent, a crosslinked collagen-chitosan-based gel scaffold. The intimal equivalent is designed to build mechanical strength and stability suitable for in vivo grafting and to prevent thrombosis. The medial equivalent is designed to serve as a scaffold for the activity of the smooth muscle cells important for vascular healing and regeneration. Our results have shown that genipin is a biocompatible crosslinker to enhance the mechanical properties of collagen-chitosan based scaffolds, and the degradation time and the activity of smooth muscle cells in the scaffold can be modulated by the crosslinking degree. For vascular grafting and regeneration in vivo, an important design parameter of the hybrid multilayer is the interface adhesion between the intimal and medial equivalents. With diametrically opposite affinities to water, delamination of the two layers occurs. Physical or chemical modification techniques were thus used to enhance the adhesion. Microscopic examination and graft-relevant functional characterizations have been performed to evaluate these techniques. Results from characterization of microstructure and functional properties, including burst strength, compliance, water permeability and suture

  19. Structure and function of Norrin in assembly and activation of a Frizzled 4–Lrp5/6 complex

    Science.gov (United States)

    Ke, Jiyuan; Harikumar, Kaleeckal G.; Erice, Clara; Chen, Chen; Gu, Xin; Wang, Liren; Parker, Naomi; Cheng, Zhihong; Xu, Wenqing; Williams, Bart O.; Melcher, Karsten; Miller, Laurence J.; Xu, H. Eric

    2013-01-01

    Norrin is a cysteine-rich growth factor that is required for angiogenesis in the eye, ear, brain, and female reproductive organs. It functions as an atypical Wnt ligand by specifically binding to the Frizzled 4 (Fz4) receptor. Here we report the crystal structure of Norrin, which reveals a unique dimeric structure with each monomer adopting a conserved cystine knot fold. Functional studies demonstrate that the novel Norrin dimer interface is required for Fz4 activation. Furthermore, we demonstrate that Norrin contains separate binding sites for Fz4 and for the Wnt ligand coreceptor Lrp5 (low-density lipoprotein-related protein 5) or Lrp6. Instead of inducing Fz4 dimerization, Norrin induces the formation of a ternary complex with Fz4 and Lrp5/6 by binding to their respective extracellular domains. These results provide crucial insights into the assembly and activation of the Norrin–Fz4–Lrp5/6 signaling complex. PMID:24186977

  20. Geodesign the multilayered water safety

    NARCIS (Netherlands)

    Sophronides, Panayiotis; Steenbruggen, John; Scholten, Henk J.; Giaoutzi, Maria

    2016-01-01

    This paper aims to frame the multi-layered water safety concept in the context of a systematic, thorough, multidisciplinary and collaborative methodology for complex problems solving, i.e. geodesign. Multi-layered safety is an integrated flood risk management (FRM) concept based not only on flood

  1. Layer-by-layer assemblies of catechol-functionalized TiO2 nanoparticles and porphyrins through electrostatic interactions.

    Science.gov (United States)

    Burger, Alexandra; Costa, Rubén D; Lobaz, Volodymyr; Peukert, Wolfgang; Guldi, Dirk M; Hirsch, Andreas

    2015-03-23

    In the current work, we present the successful functionalization and stabilization of P-25 TiO2 nanoparticles by means of N1,N7-bis(3-(4-tert-butyl-pyridium-methyl)phenyl)-4-(3-(3-(4-tert-butyl-pyridinium-methyl)phenylamino)-3-oxopropyl)-4-(3,4-dihydroxybenzamido)heptanediamide tribromide (1). The design of the latter is aimed at nanoparticle functionalization and stabilization with organic building blocks. On one hand, 1 features a catechol anchor to enable its covalent grafting onto the TiO2 surface, and on the other hand, positively charged pyridine groups at its periphery to prevent TiO2 agglomeration through electrostatic repulsion. The success of functionalization and stabilization was corroborated by thermogravimetric analysis, dynamic light-scattering, and zeta potential measurements. As a complement to this, the formation of layer-by-layer assemblies, which are governed by electrostatic interactions, by alternate deposition of functionalized TiO2 nanoparticles and two negatively charged porphyrin derivatives, that is, 5,10,15,20-(phenoxyacetic acid)-porphyrin (2) and 5,10,15,20-(4-(2-ethoxycarbonyl)-4-(2-phenoxyacetamido)heptanedioic acid)-porphyrin (3), is documented. To this end, the layer-by-layer deposition is monitored by UV/Vis spectroscopy, scanning electron microscopy, ellipsometry, and profilometry techniques. The resulting assemblies are utilized for the construction and testing of novel solar cells. From stable and repeatable photocurrents generated during several "on-off" cycles of illumination, we derive monochromatic incident photo-to-current conversion efficiencies of around 3 %. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. A New Approach to Predict Microbial Community Assembly and Function Using a Stochastic, Genome-Enabled Modeling Framework

    Science.gov (United States)

    King, E.; Brodie, E.; Anantharaman, K.; Karaoz, U.; Bouskill, N.; Banfield, J. F.; Steefel, C. I.; Molins, S.

    2016-12-01

    Characterizing and predicting the microbial and chemical compositions of subsurface aquatic systems necessitates an understanding of the metabolism and physiology of organisms that are often uncultured or studied under conditions not relevant for one's environment of interest. Cultivation-independent approaches are therefore important and have greatly enhanced our ability to characterize functional microbial diversity. The capability to reconstruct genomes representing thousands of populations from microbial communities using metagenomic techniques provides a foundation for development of predictive models for community structure and function. Here, we discuss a genome-informed stochastic trait-based model incorporated into a reactive transport framework to represent the activities of coupled guilds of hypothetical microorganisms. Metabolic pathways for each microbe within a functional guild are parameterized from metagenomic data with a unique combination of traits governing organism fitness under dynamic environmental conditions. We simulate the thermodynamics of coupled electron donor and acceptor reactions to predict the energy available for cellular maintenance, respiration, biomass development, and enzyme production. While `omics analyses can now characterize the metabolic potential of microbial communities, it is functionally redundant as well as computationally prohibitive to explicitly include the thousands of recovered organisms into biogeochemical models. However, one can derive potential metabolic pathways from genomes along with trait-linkages to build probability distributions of traits. These distributions are used to assemble groups of microbes that couple one or more of these pathways. From the initial ensemble of microbes, only a subset will persist based on the interaction of their physiological and metabolic traits with environmental conditions, competing organisms, etc. Here, we analyze the predicted niches of these hypothetical microbes and

  3. Multilayered Polymer Coated Carbon Nanotubes to Deliver Dasatinib

    Science.gov (United States)

    Moore, Thomas L.; Grimes, Stuart W.; Lewis, Robert L.; Alexis, Frank

    2014-01-01

    Multilayered, multifunctional polymer coatings were grafted onto carbon nanotubes (CNT) using a one-pot, ring-opening polymerization in order to control the release kinetic and therapeutic efficacy of dasatinib. Biocompatible, biodegradable multilayered coatings composed of poly(glycolide) (PGA), and poly(lactide) (PLA) were polymerized directly onto hydroxyl-functionalized CNT surfaces. Sequential addition of monomers into the reaction vessel enabled multilayered coatings of PLA-PGA, or PGA-PLA. Poly(ethylene glycol) capped the polymer chain ends, resulting in a multifunctional amphiphilic coating. Multilayer polymer coatings on CNTs enabled control of anticancer dasatinib’s release kinetics and enhanced the in vitro therapeutic efficacy against U-87 glioblastoma compared to monolayer polymer coatings. PMID:24294824

  4. Multilayered polymer-coated carbon nanotubes to deliver dasatinib.

    Science.gov (United States)

    Moore, Thomas L; Grimes, Stuart W; Lewis, Robert L; Alexis, Frank

    2014-01-06

    Multilayered, multifunctional polymer coatings were grafted onto carbon nanotubes (CNTs) using a one-pot, ring-opening polymerization in order to control the release kinetic and therapeutic efficacy of dasatinib. Biocompatible, biodegradable multilayered coatings composed of poly(glycolide) (PGA) and poly(lactide) (PLA) were polymerized directly onto hydroxyl-functionalized CNT surfaces. Sequential addition of monomers into the reaction vessel enabled multilayered coatings of PLA-PGA or PGA-PLA. Poly(ethylene glycol) capped the polymer chain ends, resulting in a multifunctional amphiphilic coating. Multilayer polymer coatings on CNTs enabled control of the anticancer drug dasatinib's release kinetics and enhanced the in vitro therapeutic efficacy against U-87 glioblastoma compared to monolayer polymer coatings.

  5. The cryo-EM structure of YjeQ bound to the 30S subunit suggests a fidelity checkpoint function for this protein in ribosome assembly

    Science.gov (United States)

    Razi, Aida; Guarné, Alba; Ortega, Joaquin

    2017-01-01

    Recent work suggests that bacterial YjeQ (RsgA) participates in the late stages of assembly of the 30S subunit and aids the assembly of the decoding center but also binds the mature 30S subunit with high affinity. To determine the function and mechanisms of YjeQ in the context of the mature subunit, we determined the cryo-EM structure of the fully assembled 30S subunit in complex with YjeQ at 5.8-Å resolution. We found that binding of YjeQ stabilizes helix 44 into a conformation similar to that adopted by the subunit during proofreading. This finding indicates that, along with acting as an assembly factor, YjeQ has a role as a checkpoint protein, consisting of testing the proofreading ability of the 30S subunit. The structure also informs the mechanism by which YjeQ implements the release from the 30S subunit of a second assembly factor, called RbfA. Finally, it reveals how the 30S subunit stimulates YjeQ GTPase activity and leads to release of the protein. Checkpoint functions have been described for eukaryotic ribosome assembly factors; however, this work describes an example of a bacterial assembly factor that tests a specific translation mechanism of the 30S subunit. PMID:28396444

  6. Magnetic metallic multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Hood, Randolph Quentin [Univ. of California, Berkeley, CA (United States)

    1994-04-01

    Utilizing self-consistent Hartree-Fock calculations, several aspects of multilayers and interfaces are explored: enhancement and reduction of the local magnetic moments, magnetic coupling at the interfaces, magnetic arrangements within each film and among non-neighboring films, global symmetry of the systems, frustration, orientation of the various moments with respect to an outside applied field, and magnetic-field induced transitions. Magnetoresistance of ferromagnetic-normal-metal multilayers is found by solving the Boltzmann equation. Results explain the giant negative magnetoresistance encountered in these systems when an initial antiparallel arrangement is changed into a parallel configuration by an external magnetic field. The calculation depends on (1) geometric parameters (thicknesses of layers), (2) intrinsic metal parameters (number of conduction electrons, magnetization, and effective masses in layers), (3) bulk sample properties (conductivity relaxation times), (4) interface scattering properties (diffuse scattering versus potential scattering at the interfaces, and (5) outer surface scattering properties (specular versus diffuse surface scattering). It is found that a large negative magnetoresistance requires considerable asymmetry in interface scattering for the two spin orientations. Features of the interfaces that may produce an asymmetrical spin-dependent scattering are studied: varying interfacial geometric random roughness with no lateral coherence, correlated (quasi-periodic) roughness, and varying chemical composition of the interfaces. The interplay between these aspects of the interfaces may enhance or suppress the magnetoresistance, depending on whether it increases or decreases the asymmetry in the spin-dependent scattering of the conduction electrons.

  7. Ultrahard Multilayer Coatings

    Energy Technology Data Exchange (ETDEWEB)

    Chrzan, D.C.; Dugger, M.; Follstaedt, D.M.; Friedman, Lawrence H.; Friedmann, T.A.; Knapp, J.A.; McCarty, K.F.; Medlin, D.L.; Mirkarimi, P.B.; Missert, N.; Newcomer, P.P.; Sullivan, J.P.; Tallant, D.R.

    1999-05-01

    We have developed a new multilayer a-tC material that is thick stress-free, adherent, low friction, and with hardness and stiffness near that of diamond. The new a-tC material is deposited by J pulsed-laser deposition (PLD) at room temperature, and fully stress-relieved by a short thermal anneal at 600°C. A thick multilayer is built up by repeated deposition and annealing steps. We measured 88 GPa hardness, 1100 GPa Young's modulus, and 0.1 friction coefficient (under high load). Significantly, these results are all well within the range reported for crystalline diamond. In fact, this material, if considered separate from crystalline diamond, is the 2nd hardest material known to man. Stress-free a-tC also has important advantages over thin film diamond; namely, it is smooth, processed at lower temperature, and can be grown on a much broader range of substrates. This breakthrough will enable a host of applications that we are actively pursuing in MEMs, sensors, LIGA, etc.

  8. Dithiocarbamate Self-Assembled Monolayers as Efficient Surface Modifiers for Low Work Function Noble Metals

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, Dominik; Schäfer, Tobias; Schulz, Philip; Jung, Sebastian; Rittich, Julia; Mokros, Daniel; Segger, Ingolf; Maercks, Franziska; Effertz, Christian; Mazzarello, Riccardo; Wuttig, Matthias

    2016-09-06

    Tuning the work function of the electrode is one of the crucial steps to improve charge extraction in organic electronic devices. Here, we show that N,N-dialkyl dithiocarbamates (DTC) can be effectively employed to produce low work function noble metal electrodes. Work functions between 3.1 and 3.5 eV are observed for all metals investigated (Cu, Ag, and Au). Ultraviolet photoemission spectroscopy (UPS) reveals a maximum decrease in work function by 2.1 eV as compared to the bare metal surface. Electronic structure calculations elucidate how the complex interplay between intrinsic dipoles and dipoles induced by bond formation generates such large work function shifts. Subsequently, we quantify the improvement in contact resistance of organic thin film transistor devices with DTC coated source and drain electrodes. These findings demonstrate that DTC molecules can be employed as universal surface modifiers to produce stable electrodes for electron injection in high performance hybrid organic optoelectronics.

  9. Study on work function change of ITO modified by using a self-assembled monolayer for organic based devices

    Energy Technology Data Exchange (ETDEWEB)

    Jee, Seung Hyun; Kim, Soo Ho; Ko, Jae Hwan; Yoon, Young Soo [Konkuk University, Seoul (Korea, Republic of)

    2006-11-15

    The surface of Indium tin oxide (ITO) used as an electrode in organic light emitting diodes (OLEDs) and organic thin film transistors (OTFTs) was modified by a self-assembled monolayer (SAM). In order to increase the work function of the electrode, we modified the surface of the ITO by immersion in solutions including various SAM materials, such as 4-chlorophenhyl trichlorosilane (4-CPTS), chloromethyl trichlorosilane (CMTS), 4-chlorophenyl phosphonic acid (4-CPPA), 3-nitrophenyl phosphonic acid (3-NPPA) and 2-chloroethyl phosphonic acid (2-CEPA), at room temperature. The work function changes of the ITO with a SAM were measured by using a Kelvin probe. A work function increase of 1.09 eV was observed in the ITO with CMTS. In addition, it was found by using X-ray photoelectron spectroscopy that an increase in oxygen bonding energy contributed to the work function increase of the ITO. Through a SAM process, the transmittance of the ITO with a SAM was not changed. Therefore, some possibility of ohmic contact was shown because the energy barrier was removed in an interface between the ITO and an organic layer (pentacene or TPD) in the OTFT or the OLED. The origin of the work function increase of the ITO with a SAM was analyzed by X-ray photoelectron spectroscopy. These results suggest that ITO with a SAM greatly increases the probability for high-performance OLEDs and OTFTs.

  10. Lipoproteins in Drosophila melanogaster—Assembly, Function, and Influence on Tissue Lipid Composition

    Science.gov (United States)

    Palm, Wilhelm; Sampaio, Julio L.; Brankatschk, Marko; Carvalho, Maria; Mahmoud, Ali; Shevchenko, Andrej; Eaton, Suzanne

    2012-01-01

    Interorgan lipid transport occurs via lipoproteins, and altered lipoprotein levels correlate with metabolic disease. However, precisely how lipoproteins affect tissue lipid composition has not been comprehensively analyzed. Here, we identify the major lipoproteins of Drosophila melanogaster and use genetics and mass spectrometry to study their assembly, interorgan trafficking, and influence on tissue lipids. The apoB-family lipoprotein Lipophorin (Lpp) is the major hemolymph lipid carrier. It is produced as a phospholipid-rich particle by the fat body, and its secretion requires Microsomal Triglyceride Transfer Protein (MTP). Lpp acquires sterols and most diacylglycerol (DAG) at the gut via Lipid Transfer Particle (LTP), another fat body-derived apoB-family lipoprotein. The gut, like the fat body, is a lipogenic organ, incorporating both de novo–synthesized and dietary fatty acids into DAG for export. We identify distinct requirements for LTP and Lpp-dependent lipid mobilization in contributing to the neutral and polar lipid composition of the brain and wing imaginal disc. These studies define major routes of interorgan lipid transport in Drosophila and uncover surprising tissue-specific differences in lipoprotein lipid utilization. PMID:22844248

  11. Thymine- and Adenine-Functionalized Polystyrene Form Self-Assembled Structures through Multiple Complementary Hydrogen Bonds

    Directory of Open Access Journals (Sweden)

    Yu-Shian Wu

    2014-06-01

    Full Text Available In this study, we investigated the self-assembly of two homopolymers of the same molecular weight, but containing complementary nucleobases. After employing nitroxide-mediated radical polymerization to synthesize poly(vinylbenzyl chloride, we converted the polymer into poly(vinylbenzyl azide through a reaction with NaN3 and then performed click chemistry with propargyl thymine and propargyl adenine to yield the homopolymers, poly(vinylbenzyl triazolylmethyl methylthymine (PVBT and poly(vinylbenzyl triazolylmethyl methyladenine (PVBA, respectively. This PVBT/PVBA blend system exhibited a single glass transition temperature over the entire range of compositions, indicative of a miscible phase arising from the formation of multiple strong complementary hydrogen bonds between the thymine and adenine groups of PVBT and PVBA, respectively; Fourier transform infrared and 1H nuclear magnetic resonance spectroscopy confirmed the presence of these noncovalent interactions. In addition, dynamic rheology, dynamic light scattering and transmission electron microscopy provided evidence for the formation of supramolecular network structures in these binary PVBT/PVBA blend systems.

  12. A Rationally Designed Connector for Assembly of Protein-Functionalized DNA Nanostructures.

    Science.gov (United States)

    Koßmann, Katja J; Ziegler, Cornelia; Angelin, Alessandro; Meyer, Rebecca; Skoupi, Marc; Rabe, Kersten S; Niemeyer, Christof M

    2016-06-16

    We report on the rational engineering of the binding interface of the self-ligating HaloTag protein to generate an optimized linker for DNA nanostructures. Five amino acids positioned around the active-site entry channel for the chlorohexyl ligand (CH) of the HaloTag protein were exchanged for positively charged lysine amino acids to produce the HOB (halo-based oligonucleotide binder) protein. HOB was genetically fused with the enzyme cytochrome P450 BM3, as well as with BMR, the separated reductase domain of BM3. The resulting HOB-fusion proteins revealed significantly improved rates in ligation with CH-modified oligonucleotides and DNA origami nanostructures. These results suggest that the efficient self-assembly of protein-decorated DNA structures can be greatly improved by fine-tuning of the electrostatic interactions between proteins and the negatively charged nucleic acid nanostructures. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Functionalized d-form self-assembling peptide hydrogels for bone regeneration

    Science.gov (United States)

    He, Bin; Ou, Yunsheng; Zhou, Ao; Chen, Shuo; Zhao, Weikang; Zhao, Jinqiu; Li, Hong; Zhu, Yong; Zhao, Zenghui; Jiang, Dianming

    2016-01-01

    Bone defects are very common in orthopedics, and there is great need to develop suitable bone grafts for transplantation in vivo. However, current bone grafts still encounter some limitations, including limited availability, immune rejection, poor osteoinduction and osteoconduction, poor biocompatibility and degradation properties, etc. Self-assembling peptide nanofiber scaffolds have emerged as an important substrate for cell culture and bone regeneration. We report on the structural features (eg, Congo red staining, circular dichroism spectroscopy, transmission electron microscopy, and rheometry assays) and osteogenic ability of d-RADA16-RGD peptide hydrogels (with or without basic fibroblast growth factor) due to the better stability of peptide bonds formed by these peptides compared with those formed by l-form peptides, and use them to fill the femoral condyle defect of Sprague Dawley rat model. The bone morphology change, two-dimensional reconstructions using microcomputed tomography, quantification of the microcomputed tomography analyses as well as histological analyses have demonstrated that RGD-modified d-form peptide scaffolds are able to enhance extensive bone regeneration. PMID:27114701

  14. Multilayer Piezoelectric Stack Actuator Characterization

    Science.gov (United States)

    Sherrit, Stewart; Jones, Christopher M.; Aldrich, Jack B.; Blodget, Chad; Bao, Xioaqi; Badescu, Mircea; Bar-Cohen, Yoseph

    2008-01-01

    Future NASA missions are increasingly seeking to use actuators for precision positioning to accuracies of the order of fractions of a nanometer. For this purpose, multilayer piezoelectric stacks are being considered as actuators for driving these precision mechanisms. In this study, sets of commercial PZT stacks were tested in various AC and DC conditions at both nominal and extreme temperatures and voltages. AC signal testing included impedance, capacitance and dielectric loss factor of each actuator as a function of the small-signal driving sinusoidal frequency, and the ambient temperature. DC signal testing includes leakage current and displacement as a function of the applied DC voltage. The applied DC voltage was increased to over eight times the manufacturers' specifications to investigate the correlation between leakage current and breakdown voltage. Resonance characterization as a function of temperature was done over a temperature range of -180C to +200C which generally exceeded the manufacturers' specifications. In order to study the lifetime performance of these stacks, five actuators from one manufacturer were driven by a 60volt, 2 kHz sine-wave for ten billion cycles. The tests were performed using a Lab-View controlled automated data acquisition system that monitored the waveform of the stack electrical current and voltage. The measurements included the displacement, impedance, capacitance and leakage current and the analysis of the experimental results will be presented.

  15. ATR FT-IR spectroscopy on Vmh2 hydrophobin self-assembled layers for Teflon membrane bio-functionalization

    Energy Technology Data Exchange (ETDEWEB)

    Portaccio, M., E-mail: marianna.portaccio@unina2.it [Dipartimento di Medicina Sperimentale – Seconda Università di Napoli, Via S.M. di Costantinopoli, 16-80134 Napoli (Italy); Gravagnuolo, A.M., E-mail: alfredomaria.gravagnuolo@unina.it [Dipartimento di Scienze Chimiche, Università “Federico II”, Via Cintia, 21- 80126 Napoli (Italy); Longobardi, S., E-mail: sara.longobardi@unina.it [Dipartimento di Scienze Chimiche, Università “Federico II”, Via Cintia, 21- 80126 Napoli (Italy); Giardina, P., E-mail: paola.giardina@unina.it [Dipartimento di Scienze Chimiche, Università “Federico II”, Via Cintia, 21- 80126 Napoli (Italy); Rea, I., E-mail: ilaria.rea@na.imm.cnr.it [Institute for Microelectronics and Microsystems, CNR, Via P. Castellino, 111-80131 Napoli (Italy); De Stefano, L., E-mail: luca.destefano@na.imm.cnr.it [Institute for Microelectronics and Microsystems, CNR, Via P. Castellino, 111-80131 Napoli (Italy); Cammarota, M., E-mail: marcella.cammarota@unina2.it [Dipartimento di Medicina Sperimentale – Seconda Università di Napoli, Via S.M. di Costantinopoli, 16-80134 Napoli (Italy); Lepore, M., E-mail: maria.lepore@unina2.it [Dipartimento di Medicina Sperimentale – Seconda Università di Napoli, Via S.M. di Costantinopoli, 16-80134 Napoli (Italy)

    2015-10-01

    Graphical abstract: - Highlights: • Hydrophobin self-assembled layers on Teflon in different preparation conditions were investigated. • ATR collection data geometry allowed samples examination without any particular preparation. • Amide content, lipid/amide and carbohydrate/amide ratios of the protein layer were estimated. • Secondary structure of protein was determined for the examined samples. • FT-IR demonstrated to be of extreme relevance in monitoring hydrophobin self-assembled layers preparation. - Abstract: Surface functionalization by layers of hydrophobins, amphiphilic proteins produced by fungi offers a promising and green strategy for fabrication of biomedical and bioanalytical devices. The layering process of the Vmh2 hydrophobin from Pleurotus ostreatus on Teflon membrane has been investigated by Attenuated Total Reflection Fourier Transform Infrared (ATR FT-IR) spectroscopy. In particular, protein layers obtained with hydrophobin purified with two different procedures and in various coating conditions have been examined. The layers have been characterized by quantifying the amide I and amide II band area together with the lipid/amide ratio and carbohydrate/amide ratio. This characterization can be very useful in evaluating the best purification strategy and coating conditions. Moreover the analysis of the secondary structure of the layered protein using the deconvolution procedure of amide I band indicate the prevalent contribution from β-sheet state. The results inferred by infrared spectroscopy have been also confirmed by scanning electron microscopy imaging.

  16. Dependence of optical and structural properties of ZnS and MgF{sub 2} multilayers as a function of the number of layers

    Energy Technology Data Exchange (ETDEWEB)

    Perales, F. [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, E-28049 Madrid (Spain); Soto, D., E-mail: dsoto@cajeme.cifus.uson.m [Departamento de Investigacion en Fisica, Universidad de Sonora, Apdo, Postal 5-088, Hermosillo, Sonora (Mexico); Heras, C. de las [Departamento de Fisica de Materiales and Instituto Nicolas Cabrera, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, E-28049, Madrid (Spain)

    2010-05-31

    In this paper, optical and structural properties of ZnS and MgF{sub 2} multilayers grown by thermal evaporation are studied. Effects of annealing at different temperatures on samples with different number of layers are investigated. The maximum of reflection is shifted to different wavelengths, depending on the number of layers of the annealed samples. Using X-ray diffraction analysis, structural properties have been studied, and grain size and microstrain have been obtained by the Scherrer-Wilson formula, with grain sizes ranging from 10 nm to 22 nm for MgF{sub 2} and from 0.9 nm to 210 nm for ZnS, and microstrain values from 2.5 x 10{sup -3} to 3 x 10{sup -3} for MgF{sub 2}, and from 1.2 x 10{sup -3} to 2.6 x 10{sup -3} for ZnS. Competition between crystallite size and microstrain is observed.

  17. Status of Functional Qualification System for Nuclear Valve Assembly in KIMM

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J. H.; Park, T. J.; Kim, Y. J. [Korea Institute of Machinery and Materials, Daejeon (Korea, Republic of)

    2016-05-15

    In this paper, the status of the test facility, the basic concept of the ASME QME-1 test, and the future work are presented. The measured performance parameter, such as pressure, temperature, flow rate, thrust, stroke, and time, is used for the maintenance method and the evaluation of the aging and fatigue in the operating valve. In these days, the survival of the safety related valve in severe accident is important issue. In Korea Institute of Machinery and Materials (KIMM), the functional facility and related Quality Assure (QA) system are made. In addition, the qualification research was made for the functional test of the valve as ASME QME-1. The methodology is based on the ASME QME-1 1997. But the future work for the ASME QME-1 2007 was performed. In real situation, the engineering work is needed for the functional test of the nuclear valve in QA system. So the research work for the qualification is needed. The functional qualification of the valve in the nuclear power plant is performed in KIMM The development of the research and facility required in the functional qualification is in progress. Now the functional qualification is possible domestically, that was impossible in previous time due to the lack of qualification technology and facility.

  18. Multicomponent assembly of fluorescent-tag functionalized ligands in metal-organic frameworks for sensing explosives.

    Science.gov (United States)

    Gole, Bappaditya; Bar, Arun Kumar; Mukherjee, Partha Sarathi

    2014-10-06

    Detection of trace amounts of explosive materials is significantly important for security concerns and pollution control. Four multicomponent metal-organic frameworks (MOFs-12, 13, 23, and 123) have been synthesized by employing ligands embedded with fluorescent tags. The multicomponent assembly of the ligands was utilized to acquire a diverse electronic behavior of the MOFs and the fluorescent tags were strategically chosen to enhance the electron density in the MOFs. The phase purity of the MOFs was established by PXRD, NMR spectroscopy, and finally by single-crystal XRD. Single-crystal structures of the MOFs-12 and 13 showed the formation of three-dimensional porous networks with the aromatic tags projecting inwardly into the pores. These electron-rich MOFs were utilized for detection of explosive nitroaromatic compounds (NACs) through fluorescence quenching with high selectivity and sensitivity. The rate of fluorescence quenching for all the MOFs follows the order of electron deficiency of the NACs. We also showed the detection of picric acid (PA) by luminescent MOFs is not always reliable and can be misleading. This attracts our attention to explore these MOFs for sensing picryl chloride (PC), which is as explosive as picric acid and used widely to prepare more stable explosives like 2,4,6-trinitroaniline from PA. Moreover, the recyclability and sensitivity studies indicated that these MOFs can be reused several times with parts per billion (ppb) levels of sensitivity towards PC and 2,4,6-trinitrotoluene (TNT). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Interface chemistry and molecular bonding of functional ethoxysilane-based self-assembled monolayers on magnesium surfaces.

    Science.gov (United States)

    Killian, Manuela S; Seiler, Steffen; Wagener, Victoria; Hahn, Robert; Ebensperger, Christina; Meyer, Bernd; Schmuki, Patrik

    2015-05-06

    The modification of magnesium implants with functional organic molecules is important for increasing the biological acceptance and for reducing the corrosion rate of the implant. In this work, we evaluated by a combined experimental and theoretical approach the adsorption strength and geometry of a functional self-assembled monolayer (SAM) of hydrolyzed (3-aminopropyl)triethoxysilane (APTES) molecules on a model magnesium implant surface. In time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS), only a minor amount of reverse attachment was observed. Substrate-O-Si signals could be detected, as well as other characteristic APTES fragments. The stability of the SAM upon heating in UHV was investigated additionally. Density-functional theory (DFT) calculations were used to explore the preferred binding mode and the most favorable binding configuration of the hydrolyzed APTES molecules on the hydroxylated magnesium substrate. Attachment of the molecules via hydrogen bonding or covalent bond formation via single or multiple condensation reactions were considered. The impact of the experimental conditions and the water concentration in the solvent on the thermodynamic stability of possible APTES binding modes is analyzed as a function of the water chemical potential of the environment. Finally, the influence of van der Waals contributions to the adsorption energy will be discussed.

  20. Understanding the effects of packing and chemical terminations on the optical excitations of azobenzene-functionalized self-assembled monolayers

    Science.gov (United States)

    Cocchi, Caterina; Draxl, Claudia

    2017-10-01

    In a first-principles study based on many-body perturbation theory, we analyze the optical excitations of azobenzene-functionalized self-assembled monolayers (SAMs) with increasing packing density and different terminations, considering for comparison the corresponding gas-phase molecules and dimers. Intermolecular coupling increases with the density of the chromophores independently of the functional groups. The intense π → π* resonance that triggers photo-isomerization is present in the spectra of isolated dimers and diluted SAMs, but it is almost completely washed out in tightly packed architectures. Intermolecular coupling is partially inhibited by mixing differently functionalized azobenzene derivatives, in particular when large groups are involved. In this way, the excitation band inducing the photo-isomerization process is partially preserved and the effects of dense packing partly counterbalanced. Our results suggest that a tailored design of azobenzene-functionalized SAMs which optimizes the interplay between the packing density of the chromophores and their termination can lead to significant improvements in the photo-switching efficiency of these systems.

  1. Effect of Small Molecule Osmolytes on the Self-Assembly and Functionality of Globular Protein-Polymer Diblock Copolymers

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Carla S.; Xu, Liza; Olsen, Bradley D. [MIT

    2013-12-05

    Blending the small molecule osmolytes glycerol and trehalose with the model globular protein–polymer block copolymer mCherry-b-poly(N-isopropyl acrylamide) (mCherry-b-PNIPAM) is demonstrated to improve protein functionality in self-assembled nanostructures. The incorporation of either additive into block copolymers results in functionality retention in the solid state of 80 and 100% for PNIPAM volume fractions of 40 and 55%, respectively. This represents a large improvement over the 50–60% functionality observed in the absence of any additive. Furthermore, glycerol decreases the thermal stability of block copolymer films by 15–20 °C, while trehalose results in an improvement in the thermal stability by 15–20 °C. These results suggest that hydrogen bond replacement is responsible for the retention of protein function but suppression or enhancement of thermal motion based on the glass transition of the osmolyte primarily determines thermal stability. While both osmolytes are observed to have a disordering effect on the nanostructure morphology with increasing concentration, this effect is less pronounced in materials with a larger polymer volume fraction. Glycerol preferentially localizes in the protein domains and swells the nanostructures, inducing disordering or a change in morphology depending on the PNIPAM coil fraction. In contrast, trehalose is observed to macrophase separate from the block copolymer, which results in nanodomains becoming more disordered without changing significantly in size.

  2. Material optimization of multi-layered enhanced nanostructures

    Science.gov (United States)

    Strobbia, Pietro

    The employment of surface enhanced Raman scattering (SERS)-based sensing in real-world scenarios will offer numerous advantages over current optical sensors. Examples of these advantages are the intrinsic and simultaneous detection of multiple analytes, among many others. To achieve such a goal, SERS substrates with throughput and reproducibility comparable to commonly used fluorescence sensors have to be developed. To this end, our lab has discovered a multi-layer geometry, based on alternating films of a metal and a dielectric, that amplifies the SERS signal (multi-layer enhancement). The advantage of these multi-layered structures is to amplify the SERS signal exploiting layer-to-layer interactions in the volume of the structures, rather than on its surface. This strategy permits an amplification of the signal without modifying the surface characteristics of a substrate, and therefore conserving its reproducibility. Multi-layered structures can therefore be used to amplify the sensitivity and throughput of potentially any previously developed SERS sensor. In this thesis, these multi-layered structures were optimized and applied to different SERS substrates. The role of the dielectric spacer layer in the multi-layer enhancement was elucidated by fabricating spacers with different characteristics and studying their effect on the overall enhancement. Thickness, surface coverage and physical properties of the spacer were studied. Additionally, the multi-layered structures were applied to commercial SERS substrates and to isolated SERS probes. Studies on the dependence of the multi-layer enhancement on the thickness of the spacer demonstrated that the enhancement increases as a function of surface coverage at sub-monolayer thicknesses, due to the increasing multi-layer nature of the substrates. For fully coalescent spacers the enhancement decreases as a function of thickness, due to the loss of interaction between proximal metallic films. The influence of the

  3. Functional connectivity among spike trains in neural assemblies during rat working memory task.

    Science.gov (United States)

    Xie, Jiacun; Bai, Wenwen; Liu, Tiaotiao; Tian, Xin

    2014-11-01

    Working memory refers to a brain system that provides temporary storage to manipulate information for complex cognitive tasks. As the brain is a more complex, dynamic and interwoven network of connections and interactions, the questions raised here: how to investigate the mechanism of working memory from the view of functional connectivity in brain network? How to present most characteristic features of functional connectivity in a low-dimensional network? To address these questions, we recorded the spike trains in prefrontal cortex with multi-electrodes when rats performed a working memory task in Y-maze. The functional connectivity matrix among spike trains was calculated via maximum likelihood estimation (MLE). The average connectivity value Cc, mean of the matrix, was calculated and used to describe connectivity strength quantitatively. The spike network was constructed by the functional connectivity matrix. The information transfer efficiency Eglob was calculated and used to present the features of the network. In order to establish a low-dimensional spike network, the active neurons with higher firing rates than average rate were selected based on sparse coding. The results show that the connectivity Cc and the network transfer efficiency Eglob vaired with time during the task. The maximum values of Cc and Eglob were prior to the working memory behavior reference point. Comparing with the results in the original network, the feature network could present more characteristic features of functional connectivity. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Nanopatterning of functional materials by gas phase pattern deposition of self-assembled molecular thin films in combination with electrodeposition.

    Science.gov (United States)

    George, Antony; Maijenburg, A Wouter; Nguyen, Minh Duc; Maas, Michiel G; Blank, Dave H A; ten Elshof, Johan E

    2011-10-18

    We present a general methodology to pattern functional materials on the nanometer scale using self-assembled molecular templates on conducting substrates. A soft lithographic gas phase edge patterning process using poly(dimethylsiloxane) molds was employed to form electrically isolating organosilane patterns of a few nanometer thickness and a line width that could be tuned by varying the time of deposition. Electrodeposition was employed to deposit patterns of Ni and ZnO on these prepatterned substrates. Deposition occurred only on patches of the substrate where no organosilane monolayer was present. The process is simple, inexpensive, and scalable to large areas. We achieved formation of metallic and oxide material patterns with a lateral resolution of 80 nm. © 2011 American Chemical Society

  5. Multi-layers castings

    Directory of Open Access Journals (Sweden)

    J. Szajnar

    2010-01-01

    Full Text Available In paper is presented the possibility of making of multi-layers cast steel castings in result of connection of casting and welding coating technologies. First layer was composite surface layer on the basis of Fe-Cr-C alloy, which was put directly in founding process of cast carbon steel 200–450 with use of preparation of mould cavity method. Second layer were padding welds, which were put with use of TIG – Tungsten Inert Gas surfacing by welding technology with filler on Ni matrix, Ni and Co matrix with wolfram carbides WC and on the basis on Fe-Cr-C alloy, which has the same chemical composition with alloy, which was used for making of composite surface layer. Usability for industrial applications of surface layers of castings were estimated by criterion of hardness and abrasive wear resistance of type metal-mineral.

  6. Self-assembly of palladium nanoparticles on functional TiO{sub 2} nanotubes for a nonenzymatic glucose sensor

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xianlan [School of Science, Honghe University, Mengzi, Yunnan 661100 (China); College of Chemistry, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350108 (China); Fujian Key Lab of Medical Instrument & Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); Li, Gang; Zhang, Guowei [School of Science, Honghe University, Mengzi, Yunnan 661100 (China); Hou, Keyu [College of Chemistry, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350108 (China); Fujian Key Lab of Medical Instrument & Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); Pan, Haibo, E-mail: hbpan@fzu.edu.cn [College of Chemistry, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350108 (China); Fujian Key Lab of Medical Instrument & Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); Du, Min [Fujian Key Lab of Medical Instrument & Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China)

    2016-05-01

    Polydiallyldimethylammonium chloride, PDDA, was used as a stabilizer and linker for functionalized TiO{sub 2} nanotubes (TiO{sub 2} NTs). Self-assembled process with palladium nanoparticles (NPs) was successfully synthesized and used for the oxidation of glucose on glassy carbon electrodes. Based on the voltammetric and amperometric results, Pd NPs efficiently catalyzed the oxidation of glucose at − 0.05 V in the presence of 0.1 M NaCl and showed excellent resistance toward interference poisoning from such interfering species as ascorbic acid, uric acid and urea. To further increase sensitivity, the Pd NPs-PDDA-TiO{sub 2} NTs/GCE was electrochemically treated with H{sub 2}SO{sub 4} and NaOH, the glucose oxidation current was magnified 2.5 times than that before pretreatments due to greatly enhancing the electron transport property of the sensor based on the increased defect sites and surface oxide species. In view of the physiological level of glucose, the wide linear concentration range of glucose (4 × 10{sup −7}–8 × 10{sup −4} M) with a detection limit of 8 × 10{sup −8} M (S/N = 3) was obviously good enough for clinical application. - Highlights: • PDDA was used as a stabilizer and linker for functionalized TiO{sub 2} nanotubes. • Self-assembled process with palladium nanoparticles was synthesized. • After treated both H{sub 2}SO{sub 4} and NaOH, the glucose response was magnified to 2.5 times. • The wide linear concentration range of glucose was obtained with a limit of 8 × 10{sup −8} M.

  7. FGL-functionalized self-assembling nanofiber hydrogel as a scaffold for spinal cord-derived neural stem cells

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jian [Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022 (China); Zheng, Jin [Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022 (China); Zheng, Qixin, E-mail: zheng-qx@163.com [Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022 (China); Wu, Yongchao; Wu, Bin; Huang, Shuai; Fang, Weizhi; Guo, Xiaodong [Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022 (China)

    2015-01-01

    A class of designed self-assembling peptide nanofiber scaffolds has been shown to be a good biomimetic material in tissue engineering. Here, we specifically made a new peptide hydrogel scaffold FGLmx by mixing the pure RADA{sub 16} and designer functional peptide RADA{sub 16}-FGL solution, and we analyzed the physiochemical properties of each peptide with atomic force microscopy (AFM) and circular dichroism (CD). In addition, we examined the biocompatibility and bioactivity of FGLmx as well as RADA{sub 16} scaffold on spinal cord-derived neural stem cells (SC-NSCs) isolated from neonatal rats. Our results showed that RADA{sub 16}-FGL displayed a weaker β-sheet structure and FGLmx could self-assemble into nanofibrous morphology. Moreover, we found that FGLmx was not only noncytotoxic to SC-NSCs but also promoted SC-NSC proliferation and migration into the three-dimensional (3-D) scaffold, meanwhile, the adhesion and lineage differentiation of SC-NSCs on FGLmx were similar to that on RADA{sub 16}. Our results indicated that the FGL-functionalized peptide scaffold might be very beneficial for tissue engineering and suggested its further application for spinal cord injury (SCI) repair. - Highlights: • RADA{sub 16} and RADA{sub 16}-FGL peptides were synthesized and characterized. • Rat spinal cord neural stem cells were successfully isolated and characterized. • We provided an induction method for mixed differentiation of neural stem cells. • FGL scaffold had good biocompatibility and bioactivity with neural stem cells.

  8. Cytoskeletal filament assembly and the control of cell spreading and function by extracellular matrix

    Science.gov (United States)

    Mooney, D. J.; Langer, R.; Ingber, D. E.

    1995-01-01

    This study was undertaken to analyze how cell binding to extracellular matrix produces changes in cell shape. We focused on the initial process of cell spreading that follows cell attachment to matrix and, thus, cell 'shape' changes are defined here in terms of alterations in projected cell areas, as determined by computerized image analysis. Cell spreading kinetics and changes in microtubule and actin microfilament mass were simultaneously quantitated in hepatocytes plated on different extracellular matrix substrata. The initial rate of cell spreading was highly dependent on the matrix coating density and decreased from 740 microns 2/h to 50 microns 2/h as the coating density was lowered from 1000 to 1 ng/cm2. At approximately 4 to 6 hours after plating, this initial rapid spreading rate slowed and became independent of the matrix density regardless of whether laminin, fibronectin, type I collagen or type IV collagen was used for cell attachment. Analysis of F-actin mass revealed that cell adhesion to extracellular matrix resulted in a 20-fold increase in polymerized actin within 30 minutes after plating, before any significant change in cell shape was observed. This was followed by a phase of actin microfilament disassembly which correlated with the most rapid phase of cell extension and ended at about 6 hours; F-actin mass remained relatively constant during the slow matrix-independent spreading phase. Microtubule mass increased more slowly in spreading cells, peaking at 4 hours, the time at which the transition between rapid and slow spreading rates was observed. However, inhibition of this early rise in microtubule mass using either nocodazole or cycloheximide did not prevent this transition. Use of cytochalasin D revealed that microfilament integrity was absolutely required for hepatocyte spreading whereas interference with microtubule assembly (using nocodazole or taxol) or protein synthesis (using cycloheximide) only partially suppressed cell extension. In

  9. New bioactive motifs and their use in functionalized self-assembling peptides for NSC differentiation and neural tissue engineering

    Science.gov (United States)

    Gelain, F.; Cigognini, D.; Caprini, A.; Silva, D.; Colleoni, B.; Donegá, M.; Antonini, S.; Cohen, B. E.; Vescovi, A.

    2012-04-01

    Developing functionalized biomaterials for enhancing transplanted cell engraftment in vivo and stimulating the regeneration of injured tissues requires a multi-disciplinary approach customized for the tissue to be regenerated. In particular, nervous tissue engineering may take a great advantage from the discovery of novel functional motifs fostering transplanted stem cell engraftment and nervous fiber regeneration. Using phage display technology we have discovered new peptide sequences that bind to murine neural stem cell (NSC)-derived neural precursor cells (NPCs), and promote their viability and differentiation in vitro when linked to LDLK12 self-assembling peptide (SAPeptide). We characterized the newly functionalized LDLK12 SAPeptides via atomic force microscopy, circular dichroism and rheology, obtaining nanostructured hydrogels that support human and murine NSC proliferation and differentiation in vitro. One functionalized SAPeptide (Ac-FAQ), showing the highest stem cell viability and neural differentiation in vitro, was finally tested in acute contusive spinal cord injury in rats, where it fostered nervous tissue regrowth and improved locomotor recovery. Interestingly, animals treated with the non-functionalized LDLK12 had an axon sprouting/regeneration intermediate between Ac-FAQ-treated animals and controls. These results suggest that hydrogels functionalized with phage-derived peptides may constitute promising biomimetic scaffolds for in vitro NSC differentiation, as well as regenerative therapy of the injured nervous system. Moreover, this multi-disciplinary approach can be used to customize SAPeptides for other specific tissue engineering applications.Developing functionalized biomaterials for enhancing transplanted cell engraftment in vivo and stimulating the regeneration of injured tissues requires a multi-disciplinary approach customized for the tissue to be regenerated. In particular, nervous tissue engineering may take a great advantage from the

  10. Recycling of Polymer-Based Multilayer Packaging: A Review

    Directory of Open Access Journals (Sweden)

    Katharina Kaiser

    2017-12-01

    Full Text Available Polymer-based multilayer packaging materials are commonly used in order to combine the respective performance of different polymers. By this approach, the tailored functionality of packaging concepts is created to sufficiently protect sensitive food products and thus obtain extended shelf life. However, because of their poor recyclability, most multilayers are usually incinerated or landfilled, counteracting the efforts towards a circular economy and crude oil independency. This review depicts the current state of the European multilayer packaging market and sketches the current end-of-life situation of postconsumer multilayer packaging waste in Germany. In the main section, a general overview of the state of research about material recycling of different multilayer packaging systems is provided. It is divided into two subsections, whereby one describes methods to achieve a separation of the different components, either by delamination or the selective dissolution–reprecipitation technique, and the other describes methods to achieve recycling by compatibilization of nonmiscible polymer types. While compatibilization methods and the technique of dissolution–reprecipitation are already extensively studied, the delamination of packaging has not been investigated systematically. All the presented options are able to recycle multilayer packaging, but also have drawbacks like a limited scope or a high expenditure of energy.

  11. Finite-element modelling of multilayer X-ray optics.

    Science.gov (United States)

    Cheng, Xianchao; Zhang, Lin

    2017-05-01

    Multilayer optical elements for hard X-rays are an attractive alternative to crystals whenever high photon flux and moderate energy resolution are required. Prediction of the temperature, strain and stress distribution in the multilayer optics is essential in designing the cooling scheme and optimizing geometrical parameters for multilayer optics. The finite-element analysis (FEA) model of the multilayer optics is a well established tool for doing so. Multilayers used in X-ray optics typically consist of hundreds of periods of two types of materials. The thickness of one period is a few nanometers. Most multilayers are coated on silicon substrates of typical size 60 mm × 60 mm × 100-300 mm. The high aspect ratio between the size of the optics and the thickness of the multilayer (10 7 ) can lead to a huge number of elements for the finite-element model. For instance, meshing by the size of the layers will require more than 10 16 elements, which is an impossible task for present-day computers. Conversely, meshing by the size of the substrate will produce a too high element shape ratio (element geometry width/height > 10 6 ), which causes low solution accuracy; and the number of elements is still very large (10 6 ). In this work, by use of ANSYS layer-functioned elements, a thermal-structural FEA model has been implemented for multilayer X-ray optics. The possible number of layers that can be computed by presently available computers is increased considerably.

  12. Finite-element modelling of multilayer X-ray optics

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Xianchao; Zhang, Lin

    2017-04-11

    Multilayer optical elements for hard X-rays are an attractive alternative to crystals whenever high photon flux and moderate energy resolution are required. Prediction of the temperature, strain and stress distribution in the multilayer optics is essential in designing the cooling scheme and optimizing geometrical parameters for multilayer optics. The finite-element analysis (FEA) model of the multilayer optics is a well established tool for doing so. Multilayers used in X-ray optics typically consist of hundreds of periods of two types of materials. The thickness of one period is a few nanometers. Most multilayers are coated on silicon substrates of typical size 60 mm × 60 mm × 100–300 mm. The high aspect ratio between the size of the optics and the thickness of the multilayer (107) can lead to a huge number of elements for the finite-element model. For instance, meshing by the size of the layers will require more than 1016elements, which is an impossible task for present-day computers. Conversely, meshing by the size of the substrate will produce a too high element shape ratio (element geometry width/height > 106), which causes low solution accuracy; and the number of elements is still very large (106). In this work, by use of ANSYS layer-functioned elements, a thermal-structural FEA model has been implemented for multilayer X-ray optics. The possible number of layers that can be computed by presently available computers is increased considerably.

  13. Nanoscale mono- and multi-layer cylinder structures formed by recombinant S-layer proteins of mosquitocidal Bacillus sphaericus C3-41.

    Science.gov (United States)

    Li, Jia; Yang, Lingling; Hu, Xiaomin; Zheng, Dasheng; Yan, Jianpin; Yuan, Zhiming

    2013-08-01

    The mature surface layer (S-layer) protein SlpC of mosquitocidal Bacillus sphaericus C3-41 comprises amino acids 31-1,176 and could recrystallize in vitro. The N-terminal SLH domain is responsible for binding function. Deletion of this part, S-layer proteins could not bind to the cell wall sacculi. To investigate the self-assembly ability of SlpC from B. sphaericus, nine truncations were constructed and their self-assembly properties were compared with the recombinant mature S-layer protein rSlpC₃₁₋₁,₁₇₆. The results showed that rSbsC₃₁₋₁,₁₇₆ and truncations rSlpC₂₁₁₋₁,₁₇₆, rSlpC₂₇₈₋₁,₁₇₆, rSlpC₃₁₋₁,₁₀₀, and rSlpC₃₁₋₁,₀₅₀ could assemble into multilayer cylinder structures, while N-terminal truncations rSlpC₃₃₈₋₁,₁₇₆, rSlpC₄₃₈₋₁,₁₇₆, and rSlpC₄₉₈₋₁,₁₇₆ mainly showed monolayer cylinders in recombinant Escherichia coli BL21 (DE3) cells. Growth phase analysis of the self-assembly process revealed that rSlpC₄₉₈₋₁,₁₇₆ mainly formed monolayer cylinders in the early stage (0.5 and 1 h induction of expression), but few double-layer or multilayer cylinders were also found with the cells growing, while rSlpC₃₁₋₁,₁₇₆ could formed multilayer cylinders in all the growth stage in the E. coli cells. It is concluded that the deletion of the C-terminal 126 aa or the N-terminal 497 aa did not interfere with the self-assembly process, the fragment (amino acids 278 to 337) is essential for the multilayer cylinder formation in E. coli BL21 (DE3) cells in the early stage and the fragment (amino acids 338 to 497) is related to monolayer cylinder formation. The information is important for further studies on the assembly mechanism of S-layer proteins and forms a basis for further studies concerning surface display and nanobiotechnology.

  14. 133 Structural basis for ebolavirus matrix assembly and budding; protein plasticity allows multiple functions

    OpenAIRE

    Bornholdt, Zachary; Noda, Takeshi; Abelson, Dafna; Halfmann, Peter; Wood, Malcolm; Kawaoa, Yoshihiro; Saphire, Erica Ollmann

    2014-01-01

    Proteins, particularly viral proteins, can be multifunctional, but the mechanism(s) behind this trait are not fully understood. Here, we illustrate through multiple crystal structures, biochemistry and cellular microscopy that the Ebola virus VP40 protein rearranges into different structures, each with a distinct and essential function required for the ebolavirus life cycle. A butterfly-shaped VP40 dimer trafficks to the cellular membrane. There, electrostatic interactions trigger rearrangeme...

  15. Structural basis for ebolavirus matrix assembly and budding; protein plasticity allows multiple functions

    OpenAIRE

    Zachary A Bornholdt; Noda, Takeshi; Abelson, Dafna M.; Halfmann, Peter; Wood, Malcolm; Kawaoka, Yoshihiro; Saphire, Erica Ollmann

    2013-01-01

    Proteins, particularly viral proteins, can be multifunctional, but the mechanism(s) behind this trait are not fully understood. Here, we illustrate through multiple crystal structures, biochemistry and cellular microscopy that VP40 rearranges into different structures, each with a distinct function required for the ebolavirus life cycle. A butterfly-shaped VP40 dimer trafficks to the cellular membrane. There, electrostatic interactions trigger rearrangement of the polypeptide into a linear he...

  16. Decoupling phylogenetic and functional diversity to reveal hidden signals in community assembly

    Czech Academy of Sciences Publication Activity Database

    de Bello, Francesco; Šmilauer, P.; Diniz-Filho, J. A. F.; Carmona, C. P.; Lososová, Z.; Herben, Tomáš; Götzenberger, Lars

    2017-01-01

    Roč. 8, č. 10 (2017), s. 1200-1211 ISSN 2041-210X R&D Projects: GA ČR(CZ) GA16-15012S; GA ČR GB14-36079G EU Projects: European Commission(XE) 267243 Institutional support: RVO:67985939 Keywords : community ecology * phylogenetic diversity * functional diversity Subject RIV: EH - Ecology, Behaviour OBOR OECD: Ecology Impact factor: 5.708, year: 2016

  17. Establishing Antibacterial Multilayer Films on the Surface of Direct Metal Laser Sintered Titanium Primed with Phase-Transited Lysozyme

    Science.gov (United States)

    Guan, Binbin; Wang, Haorong; Xu, Ruiqing; Zheng, Guoying; Yang, Jie; Liu, Zihao; Cao, Man; Wu, Mingyao; Song, Jinhua; Li, Neng; Li, Ting; Cai, Qing; Yang, Xiaoping; Li, Yanqiu; Zhang, Xu

    2016-11-01

    Direct metal laser sintering is a technology that allows the fabrication of titanium (Ti) implants with a functional gradation of porosity and surface roughness according to three-dimensional (3D) computer data. The surface roughness of direct metal laser sintered titanium (DMLS-Ti) implants may provide abundant binding sites for bacteria. Bacterial colonization and subsequent biofilm formation can cause unsatisfactory cell adhesion and implant-related infections. To prevent such infections, a novel phase-transited lysozyme (PTL) was utilized as an initial functional layer to simply and effectively prime DMLS-Ti surfaces for subsequent coating with antibacterial multilayers. The purpose of the present study was to establish a surface with dual biological functionality. The minocycline-loaded polyelectrolyte multilayers of hyaluronic acid (HA) and chitosan (CS) formed via a layer-by-layer (LbL) self-assembly technique on PTL-functionalized DMLS-Ti were designed to inhibit pathogenic microbial infections while allowing the DMLS-Ti itself and the modified coatings to retain acceptable biocompatibility. The experimental results indicate that the DMLS-Ti and the hydrogel treated surfaces can inhibit early bacterial adhesion while completely preserving osteoblast functions. This design is expected to gain considerable interest in the medical field and to have good potential for applications in multifunctional DMLS-Ti implants.

  18. Multi-layered proton-conducting electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Tae H.; Dorris, Stephen E.; Balachandran, Uthamalingam

    2017-06-27

    The present invention provides a multilayer anode/electrolyte assembly comprising a porous anode substrate and a layered solid electrolyte in contact therewith. The layered solid electrolyte includes a first dense layer of yttrium-doped barium zirconate (BZY), optionally including another metal besides Y, Ba, and Zr (e.g., a lanthanide metal such as Pr) on one surface thereof, a second dense layer of yttrium-doped barium cerate (BCY), and an interfacial layer between and contacting the BZY and BCY layers. The interfacial layer comprises a solid solution of the BZY and BCY electrolytes. The porous anode substrate comprises at least one porous ceramic material that is stable to carbon dioxide and water (e.g., porous BZY), as well as an electrically conductive metal and/or metal oxide (e.g., Ni, NiO, and the like).

  19. Optical transmittance of multilayer graphene

    OpenAIRE

    Zhu, Shou-En; Yuan, Shengjun; Janssen, G.C.A.M.

    2014-01-01

    We study the optical transmittance of multilayer graphene films up to 65 layers thick. By combing large-scale tight-binding simulation and optical measurement on CVD multilayer graphene, the optical transmission through graphene films in the visible region is found to be solely determined by the number of graphene layers. We argue that the optical transmittance measurement is more reliable in the determination of the number of layers than the commonly used Raman Spectroscopy. Moreover, optica...

  20. A bisphenol A sensor based on novel self-assembly of zinc phthalocyanine tetrasulfonic acid-functionalized graphene nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Keyu [Fujian Key Lab of Medical Instrument & Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); Institute of Research for Functional Materials, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); College of Chemistry, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350116 (China); Huang, Lei; Qi, Yongbo [Institute of Research for Functional Materials, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); College of Chemistry, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350116 (China); Huang, Caixia [Fujian Key Lab of Medical Instrument & Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); Institute of Research for Functional Materials, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); College of Chemistry, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350116 (China); Pan, Haibo, E-mail: hbpan@fzu.edu.cn [Fujian Key Lab of Medical Instrument & Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); Institute of Research for Functional Materials, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); College of Chemistry, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350116 (China); Du, Min [Fujian Key Lab of Medical Instrument & Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China)

    2015-04-01

    In this work, a novel zinc phthalocyanine tetrasulfonic acid (ZnTsPc)-functionalized graphene nanocomposites (f-GN) was synthesized by a simple and efficient electrostatic self-assembly method, where the positive charged GN decorated by (3-aminopropyl) triethoxysilane (APTES) was self-assemblied with ZnTsPc, a two dimensional (2-D) molecules. It not only enhanced its stability for the hybrid structure, but also avoided the reaggregation of ZnTsPc or f-GN themselves. Based on layered ZnTsPc/f-GN nanocomposites modified glassy carbon electrode, a rapid and sensitive sensor was developed for the determination of bisphenol A (BPA). Under the optimal conditions, the oxidation peak current increased linearly with the concentration of BPA in the range of 5.0 × 10{sup −8} to 4.0 × 10{sup −6} M with correlation coefficient 0.998 and limits of detection 2.0 × 10{sup −8} M. Due to high absorption nature for BPA and electron deficiency on ZnTsPc/f-GN, it presented the unique electron pathway arising from π–π stackable interaction during redox process for detecting BPA. The sensor exhibited remarkable long-term stability, good anti-interference and excellent electrocatalytic activity towards BPA detection. - Graphical abstract: 2-D ZnTsPc/f-GN architecture with high BPA absorption efficiency and excellent catalysis of central metal in ZnTsPc was highly promising for BPA sensor. - Highlights: • 2-D ZnTsPc/f-GN architecture was synthesized by electrostatic self-assembly method. • ZnTsPc/f-GN nanocomposites avoided the reaggregation of ZnTsPc and f-GN themselves. • An electrochemical BPA sensor was developed based on ZnTsPc/f-GN nanocomposites. • High absorption for BPA and electron deficiency on the surface of ZnTsPc/f-GN • The proposed sensor could be applied for detection of BPA in real samples.

  1. Engineering and Design of Polymeric Shells: Inwards Interweaving Polymers as Multilayer Nanofilm, Immobilization Matrix, or Chromatography Resins.

    Science.gov (United States)

    Pan, Houwen Matthew; Yu, Han; Guigas, Gernot; Fery, Andreas; Weiss, Matthias; Patzel, Volker; Trau, Dieter

    2017-02-15

    Hydrogels with complex internal structures are required for advanced drug delivery systems and tissue engineering or used as inks for 3D printing. However, hydrogels lack the tunability and diversity of polymeric shells and require complicated postsynthesis steps to alter its structure or properties. We report on the first integrated approach to assemble and design polymeric shells to take on various complex structures and functions such as multilayer nanofilms, multidensity immobilization matrix, or multiadhesive chromatography resins via the tuning of four assembly parameters: (a) poly(allylamine) (PA) concentration, (b) number of poly(allylamine)/poly(styrenesulfonic acid) (PA/PSSA) incubations, (c) poly(allylamine) (PA) to poly(ethylene glycol) (PEG) grafting ratio, and (d) % H2O present during assembly. Our approach combines the complex 3D structures of hydrogels with the versatility of self-assembled polymeric layers. Polymeric shells produced from our method have a highly uniform material distribution and well-defined shell boundaries. Shell thickness, density, and adhesive properties are easily tunable. By virtue of such unique material features, we demonstrate that polymeric shells can be designed to expand beyond its conventional function as thin films and serve as immobilization matrix, chromatography resins, or even reaction compartments. This technique could also uncover interesting perspectives in the development of novel multimaterials for 3D printing to synthesize scaffolds at a higher order of complexity.

  2. Functional characterization of sticholysin I and W111C mutant reveals the sequence of the actinoporin's pore assembly.

    Directory of Open Access Journals (Sweden)

    Valeria Antonini

    Full Text Available The use of pore-forming toxins in the construction of immunotoxins against tumour cells is an alternative for cancer therapy. In this protein family one of the most potent toxins are the actinoporins, cytolysins from sea anemones. We work on the construction of tumour proteinase-activated immunotoxins using sticholysin I (StI, an actinoporin isolated from the sea anemone Stichodactyla helianthus. To accomplish this objective, recombinant StI (StIr with a mutation in the membrane binding region has been employed. In this work, it was evaluated the impact of mutating tryptophan 111 to cysteine on the toxin pore forming capability. StI W111C is still able to permeabilize erythrocytes and liposomes, but at ten-fold higher concentration than StI. This is due to its lower affinity for the membrane, which corroborates the importance of residue 111 for the binding of actinoporins to the lipid bilayer. In agreement, other functional characteristics not directly associated to the binding, are essentially the same for both variants, that is, pores have oligomeric structures with similar radii, conductance, cation-selectivity, and instantaneous current-voltage behavior. In addition, this work provides experimental evidence sustaining the toroidal protein-lipid actinoporins lytic structures, since the toxins provoke the trans-bilayer movement (flip-flop of a pyrene-labeled analogue of phosphatidylcholine in liposomes, indicating the existence of continuity between the outer and the inner membrane leaflet. Finally, our planar lipid membranes results have also contributed to a better understanding of the actinoporin's pore assembly mechanism. After the toxin binding and the N-terminal insertion in the lipid membrane, the pore assembly occurs by passing through different transient sub-conductance states. These states, usually 3 or 4, are due to the successive incorporation of N-terminal α-helices and lipid heads to the growing pores until a stable toroidal

  3. Cationic β-cyclodextrin polymer applied to a dual cyclodextrin polyelectrolyte multilayer system.

    Science.gov (United States)

    Junthip, Jatupol; Tabary, Nicolas; Leclercq, Laurent; Martel, Bernard

    2015-08-01

    A polyelectrolyte multilayer film (PEM) based on cationic and anionic β-cyclodextrin polyelectrolytes was coated onto a textile substrate for future drug delivery purposes. We firstly synthesized a novel cationic β-cyclodextrin polymer (polyEPG-CD) by crosslinking β-cyclodextrin (βCD) with epichlorohydrin (EP) under basic conditions, in the presence of glycidyltrimetrylammonium chloride (GTMAC) as cationizing group. The influence of preparation conditions has been investigated in order to preferably obtain a water soluble fraction whose charge density and molecular weights were optimal for the layer-by-layer (LbL) deposition process. The different cationic cyclodextrin polymers obtained were characterized by FTIR, NMR, colloidal titration, conductimetry, thermogravimetric analysis and size exclusion chromatography. Besides, the counterpart polyelectrolyte was a β-cyclodextrin polymer crosslinked with citric acid, polyCTR-CD, whose synthesis and characterization have been previously reported. Finally we realized the Layer by Layer (LbL) build-up of the PEM coating onto the textile support, using the dip coating method, by alternatively soaking it in cationic polyEPG-CD and anionic polyCTR-CD solutions. This multilayer self-assembly was monitored by SEM, gravimetry and OWLS in function of both polyelectrolytes concentrations and ratios. Solutions parameters such as pH, ionic strenght were also discussed. Copyright © 2015 Elsevier Ltd. All rights reserved.

  4. Functionalized Nanostructures: Redox-Active Porphyrin Anchors for Supramolecular DNA Assemblies

    KAUST Repository

    Börjesson, Karl

    2010-09-28

    We have synthesized and studied a supramolecular system comprising a 39-mer DNA with porphyrin-modified thymidine nucleosides anchored to the surface of large unilamellar vesicles (liposomes). Liposome porphyrin binding characteristics, such as orientation, strength, homogeneity, and binding site size, was determined, suggesting that the porphyrin is well suited as a photophysical and redox-active lipid anchor, in comparison to the inert cholesterol anchor commonly used today. Furthermore, the binding characteristics and hybridization capabilities were studied as a function of anchor size and number of anchoring points, properties that are of importance for our future plans to use the addressability of these redox-active nodes in larger DNA-based nanoconstructs. Electron transfer from photoexcited porphyrin to a lipophilic benzoquinone residing in the lipid membrane was characterized by steady-state and time-resolved fluorescence and verified by femtosecond transient absorption. © 2010 American Chemical Society.

  5. Confine Clay in an Alternating Multilayered Structure through Injection Molding: A Simple and Efficient Route to Improve Barrier Performance of Polymeric Materials.

    Science.gov (United States)

    Yu, Feilong; Deng, Hua; Bai, Hongwei; Zhang, Qin; Wang, Ke; Chen, Feng; Fu, Qiang

    2015-05-20

    Various methods have been devoted to trigger the formation of multilayered structure for wide range of applications. These methods are often complicated with low production efficiency or require complex equipment. Herein, we demonstrate a simple and efficient method for the fabrication of polymeric sheets containing multilayered structure with enhanced barrier property through high speed thin-wall injection molding (HSIM). To achieve this, montmorillonite (MMT) is added into PE first, then blended with PP to fabricate PE-MMT/PP ternary composites. It is demonstrated that alternating multilayer structure could be obtained in the ternary composites because of low interfacial tension and good viscosity match between different polymer components. MMT is selectively dispersed in PE phase with partial exfoliated/partial intercalated microstructure. 2D-WAXD analysis indicates that the clay tactoids in PE-MMT/PP exhibits an uniplanar-axial orientation with their surface parallel to the molded part surface, while the tactoids in binary PE-MMT composites with the same overall MMT contents illustrate less orientation. The enhanced orientation of nanoclay in PE-MMT/PP could be attributed to the confinement of alternating multilayer structure, which prohibits the tumbling and rotation of nanoplatelets. Therefore, the oxygen barrier property of PE-MMT/PP is superior to that of PE-MMT because of increased gas permeation pathway. Comparing with the results obtained for PE based composites in literature, outstanding barrier property performance (45.7% and 58.2% improvement with 1.5 and 2.5 wt % MMT content, respectively) is achieved in current study. Two issues are considered responsible for such improvement: enhanced MMT orientation caused by the confinement in layered structure, and higher local density of MMT in layered structure induced denser assembly. Finally, enhancement in barrier property by confining impermeable filler into alternating multilayer structure through such

  6. Involvement of ribosomal protein L6 in assembly of functional 50S ribosomal subunit in Escherichia coli cells

    Energy Technology Data Exchange (ETDEWEB)

    Shigeno, Yuta [Division of Applied Biology, Faculty of Textile Science and Technology, Shinshu University, Ueda 386-8567 (Japan); Uchiumi, Toshio [Department of Biology, Faculty of Science, Niigata University, Niigata 950-2181 (Japan); Nomura, Takaomi, E-mail: nomurat@shinshu-u.ac.jp [Division of Applied Biology, Faculty of Textile Science and Technology, Shinshu University, Ueda 386-8567 (Japan)

    2016-04-22

    Ribosomal protein L6, an essential component of the large (50S) subunit, primarily binds to helix 97 of 23S rRNA and locates near the sarcin/ricin loop of helix 95 that directly interacts with GTPase translation factors. Although L6 is believed to play important roles in factor-dependent ribosomal function, crucial biochemical evidence for this hypothesis has not been obtained. We constructed and characterized an Escherichia coli mutant bearing a chromosomal L6 gene (rplF) disruption and carrying a plasmid with an arabinose-inducible L6 gene. Although this ΔL6 mutant grew more slowly than its wild-type parent, it proliferated in the presence of arabinose. Interestingly, cell growth in the absence of arabinose was biphasic. Early growth lasted only a few generations (LI-phase) and was followed by a suspension of growth for several hours (S-phase). This suspension was followed by a second growth phase (LII-phase). Cells harvested at both LI- and S-phases contained ribosomes with reduced factor-dependent GTPase activity and accumulated 50S subunit precursors (45S particles). The 45S particles completely lacked L6. Complete 50S subunits containing L6 were observed in all growth phases regardless of the L6-depleted condition, implying that the ΔL6 mutant escaped death because of a leaky expression of L6 from the complementing plasmid. We conclude that L6 is essential for the assembly of functional 50S subunits at the late stage. We thus established conditions for the isolation of L6-depleted 50S subunits, which are essential to study the role of L6 in translation. - Highlights: • We constructed an in vivo functional assay system for Escherichia coli ribosomal protein L6. • Growth of an E. coli ΔL6 mutant was biphasic when L6 levels were depleted. • The ΔL6 mutant accumulated 50S ribosomal subunit precursors that sedimented at 45S. • L6 is a key player in the late stage of E. coli 50S subunit assembly.

  7. Highly tunable interfacial adhesion of glass fiber by hybrid multilayers of graphene oxide and aramid nanofiber.

    Science.gov (United States)

    Park, Byeongho; Lee, Wonoh; Lee, Eunhee; Min, Sa Hoon; Kim, Byeong-Su

    2015-02-11

    The performance of fiber-reinforced composites is governed not only by the nature of each individual component comprising the composite but also by the interfacial properties between the fiber and the matrix. We present a novel layer-by-layer (LbL) assembly for the surface modification of a glass fiber to enhance the interfacial properties between the glass fiber and the epoxy matrix. Solution-processable graphene oxide (GO) and an aramid nanofiber (ANF) were employed as active components for the LbL assembly onto the glass fiber, owing to their abundant functional groups and mechanical properties. We found that the interfacial properties of the glass fibers uniformly coated with GO and ANF multilayers, such as surface free energy and interfacial shear strength, were improved by 23.6% and 39.2%, respectively, compared with those of the bare glass fiber. In addition, the interfacial adhesion interactions between the glass fiber and the epoxy matrix were highly tunable simply by changing the composition and the architecture of layers, taking advantage of the versatility of the LbL assembly.

  8. Self-assembled anchor layers/polysaccharide coatings on titanium surfaces: a study of functionalization and stability

    Directory of Open Access Journals (Sweden)

    Ognen Pop-Georgievski

    2015-03-01

    Full Text Available Composite materials based on a titanium support and a thin, alginate hydrogel could be used in bone tissue engineering as a scaffold material that provides biologically active molecules. The main objective of this contribution is to characterize the activation and the functionalization of titanium surfaces by the covalent immobilization of anchoring layers of self-assembled bisphosphonate neridronate monolayers and polymer films of 3-aminopropyltriethoxysilane and biomimetic poly(dopamine. These were further used to bind a bio-functional alginate coating. The success of the titanium surface activation, anchoring layer formation and alginate immobilization, as well as the stability upon immersion under physiological-like conditions, are demonstrated by different surface sensitive techniques such as spectroscopic ellipsometry, infrared reflection–absorption spectroscopy and X-ray photoelectron spectroscopy. The changes in morphology and the established continuity of the layers are examined by scanning electron microscopy, surface profilometry and atomic force microscopy. The changes in hydrophilicity after each modification step are further examined by contact angle goniometry.

  9. Orientation and Mg Incorporation of Calcite Grown on Functionalized Self-Assembled Monolayers: A Synchrotron X-ray Study

    Energy Technology Data Exchange (ETDEWEB)

    Kwak,S.; DiMasi, E.; Han, Y.; Aizenberg, J.; Kuzmenko, I.

    2005-01-01

    Calcite crystals were nucleated from MgCl2/CaCl2 solutions onto functionalized self-assembled monolayers adsorbed onto E-beam evaporated Au films. Synchrotron X-ray scattering studies of the crystals reveal new information about preferred orientation and Mg incorporation. The Au [111] axis is distributed within 2.6 degrees of the film surface normal, but the oriented crystals may be tilted up to 6 degrees away from this axis. For low Mg{sup 2+} content, SO{sub 3}--functionalized films nucleated primarily near the (106) calcite face, odd-chain-length carboxylic acid terminated alkanethiol films nucleated near the (012) face, and even-chain-length carboxylic acid terminated alkanethiol films nucleated near the (113) face. [Mg{sup 2+}]/[Ca{sup 2+}] concentration ratios (n) of 2 and greater defeated this preferred orientation and created a powder texture. Diffraction patterns within the layer plane from the coarse calcite powders indicated a shift to higher 2 accompanied by peak broadening with increasing n. For 0.5 < n < 3.5, a double set of calcite peaks is observed, showing that two distinct Mg calcite phases form: one of comparatively lower Mg content, derived from the templated crystals, and a Mg-rich phase derived from amorphous precursor particles. According to the refinement of lattice parameters, Mg incorporation of up to 18 mol % occurs for n = 4, independent of film functionality. We discuss the differences between the differently functionalized monolayers and also introduce the hypothesis that two separate routes to Mg calcite formation occur in this system.

  10. Titanium Surface Priming with Phase-Transited Lysozyme to Establish a Silver Nanoparticle-Loaded Chitosan/Hyaluronic Acid Antibacterial Multilayer via Layer-by-Layer Self-Assembly

    OpenAIRE

    Xue Zhong; Yunjia Song; Peng Yang; Yao Wang; Shaoyun Jiang; Xu Zhang; Changyi Li

    2016-01-01

    Objectives The formation of biofilm around implants, which is induced by immediate bacterial colonization after installation, is the primary cause of post-operation infection. Initial surface modification is usually required to incorporate antibacterial agents on titanium (Ti) surfaces to inhibit biofilm formation. However, simple and effective priming methods are still lacking for the development of an initial functional layer as a base for subsequent coatings on titanium surfaces. The purpo...

  11. Density Functional Investigation of the Inclusion of Gold Clusters on a CH3S Self-Assembled Lattice on Au(111

    Directory of Open Access Journals (Sweden)

    Darnel J. Allen

    2016-01-01

    Full Text Available We employ first-principles density functional theoretical calculations to address the inclusion of gold (Au clusters in a well-packed CH3S self-assembled lattice. We compute CH3S adsorption energies to quantify the energetic stability of the self-assembly and gold adsorption and dissolution energies to characterize the structural stability of a series of Au clusters adsorbed at the SAM-Au interface. Our results indicate that the inclusion of Au clusters with less than four Au atoms in the SAM-Au interface enhances the binding of CH3S species. In contrast, larger Au clusters destabilize the self-assembly. We attribute this effect to the low-coordinated gold atoms in the cluster. For small clusters, these low-coordinated sites have significantly different electronic properties compared to larger islands, which makes the binding with the self-assembly energetically more favorable. Our results further indicate that Au clusters in the SAM-Au interface are thermodynamically unstable and they will tend to dissolve, producing Au adatoms incorporated in the self-assembly in the form of CH3S-Au-SCH3 species. This is due to the strong S-Au bond which stabilizes single Au adatoms in the self-assembly. Our results provide solid insight into the impact of adatom islands at the CH3S-Au interface.

  12. Critical Contribution of Tyr15 in the HIV-1 Integrase (IN) in Facilitating IN Assembly and Nonenzymatic Function through the IN Precursor Form with Reverse Transcriptase.

    Science.gov (United States)

    Takahata, Tatsuro; Takeda, Eri; Tobiume, Minoru; Tokunaga, Kenzo; Yokoyama, Masaru; Huang, Yu-Lun; Hasegawa, Atsuhiko; Shioda, Tatsuo; Sato, Hironori; Kannagi, Mari; Masuda, Takao

    2017-01-01

    Nonenzymatic roles for HIV-1 integrase (IN) at steps prior to the enzymatic integration step have been reported. To obtain structural and functional insights into the nonenzymatic roles of IN, we performed genetic analyses of HIV-1 IN, focusing on a highly conserved Tyr15 in the N-terminal domain (NTD), which has previously been shown to regulate an equilibrium state between two NTD dimer conformations. Replacement of Tyr15 with alanine, histidine, or tryptophan prevented HIV-1 infection and caused severe impairment of reverse transcription without apparent defects in reverse transcriptase (RT) or in capsid disassembly kinetics after entry into cells. Cross-link analyses of recombinant IN proteins demonstrated that lethal mutations of Tyr15 severely impaired IN structure for assembly. Notably, replacement of Tyr15 with phenylalanine was tolerated for all IN functions, demonstrating that a benzene ring of the aromatic side chain is a key moiety for IN assembly and functions. Additional mutagenic analyses based on previously proposed tetramer models for IN assembly suggested a key role of Tyr15 in facilitating the hydrophobic interaction among IN subunits, together with other proximal residues within the subunit interface. A rescue experiment with a mutated HIV-1 with RT and IN deleted (ΔRT ΔIN) and IN and RT supplied in trans revealed that the nonenzymatic IN function might be exerted through the IN precursor conjugated with RT (RT-IN). Importantly, the lethal mutations of Tyr15 significantly reduced the RT-IN function and assembly. Taken together, Tyr15 seems to play a key role in facilitating the proper assembly of IN and RT on viral RNA through the RT-IN precursor form. Inhibitors of the IN enzymatic strand transfer function (INSTI) have been applied in combination antiretroviral therapies to treat HIV-1-infected patients. Recently, allosteric IN inhibitors (ALLINIs) that interact with HIV-1 IN residues, the locations of which are distinct from the catalytic

  13. Preparation and Grafting Functionalization of Self-Assembled Chitin Nanofiber Film

    Directory of Open Access Journals (Sweden)

    Jun-ichi Kadokawa

    2016-07-01

    Full Text Available Chitin is a representative biomass resource comparable to cellulose. Although considerable efforts have been devoted to extend novel applications to chitin, lack of solubility in water and common organic solvents causes difficulties in improving its processability and functionality. Ionic liquids have paid much attention as solvents for polysaccharides. However, little has been reported regarding the dissolution of chitin with ionic liquids. The author found that an ionic liquid, 1-allyl-3-methylimidazolium bromide (AMIMBr, dissolved chitin in concentrations up to ~4.8 wt % and the higher contents of chitin with AMIMBr gave ion gels. When the ion gel was soaked in methanol for the regeneration of chitin, followed by sonication, a chitin nanofiber dispersion was obtained. Filtration of the dispersion was subsequently carried out to give a chitin nanofiber film. A chitin nanofiber/poly(vinyl alcohol composite film was also obtained by co-regeneration approach. Chitin nanofiber-graft-synthetic polymer composite films were successfully prepared by surface-initiated graft polymerization technique. For example, the preparation of chitin nanofiber-graft-biodegradable polyester composite film was achieved by surface-initiated graft polymerization from the chitin nanofiber film. The similar procedure also gave chitin nanofiber-graft-polypeptide composite film. The surface-initiated graft atom transfer radical polymerization was conducted from a chitin macroinitiator film derived from the chitin nanofiber film.

  14. An evaluation of the T-6A Texan (JPATS) functional performance of the CFIS laser assemblies

    Science.gov (United States)

    Blachowski, Thomas J.; Eccard, George

    2008-08-01

    The Indian Head Division, Naval Surface Warfare Center (IHDIV, NSWC) CAD Engineering Division is conducting a program to evaluate the laser components which comprise the Canopy Fracturing Initiation System (CFIS) currently installed on the T-6A Texan or JPATS (Joint Primary Aircraft Training System) aircraft. The T-6A Texan is the first aircraft used by the military to train future pilots. The CFIS is an element of the pilot emergency escape system which weakens the canopy in the path of the ejection seat. The CFIS is comprised of three differing configurations (Internal, External, and Seat Motion) which generate a laser pulse that is distributed through a fiber optic energy transmission system. This pulse, in turn, initiates explosive components which weaken the respective canopies. All of the CFIS laser types are flashlamp-pumped, neodymium glass lasers which are located at various positions in the aircraft cockpit area. This paper presents the CAD Engineering Division effort to evaluate the functional performance of the three CCFIS laser signal generators after their being in fleet use for a period of time.

  15. Assembly of robust bacterial microcompartment shells using building blocks from an organelle of unknown function.

    Science.gov (United States)

    Lassila, Jonathan K; Bernstein, Susan L; Kinney, James N; Axen, Seth D; Kerfeld, Cheryl A

    2014-05-29

    Bacterial microcompartments (BMCs) sequester enzymes from the cytoplasmic environment by encapsulation inside a selectively permeable protein shell. Bioinformatic analyses indicate that many bacteria encode BMC clusters of unknown function and with diverse combinations of shell proteins. The genome of the halophilic myxobacterium Haliangium ochraceum encodes one of the most atypical sets of shell proteins in terms of composition and primary structure. We found that microcompartment shells could be purified in high yield when all seven H. ochraceum BMC shell genes were expressed from a synthetic operon in Escherichia coli. These shells differ substantially from previously isolated shell systems in that they are considerably smaller and more homogeneous, with measured diameters of 39±2nm. The size and nearly uniform geometry allowed the development of a structural model for the shells composed of 260 hexagonal units and 13 hexagons per icosahedral face. We found that new proteins could be recruited to the shells by fusion to a predicted targeting peptide sequence, setting the stage for the use of these remarkably homogeneous shells for applications such as three-dimensional scaffolding and the construction of synthetic BMCs. Our results demonstrate the value of selecting from the diversity of BMC shell building blocks found in genomic sequence data for the construction of novel compartments. Copyright © 2014 Elsevier Ltd. All rights reserved.

  16. Assembly of Robust Bacterial Microcompartment Shells Using Building Blocks from an Organelle of Unknown Function

    Energy Technology Data Exchange (ETDEWEB)

    Lassila, JK; Bernstein, SL; Kinney, JN; Axen, SD; Kerfeld, CA

    2014-05-29

    Bacterial microconnpartnnents (BMCs) sequester enzymes from the cytoplasmic environment by encapsulation inside a selectively permeable protein shell. Bioinformatic analyses indicate that many bacteria encode BMC clusters of unknown function and with diverse combinations of shell proteins. The genome of the halophilic myxobacterium Haliangium ochraceum encodes one of the most atypical sets of shell proteins in terms of composition and primary structure. We found that microconnpartnnent shells could be purified in high yield when all seven H. ochraceum BMC shell genes were expressed from a synthetic operon in Escherichia coll. These shells differ substantially from previously isolated shell systems in that they are considerably smaller and more homogeneous, with measured diameters of 39 2 nm. The size and nearly uniform geometry allowed the development of a structural model for the shells composed of 260 hexagonal units and 13 hexagons per icosahedral face. We found that new proteins could be recruited to the shells by fusion to a predicted targeting peptide sequence, setting the stage for the use of these remarkably homogeneous shells for applications such as three-dimensional scaffolding and the construction of synthetic BMCs. Our results demonstrate the value of selecting from the diversity of BMC shell building blocks found in genomic sequence data for the construction of novel compartments. (C) 2014 Elsevier Ltd. All rights reserved.

  17. Multilayer graphene rubber nanocomposites

    Science.gov (United States)

    Schartel, Bernhard; Frasca, Daniele; Schulze, Dietmar; Wachtendorf, Volker; Krafft, Bernd; Morys, Michael; Böhning, Martin; Rybak, Thomas

    2016-05-01

    Multilayer Graphene (MLG), a nanoparticle with a specific surface of BET = 250 m2/g and thus made of only approximately 10 graphene sheets, is proposed as a nanofiller for rubbers. When homogenously dispersed, it works at low loadings enabling the replacement of carbon black (CB), increase in efficiency, or reduction in filler concentration. Actually the appropriate preparation yielded nanocomposites in which just 3 phr are sufficient to significantly improve the rheological, curing and mechanical properties of different rubbers, as shown for Chlorine-Isobutylene-Isoprene Rubber (CIIR), Nitrile-Butadiene Rubber (NBR), Natural Rubber (NR), and Styrene-Butadiene Rubber (SBR). A mere 3 phr of MLG tripled the Young's modulus of CIIR, an effect equivalent to 20 phr of carbon black. Similar equivalents are observed for MLG/CB mixtures. MLG reduces gas permeability, increases thermal and electrical conductivities, and retards fire behavior. The later shown by the reduction in heat release rate in the cone calorimeter. The higher the nanofiller concentration is (3 phr, 5 phr, and 10 phr was investigated), the greater the improvement in the properties of the nanocomposites. Moreover, the MLG nanocomposites improve stability of mechanical properties against weathering. An increase in UV-absorption as well as a pronounced radical scavenging are proposed and were proved experimentally. To sum up, MLG is interesting as a multifunctional nanofiller and seems to be quite ready for rubber development.

  18. Multilayer optical calculations

    CERN Document Server

    Byrnes, Steven J

    2016-01-01

    When light hits a multilayer planar stack, it is reflected, refracted, and absorbed in a way that can be derived from the Fresnel equations. The analysis is treated in many textbooks, and implemented in many software programs, but certain aspects of it are difficult to find explicitly and consistently worked out in the literature. Here, we derive the formulas underlying the transfer-matrix method of calculating the optical properties of these stacks, including oblique-angle incidence, absorption-vs-position profiles, and ellipsometry parameters. We discuss and explain some strange consequences of the formulas in the situation where the incident and/or final (semi-infinite) medium are absorptive, such as calculating $T>1$ in the absence of gain. We also discuss some implementation details like complex-plane branch cuts. Finally, we derive modified formulas for including one or more "incoherent" layers, i.e. very thick layers in which interference can be neglected. This document was written in conjunction with ...

  19. pH-controlled construction of chitosan/alginate multilayer film: characterization and application for antibody immobilization.

    Science.gov (United States)

    Yuan, Weiyong; Dong, Hua; Li, Chang Ming; Cui, Xiaoqiang; Yu, Ling; Lu, Zhisong; Zhou, Qin

    2007-12-18

    In this work, a chitosan/alginate multilayer film was constructed via layer-by-layer self-assembly and studied by in situ surface plasmon resonance monitoring and contact angle measurements. The results demonstrate that the surface composition of the self-assembled multilayer film can be simply tailored through pH control during the assembly process. The biological property of the assembled film was further characterized via antigen-antibody interactions, showing that the loading capacity of the antibody on the multilayered film and the binding activity of the antigen to the immobilized antibody could be also well-tuned by pH control. This work can provide more scientific insight in the interaction between protein and polymer matrix and render a novel simple approach to build high-performance biointerfaces through pH control for potential applications of highly sensitive immunosensors.

  20. Investigation of the structural anisotropy in a self-assembling glycinate layer on Cu(100) by scanning tunneling microscopy and density functional theory calculations

    Energy Technology Data Exchange (ETDEWEB)

    Kuzmin, Mikhail [Surface Science Laboratory, Optoelectronics Research Centre, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere (Finland); Ioffe Physical Technical Institute, Russian Academy of Sciences, 26 Polytekhnicheskaya, St Petersburg 194021 (Russian Federation); Lahtonen, Kimmo; Vuori, Leena [Surface Science Laboratory, Optoelectronics Research Centre, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere (Finland); Sánchez-de-Armas, Rocío [Materials Theory Division, Department of Physics and Astronomy, Uppsala University, P.O. Box 516, S75120 Uppsala (Sweden); Hirsimäki, Mika, E-mail: mikahirsi@gmail.com [Surface Science Laboratory, Optoelectronics Research Centre, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere (Finland); Valden, Mika [Surface Science Laboratory, Optoelectronics Research Centre, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere (Finland)

    2017-07-01

    Highlights: • Deprotonation reaction of glycine and self-assembly of glycinate is observed on Cu. • Bias-dependent scanning tunneling microscopy indicates two glycinate geometries. • Density functional theory calculations confirm the two non-identical configurations. • Non-identical adsorption explains the anisotropy in adlayer’s electronic structure. - Abstract: Self-assembling organic molecule-metal interfaces exhibiting free-electron like (FEL) states offers an attractive bottom-up approach to fabricating materials for molecular electronics. Accomplishing this, however, requires detailed understanding of the fundamental driving mechanisms behind the self-assembly process. For instance, it is still unresolved as to why the adsorption of glycine ([NH{sub 2}(CH{sub 2})COOH]) on isotropic Cu(100) single crystal surface leads, via deprotonation and self-assembly, to a glycinate ([NH{sub 2}(CH{sub 2})COO–]) layer that exhibits anisotropic FEL behavior. Here, we report on bias-dependent scanning tunneling microscopy (STM) experiments and density functional theory (DFT) calculations for glycine adsorption on Cu(100) single crystal surface. We find that after physical vapor deposition (PVD) of glycine on Cu(100), glycinate self-assembles into an overlayer exhibiting c(2 × 4) and p(2 × 4) symmetries with non-identical adsorption sites. Our findings underscore the intricacy of electrical conductivity in nanomolecular organic overlayers and the critical role the structural anisotropy at molecule-metal interface plays in the fabrication of materials for molecular electronics.

  1. Evaluation of early and late effects into the acute spinal cord injury of an injectable functionalized self-assembling scaffold.

    Directory of Open Access Journals (Sweden)

    Daniela Cigognini

    Full Text Available The complex physiopathological events occurring after spinal cord injury (SCI make this devastating trauma still incurable. Self-assembling peptides (SAPs are nanomaterials displaying some appealing properties for application in regenerative medicine because they mimic the structure of the extra-cellular matrix (ECM, are reabsorbable, allow biofunctionalizations and can be injected directly into the lesion. In this study we evaluated the putative neurorigenerative properties of RADA16-4G-BMHP1 SAP, proved to enhance in vitro neural stem cells survival and differentiation. This SAP (RADA16-I has been functionalized with a bone marrow homing motif (BMHP1 and optimized via the insertion of a 4-glycine-spacer that ameliorates scaffold stability and exposure of the biomotifs. We injected the scaffold immediately after contusion in the rat spinal cord, then we evaluated the early effects by semi-quantitative RT-PCR and the late effects by histological analysis. Locomotor recovery over 8 weeks was assessed using Basso, Beattie, Bresnahan (BBB test. Gene expression analysis showed that at 7 days after lesion the functionalized SAP induced a general upregulation of GAP-43, trophic factors and ECM remodelling proteins, whereas 3 days after SCI no remarkable changes were observed. Hystological analysis revealed that 8 weeks after SCI our scaffold increased cellular infiltration, basement membrane deposition and axon regeneration/sprouting within the cyst. Moreover the functionalized SAP showed to be compatible with the surrounding nervous tissue and to at least partially fill the cavities. Finally SAP injection resulted in a statistically significant improvement of both hindlimbs' motor performance and forelimbs-hindlimbs coordination. Altogether, these results indicate that RADA16-4G-BMHP1 induced favourable reparative processes, such as matrix remodelling, and provided a physical and trophic support to nervous tissue ingrowth. Thus this biomaterial

  2. Ionic self-assembly of surface functionalized metal-organic polyhedra nanocages and their ordered honeycomb architecture at the air/water interface.

    Science.gov (United States)

    Li, Yantao; Zhang, Daojun; Gai, Fangyuan; Zhu, Xingqi; Guo, Ya-nan; Ma, Tianliang; Liu, Yunling; Huo, Qisheng

    2012-08-18

    Metal-organic polyhedra (MOP) nanocages were successfully surface functionalized via ionic self-assembly and the ordered honeycomb architecture of the encapsulated MOP nanocages was also fabricated at the air/water surface. The results provide a novel synthetic method and membrane processing technique of amphiphilic MOP nanocages for various applications.

  3. A functional mobA gene for molybdopterin cytosine dinucleotide cofactor biosynthesis is required for activity and holoenzyme assembly of the heterotrimeric nicotine dehydrogenases of Arthrobacter nicotinovorans.

    Science.gov (United States)

    Sachelaru, Paula; Schiltz, Emile; Brandsch, Roderich

    2006-07-01

    Two Arthrobacter nicotinovorans molybdenum enzymes hydroxylate the pyridine ring of nicotine. Molybdopterin cytosine dinucleotide (MCD) was determined to be a cofactor of these enzymes. A mobA gene responsible for the formation of MCD could be identified and its function shown to be required for assembly of the heterotrimeric molybdenum enzymes.

  4. Microstructure and Phase Behavior of a Quinquethiophene-Based Self-Assembled Monolayer as a Function of Temperature

    NARCIS (Netherlands)

    Flesch, Heinz-Georg; Mathijssen, Simon G. J.; Gholamrezaie, Fatemeh; Moser, Armin; Neuhold, Alfred; Novak, Jiri; Ponomarenko, Sergei A.; Shen, Quan; Teichert, Christian; Hlawacek, Gregor; Puschnig, Peter; Ambrosch-Draxl, Claudia; Resel, Roland; de Leeuw, Dago M.

    2011-01-01

    The self-assembly of monolayers is a highly promising approach in organic electronics, but most systems show weak device performances, probably because of a lack of long-range order of the molecules. The present self-assembled monolayer was formed by a molecule that contains a dimethyl-chlorosilyl

  5. Self-assembly and photopolymerization of a novel quaternary-ammonium functionalized diacetylene on noble metal nanoparticles: A comparative study

    Science.gov (United States)

    Martinez-Espinoza, Maria Isabel; Maccagno, Massimo; Thea, Sergio; Alloisio, Marina

    2018-01-01

    Stable hydrosols of gold and silver nanoparticles coated with the quaternary-ammonium group endowed diacetylene DAAMM (N,N,N-trimethyl-3-(pentacosa-10,12-diynamido)propan-1-ammonium) were obtained through a ligand-exchange reaction leaving the morphology of the pristine cores unmodified. Photopolymerization of the chemisorbed diacetylene shell occurred in both red and blue phases thanks to the presence of internal, H-bondable amide functions in the monomer chain, which are supposed to help the formation of a packed bilayer on the metal surfaces. Multidisciplinary characterization of the polymerized samples, including spectroscopic, morphological and thermal techniques, highlighted that differences occur in the polymerization process on gold and silver nanoparticles under different experimental conditions, suggesting a higher affinity of the trimethylammonium headgroup for gold substrates in acidic media. With respect to the extensively investigated PCDA (pentacosa-10,12-diynoic acid), DAAMM showed reduced capability of photogenerating thick polymer shells, especially in the more delocalized blue form, probably because of the inefficiency of the cationic monomer to form the multi-bilayered architecture typical of the highly-performing, carboxyl-terminated diacetylene. On the other end, the inner cross-linked structure gives to poly(DAAMM)-coated nanohybrids increased stability in water with respect to self-assembled counterparts deriving from saturated cationic surfactants, making them a promising sensing platform for rapid and cost effective assays of real samples.

  6. Zwint-1 is required for spindle assembly checkpoint function and kinetochore-microtubule attachment during oocyte meiosis.

    Science.gov (United States)

    Woo Seo, Dong; Yeop You, Seung; Chung, Woo-Jae; Cho, Dong-Hyung; Kim, Jae-Sung; Su Oh, Jeong

    2015-10-21

    The key step for faithful chromosome segregation during meiosis is kinetochore assembly. Defects in this process result in aneuploidy, leading to miscarriages, infertility and various birth defects. However, the roles of kinetochores in homologous chromosome segregation during meiosis are ill-defined. Here we found that Zwint-1 is required for homologous chromosome segregation during meiosis. Knockdown of Zwint-1 accelerated the first meiosis by abrogating the kinetochore recruitment of Mad2, leading to chromosome misalignment and a high incidence of aneuploidy. Although Zwint-1 knockdown did not affect Aurora C kinase activity, the meiotic defects following Zwint-1 knockdown were similar to those observed with ZM447439 treatment. Importantly, the chromosome misalignment following Aurora C kinase inhibition was not restored after removing the inhibitor in Zwint-1-knockdown oocytes, whereas the defect was rescued after the inhibitor washout in the control oocytes. These results suggest that Aurora C kinase-mediated correction of erroneous kinetochore-microtubule attachment is primarily regulated by Zwint-1. Our results provide the first evidence that Zwint-1 is required to correct erroneous kinetochore-microtubule attachment and regulate spindle checkpoint function during meiosis.

  7. Chemical bath deposition of ZnO on functionalized self-assembled monolayers: selective deposition and control of deposit morphology.

    Science.gov (United States)

    Shi, Zhiwei; Walker, Amy V

    2015-02-03

    We have developed a method by which to selectively and reproducibly deposit ZnO films on functionalized self-assembled monolayers (SAMs) using chemical bath deposition (CBD). The deposition bath is composed of zinc acetate and ethylenediamine. The deposition reaction pathways are shown to be similar to those observed for sulfides and selenides, even though ethylenediamine acts as both an oxygen source and a complexing agent. On -COOH terminated SAMs, Zn-carboxylate surface complexes act as nucleation sites for ion-by-ion growth, leading to the formation of adherent ZnO nanocrystallites. Cluster-by-cluster growth is also observed, which produces weakly adherent micrometer-sized ZnO crystallites. On -CH3 and -OH terminated SAMs, only micrometer-sized ZnO crystallites are observed because Zn(2+) does not complex with the SAM terminal group, preventing nucleation of the nanocrystalline phase. The application of either ultrasound ("sonication-assisted CBD") or stirring promotes ion-by-ion ZnO growth on -COOH terminated SAMs. Stirring produces smoother but less reproducible ZnO films than sonication-assisted CBD.

  8. Sectioning of multilayers to make a multilayer Laue lens

    Science.gov (United States)

    Kang, Hyon Chol; Stephenson, G. Brian; Liu, Chian; Conley, Ray; Khachatryan, Ruben; Wieczorek, Michael; Macrander, Albert T.; Yan, Hanfei; Maser, Jörg; Hiller, Jon; Koritala, Rachel

    2007-04-01

    We report a process to fabricate multilayer Laue lenses (MLL's) by sectioning and thinning multilayer films. This method can produce a linear zone plate structure with a very large ratio of zone depth to width (e.g., >1000), orders of magnitude larger than can be attained with photolithography. Consequently, MLL's are advantageous for efficient nanofocusing of hard x rays. MLL structures prepared by the technique reported here have been tested at an x-ray energy of 19.5keV, and a diffraction-limited performance was observed. The present article reports the fabrication techniques that were used to make the MLL's.

  9. Structural and magnetic properties of granular CoPd multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Vivas, L.G.; Figueroa, A.I.; Bartolomé, F. [Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Dept. de Física de la Materia Condensada, E-50009 Zaragoza (Spain); Rubín, J. [Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Dept. de Ciencia y Tecnología de Materiales y Fluidos, E-50018 Zaragoza (Spain); García, L.M. [Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Dept. de Física de la Materia Condensada, E-50009 Zaragoza (Spain); Deranlot, C.; Petroff, F. [Unité Mixte de Physique CNRS/Thales, F-91767 Palaiseau Cedex, France and Université Paris-Sud, F-191405 Orsay Cedex (France); Ruiz, L.; González-Calbet, J.M [Dept. de Química Inorgánica, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Brookes, N.B.; Wilhelm, F.; Rogalev, A. [European Synchrotron Radiation Facility (ESRF), CS40220, F-38043 Grenoble Cedex 9 (France); Bartolomé, J. [Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Dept. de Física de la Materia Condensada, E-50009 Zaragoza (Spain)

    2016-02-15

    Multilayers of bimetallic CoPd alloyed and assembled nanoparticles, prepared by room temperature sequential sputtering deposition on amorphous alumina, were studied by means of high-resolution transmission electron microscopy, x-ray diffraction, SQUID-based magnetometry and x-ray magnetic circular dichroism. Alloying between Co and Pd in these nanoparticles gives rise to a high perpendicular magnetic anisotropy. Their magnetic properties are temperature dependent: at low temperature, the multilayers are ferromagnetic with a high coercive field; at intermediate temperature the behavior is of a soft-ferromagnet, and at higher temperature, the perpendicular magnetic anisotropy in the nanoparticles disappears. The magnetic orbital moment to spin moment ratio is enhanced compared with Co bare nanoparticles and Co fcc bulk. - Highlights: • CoPd granular nanolayers show perpendicular magnetic anisotropy. • Three magnetic phases are detected: hard-ferro, soft-ferro and superparamagnetism. • The nanoparticles have Co-core and CoPd alloy shell morphology.

  10. Localization and function of Kinesin-5-like proteins during assembly and maintenance of mitotic spindles in Silvetia compressa

    Directory of Open Access Journals (Sweden)

    Miller Anne

    2009-06-01

    Full Text Available Abstract Background Kinesin-5 (Eg-5 motor proteins are essential for maintenance of spindle bipolarity in animals. The roles of Kinesin-5 proteins in other systems, such as Arabidopsis, Dictyostelium, and sea urchin are more varied. We are studying Kinesin-5-like proteins during early development in the brown alga Silvetia compressa. Previously, this motor was shown to be needed to assemble a bipolar spindle, similar to animals. This report builds on those findings by investigating the localization of the motor and probing its function in spindle maintenance. Findings Anti-Eg5 antibodies were used to investigate localization of Kinesin-5-like proteins in brown algal zygotes. In interphase zygotes, localization was predominantly within the nucleus. As zygotes entered mitosis, these motor proteins strongly associated with spindle poles and, to a lesser degree, with the polar microtubule arrays and the spindle midzone. In order to address whether Kinesin-5-like proteins are required to maintain spindle bipolarity, we applied monastrol to synchronized zygotes containing bipolar spindles. Monastrol is a cell-permeable chemical inhibitor of the Kinesin-5 class of molecular motors. We found that inhibition of motor function in pre-formed spindles induced the formation of multipolar spindles and short bipolar spindles. Conclusion Based upon these localization and inhibitor studies, we conclude that Kinesin-5-like motors in brown algae are more similar to the motors of animals than those of plants or protists. However, Kinesin-5-like proteins in S. compressa serve novel roles in spindle formation and maintenance not observed in animals.

  11. Insight into the assembly properties and functional organisation of the magnetotactic bacterial actin-like homolog, MamK.

    Directory of Open Access Journals (Sweden)

    Sanjiv Sonkaria

    Full Text Available Magnetotactic bacteria (MTB synthesize magnetosomes, which are intracellular vesicles comprising a magnetic particle. A series of magnetosomes arrange themselves in chains to form a magnetic dipole that enables the cell to orient itself along the Earth's magnetic field. MamK, an actin-like homolog of MreB has been identified as a central component in this organisation. Gene deletion, fluorescence microscopy and in vitro studies have yielded mechanistic differences in the filament assembly of MamK with other bacterial cytoskeletal proteins within the cell. With little or no information on the structural and behavioural characteristics of MamK outside the cell, the mamK gene from Magnetospirillium gryphiswaldense was cloned and expressed to better understand the differences in the cytoskeletal properties with its bacterial homologues MreB and acitin. Despite the low sequence identity shared between MamK and MreB (22% and actin (18%, the behaviour of MamK monitored by light scattering broadly mirrored that of its bacterial cousin MreB primarily in terms of its pH, salt, divalent metal-ion and temperature dependency. The broad size variability of MamK filaments revealed by light scattering studies was supported by transmission electron microscopy (TEM imaging. Filament morphology however, indicated that MamK conformed to linearly orientated filaments that appeared to be distinctly dissimilar compared to MreB suggesting functional differences between these homologues. The presence of a nucleotide binding domain common to actin-like proteins was demonstrated by its ability to function both as an ATPase and GTPase. Circular dichroism and structural homology modelling showed that MamK adopts a protein fold that is consistent with the 'classical' actin family architecture but with notable structural differences within the smaller domains, the active site region and the overall surface electrostatic potential.

  12. The COSMOS2015 galaxy stellar mass function . Thirteen billion years of stellar mass assembly in ten snapshots

    Science.gov (United States)

    Davidzon, I.; Ilbert, O.; Laigle, C.; Coupon, J.; McCracken, H. J.; Delvecchio, I.; Masters, D.; Capak, P.; Hsieh, B. C.; Le Fèvre, O.; Tresse, L.; Bethermin, M.; Chang, Y.-Y.; Faisst, A. L.; Le Floc'h, E.; Steinhardt, C.; Toft, S.; Aussel, H.; Dubois, C.; Hasinger, G.; Salvato, M.; Sanders, D. B.; Scoville, N.; Silverman, J. D.

    2017-09-01

    We measure the stellar mass function (SMF) and stellar mass density of galaxies in the COSMOS field up to z 6. We select them in the near-IR bands of the COSMOS2015 catalogue, which includes ultra-deep photometry from UltraVISTA-DR2, SPLASH, and Subaru/Hyper Suprime-Cam. At z> 2.5 we use new precise photometric redshifts with error σz = 0.03(1 + z) and an outlier fraction of 12%, estimated by means of the unique spectroscopic sample of COSMOS ( 100 000 spectroscopic measurements in total, more than one thousand having robust zspec> 2.5). The increased exposure time in the DR2, along with our panchromatic detection strategy, allow us to improve the completeness at high z with respect to previous UltraVISTA catalogues (e.g. our sample is >75% complete at 1010 ℳ⊙ and z = 5). We also identify passive galaxies through a robust colour-colour selection, extending their SMF estimate up to z = 4. Our work provides a comprehensive view of galaxy-stellar-mass assembly between z = 0.1 and 6, for the first time using consistent estimates across the entire redshift range. We fit these measurements with a Schechter function, correcting for Eddington bias. We compare the SMF fit with the halo mass function predicted from ΛCDM simulations, finding that at z> 3 both functions decline with a similar slope in thehigh-mass end. This feature could be explained assuming that mechanisms quenching star formation in massive haloes become less effective at high redshifts; however further work needs to be done to confirm this scenario. Concerning the SMF low-mass end, it shows a progressive steepening as it moves towards higher redshifts, with α decreasing from -1.47+0.02-0.02 at z ≃ 0.1 to -2.11+0.30-0.13-2.11-0.13+0.30 at z ≃ 5. This slope depends on the characterisation of the observational uncertainties, which is crucial to properly remove the Eddington bias. We show that there is currently no consensus on the method to quantify such errors: different error models result in

  13. Multilayer adsorption on fractal surfaces.

    Science.gov (United States)

    Vajda, Péter; Felinger, Attila

    2014-01-10

    Multilayer adsorption is often observed in liquid chromatography. The most frequently employed model for multilayer adsorption is the BET isotherm equation. In this study we introduce an interpretation of multilayer adsorption measured on liquid chromatographic stationary phases based on the fractal theory. The fractal BET isotherm model was successfully used to determine the apparent fractal dimension of the adsorbent surface. The nonlinear fitting of the fractal BET equation gives us the estimation of the adsorption equilibrium constants and the monolayer saturation capacity of the adsorbent as well. In our experiments, aniline and proline were used as test molecules on reversed phase and normal phase columns, respectively. Our results suggest an apparent fractal dimension 2.88-2.99 in the case of reversed phase adsorbents, in the contrast with a bare silica column with a fractal dimension of 2.54. Copyright © 2013 The Authors. Published by Elsevier B.V. All rights reserved.

  14. De novo sequencing and assembly of Centella asiatica leaf transcriptome for mapping of structural, functional and regulatory genes with special reference to secondary metabolism.

    Science.gov (United States)

    Sangwan, Rajender S; Tripathi, Sandhya; Singh, Jyoti; Narnoliya, Lokesh K; Sangwan, Neelam S

    2013-08-01

    Centella asiatica (L.) Urban is an important medicinal plant and has been used since ancient times in traditional systems of medicine. C. asiatica mainly contains ursane skeleton based triterpenoid sapogenins and saponins predominantly in its leaves. This investigation employed Illumina next generation sequencing (NGS) strategy on a pool of three cDNAs from expanding leaf of C. asiatica and developed an assembled transcriptome sequence resource of the plant. The short transcript reads (STRs) generated and assembled into contigs and singletons, representing majority of the genes expressed in C. asiatica, were termed as 'tentative unique transcripts' (TUTs). The TUT dataset was analyzed with the objectives of (i) development of a transcriptome assembly of C. asiatica, and (ii) classification/characterization of the genes into categories like structural, functional, regulatory etc. based on their function. Overall, 68.49% of the 46,171,131 reads generated in the NGS process could be assembled into a total of 79,041 contigs. Gene ontology and functional annotation of sequences resulted into the identification of genes related to different sets of cellular functions including identification of genes related to primary and secondary metabolism. The wet lab validation of seventeen assembled gene sequences identified to be involved in secondary metabolic pathways and control of reactive oxygen species (ROS) was established by semi-quantitative and real time PCR (qRT-PCR). The validation also included sequencing/size matching of a set of semi-quantitative PCR amplicons with their in silico assembled contig/gene. This confirmed the appropriateness of assembling the reads and contigs. Thus, the present study constitutes the largest report to date on C. asiatica transcriptome based gene resource that may contribute substantially to the understanding of the basal biological functions and biochemical pathways of secondary metabolites as well as the transcriptional regulatory

  15. X-ray grazing incidence diffraction from multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Tixier, S.; Boeni, P.; Swygenhoven, H. van; Horisberger, M. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-09-01

    Grazing incidence scattering geometries using synchrotron radiation have been applied in order to characterise the roughness profiles and the structural coherence of multilayers. The lateral correlation length of the roughness profiles was evaluated using diffuse reflectivity in the `out of plane` geometry. This type of measurement is the only diffuse reflectivity technique allowing large lateral momentum transfer. It is typically suitable for correlation lengths smaller than 1000 A. The lateral structural coherence length of Ni{sub 3}Al/Ni multilayers as a function of the layer thickness was obtained by grazing incidence diffraction (GID). 3 figs., 1 ref.

  16. Electron-electron Interactions in ABC-stacked Multilayer Graphene

    Science.gov (United States)

    Zhang, Fan; MacDonald, Allan

    2010-03-01

    The electronic band structures of ABC-stacked multilayer graphene systems are obtained by the tight-binding calculation and the density function theory. We predict that the electron- electron interactions drive the neutral graphene multilayer systems to pseudospin magnets in which the charge density contribution spontaneously shifts to either the top or the bottom layers, based on the HF and PRG calculations. We show that the spin and valley degrees of freedom enhance the instabilities. We investigate the influence on the broken symmetry phase by the trigonal warping, the external electric field and the number of coupled graphene layers.

  17. Influence of surface topography on the multilayer film formation

    Energy Technology Data Exchange (ETDEWEB)

    Grishchenko, Yu. V., E-mail: grishchenko@ns.crys.ras.ru [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Zanaveskin, M. L. [Russian Research Centre Kurchatov Institute (Russian Federation); Tolstikhina, A. L. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

    2010-01-15

    The relationship between the topography of substrates and multilayer films deposited on these substrates (which are used in ring laser gyroscopes) has been investigated. The surfaces were studied by atomic-force microscopy. The statistical properties of the surface topography are analyzed within the approach based on a comparative analysis of the power spectral density functions of roughness calculated for the substrate and film. The degree of correlation between the substrate nanotopography and multilayer film is determined, and the influence of the substrate roughness on the optical characteristics of the deposited mirrors is established.

  18. Surface grafted chitosan gels. Part I. Molecular insight into the formation of chitosan and poly(acrylic acid) multilayers

    DEFF Research Database (Denmark)

    Liu, Chao; Thormann, Esben; Claesson, Per M.

    2014-01-01

    and decomposition. The assembly process is characterized by nonlinear growth behavior, with different adsorption kinetics for chitosan and PAA. In situ analysis of the multilayer by means of surface sensitive total internal reflection Raman (TIRR) spectroscopy, combined with target factor analysis of the spectra...... components (PAA) and the island-like morphology contribute to the nonlinear growth of chitosan/PAA multilayers. © 2014 American Chemical Society....

  19. Adaptation, acclimation, and assembly: How optimality principles govern the scaling of form, function, and diversity of ecosystem function in the light of climate change.

    Science.gov (United States)

    Enquist, B. J.

    2016-12-01

    The link between variation in species-specific traits - due to acclimation, adaptation, and how ecological communities assemble in time and space - and larger scale ecosystem processes is an important focus for global change research. Understanding such linkages requires synthesis of evolutionary, biogeograpahic, and biogeochemical approaches. Recent observations reveal several paradoxical patterns across ecosystems. Optimality principles provide a novel framework for generating numerous predictions for how ecosystems have and will reorganize and respond to climate change. Tropical elevation gradients are natural laboratories to assess how changing climate can ramify to influence tropical forest diversity and ecosystem functioning. We tested several new predictions from trait- and metabolic scaling theories by assessing the covariation between climate, traits, biomass and gross and net primary productivity (GPP and NPP) across tropical forest plots spanning elevation gradients. We measured multiple leaf physiological, morphological, and stoichiometric traits linked to variation in tree growth. Consistent with theory, observed decreases in NPP and GPP with temperature were best predicted by forest biomass, and scaled allometrically as predicted by theory but the effect of temperature was much less, characterized by a kinetic response much lower ( 0.1eV) than predicted ( 0.65eV). This is likely due to an observed exponential increase in the mean community leaf P:N ratio and photosynthetic nutrient use efficiency with decreases in temperature. Our results are consistent with predictions from Trait Driver Theory, where adaptive/acclamatory shifts in plant traits compensate for the kinetic effects of temperature on tree growth. Further, most of the traits measured showed significantly skewed trait distributions consistent with recent observations that observed shifts in species composition. The development of trait-based scaling theory provides a robust basis to predict

  20. Optical transmittance of multilayer graphene

    Science.gov (United States)

    Zhu, Shou-En; Yuan, Shengjun; Janssen, G. C. A. M.

    2014-10-01

    We study the optical transmittance of multilayer graphene films up to 65 layers thick. By combing large-scale tight-binding simulation and optical measurement on CVD multilayer graphene, the optical transmission through graphene films in the visible region is found to be solely determined by the number of graphene layers. We argue that the optical transmittance measurement is more reliable in the determination of the number of layers than the commonly used the Raman spectroscopy. Moreover, the optical transmittance measurement can be applied also to other 2D materials with weak van der Waals interlayer interaction.

  1. Thermally induced delamination of multilayers

    DEFF Research Database (Denmark)

    Sørensen, Bent F.; Sarraute, S.; Jørgensen, O.

    1998-01-01

    Steady-state delamination of multilayered structures, caused by stresses arising during processing due to thermal expansion mismatch, is analyzed by a fracture mechanics model based on laminate theory. It is found that inserting just a few interlayers with intermediate thermal expansion coefficie......Steady-state delamination of multilayered structures, caused by stresses arising during processing due to thermal expansion mismatch, is analyzed by a fracture mechanics model based on laminate theory. It is found that inserting just a few interlayers with intermediate thermal expansion...

  2. A versatile strategy towards non-covalent functionalization of graphene by surface-confined supramolecular self-assembly of Janus tectons

    Directory of Open Access Journals (Sweden)

    Ping Du

    2015-03-01

    Full Text Available Two-dimensional (2D, supramolecular self-assembly at surfaces is now well-mastered with several existing examples. However, one remaining challenge to enable future applications in nanoscience is to provide potential functionalities to the physisorbed adlayer. This work reviews a recently developed strategy that addresses this key issue by taking advantage of a new concept, Janus tecton materials. This is a versatile, molecular platform based on the design of three-dimensional (3D building blocks consisting of two faces linked by a cyclophane-type pillar. One face is designed to steer 2D self-assembly onto C(sp2-carbon-based flat surfaces, the other allowing for the desired functionality above the substrate with a well-controlled lateral order. In this way, it is possible to simultaneously obtain a regular, non-covalent paving as well as supramolecular functionalization of graphene, thus opening interesting perspectives for nanoscience applications.

  3. Calmodulin is essential for cardiac IKS channel gating and assembly: impaired function in long-QT mutations

    DEFF Research Database (Denmark)

    Shamgar, Liora; Ma, Lijuan; Schmitt, Nicole

    2006-01-01

    The slow IKS K+ channel plays a major role in repolarizing the cardiac action potential and consists of the assembly of KCNQ1 and KCNE1 subunits. Mutations in either KCNQ1 or KCNE1 genes produce the long-QT syndrome, a life-threatening ventricular arrhythmia. Here, we show that long-QT mutations...... located in the KCNQ1 C terminus impair calmodulin (CaM) binding, which affects both channel gating and assembly. The mutations produce a voltage-dependent macroscopic inactivation and dramatically alter channel assembly. KCNE1 forms a ternary complex with wild-type KCNQ1 and Ca(2+)-CaM that prevents...... inactivation, facilitates channel assembly, and mediates a Ca(2+)-sensitive increase of IKS-current, with a considerable Ca(2+)-dependent left-shift of the voltage-dependence of activation. Coexpression of KCNQ1 or IKS channels with a Ca(2+)-insensitive CaM mutant markedly suppresses the currents and produces...

  4. Multilayer motif analysis of brain networks

    Science.gov (United States)

    Battiston, Federico; Nicosia, Vincenzo; Chavez, Mario; Latora, Vito

    2017-04-01

    In the last decade, network science has shed new light both on the structural (anatomical) and on the functional (correlations in the activity) connectivity among the different areas of the human brain. The analysis of brain networks has made possible to detect the central areas of a neural system and to identify its building blocks by looking at overabundant small subgraphs, known as motifs. However, network analysis of the brain has so far mainly focused on anatomical and functional networks as separate entities. The recently developed mathematical framework of multi-layer networks allows us to perform an analysis of the human brain where the structural and functional layers are considered together. In this work, we describe how to classify the subgraphs of a multiplex network, and we extend the motif analysis to networks with an arbitrary number of layers. We then extract multi-layer motifs in brain networks of healthy subjects by considering networks with two layers, anatomical and functional, respectively, obtained from diffusion and functional magnetic resonance imaging. Results indicate that subgraphs in which the presence of a physical connection between brain areas (links at the structural layer) coexists with a non-trivial positive correlation in their activities are statistically overabundant. Finally, we investigate the existence of a reinforcement mechanism between the two layers by looking at how the probability to find a link in one layer depends on the intensity of the connection in the other one. Showing that functional connectivity is non-trivially constrained by the underlying anatomical network, our work contributes to a better understanding of the interplay between the structure and function in the human brain.

  5. Binary metal oxide nanoparticle incorporated composite multilayer thin films for sono-photocatalytic degradation of organic pollutants

    Science.gov (United States)

    Gokul, Paramasivam; Vinoth, Ramalingam; Neppolian, Bernaurdshaw; Anandhakumar, Sundaramurthy

    2017-10-01

    We report reduced graphene oxide (rGO) supported binary metal oxide (CuO-TiO2/rGO) nanoparticle (NP) incorporated multilayer thin films based on Layer-by-Layer (LbL) assembly for enhanced sono-photocatalytic degradation of methyl orange under exposure to UV radiation. Multilayer thin films were fabricated on glass and quartz slides, and investigated using scanning electron microscopy and UV-vis spectroscopy. The loading of catalyst NPs on the film resulted in the change of morphology of the film from smooth to rough with uniformly distributed NPs on the surface. The growth of the control and NP incorporated films followed a linear regime as a function of number of layers. The%degradation of methyl orange as a function of time was investigated by UV-vis spectroscopy and total organic carbon (TOC) measurements. Complete degradation of methyl orange was achieved within 13 h. The amount of NP loading in the film significantly influenced the%degradation of methyl orange. Catalyst reusability studies revealed that the catalyst thin films could be repeatedly used for up to five times without any change in photocatalytic activity of the films. The findings of the present study support that the binary metal oxide catalyst films reported here are very useful for continuous systems, and thus, making it an option for scale up.

  6. Fabrication and applications of multi-layer graphene stack on transparent polymer

    Science.gov (United States)

    Krajewska, Aleksandra; Pasternak, Iwona; Sobon, Grzegorz; Sotor, Jaroslaw; Przewloka, Aleksandra; Ciuk, Tymoteusz; Sobieski, Jan; Grzonka, Justyna; Abramski, Krzysztof M.; Strupinski, Wlodek

    2017-01-01

    In this report, we demonstrate the preparation method of a multi-layer stack with a pre-defined number of graphene layers, which was obtained using chemical vapor deposition graphene deposited on a copper substrate and subsequently transferred onto a poly(methyl methacrylate) (PMMA) substrate. The prepared multi-layer stack can also be transferred onto an arbitrary substrate and in the end, the polymer can be removed, which in consequence significantly increases the range of possible graphene applications. The multi-layer character was confirmed by optical transmittance measurements and Raman spectroscopy, whereas the microstructure of the multi-layer graphene stack was investigated using Scanning Electron Microscopy. The electrical properties in the function of the number of graphene layers were assessed with standard Hall Effect measurements. Finally, we showed the practical application of the multi-layer graphene stack as a saturable absorber of a mode-locked Er-doped fiber laser.

  7. Multilayer Controller for Outdoor Vehicle

    DEFF Research Database (Denmark)

    Reske-Nielsen, Anders; Mejnertsen, Asbjørn; Andersen, Nils Axel

    2006-01-01

    A full software and hardware solution has been designed, implemented and tested for control of a small agricultural automatic tractor. The objective was to realise a user-friendly, multi-layer controller architecture for an outdoor platform. The collaborative research work was done as a part...

  8. X-ray reflectivity study on the structure and phase stability of mixed phospholipid multilayers.

    Science.gov (United States)

    Jing, H Y; Hong, D H; Kwak, B D; Choi, D J; Shin, K; Yu, C J; Kim, J W; Noh, D Y; Seo, Y S

    2009-04-07

    Vertically oriented multilayers composed of two saturated phospholipids, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphoserine (DPPS), were deposited on silicon. X-ray reflectivity was used to investigate the structures of the variously mixed phospholipid multilayers as a function of composition. Then, the phase stability was investigated at various annealing temperatures under humid conditions. The results indicated that the lipid spacing of the mixed phospholipid multilayers varied systematically as a function of the DPPC/DPPS ratio and that no macroscopic phase separation occurred during the annealing process under both dry and humid conditions.

  9. New developments in Ni/Ti multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, I.; Hoghoj, P. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)

    1997-04-01

    It is now 20 years since super-mirrors were first used as a neutron optical element. Since then the field of multilayer neutron-optics has matured with multilayers finding their way to application in many neutron scattering instruments. However, there is still room for progress in terms of multilayer quality, performance and application. Along with work on multilayers for neutron polarisation Ni/Ti super-mirrors have been optimised. The state-of-the-art Ni/Ti super-mirror performance and the results obtained in two neutron-optics applications of Ni/Ti multilayers are presented. (author).

  10. Microfluidic polymer multilayer adsorption on liquid crystal droplets for microcapsule synthesis.

    Science.gov (United States)

    Priest, Craig; Quinn, Anthony; Postma, Almar; Zelikin, Alexander N; Ralston, John; Caruso, Frank

    2008-12-01

    Exploiting microfluidic principles, the potential for chip-based multilayer assembly for the synthesis of polymer microcapsules was investigated. We demonstrate that continuous flow microfluidic multilayer synthesis is a fast, efficient, automated alternative to conventional batch synthesis. In this work, we dispersed liquid crystal (LC) molecules (organic phase) as monodisperse droplets in an aqueous continuous phase containing the primary polymer and a suitable surfactant. The primary polymer was coadsorbed with the surfactant at the organic/aqueous interface, stabilizing the LC droplets against coalescence and providing a template for subsequent polymer adsorption. As the droplet templates are transported through the microfluidic channel, the polymer-containing aqueous continuous phase is selectively withdrawn and replaced with rinse solution, and then with an alternative polymer solution. This selective withdrawal and infusion cycle was repeated to assemble polymer multilayers onto the emulsion droplets. The process was followed using fluorescence microscopy of the fluorescently-labelled polymers at the LC interface and of the flowing polymer solutions during the sequential rinse stages. Cross-linking of the multilayers and removal of the dispersed LC phase resulted in polymer capsules retaining the high monodispersity of the droplet templates. This microfluidic approach significantly reduces the multilayer formation time (to <2 min for 3-layer capsules) of well-defined capsules that are envisaged to have benefits in biomedical applications, including drug delivery and encapsulated biochemical reactions.

  11. Comparisons of multilayer H2O adsorption onto the (110) surfaces of alpha-TiO2 and SnO2 as calculated with density functional theory.

    Science.gov (United States)

    Bandura, Andrei V; Kubicki, James D; Sofo, Jorge O

    2008-09-18

    Mono- and bilayer adsorption of H2O molecules on TiO2 and SnO 2 (110) surfaces has been investigated using static planewave density functional theory (PW DFT) simulations. Potential energies and structures were calculated for the associative, mixed, and dissociative adsorption states. The DOS of the bare and hydrated surfaces has been used for the analysis of the difference between the H2O interaction with TiO2 and SnO 2 surfaces. The important role of the bridging oxygen in the H2O dissociation process is discussed. The influence of the second layer of H2O molecules on relaxation of the surface atoms was estimated.

  12. Mono- and multilayers of molecular spoked carbazole wheels on graphite

    Directory of Open Access Journals (Sweden)

    Stefan-S. Jester

    2014-11-01

    Full Text Available Self-assembled monolayers of a molecular spoked wheel (a shape-persistent macrocycle with an intraannular spoke/hub system and its synthetic precursor are investigated by scanning tunneling microscopy (STM at the liquid/solid interface of 1-octanoic acid and highly oriented pyrolytic graphite. The submolecularly resolved STM images reveal that the molecules indeed behave as more or less rigid objects of certain sizes and shapes – depending on their chemical structures. In addition, the images provide insight into the multilayer growth of the molecular spoked wheels (MSWs, where the first adlayer acts as a template for the commensurate adsorption of molecules in the second layer.

  13. Landslide susceptibility assesssment in the Uttarakhand area (India) using GIS: a comparison study of prediction capability of naïve bayes, multilayer perceptron neural networks, and functional trees methods

    Science.gov (United States)

    Pham, Binh Thai; Tien Bui, Dieu; Pourghasemi, Hamid Reza; Indra, Prakash; Dholakia, M. B.

    2017-04-01

    The objective of this study is to make a comparison of the prediction performance of three techniques, Functional Trees (FT), Multilayer Perceptron Neural Networks (MLP Neural Nets), and Naïve Bayes (NB) for landslide susceptibility assessment at the Uttarakhand Area (India). Firstly, a landslide inventory map with 430 landslide locations in the study area was constructed from various sources. Landslide locations were then randomly split into two parts (i) 70 % landslide locations being used for training models (ii) 30 % landslide locations being employed for validation process. Secondly, a total of eleven landslide conditioning factors including slope angle, slope aspect, elevation, curvature, lithology, soil, land cover, distance to roads, distance to lineaments, distance to rivers, and rainfall were used in the analysis to elucidate the spatial relationship between these factors and landslide occurrences. Feature selection of Linear Support Vector Machine (LSVM) algorithm was employed to assess the prediction capability of these conditioning factors on landslide models. Subsequently, the NB, MLP Neural Nets, and FT models were constructed using training dataset. Finally, success rate and predictive rate curves were employed to validate and compare the predictive capability of three used models. Overall, all the three models performed very well for landslide susceptibility assessment. Out of these models, the MLP Neural Nets and the FT models had almost the same predictive capability whereas the MLP Neural Nets (AUC = 0.850) was slightly better than the FT model (AUC = 0.849). The NB model (AUC = 0.838) had the lowest predictive capability compared to other models. Landslide susceptibility maps were final developed using these three models. These maps would be helpful to planners and engineers for the development activities and land-use planning.

  14. EUV multilayer mirror, optical system including a multilayer mirror and method of manufacturing a multilayer mirror

    NARCIS (Netherlands)

    Huang, Qiushi; Louis, Eric; Bijkerk, Frederik; de Boer, Meint J.; von Blanckenhagen, G.

    2016-01-01

    A multilayer mirror (M) reflecting extreme ultraviolet (EUV) radiation from a first wave-length range in a EUV spectral region comprises a substrate (SUB) and a stack of layers (SL) on the substrate, the stack of layers comprising layers comprising a low index material and a high index material, the

  15. Probing the mechanism of non-linear growth of polyelectrolyte multilayers

    Science.gov (United States)

    Selin, Victor; Ankner, John; Sukhishvili, Svetlana A.

    We report a study of the non-linear growth of electrostatically assembled polyelectrolyte multilayer films (PEM). PEM films were assembled by the layer-by-layer (LbL) technique using poly(methacrylic acid) as a polyanion and quaternized poly-2-(dimethylamino)ethyl methacrylate as a polycation. During film build-up, the thickness evolution as well as water uptake of PEM films were measured by in situ ellipsometry, whereas neutron reflectometry was used to probe the evolution of film internal structure as a function of deposition time. First, we found that during non-linear growth, films remain in a highly swollen hydrogel-like state, but the swelling ratio demonstrated an odd/even effect, with much larger hydration of the PEM when the terminal layer was the polycation. Second, while polycation chains were able to diffuse into the bulk of the film with a diffusion constant several orders of magnitude lower than in their free, unbound state, polyanion invasion was limited to the film surface. The amounts of the polycation and the polyanion adsorbed per deposition cycle were also drastically different. We quantify chemical composition and water content in the film, and correlate these data with the depth polyelectrolyte chains penetrate within the film during PEM construction.

  16. The potential of cashew gum functionalization as building blocks for layer-by-layer films.

    Science.gov (United States)

    Leite, Álvaro J; Costa, Rui R; Costa, Ana M S; Maciel, Jeanny S; Costa, José F G; de Paula, Regina C M; Mano, João F

    2017-10-15

    Cashew gum (CG), an exudate polysaccharide from Anacardium occidentale trees, was carboxymethylated (CGCm) and oxidized (CGO). These derivatives were characterized by FTIR and zeta potential measurements confirming the success of carboxymethylation and oxidation reactions. Nanostructured multilayered films were then produced through layer-by-layer (LbL) assembly in conjugation with chitosan via electrostatic interactions or Schiff bases covalent bonds. The films were analyzed by QCM-D and AFM. CG functionalization increased the film thickness, with the highest thickness being achieved for the lowest oxidation degree. The roughest surface was obtained for the CGO with the highest oxidation degree due to the predominance of covalent Schiff bases. This work shows that nanostructured films can be assembled and stabilized by covalent bonds in alternative to the conventional electrostatic ones. Moreover, the functionalization of CG can increase its feasibility in multilayers films, widening its potential in biomedical, food industry, or environmental applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Novel Luminescent Multilayer Films Containing π-Conjugated Anionic Polymer with Electronic Microenvironment

    Directory of Open Access Journals (Sweden)

    Tianlei Wang

    2016-09-01

    Full Text Available Layered double hydroxides (LDHs, luminescent π-conjugated anionic polymer and montmorillonite (MMT were orderly assembled into luminescent multilayer films via layer-by-layer self-assembly method. The electronic microenvironment (EME, the structure of which is like a traditional capacitor, can be constructed by exfoliated LDHs or MMT nanosheets. In addition, the rigid inorganic laminated configuration can offer stable surroundings between the interlayers. As a result, we conclude that EME can extend the luminescent lifespans of multilayer films substantially, due to affecting relaxation times of π-conjugated anionic polymer. Consequently, because of the remarkable impact on better photoemission behaviors of luminescent π-conjugated anionic polymer, EME assembled by LDHs or MMT nanosheets have had high hopes attached to them. They are expected to have the potential for designing, constructing, and investigating novel light-emitting thin films.

  18. Acid-base equilibria of multilayered pseudo-polyelectrolytes

    Science.gov (United States)

    Mateo, Ayeisca E.; Priefer, Ronny

    2015-11-01

    The use of weak polyelectrolytes in multilayer polymer systems provides a means of altering the physicochemical properties of these thin films. Previously, we have examined the limits of the polyanions by incorporating the pseudo-polyelectrolytes (pPE's), poly(4-vinylphenol) (PVPh) and poly[5-(2-trifluoromethyl-1,1,1-trifluoro-2-hydroxypropyl)-2-norbornene] (PNBHFA). These pPE's, although being polyacids, should have pKa values in the basic versus acidic pH range. In order to determine the pKa(app) value of these polymers, once multilayered onto Snowtex silica particles with the weak polyelectrolyte, poly(allylamine hydrochloride) (PAH), we employed zeta potential. PVPh demonstrated pKa(app) values ranging from 10.55 to 11.08 which varied based upon assembly pH conditions as well as layer number. PAH yielded pKa(app) values ranging between 9.81 and 10.99 when multilayered with PVPh and 9.91-11.04 when partnered with PNBHFA. However, from our study it would appear that PNBHFA does not interact with PAH electrostatically, but rather via H-bonding, and therefore should actually not be classified as a pPE.

  19. Multilayered materials based on biopolymers as drug delivery systems.

    Science.gov (United States)

    Vilela, Carla; Figueiredo, Ana R P; Silvestre, Armando J D; Freire, Carmen S R

    2017-02-01

    The design of efficient therapeutic delivery devices has become a tremendously active area of research with a strong contribution from the layer-by-layer (LbL) technology. The application of this simple yet firmly established technique for the design of drug reservoirs originates a multitude of multilayered systems of tailored architecture and with a high level of control of drug administration. Areas covered: This review will focus on the most recent and original research on LbL assemblies based on biopolymers including polysaccharides, polypeptides and proteins, with potential use in drug delivery. Herein, drug reservoirs consisting of multilayered planar films and capsules will be examined with emphasis on the ones benefiting from the non-cytotoxic and biocompatible nature of biopolymers, which are suitable to load, protect and release a high payload of toxic and fragile drugs. Expert opinion: The combination of biopolymers with LbL technology has undergone extensive research, still, there is a multitude of R&D opportunities for the design of smart drug delivery systems with distinct multilayered morphologies, low immunological response, non-invasive drug release devices, as well as the design of theranostic systems combining diagnostics and therapeutic features. Further developments in terms of scaling towards mass production in the pharmaceutical industry are expected in the long-term.

  20. Charge carrier transport in defective reduced graphene oxide as quantum dots and nanoplatelets in multilayer films

    Science.gov (United States)

    Jimenez, Mawin J. M.; Oliveira, Rafael F.; Almeida, Tiago P.; Hensel Ferreira, Rafael C.; Bufon, Carlos Cesar B.; Rodrigues, Varlei; Pereira-da-Silva, Marcelo A.; Gobbi, Ângelo L.; Piazzetta, Maria H. O.; Riul, Antonio, Jr.

    2017-12-01

    Graphene is a breakthrough 2D material due to its unique mechanical, electrical, and thermal properties, with considerable responsiveness in real applications. However, the coverage of large areas with pristine graphene is a challenge and graphene derivatives have been alternatively exploited to produce hybrid and composite materials that allow for new developments, considering also the handling of large areas using distinct methodologies. For electronic applications there is significant interest in the investigation of the electrical properties of graphene derivatives and related composites to determine whether the characteristic 2D charge transport of pristine graphene is preserved. Here, we report a systematic study of the charge transport mechanisms of reduced graphene oxide chemically functionalized with sodium polystyrene sulfonate (PSS), named as GPSS. GPSS was produced either as quantum dots (QDs) or nanoplatelets (NPLs), being further nanostructured with poly(diallyldimethylammonium chloride) through the layer-by-layer (LbL) assembly to produce graphene nanocomposites with molecular level control. Current–voltage (I–V) measurements indicated a meticulous growth of the LbL nanostructures onto gold interdigitated electrodes (IDEs), with a space-charge-limited current dominated by a Mott-variable range hopping mechanism. A 2D intra-planar conduction within the GPSS nanostructure was observed, which resulted in effective charge carrier mobility (μ) of 4.7 cm2 V‑1 s‑1 for the QDs and 34.7 cm2 V‑1 s‑1 for the NPLs. The LbL assemblies together with the dimension of the materials (QDs or NPLs) were favorably used for the fine tuning and control of the charge carrier mobility inside the LbL nanostructures. Such 2D charge conduction mechanism and high μ values inside an interlocked multilayered assembly containing graphene-based nanocomposites are of great interest for organic devices and functionalization of interfaces.

  1. Sequence assembly

    DEFF Research Database (Denmark)

    Scheibye-Alsing, Karsten; Hoffmann, S.; Frankel, Annett Maria

    2009-01-01

    Despite the rapidly increasing number of sequenced and re-sequenced genomes, many issues regarding the computational assembly of large-scale sequencing data have remain unresolved. Computational assembly is crucial in large genome projects as well for the evolving high-throughput technologies...... and plays an important role in processing the information generated by these methods. Here, we provide a comprehensive overview of the current publicly available sequence assembly programs. We describe the basic principles of computational assembly along with the main concerns, such as repetitive sequences...... in genomic DNA, highly expressed genes and alternative transcripts in EST sequences. We summarize existing comparisons of different assemblers and provide a detailed descriptions and directions for download of assembly programs at: http://genome.ku.dk/resources/assembly/methods.html....

  2. Thermal Performance of a Customized Multilayer Insulation (MLI). Design and Fabrication of Test Facility Hardware

    Science.gov (United States)

    Leonhard, K. E.

    1975-01-01

    The design, fabrication, and assembly of hardware for testing the performance of a customized multilayer insulation are discussed. System components described include the thermal payload simulator, the modified cryoshroud, and a tank back pressure control device designed to maintain a constant liquid boiling point during the thermal evaluation of the multilayer insulation. The thermal payload simulator will provide a constant temperature surface in the range of 20.5 to 417K (37 to 750R) for the insulated tank to view. The cryoshroud was modified to establish a low temperature black body cavity while limiting liquid hydrogen usage to a minimum feasible rate.

  3. Assembling large, complex environmental metagenomes

    Energy Technology Data Exchange (ETDEWEB)

    Howe, A. C. [Michigan State Univ., East Lansing, MI (United States). Microbiology and Molecular Genetics, Plant Soil and Microbial Sciences; Jansson, J. [USDOE Joint Genome Institute (JGI), Walnut Creek, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Earth Sciences Division; Malfatti, S. A. [USDOE Joint Genome Institute (JGI), Walnut Creek, CA (United States); Tringe, S. G. [USDOE Joint Genome Institute (JGI), Walnut Creek, CA (United States); Tiedje, J. M. [Michigan State Univ., East Lansing, MI (United States). Microbiology and Molecular Genetics, Plant Soil and Microbial Sciences; Brown, C. T. [Michigan State Univ., East Lansing, MI (United States). Microbiology and Molecular Genetics, Computer Science and Engineering

    2012-12-28

    The large volumes of sequencing data required to sample complex environments deeply pose new challenges to sequence analysis approaches. De novo metagenomic assembly effectively reduces the total amount of data to be analyzed but requires significant computational resources. We apply two pre-assembly filtering approaches, digital normalization and partitioning, to make large metagenome assemblies more computationaly tractable. Using a human gut mock community dataset, we demonstrate that these methods result in assemblies nearly identical to assemblies from unprocessed data. We then assemble two large soil metagenomes from matched Iowa corn and native prairie soils. The predicted functional content and phylogenetic origin of the assembled contigs indicate significant taxonomic differences despite similar function. The assembly strategies presented are generic and can be extended to any metagenome; full source code is freely available under a BSD license.

  4. Multilayer X-ray optics at CHESS.

    Science.gov (United States)

    Kazimirov, Alexander; Smilgies, Detlef M; Shen, Qun; Xiao, Xianghui; Hao, Quan; Fontes, Ernest; Bilderback, Donald H; Gruner, Sol M; Platonov, Yuriy; Martynov, Vladimir V

    2006-03-01

    Almost half of the X-ray beamlines at the Cornell High Energy Synchrotron Source (CHESS) are based on multilayer optics. ;Traditional' multilayers with an energy resolution of DeltaE/E approximately 2% are routinely used to deliver X-ray flux enhanced by a factor of 10(2) in comparison with standard Si(111) optics. Sagittal-focusing multilayers with fixed radius provide an additional factor of 10 gain in flux density. High-resolution multilayer optics with DeltaE/E approximately 0.2% are now routinely used by MacCHESS crystallographers. New wide-bandpass multilayers with DeltaE/E = 5% and 10% have been designed and tested for potential applications in macromolecular crystallography. Small d-spacing multilayers with d < or = 20 A have been successfully used to extend the energy range of multilayer optics. Analysis of the main characteristics of the Mo/B4C and W/B4C small d-spacing multilayer optics shows enhancement in their performance at higher energies. Chemical vapour deposited SiC, with a bulk thermal conductivity of a factor of two higher than that of silicon, has been successfully introduced as a substrate material for multilayer optics. Characteristics of different types of multilayer optics at CHESS beamlines and their applications in a variety of scattering, diffraction and imaging techniques are discussed.

  5. Super-hydrophobic multilayer coatings with layer number tuned swapping in surface wettability and redox catalytic anti-corrosion application.

    Science.gov (United States)

    Syed, Junaid Ali; Tang, Shaochun; Meng, Xiangkang

    2017-06-30

    The wetting characteristic of a metal surface can be controlled by employing different coating materials and external stimuli, however, layer number (n) modulated surface swapping between hydrophobicity and hydrophilicity in a multilayer structure to achieve prolonged anti-corrosion ability was not taken into consideration. In this study, we proposed a layer-by-layer (LbL) spin assembled polyaniline-silica composite/tetramethylsilane functionalized silica nanoparticles (PSC/TMS-SiO2) coating with the combined effect of super-hydrophobicity and enhanced anti-corrosion ability. Interestingly, the hierarchical integration of two coating materials with inherently different surface roughness and energy in a multilayer structure allows the wetting feature to swap from hydrophobic to hydrophilic state by modulating n with decreasing hydrophilicity. The samples with odd n (TMS-SiO2 surface) are hydrophobic while the samples with even n (PSC surface) exhibits the hydrophilic character. The TMS-SiO2 content was optimized to achieve super-hydrophobic coating with significantly high water contact angle (CA) 153° ± 2° and small sliding angle (SA) 6° ± 2°. Beside its self-cleaning behavior, the electro-active PSC/TMS-SiO2 coating also exhibits remarkably enhanced corrosion resistance against aggressive media. The corrosion resistance of the coating was remained stable even after 240 h of exposure, this enhancement is attributed to super-hydrophobicity and anodic shift in corrosion potential.

  6. Anomalous magnetoresistance in Fibonacci multilayers.

    Energy Technology Data Exchange (ETDEWEB)

    Machado, L. D.; Bezerra, C. G.; Correa, M. A.; Chesman, C.; Pearson, J. E.; Hoffmann, A. (Materials Science Division); (Universidade Federal do Rio Grande do Norte)

    2012-01-01

    We theoretically investigated magnetoresistance curves in quasiperiodic magnetic multilayers for two different growth directions, namely, [110] and [100]. We considered identical ferromagnetic layers separated by nonmagnetic layers with two different thicknesses chosen based on the Fibonacci sequence. Using parameters for Fe/Cr multilayers, four terms were included in our description of the magnetic energy: Zeeman, cubic anisotropy, bilinear coupling, and biquadratic coupling. The minimum energy was determined by the gradient method and the equilibrium magnetization directions found were used to calculate magnetoresistance curves. By choosing spacers with a thickness such that biquadratic coupling is stronger than bilinear coupling, unusual behaviors for the magnetoresistance were observed: (i) for the [110] case, there is a different behavior for structures based on even and odd Fibonacci generations, and, more interesting, (ii) for the [100] case, we found magnetic field ranges for which the magnetoresistance increases with magnetic field.

  7. A nanoscale bio-inspired light-harvesting system developed from self-assembled alkyl-functionalized metallochlorin nano-aggregates

    KAUST Repository

    Ocakoǧlu, Kasim

    2014-01-01

    Self-assembled supramolecular organization of nano-structured biomimetic light-harvesting modules inside solid-state nano-templates can be exploited to develop excellent light-harvesting materials for artificial photosynthetic devices. We present here a hybrid light-harvesting system mimicking the chlorosomal structures of the natural photosynthetic system using synthetic zinc chlorin units (ZnChl-C6, ZnChl-C12 and ZnChl-C 18) that are self-aggregated inside the anodic aluminum oxide (AAO) nano-channel membranes. AAO nano-templates were modified with a TiO2 matrix and functionalized with long hydrophobic chains to facilitate the formation of supramolecular Zn-chlorin aggregates. The transparent Zn-chlorin nano-aggregates inside the alkyl-TiO2 modified AAO nano-channels have a diameter of ∼120 nm in a 60 μm length channel. UV-Vis studies and fluorescence emission spectra further confirm the formation of the supramolecular ZnChl aggregates from monomer molecules inside the alkyl-functionalized nano-channels. Our results prove that the novel and unique method can be used to produce efficient and stable light-harvesting assemblies for effective solar energy capture through transparent and stable nano-channel ceramic materials modified with bio-mimetic molecular self-assembled nano-aggregates. © 2014 the Partner Organisations.

  8. Phase Transitions in the Nucleus: the functional implications of concentration-dependent assembly of a Liquid-like RNA/Protein Body

    Science.gov (United States)

    Zhu, Lian; Weber, Stephanie; Berry, Joel; Vaidya, Nilesh; Haataja, Mikko; Brangwynne, Clifford

    2015-03-01

    The nucleolus is a liquid-like membrane-less nuclear body which plays an important role in cell growth and size control. By modulating nucleolar component concentration through RNAi conditions that change C. elegans cell size, we find that nucleoli only assemble above a threshold concentration; moreover, the ripening dynamics of nucleated droplets are consistent with the hypothesis that the assembly of the nucleolus represents an intracellular liquid-liquid phase transition. A key question is how this phase-transition is linked to the primary function of the nucleolus, in transcribing and processing ribosomal RNA. To address this, we characterize the localization of RNA Polymerase I, a key transcriptional enzyme, into nucleolar foci as a function of nucleolar component concentration. Our results suggest that there are a small number of key disordered phosphoproteins that may serve as a link between transcription and assembly. Finally, we present preliminary results using a reduced model system consisting of purified nucleolar proteins to assess the ability of nucleolar proteins to drive liquid-liquid phase separation in vitro. These results lay the foundation for a quantitative understanding of intracellular phase transitions and their impact on biomedically-critical RNA-processing steps.

  9. Constructing multilayers with absorbing materials

    OpenAIRE

    Larruquert, Juan Ignacio; Vidal-Dasilva, M.; García-Cortés, S.; Fernández Perea, Mónica; Méndez, José Antonio; Aznárez, José Antonio

    2010-01-01

    The strong absorption of materials in the extreme ultraviolet (EUV) above ~50 nm has precluded the development of efficient coatings. The development of novel coatings with improved EUV performance is presented. An extensive research was performed on the search and characterization of materials with moderate absorption, such as various lanthanides. Based on this research, novel multilayers based on Yb, Al, and SiO have been developed with a narrowband performance in the 50-92 nm range. Furthe...

  10. Influence of functionalized silicones on hair fiber-fiber interactions and on the relationship with the macroscopic behavior of hair assembly.

    Science.gov (United States)

    Dussaud, Anne; Fieschi-Corso, Lara

    2009-01-01

    It is well established that silicones alter hair surface properties and that silicones have a significant impact on the macroscopic behavior of hair assembly, such as visual appearance, combing performance and manageability of the hair. In order to fine-tune the chemistry of functionlized silicones for specific consumer benefits and hair types, we investigated the influence of silicones on hair fiber-fiber interactions and their correlation to hair volume. The incline plane fiber loop method, implemented with a high-precision motorized rotary stage, was used to quantify the fiber-fiber interactions. Low load static friction was studied as a function of polymer molecular weight, dose and chemical architecture. This information was related to the macroscopic behavior of hair assembly, using virgin curly hair in high humidity.

  11. Structural and magnetic properties of Ce/Fe and Ce/FeCoV multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Tixier, S.; Boeni, P. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Mannix, D.; Stirling, W.G. [Liverpool Univ. (United Kingdom); Lander, G.H.

    1997-09-01

    Ce/Fe and Ce/FeCoV multilayers have been grown by magnetron sputtering. The interfaces are well defined and the layers are crystalline down to an individual layer thickness of 20 A. Ce/FeCoV multilayers show sharper interfaces than Ce/Fe but some loss of crystallinity is observed. Hysteresis loops obtained by SQUID show different behaviour of the bulk magnetisation as a function of the layer thickness. Fe moments are found by Moessbauer spectroscopy to be perpendicular to the interfaces for multilayers with small periodicity. (author) 2 figs., 2 refs.

  12. Ultra-thin multilayer capacitors.

    Energy Technology Data Exchange (ETDEWEB)

    Renk, Timothy Jerome; Monson, Todd C.

    2009-06-01

    The fabrication of ultra-thin lanthanum-doped lead zirconium titanate (PLZT) multilayer ceramic capacitors (MLCCs) using a high-power pulsed ion beam was studied. The deposition experiments were conducted on the RHEPP-1 facility at Sandia National Laboratories. The goal of this work was to increase the energy density of ceramic capacitors through the formation of a multilayer device with excellent materials properties, dielectric constant, and standoff voltage. For successful device construction, there are a number of challenging requirements including achieving correct stoichiometric and crystallographic composition of the deposited PLZT, as well as the creation of a defect free homogenous film. This report details some success in satisfying these requirements, although 900 C temperatures were necessary for PLZT perovskite phase formation. These temperatures were applied to a previously deposited multi-layer film which was then post-annealed to this temperature. The film exhibited mechanical distress attributable to differences in the coefficient of thermal expansion (CTE) of the various layers. This caused significant defects in the deposited films that led to shorts across devices. A follow-on single layer deposition without post-anneal produced smooth layers with good interface behavior, but without the perovskite phase formation. These issues will need to be addressed in order for ion beam deposited MLCCs to become a viable technology. It is possible that future in-situ heating during deposition may address both the CTE issue, and result in lowered processing temperatures, which in turn could raise the probability of successful MLCC formation.

  13. Mathematical Formulation of Multilayer Networks

    Directory of Open Access Journals (Sweden)

    Manlio De Domenico

    2013-12-01

    Full Text Available A network representation is useful for describing the structure of a large variety of complex systems. However, most real and engineered systems have multiple subsystems and layers of connectivity, and the data produced by such systems are very rich. Achieving a deep understanding of such systems necessitates generalizing “traditional” network theory, and the newfound deluge of data now makes it possible to test increasingly general frameworks for the study of networks. In particular, although adjacency matrices are useful to describe traditional single-layer networks, such a representation is insufficient for the analysis and description of multiplex and time-dependent networks. One must therefore develop a more general mathematical framework to cope with the challenges posed by multilayer complex systems. In this paper, we introduce a tensorial framework to study multilayer networks, and we discuss the generalization of several important network descriptors and dynamical processes—including degree centrality, clustering coefficients, eigenvector centrality, modularity, von Neumann entropy, and diffusion—for this framework. We examine the impact of different choices in constructing these generalizations, and we illustrate how to obtain known results for the special cases of single-layer and multiplex networks. Our tensorial approach will be helpful for tackling pressing problems in multilayer complex systems, such as inferring who is influencing whom (and by which media in multichannel social networks and developing routing techniques for multimodal transportation systems.

  14. Mathematical Formulation of Multilayer Networks

    Science.gov (United States)

    De Domenico, Manlio; Solé-Ribalta, Albert; Cozzo, Emanuele; Kivelä, Mikko; Moreno, Yamir; Porter, Mason A.; Gómez, Sergio; Arenas, Alex

    2013-10-01

    A network representation is useful for describing the structure of a large variety of complex systems. However, most real and engineered systems have multiple subsystems and layers of connectivity, and the data produced by such systems are very rich. Achieving a deep understanding of such systems necessitates generalizing “traditional” network theory, and the newfound deluge of data now makes it possible to test increasingly general frameworks for the study of networks. In particular, although adjacency matrices are useful to describe traditional single-layer networks, such a representation is insufficient for the analysis and description of multiplex and time-dependent networks. One must therefore develop a more general mathematical framework to cope with the challenges posed by multilayer complex systems. In this paper, we introduce a tensorial framework to study multilayer networks, and we discuss the generalization of several important network descriptors and dynamical processes—including degree centrality, clustering coefficients, eigenvector centrality, modularity, von Neumann entropy, and diffusion—for this framework. We examine the impact of different choices in constructing these generalizations, and we illustrate how to obtain known results for the special cases of single-layer and multiplex networks. Our tensorial approach will be helpful for tackling pressing problems in multilayer complex systems, such as inferring who is influencing whom (and by which media) in multichannel social networks and developing routing techniques for multimodal transportation systems.

  15. Rocket Assembly and Checkout Facility

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Integrates, tests, and calibrates scientific instruments flown on sounding rocket payloads. The scientific instruments are assembled on an optical bench;...

  16. Kinetic Effects on Self-Assembly and Function of Protein-Polymer Bioconjugates in Thin Films Prepared by Flow Coating

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Dongsook [Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave Cambridge MA 02142 USA; Huang, Aaron [Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave Cambridge MA 02142 USA; Olsen, Bradley D. [Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave Cambridge MA 02142 USA

    2016-11-04

    The self-assembly of nanostructured globular protein arrays in thin films is demonstrated using protein–polymer block copolymers based on a model protein mCherry and the polymer poly(oligoethylene glycol acrylate) (POEGA). Conjugates are flow coated into thin films on a poly(ethylene oxide) grafted Si surface, forming self-assembled cylindrical nanostructures with POEGA domains selectively segregating to the air–film interface. Long-range order and preferential arrangement of parallel cylinders templated by selective surfaces are demonstrated by controlling relative humidity. Long-range order increases with coating speed when the film thicknesses are kept constant, due to reduced nucleation per unit area of drying film. Fluorescence emission spectra of mCherry in films prepared at <25% relative humidity shows a small shift suggesting that proteins are more perturbed at low humidity than high humidity or the solution state.

  17. Assembly of synthetic functional cellulosomal structures onto theLactobacillus plantarumcell surface - a potent member of the gut microbiome.

    Science.gov (United States)

    Stern, Johanna; Moraïs, Sarah; Ben-David, Yonit; Salama, Rachel; Shamshoum, Melina; Lamed, Raphael; Shoham, Yuval; Bayer, Edward A; Mizrahi, Itzhak

    2018-02-16

    Heterologous display of enzymes on microbial cell surfaces is an extremely desirable approach, since it enables the engineered microbe to interact directly with the plant-wall extracellular polysaccharide matrix. In recent years, attempts have been made to endow non-cellulolytic microbes with genetically engineered cellulolytic capabilities for improved hydrolysis of lignocellulosic biomass and for advanced probiotics. Thus far, however, owing to the hurdles of secreting and assembling large, intricate complexes on the bacterial cell wall, only free cellulases or relatively simple cellulosome assemblies have been introduced into live bacteria. Here, we employed the "adaptor scaffoldin" strategy to overcome the low levels of protein displayed on the bacterial cell surface. The approach mimics natural cellulosome elaborated architectures, thus exploiting the exponential features of their Lego-like combinatorics. Using this approach, we produced several bacterial consortia of Lactobacillus plantarum , a potent gut microbe which provides a very robust genetic framework for lignocellulosic degradation. We successfully engineered surface display of large, fully active self-assembling cellulosomal complexes containing an unprecedented number of catalytic subunits all produced in vivo by the cell-consortia. Our results demonstrate superior enzyme stability and performance of the cellulosomal machinery, compared to the equivalent secreted free enzyme system and high cellulase-to-xylanase ratios proved beneficial for efficient degradation of wheat straw. Importance The multiple benefits of lactic acid bacteria are well established in health and industry. Here we present an approach to extensively increase the cell-surface display of proteins via successive assembly of interactive components. Our findings present a stepping stone towards proficient engineering of Lactobacillus plantarum , a widespread, environmentally important bacterium and potent microbiome member, for

  18. Evolutionary Conservation in Biogenesis of β-Barrel Proteins Allows Mitochondria to Assemble a Functional Bacterial Trimeric Autotransporter Protein*

    Science.gov (United States)

    Ulrich, Thomas; Oberhettinger, Philipp; Schütz, Monika; Holzer, Katharina; Ramms, Anne S.; Linke, Dirk; Autenrieth, Ingo B.; Rapaport, Doron

    2014-01-01

    Yersinia adhesin A (YadA) belongs to a class of bacterial adhesins that form trimeric structures. Their mature form contains a passenger domain and a C-terminal β-domain that anchors the protein in the outer membrane (OM). Little is known about how precursors of such proteins cross the periplasm and assemble into the OM. In the present study we took advantage of the evolutionary conservation in the biogenesis of β-barrel proteins between bacteria and mitochondria. We previously observed that upon expression in yeast cells, bacterial β-barrel proteins including the transmembrane domain of YadA assemble into the mitochondrial OM. In the current study we found that when expressed in yeast cells both the monomeric and trimeric forms of full-length YadA were detected in mitochondria but only the trimeric species was fully integrated into the OM. The oligomeric form was exposed on the surface of the organelle in its native conformation and maintained its capacity to adhere to host cells. The co-expression of YadA with a mitochondria-targeted form of the bacterial periplasmic chaperone Skp, but not with SurA or SecB, resulted in enhanced levels of both forms of YadA. Taken together, these results indicate that the proper assembly of trimeric autotransporter can occur also in a system lacking the lipoproteins of the BAM machinery and is specifically enhanced by the chaperone Skp. PMID:25190806

  19. Multilayer Radar Absorbing Non-Woven Material

    Science.gov (United States)

    Dedov, A. V.; Nazarov, V. G.

    2016-06-01

    We study the electrical properties of multilayer radar absorbing materials obtained by adding nonwoven sheets of dielectric fibers with an intermediate layer of electrically conductive carbon fibers. Multilayer materials that absorb electromagnetic radiation in a wide frequency range are obtained by varying the content of the carbon fibers. The carbon-fiber content dependent mechanism of absorption of electromagnetic radiation by sheets and multilayer materials is considered.

  20. Multi-layer seal for electrochemical devices

    Science.gov (United States)

    Chou, Yeong-Shyung [Richland, WA; Meinhardt, Kerry D [Kennewick, WA; Stevenson, Jeffry W [Richland, WA

    2010-09-14

    Multi-layer seals are provided that find advantageous use for reducing leakage of gases between adjacent components of electrochemical devices. Multi-layer seals of the invention include a gasket body defining first and second opposing surfaces and a compliant interlayer positioned adjacent each of the first and second surfaces. Also provided are methods for making and using the multi-layer seals, and electrochemical devices including said seals.

  1. Structure-Function Analysis of Friedreich's Ataxia Mutants Reveals Determinants of Frataxin Binding and Activation of the Fe-S Assembly Complex

    Energy Technology Data Exchange (ETDEWEB)

    Bridwell-Rabb, Jennifer; Winn, Andrew M; Barondeau, David P [TAM

    2012-08-01

    Friedreich's ataxia (FRDA) is a progressive neurodegenerative disease associated with the loss of function of the protein frataxin (FXN) that results from low FXN levels due to a GAA triplet repeat expansion or, occasionally, from missense mutations in the FXN gene. Here biochemical and structural properties of FXN variants, including three FRDA missense mutations (N146K, Q148R, and R165C) and three related mutants (N146A, Q148G, and Q153A), were determined in an effort to understand the structural basis for the loss of function. In vitro assays revealed that although the three FRDA missense mutations exhibited similar losses of cysteine desulfurase and Fe-S cluster assembly activities, the causes for these activation defects were distinct. The R165C variant exhibited a kcat/KM higher than that of native FXN but weak binding to the NFS1, ISD11, and ISCU2 (SDU) complex, whereas the Q148R variant exhibited the lowest kcat/KM of the six tested FXN variants and only a modest binding deficiency. The order of the FXN binding affinities for the SDU Fe-S assembly complex was as follows: FXN > Q148R > N146A > Q148G > N146K > Q153A > R165C. Four different classes of FXN variants were identified on the basis of their biochemical properties. Together, these structure-function studies reveal determinants for the binding and allosteric activation of the Fe-S assembly complex and provide insight into how FRDA missense mutations are functionally compromised.

  2. Interface stress in Au/Ni multilayers

    DEFF Research Database (Denmark)

    Schweitz, K.O.; Böttiger, J.; Chevallier, J.

    2000-01-01

    The effect of intermixing on the apparent interface stress is studied in -textured dc-magnetron sputtered Au/Ni multilayers by use of two methods commonly used for determining interface stress. The method using profilometry and in-plane x-ray diffraction does not take intermixing...... into account and yields an apparent interface stress of -8.46 +/- 0.99 J m(-2). However, observed discrepancies between model calculations and measured high-angle x-ray diffractograms indicate intermixing, and by use of the profilometry and sin(2) psi method the real interface stress value of -2.69 +/- 0.43 J...... m(-2) is found. This method also reveals a significant and systematic change of the stress-free lattice parameter of both constituents as a function of modulation period which is shown to account for the difference between the two findings. The method using in-plane diffraction is thus shown...

  3. Programming molecular self-assembly of intrinsically disordered proteins containing sequences of low complexity

    Science.gov (United States)

    Simon, Joseph R.; Carroll, Nick J.; Rubinstein, Michael; Chilkoti, Ashutosh; López, Gabriel P.

    2017-06-01

    Dynamic protein-rich intracellular structures that contain phase-separated intrinsically disordered proteins (IDPs) composed of sequences of low complexity (SLC) have been shown to serve a variety of important cellular functions, which include signalling, compartmentalization and stabilization. However, our understanding of these structures and our ability to synthesize models of them have been limited. We present design rules for IDPs possessing SLCs that phase separate into diverse assemblies within droplet microenvironments. Using theoretical analyses, we interpret the phase behaviour of archetypal IDP sequences and demonstrate the rational design of a vast library of multicomponent protein-rich structures that ranges from uniform nano-, meso- and microscale puncta (distinct protein droplets) to multilayered orthogonally phase-separated granular structures. The ability to predict and program IDP-rich assemblies in this fashion offers new insights into (1) genetic-to-molecular-to-macroscale relationships that encode hierarchical IDP assemblies, (2) design rules of such assemblies in cell biology and (3) molecular-level engineering of self-assembled recombinant IDP-rich materials.

  4. A Method for Designing Assembly Tolerance Networks of Mechanical Assemblies

    Directory of Open Access Journals (Sweden)

    Yi Zhang

    2012-01-01

    Full Text Available When designing mechanical assemblies, assembly tolerance design is an important issue which must be seriously considered by designers. Assembly tolerances reflect functional requirements of assembling, which can be used to control assembling qualities and production costs. This paper proposes a new method for designing assembly tolerance networks of mechanical assemblies. The method establishes the assembly structure tree model of an assembly based on its product structure tree model. On this basis, assembly information model and assembly relation model are set up based on polychromatic sets (PS theory. According to the two models, the systems of location relation equations and interference relation equations are established. Then, using methods of topologically related surfaces (TTRS theory and variational geometric constraints (VGC theory, three VGC reasoning matrices are constructed. According to corresponding relations between VGCs and assembly tolerance types, the reasoning matrices of tolerance types are also established by using contour matrices of PS. Finally, an exemplary product is used to construct its assembly tolerance networks and meanwhile to verify the feasibility and effectiveness of the proposed method.

  5. Multi-Layer Electrospun Membrane Mimicking Tendon Sheath for Prevention of Tendon Adhesions

    Directory of Open Access Journals (Sweden)

    Shichao Jiang

    2015-03-01

    Full Text Available Defect of the tendon sheath after tendon injury is a main reason for tendon adhesions, but it is a daunting challenge for the biomimetic substitute of the tendon sheath after injury due to its multi-layer membrane-like structure and complex biologic functions. In this study, a multi-layer membrane with celecoxib-loaded poly(l-lactic acid-polyethylene glycol (PELA electrospun fibrous membrane as the outer layer, hyaluronic acid (HA gel as middle layer, and PELA electrospun fibrous membrane as the inner layer was designed. The anti-adhesion efficacy of this multi-layer membrane was compared with a single-layer use in rabbit flexor digitorum profundus tendon model. The surface morphology showed that both PELA fibers and celecoxib-loaded PELA fibers in multi-layer membrane were uniform in size, randomly arrayed, very porous, and smooth without beads. Multi-layer membrane group had fewer peritendinous adhesions and better gliding than the PELA membrane group and control group in gross and histological observation. The similar mechanical characteristic and collagen expression of tendon repair site in the three groups indicated that the multi-layer membrane did not impair tendon healing. Taken together, our results demonstrated that such a biomimetic multi-layer sheath could be used as a potential strategy in clinics for promoting tendon gliding and preventing adhesion without poor tendon healing.

  6. Magnetic depth profiling of Fe/Au multilayer using neutron ...

    Indian Academy of Sciences (India)

    Au multilayer sample for characterizing the layer structure and magnetic moment density profile. Fe/Au multilayer shows strong spin-dependent scattering at interfaces, making it a prospective GMR material. Fe/Au multilayer with bilayer ...

  7. Evolutionary conservation in biogenesis of β-barrel proteins allows mitochondria to assemble a functional bacterial trimeric autotransporter protein.

    Science.gov (United States)

    Ulrich, Thomas; Oberhettinger, Philipp; Schütz, Monika; Holzer, Katharina; Ramms, Anne S; Linke, Dirk; Autenrieth, Ingo B; Rapaport, Doron

    2014-10-24

    Yersinia adhesin A (YadA) belongs to a class of bacterial adhesins that form trimeric structures. Their mature form contains a passenger domain and a C-terminal β-domain that anchors the protein in the outer membrane (OM). Little is known about how precursors of such proteins cross the periplasm and assemble into the OM. In the present study we took advantage of the evolutionary conservation in the biogenesis of β-barrel proteins between bacteria and mitochondria. We previously observed that upon expression in yeast cells, bacterial β-barrel proteins including the transmembrane domain of YadA assemble into the mitochondrial OM. In the current study we found that when expressed in yeast cells both the monomeric and trimeric forms of full-length YadA were detected in mitochondria but only the trimeric species was fully integrated into the OM. The oligomeric form was exposed on the surface of the organelle in its native conformation and maintained its capacity to adhere to host cells. The co-expression of YadA with a mitochondria-targeted form of the bacterial periplasmic chaperone Skp, but not with SurA or SecB, resulted in enhanced levels of both forms of YadA. Taken together, these results indicate that the proper assembly of trimeric autotransporter can occur also in a system lacking the lipoproteins of the BAM machinery and is specifically enhanced by the chaperone Skp. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

  8. Site-directed mutants of 16S rRNA reveal important RNA domains for KsgA function and 30S subunit assembly.

    Science.gov (United States)

    Desai, Pooja M; Culver, Gloria M; Rife, Jason P

    2011-02-08

    KsgA is an rRNA methyltransferase important to the process of small subunit biogenesis in bacteria. It is ubiquitously found in all life including archaea and eukarya, where the enzyme is referred to as Dim1. Despite the emergence of considerable data addressing KsgA function over the last several years, details pertaining to RNA recognition are limited, in part because the most accessible substrate for in vitro studies of KsgA is the 900000 Da 30S ribosomal subunit. To overcome challenges imposed by size and complexity, we adapted recently reported techniques to construct in vivo assembled mutant 30S subunits suitable for use in in vitro methyltransferase assays. Using this approach, numerous 16S rRNA mutants were constructed and tested. Our observations indicate that the 790 loop of helix 24 plays an important role in overall catalysis by KsgA. Moreover, the length of helix 45 also is important to catalysis. In both cases loss of catalytic function occurred without an increase in the production of N(6)-methyladenosine, a likely indication that there was no critical reduction in binding strength. Both sets of observations support a "proximity" mechanism of KsgA function. We also report that several of the mutants constructed failed to assemble properly into 30S subunits, while some others did so with reduced efficiency. Therefore, the same technique of generating mutant 30S subunits can be used to study ribosome biogenesis on the whole.

  9. Site-directed mutants of 16S rRNA reveal important RNA domains for KsgA function and 30S subunit assembly

    Science.gov (United States)

    Desai, Pooja M.; Culver, Gloria M.; Rife, Jason P.

    2013-01-01

    KsgA is an rRNA methyltransferase important to the process of small subunit biogenesis in bacteria. It is ubiquitously found in all life including archaea and eukarya, where the enzyme is referred to as Dim1. Despite the emergence of considerable data addressing KsgA function over the last several years, details pertaining to RNA recognition are limited, in part because the most accessible substrate for in vitro studies of KsgA is the 900,000 Daltons 30S ribosomal subunit. To overcome challenges imposed by size and complexity we adapted recently reported techniques to construct in vivo assembled mutant 30S subunits suitable for use in in vitro methyltransferase assays. Using this approach, numerous 16S rRNA mutants were constructed and tested. Our observations indicate that the 790 loop of helix 24 plays an important role in overall catalysis by KsgA. Moreover, the length of helix 45 also is important to catalysis. In both cases loss of catalytic function occurred without an increase in the production of N6-methyladenosine, a likely indication that there was no critical reduction in binding strength. Both sets of observations support a ‘proximity’ mechanism of KsgA function. We also report that several of the mutants constructed failed to assemble properly into 30S subunits, while some others did so with reduced efficiency. Therefore, the same technique of generating mutant 30S subunits can be used to study ribosome biogenesis on the whole. PMID:21142019

  10. Properties of electrodeposited CoFe/Cu multilayers: The effect of Cu layer thickness

    Energy Technology Data Exchange (ETDEWEB)

    Sahin, Turgut, E-mail: stsahin4@hotmail.com [Deparment of Physics, Science and Literature Faculty, Balikesir University, 10100 Balikesir (Turkey); Kockar, Hakan, E-mail: hkockar@balikesir.edu.tr [Deparment of Physics, Science and Literature Faculty, Balikesir University, 10100 Balikesir (Turkey); Alper, Mursel, E-mail: malper@uludag.edu.tr [Deparment of Physics, Science and Literature Faculty, Uludag University, 16059 Gorukle, Bursa (Turkey)

    2015-01-01

    CoFe/Cu multilayers were potentiostatically electrodeposited on Ti substrates as a function of different non-magnetic (Cu) layer thicknesses, and their characterizations were investigated. The compositional analysis performed by energy dispersive X-ray spectroscopy disclosed that the Cu content in the multilayers increased and the Co content decreased as non-magnetic layer was increased. However, the Fe content was almost stable. The scanning electron microscopy studies showed that the surface morphology of the films is strongly affected by the non-magnetic layer thickness, and X-ray diffraction was used to analyse the structural properties of the multilayers and revealed that the multilayers have face-centred cubic (fcc) structure and their preferred orientations change depending on the Cu layer thickness. In the case of magnetoresistance measurements of the multilayers performed at room temperature, the highest giant magnetoresistance (GMR) values exhibited for the films with the Cu layer thickness (6.0 nm) whereas the lowest GMR magnitudes were observed for the films without Cu layer. Therefore, the variations of the Cu layer thicknesses were observed to have a significant effect on the GMR of multilayers. The differences observed in the magnetotransport properties were attributed to the microstructural changes caused by the Cu layer thickness. - Highlights: • CoFe/Cu multilayers were potentiostatically electrodeposited on Ti substrates. • Microstructural and magnetoresistance properties of CoFe/Cu multilayers were investigated. • All films had a face-centred cubic structure irrespective of the multilayer content. • All samples exhibited GMR and the maximum GMR value was 11%.

  11. Synthesis and photocatalytic property of multilayered Co{sub 3}O{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Dong En, E-mail: zdewxm@aliyun.com [Department of Chemical Engineering, Huaihai Institute of Technology, Lianyungang 222005 (China); Jiangsu Marine Resources Develepment Research Insititute, Lianyungang 222005 (China); School of Chemistry and Chemical Engineering, Nanjing University, 22 Hankou Road, Nanjing 210093 (China); Ren, Li Zheng; Hao, Xiao Yun; Pan, Bin Bin; Wang, Ming Yan; Ma, Juan Juan; Li, Feng [Department of Chemical Engineering, Huaihai Institute of Technology, Lianyungang 222005 (China); Li, Shu An [Jiangsu Marine Resources Develepment Research Insititute, Lianyungang 222005 (China); Tong, Zhi Wei [Department of Chemical Engineering, Huaihai Institute of Technology, Lianyungang 222005 (China)

    2015-11-15

    Highlights: • Multilayered Co{sub 3}O{sub 4} particles are synthesized from decomposition of multilayered Co{sub 2}(CO{sub 3})(OH){sub 2}. • The influences of solvent and probable growth mechanism are discussed. • The Co{sub 3}O{sub 4} particles exhibit good photocatalytic activity on degradation of MV. - Abstract: Co{sub 3}O{sub 4} multilayered structures were successfully synthesized by a facile poly (ethylene glycol 20000) (PEG-20000) assisted hydrothermal technique in combination with calcination method. The final Co{sub 3}O{sub 4} multilayered structures inherited perfectly the morphology of the preliminarily hydrothermal products. Experimental results obtained from the different growth stages demonstrate that the as-prepared precursor exhibit an interesting time-dependent evolution of building blocks, from urchin to multilayer. The possible formation mechanism for the hierarchical structures with various architectures is presented on account of the self-assembled growth induced by Ostwald ripening. Because of the unique structured composed of slices, the photocatalytic activity of the products was examined by measuring the photodecolourisation of methyl violet solution with ultraviolet radiation. The result shows that our products have a good photocatalytic activity.

  12. Modeling Delamination of Interfacial Corner Cracks in Multilayered Structures

    DEFF Research Database (Denmark)

    Veluri, Badrinath (Badri); Jensen, Henrik Myhre

    2013-01-01

    Multilayered electronic components, typically of heterogeneous materials, delaminate under thermal and mechanical loading. A phenomenological model focused on modeling the shape of such interface cracks close to corners in layered interconnect structures for calculating the critical stress...... for the calculation of fracture mechanical properties has been validated with threedimensional models for varying crack front shapes. A custom quantitative approach was formulated based on the finite element method with iterative adjustment of the crack front to estimate the critical delaminatio stress as a function...

  13. Electrically tunable plasma excitations in AA-stacking multilayer graphene

    OpenAIRE

    Lin, Ming-Fa; Chuang, Ying-Chih; Wu, Jhao-Ying

    2014-01-01

    We use a tight-binding model and the random-phase approximation to study the Coulomb excitations in simple-hexagonal-stacking multilayer graphene and discuss the field effects. The calculation results include the energy bands, the response functions, and the plasmon dispersions. A perpendicular electric field is predicted to induce significant charge transfer and thus capable of manipulating the energy, intensity, and the number of plasmon modes. This could be further validated by inelastic l...

  14. Functionalization at the central position of vinyl polymer chains: highly associable multipoint hydrogen bonds for complementary self-assemblies.

    Science.gov (United States)

    Lee, Sang-Ho; Ouchi, Makoto; Sawamoto, Mitsuo

    2014-02-01

    This paper deals with the precision introduction of a multiple hydrogen-bonding site of a high association constant at the central position of a vinyl polymer chain for complementary self-assemblies. The interactive site consists of an array of hydrogen donors (D) and acceptors (A) to induce a multiple and highly associable interaction with a complementary counterpart. A bifunctional initiator (Cl-DADDAD-Cl) for metal-catalyzed living radical polymerization is thus designed and synthesized to embed a "Hamilton receptor" (DADDAD) between two terminal chlorides (Cl). In the presence of a ruthenium complex, the dichloride gives controlled polymers (Cl∼∼∼DADDAD∼∼∼Cl, ∼ ∼ ∼: polymer backbone) of narrow molecular weight distributions (Mw/Mn MMA). The receptor-decorated polystyrene recognizes complementary associable molecules and polymers carrying an ADADA unit (ADADA-Anthracene and ADADA-PMMA) to form self-assemblies where the association constant is as high as K(ass) ≈ 8000 m(-1). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Multi-Layer Traffic Steering

    DEFF Research Database (Denmark)

    Fotiadis, Panagiotis; Polignano, Michele; Gimenez, Lucas Chavarria

    2013-01-01

    This paper investigates the potentials of traffic steering in the Radio Resource Control (RRC) Idle state by evaluating the Absolute Priorities (AP) framework in a multilayer Long Term Evolution (LTE) macrocell scenario. Frequency priorities are broadcast on the system information and RRC Idle...... signaling. The priority adjustment is based on both the Composite Available Capacity (CAC) and the radio conditions of the candidate layers. Compared to broadcast AP, the proposed scheme achieves better load balancing performance and improves network capacity, given that the User Equipment (UE) inactivity...

  16. Triggered release of insulin from glucose-sensitive enzyme multilayer shells.

    Science.gov (United States)

    Qi, Wei; Yan, Xuehai; Fei, Jinbo; Wang, Anhe; Cui, Yue; Li, Junbai

    2009-05-01

    A glucose-sensitive multilayer shell, which was fabricated by the layer-by-layer (LbL) assembly method, can be used as a carrier for the encapsulation and controlled release of insulin. In the present report, glucose oxidase (GOD) and catalase (CAT) were assembled on insulin particles alternately via glutaraldehyde (GA) cross-linking. The resulting core-shell system has been proven to be glucose-sensitive. When the external glucose was introduced, the release ratio of insulin from the protein multilayer can be increased observably. This is likely attributed to the catalysis interaction of CAT/GOD shells to glucose, which leads to the production of H(+) and thus drops the pH of the microenvironment. Under the acidic conditions, on the one hand, a part of C=N bond formed from Schiff base reaction can be broken and thus increasing the permeability of the capsule wall. On the other hand, the solubility of insulin can also be increased. The above factors may be the key control to increase the release of insulin from the multilayer. Therefore, such CAT/GOD multilayer may have a great potential as a glucose-sensitive release carrier for insulin, and may open the way for the further application of LbL capsules in the drug delivery and controlled release, etc.

  17. Diffusion phenomena in chemically stabilized multilayer structures

    NARCIS (Netherlands)

    Bruijn, S.; Bruijn, Saskia

    2011-01-01

    Multilayered thin film structures are widely applied as reflective coatings for optical elements in t