WorldWideScience

Sample records for hydrophobic ion interactions

  1. Specific ion effects on the hydrophobic interaction of benzene self-assembled monolayers

    DEFF Research Database (Denmark)

    Dobberschütz, Sören; Pedersen, Morten Rimmen; Hassenkam, Tue

    2015-01-01

    The interaction of aromatic compounds with various ions in aqueous solutions plays a role in a number of fields, as diverse as protein folding and enhanced oil recovery, among others. Therefore, we have investigated the effect of the four electrolytes, KCl, NaCl, MgCl2 and CaCl2, on the hydrophobic...

  2. Hydrophobic interactions and chemical reactivity

    NARCIS (Netherlands)

    Otto, Sijbren; Engberts, Jan B.F.N.

    2003-01-01

    This perspective describes how kinetic studies of organic reactions can be used to increase our understanding of hydrophobic interactions. In turn, our understanding of hydrophobic interactions can be used as a tool to influence chemical reactions.

  3. Water on hydrophobic surfaces: Mechanistic modeling of hydrophobic interaction chromatography.

    Science.gov (United States)

    Wang, Gang; Hahn, Tobias; Hubbuch, Jürgen

    2016-09-23

    Mechanistic models are successfully used for protein purification process development as shown for ion-exchange column chromatography (IEX). Modeling and simulation of hydrophobic interaction chromatography (HIC) in the column mode has been seldom reported. As a combination of these two techniques is often encountered in biopharmaceutical purification steps, accurate modeling of protein adsorption in HIC is a core issue for applying holistic model-based process development, especially in the light of the Quality by Design (QbD) approach. In this work, a new mechanistic isotherm model for HIC is derived by consideration of an equilibrium between well-ordered water molecules and bulk-like ordered water molecules on the hydrophobic surfaces of protein and ligand. The model's capability of describing column chromatography experiments is demonstrated with glucose oxidase, bovine serum albumin (BSA), and lysozyme on Capto™ Phenyl (high sub) as model system. After model calibration from chromatograms of bind-and-elute experiments, results were validated with batch isotherms and prediction of further gradient elution chromatograms. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Use of ion-exchange chromatography and hydrophobic interaction chromatography in the preparation and recovery of polyethylene glycol-linked proteins.

    Science.gov (United States)

    Seely, J E; Richey, C W

    2001-01-26

    Cation- and anion-exchange chromatography can be used to purify a polyethylene glycol-linked protein dimer (PEG dimer) made with M, 20 000 PEG bis-vinylsulfone, even when there are no net charge differences between the components that are being separated. The retention time on ion-exchange generally is inversely proportional to the PEG:protein ratio (on a mass basis). One of the biggest challenges in developing the process for making this PEG dimer was the quality of the PEG linker. Reversed-phase HPLC can be used to determine both size heterogeneity and the degree of end-group activation of Mr 20 000 PEG bis-vinylsulfone. In addition, we have found that hydrophobic interaction chromatography can be used make more size homogeneous preparations of Mr 20000 PEG bis-vinylsulfone, which significantly increased the recovery of the PEG dimer.

  5. Recovery of infective virus particles in ion-exchange and hydrophobic interaction monolith chromatography is influenced by particle charge and total-to-infective particle ratio.

    Science.gov (United States)

    Sviben, Dora; Forcic, Dubravko; Ivancic-Jelecki, Jelena; Halassy, Beata; Brgles, Marija

    2017-06-01

    Viral particles are used in medical applications as vaccines or gene therapy vectors. In order to obtain product of high purity, potency and safety for medical use purification of virus particles is a prerequisite, and chromatography is gaining increased attention to meet this aim. Here, we report on the use of ion-exchange and hydrophobic interaction chromatography on monolithic columns for purification of mumps virus (MuV) and measles virus (MeV). Efficiency of the process was monitored by quantification of infective virus particles (by 50% cell culture infective dose assay) and total virus particles, and monitoring of their size (by Nanoparticle Tracking Analysis). Ion-exchange chromatography was shown to be inefficient for MuV and best results for MeV were obtained on QA column with recovery around 17%. Purification of MuV and MeV by hydrophobic interaction chromatography resulted in recoveries around 60%. Results showed that columns with small channels (d=1.4μm) are not suitable for MuV and MeV, although their size is below 400nm, whereas columns with large channels (6μm) showed to be efficient and recoveries independent on the flow rate up to 10mL/min. Heterogeneity of the virus suspension and its interday variability mostly regarding total-to-infective particle ratio was observed. Interestingly, a trend in recovery depending on the day of the harvest was also observed for both viruses, and it correlated with the total-to-infective particle ratio, indicating influence of the virus sample composition on the chromatography results. Copyright © 2017. Published by Elsevier B.V.

  6. Predicting hot spots in protein interfaces based on protrusion index, pseudo hydrophobicity and electron-ion interaction pseudopotential features.

    Science.gov (United States)

    Xia, Junfeng; Yue, Zhenyu; Di, Yunqiang; Zhu, Xiaolei; Zheng, Chun-Hou

    2016-04-05

    The identification of hot spots, a small subset of protein interfaces that accounts for the majority of binding free energy, is becoming more important for the research of drug design and cancer development. Based on our previous methods (APIS and KFC2), here we proposed a novel hot spot prediction method. For each hot spot residue, we firstly constructed a wide variety of 108 sequence, structural, and neighborhood features to characterize potential hot spot residues, including conventional ones and new one (pseudo hydrophobicity) exploited in this study. We then selected 3 top-ranking features that contribute the most in the classification by a two-step feature selection process consisting of minimal-redundancy-maximal-relevance algorithm and an exhaustive search method. We used support vector machines to build our final prediction model. When testing our model on an independent test set, our method showed the highest F1-score of 0.70 and MCC of 0.46 comparing with the existing state-of-the-art hot spot prediction methods. Our results indicate that these features are more effective than the conventional features considered previously, and that the combination of our and traditional features may support the creation of a discriminative feature set for efficient prediction of hot spots in protein interfaces.

  7. Three dimensional liquid chromatography coupling ion exchange chromatography/hydrophobic interaction chromatography/reverse phase chromatography for effective protein separation in top-down proteomics.

    Science.gov (United States)

    Valeja, Santosh G; Xiu, Lichen; Gregorich, Zachery R; Guner, Huseyin; Jin, Song; Ge, Ying

    2015-01-01

    To address the complexity of the proteome in mass spectrometry (MS)-based top-down proteomics, multidimensional liquid chromatography (MDLC) strategies that can effectively separate proteins with high resolution and automation are highly desirable. Although various MDLC methods that can effectively separate peptides from protein digests exist, very few MDLC strategies, primarily consisting of 2DLC, are available for intact protein separation, which is insufficient to address the complexity of the proteome. We recently demonstrated that hydrophobic interaction chromatography (HIC) utilizing a MS-compatible salt can provide high resolution separation of intact proteins for top-down proteomics. Herein, we have developed a novel 3DLC strategy by coupling HIC with ion exchange chromatography (IEC) and reverse phase chromatography (RPC) for intact protein separation. We demonstrated that a 3D (IEC-HIC-RPC) approach greatly outperformed the conventional 2D IEC-RPC approach. For the same IEC fraction (out of 35 fractions) from a crude HEK 293 cell lysate, a total of 640 proteins were identified in the 3D approach (corresponding to 201 nonredundant proteins) as compared to 47 in the 2D approach, whereas simply prolonging the gradients in RPC in the 2D approach only led to minimal improvement in protein separation and identifications. Therefore, this novel 3DLC method has great potential for effective separation of intact proteins to achieve deep proteome coverage in top-down proteomics.

  8. Hydrophobic Interactions Involved in Attachment of a Baculovirus to Hydrophobic Surfaces

    OpenAIRE

    Small, Deirdre A.; Moore, Norman F.; Entwistle, Philip F.

    1986-01-01

    The hydrophobic interactions of Trichoplusia ni nuclear polyhedrosis virus were characterized by hydrophobic interaction chromatography. The determination of the hydrophobic force and some of the factors that influence its size is discussed in relation to the attachment to leaf surfaces of polyhedra during their use as biological control agents against insect pests.

  9. Hydrophobic interactions of sucralose with protein structures.

    Science.gov (United States)

    Shukla, Nimesh; Pomarico, Enrico; Hecht, Cody J S; Taylor, Erika A; Chergui, Majed; Othon, Christina M

    2018-02-01

    Sucralose is a commonly employed artificial sweetener that appears to destabilize protein native structures. This is in direct contrast to the bio-preservative nature of its natural counterpart, sucrose, which enhances the stability of biomolecules against environmental stress. We have further explored the molecular interactions of sucralose as compared to sucrose to illuminate the origin of the differences in their bio-preservative efficacy. We show that the mode of interactions of sucralose and sucrose in bulk solution differ subtly through the use of hydration dynamics measurement and computational simulation. Sucralose does not appear to disturb the native state of proteins for moderate concentrations (sucralose appears to differ in its interactions with protein leading to the reduction of native state stability. This difference in interaction appears weak. We explored the difference in the preferential exclusion model using time-resolved spectroscopic techniques and observed that both molecules appear to be effective reducers of bulk hydration dynamics. However, the chlorination of sucralose appears to slightly enhance the hydrophobicity of the molecule, which reduces the preferential exclusion of sucralose from the protein-water interface. The weak interaction of sucralose with hydrophobic pockets on the protein surface differs from the behavior of sucrose. We experimentally followed up upon the extent of this weak interaction using isothermal titration calorimetry (ITC) measurements. We propose this as a possible origin for the difference in their bio-preservative properties. Copyright © 2017 Elsevier Inc. All rights reserved.

  10. Hydrophobic interactions increase attachment of gum Arabic- and PVP-coated Ag nanoparticles to hydrophobic surfaces.

    Science.gov (United States)

    Song, Jee Eun; Phenrat, Tanapon; Marinakos, Stella; Xiao, Yao; Liu, Jie; Wiesner, Mark R; Tilton, Robert D; Lowry, Gregory V

    2011-07-15

    A fundamental understanding of attachment of surface-coated nanoparticles (NPs) is essential to predict the distribution and potential risks of NPs in the environment. Column deposition studies were used to examine the effect of surface-coating hydrophobicity on NP attachment to collector surfaces in mixtures with varying ratios of octadecylichlorosilane (OTS)-coated (hydrophobic) glass beads and clean silica (hydrophilic) glass beads. Silver nanoparticles (AgNPs) coated with organic coatings of varying hydrophobicity, including citrate, polyvinylpyrrolidone (PVP), and gum arabic (GA), were used. The attachment efficiencies of GA and PVP AgNPs increased by 2- and 4-fold, respectively, for OTS-coated glass beads compared to clean glass beads. Citrate AgNPs showed no substantial change in attachment efficiency for hydrophobic compared to hydrophilic surfaces. The attachment efficiency of PVP-, GA-, and citrate-coated AgNPs to hydrophobic collector surfaces correlated with the relative hydrophobicity of the coatings. The differences in the observed attachment efficiencies among AgNPs could not be explained by classical DLVO, suggesting that hydrophobic interactions between AgNPs and OTS-coated glass beads were responsible for the increase in attachment of surface-coated AgNPs with greater hydrophobicity. This study indicates that the overall attachment efficiency of AgNPs will be influenced by the hydrophobicity of the NP coating and the fraction of hydrophobic surfaces in the environment.

  11. Hydrophobic interaction membrane chromatography for bioseparation and responsive polymer ligands involved

    Science.gov (United States)

    Chen, Jingling; Peng, Rong; Chen, Xiaonong

    2017-09-01

    Hydrophobic interaction chromatography (HIC) is a rapid growing bioseparation technique, which separates biomolecules, such as therapeutic proteins and antibodys, based on the reversible hydrophobic interaction between immobilized hydrophobic ligands on chromatographic resin spheres and non-polar regions of solute molecule. In this review, the fundamental concepts of HIC and the factors that may affect purification efficiency of HIC is summarized, followed by the comparison of HIC with affinity chromatography and ion-exchange chromatography. Hydrophobic interaction membrane chromatography (HIMC) combines the advantages of HIC and membrane process and has showed great potential in bioseparation. For better understanding of HIMC, this review presents an overview of two main concerns about HIMC, i.e. membrane materials and hydrophobic ligands. Specifically, cellulose fiber-based membrane substrate and environment-responsive ligands are emphasized.

  12. Selective discrimination of small hydrophobic biomolecules based on ion-current rectification in conically shaped nanochannel.

    Science.gov (United States)

    Guo, Zhijun; Wang, Jiahai; Wang, Erkang

    2012-01-30

    In this study, based on ion-current rectification in the conically shaped nanochannel embedded in polyethylene terephthalate (PET) membrane, we have selectively discriminated three small biomolecules. Because three positive biomolecules (Hoechst 33342, Propidium and Bupivacaine) have different hydrophobicities, their interactions with inside wall of the conical nanochannel are different and their binding affinities can be derived from Langmuir absorption model. Therefore, we can successfully discriminate these small biomolecules. The highest binding constant was obtained for the small molecule with highest hydrophobicity. Another interesting result is that the detection limit for the small molecule with the highest binding constant shifts to submicromole. Copyright © 2011 Elsevier B.V. All rights reserved.

  13. Competition of electrostatic and hydrophobic interactions between small hydrophobes and model enclosures.

    Science.gov (United States)

    Wang, Lingle; Friesner, Richard A; Berne, B J

    2010-06-03

    The binding affinity between a probe hydrophobic particle and model hydrophobic plates with different charge (or dipole) densities in water was investigated through molecular dynamics simulation free-energy perturbation calculations. We observed a reduced binding affinity when the plates are charged, in agreement with previous findings. With increased charge density, the plates can change from "hydrophobic like" (pulling the particle into the interplate region) to "hydrophilic like" (ejecting the particle out of the interplate region), demonstrating the competition between hydrophobic and electrostatic interactions. The reduction of the binding affinity is quadratically dependent on the magnitude of the charge for symmetric systems, but linear and cubic terms also make a contribution for asymmetric systems. Statistical perturbation theory explains these results and shows when and why implicit solvent models fail.

  14. Inverse colloidal crystal membranes for hydrophobic interaction membrane chromatography.

    Science.gov (United States)

    Vu, Anh T; Wang, Xinying; Wickramasinghe, S Ranil; Yu, Bing; Yuan, Hua; Cong, Hailin; Luo, Yongli; Tang, Jianguo

    2015-08-01

    Hydrophobic interaction membrane chromatography has gained interest due to its excellent performance in the purification of humanized monoclonal antibodies. The membrane material used in hydrophobic interaction membrane chromatography has typically been commercially available polyvinylidene fluoride. In this contribution, newly developed inverse colloidal crystal membranes that have uniform pores, high porosity and, therefore, high surface area for protein binding are used as hydrophobic interaction membrane chromatography membranes for humanized monoclonal antibody immunoglobulin G purification. The capacity of the inverse colloidal crystal membranes developed here is up to ten times greater than commercially available polyvinylidene fluoride membranes with a similar pore size. This work highlights the importance of developing uniform pore size high porosity membranes in order to maximize the capacity of hydrophobic interaction membrane chromatography. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Thermodynamics of hydrophobic interaction between silica surfaces coated with octadecyltrichlorosilane.

    Science.gov (United States)

    Li, Zuoli; Yoon, Roe-Hoan

    2013-02-15

    Surface force measurements conducted with thiolated gold surfaces showed previously that hydrophobic interaction entails a decrease in excess film entropy, suggesting that hydrophobic force originates from changes in the structure of the medium (water) confined between hydrophobic surfaces. As a follow-up work, surface force measurements have been conducted in the present work using an atomic force microscope (AFM) with silica surfaces coated with octadecyltrichlorosilane (OTS) at temperatures in the range of 10-40°C. A thermodynamic analysis of the results show that both the excess film entropy (ΔS(f)) and excess film enthalpy (ΔH(f)) decrease with decreasing thickness of the water films between the hydrophobic surfaces. It has been found also that |ΔH(f)|>|TΔS(f)|, which represents a necessary condition for the excess free energy change (ΔG(f)) to be negative and hence the hydrophobic interaction be attractive. Thus, the results obtained with both the thiolated and silylated surfaces show that hydrophobic forces originate from the structural changes in the medium. It is believed that the water molecules in the thin liquid films (TLFs) of water form clusters as a means to reduce the free energy when they cannot form H-bonds to neighboring hydrophobic surfaces. Copyright © 2012 Elsevier Inc. All rights reserved.

  16. Interaction mechanism between hydrophobic and hydrophilic surfaces: using polystyrene and mica as a model system.

    Science.gov (United States)

    Faghihnejad, Ali; Zeng, Hongbo

    2013-10-08

    The interactions between hydrophobic and hydrophilic molecules, particles, or surfaces occur in many biological phenomena and industrial processes. In this work, polystyrene (PS) and mica were chosen as a model system to investigate the interaction mechanism between hydrophilic and hydrophobic surfaces. Using a surface forces apparatus (SFA) coupled with a top-view optical microscope, interaction forces between PS and mica surfaces were directly probed in five different electrolyte solutions (i.e., NaCl, CaCl2, NaOH, HCl, and CH3COOH) of various concentrations. Long-range repulsion was observed in low electrolyte concentration (e.g., 0.001 M) which was mainly due to the presence of microscopic and submicroscopic bubbles on PS surface. A modified Derjaguin-Landau-Verwey-Overbeek (DLVO) theory well fits the interaction forces by taking into account the effect of bubbles on PS surface. The range of the repulsion was dramatically reduced in 1.0 M solutions of NaCl, CaCl2, and NaOH but did not significantly change in 1.0 M HCl and CH3COOH, which was due to ion specificity effect on the formation and stability of bubbles on PS surface. The range of repulsion was also significantly reduced to hydrophobic attraction of the untreated PS-PS system to pure repulsion between untreated PS and treated PS, demonstrating the important role of surface hydrophobicity on the formation and stability of bubbles on substrates. Our results indicate that DLVO forces dominate the interaction between hydrophilic surface (i.e., mica) and hydrophobic polymer (i.e., PS), while the types of electrolytes (ion specificity), electrolyte concentration, degassing, and surface hydrophobicity can significantly affect the formation and stability of bubbles on the interacting surfaces, thus affecting the range and magnitude of the interaction forces.

  17. Compositional fingerprint of soy sauces via hydrophobic surface interaction.

    Science.gov (United States)

    Jakobi, Victoria; Salmen, Paul; Paulus, Michael; Tolan, Metin; Rosenhahn, Axel

    2017-03-01

    In this work, the interaction of soy sauces with hydrophobic surfaces has been analyzed. Hydrophobic self-assembled monolayers on gold or silicon dioxide were used to harvest conditioning layers from soy sauce products with varying amounts of additives. The data was compared to adsorption of soy protein and glutamic acid as common ingredients. Spectral ellipsometry revealed that all tested sauces led to the formation of thin overlayers on hydrophobic surfaces. Products with less additives yielded adlayers in the same thickness range as pure soy protein. In contrast, sauces with more ingredients create distinctly thicker films. Using water contact angle goniometry, it is shown that all adlayers render the substrate more hydrophilic. Infrared spectroscopy provided a deeper insight into the adlayer chemistry and revealed that the adlayer composition is dominated by protein rich components. X-ray reflectivity on selected films provided further insight into the density profiles within the adlayers on the molecular scale. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. The Structure and Transport of Water and Hydrated Ions Within Hydrophobic, Nanoscale Channels

    Energy Technology Data Exchange (ETDEWEB)

    Holt, J K; Herberg, J L; Wu, Y; Schwegler, E; Mehta, A

    2009-06-15

    The purpose of this project includes an experimental and modeling investigation into water and hydrated ion structure and transport at nanomaterials interfaces. This is a topic relevant to understanding the function of many biological systems such as aquaporins that efficiently shuttle water and ion channels that permit selective transport of specific ions across cell membranes. Carbon nanotubes (CNT) are model nanoscale, hydrophobic channels that can be functionalized, making them artificial analogs for these biological channels. This project investigates the microscopic properties of water such as water density distributions and dynamics within CNTs using Nuclear Magnetic Resonance (NMR) and the structure of hydrated ions at CNT interfaces via X-ray Absorption Spectroscopy (XAS). Another component of this work is molecular simulation, which can predict experimental measurables such as the proton relaxation times, chemical shifts, and can compute the electronic structure of CNTs. Some of the fundamental questions this work is addressing are: (1) what is the length scale below which nanoscale effects such as molecular ordering become important, (2) is there a relationship between molecular ordering and transport?, and (3) how do ions interact with CNT interfaces? These are questions of interest to the scientific community, but they also impact the future generation of sensors, filters, and other devices that operate on the nanometer length scale. To enable some of the proposed applications of CNTs as ion filtration media and electrolytic supercapacitors, a detailed knowledge of water and ion structure at CNT interfaces is critical.

  19. Microphase Separation in Oil-Water Mixtures Containing Hydrophilic and Hydrophobic Ions

    Science.gov (United States)

    Tasios, Nikos; Samin, Sela; van Roij, René; Dijkstra, Marjolein

    2017-11-01

    We develop a lattice-based Monte Carlo simulation method for charged mixtures capable of treating dielectric heterogeneities. Using this method, we study oil-water mixtures containing an antagonistic salt, with hydrophilic cations and hydrophobic anions. Our simulations reveal several phases with a spatially modulated solvent composition, in which the ions partition between water-rich and water-poor regions according to their affinity. In addition to the recently observed lamellar phase, we find tubular and droplet phases, reminiscent of those found in block copolymers and surfactant systems. Interestingly, these structures stem from ion-mediated interactions, which allows for tuning of the phase behavior via the concentrations, the ionic properties, and the temperature.

  20. Interaction of hydrophobic polymers with model lipid bilayers.

    Science.gov (United States)

    Bochicchio, D; Panizon, E; Monticelli, L; Rossi, G

    2017-07-25

    The interaction of nanoscale synthetic materials with cell membranes is one of the key steps determining nanomaterials' toxicity. Here we use molecular simulations, with atomistic and coarse-grained resolution, to investigate the interaction of three hydrophobic polymers with model lipid membranes. Polymer nanoparticles made of polyethylene (PE), polypropylene (PP) and polystyrene with size up to 7 nm enter easily POPC lipid membranes, localizing to the membrane hydrophobic core. For all three materials, solid polymeric nanoparticles become essentially liquid within the membrane at room temperature. Still, their behavior in the membrane core is not the same: PP and PS disperse in the core of the bilayer, while PE shows a tendency to aggregate. We also examined the interaction of the polymers with heterogeneous membranes, consisting of a ternary lipid mixture exhibiting liquid-ordered/liquid-disordered phase separation. The behavior of the three polymers is markedly different: PP disfavors lipid phase separation, PS stabilizes it, and PE modifies the topology of the phase boundaries and causes cholesterol depletion from the liquid ordered phase. Our results show that different hydrophobic polymers have major effects on the properties of lipid membranes, calling for further investigations on model systems and cell membranes.

  1. Structures of multidomain proteins adsorbed on hydrophobic interaction chromatography surfaces.

    Science.gov (United States)

    Gospodarek, Adrian M; Sun, Weitong; O'Connell, John P; Fernandez, Erik J

    2014-12-05

    In hydrophobic interaction chromatography (HIC), interactions between buried hydrophobic residues and HIC surfaces can cause conformational changes that interfere with separations and cause yield losses. This paper extends our previous investigations of protein unfolding in HIC chromatography by identifying protein structures on HIC surfaces under denaturing conditions and relating them to solution behavior. The thermal unfolding of three model multidomain proteins on three HIC surfaces of differing hydrophobicities was investigated with hydrogen exchange mass spectrometry (HXMS). The data were analyzed to obtain unfolding rates and Gibbs free energies for unfolding of adsorbed proteins. The melting temperatures of the proteins were lowered, but by different amounts, on the different surfaces. In addition, the structures of the proteins on the chromatographic surfaces were similar to the partially unfolded structures produced in the absence of a surface by temperature as well as by chemical denaturants. Finally, it was found that patterns of residue exposure to solvent on different surfaces at different temperatures can be largely superimposed. These findings suggest that protein unfolding on various HIC surfaces might be quantitatively related to protein unfolding in solution and that details of surface unfolding behavior might be generalized. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. Nisin adsorption on hydrophilic and hydrophobic surfaces: evidence of its interactions and antibacterial activity.

    Science.gov (United States)

    Karam, Layal; Jama, Charafeddine; Nuns, Nicolas; Mamede, Anne-Sophie; Dhulster, Pascal; Chihib, Nour-Eddine

    2013-06-01

    Study of peptides adsorption on surfaces remains a current challenge in literature. A complementary approach, combining X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to investigate the antimicrobial peptide nisin adsorption on hydrophilic and hydrophobic surfaces. The native low density polyethylene was used as hydrophobic support and it was grafted with acrylic acid to render it hydrophilic. XPS permitted to confirm nisin adsorption and to determine its amount on the surfaces. ToF-SIMS permitted to identify the adsorbed bacteriocin type and to observe its distribution and orientation behavior on both types of surfaces. Nisin was more oriented by its hydrophobic side to the hydrophobic substrate and by its hydrophilic side to the outer layers of the adsorbed peptide, in contrast to what was observed on the hydrophilic substrate. A correlation was found between XPS and ToF-SIMS results, the types of interactions on both surfaces and the observed antibacterial activity. Such interfacial studies are crucial for better understanding the peptides interactions and adsorption on surfaces and must be considered when setting up antimicrobial surfaces. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.

  3. Phenylalanine functionalized zwitterionic monolith for hydrophobic interaction electrochromatography.

    Science.gov (United States)

    Wang, Jiabin; Jia, Wenchao; Lin, Xucong; Wu, Xiaoping; Xie, Zenghong

    2013-12-01

    A novel phenylalanine (Phe) functionalized zwitterionic monolith for hydrophobic electrochromatography was prepared by a two-step procedure involving the synthesis of glycidyl methacrylate based polymer monolith and subsequent on-column chemical modification with Phe via ring-opening reaction of epoxides. Benefitting from the hydrophobicity of both methacrylate-based matrix and aromatic group of Phe, this monolith could exhibit good hydrophobic interaction for the separation. Typical RP chromatographic behavior was observed toward various solutes. The well-controlled cathodic or anodic EOF of the prepared column could be facilely switched by altering the pH values of running buffers. The separation mechanism of this Phe functionalized zwitterionic monolith is discussed in detail. Two mixed-mode mechanisms of RP/cation exchange and RP/anion exchange could be further realized on the same monolith in different pH condition of the mobile phase. Versatile separation capabilities of neutral, basic, and acidic analytes have been successfully achieved in this zwitterionic monolith by CEC method. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Protein interactions in hydrophobic charge induction chromatography (HCIC).

    Science.gov (United States)

    Ghose, Sanchayita; Hubbard, Brian; Cramer, Steven M

    2005-01-01

    A quantitative understanding of how proteins interact with hydrophobic charge induction chromatographic resins is provided. Selectivity on this mode of chromatography for monoclonal antibodies as compared to other model proteins is probed by means of a linear retention vs pH plot. The pH-dependent adsorption behavior on this mode of chromatography for a hydrophobic, charged solute is described by taking into account the equilibrium between a hydrophobic, charged solute and an ionizable, heterocyclic ligand. By analogy, an equation that is seen to adequately describe macromolecular retention under linear conditions over a range of pH is developed. A preparative, nonlinear isotherm that can capture both pH and salt concentration dependency for proteins is proposed by using an exponentially modified Langmuir isotherm model. This model is seen to successfully simulate adsorption isotherms for a variety of proteins over a range of pHs and mobile phase salt concentrations. Finally, the widely differing retention characteristics of two monoclonal antibodies are used to derive two different strategies for improving separations on this mode of chromatography. A better understanding of protein binding to this class of resins is seen as an important step to future exploitation of this mode of chromatography for industrial scale purification of proteins.

  5. Water interaction with hydrophobic and hydrophilic soot particles.

    Science.gov (United States)

    Popovicheva, Olga; Persiantseva, Natalia M; Shonija, Natalia K; DeMott, Paul; Koehler, Kirsten; Petters, Markus; Kreidenweis, Sonia; Tishkova, Victoria; Demirdjian, Benjamin; Suzanne, Jean

    2008-05-07

    The interaction of water with laboratory soots possessing a range of properties relevant for atmospheric studies is examined by two complementary methods: gravimetrical measurement of water uptake coupled with chemical composition and porosity analysis and HTDMA (humidified tandem differential mobility analyzer) inference of water uptake accompanied by separate TEM (transmission electron microscopy) analysis of single particles. The first method clarifies the mechanism of water uptake for bulk soot and allows the classification of soot with respect to its hygroscopicity. The second method highlights the dependence of the soot aerosol growth factor on relative humidity (RH) for quasi-monodisperse particles. Hydrophobic and hydrophilic soot are qualitatively defined by their water uptake and surface polarity: laboratory soot particles are thus classified from very hydrophobic to very hydrophilic. Thermal soot particles produced from natural gas combustion are classified as hydrophobic with a surface of low polarity since water is found to cover only half of the surface. Graphitized thermal soot particles are proposed for comparison as extremely hydrophobic and of very low surface polarity. Soot particles produced from laboratory flame of TC1 aviation kerosene are less hydrophobic, with their entire surface being available for statistical monolayer water coverage at RH approximately 10%. Porosity measurements suggest that, initially, much of this surface water resides within micropores. Consequently, the growth factor increase of these particles to 1.07 at RH > 80% is attributed to irreversible swelling that accompanies water uptake. Hysteresis of adsorption/desorption cycles strongly supports this conclusion. In contrast, aircraft engine soot, produced from burning TC1 kerosene in a gas turbine engine combustor, has an extremely hydrophilic surface of high polarity. Due to the presence of water soluble organic and inorganic material it can be covered by many water

  6. Water-Mediated Interactions between Hydrophilic and Hydrophobic Surfaces.

    Science.gov (United States)

    Kanduč, Matej; Schlaich, Alexander; Schneck, Emanuel; Netz, Roland R

    2016-09-06

    All surfaces in water experience at short separations hydration repulsion or hydrophobic attraction, depending on the surface polarity. These interactions dominate the more long-ranged electrostatic and van der Waals interactions and are ubiquitous in biological and colloidal systems. Despite their importance in all scenarios where the surface separation is in the nanometer range, the origin of these hydration interactions is still unclear. Using atomistic solvent-explicit molecular dynamics simulations, we analyze the interaction free energies of charge-neutral model surfaces with different elastic and water-binding properties. The surface polarity is shown to be the most important parameter that not only determines the hydration properties and thereby the water contact angle of a single surface but also the surface-surface interaction and whether two surfaces attract or repel. Elastic properties of the surfaces are less important. On the basis of surface contact angles and surface-surface binding affinities, we construct a universal interaction diagram featuring three different interaction regimes-hydration repulsion, cavitation-induced attraction-and for intermediate surface polarities-dry adhesion. On the basis of scaling arguments and perturbation theory, we establish simple combination rules that predict the interaction behavior for combinations of dissimilar surfaces.

  7. Hydrophobic interactions within biofilms of nitrifying and denitrifying bacteria in biofilters

    Energy Technology Data Exchange (ETDEWEB)

    Kim, I.S.; Stabnikova, E.V.; Ivanov, V.N. [Kwangju Inst. of Science and Technology (Korea). Dept. of Environmental Science and Engineering

    2000-04-01

    Hydrophobicity of the solid surface and microbial cell surface is important factor for the development of biofilms applied in bioengineering systems. An adsorption of phenanthrene was used for analysis of the hydrophobicity of support fibers and bacterial cell surfaces within the biofilter of wastewater. The adsorption of phenanthrene was measured by synchronous fluorescence spectrometry. Cell surface hydrophobicity does not depend on the fixation procedure, pH of microbial suspension, and has no clear correlation with an adherence of the cells to hexadecane droplets. Notwithstanding high hydrophobicity of bacterial cells, the hydrophobicity of intact biofilm is determined by the hydrophobicity of the support fibers. New indexes were proposed to evaluate the reactor performance related with hydrophobic interactions within the biofilm. These indexes showed that significant share of hydrophobic sites within the nitrifying biofilm is protected from the hydrophobic interactions between the cells and environment. (orig.)

  8. Purification of monoclonal antibodies by hydrophobic interaction chromatography under no-salt conditions.

    Science.gov (United States)

    Ghose, Sanchayita; Tao, Yinying; Conley, Lynn; Cecchini, Douglas

    2013-01-01

    Hydrophobic interaction chromatography (HIC) is commonly used as a polishing step in monoclonal antibody purification processes. HIC offers an orthogonal selectivity to ion exchange chromatography and can be an effective step for aggregate clearance and host cell protein reduction. HIC, however, suffers from the limitation of use of high concentrations of kosmotropic salts to achieve the desired separation. These salts often pose a disposal concern in manufacturing facilities and at times can cause precipitation of the product. Here, we report an unconventional way of operating HIC in the flowthrough (FT) mode with no kosmotropic salt in the mobile phase. A very hydrophobic resin is selected as the stationary phase and the pH of the mobile phase is modulated to achieve the required selectivity. Under the pH conditions tested (pH 6.0 and below), antibodies typically become positively charged, which has an effect on its polarity and overall surface hydrophobicity. Optimum pH conditions were chosen under which the antibody product of interest flowed through while impurities such as aggregates and host cell proteins bound to the column. This strategy was tested with a panel of antibodies with varying pI and surface hydrophobicity. Performance was comparable to that observed using conventional HIC conditions with high salt.

  9. Dewetting and hydrophobic interaction in physical and biological systems.

    Science.gov (United States)

    Berne, Bruce J; Weeks, John D; Zhou, Ruhong

    2009-01-01

    Hydrophobicity manifests itself differently on large and small length scales. This review focuses on large-length-scale hydrophobicity, particularly on dewetting at single hydrophobic surfaces and drying in regions bounded on two or more sides by hydrophobic surfaces. We review applicable theories, simulations, and experiments pertaining to large-scale hydrophobicity in physical and biomolecular systems and clarify some of the critical issues pertaining to this subject. Given space constraints, we cannot review all the significant and interesting work in this active field.

  10. Prediction of protein retention times in hydrophobic interaction chromatography by robust statistical characterization of their atomic-level surface properties.

    NARCIS (Netherlands)

    Hanke, A.T.; Klijn, M.E.; Verhaert, P.D.; Wielen, van der L.; Ottens, M.; Eppink, M.H.M.; Sandt, van de E.J.A.X.

    2016-01-01

    The correlation between the dimensionless retention times (DRT) of proteins in hydrophobic interaction chromatography (HIC) and their surface properties were investigated. A ternary atomic-level hydrophobicity scale was used to calculate the distribution of local average hydrophobicity across the

  11. Adhesive hydrophobicity of Cu2O nano-columnar arrays induced by nitrogen ion irradiation.

    Science.gov (United States)

    Dhal, Satyanarayan; Chatterjee, Sriparna; Manju, Unnikrishnan; Tribedi, Lokesh C; Thulasiram, K V; Fernandez, W A; Chatterjee, Shyamal

    2015-12-21

    Low energy nitrogen ions are used in this work to manipulate wetting properties of the surface of the array of Cu2O nano-columns, which yields remarkable results. The nano-columnar thin films were grown on a highly conductive silicon surface by a sputter deposition technique. The films were irradiated at two different fluences of 5 × 10(15) and 1 × 10(16) ions per cm(2), respectively. With increasing fluence the shape of column tip changes, columns are bent and porous channels between columns are clogged up. While the surface of the pristine sample is hydrophilic, the irradiated surface turns into hydrophobic but having adhesion properties. We have analysed the structural and chemical properties of the surface in detail to understand the initial and modified wetting properties. Furthermore, the temporal evolutions of different droplet parameters are investigated to realize the interactions between the water droplet, the sample surface and the atmosphere. We envisage that such modified surfaces can be beneficial for transport of a small volume of liquids with minimum loss and spectroscopic studies, where a small amount of water droplet is available for measurements.

  12. Hydrophobization of track membrane surface by ion-plasma sputtering method

    Science.gov (United States)

    Kuklin, I. E.; Khlebnikov, N. A.; Barashev, N. R.; Serkov, K. V.; Polyakov, E. V.; Zdorovets, M. V.; Borgekov, D. B.; Zhidkov, I. S.; Cholakh, S. O.; Kozlovskiy, A. L.

    2017-09-01

    This article reviews the possibility of applying inorganic coatings of metal compounds on PTM by ion-plasma sputtering. The main aim of this research is to increase the contact angle of PTM surfaces and to impart the properties of a hydrophobic material to it. After the modification, the initial contact angle increased from 70° to 120°.

  13. Hydrophobically modified polyelectrolytes : synthesis, properties and interactions with surfactants

    NARCIS (Netherlands)

    Nieuwkerk, A.C.

    1998-01-01

    Hydrophobically modified polyelectrolytes can form micelle-like aggregates, so-called microdomains, in aqueous solution. The hydrophobic side chains constitute the apolar inner part of these microdomains and the hydrophilic groups on the polyelectrolyte backbone are at the surface of the

  14. Naphthyl methacrylate-based monolithic column for RP-CEC via hydrophobic and pi interactions.

    Science.gov (United States)

    Karenga, Samuel; El Rassi, Ziad

    2010-03-01

    A neutral naphthyl methacrylate-based monolith (NMM) was introduced for RP-CEC of various aromatic compounds via hydrophobic and pi interactions. It was characterized over a wide range of elution conditions to gain insight into its RP retention mechanism toward the various solute probes under investigation. First, the NMM column exhibited cathodal EOF at various mobile phase compositions and pH suggesting that although the NMM column is void of fixed charges, it acquires a negative zeta potential. It is believed that the negative zeta potential is imparted by the adsorption of mobile phase ions to the NMM surface. The NMM column exhibited pi-pi interactions in addition to hydrophobic interactions due to the aromatic and nonpolar nature of its naphthyl ligands. In all cases, the retention of the various aromatic test solutes including PAHs, benzene derivatives, toluene derivatives, anilines and toluidine, tolunitrile and nitrotoluene positional isomers on the NMM column were compared to their retention on an octadecyl acrylate-based monolithic column. Not only were the values of the retention factors of the various solutes on the NMM column higher than those obtained on the octadecyl acrylate-based monolithic column under otherwise the same CEC conditions, but the elution orders were also different on both columns with a superior and unique selectivity exhibited by the NMM column.

  15. Potential hydrophobic interaction between two cysteines in interior hydrophobic region improves thermostability of a family 11 xylanase from Neocallimastix patriciarum.

    Science.gov (United States)

    You, Chun; Huang, Qiang; Xue, Huping; Xu, Yang; Lu, Hong

    2010-04-01

    In this study, we employed directed evolution and site-directed mutagenesis to screen thermostable mutants of a family 11 xylanase from Neocallimastix patriciarum, and found that the thermostability and specific activity are both enhanced when mutations (G201C and C60A) take place in the interior hydrophobic region of the enzyme. Far-ultraviolet circular dichroism analysis showed that the melting temperatures (T(m)) of the G201C and C60A-G201C mutants are higher than that of the wild type by about 10 and 12 degrees C, respectively. At 72 degrees C, their specific activities are about 4 and 6 times as that of the wild type, respectively. Homology modeling and site-directed mutagenesis demonstrated that the enhanced thermostability of the G201C and C60A-G201C mutants may be mainly attributed to a potential stronger hydrophobic interaction between the two well-packed cysteines at sites 50 and 201, rather than the disulfide bond formation which was ruled out by thiol titration with dithionitrobenzoic acid (DTNB). And the strength of such interaction depends on the packing of the side-chain and hydrophobicity of residues at these two sites. This suggests that cysteine could stabilize a protein not only by forming a disulfide bond, but also by the strong hydrophobicity itself. (c) 2009 Wiley Periodicals, Inc.

  16. Extended surfaces modulate hydrophobic interactions of neighboring solutes.

    Science.gov (United States)

    Patel, Amish J; Varilly, Patrick; Jamadagni, Sumanth N; Acharya, Hari; Garde, Shekhar; Chandler, David

    2011-10-25

    Interfaces are a most common motif in complex systems. To understand how the presence of interfaces affects hydrophobic phenomena, we use molecular simulations and theory to study hydration of solutes at interfaces. The solutes range in size from subnanometer to a few nanometers. The interfaces are self-assembled monolayers with a range of chemistries, from hydrophilic to hydrophobic. We show that the driving force for assembly in the vicinity of a hydrophobic surface is weaker than that in bulk water and decreases with increasing temperature, in contrast to that in the bulk. We explain these distinct features in terms of an interplay between interfacial fluctuations and excluded volume effects--the physics encoded in Lum-Chandler-Weeks theory [Lum K, Chandler D, Weeks JD (1999) J Phys Chem B 103:4570-4577]. Our results suggest a catalytic role for hydrophobic interfaces in the unfolding of proteins, for example, in the interior of chaperonins and in amyloid formation.

  17. Preparation of a weak anion exchange/hydrophobic interaction dual-function mixed-mode chromatography stationary phase for protein separation using click chemistry.

    Science.gov (United States)

    Zhao, Kailou; Yang, Fan; Xia, Hongjun; Wang, Fei; Song, Qingguo; Bai, Quan

    2015-03-01

    In this study, 3-diethylamino-1-propyne was covalently bonded to the azide-silica by a click reaction to obtain a novel dual-function mixed-mode chromatography stationary phase for protein separation with a ligand containing tertiary amine and two ethyl groups capable of electrostatic and hydrophobic interaction functionalities, which can display hydrophobic interaction chromatography character in a high-salt-concentration mobile phase and weak anion exchange character in a low-salt-concentration mobile phase employed for protein separation. As a result, it can be employed to separate proteins with weak anion exchange and hydrophobic interaction modes, respectively. The resolution and selectivity of the stationary phase were evaluated in both hydrophobic interaction and ion exchange modes with standard proteins, respectively, which can be comparable to that of conventional weak anion exchange and hydrophobic interaction chromatography columns. Therefore, the synthesized weak anion exchange/hydrophobic interaction dual-function mixed-mode chromatography column can be used to replace two corresponding conventional weak anion exchange and hydrophobic interaction chromatography columns to separate proteins. Based on this mixed-mode chromatography stationary phase, a new off-line two-dimensional liquid chromatography technology using only a single dual-function mixed-mode chromatography column was developed. Nine kinds of tested proteins can be separated completely using the developed method within 2.0 h. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Automated Hydrophobic Interaction Chromatography Column Selection for Use in Protein Purification

    Science.gov (United States)

    Murphy, Patrick J. M.; Stone, Orrin J.; Anderson, Michelle E.

    2011-01-01

    In contrast to other chromatographic methods for purifying proteins (e.g. gel filtration, affinity, and ion exchange), hydrophobic interaction chromatography (HIC) commonly requires experimental determination (referred to as screening or "scouting") in order to select the most suitable chromatographic medium for purifying a given protein 1. The method presented here describes an automated approach to scouting for an optimal HIC media to be used in protein purification. HIC separates proteins and other biomolecules from a crude lysate based on differences in hydrophobicity. Similar to affinity chromatography (AC) and ion exchange chromatography (IEX), HIC is capable of concentrating the protein of interest as it progresses through the chromatographic process. Proteins best suited for purification by HIC include those with hydrophobic surface regions and able to withstand exposure to salt concentrations in excess of 2 M ammonium sulfate ((NH4)2SO4). HIC is often chosen as a purification method for proteins lacking an affinity tag, and thus unsuitable for AC, and when IEX fails to provide adequate purification. Hydrophobic moieties on the protein surface temporarily bind to a nonpolar ligand coupled to an inert, immobile matrix. The interaction between protein and ligand are highly dependent on the salt concentration of the buffer flowing through the chromatography column, with high ionic concentrations strengthening the protein-ligand interaction and making the protein immobile (i.e. bound inside the column) 2. As salt concentrations decrease, the protein-ligand interaction dissipates, the protein again becomes mobile and elutes from the column. Several HIC media are commercially available in pre-packed columns, each containing one of several hydrophobic ligands (e.g. S-butyl, butyl, octyl, and phenyl) cross-linked at varying densities to agarose beads of a specific diameter 3. Automated column scouting allows for an efficient approach for determining which HIC media

  19. Hydrophobic and hydrophilic interactions in aqueous mixtures of alcohols at a hydrophobic surface.

    Science.gov (United States)

    Ballal, Deepti; Chapman, Walter G

    2013-09-21

    Aqueous solutions of alcohols are interesting because of their anomalous behavior that is believed to be due to the molecular structuring of water and alcohol around each other in solution. The interfacial structuring and properties are significant for application in alcohol purification processes and biomolecular structure. Here we study aqueous mixtures of short alcohols (methanol, ethanol, 1-propanol, and 2-propanol) at a hydrophobic surface using interfacial statistical associating fluid theory which is a perturbation density functional theory. The addition of a small amount of alcohol decreases the interfacial tension of water drastically. This trend in interfacial tension can be explained by the structure of water and alcohol next to the surface. The hydrophobic group of an added alcohol preferentially goes to the surface preserving the structure of water in the bulk. For a given bulk alcohol concentration, water mixed with the different alcohols has different interfacial tensions with propanol having a lower interfacial tension than methanol and ethanol. 2-propanol is not as effective in decreasing the interfacial tension as 1-propanol because it partitions poorly to the surface due to its larger excluded volume. But for a given surface alcohol mole fraction, all the alcohol mixtures give similar values for interfacial tension. For separation of alcohol from water, methods that take advantage of the high surface mole fraction of alcohol have advantages compared to separation using the vapor in equilibrium with a water-alcohol liquid.

  20. Ion Transfer Voltammetry Associated with Two Polarizable Interfaces Within Water and Moderately Hydrophobic Ionic Liquid Systems

    DEFF Research Database (Denmark)

    Gan, Shiyu; Zhou, Min; Zhang, Jingdong

    2013-01-01

    An electrochemical system composed of two polarizable interfaces (the metallic electrode|water and water|ionic liquid interfaces), namely two‐polarized‐interface (TPI) technique, has been proposed to explore the ion transfer processes between water and moderately hydrophobic ionic liquids (W......|mIL), typically 1‐octyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide (C8mimC1C1N) and 1‐hexyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide (C6mimC1C1N). Within the classic four‐electrode system, it is not likely that the ion transfer information at the W|mIL interface can be obtained due...... to an extremely narrow polarized potential window (ppw) caused by these moderately hydrophobic ionic components. In this article, we show that TPI technique has virtually eliminated the ppw limitation based on a controlling step of concentration polarization at the electrode|water interface. With the aid...

  1. Hydrophobic and Ionic-Interactions in Bulk and Confined Water with Implications for Collapse and Folding of Proteins

    Science.gov (United States)

    Vaitheeswaran, S.; Chen, Jie; Thirumalai, D.

    2011-10-01

    Water and water-mediated interactions determine the thermodynamics and kinetics of protein folding, protein aggregation and self-assembly in confined spaces. To obtain insights into the role of water in the context of folding problems, we describe computer simulations of a few related model systems. The dynamics of collapse of eicosane shows that upon expulsion of water the linear hydrocarbon chain adopts an ordered helical hairpin structure with 1.5 turns. The structure of dimer of eicosane molecules has two well ordered helical hairpins that are stacked perpendicular to each other. As a prelude to studying folding in confined spaces we used simulations to understand changes in hydrophobic and ionic interactions in nano-sized water droplets. Solvation of hydrophobic and charged species change drastically in nano-scale water droplets. Hydrophobic species are localized at the boundary. The tendency of ions to be at the boundary where water density is low increases as the charge density decreases. The interactions between hydrophobic, polar, and charged residue are also profoundly altered in confined spaces. Using the results of computer simulations and accounting for loss of chain entropy upon confinement we argue and then demonstrate, using simulations in explicit water, that ordered states of generic amphiphilic peptide sequences should be stabilized in cylindrical nanopores.

  2. In silico modelling for predicting the cationic hydrophobicity and cytotoxicity of ionic liquids towards the Leukemia rat cell line, Vibrio fischeri and Scenedesmus vacuolatus based on molecular interaction potentials of ions.

    Science.gov (United States)

    Cho, C-W; Ranke, J; Arning, J; Thöming, J; Preiss, U; Jungnickel, C; Diedenhofen, M; Krossing, I; Stolte, S

    2013-10-01

    In this study we present prediction models for estimating in silico the cationic hydrophobicity and the cytotoxicity (log [1/EC50]) of ionic liquids (ILs) towards the Leukemia rat cell line (IPC-81), the marine bacterium Vibrio fischeri and the limnic green algae Scenedesmus vacuolatus using linear free energy relationship (LFER) descriptors computed by COSMO calculations. The LFER descriptors used for the prediction model (i.e. excess molar refraction (E), dipolarity/polarizability (S), hydrogen-bonding acidity (A), hydrogen-bonding basicity (B) and McGowan volume (V)) were calculated using sub-descriptors (sig2, sig3, HBD3, HBA4, MR, and volume) derived from COSMO-RS, COSMO and OBPROP. With the combination of two solute descriptors (B, V) of the cation we were able to predict cationic hydrophobicity values (log ko ) with r (2) = 0.987 and standard error (SE) = 0.139 log units. By using the calculated log k o values, we were able to deduce a linear toxicity prediction model. In the second prediction study for the cytotoxicity of ILs, analysis of descriptor sensitivity helped us to determine that the McGowan volume (V) terms of the cation was the most important predictor of cytotoxicity and to simplify prediction models for cytotoxicity of ILs towards the IPC-81 (r (2) of 0.778, SE of 0.450 log units), Vibrio fischeri (r (2) of 0.762, SE of 0.529 log units) and Scenedesmus vacuolatus (r (2) of 0.776, SE of 0.825 log units). The robustness and predictivity of the two models for IPC-81 and Vibrio fischeri were checked by comparing the calculated SE and r (2) (coefficient of determination) values of the test set.

  3. High-throughput protein precipitation and hydrophobic interaction chromatography: salt effects and thermodynamic interrelation.

    Science.gov (United States)

    Nfor, Beckley K; Hylkema, Nienke N; Wiedhaup, Koenraad R; Verhaert, Peter D E M; van der Wielen, Luuk A M; Ottens, Marcel

    2011-12-09

    Salt-induced protein precipitation and hydrophobic interaction chromatography (HIC) are two widely used methods for protein purification. In this study, salt effects in protein precipitation and HIC were investigated for a broad combination of proteins, salts and HIC resins. Interrelation between the critical thermodynamic salting out parameters in both techniques was equally investigated. Protein precipitation data were obtained by a high-throughput technique employing 96-well microtitre plates and robotic liquid handling technology. For the same protein-salt combinations, isocratic HIC experiments were performed using two or three different commercially available stationary phases-Phenyl Sepharose low sub, Butyl Sepharose and Resource Phenyl. In general, similar salt effects and deviations from the lyotropic series were observed in both separation methods, for example, the reverse Hofmeister effect reported for lysozyme below its isoelectric point and at low salt concentrations. The salting out constant could be expressed in terms of the preferential interaction parameter in protein precipitation, showing that the former is, in effect, the net result of preferential interaction of a protein with water molecules and salt ions in its vicinity. However, no general quantitative interrelation was found between salting out parameters or the number of released water molecules in protein precipitation and HIC. In other words, protein solubility and HIC retention factor could not be quantitatively interrelated, although for some proteins, regular trends were observed across the different resins and salt types. Copyright © 2011 Elsevier B.V. All rights reserved.

  4. Hydrophobic interaction chromatography of proteins. IV. Protein adsorption capacity and transport in preparative mode.

    Science.gov (United States)

    To, Brian C S; Lenhoff, Abraham M

    2011-01-21

    The adsorption isotherms of four model proteins (lysozyme, α-lactalbumin, ovalbumin, and BSA) on eight commercial phenyl hydrophobic interaction chromatography media were measured. The isotherms were softer than those usually seen in ion-exchange chromatography of proteins, and the static capacities of the media were lower, ranging from 30 to 110 mg/mL, depending on the ammonium sulfate concentration and the protein and adsorbent types. The protein-accessible surface area appears to be the main factor determining the binding capacity, and little correlation was seen with the protein affinities of the adsorbents. Breakthrough experiments showed that the dynamic capacities of the adsorbents at 10% breakthrough were 20-80% of the static capacities, depending on adsorbent type. Protein diffusivities in the adsorbents were estimated from batch uptake experiments using the pore diffusion and homogeneous diffusion models. Protein transport was affected by the adsorbent pore structures. Apparent diffusivities were higher at lower salt concentrations and column loadings, suggesting that adsorbed proteins may retard intraparticle protein transport. The diffusivities estimated from the batch uptake experiments were used to predict column breakthrough behavior. Analytical solutions developed for ion-exchange systems were able to provide accurate predictions for lysozyme breakthrough but not for ovalbumin. Impurities in the ovalbumin solutions used for the breakthrough experiments may have affected the ovalbumin uptake and led to the discrepancies between the predictions and the experimental results. Copyright © 2010 Elsevier B.V. All rights reserved.

  5. Molecular aggregation in water : the interplay of hydrophobic and electrostatic interactions

    NARCIS (Netherlands)

    Buwalda, Rixt Tietje

    2001-01-01

    Hydrophobic interactions belong to the most important noncovalent interactions and play an important role in many (bio)chemical processes. A number of processes in aqueous solution like protein folding, surfactant aggregation or molecular recognition processes strongly rely on the interactions

  6. Detection of Heavy-metal Ions Based on Evaporative Concentration Using a Super-hydrophobic Surface

    Science.gov (United States)

    Yanagimachi, Isao; Nashida, Norihiro; Iwasa, Koichiro; Suzuki, Hiroaki

    A concentrator chip which could detect a variety of heavy-metal ions was fabricated. To improve the detection sensitivity, a droplet of a sample solution was concentrated evaporatively using a super-hydrophobic surface formed with polytetrafluoroethylene (PTFE) beads. The system consists of a working electrode at the center, surrounded by an Ag/AgCl reference electrode. Square-wave anodic stripping voltammetry was conducted using concentrator chips with different working electrode materials. A significant increase in peak height was observed as the sensitive area decreased and the volume of the droplet increased. When a 5-μl droplet was used, the detection limit for lead, cadmium, and arsenic ions was 1 ppb.

  7. A conserved patch of hydrophobic amino acids modulates Myb activity by mediating protein-protein interactions.

    Science.gov (United States)

    Dukare, Sandeep; Klempnauer, Karl-Heinz

    2016-07-01

    The transcription factor c-Myb plays a key role in the control of proliferation and differentiation in hematopoietic progenitor cells and has been implicated in the development of leukemia and certain non-hematopoietic tumors. c-Myb activity is highly dependent on the interaction with the coactivator p300 which is mediated by the transactivation domain of c-Myb and the KIX domain of p300. We have previously observed that conservative valine-to-isoleucine amino acid substitutions in a conserved stretch of hydrophobic amino acids have a profound effect on Myb activity. Here, we have explored the function of the hydrophobic region as a mediator of protein-protein interactions. We show that the hydrophobic region facilitates Myb self-interaction and binding of the histone acetyl transferase Tip60, a previously identified Myb interacting protein. We show that these interactions are affected by the valine-to-isoleucine amino acid substitutions and suppress Myb activity by interfering with the interaction of Myb and the KIX domain of p300. Taken together, our work identifies the hydrophobic region in the Myb transactivation domain as a binding site for homo- and heteromeric protein interactions and leads to a picture of the c-Myb transactivation domain as a composite protein binding region that facilitates interdependent protein-protein interactions of Myb with regulatory proteins. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. Modulation of graft architectures for enhancing hydrophobic interaction of biomolecules with thermoresponsive polymer-grafted surfaces.

    Science.gov (United States)

    Idota, Naokazu; Kikuchi, Akihiko; Kobayashi, Jun; Sakai, Kiyotaka; Okano, Teruo

    2012-11-01

    This paper describes the effects of graft architecture of poly(N-isopropylacrylamide) (PIPAAm) brush surfaces on thermoresponsive aqueous wettability changes and the temperature-dependent hydrophobic interaction of steroids in silica capillaries (I.D.: 50 μm). PIPAAm brushes were grafted onto glass substrates by surface-initiated atom transfer radical polymerization (ATRP) that is one of the living radical polymerization techniques. Increases in the graft density and chain length of PIPAAm brushes increased the hydration of polymer brushes, resulting in the increased hydrophilic properties of the surface below the transition temperature of PIPAAm at 32 °C. More hydrophobic surface properties were also observed on surfaces modified with the block copolymers of IPAAm and n-butyl methacrylate (BMA) than that with IPAAm homopolymer-grafted surfaces over the transition temperature. Using PBMA-b-PIPAAm-grafted silica capillaries, the baseline separation of steroids was successfully achieved by only changing temperature. The incorporation of hydrophobic PBMA chains in grafted PIPAAm enhanced the hydrophobic interaction with testosterone above the transition temperature. The surface modification of hydrophobicity-enhanced thermoresponsive polymers is a promising method for the preparation of thermoresponsive biointerfaces that can effectively modulated their biomolecule and cell adsorption with the wide dynamic range of hydrophilic/hydrophobic property change across the transition temperature. Copyright © 2011 Elsevier B.V. All rights reserved.

  9. Asymmetric electrostatic and hydrophobic-hydrophilic interaction forces between mica surfaces and silicone polymer thin films.

    Science.gov (United States)

    Donaldson, Stephen H; Das, Saurabh; Gebbie, Matthew A; Rapp, Michael; Jones, Louis C; Roiter, Yuri; Koenig, Peter H; Gizaw, Yonas; Israelachvili, Jacob N

    2013-11-26

    We have synthesized model hydrophobic silicone thin films on gold surfaces by a two-step covalent grafting procedure. An amino-functionalized gold surface reacts with monoepoxy-terminated polydimethylsiloxane (PDMS) via a click reaction, resulting in a covalently attached nanoscale thin film of PDMS, and the click chemistry synthesis route provides great selectivity, reproducibility, and stability in the resulting model hydrophobic silicone thin films. The asymmetric interaction forces between the PDMS thin films and mica surfaces were measured with the surface forces apparatus in aqueous sodium chloride solutions. At an acidic pH of 3, attractive interactions are measured, resulting in instabilities during both approach (jump-in) and separation (jump-out from adhesive contact). Quantitative analysis of the results indicates that the Derjaguin-Landau-Verwey-Overbeek theory alone, i.e., the combination of electrostatic repulsion and van der Waals attraction, cannot fully describe the measured forces and that the additional measured adhesion is likely due to hydrophobic interactions. The surface interactions are highly pH-dependent, and a basic pH of 10 results in fully repulsive interactions at all distances, due to repulsive electrostatic and steric-hydration interactions, indicating that the PDMS is negatively charged at high pH. We describe an interaction potential with a parameter, known as the Hydra parameter, that can account for the extra attraction (low pH) due to hydrophobicity as well as the extra repulsion (high pH) due to hydrophilic (steric-hydration) interactions. The interaction potential is general and provides a quantitative measure of interfacial hydrophobicity/hydrophilicity for any set of interacting surfaces in aqueous solution.

  10. Synthesis of sponge-like hydrophobic NiBi{sub 3} surface by 200 keV Ar ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Siva, Vantari; Datta, D.P. [School of Physical Sciences, National Institute of Science Education and Research, HBNI, Jatni 752050 (India); Chatterjee, S. [Colloids and Materials Chemistry Department, CSIR-Institute of Minerals and Materials Technology, Acharya Vihar, Bhubaneswar 751 013 (India); Varma, S. [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India); Kanjilal, D. [Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India); Sahoo, Pratap K., E-mail: pratap.sahoo@niser.ac.in [School of Physical Sciences, National Institute of Science Education and Research, HBNI, Jatni 752050 (India)

    2017-07-15

    Highlights: • A sponge-like hydrophobic NiBi{sub 3} surface has been synthesized using 200 keV Ar ion implantation. • A competition between amorphization and re-crystallization was observed in the existing phases owing to comparable magnitudes of nuclear and electronic energy depositions. • The relation between hydrophobic nature and sponge-like NiBi{sub 3} phase seems interesting, which is attributed to ion beam induced sputtering and mixing of the layers. - Abstract: Sponge-like nanostructures develop under Ar-ion implantation of a Ni–Bi bilayer with increasing ion fluence at room temperature. The surface morphology features different stages of evolution as a function of ion fluence, finally resulting in a planar surface at the highest fluence. Our investigations on the chemical composition reveal a spontaneous formation of NiBi{sub 3} phase on the surface of the as deposited bilayer film. Interestingly, we observe a competition between crystallization and amorphization of the existing poly-crystalline phases as a function of the implanted fluence. Measurements of contact angle by sessile drop method clearly show the ion-fluence dependent hydrophobic nature of the nano-structured surfaces. The wettability has been correlated with the variation in roughness and composition of the implanted surface. In fact, our experimental results confirm dominant effect of ion-sputtering as well as ion-induced mixing at the bilayer interface in the evolution of the sponge-like surface.

  11. Counter-ion binding and mobility in the presence of hydrophobic polyions – combining molecular dynamics simulations and NMR

    Directory of Open Access Journals (Sweden)

    Maksym Druchok

    2016-06-01

    Full Text Available Counter-ion binding and mobility in aqueous solutions of partially hydrophobic ionene oligoions is studied here by a combination of all-atomic molecular dynamics (MD simulations and NMR (19F and 81Br nuclei measurements. We present results for 12, 12–ionenes in the presence of different halide ions (F−, Cl−, Br− and I−, as well as their mixtures; the latter allowing us to probe counter-ion selectivity of these oligoions. We consolidate both structural and dynamic information, in particular simulated radial distribution functions and average residence times of counter-ions in the vicinity of ionenes and NMR data in the form of counter-ion chemical shift and self-diffusion coefficients. On one hand, previously reported enthalpy of dilution and mixing measurements show a reverse counter-ion sequence for 12, 12–ionenes with respect to their less hydrophobic 3, 3– and 6, 6– analogues. On the other hand, the current MD and NMR data, reflecting the counter-ion binding tendencies to the ionene chain, give evidence for the same ordering as that observed by MD for 3, 3–ionenes. This is not seen as a contradiction and can be rationalized on the basis of increasing chain hydrophobicity, which has different consequences for enthalpy and ion-binding. The latter is reflecting free energy changes and as such includes both enthalpic and entropic contributions.

  12. Counter-ion binding and mobility in the presence of hydrophobic polyions – combining molecular dynamics simulations and NMR

    Energy Technology Data Exchange (ETDEWEB)

    Druchok, Maksym [Institute for Condensed Matter Physics, Svientsitskii 1, 79011 Lviv (Ukraine); Malikova, Natalie; Rollet, Anne-Laure [Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR 8234, PHENIX, F-75005, Paris (France); Vlachy, Vojko, E-mail: vojko.vlachy@fkkt.uni-lj.si [Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana (Slovenia)

    2016-06-15

    Counter-ion binding and mobility in aqueous solutions of partially hydrophobic ionene oligoions is studied here by a combination of all-atomic molecular dynamics (MD) simulations and NMR ({sup 19}F and {sup 81}Br nuclei) measurements. We present results for 12, 12–ionenes in the presence of different halide ions (F{sup −}, Cl{sup −}, Br{sup −} and I{sup −}), as well as their mixtures; the latter allowing us to probe counter-ion selectivity of these oligoions. We consolidate both structural and dynamic information, in particular simulated radial distribution functions and average residence times of counter-ions in the vicinity of ionenes and NMR data in the form of counter-ion chemical shift and self-diffusion coefficients. On one hand, previously reported enthalpy of dilution and mixing measurements show a reverse counter-ion sequence for 12, 12–ionenes with respect to their less hydrophobic 3, 3– and 6, 6– analogues. On the other hand, the current MD and NMR data, reflecting the counter-ion binding tendencies to the ionene chain, give evidence for the same ordering as that observed by MD for 3, 3–ionenes. This is not seen as a contradiction and can be rationalized on the basis of increasing chain hydrophobicity, which has different consequences for enthalpy and ion-binding. The latter is reflecting free energy changes and as such includes both enthalpic and entropic contributions.

  13. N-capping motifs promote interaction of amphipathic helical peptides with hydrophobic surfaces and drastically alter hydrophobicity values of individual amino acids.

    Science.gov (United States)

    Spicer, Vic; Lao, Ying W; Shamshurin, Dmitry; Ezzati, Peyman; Wilkins, John A; Krokhin, Oleg V

    2014-12-02

    Capping rules, which govern interactions of helical peptides with hydrophobic surfaces, were never established before due to lack of methods for the direct measurement of polypeptide structure on the interphase boundary. We employed proteomic techniques and peptide retention modeling in reversed-phase chromatography to generate a data set sufficient for amino acid population analysis at helix ends. We found that interactions of amphipathic helical peptides with a hydrophobic C18 phase are induced by a unique motif featuring hydrophobic residues in the N1 and N2 positions adjacent to the N-cap (Asn, Asp, Ser, Thr, Gly), followed by Glu, Gln, or Asp in position N3 to complete a capping box. A favorable N-capping arrangement prior to amphipathic helix may result in the highest hydrophobicity (retention on C18 columns) of Asp/Asn (or Glu/Gln) peptide analogues among all naturally occurring amino acids when placed in N-cap or N3 position, respectively. These results contradict all previously reported hydrophobicity scales and provide new insights into our understanding of the phenomenon of hydrophobic interactions.

  14. Immobilization of molecular cobalt electrocatalyst by hydrophobic interaction with hematite photoanode for highly stable oxygen evolution

    KAUST Repository

    Joya, Khurram

    2015-07-15

    A unique modification of a hematite photoanode with perfluorinated Co-phthalocyanine (CoFPc) by strong binding associated with hydrophobic interaction is demonstrated. The resultant molecular electrocatalyst – hematite photoanode hybrid material showed significant onset shift and high stability for photoelectrochemical oxidation evolution reaction (OER).

  15. Reference interaction site model with hydrophobicity induced density inhomogeneity: An analytical theory to compute solvation properties of large hydrophobic solutes in the mixture of polyatomic solvent molecules

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Siqin [The HKUST Shenzhen Research Institute, Shenzhen (China); Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Sheong, Fu Kit [Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Huang, Xuhui, E-mail: xuhuihuang@ust.hk [The HKUST Shenzhen Research Institute, Shenzhen (China); Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Division of Biomedical Engineering, Center of Systems Biology and Human Health, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)

    2015-08-07

    Reference interaction site model (RISM) has recently become a popular approach in the study of thermodynamical and structural properties of the solvent around macromolecules. On the other hand, it was widely suggested that there exists water density depletion around large hydrophobic solutes (>1 nm), and this may pose a great challenge to the RISM theory. In this paper, we develop a new analytical theory, the Reference Interaction Site Model with Hydrophobicity induced density Inhomogeneity (RISM-HI), to compute solvent radial distribution function (RDF) around large hydrophobic solute in water as well as its mixture with other polyatomic organic solvents. To achieve this, we have explicitly considered the density inhomogeneity at the solute-solvent interface using the framework of the Yvon-Born-Green hierarchy, and the RISM theory is used to obtain the solute-solvent pair correlation. In order to efficiently solve the relevant equations while maintaining reasonable accuracy, we have also developed a new closure called the D2 closure. With this new theory, the solvent RDFs around a large hydrophobic particle in water and different water-acetonitrile mixtures could be computed, which agree well with the results of the molecular dynamics simulations. Furthermore, we show that our RISM-HI theory can also efficiently compute the solvation free energy of solute with a wide range of hydrophobicity in various water-acetonitrile solvent mixtures with a reasonable accuracy. We anticipate that our theory could be widely applied to compute the thermodynamic and structural properties for the solvation of hydrophobic solute.

  16. Application of Divergence Entropy to Characterize the Structure of the Hydrophobic Core in DNA Interacting Proteins

    Directory of Open Access Journals (Sweden)

    Barbara Kalinowska

    2015-03-01

    Full Text Available The fuzzy oil drop model, a tool which can be used to study the structure of the hydrophobic core in proteins, has been applied in the analysis of proteins belonging to the jumonji group—JARID2, JARID1A, JARID1B and JARID1D—proteins that share the property of being able to interact with DNA. Their ARID and PHD domains, when analyzed in the context of the fuzzy oil drop model, are found to exhibit structural variability regarding the status of their secondary folds, including the β-hairpin which determines their biological function. Additionally, the structure of disordered fragments which are present in jumonji proteins (as confirmed by the DisProt database is explained on the grounds of the hydrophobic core model, suggesting that such fragments contribute to tertiary structural stabilization. This conclusion is supported by divergence entropy measurements, expressing the degree of ordering in each protein’s hydrophobic core.

  17. Antibody-ligand interactions for hydrophobic charge-induction chromatography: a surface plasmon resonance study.

    Science.gov (United States)

    Cheng, Fang; Li, Ming-Yang; Wang, Han-Qi; Lin, Dong-Qiang; Qu, Jing-Ping

    2015-03-24

    This article describes the use of surface plasmon resonance (SPR) spectroscopy to study antibody-ligand interactions for hydrophobic charge-induction chromatography (HCIC) and its versatility in investigating the surface and solution factors affecting the interactions. Two density model surfaces presenting the HCIC ligand (mercapto-ethyl-pyridine, MEP) were prepared on Au using a self-assembly technique. The surface chemistry and structure, ionization, and protein binding of such model surfaces were characterized by X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS), contact-angle titration, and SPR, respectively. The influences of the surface and solution factors, e.g., ligand density, salt concentration, and solution pH, on protein adsorption were determined by SPR. Our results showed that ligand density affects both equilibrium and dynamic aspects of the interactions. Specifically, a dense ligand leads to an increase in binding strength, rapid adsorption, slow desorption, and low specificity. In addition, both hydrophobic interactions and hydrogen bonding contribute significantly to the protein adsorption at neutral pH, while the electrostatic repulsion is overwhelmed under acidic conditions. The hydrophobic interaction at a high concentration of lyotropic salt would cause drastic conformational changes in the adsorbed protein. Combined with the self-assembly technique, SPR proves to be a powerful tool for studying the interactions between an antibody and a chromatographic ligand.

  18. Molecular Theory and the Effects of Solute Attractive Forces on Hydrophobic Interactions.

    Science.gov (United States)

    Chaudhari, Mangesh I; Rempe, Susan B; Asthagiri, D; Tan, L; Pratt, L R

    2016-03-03

    The role of solute attractive forces on hydrophobic interactions is studied by coordinated development of theory and simulation results for Ar atoms in water. We present a concise derivation of the local molecular field (LMF) theory for the effects of solute attractive forces on hydrophobic interactions, a derivation that clarifies the close relation of LMF theory to the EXP approximation applied to this problem long ago. The simulation results show that change from purely repulsive atomic solute interactions to include realistic attractive interactions diminishes the strength of hydrophobic bonds. For the Ar-Ar rdfs considered pointwise, the numerical results for the effects of solute attractive forces on hydrophobic interactions are opposite in sign and larger in magnitude than predicted by LMF theory. That comparison is discussed from the point of view of quasichemical theory, and it is suggested that the first reason for this difference is the incomplete evaluation within LMF theory of the hydration energy of the Ar pair. With a recent suggestion for the system-size extrapolation of the required correlation function integrals, the Ar-Ar rdfs permit evaluation of osmotic second virial coefficients B2. Those B2's also show that incorporation of attractive interactions leads to more positive (repulsive) values. With attractive interactions in play, B2 can change from positive to negative values with increasing temperatures. This is consistent with the puzzling suggestions of decades ago that B2 ≈ 0 for intermediate cases of temperature or solute size. In all cases here, B2 becomes more attractive with increasing temperature.

  19. Polypropylene/hydrophobic-silica-aerogel-composite separator induced enhanced safety and low polarization for lithium-ion batteries

    Science.gov (United States)

    Feng, Guanhua; Li, Zihe; Mi, Liwei; Zheng, Jinyun; Feng, Xiangming; Chen, Weihua

    2018-02-01

    Separator as an important part of lithium-ion batteries, allowing the ion to transfer and preventing the direct contact of anode with cathode, determines the safety of the batteries. In this work, a kind of polypropylene/hydrophobic silica-aerogel-composite (SAC) separator is fabricated through combining hydrophobic silica aerogel and polypropylene (PP) separator. The rationally designed SAC effectively increases the thermal stability of the separator with slightly growing weight (the area retention rate is 30% higher than that of the PP separator after being heated for 30 min at 160 °C). In addition, the hydrophobic silica aerogel layer in SAC significantly improves the wettability of PP separator to electrolyte owning to the introduced hydrophobic functional groups of -Si(CH3)3 and porous structure, and the contact angles of SAC separator to several common organic electrolytes (EC/DMC, DMC/DOL, Diglyme) are close to 0°. Electrochemical tests show that the prepared SAC separator can decrease the polarization of Li-ion batteries and leads to improved power performance and cycle stability. And the SAC separator is firm with neglectable abscission after folding 200 times. This work provides a new way to improve the safety and simultaneously reduce the polarization of the batteries, implying promising application potential in power batteries.

  20. Toward a Molecular Understanding of the Mechanism of Cryopreservation by Polyampholytes: Cell Membrane Interactions and Hydrophobicity.

    Science.gov (United States)

    Rajan, Robin; Hayashi, Fumiaki; Nagashima, Toshio; Matsumura, Kazuaki

    2016-05-09

    Cryopreservation enables long-term preservation of cells at ultralow temperatures. Current cryoprotective agents (CPAs) have several limitations, making it imperative to develop CPAs with advanced properties. Previously, we developed a novel synthetic polyampholyte-based CPA, copolymer of 2-(dimethylamino)ethyl methacrylate (DMAEMA) and methacrylic acid(MAA) (poly(MAA-DMAEMA)), which showed excellent efficiency and biocompatibility. Introduction of hydrophobicity increased its efficiency significantly. Herein, we investigated the activity of other polyampholytes. We prepared two zwitterionic polymers, poly(sulfobetaine) (SPB) and poly(carboxymethyl betaine) (CMB), and compared their efficiency with poly(MAA-DMAEMA). Poly-SPB showed only intermediate property and poly-CMB showed no cryoprotective property. These data suggested that the polymer structure strongly influences cryoprotection, providing an impetus to elucidate the molecular mechanism of cryopreservation. We investigated the mechanism by studying the interaction of polymers with cell membrane, which allowed us to identify the interactions responsible for imparting different properties. Results unambiguously demonstrated that polyampholytes cryopreserve cells by strongly interacting with cell membrane, with hydrophobicity increasing the affinity for membrane interaction, which enables it to protect the membrane from various freezing-induced damages. Additionally, cryoprotective polymers, especially their hydrophobic derivatives, inhibit the recrystallization of ice, thus averting cell death. Hence, our results provide an important insight into the complex mechanism of cryopreservation, which might facilitate the rational design of polymeric CPAs with improved efficiency.

  1. Adsorption of bisphenol A based on synergy between hydrogen bonding and hydrophobic interaction.

    Science.gov (United States)

    Zhou, Xiangyu; Wei, Junfu; Liu, Kai; Liu, Nana; Zhou, Bin

    2014-11-25

    The study mainly investigated the synergetic adsorption of hydrogen bonding and hydrophobic interaction. To simplify the adsorption driving forces and binding sites, the hydrophilic and hydrophobic microdomain was introduced onto polypropylene (PP) nonwoven. The amphiphilic structure was constructed for the adsorption of bisphenol A (BPA). A solvent shielding experiment was conducted to calculate the contributions of diverse interactions. Also, a specific structure without hydrophilic microdomain was constructed as comparison to determine the adsorption rate and quantify the diffusion behaviors. On the basis of double-exponential model, the adsorption process can be distinctly divided into three stages, namely film diffusion stage, intralayer diffusion stage, and dynamic equilibrium stage. The adsorption rate was dramatically improved due to the influence of hydrophilic microdomain and participation of hydrogen bonding adsorption. Discussions on adsorption priority were also proposed. The results of surface energy heterogeneity revealed that the hydrophilic microdomain or the hydrogen bonding site was occupied preferentially.

  2. Silica-Derived Hydrophobic Colloidal Nano-Si for Lithium-Ion Batteries.

    Science.gov (United States)

    Liu, Zhiliang; Chang, Xinghua; Wang, Teng; Li, Wei; Ju, Haidong; Zheng, Xinyao; Wu, Xiuqi; Wang, Cong; Zheng, Jie; Li, Xingguo

    2017-06-27

    Silica can be converted to silicon by magnesium reduction. Here, this classical reaction is renovated for more efficient preparation of silicon nanoparticles (nano-Si). By reducing the particle size of the starting materials, the reaction can be completed within 10 min by mechanical milling at ambient temperature. The obtained nano-Si with high surface reactivity are directly reacted with 1-pentanol to form an alkoxyl-functionalized hydrophobic colloid, which significantly simplifies the separation process and minimizes the loss of small Si particles. Nano-Si in 5 g scale can be obtained in one single batch with laboratory scale setups with very high yield of 89%. Utilizing the excellent dispersion in ethanol of the alkoxyl-functionalized nano-Si, surface carbon coating can be readily achieved by using ethanol soluble oligomeric phenolic resin as the precursor. The nano-Si after carbon coating exhibit excellent lithium storage performance comparable to the state of the art Si-based anode materials, featured for the high reversible capacity of 1756 mAh·g-1 after 500 cycles at a current density of 2.1 A·g-1. The preparation approach will effectively promote the development of nano-Si-based anode materials for lithium-ion batteries.

  3. Single step plasmid DNA purification using methacrylate monolith bearing combination of ion-exchange and hydrophobic groups.

    Science.gov (United States)

    Smrekar, Vida; Smrekar, Franc; Strancar, Aleš; Podgornik, Aleš

    2013-02-08

    Purification of high quantities of human grade plasmid DNA is one of the most intensive production steps. Because of that several methods have been proposed, among them also chromatographic purification using methacrylate monoliths. Recently, a process comprising the combination of hydrophobic interaction (HIC) monolith and ion-exchange monolith was developed. In this work both chemistries were tried to be introduced on a single monolith. Methacrylate monoliths bearing octylamine groups, combination of butyl (C4) grafted methacrylate groups and diethylaminoethyl (DEAE) groups as well as grafted chains bearing both C4 and DEAE groups were prepared. All monoliths were investigated for their ionic and protein capacity and compared to conventional epoxy, C4, and DEAE methacrylate monoliths. Octylamine monolith and monolith bearing combination of C4 grafted methacrylate groups and DEAE groups were found to be the most promising candidates and were further tested for plasmid DNA (pDNA) dynamic binding capacity under ion-exchange (IEX) and HIC binding conditions and ability to separate open circular (OC) from supercoiled (SC) pDNA forms and RNA from pDNA. Since monolith bearing combination of grafted C4 methacrylate groups and DEAE groups was superior in all three tested features, exhibiting pDNA dynamic binding capacity of 4.7 mg/ml under IEX conditions and 2.1mg/ml under HIC conditions, it was used for the development of a single step purification method and tested with pure pDNA as well as with cell lysate. Developed method removed over 99% of RNA, host cell proteins (HCP) and genomic DNA (gDNA) demonstrating capacity to purify around 1.5mg of pDNA/ml of monolith from cell lysate. Copyright © 2012. Published by Elsevier B.V.

  4. Interactions between a polystyrene particle and hydrophilic and hydrophobic surfaces in aqueous solutions.

    Science.gov (United States)

    Thormann, Esben; Simonsen, Adam C; Hansen, Per L; Mouritsen, Ole G

    2008-07-15

    The interaction between a colloidal polystyrene particle mounted on an AFM cantilever and a hydrophilic and a hydrophobic surface in aqueous solution is investigated. Despite the apparent simplicity of these two types of systems a variety of different types of interactions are observed. The system containing the polystyrene particle and a hydrophilic surface shows DLVO-like interactions characteristic of forces between charged surfaces. However, when the surface is hydrophobized the interaction changes dramatically and shows evidence of a bridging air bubble being formed between the particle and the surface. For both sets of systems, plateaus of constant force in the force curves are obtained when the particle is retracted from the surface after being in contact. These events are interpreted as a number of individual polystyrene molecules that are bridging the polystyrene particle and the surface. The plateaus of constant force are expected for pulling a hydrophobic polymer in a bad (hydrophilic) solvent. The plateau heights are found to be of uniform spacing and independent of the type of surface, which suggests a model by which collapsed polymers are extended into the aqueous medium. This model is supported by a full stretching curve showing also the backbone elasticity and a stretching curve obtained in pentanol, where the plateau changes to a nonlinear force response, which is typical for a polymer in a good or neutral solvent. We suggest that these polymer bridges are important in particular for the interaction between polystyrene and the hydrophilic surface, where they to some extent counteract the long-range electrostatic repulsion.

  5. Thermodynamic Molecular Switch in Sequence-Specific Hydrophobic Interaction: Two Computational Models Compared

    Directory of Open Access Journals (Sweden)

    Paul Chun

    2003-01-01

    Full Text Available We have shown in our published work the existence of a thermodynamic switch in biological systems wherein a change of sign in ΔCp°(Treaction leads to a true negative minimum in the Gibbs free energy change of reaction, and hence, a maximum in the related Keq. We have examined 35 pair-wise, sequence-specific hydrophobic interactions over the temperature range of 273–333 K, based on data reported by Nemethy and Scheraga in 1962. A closer look at a single example, the pair-wise hydrophobic interaction of leucine-isoleucine, will demonstrate the significant differences when the data are analyzed using the Nemethy-Scheraga model or treated by the Planck-Benzinger methodology which we have developed. The change in inherent chemical bond energy at 0 K, ΔH°(T0 is 7.53 kcal mol-1 compared with 2.4 kcal mol-1, while ‹ts› is 365 K as compared with 355 K, for the Nemethy-Scheraga and Planck-Benzinger model, respectively. At ‹tm›, the thermal agitation energy is about five times greater than ΔH°(T0 in the Planck-Benzinger model, that is 465 K compared to 497 K in the Nemethy-Scheraga model. The results imply that the negative Gibbs free energy minimum at a well-defined ‹ts›, where TΔS° = 0 at about 355 K, has its origin in the sequence-specific hydrophobic interactions, which are highly dependent on details of molecular structure. The Nemethy-Scheraga model shows no evidence of the thermodynamic molecular switch that we have found to be a universal feature of biological interactions. The Planck-Benzinger method is the best known for evaluating the innate temperature-invariant enthalpy, ΔH°(T0, and provides for better understanding of the heat of reaction for biological molecules.

  6. Hydrophobic pore array surfaces: wetting and interaction forces in water/ethanol mixtures.

    Science.gov (United States)

    Hansson, Petra M; Hormozan, Yashar; Brandner, Birgit D; Linnros, Jan; Claesson, Per M; Swerin, Agne; Schoelkopf, Joachim; Gane, Patrick A C; Thormann, Esben

    2013-04-15

    Interactions between and wetting behavior of structured hydrophobic surfaces using different concentrations of water/ethanol mixtures have been investigated. Silica surfaces consisting of pore arrays with different pore spacings and pore depths were made hydrophobic by silanization. Their static and dynamic contact angles were found to be independent of the pore depth while fewer pores on the surface, i.e. a closer resemblance to a flat surface, gave a lower contact angle. As expected, a higher amount of ethanol facilitated wetting on all the surfaces tested. Confocal Raman microscopy measurements proved both water and ethanol to penetrate into the pores. AFM colloidal probe force measurements clearly showed that formation of air cavitation was hindered between the hydrophobic surfaces in presence of ethanol, and an increase in ethanol concentration was followed by a smaller jump-in distance and a weaker adhesion force. On separation, an immediate jump-out of contact occurred. The measured forces were interpreted as being due to capillary condensation of ethanol between the surfaces giving rise to very unstable cavities immediately rupturing on surface separation.

  7. Hydrophobic interactions are involved in the inhibition of human leukocyte elastase by alkyltrimethylammonium salts.

    Science.gov (United States)

    Kouadri-Boudjelthia, A; Wallach, J M

    1997-02-01

    Electrostatic forces and hydrophobic interactions had been suggested to modify the adsorption of elastases onto insoluble fibrous elastin, which is the initial stage of elastolysis, but conflicting results had been obtained, and comparison between compounds with different structures was difficult. In order to explore these observations, we have studied the effect of six alkyltrimethylammonium bromides, with alkyl chain length ranging from six to 16 carbon atoms, on human leucocyte elastase activities, either with a synthetic substrate or with insoluble elastin. The enzymatic studies were performed either spectrophotometrically or using conductimetry, and direct binding on to elastin was conductimetrically measured. Binding of the alkyltrimethylammonium salts is increasing with alkyl chain length and we could demonstrate a cooperative binding for tetra- and hexadecyl chains. No effect of the six compounds could be evidenced on hydrolysis of a specific synthetic substrate. With insoluble elastin, elastolysis inhibition could be demonstrated for alkyl chain longer than ten carbon atoms, the effect increasing with chain length. A similar inhibition was observed with the soluble kappa-elastin, but it was less effective. The study shows that the interaction between the alkyltrimethylammonium salts and elastin plays a major role in the inhibitory potency of these molecules. As this effect is enhanced with alkyl chain length, it was concluded that hydrophobic interactions favour their binding, protecting elastin against elastase adsorption.

  8. Hydrophobic interaction adsorption of hen egg white proteins albumin, conalbumin, and lysozyme.

    Science.gov (United States)

    Rojas, Edwin E Garcia; dos Reis Coimbra, Jane S; Minim, Luis A; Saraiva, Sérgio H; da Silva, César A Sodré

    2006-08-18

    Hydrophobic adsorption equilibrium data of the hen egg white proteins albumin, conalbumin, and lysozyme were obtained in batch systems, at 25 degrees C, using the Streamline Phenyl resin as adsorbent. The influence of three types of salt, NaCl, Na(2)SO(4), or (NH(4))(2)SO(4), and their concentration on the equilibrium data were evaluated. The salt Na(2)SO(4) showed the higher interaction with the studied proteins, thus favoring the adsorption of proteins by the adsorbent, even though each type of salt interacted in a distinct manner with each protein. The isotherm models of Langmuir, Langmuir exponential, and Chen and Sun were well fitted to the equilibrium data, with no significant difference being observed at the 5% level of significance. The mass transfer model applied simulated correctly adsorption kinetics of the proteins under the studied conditions.

  9. Effect of mass overloading on binding and elution of unstable proteins in hydrophobic interaction chromatography.

    Science.gov (United States)

    Muca, Renata; Marek, Wojciech; Żurawski, Marek; Piątkowski, Wojciech; Antos, Dorota

    2017-04-07

    Adsorption behavior of unstable proteins, i.e., bovine serum albumin and α-lactalbumin, has been studied on a hydrophobic interaction chromatography medium under mass overloading conditions at different kosmotropic salt concentrations in the mobile phase. A mechanistic model has been formulated and used to describe kinetics and thermodynamics of protein interactions with the adsorbent surface. The model assumed two-site binding adsorption and reversible protein unfolding, which allowed predicting the inhibition of protein unfolding at high column loadings. A simplified procedure for the determination of model parameters has been developed, which was based on the inverse method. The model was successfully used to reproduce the pattern of chromatographic elution as well as the course of breakthrough curves. The model formulation was supported by Nano Differential Scanning Fluorimetry measurements, which were exploited to determine the protein stability in the liquid and adsorbed phases at different column loadings and salt concentrations. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Synthesis of sponge-like hydrophobic NiBi3 surface by 200 keV Ar ion implantation

    Science.gov (United States)

    Siva, Vantari; Datta, D. P.; Chatterjee, S.; Varma, S.; Kanjilal, D.; Sahoo, Pratap K.

    2017-07-01

    Sponge-like nanostructures develop under Ar-ion implantation of a Ni-Bi bilayer with increasing ion fluence at room temperature. The surface morphology features different stages of evolution as a function of ion fluence, finally resulting in a planar surface at the highest fluence. Our investigations on the chemical composition reveal a spontaneous formation of NiBi3 phase on the surface of the as deposited bilayer film. Interestingly, we observe a competition between crystallization and amorphization of the existing poly-crystalline phases as a function of the implanted fluence. Measurements of contact angle by sessile drop method clearly show the ion-fluence dependent hydrophobic nature of the nano-structured surfaces. The wettability has been correlated with the variation in roughness and composition of the implanted surface. In fact, our experimental results confirm dominant effect of ion-sputtering as well as ion-induced mixing at the bilayer interface in the evolution of the sponge-like surface.

  11. Impact of organic modifier and temperature on protein denaturation in hydrophobic interaction chromatography.

    Science.gov (United States)

    Bobaly, Balázs; Beck, Alain; Veuthey, Jean-Luc; Guillarme, Davy; Fekete, Szabolcs

    2016-11-30

    The goal of this study was to better understand the chromatographic conditions in which monoclonal antibodies (mAbs) of broad hydrophobicity scale and a cysteine conjugated antibody-drug conjugate (ADCs), namely brentuximab-vedotin, could denaturate. For this purpose, some experiments were carried out in HIC conditions using various organic modifier in natures and proportions, different mobile phase temperatures and also different pHs. Indeed, improper analytical conditions in hydrophobic interaction chromatography (HIC) may create reversed-phase (RP) like harsh conditions and therefore protein denaturation. In terms of organic solvents, acetonitrile (ACN) and isopropanol (IPA) were tested with proportions ranging from 0 to 40%. It appeared that IPA was a less denaturating solvent than ACN, but should be used in a reasonable range (10-15%). Temperature should also be kept reasonable (below 40°C), to limit denaturation under HIC conditions. However, the combined increase of temperature and organic content induced denaturation of protein biopharmaceuticals in all cases. Indeed, above 30-40°C and 10-15% organic modifier in mobile phase B, heavy chain (HC) and light chain (LC) fragments dissociated. Mobile phase pH was also particularly critical and denaturation was significant even under moderately acidic conditions (pH of 5.4). Today, HIC is widely used for measuring drug-to-antibody ratio (DAR) of ADCs, which is a critical quality attribute of such samples. Here, we demonstrated that the estimation of average DAR can be dependent on the amount of organic modifier in the mobile phase under HIC conditions, due to the better recovery of the most hydrophobic proteins in presence of organic solvent (IPA). So, special care should be taken when measuring the average DAR of ADCs in HIC. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Thermodynamic modelling of hydrophobic interaction chromatography of biomolecules in the presence of salt.

    Science.gov (United States)

    Mirani, Mohammad Reza; Rahimpour, Farshad

    2015-11-27

    Hydrophobic interaction chromatography (HIC) is a useful method for isolation and purification of macromolecules. HIC separates proteins on the basis of surface hydrophobicity while generally retaining the activity of proteins. Aqueous mobile phases with high salt concentrations are often used to adsorb the proteins on a mildly hydrophobic support. In this research, the thermodynamic model of Chen and Sun, which predicts the adsorption isotherms of protein in presence of different type of salts, was modified by substitution the protein and salt activities in the mobile phase instead of their concentrations. In addition, model was examined for studying the adsorption of BSA, HSA, α-lactalbumin and Trypsinogen on different sepharose gels. The model parameters of Chen and Sun are adsorption equilibrium constant (KP), protein dehydration equilibrium constant (Ks), salt coefficient (α) and number of ligand binding (n). By substitution activity instead of salt and protein concentration, two other parameters (c1 and As), which related to the activity coefficients, are added to the model. The parameters of this nonlinear model are calculated by genetic algorithm (GA). The maximum average absolute percentage deviation (AAD) for the data which are obtained from the adsorption isotherm of BSA on phenyl sepharose gel, in the presence of different concentration of NaCl was 4.8%, while for Chen and Sun model, was 22.0%. Also maximum ADD for HSA, α-lactalbumin, and Trypsinogen adsorption was 7.8, 6.9, and 8.4, respectively. The results indicate that the modified model has adequate accuracy to predict protein HIC behaviour. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Separation of toxic metal ions, hydrophilic hydrocarbons, hydrophobic fuel and halogenated hydrocarbons and recovery of ethanol from a process stream

    Science.gov (United States)

    Kansa, Edward J.; Anderson, Brian L.; Wijesinghe, Ananda M.; Viani, Brian E.

    1999-01-01

    This invention provides a process to tremendously reduce the bulk volume of contaminants obtained from an effluent stream produced subsurface remediation. The chemicals used for the subsurface remediation are reclaimed for recycling to the remediation process. Additional reductions in contaminant bulk volume are achieved by the ultra-violet light destruction of halogenated hydrocarbons, and the complete oxidation of hydrophobic fuel hydrocarbons and hydrophilic hydrocarbons. The contaminated bulk volume will arise primarily from the disposal of the toxic metal ions. The entire process is modular, so if there are any technological breakthroughs in one or more of the component process modules, such modules can be readily replaced.

  14. Influence of mixed electrolytes and pH on adsorption of bovine serum albumin in hydrophobic interaction chromatography.

    Science.gov (United States)

    Hackemann, Eva; Hasse, Hans

    2017-10-27

    Using salt mixtures instead of single salts can be beneficial for hydrophobic interaction chromatography (HIC). The effect of electrolytes on the adsorption of proteins, however, depends on the pH. Little is known on that dependence for mixed electrolytes. Therefore, the effect of the pH on protein adsorption from aqueous solutions containing mixed salts is systematically studied in the present work for a model system: the adsorption of bovine serum albumin (BSA) on the mildly hydrophobic resin Toyopearl PPG-600M. The pH is adjusted to 4.0, 4.7 or 7.0 using 25mM sodium phosphate or sodium citrate buffer. Binary and ternary salt mixtures of sodium chloride, ammonium chloride, sodium sulfate and ammonium sulfate as well as the pure salts are used at overall ionic strengths between 1500 and 4200mM. The temperature is always 25°C. The influence of the mixed electrolytes on the adsorption behavior of BSA changes completely with varying pH. Positive as well as negative cooperative effects of the mixed electrolytes are observed. The results are analyzed using a mathematical model which was recently introduced by our group. In that model the influence of the electrolytes is described by a Taylor series expansion in the individual ion molarities. After suitable parametrization using a subset of the data determined in the present work, the model successfully predicts the influence of mixed electrolytes on the protein adsorption. Furthermore, results for BSA from the present study are compared to literature data for lysozyme, which are available for the same adsorbent, temperature and salts. By calculating the ratio of the loading of the adsorbent for both proteins particularly favorable separation conditions can be selected. Hence, a model-based optimization of solvents for protein separation is possible. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. New Information on the Hydrophobic Interaction Revealed by Frequency Modulation AFM.

    Science.gov (United States)

    Schlesinger, Itai; Sivan, Uri

    2017-03-14

    Using ultrahigh resolution atomic force microscopy (AFM) operated in frequency modulation mode, we extend existing measurements of the force acting between hydrophobic surfaces immersed in water in three essential ways. (1) The measurement range, which was previously limited to distances longer than 2-3 nm, is extended to cover all distances, down to contact. The measurements disclose that the long-range attraction observed also by conventional techniques, turns at distances shorter than 1-2 nm into pronounced repulsion. (2) Simultaneous measurements of the dissipative component of the tip-surface interaction reveal an anomalously large dissipation commencing abruptly at the point where attraction begins. The dissipation is more than 2 orders of magnitude larger than expected from bulk water viscosity or from similar measurements between hydrophilic surfaces. (3) The short-range repulsion is oscillatory, indicating molecular ordering of the medium as the hydrophobic surfaces approach each other. The oscillation period, ∼0.5 nm, is larger than the ∼0.3 nm period observed with hydrophilic surfaces. Their range, ∼1.5 nm, is longer as well. These observations are consistent with a conspicuous change in the properties of the surrounding medium, taking place simultaneously with the onset of attraction as the two surfaces approach each other.

  16. The interaction between fluid flow and ultra-hydrophobic surface in mini channel

    Directory of Open Access Journals (Sweden)

    Jasikova Darina

    2017-01-01

    Full Text Available Interaction of liquid with ultra-hydrophobic surface is accompanied by creation of layer of air. The effect of the air film has a potential of use in industry in many applications. The quality of the surface is influenced by matrix roughness, the character of physical or chemical cover. There was developed a method for analysis of the liquid flow and the air film using the lighting in volume, visualization with CCD camera and long distance microscope, and optical filters. There were prepared four stainless steel samples of inner channel of dimensions (80 × 8 × 8 mm and initial surface roughness Ra 0.33, Ra 1.0, Ra 2.0, and Ra 2.2. The inner channel was treated with plasma and commercial hydrophobic coating Greblon (WEILBURGER Coatings GmbH. There was realized study focused on the liquid flow velocity profile close to the air film. There are present results for laminar, transient and turbulent flows. The study also estimated the air film thickness depending on the Re number. The knowledge of the air film behaviour helps applied suitable degree of processing and cover for the target application.

  17. MICROBIAL CELL-SURFACE HYDROPHOBICITY - THE INVOLVEMENT OF ELECTROSTATIC INTERACTIONS IN MICROBIAL ADHESION TO HYDROCARBONS (MATH)

    NARCIS (Netherlands)

    GEERTSEMADOORNBUSCH, GI; VANDERMEI, HC; BUSSCHER, HJ

    Microbial adhesion to hydrocarbons (MATH) is the most commonly used method to determine microbial cell surface hydrophobicity. Since, however, the assay is based on adhesion, it is questionable whether the results reflect only the cell surface hydrophobicity or an interplay of hydrophobicity and

  18. The role of hydrophobic interactions in positioning of peripheral proteins in membranes

    Directory of Open Access Journals (Sweden)

    Lomize Mikhail A

    2007-06-01

    Full Text Available Abstract Background Three-dimensional (3D structures of numerous peripheral membrane proteins have been determined. Biological activity, stability, and conformations of these proteins depend on their spatial positions with respect to the lipid bilayer. However, these positions are usually undetermined. Results We report the first large-scale computational study of monotopic/peripheral proteins with known 3D structures. The optimal translational and rotational positions of 476 proteins are determined by minimizing energy of protein transfer from water to the lipid bilayer, which is approximated by a hydrocarbon slab with a decadiene-like polarity and interfacial regions characterized by water-permeation profiles. Predicted membrane-binding sites, protein tilt angles and membrane penetration depths are consistent with spin-labeling, chemical modification, fluorescence, NMR, mutagenesis, and other experimental studies of 53 peripheral proteins and peptides. Experimental membrane binding affinities of peripheral proteins were reproduced in cases that did not involve a helix-coil transition, specific binding of lipids, or a predominantly electrostatic association. Coordinates of all examined peripheral proteins and peptides with the calculated hydrophobic membrane boundaries, subcellular localization, topology, structural classification, and experimental references are available through the Orientations of Proteins in Membranes (OPM database. Conclusion Positions of diverse peripheral proteins and peptides in the lipid bilayer can be accurately predicted using their 3D structures that represent a proper membrane-bound conformation and oligomeric state, and have membrane binding elements present. The success of the implicit solvation model suggests that hydrophobic interactions are usually sufficient to determine the spatial position of a protein in the membrane, even when electrostatic interactions or specific binding of lipids are substantial. Our

  19. Hydrophobic Poly(ionic liquid for Highly Effective Separation of Methyl Blue and Chromium Ions from Water

    Directory of Open Access Journals (Sweden)

    Jie Kong

    2013-10-01

    Full Text Available The hydrophobic poly(ionic liquid of poly(3-ethyl-1-vinylimidazolium bis(trifluoromethanesulfonylimide (PVI-TFSI containing imidazolium cations and bis(trifluoromethanesulfonylimide anions was synthesized for the separation of methyl blue and chromium ions [Cr(VI] from water. The adsorption of methyl blue and Cr(VI in PVI-TSFI/water system reached equilibrium stage within 60 min and 12 h, and the maximum adsorbed percentage for methyl blue and Cr(VI was 97.6% and 98.0%, respectively. The adsorption regi me of either methyl blue or Cr(VI for PVI-TFSI was in correspondence with the Langmuir adsorption model. The maximum adsorption capacity of PVI-TFSI for methyl blue and Cr(VI was determined as 476.2 and 17.9 mg/g, respectively. The hydrophobic poly(ionic liquid with a remarkable adsorbent capacity of methyl blue and Cr(VI can be conveniently synthesized and shows potential in water treatment for the effective separation of organic dyes or heavy metal ions.

  20. Interaction between human BAP31 and respiratory syncytial virus small hydrophobic (SH) protein

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yan; Jain, Neeraj; Limpanawat, Suweeraya; To, Janet [School of Biological Sciences, Nanyang Technological University, 637551 (Singapore); Quistgaard, Esben M. [Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm (Sweden); Nordlund, Par [School of Biological Sciences, Nanyang Technological University, 637551 (Singapore); Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm (Sweden); Thanabalu, Thirumaran [School of Biological Sciences, Nanyang Technological University, 637551 (Singapore); Torres, Jaume, E-mail: jtorres@ntu.edu.sg [School of Biological Sciences, Nanyang Technological University, 637551 (Singapore)

    2015-08-15

    The small hydrophobic (SH) protein is a short channel-forming polypeptide encoded by the human respiratory syncytial virus (hRSV). Deletion of SH protein leads to the viral attenuation in mice and primates, and delayed apoptosis in infected cells. We have used a membrane-based yeast two-hybrid system (MbY2H) and a library from human lung cDNA to detect proteins that bind SH protein. This led to the identification of a membrane protein, B-cell associated protein 31 (BAP31). Transfected SH protein co-localizes with transfected BAP31 in cells, and pulls down endogenous BAP31. Titration of purified C-terminal endodomain of BAP31 against isotopically labeled SH protein in detergent micelles suggests direct interaction between the two proteins. Given the key role of BAP31 in protein trafficking and its critical involvement in pro- and anti-apoptotic pathways, this novel interaction may constitute a potential drug target. - Highlights: • A yeast two-hybrid system (MbY2H) detected BAP31 as a binder of RSV SH protein. • Transfected SH and BAP31 co-localize in lung epithelial cells. • Endogenous BAP31 is pulled down by RSV SH protein. • BAP31 endodomain interacts with the N-terminal α-helix of SH protein in micelles. • This interaction is proposed to be a potential drug target.

  1. Reduced hydrophobic interaction of polystyrene surfaces by spontaneous segregation of block copolymers with oligo (ethylene glycol) methyl ether methacrylate blocks: force measurements in water using atomic force microscope with hydrophobic probes.

    Science.gov (United States)

    Zhang, Rui; Seki, Akiko; Ishizone, Takashi; Yokoyama, Hideaki

    2008-05-20

    Reduction of hydrophobic interaction in water is important in biological interfaces. In our previous work, we have found that poly(styrene- b-triethylene glycol methyl ether methacrylate) (PS-PME3MA) segregates the PME3MA block to the surface in hydrophobic environment, such as in air or in a vacuum, and shows remarkable resistance against adsorption or adhesion of proteins, platelets, and cells in water. In this paper, we report that atomic force microscopy (AFM) with hydrophobic probes can directly monitor the reduced hydrophobic interaction of the PS surfaces modified by poly(styrene- b-origoethylene glycol methyl ether methacrylate) (PS-PME NMA), where N is the number of ethylene glycol units. The pull-off forces between the hydrophobic probes that are coated with octyltrichlorosilane (OLTS) and the PS-PME NMA modified polystyrene (PS) surfaces in water were measured. The absolute spring constants and tip-curvatures of the AFM cantilevers were measured to compute the work of adhesion by the Johnson, Kendall, and Roberts (JKR) theory, which relates the pull-off force at which the separation occurs between a hemisphere and a plane to the work of adhesion. The hydrophobic interactions between the hydrophobic tip and polymer surfaces in water were greatly reduced with the segregated PME NMA blocks. The hydrophobic interactions decrease with increasing N of the series of PS-PME NMA and show a correlation with the amount of protein adsorbed.

  2. Heparin coating of poly(ethylene terephthalate) decreases hydrophobicity, monocyte/leukocyte interaction and tissue interaction

    NARCIS (Netherlands)

    van Bilsen, Paul H. J.; Krenning, Guido; Billy, Didier; Duval, Jean-Luc; Huurdeman-Vincent, Judith; van Luyn, Marja J. A.

    2008-01-01

    Woven poly(ethylene terephthalate) (PET) is widely used in implantable medical devices. Upon implantation, fibrinogen interacts with the PET and changes conformation, such that the fibrinogen P2 epitope may become exposed. This allows inflammatory cells to interact with the material. In this study

  3. Energetic Ion Interactions with the Galilean Satellites

    Science.gov (United States)

    Cooper, John F.

    2000-01-01

    The principal research tasks of this investigation are: (1) specification of the energetic (keV to MeV) ion environments upstream of the four Galilean satellites and (2) data analysis and numerical modeling of observed ion interactions with the satellites. Differential flux spectra are being compiled for the most abundant ions (protons, oxygen, and sulfur) from measurements at 20 keV to 100 MeV total energy by the Energetic Particle Detector (EPD) experiment and at higher ion energies by the Heavy Ion Counter (HIC) experiment. Runge-Kutta and other numerical techniques are used to propagate test particles sampled from the measured upstream spectra to the satellite surface or spacecraft through the local magnetic and corotational electric field environment of each satellite. Modeling of spatial variations in directional flux anisotropies measured during each close flyby provides limits on atomic charge states for heavy (O, S) magnetospheric ions and on internal or induced magnetic fields of the satellites. Validation of models for magnetic and electric field configurations then allows computation of rates for ion implantation, sputtering, and energy deposition into the satellite surfaces for further modeling of observable chemical changes induced by irradiation. Our ongoing work on production of oxidants and other secondary species by ice irradiation on Europa's surface has significant applications, already acknowledged in current literature, to astrobiological evolution. Finally, the work will improve understanding of energetic ion sources and sinks at the satellite orbits for improved modeling of magnetospheric transport processes. The scope of the research effort mainly includes data from the primary Galileo mission (1995-1997) but may also include some later data where directly relevant (e.g., comparison of J0 and I27 data for Io) to the primary mission objectives. Funding for this contract also includes partial support for our related education and public

  4. Influence of binding pH and protein solubility on the dynamic binding capacity in hydrophobic interaction chromatography.

    Science.gov (United States)

    Baumann, Pascal; Baumgartner, Kai; Hubbuch, Jürgen

    2015-05-29

    Hydrophobic interaction chromatography (HIC) is one of the most frequently used purification methods in biopharmaceutical industry. A major drawback of HIC, however, is the rather low dynamic binding capacity (DBC) obtained when compared to e.g. ion exchange chromatography (IEX). The typical purification procedure for HIC includes binding at neutral pH, independently of the proteins nature and isoelectric point. Most approaches to process intensification are based on resin and salt screenings. In this paper a combination of protein solubility data and varying binding pH leads to a clear enhancement of dynamic binding capacity. This is shown for three proteins of acidic, neutral, and alkaline isoelectric points. High-throughput solubility screenings as well as miniaturized and parallelized breakthrough curves on Media Scout RoboColumns (Atoll, Germany) were conducted at pH 3-10 on a fully automated robotic workstation. The screening results show a correlation between the DBC and the operational pH, the protein's isoelectric point and the overall solubility. Also, an inverse relationship of DBC in HIC and the binding kinetics was observed. By changing the operational pH, the DBC could be increased up to 30% compared to the standard purification procedure performed at neutral pH. As structural changes of the protein are reported during HIC processes, the applied samples and the elution fractions were proven not to be irreversibly unfolded. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. Influence of hydrophobization of fumed oxides on interactions with polar and nonpolar adsorbates

    Science.gov (United States)

    Gun'ko, V. M.; Pakhlov, E. M.; Goncharuk, O. V.; Andriyko, L. S.; Marynin, A. I.; Ukrainets, A. I.; Charmas, B.; Skubiszewska-Zięba, J.; Blitz, J. P.

    2017-11-01

    A variety of unmodified and modified fumed silica A-300 and silica/titania (ST20 and ST76 at 20 and 76 wt.% of titania, respectively) was prepared to analyze features of their interactions with polar and nonpolar adsorbates. The materials were studied using nitrogen adsorption-desorption, ethanol evaporation kinetics, infrared (IR) spectroscopy, thermogravimetry (TG), photon correlation spectroscopy, differential scanning calorimetry (DSC), DSC and TG thermoporometry, and quantum chemistry. Changes in surface structure of modified nanooxides with increasing hydrophobization degree (ΘMS) from 20% to 100% have a strong affect on the textural characteristics of the materials and adsorption-desorption of various adsorbates. Confined space effects enhanced due to the location of adsorbates in narrow voids between nanoparticles lead to freezing-melting point depression for bound polar and nonpolar adsorbates. The behavior of particles of modified nanooxides in aqueous and water/ethanol media is strongly altered due to enhanced aggregations with increasing value of ΘMS. All of these change are non-monotonic functions of ΘMS which affects (i) rearrangement of nanoparticles, (ii) interactions with polar and nonpolar adsorbates, (iii) location of adsorbates in voids of different sizes, (iv) the clustering of adsorbates and formation of nearly bulk structures.

  6. Difference of carboxybetaine and oligo(ethylene glycol) moieties in altering hydrophobic interactions: a molecular simulation study.

    Science.gov (United States)

    Shao, Qing; White, Andrew D; Jiang, Shaoyi

    2014-01-09

    Polycarboxybetaine and poly(ethylene glycol) materials resist nonspecific protein adsorption but differ in influencing biological functions such as enzymatic activity. To investigate this difference, we studied the influence of carboxybetaine and oligo(ethylene glycol) moieties on hydrophobic interactions using molecular simulations. We employed a model system composed of two non-polar plates and studied the potential of mean force of plate-plate association in carboxybetaine, (ethylene glycol)4, and (ethylene glycol)2 solutions using well-tempered metadynamics simulations. Water, trimethylamine N-oxide, and urea solutions were used as reference systems. We analyzed the variation of the potential of mean force in various solutions to study how carboxybetaine and oligo(ethylene glycol) moieties influence the hydrophobic interactions. To study the origin of their influence, we analyzed the normalized distributions of moieties and water molecules using molecular dynamics simulations. The simulation results showed that oligo(ethylene glycol) moieties repel water molecules away from the non-polar plates and weaken the hydrophobic interactions. Carboxybetaine moieties do not repel water molecules away from the plates and therefore do not influence the hydrophobic interactions.

  7. The role of hydrophobic surfaces in altering water-mediated peptide-peptide interactions in an aqueous environment.

    Science.gov (United States)

    Yoo, Soohaeng; Xantheas, Sotiris S

    2011-06-16

    Using Born-Oppenheimer molecular dynamics within the density functional framework, we calculated the effective force acting on water-mediated peptide-peptide interaction between antiparallel β-sheets in an aqueous environment and also in the vicinity of a hydrophobic surface. From the magnitude of the effective force (corresponding to the slope of the free energy as a function of the interpeptide distance) and its sign (a negative value indicates an effective attraction, whereas a positive value indicates an effective repulsion) we can elucidate the fundamental differences of the water-mediated peptide-peptide interactions in those two environments. The computed effective forces indicate that the water-mediated interaction between peptides in an aqueous environment is attractive in the range of interpeptide distance d = 7-8 Å when hydrophobic surfaces are not nearby. Due to the stabilization of the water molecules bridging between the two β-sheets, a free energy barrier exists between the direct and indirect (water-mediated) interpeptide interactions. However, when the peptides are in the proximity of hydrophobic surfaces, this free energy barrier decreases because the hydrophobic surfaces enhance the interpeptide attraction by the destabilization and ease-to-libration of the bridging water molecules between them. © 2011 American Chemical Society

  8. Fabrication of Super-Hydrophobic Microchannels via Strain-Recovery Deformations of Polystyrene and Oxygen Reactive Ion Etch

    Directory of Open Access Journals (Sweden)

    Anirban Chakraborty

    2013-08-01

    Full Text Available In this article, we report a simple approach to generate micropillars (whose top portions are covered by sub-micron wrinkles on the inner surfaces of polystyrene (PS microchannels, as well as on the top surface of the PS substrate, based on strain-recovery deformations of the PS and oxygen reactive ion etch (ORIE. Using this approach, two types of micropillar-covered microchannels are fabricated. Their widths range from 118 μm to 132 μm, depths vary from 40 μm to 44 μm, and the inclined angles of their sidewalls are from 53° to 64°. The micropillars enable these microchannels to have super-hydrophobic properties. The contact angles observed on the channel-structured surfaces are above 162°, and the tilt angles to make water drops roll off from these channel-structured substrates can be as small as 1°.

  9. Ion beam control in laser plasma interaction

    Science.gov (United States)

    Kawata, S.; Izumiyama, T.; Sato, D.; Nagashima, T.; Takano, M.; Barada, D.; Gu, Y. J.; Ma, Y. Y.; Kong, Q.; Wang, P. X.; Wang, W. M.

    2016-03-01

    By a two-stage successive acceleration in laser ion acceleration, our 2.5-dimensional particle-in-cell simulations demonstrate a remarkable increase in ion energy by a few hundreds of MeV; the maximum proton energy reaches about 250MeV. The ions are accelerated by the inductive continuous post-acceleration in a laser plasma interaction together with the target normal sheath acceleration and the breakout afterburner mechanism. An intense short-pulse laser generates a strong current by high-energy electrons accelerated, when an intense short- pulse laser illuminates a plasma target. The strong electric current creates a strong magnetic field along the high-energy electron current in the plasma. During the increase phase in the magnetic field strength, the moving longitudinal inductive electric field is induced by the Faraday law, and accelerates the forward-moving ions continously. The multi-stage acceleration provides a unique controllability in the ion energy and its quality.

  10. Interactions between nano-TiO{sub 2} and the oral cavity: Impact of nanomaterial surface hydrophilicity/hydrophobicity

    Energy Technology Data Exchange (ETDEWEB)

    Teubl, Birgit J.; Schimpel, Christa [Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology, University of Graz, 8010 (Austria); Leitinger, Gerd [Institute of Cell Biology, Histology and Embryology, Research Unit Electron Microscopic Techniques, Medical University of Graz, 8010 (Austria); Center for Medical Research, Medical University of Graz, 8010 (Austria); BioTechMed, Graz 8010 (Austria); Bauer, Bettina [Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology, University of Graz, 8010 (Austria); Fröhlich, Eleonore [Center for Medical Research, Medical University of Graz, 8010 (Austria); BioTechMed, Graz 8010 (Austria); Zimmer, Andreas [Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology, University of Graz, 8010 (Austria); BioTechMed, Graz 8010 (Austria); Roblegg, Eva, E-mail: eva.roblegg@uni-graz.at [Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology, University of Graz, 8010 (Austria); BioTechMed, Graz 8010 (Austria)

    2015-04-09

    Highlights: • Hydrophilic as well as hydrophobic TiO{sub 2} NPs agglomerated under oral physiological conditions. • Particles penetrated the upper and lower buccal epithelium, independent on the degree of hydrophilicity. • Most of the hydrophobic particles were found in vesicular structures, while hydrophilic particles were freely distributed in the cytoplasm. • Hydrophilic particles had a higher potential to trigger toxic effects (e.g., ROS) than hydrophobic particles. - Abstract: Titanium dioxide (TiO{sub 2}) nanoparticles are available in a variety of oral applications, such as food additives and cosmetic products. Thus, questions about their potential impact on the oro-gastrointestinal route rise. The oral cavity represents the first portal of entry and is known to rapidly interact with nanoparticles. Surface charge and size contribute actively to the particle–cell interactions, but the influence of surface hydrophilicity/hydrophobicity has never been shown before. This study addresses the biological impact of hydrophilic (NM 103, rutile, 20 nm) and hydrophobic (NM 104, rutile, 20 nm) TiO{sub 2} particles within the buccal mucosa. Particle characterization was addressed with dynamic light scattering and laser diffraction. Despite a high agglomeration tendency, 10% of the particles/agglomerates were present in the nanosized range and penetrated into the mucosa, independent of the surface properties. However, significant differences were observed in intracellular particle localization. NM 104 particles were found freely distributed in the cytoplasm, whereas their hydrophobic counterparts were engulfed in vesicular structures. Although cell viability/membrane integrity was not affected negatively, screening assays demonstrated that NM 104 particles showed a higher potential to decrease the physiological mitochondrial membrane potential than NM 103, resulting in a pronounced generation of reactive oxygen species.

  11. Isotherm type shift of hydrophobic interaction adsorption and its effect on chromatographic behavior.

    Science.gov (United States)

    Meng, Qingqiang; Wang, Jiaxing; Ma, Guanghui; Su, Zhiguo

    2013-02-01

    Adsorption isotherm type is a key factor in simulating chromatographic profiles. In this study, the adsorption isotherm type of pure bovine serum albumin (BSA) and immunoglobulin G (IgG) on hydrophobic interaction chromatography (HIC) media was found to shift from Freundlich to Langmuir with the increase of salt concentration. For BSA on butyl-, phenyl- and octyl-sepharose, the isotherm type shift occurred when the salt concentrations were higher than 1.8, 1.5 and 1.4 mol/L, respectively. For IgG, the turning points were 1.0 mol/L on phenyl-sepharose and 0.9 mol/L on octyl-sepharose. Circular dichroism spectra and high-performance size-exclusion chromatography found no obvious conformational change or oligomer formation for the proteins in the solutions with different salt concentrations. HIC profiles of BSA and IgG revealed that the isotherm type shift greatly affected the chromatographic behavior, because the original single peak was coincidentally split into two peaks at the salt concentrations over which the isotherm type shift occurred. Combining both the isotherm type shift and peak-splitting phenomena, it was possible that the change of protein-protein repulsion among adsorbed protein molecules under different salt concentrations caused the abnormal behavior of adsorption isotherm and chromatographic profiles.

  12. Isolation of soybean protein P34 from oil bodies using hydrophobic interaction chromatography

    Directory of Open Access Journals (Sweden)

    Seidel-Morgenstern Andreas

    2008-03-01

    Full Text Available Abstract Background Soybeans play a prominent role in allergologic research due to the high incidence of allergic reactions. For detailed studies on specific proteins it is necessary to have access to a large amount of pure substance. Results In this contribution, a method for purifying soybean (Glycine max protein P34 (also called Gly m Bd 30 K or Gly m 1 using hydrophobic interaction chromatography is presented. After screening experiments using 1 mL HiTrap columns, Butyl Sepharose 4 FF was selected for further systematic investigations. With this stationary phase, suitable operation conditions for two-step gradient elution using ammonium sulphate were determined experimentally. The separation conditions obtained in a small column could be scaled up successfully to column volumes of 7.5 and 75 mL, allowing for high product purities of almost 100% with a yield of 27% for the chromatographic separation step. Conditions could be simplified further using a onestep gradient, which gave comparable purification in a shorter process time. The identity of the purified protein was verified using in-gel digestion and mass spectrometry as well as immunological techniques. Conclusion With the technique presented it is possible to produce, within a short timeframe, pure P34, suitable for further studies where an example antigen is needed.

  13. Simulations of RNA interactions with monovalent ions.

    Science.gov (United States)

    Chen, Alan A; Marucho, Marcelo; Baker, Nathan A; Pappu, Rohit V

    2009-01-01

    RNA folding and binding reactions are mediated by interactions with ions that make up the surrounding aqueous electrolytic milieu. Although Mg(2+) ions are often implicated as being crucial for RNA folding, it is known that folding is feasible in high concentrations of monovalent alkali-halide salts. Experiments have yielded important information regarding the salt dependence of RNA stability. Recent work has shown that molecular simulations based on explicit representations of solvent molecules and monovalent ions can also provide useful insights regarding the ionic atmospheres around model RNA systems. These insights can help rationalize intriguing observations regarding the dependence of RNA stability on cation type providing one pays attention to important considerations that go into the proper design of molecular simulations. These issues are discussed in detail and the methods are applied to an A-form RNA and B-form DNA sequence. The results of these simulations are compared to previous work on a kissing-loop system with analogous sequence. In particular, ionic atmospheres obtained from molecular simulations are compared to those obtained using the nonlinear Poisson Boltzmann model for continuum electrostatics for these three different nucleic acid systems. The comparisons indicate reasonable agreement in terms of coarse-grained observables such as the numbers of counterions accumulated around the solutes. However, details of the ionic atmospheres, captured in terms of spatial free energy density profiles, are quite different between the two approaches. These comparisons suggest the need for improvements in continuum models to capture sequence-specific effects, ion-ion correlation, and the effects of partial dehydration of ions. Copyright © 2009 Elsevier Inc. All rights reserved.

  14. Interactions of fast ions with graphene

    Directory of Open Access Journals (Sweden)

    Radović Ivan S.

    2009-01-01

    Full Text Available In this work, we study the interactions of fast ions with graphene describing the excitations of the electron gas in graphene by a two-dimensional (2D hydrodynamic model (one-fluid and two-fluid model. The two-fluid model reproduces qualitatively the split of plasmon dispersions into the low-frequency p-electron branch and the high-frequency s+p-electron branch. We calculate the stopping force and the image force on an ion moving parallel to a single sheet of graphene. Numerical results show that the presence of the low-energy, quasiacoustic plasmon in the two-fluid model gives rise to resonant features at low velocities around its 'acoustic' speed, which are not seen in the one-fluid model. The two models give virtually indistinguishable results for both forces at high speeds. Marked differences between the two models in the values of image forces at low speeds can be seen. Numerical results show that the magnitudes of both the stopping and image forces exhibit typical resonance-shaped velocity dependencies, with the peak positions moving to higher velocities for higher distances and with the overall magnitudes decreasing sharply with increasing distances. The second order corrections are found to be small, as expected for fast ions outside the electron gas, but their relative magnitudes should be easily discernible in experiments on ion grazing scattering from graphene. One notices effects which are similar to those obtained earlier for proton channeling in carbon nanotubes.

  15. The use of dielectric spectroscopy for the characterisation of the precipitation of hydrophobically modified poly(acrylic-acid) with divalent barium ions

    DEFF Research Database (Denmark)

    Christensen, Peter Vittrup; Keiding, Kristian

    2009-01-01

    The use of dielectric spectroscopy as a monitor for coagulation processes was investigated. Hydrophobically modified poly(acrylic-acid) polymers were used as model macromolecules and coagulated with barium ions. The coagulation process was quantified using a photometric dispersion analyser, thereby...

  16. Prediction of protein retention times in hydrophobic interaction chromatography by robust statistical characterization of their atomic-level surface properties.

    Science.gov (United States)

    Hanke, Alexander T; Klijn, Marieke E; Verhaert, Peter D E M; van der Wielen, Luuk A M; Ottens, Marcel; Eppink, Michel H M; van de Sandt, Emile J A X

    2016-03-01

    The correlation between the dimensionless retention times (DRT) of proteins in hydrophobic interaction chromatography (HIC) and their surface properties were investigated. A ternary atomic-level hydrophobicity scale was used to calculate the distribution of local average hydrophobicity across the proteins surfaces. These distributions were characterized by robust descriptive statistics to reduce their sensitivity to small changes in the three-dimensional structure. The applicability of these statistics for the prediction of protein retention behaviour was looked into. A linear combination of robust statistics describing the central tendency, heterogeneity and frequency of highly hydrophobic clusters was found to have a good predictive capability (R2  = 0.78), when combined a factor to account for protein size differences. The achieved error of prediction was 35% lower than for a similar model based on a description of the protein surface on an amino acid level. This indicates that a robust and mathematically simple model based on an atomic description of the protein surface can be used for the prediction of the retention behaviour of conformationally stable globular proteins with a well determined 3D structure in HIC. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:372-381, 2016. © 2016 American Institute of Chemical Engineers.

  17. Interactions of hydrophobically modified polyvinylamines: adsorption behavior at charged surfaces and the formation of polyelectrolyte multilayers with polyacrylic acid.

    Science.gov (United States)

    Illergård, Josefin; Enarsson, Lars-Erik; Wågberg, Lars; Ek, Monica

    2010-02-01

    The structure and adsorption behaviors of two types of hydrophobically modified polyvinylamines (PVAm) containing substituents of hexyl and octyl chains were compared to a native polyvinylamine sample. The conformation of dissolved polyvinylamines was studied in aqueous salt solutions using dynamic light scattering. Modified PVAm showed hydrodynamic diameters similar to native PVAm, which indicated that all PVAm polymers were present as single molecules in solution. The adsorption of the polyvinylamines, both native and hydrophobically modified, from aqueous solution onto negatively charged silica surfaces was studied in situ by reflectometry and quartz crystal microgravimetry with dissipation. Polyelectrolyte multilayers (PEM) with up to nine individual layers were formed together with poly(acrylic acid). Obtained PEM structures were rigid and showed high adsorbed amounts combined with low dissipation, with similar results for both the modified and unmodified PVAm. This suggests that electrostatics dominated the PEM formation. At lower salt concentrations, the hydrophobically modified PVAm produced multilayers with low water contents, indicating that secondary interactions induced by the hydrophobic constituents can also have a significant influence on the properties of the formed layers. The surface structure of PEMs with nine individual layers was imaged in dry state using atomic force microscopy in a dynamic mode. Modified PVAm was found to induce a different structure of the PEM at 100 mM, with larger aggregates compared to those of native PVAm. From these results, it is proposed that modified PVAm can induce aggregation within the PEM, whereas PVAm remains as single molecules in solution.

  18. Collagen mimetic peptide discs promote assembly of a broad range of natural protein fibers through hydrophobic interactions.

    Science.gov (United States)

    McGuinness, Kenneth; Nanda, Vikas

    2017-07-19

    Collagen mimetic peptides that alone formed two-dimensional nanoscale discs driven by hydrophobic interactions were shown in electron microscopy studies to also co-assemble with natural fibrous proteins to produce discs-on-a-string (DoS) nanostructures. In most cases, peptide discs also facilitated bundling of the protein fibers. This provides insight into how synthetic and natural proteins may be combined to develop multicomponent, multi-dimensional architectures at the nanoscale.

  19. Interaction forces between a deformable air bubble and a spherical particle of tuneable hydrophobicity and surface charge in aqueous solutions.

    Science.gov (United States)

    Englert, A H; Ren, S; Masliyah, J H; Xu, Z

    2012-08-01

    Interaction forces between an air bubble and a spherical particle of moderate and tuneable surface charge density and hydrophobicity in aqueous solutions were measured using atomic force microscopy. Bitumen coated silica spheres were used as model particles of tuneable charge density and hydrophobicity due to pH-dependent ionisation of carboxylic acids at bitumen-water interfaces. The measured force profiles showed a long-range repulsion prior to jump into contact, indicating the rupture of intervening liquid film between the bitumen and bubble surfaces. The long-range repulsive force increased with increasing pH. The measured force profiles were analysed by adopting the model originally developed by White and co-workers to account for deformation and change in shape of bubbles before rupture of the intervening liquid film. Satisfactory agreement between the theory and measured force profiles was obtained, showing the suitability of the model to describe the measured interaction forces. The model was then used to study the physical parameters on the particle-bubble interaction forces prior to three phase contact line (TPCL) formation. The hydrophobic decay length, surface potential and size of bubble and probe particles, and ionic strength of the medium (KCl concentration) were found to have a strong influence on the predicted force profiles. Copyright © 2012 Elsevier Inc. All rights reserved.

  20. Basic atomic interactions of accelerated heavy ions in matter atomic interactions of heavy ions

    CERN Document Server

    Tolstikhina, Inga; Winckler, Nicolas; Shevelko, Viacheslav

    2018-01-01

    This book provides an overview of the recent experimental and theoretical results on interactions of heavy ions with gaseous, solid and plasma targets from the perspective of atomic physics. The topics discussed comprise stopping power, multiple-electron loss and capture processes, equilibrium and non-equilibrium charge-state fractions in penetration of fast ion beams through matter including relativistic domain. It also addresses mean charge-states and equilibrium target thickness in ion-beam penetrations, isotope effects in low-energy electron capture, lifetimes of heavy ion beams, semi-empirical formulae for effective cross sections. The book is intended for researchers and graduate students working in atomic, plasma and accelerator physics.

  1. Diels-Alder reactions in water : Enforced hydrophobic interaction and hydrogen bonding

    NARCIS (Netherlands)

    Engberts, Jan B.F.N.

    1995-01-01

    Second-order rate constants have been measured for the Diels-Alder (DA) reactions of cyclopentadiene with dienophiles of varying hydrophobicity and hydrogen-bond acceptor capacity in water, in a series of organic solvents and in alcohol-water mixtures. The intramolecular DA reaction of

  2. DIELS-ALDER REACTIONS IN WATER - ENFORCED HYDROPHOBIC INTERACTION AND HYDROGEN-BONDING

    NARCIS (Netherlands)

    Engberts, J.B.F.N.

    Second-order rate constants have been measured for the Diels-Alder (DA) reactions of cyclopentadiene with dienophiles of varying hydrophobicity and hydrogen-bond acceptor capacity in water, in a series of organic solvents and in alcohol-water mixtures. The intramolecular DA reaction of

  3. 3DRISM-HI-D2MSA: an improved analytic theory to compute solvent structure around hydrophobic solutes with proper treatment of solute–solvent electrostatic interactions

    KAUST Repository

    Cao, Siqin

    2017-12-22

    The 3D reference interaction site model (3DRISM) is a powerful tool to study the thermodynamic and structural properties of liquids. However, for hydrophobic solutes, the inhomogeneity of the solvent density around them poses a great challenge to the 3DRISM theory. To address this issue, we have previously introduced the hydrophobic-induced density inhomogeneity theory (HI) for purely hydrophobic solutes. To further consider the complex hydrophobic solutes containing partial charges, here we propose the D2MSA closure to incorporate the short-range and long-range interactions with the D2 closure and the mean spherical approximation, respectively. We demonstrate that our new theory can compute the solvent distributions around real hydrophobic solutes in water and complex organic solvents that agree well with the explicit solvent molecular dynamics simulations.

  4. Highly charged Arq+ ions interacting with metals

    Science.gov (United States)

    Wang, Jijin; Zhang, Jian; Gu, Jiangang; Luo, Xianwen; Hu, Bitao

    2009-12-01

    Using computer simulation, alternative methods of the interaction of highly charged ions Arq+ with metals (Au, Ag) are used and verified in the present work. Based on the classical over-barrier model, we discussed the promotion loss and peeling off processes. The simulated total potential electron yields agree well with the experiment data in incident energy ranging from 100 eV to 5 keV and all charge states of Arq+ . Based on the TRIM code, we obtain the side-feeding rate as well as the motion and charge transfer of HCI below the surface. Some results, including the array of KLx x-ray satellite lines, the respective contribution of autoionization, and side-feeding to inner shells, and the filling rates and lifetime of inner shells for Ar agree well with experiment or theory.

  5. Hydrophobic interactions in model enclosures from small to large length scales: non-additivity in explicit and implicit solvent models.

    Science.gov (United States)

    Wang, Lingle; Friesner, Richard A; Berne, B J

    2010-01-01

    The binding affinities between a united-atom methane and various model hydrophobic enclosures were studied through high accuracy free energy perturbation methods (FEP). We investigated the non-additivity of the hydrophobic interaction in these systems, measured by the deviation of its binding affinity from that predicted by the pairwise additivity approximation. While only small non-additivity effects were previously reported in the interactions in methane trimers, we found large cooperative effects (as large as -1.14 kcal mol(-1) or approximately a 25% increase in the binding affinity) and anti-cooperative effects (as large as 0.45 kcal mol(-1)) for these model enclosed systems. Decomposition of the total potential of mean force (PMF) into increasing orders of multi-body interactions indicates that the contributions of the higher order multi-body interactions can be either positive or negative in different systems, and increasing the order of multi-body interactions considered did not necessarily improve the accuracy. A general correlation between the sign of the non-additivity effect and the curvature of the solute molecular surface was observed. We found that implicit solvent models based on the molecular surface area (MSA) performed much better, not only in predicting binding affinities, but also in predicting the non-additivity effects, compared with models based on the solvent accessible surface area (SASA), suggesting that MSA is a better descriptor of the curvature of the solutes. We also show how the non-additivity contribution changes as the hydrophobicity of the plate is decreased from the dewetting regime to the wetting regime.

  6. Elucidation of conformer preferences for a hydrophobic antimicrobial peptide by vesicle capture-freeze-drying: a preparatory method coupled to ion mobility-mass spectrometry.

    Science.gov (United States)

    Patrick, John W; Gamez, Roberto C; Russell, David H

    2015-01-06

    A novel sample preparation method to probe the solution phase structure of dimerized Gramicidin A (GA) inserted into lipid vesicle bilayers is described. This method, termed vesicle capture-freeze-drying (VCFD), when coupled with electrospray ionization-ion mobility-mass spectrometry (ESI-IM-MS), successfully demonstrates the first evidence for the preservation of membrane-bound structure in the analysis of solution phase conformers retained into the gas phase. The extremely hydrophobic character of GA ensures that only membrane-bound conformations are captured and subsequently monitored when samples are prepared using VCFD, removing a barrier that has prevented previous attempts at direct analysis using mass spectrometry. Solution-phase physicochemical interactions of GA influenced by lipid acyl chain length and extent of acyl chain unsaturation can now be probed by monitoring the conformer preferences using IM-MS. Increasing the acyl chain length from 12 to 22 carbons yields [2GA + 2Na](2+) IM-MS profiles with reduced conformer microheterogeneity. POPC (16:0, 18:1 PC), a lipid possessing a single acyl chain unsaturation point, yields the highest abundance of the single stranded head to head (SSHH) conformer. Conformer preferences adopted in the lipid bilayer are maintained as GA dimers travel from the solution phase to fully desolvated gas-phase ions demonstrating that distributions observed using ESI-IM-MS unambiguously reflect the ensemble of conformers observed in the solution phase. VCFD-ESI-IM-MS yields novel biophysical insight into the influence of lipid bilayer membranes on conformer preferences and conformer heterogeneity of an important channel-forming membrane peptide.

  7. Tough Supramolecular Hydrogel Based on Strong Hydrophobic Interactions in a Multiblock Segmented Copolymer

    Science.gov (United States)

    2017-01-01

    We report the preparation and structural and mechanical characterization of a tough supramolecular hydrogel, based exclusively on hydrophobic association. The system consists of a multiblock, segmented copolymer of hydrophilic poly(ethylene glycol) (PEG) and hydrophobic dimer fatty acid (DFA) building blocks. A series of copolymers containing 2K, 4K, and 8K PEG were prepared. Upon swelling in water, a network is formed by self-assembly of hydrophobic DFA units in micellar domains, which act as stable physical cross-link points. The resulting hydrogels are noneroding and contain 75–92 wt % of water at swelling equilibrium. Small-angle neutron scattering (SANS) measurements showed that the aggregation number of micelles ranges from 2 × 102 to 6 × 102 DFA units, increasing with PEG molecular weight. Mechanical characterization indicated that the hydrogel containing PEG 2000 is mechanically very stable and tough, possessing a tensile toughness of 4.12 MJ/m3. The high toughness, processability, and ease of preparation make these hydrogels very attractive for applications where mechanical stability and load bearing features of soft materials are required. PMID:28469284

  8. Ion/neutral, ion/electron, ion/photon, and ion/ion interactions in tandem mass spectrometry: do we need them all? Are they enough?

    Science.gov (United States)

    McLuckey, Scott A; Mentinova, Marija

    2011-01-01

    A range of strategies and tools have been developed to facilitate the determination of primary structures of analyte molecules of interest via tandem mass spectrometry (MS/MS). The two main factors that determine the primary structural information present in an MS/MS spectrum are the type of ion generated from the analyte molecule and the dissociation method. The ion type subjected to dissociation is determined by the ionization method/conditions and ion transformation processes that might take place after initial gas-phase ion formation. Furthermore, the range of analyte-related ion types can be expanded via derivatization reactions prior to mass spectrometry. Dissociation methods include those that simply alter the population of internal states of the mass-selected ion (i.e., activation methods like collision-induced dissociation) as well as processes that rely on the transformation of the ion type prior to dissociation (e.g., electron capture dissociation). A variety of ion interactions have been studied for the purpose of ion dissociation and ion transformation, including ion/neutral, ion/photon, ion/electron, and ion/ion interactions. A wide range of phenomena have been observed, many of which have been explored/developed as means for structural analysis. The techniques arising from these phenomena are discussed within the context of the elements of structural determination in tandem mass spectrometry: ion-type definition and dissociation. Unique aspects of the various ion interactions are emphasized along with any barriers to widespread implementation. © American Society for Mass Spectrometry, 2011

  9. A Hydrophobic Pocket in the Active Site of Glycolytic Aldolase Mediates Interactions with Wiskott-Aldrich Syndrome Protein

    Energy Technology Data Exchange (ETDEWEB)

    St-Jean,M.; Izard, T.; Sygusch, J.

    2007-01-01

    Aldolase plays essential catalytic roles in glycolysis and gluconeogenesis. However, aldolase is a highly abundant protein that is remarkably promiscuous in its interactions with other cellular proteins. In particular, aldolase binds to highly acidic amino acid sequences, including the C-terminus of the Wiskott-Aldrich syndrome protein, an actin nucleation promoting factor. Here we report the crystal structure of tetrameric rabbit muscle aldolase in complex with a C-terminal peptide of Wiskott-Aldrich syndrome protein. Aldolase recognizes a short, 4-residue DEWD motif (residues 498-501), which adopts a loose hairpin turn that folds about the central aromatic residue, enabling its tryptophan side chain to fit into a hydrophobic pocket in the active site of aldolase. The flanking acidic residues in this binding motif provide further interactions with conserved aldolase active site residues, Arg-42 and Arg-303, aligning their side chains and forming the sides of the hydrophobic pocket. The binding of Wiskott-Aldrich syndrome protein to aldolase precludes intramolecular interactions of its C-terminus with its active site, and is competitive with substrate as well as with binding by actin and cortactin. Finally, based on this structure a novel naphthol phosphate-based inhibitor of aldolase was identified and its structure in complex with aldolase demonstrated mimicry of the Wiskott-Aldrich syndrome protein-aldolase interaction. The data support a model whereby aldolase exists in distinct forms that regulate glycolysis or actin dynamics.

  10. Ion beam modification of solids ion-solid interaction and radiation damage

    CERN Document Server

    Wesch, Werner

    2016-01-01

    This book presents the method of ion beam modification of solids in realization, theory and applications in a comprehensive way. It provides a review of the physical basics of ion-solid interaction and on ion-beam induced structural modifications of solids. Ion beams are widely used to modify the physical properties of materials. A complete theory of ion stopping in matter and the calculation of the energy loss due to nuclear and electronic interactions are presented including the effect of ion channeling. To explain structural modifications due to high electronic excitations, different concepts are presented with special emphasis on the thermal spike model. Furthermore, general concepts of damage evolution as a function of ion mass, ion fluence, ion flux and temperature are described in detail and their limits and applicability are discussed. The effect of nuclear and electronic energy loss on structural modifications of solids such as damage formation, phase transitions and amorphization is reviewed for ins...

  11. Interaction between Low Energy Ions and the Complicated Organism

    Science.gov (United States)

    Yu, Zeng-liang

    1999-12-01

    Low energy ions exist widely in natural world, but people pay a little attention on the interaction between low energy ions and matter, it is even more out of the question of studying on the relation of low energy ions and the complicated organism. The discovery of bioeffect induced by ion implantation has, however, opened a new branch in the field of ion beam application in life sciences. This paper reports recent advances in research on the role of low energy ions in chemical synthesis of the biomolecules and application in genetic modification.

  12. Positron Interactions with Atoms and Ions

    Science.gov (United States)

    Bhatia, Anand K.

    2012-01-01

    Dirac, in 1928, combining the ideas of quantum mechanics and the ideas of relativity invented the well-known relativistic wave equation. In his formulation, he predicted an antiparticle of the electron of spin n-bar/2. He thought that this particle must be a proton. Dirac published his interpretation in a paper 'A theory of electrons and protons.' It was shown later by the mathematician Hermann Weyl that the Dirac theory was completely symmetric between negative and positive particles and the positive particle must have the same mass as that of the electron. In his J. Robert Oppenheimer Memorial Prize Acceptance Speech, Dirac notes that 'Blackett was really the first person to obtain hard evidence for the existence of a positron but he was afraid to publish it. He wanted confirmation, he was really over cautious.' Positron, produced by the collision of cosmic rays in a cloud chamber, was detected experimentally by Anderson in 1932. His paper was published in Physical Review in 1933. The concept of the positron and its detection were the important discoveries of the 20th century. I have tried to discuss various processes involving interactions of positrons with atoms and ions. This includes scattering, bound states and resonances. It has not been possible to include the enormous work which has been carried out during the last 40 or 50 years in theory and measurements.

  13. Key aromatic/hydrophobic amino acids controlling a cross-amyloid peptide interaction versus amyloid self-assembly.

    Science.gov (United States)

    Bakou, Maria; Hille, Kathleen; Kracklauer, Michael; Spanopoulou, Anna; Frost, Christina V; Malideli, Eleni; Yan, Li-Mei; Caporale, Andrea; Zacharias, Martin; Kapurniotu, Aphrodite

    2017-09-01

    The interaction of the intrinsically disordered polypeptide islet amyloid polypeptide (IAPP), which is associated with type 2 diabetes (T2D), with the Alzheimer's disease amyloid-β (Aβ) peptide modulates their self-assembly into amyloid fibrils and may link the pathogeneses of these two cell-degenerative diseases. However, the molecular determinants of this interaction remain elusive. Using a systematic alanine scan approach, fluorescence spectroscopy, and other biophysical methods, including heterocomplex pulldown assays, far-UV CD spectroscopy, the thioflavin T binding assay, transmission EM, and molecular dynamics simulations, here we identified single aromatic/hydrophobic residues within the amyloid core IAPP region as hot spots or key residues of its cross-interaction with Aβ40(42) peptide. Importantly, we also find that none of these residues in isolation plays a key role in IAPP self-assembly, whereas simultaneous substitution of four aromatic/hydrophobic residues with Ala dramatically impairs both IAPP self-assembly and hetero-assembly with Aβ40(42). Furthermore, our experiments yielded several novel IAPP analogs, whose sequences are highly similar to that of IAPP but have distinct amyloid self- or cross-interaction potentials. The identified similarities and major differences controlling IAPP cross-peptide interaction with Aβ40(42) versus its amyloid self-assembly offer a molecular basis for understanding the underlying mechanisms. We propose that these insights will aid in designing intervention strategies and novel IAPP analogs for the management of type 2 diabetes, Alzheimer's disease, or other diseases related to IAPP dysfunction or cross-amyloid interactions. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  14. Simple Physics-Based Analytical Formulas for the Potentials of Mean Force of the Interaction of Amino Acid Side Chains in Water. VII. Charged-Hydrophobic/Polar and Polar-Hydrophobic/Polar Side Chains.

    Science.gov (United States)

    Makowski, Mariusz; Liwo, Adam; Scheraga, Harold A

    2017-01-19

    The physics-based potentials of side-chain-side-chain interactions corresponding to pairs composed of charged and polar, polar and polar, charged and hydrophobic, and hydrophobic and hydrophobic side chains have been determined. A total of 144 four-dimensional potentials of mean force (PMFs) of all possible pairs of molecules modeling these pairs were determined by umbrella-sampling molecular dynamics simulations in explicit water as functions of distance and orientation, and the analytical expressions were then fitted to the PMFs. Depending on the type of interacting sites, the analytical approximation to the PMF is a sum of terms corresponding to van der Waals interactions and cavity-creation involving the nonpolar sections of the side chains and van der Waals, cavity-creation, and electrostatic (charge-dipole or dipole-dipole) interaction energies and polarization energies involving the charged or polar sections of the side chains. The model used in this work reproduces all features of the interacting pairs. The UNited RESidue force field with the new side-chain-side-chain interaction potentials was preliminarily tested with the N-terminal part of the B-domain of staphylococcal protein A (PDBL 1BDD ; a three-α-helix bundle) and UPF0291 protein YnzC from Bacillus subtilis (PDB: 2HEP ; an α-helical hairpin).

  15. Evaporation of Drops Containing Silica Nanoparticles of Varying Hydrophobicities: Exploiting Particle-Particle Interactions for Additive-Free Tunable Deposit Morphology.

    Science.gov (United States)

    Anyfantakis, Manos; Baigl, Damien; Binks, Bernard P

    2017-05-23

    We describe the systematic and quantitative investigation of a large number of patterns that emerge after the evaporation of aqueous drops containing fumed silica nanoparticles (NPs) of varying wettabilities for an extended particle concentration range. We show that for a chosen system, the dry pattern morphology is mainly determined by particle-particle interactions (Coulomb repulsion and hydrophobic attraction) in the bulk. These depend on both particle hydrophobicity and particle concentration within the drop. For high and intermediate particle concentrations, interparticle hydrophobic attraction is the dominant factor defining the deposit morphology. With increasing particle hydrophobicity, patterns ranging from rings to domes are observed, arising from the time needed for the drop to gel compared with the total evaporation time. On the contrary, drops of dilute suspensions maintain a finite viscosity during most of the drop lifetime, resulting in dry patterns that are predominantly rings for all particle hydrophobicities. In all investigated systems, the NP concentration corresponded to a large excess of NPs in the bulk compared with the maximal amount that could be adsorbed at available interfaces, making particle-interface interactions such as adsorption of hydrophobic NPs at the air-water interface a negligible contribution over bulk particle-particle interactions. This work emphasizes the advantage of particle surface chemistry in tuning both particle-particle interactions and particle deposition onto solid substrates in a robust manner, without the need for any additive such as a surfactant.

  16. Modulation and interactions of charged biomimetic membranes with bivalent ions

    Science.gov (United States)

    Kazadi Badiambile, Adolphe

    The biological membrane of an eukaryotic cell is a two-dimensional structure of mostly phospholipids with embedded proteins. This two-dimensional structure plays many key roles in the life of a cell. Transmembrane proteins, for example, play the role of a gate for different ions (such as Ca2+). Also found are peripheral proteins that are used as enzymes for different purposes in the inner leaflet of the plasma membrane. Phospholipids, in particular play three key roles. Firstly, some members of this group are used to store energy. Secondly, the hydrophobic and hydrophilic properties inherent to phospholipids enable them to be used as building blocks of the cell membrane by forming an asymmetric bilayer. This provides a shielding protection against the outer environment while at the same time keeping the organelles and cytosol from leaking out of the cell. Finally lipids are involved in regulating the aggregation of proteins in the membrane. In addition, some subspecies such as phosphatidylinositol (PtdIns) are second messenger molecules in their own right, thus playing an important role in cellular signaling events. In my work presented in this thesis, I am focusing on the role of some phospholipids as signaling molecules and in particular the physicochemical underpinnings that could be used in their spatiotemporal organization in the cellular plasma membrane. I am specifically concerned with the important family of phosphatidylinositol lipids. PtdIns are very well known for their role as signaling molecules in numerous cell events. They are located in the inner leaflet of the plasma membrane as well as part of the membrane of other organelles. Studies of these signaling molecules in their in vivo environment present many challenges: Firstly, the complexity of interactions due to the numerous entities present in eukaryotic cell membranes makes it difficult to establish clear cause and effect relationships. Secondly, due to their size, our inability to probe these

  17. Ion-dipole interactions in concentrated organic electrolytes.

    Science.gov (United States)

    Chagnes, Alexandre; Nicolis, Stamatios; Carré, Bernard; Willmann, Patrick; Lemordant, Daniel

    2003-06-16

    An algorithm is proposed for calculating the energy of ion-dipole interactions in concentrated organic electrolytes. The ion-dipole interactions increase with increasing salt concentration and must be taken into account when the activation energy for the conductivity is calculated. In this case, the contribution of ion-dipole interactions to the activation energy for this transport process is of the same order of magnitude as the contribution of ion-ion interactions. The ion-dipole interaction energy was calculated for a cell of eight ions, alternatingly anions and cations, placed on the vertices of an expanded cubic lattice whose parameter is related to the mean interionic distance (pseudolattice theory). The solvent dipoles were introduced randomly into the cell by assuming a randomness compacity of 0.58. The energy of the dipole assembly in the cell was minimized by using a Newton-Raphson numerical method. The dielectric field gradient around ions was taken into account by a distance parameter and a dielectric constant of epsilon = 3 at the surfaces of the ions. A fair agreement between experimental and calculated activation energy has been found for systems composed of gamma-butyrolactone (BL) as solvent and lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) as salts.

  18. Lateral Protein-Protein Interactions at Hydrophobic and Charged Surfaces as a Function of pH and Salt Concentration.

    Science.gov (United States)

    Hladílková, Jana; Callisen, Thomas H; Lund, Mikael

    2016-04-07

    Surface adsorption of Thermomyces lanuginosus lipase (TLL)-a widely used industrial biocatalyst-is studied experimentally and theoretically at different pH and salt concentrations. The maximum achievable surface coverage on a hydrophobic surface occurs around the protein isoelectric point and adsorption is reduced when either increasing or decreasing pH, indicating that electrostatic protein-protein interactions in the adsorbed layer play an important role. Using Metropolis Monte Carlo (MC) simulations, where proteins are coarse grained to the amino acid level, we estimate the protein isoelectric point in the vicinity of charged surfaces as well as the lateral osmotic pressure in the adsorbed monolayer. Good agreement with available experimental data is achieved and we further make predictions of the protein orientation at hydrophobic and charged surfaces. Finally, we present a perturbation theory for predicting shifts in the protein isoelectric point due to close proximity to charged surfaces. Although this approximate model requires only single protein properties (mean charge and its variance), excellent agreement is found with MC simulations.

  19. The Non-Specific Binding of Fluorescent-Labeled MiRNAs on Cell Surface by Hydrophobic Interaction

    Science.gov (United States)

    Ren, Jianwei; Yao, Peng; Wang, Xiaowei; Wang, Zhe; Zhang, Qunye

    2016-01-01

    Background MicroRNAs are small noncoding RNAs about 22 nt long that play key roles in almost all biological processes and diseases. The fluorescent labeling and lipofection are two common methods for changing the levels and locating the position of cellular miRNAs. Despite many studies about the mechanism of DNA/RNA lipofection, little is known about the characteristics, mechanisms and specificity of lipofection of fluorescent-labeled miRNAs. Methods and Results Therefore, miRNAs labeled with different fluorescent dyes were transfected into adherent and suspension cells using lipofection reagent. Then, the non-specific binding and its mechanism were investigated by flow cytometer and laser confocal microscopy. The results showed that miRNAs labeled with Cy5 (cyanine fluorescent dye) could firmly bind to the surface of adherent cells (Hela) and suspended cells (K562) even without lipofection reagent. The binding of miRNAs labeled with FAM (carboxyl fluorescein) to K562 cells was obvious, but it was not significant in Hela cells. After lipofectamine reagent was added, most of the fluorescently labeled miRNAs binding to the surface of Hela cells were transfected into intra-cell because of the high transfection efficiency, however, most of them were still binding to the surface of K562 cells. Moreover, the high-salt buffer which could destroy the electrostatic interactions did not affect the above-mentioned non-specific binding, but the organic solvent which could destroy the hydrophobic interactions eliminated it. Conclusions These results implied that the fluorescent-labeled miRNAs could non-specifically bind to the cell surface by hydrophobic interaction. It would lead to significant errors in the estimation of transfection efficiency only according to the cellular fluorescence intensity. Therefore, other methods to evaluate the transfection efficiency and more appropriate fluorescent dyes should be used according to the cell types for the accuracy of results. PMID

  20. The Non-Specific Binding of Fluorescent-Labeled MiRNAs on Cell Surface by Hydrophobic Interaction.

    Directory of Open Access Journals (Sweden)

    Ting Lu

    Full Text Available MicroRNAs are small noncoding RNAs about 22 nt long that play key roles in almost all biological processes and diseases. The fluorescent labeling and lipofection are two common methods for changing the levels and locating the position of cellular miRNAs. Despite many studies about the mechanism of DNA/RNA lipofection, little is known about the characteristics, mechanisms and specificity of lipofection of fluorescent-labeled miRNAs.Therefore, miRNAs labeled with different fluorescent dyes were transfected into adherent and suspension cells using lipofection reagent. Then, the non-specific binding and its mechanism were investigated by flow cytometer and laser confocal microscopy. The results showed that miRNAs labeled with Cy5 (cyanine fluorescent dye could firmly bind to the surface of adherent cells (Hela and suspended cells (K562 even without lipofection reagent. The binding of miRNAs labeled with FAM (carboxyl fluorescein to K562 cells was obvious, but it was not significant in Hela cells. After lipofectamine reagent was added, most of the fluorescently labeled miRNAs binding to the surface of Hela cells were transfected into intra-cell because of the high transfection efficiency, however, most of them were still binding to the surface of K562 cells. Moreover, the high-salt buffer which could destroy the electrostatic interactions did not affect the above-mentioned non-specific binding, but the organic solvent which could destroy the hydrophobic interactions eliminated it.These results implied that the fluorescent-labeled miRNAs could non-specifically bind to the cell surface by hydrophobic interaction. It would lead to significant errors in the estimation of transfection efficiency only according to the cellular fluorescence intensity. Therefore, other methods to evaluate the transfection efficiency and more appropriate fluorescent dyes should be used according to the cell types for the accuracy of results.

  1. Comparison of entropic contributions to binding in a "hydrophilic" versus "hydrophobic" ligand-protein interaction.

    Science.gov (United States)

    Syme, Neil R; Dennis, Caitriona; Bronowska, Agnieszka; Paesen, Guido C; Homans, Steve W

    2010-06-30

    In the present study we characterize the thermodynamics of binding of histamine to recombinant histamine-binding protein (rRaHBP2), a member of the lipocalin family isolated from the brown-ear tick Rhipicephalus appendiculatus. The binding pocket of this protein contains a number of charged residues, consistent with histamine binding, and is thus a typical example of a "hydrophilic" binder. In contrast, a second member of the lipocalin family, the recombinant major urinary protein (rMUP), binds small hydrophobic ligands, with a similar overall entropy of binding in comparison with rRaHBP2. Having extensively studied ligand binding thermodynamics for rMUP previously, the data we obtained in the present study for HBP enables a comparison of the driving forces for binding between these classically distinct binding processes in terms of entropic contributions from ligand, protein, and solvent. In the case of rRaHBP2, we find favorable entropic contributions to binding from desolvation of the ligand; however, the overall entropy of binding is unfavorable due to a dominant unfavorable contribution arising from the loss of ligand degrees of freedom, together with the sequestration of solvent water molecules into the binding pocket in the complex. This contrasts with binding in rMUP where desolvation of the protein binding pocket makes a minor contribution to the overall entropy of binding given that the pocket is substantially desolvated prior to binding.

  2. Epitope mapping of imidazolium cations in ionic liquid-protein interactions unveils the balance between hydrophobicity and electrostatics towards protein destabilisation.

    Science.gov (United States)

    Silva, Micael; Figueiredo, Angelo Miguel; Cabrita, Eurico J

    2014-11-14

    We investigated imidazolium-based ionic liquid (IL) interactions with human serum albumin (HSA) to discern the level of cation interactions towards protein stability. STD-NMR spectroscopy was used to observe the imidazolium IL protons involved in direct binding and to identify the interactions responsible for changes in Tm as accessed by differential scanning calorimetry (DSC). Cations influence protein stability less than anions but still significantly. It was found that longer alkyl side chains of imidazolium-based ILs (more hydrophobic) are associated with a higher destabilisation effect on HSA than short-alkyl groups (less hydrophobic). The reason for such destabilisation lies on the increased surface contact area of the cation with the protein, particularly on the hydrophobic contacts promoted by the terminus of the alkyl chain. The relevance of the hydrophobic contacts is clearly demonstrated by the introduction of a polar moiety in the alkyl chain: a methoxy or alcohol group. Such structural modification reduces the degree of hydrophobic contacts with HSA explaining the lesser extent of protein destabilisation when compared to longer alkyl side chain groups: above [C2mim](+). Competition STD-NMR experiments using [C2mim](+), [C4mim](+) and [C2OHmim](+) also validate the importance of the hydrophobic interactions. The combined effect of cation and anion interactions was explored using (35)Cl NMR. Such experiments show that the nature of the cation has no influence on the anion-protein contacts, still the nature of the anion modulates the cation-protein interaction. Herein we propose that more destabilising anions are likely to be a result of a partial contribution from the cation as a direct consequence of the different levels of interaction (cation-anion pair and cation-protein).

  3. Synthesis of Fe3O4-ZnS/AgInS2 composite nanoparticles using a hydrophobic interaction.

    Science.gov (United States)

    Choi, Kang Sik; Bang, Bo Keuk; Bae, Pan Kee; Kim, Yong-Rok; Kim, Chang Hae

    2013-03-01

    Magnetic nanoparticles and fluorescent quantum dots (QDs) can make many effective applications in biomedical system. Here, we demonstrated one way of synthetic method and its surface modification to use for biomedical applications. Fe3O4 nanoparticles are well known as magnetic materials and its magnetic property can be used in magnetic resonance imaging (MRI), cell detection. QDs as a fluorescent probes, make cell labeling and in vivo imaging possible. ZnS/AgInS2 QDs have a lower toxicity than other QDs (CdSe, CdTe, CdS). We combined two nanoparticles by hydrophobic interaction in their ligands. The prepared fluorescent magnetic composite particles were modified with CTAB-TEOS. The surface modified composite has a low cytotoxicity and these biocompatible particles will provide many possibilities in biomedical system.

  4. Aggregation of non-polar solutes in water at different pressures and temperatures: the role of hydrophobic interaction.

    Science.gov (United States)

    Ferrara, C Gastón; Chara, Osvaldo; Grigera, J Raúl

    2012-10-07

    Due to the importance of the hydrophobic interaction in protein folding, we decided to study the effect of pressure and temperature on the phase transitions of non-polar solutes in water, and thereby their solubility, using molecular dynamics simulations. The main results are: (1) within a certain range, temperature induces the aggregation of Lennard-Jones particles in water; and (2) pressure induces disaggregation of the formed clusters. From the simulated data, a non-monotonic coexistence curve for the binary system was obtained, from which a critical point of T(c) = 383 ± 9 K and p(c) = 937 ± 11 bar was determined. The results are in accordance with previous experimental evidence involving transitions of hydrocarbons in water mixtures, and protein unfolding.

  5. Interaction of bovine serum albumin with N-acyl amino acid based anionic surfactants: Effect of head-group hydrophobicity.

    Science.gov (United States)

    Ghosh, Subhajit; Dey, Joykrishna

    2015-11-15

    The function of a protein depends upon its structure and surfactant molecules are known to alter protein structure. For this reason protein-surfactant interaction is important in biological, pharmaceutical, and cosmetic industries. In the present work, interactions of a series of anionic surfactants having the same hydrocarbon chain length, but different amino acid head group, such as l-alanine, l-valine, l-leucine, and l-phenylalanine with the transport protein, bovine serum albumin (BSA), were studied at low surfactant concentrations using fluorescence and circular dichroism (CD) spectroscopy, and isothermal titration calorimetry (ITC). The results of fluorescence measurements suggest that the surfactant molecules bind simultaneously to the drug binding site I and II of the protein subdomain IIA and IIIA, respectively. The fluorescence as well as CD spectra suggest that the conformation of BSA goes to a more structured state upon surfactant binding at low concentrations. The binding constants of the surfactants were determined by the use of fluorescence as well as ITC measurements and were compared with that of the corresponding glycine-derived surfactant. The binding constant values clearly indicate a significant head-group effect on the BSA-surfactant interaction and the interaction is mainly hydrophobic in nature. Copyright © 2015 Elsevier Inc. All rights reserved.

  6. A dock and coalesce mechanism driven by hydrophobic interactions governs Cdc42 binding with its effector protein ACK.

    Science.gov (United States)

    Tetley, George J N; Mott, Helen R; Cooley, R Neil; Owen, Darerca

    2017-07-07

    Cdc42 is a Rho-family small G protein that has been widely studied for its role in controlling the actin cytoskeleton and plays a part in several potentially oncogenic signaling networks. Similar to most other small G proteins, Cdc42 binds to many downstream effector proteins to elicit its cellular effects. These effector proteins all engage the same face of Cdc42, the conformation of which is governed by the activation state of the G protein. Previously, the importance of individual residues in conferring binding affinity has been explored for residues within Cdc42 for three of its Cdc42/Rac interactive binding (CRIB) effectors, activated Cdc42 kinase (ACK), p21-activated kinase (PAK), and Wiskott-Aldrich syndrome protein (WASP). Here, in a complementary study, we have used our structure of Cdc42 bound to ACK via an intrinsically disordered ACK region to guide an analysis of the Cdc42 interface on ACK, creating a panel of mutant proteins with which we can now describe the complete energetic landscape of the Cdc42-binding site on ACK. Our data suggest that the binding affinity of ACK relies on several conserved residues that are critical for stabilizing the quaternary structure. These residues are centered on the CRIB region, with the complete binding region anchored at each end by hydrophobic interactions. These findings suggest that ACK adopts a dock and coalesce binding mechanism with Cdc42. In contrast to other CRIB-family effectors and indeed other intrinsically disordered proteins, hydrophobic residues likely drive Cdc42-ACK binding. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  7. Rational design of viscosity reducing mutants of a monoclonal antibody: hydrophobic versus electrostatic inter-molecular interactions.

    Science.gov (United States)

    Nichols, Pilarin; Li, Li; Kumar, Sandeep; Buck, Patrick M; Singh, Satish K; Goswami, Sumit; Balthazor, Bryan; Conley, Tami R; Sek, David; Allen, Martin J

    2015-01-01

    High viscosity of monoclonal antibody formulations at concentrations ≥100 mg/mL can impede their development as products suitable for subcutaneous delivery. The effects of hydrophobic and electrostatic intermolecular interactions on the solution behavior of MAB 1, which becomes unacceptably viscous at high concentrations, was studied by testing 5 single point mutants. The mutations were designed to reduce viscosity by disrupting either an aggregation prone region (APR), which also participates in 2 hydrophobic surface patches, or a negatively charged surface patch in the variable region. The disruption of an APR that lies at the interface of light and heavy chain variable domains, VH and VL, via L45K mutation destabilized MAB 1 and abolished antigen binding. However, mutation at the preceding residue (V44K), which also lies in the same APR, increased apparent solubility and reduced viscosity of MAB 1 without sacrificing antigen binding or thermal stability. Neutralizing the negatively charged surface patch (E59Y) also increased apparent solubility and reduced viscosity of MAB 1, but charge reversal at the same position (E59K/R) caused destabilization, decreased solubility and led to difficulties in sample manipulation that precluded their viscosity measurements at high concentrations. Both V44K and E59Y mutations showed similar increase in apparent solubility. However, the viscosity profile of E59Y was considerably better than that of the V44K, providing evidence that inter-molecular interactions in MAB 1 are electrostatically driven. In conclusion, neutralizing negatively charged surface patches may be more beneficial toward reducing viscosity of highly concentrated antibody solutions than charge reversal or aggregation prone motif disruption.

  8. Organic sorbate-organoclay interactions in aqueous and hydrophobic environments: sorbate-water competition.

    Science.gov (United States)

    Borisover, Mikhail; Gerstl, Zev; Burshtein, Faina; Yariv, Shmuel; Mingelgrin, Uri

    2008-10-01

    Sorption of nitrobenzene, phenol, and m-nitrophenol from water and n-hexadecane was measured on Na-montmorillonite and organoclays in which 41 and 90% of the exchange capacity of the Na-clay was occupied by hexadecyltrimethylammonium. The strength of sorbate-sorbent interactions in n-hexadecane for all three sorbents was in the following order: nitrobenzene organoclays is minor, whereas the major contribution is from adsorptive sorbate-sorbent interactions. Sorption isotherms obtained in different solvents were compared using a sorbate activity scale. In the organoclays, the stronger the tendency of a sorbate to interact with sorption sites, the less pronounced is the reduction in the activity-based sorption due to competition with water. The order of this reduction for the different sorbates is nitrobenzene > phenol > m-nitrophenol. The weakening of sorbate-sorbent interactions resulting from water-sorbate competition might be mitigated by interaction between the organic sorbate and sorbed water molecules. Since the more strongly interacting organic compounds are less susceptible to suppression of sorption in the presence of water, hydrating organoclays may result in an increased differentiation between "weakly" and "strongly" interacting ("nonpolar" and "polar") compounds in the organoclay phase.

  9. Hydrophobic environment is a key factor for the stability of thermophilic proteins.

    Science.gov (United States)

    Gromiha, M Michael; Pathak, Manish C; Saraboji, Kadhirvel; Ortlund, Eric A; Gaucher, Eric A

    2013-04-01

    The stability of thermophilic proteins has been viewed from different perspectives and there is yet no unified principle to understand this stability. It would be valuable to reveal the most important interactions for designing thermostable proteins for such applications as industrial protein engineering. In this work, we have systematically analyzed the importance of various interactions by computing different parameters such as surrounding hydrophobicity, inter-residue interactions, ion-pairs and hydrogen bonds. The importance of each interaction has been determined by its predicted relative contribution in thermophiles versus the same contribution in mesophilic homologues based on a dataset of 373 protein families. We predict that hydrophobic environment is the major factor for the stability of thermophilic proteins and found that 80% of thermophilic proteins analyzed showed higher hydrophobicity than their mesophilic counterparts. Ion pairs, hydrogen bonds, and interaction energy are also important and favored in 68%, 50%, and 62% of thermophilic proteins, respectively. Interestingly, thermophilic proteins with decreased hydrophobic environments display a greater number of hydrogen bonds and/or ion pairs. The systematic elimination of mesophilic proteins based on surrounding hydrophobicity, interaction energy, and ion pairs/hydrogen bonds, led to correctly identifying 95% of the thermophilic proteins in our analyses. Our analysis was also applied to another, more refined set of 102 thermophilic-mesophilic pairs, which again identified hydrophobicity as a dominant property in 71% of the thermophilic proteins. Further, the notion of surrounding hydrophobicity, which characterizes the hydrophobic behavior of residues in a protein environment, has been applied to the three-dimensional structures of elongation factor-Tu proteins and we found that the thermophilic proteins are enriched with a hydrophobic environment. The results obtained in this work highlight the

  10. Coumarins as new matrices for matrix-assisted laser-desorption/ionization Fourier transform ion cyclotron resonance mass spectrometric analysis of hydrophobic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hang, E-mail: hangwang@sjtu.edu.cn [Instrumental Analysis Center, Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240 (China); Dai, Bona [Instrumental Analysis Center, Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240 (China); Liu, Bin [Key Laboratory of Kidney Disease Pathogenesis and Intervention of Hubei Province, College of Medicine, Hubei Polytechnic University, Huangshi, Hubei 435003 (China); Lu, Han [Department of Anesthesiology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine (SJTU-SM), 197, Rui Jin Er Road, Shanghai 200025 (China)

    2015-07-02

    Highlights: • Coumarins were used as new MALDI matrices. • Coumarins were used for MALDI-FT ICR MS detection of hydrophobic compounds. • DCA had improvement in detection sensitivity, stability, selectivity and reproducibility. • DCA was applied to sterols detection in yeast cells. - Abstract: Hydrophobic compounds with hydroxyl, aldehyde or ketone groups are generally difficult to detect using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), because these compounds have low proton affinity and are poorly ionized by MALDI. Herein, coumarins have been used as new matrices for MALDI-MS analysis of a variety of hydrophobic compounds with low ionization efficiency, including steroids, coenzyme Q10, a cyclic lipopeptide and cholesterol oleate. Five coumarins, including coumarin, umbelliferone, esculetin, 7-hydroxycoumarin-3-carboxylic acid (HCA) and 6,7-dihydroxycoumarin-3-carboxylic acid (DCA), were compared with the conventional matrices of 2,5-dihydroxybenzoic acid (DHB) and α-cyano-4-hydroxycinnamic acid (CHCA). Coumarins with hydroxyl or carboxylic acid groups enabled detection. Taking DCA as an example, this matrix proved to be superior to DHB or CHCA in detection sensitivity, stability, spot-to-spot and sample-to-sample reproducibility, and accuracy. DCA increased the stability of the target compounds and decreased the loss of water. The [M + Na]{sup +} peaks were observed for all target compounds by adding NaCl as an additive, and the [M − H{sub 2}O + H]{sup +} and [M + H]{sup +} peaks decreased. DCA was selected for the identification of sterols in yeast cells, and thirteen sterols were detected by Fourier transform ion cyclotron resonance (FT ICR) mass spectrometry. This work demonstrates the potential of DCA as a new matrix for detection of hydrophobic molecules by MALDI-MS and provides an alternative tool for screening sterols in antifungal research.

  11. Nuclear import of cutaneous beta genus HPV8 E7 oncoprotein is mediated by hydrophobic interactions between its zinc-binding domain and FG nucleoporins

    Energy Technology Data Exchange (ETDEWEB)

    Onder, Zeynep; Moroianu, Junona, E-mail: moroianu@bc.edu

    2014-01-20

    We have previously discovered and characterized the nuclear import pathways for the E7 oncoproteins of mucosal alpha genus HPVs, type 16 and 11. Here we investigated the nuclear import of cutaneous beta genus HPV8 E7 protein using confocal microscopy after transfections of HeLa cells with EGFP-8E7 and mutant plasmids and nuclear import assays in digitonin-permeabilized HeLa cells. We determined that HPV8 E7 contains a nuclear localization signal (NLS) within its zinc-binding domain that mediates its nuclear import. Furthermore, we discovered that a mostly hydrophobic patch {sub 65}LRLFV{sub 69} within the zinc-binding domain is essential for the nuclear import and localization of HPV8 E7 via hydrophobic interactions with the FG nucleoporins Nup62 and Nup153. Substitution of the hydrophobic residues within the {sub 65}LRLFV{sub 69} patch to alanines, and not R66A mutation, disrupt the interactions between the 8E7 zinc-binding domain and Nup62 and Nup153 and consequently inhibit nuclear import of HPV8 E7. - Highlights: • HPV8 E7 has a cNLS within its zinc-binding domain that mediates its nuclear import. • Discovery of a hydrophobic patch that is critical for the nuclear import of HPV8 E7. • HPV8 E7 nuclear import is mediated by hydrophobic interactions with FG-Nups, Nup62 and Nup153.

  12. Relationship between hydrophobic interactions and secondary structure stability for Trpzip beta-hairpin peptides.

    Science.gov (United States)

    Takekiyo, Takahiro; Wu, Ling; Yoshimura, Yukihiro; Shimizu, Akio; Keiderling, Timothy A

    2009-02-24

    The temperature-induced beta-hairpin stabilities of selected mutations of the Trpzip1 peptide, SWTWEGNKWTWK (WWWW), have been investigated by electronic circular dichroism (CD), Raman, and FT-IR spectroscopies. The tryptophan (Trp) residues in the original Trpzip1 sequence were systematically substituted with tyrosine (Tyr) in different positions to test the impact of Trp interactions on the beta-hairpin structure and stability. The CD intensity at approximately 228 nm, which arises from Trp-Trp interactions (tertiary structure), and the amide I' IR absorbance at approximately 1635 cm(-1) (secondary structure) have been measured over a range of temperatures to investigate the impact of Tyr substitution on beta-hairpin thermal stability in Trpzip peptides. Mutation from Trp to Tyr in the Trpzip1 sequence reduces the extent of beta-hairpin structure and monotonically decreases the beta-hairpin stability of Trpzip1 mutant peptides with an increasing number of Tyr substitutions. Substituted Trpzip peptides with just one pair of Trp-Trp interactions close to either the terminal residues (WYYW) or the turn (YWWY) have similar stabilities. Comparison of conformational transitions monitored by CD and IR reveals them to have multistate behavior in which the temperature-induced disruption of the Trp-Trp interaction (tertiary structure) occurs at a lower temperature than the unfolding of the secondary structure.

  13. Surface modification of hydrophobic polymers for improvement of endothelial cell-surface interactions

    NARCIS (Netherlands)

    Dekker, A.; Dekker, A.; Reitsma, K.; Beugeling, T.; Beugeling, T.; Bantjes, A.; Bantjes, A.; Feijen, Jan; Kirkpatrick, C.J.; van Aken, W.G.

    1992-01-01

    The aim of this study is to improve the interaction of endothelial cells with polymers used in vascular prostheses. Polytetrafluoroethylene (PTFE; Teflon) films were treated by means of nitrogen and oxygen plasmas. Depending on the plasma exposure time, modified PTFE surfaces showed water-contact

  14. Preparation of a novel weak cation exchange/hydrophobic interaction chromatography dual-function polymer-based stationary phase for protein separation using "thiol-ene click chemistry".

    Science.gov (United States)

    Yang, Fan; Bai, Quan; Zhao, Kailou; Gao, Dong; Tian, Lei

    2015-02-01

    A novel dual-function mixed-mode stationary phase based on poly(glycidyl methacrylate-co-ethylene dimethacrylate) microspheres was synthesized by thiol-ene click chemistry and characterized by infrared spectroscopy and elemental analysis. The new system displays both hydrophobic interaction chromatography (HIC) character in a high salt concentration mobile phase, and weak cation exchange (WCX) chromatography character in a low salt concentration mobile phase. It can be used to separate proteins in both ion-exchange chromatography (IEC) mode and HIC mode. The resolution and selectivity of the stationary phase were evaluated in both HIC mode and IEC mode using protein standards. In comparison with the conventional WCX and HIC columns, the results were satisfactory and acceptable. Protein mass and bioactivity recoveries of more than 96% can be achieved in both HIC mode and IEC mode using this column. The results indicate that the novel dual-function mixed-mode column in many cases can replace the use of two individual WCX and HIC columns. In addition, the effects on protein separation of different ligand structures in the dual-function stationary phase and the pH of the mobile phase used were also investigated in detail. The results show that electrostatic interaction of the ligand with proteins must match the hydrophobicity of the ligand, which is an important factor to prepare the dual-function stationary phase. On the basis of this dual-function mixed-mode chromatography column, a new two-dimensional liquid chromatography technology with a single column system was also developed in this study, and was used to renature and purify recombinant human interferon-γ from inclusion bodies. The mass recovery, purity, and specific bioactivity obtained for the purified recombinant human interferon-γ were 87.2%, 92.4%, and 2.8 × 10(7) IU/mg, respectively, in IEC mode, and 83.4%, 95.2%, and 4.3 × 10(7) IU/mg, respectively, in HIC mode. The results indicate that the

  15. Solid-state structure of gelatin-mono epoxy terminated polydimethylsiloxane polymer: effect of electrostatic and hydrophobic interactions.

    Science.gov (United States)

    Xu, Jing; Xia, Yongmei; Qiao, Cong-De; Zhu, Weiyue; Wang, Yuexia; Li, Tian-Duo

    2014-11-01

    In this study, a hybrid synthetic gelatin-mono epoxy terminated polydimethylsiloxane polymer (PDMS-E grafted gelatin (PGG)) was successfully synthesized on a large scale. Supramolecular structure of gelatin, which was decided by the sophisticated inter- and intra-molecular interactions, significantly affected the self-assembly and phase behavior of PGG. Interestingly, the supramolecular organization of PGG could be tuned finely by negatively charged surfactants, such as sodium dodecyl sulfate (SDS) and sodium tetradecyl sulfonate (STSo), as revealed by high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), light microscopy (LM), and atomic force microscopy (AFM). SEM images exhibited the presence of spherical aggregates in PGG/SDS films while hexagonal array was observed in PGG/STSo films. The results of LM revealed that when PGG/STSo solution was dried, a successive structural transformation from spheres to hexagons, via sticks and butterfly-shaped aggregates as intermediates, was observed. However, the morphologies of the aggregates formed in PGG/SDS system did not exhibit any obvious change upon drying. Attenuated total reflection-Fourier transform infrared spectra combined with AFM observations indicated that the secondary structure and aggregation behavior of gelatin was modified with the change in the electrostatic and hydrophobic interactions, leading to the formation of diversified solid-state structures of PGG. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Slow ions in plasma wind tunnels. [satellite-ionosphere interaction

    Science.gov (United States)

    Oran, W. A.; Stone, N. H.; Samir, U.

    1976-01-01

    One of the limitations of simulation experiments for the study of interaction between a satellite and its space environment is the background of slow ions in the plasma chamber. These ions appear to be created by charge exchange between the beam ions and residual neutral gas and may affect measurements of the current and potential in the wake. Results are presented for a plasma wind tunnel experiment to study the effect of slow ions on both the ion and electron current distribution and the electron temperature in the wake of a body in a streaming plasma. It is shown that the effect of slow ions for beam ion density not exceeding 3 is not significant for measurements of ion current variations in the wake zone. This is not the case when studies are aimed at the quantitative examination of electron current and temperature variations in the near wake zone. In these instances, the measurements of electron properties in the wake should be done at very low system pressures or over a range of system pressures in order to ascertain the influence of slow ions.

  17. Beamlet interaction in multi-aperture negative ion source

    Energy Technology Data Exchange (ETDEWEB)

    Fujiwara, Yukio; Hanada, Masaya; Kawai, Kenichi; Kitagawa, Tadashi; Miyamoto, Kenji; Okumura, Yoshikazu; Watanabe, Kazuhiro [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment

    1999-02-01

    Beamlet interaction, which may deteriorate beam convergence, was studied in a high-current negative ion beam composed of multiple beamlets. Experimental results demonstrated that a deflection angle of beamlets at the edge of a beam was larger than that at the center of a beam, because of space charge effect. The deflection angle was independent of the beam energy ranging from 86 keV to 178 keV at the same perveance. Effect of electrons accompanying negative ions was confirmed to be negligible. It was shown that repulsive force due to space charge effect was inversely proportional to the square of distance. The maximum deflection angle of a large negative ion source for the JT-60 Negative ion-NBI system was estimated to be about 6.6 mrad based on the obtained results. Shaping of a grid was proposed to compensate the beamlet interaction. Beam orbit simulations indicated the effectiveness of the shaping. (author)

  18. Hydrophobic properties of high Fe3+ ion containing Fe2O3-TiO2 coatings

    Science.gov (United States)

    Zukuls, A.; Mezinskis, G.

    2017-10-01

    The treatment of environmental pollution using semiconductor photo catalysis converts contaminants to innocuous products, such as CO2 and H2O. The most promising semiconductor photo catalysts are titania based materials. However, the main drawback of titania anatase polymorph is the large band gap which limits the spectrum of photons that can create electron–hole pairs to participate in oxidation or reduction. In this study Fe2O3–TiO2 coatings were successfully prepared on soda-lime silicate glass slide substrates using sol–gel method. Coating surface and morphology has been studied using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). Coatings were obtained using dip-coating method. The present research is devoted to the studies of aging time and heat treatment effects on films hydrophobicity. The purpose of this contribution was the development of iron oxide rich Fe2O3–TiO2 hydrophobic thin films depending on different preparation parameters. SEM and AFM investigation revealed the formation of two layered, porous coating microstructure consisting of rough flattened areas which formed the backbone for irregularly shaped particles.

  19. Anionic and cationic Hofmeister effects on hydrophobic and hydrophilic surfaces.

    Science.gov (United States)

    Schwierz, Nadine; Horinek, Dominik; Netz, Roland R

    2013-02-26

    Using a two-step modeling approach, we address the full spectrum of direct, reversed, and altered ionic sequences as the charge of the ion, the charge of the surface, and the surface polarity are varied. From solvent-explicit molecular dynamics simulations, we extract single-ion surface interaction potentials for halide and alkali ions at hydrophilic and hydrophobic surfaces. These are used within Poisson-Boltzmann theory to calculate ion density and electrostatic potential distributions at mixed polar/unpolar surfaces for varying surface charge. The resulting interfacial tension increments agree quantitatively with experimental data and capture the Hofmeister series, especially the anomaly of lithium, which is difficult to obtain using continuum theory. Phase diagrams that feature different Hofmeister series as a function of surface charge, salt concentration, and surface polarity are constructed from the long-range force between two surfaces interacting across electrolyte solutions. Large anions such as iodide have a high hydrophobic surface affinity and increase the effective charge magnitude on negatively charged unpolar surfaces. Large cations such as cesium also have a large hydrophobic surface affinity and thereby compensate an external negative charge surface charge most efficiently, which explains the well-known asymmetry between cations and anions. On the hydrophilic surface, the size-dependence of the ion surface affinity is reversed, explaining the Hofmeister series reversal when comparing hydrophobic with hydrophilic surfaces.

  20. Cation-Anion Interactions within the Nucleic Acid Ion Atmosphere Revealed by Ion Counting.

    Science.gov (United States)

    Gebala, Magdalena; Giambaşu, George M; Lipfert, Jan; Bisaria, Namita; Bonilla, Steve; Li, Guangchao; York, Darrin M; Herschlag, Daniel

    2015-11-25

    The ion atmosphere is a critical structural, dynamic, and energetic component of nucleic acids that profoundly affects their interactions with proteins and ligands. Experimental methods that "count" the number of ions thermodynamically associated with the ion atmosphere allow dissection of energetic properties of the ion atmosphere, and thus provide direct comparison to theoretical results. Previous experiments have focused primarily on the cations that are attracted to nucleic acid polyanions, but have also showed that anions are excluded from the ion atmosphere. Herein, we have systematically explored the properties of anion exclusion, testing the zeroth-order model that anions of different identity are equally excluded due to electrostatic repulsion. Using a series of monovalent salts, we find, surprisingly, that the extent of anion exclusion and cation inclusion significantly depends on salt identity. The differences are prominent at higher concentrations and mirror trends in mean activity coefficients of the electrolyte solutions. Salts with lower activity coefficients exhibit greater accumulation of both cations and anions within the ion atmosphere, strongly suggesting that cation-anion correlation effects are present in the ion atmosphere and need to be accounted for to understand electrostatic interactions of nucleic acids. To test whether the effects of cation-anion correlations extend to nucleic acid kinetics and thermodynamics, we followed the folding of P4-P6, a domain of the Tetrahymena group I ribozyme, via single-molecule fluorescence resonance energy transfer in solutions with different salts. Solutions of identical concentration but lower activity gave slower and less favorable folding. Our results reveal hitherto unknown properties of the ion atmosphere and suggest possible roles of oriented ion pairs or anion-bridged cations in the ion atmosphere for electrolyte solutions of salts with reduced activity. Consideration of these new results leads to

  1. Cation–Anion Interactions within the Nucleic Acid Ion Atmosphere Revealed by Ion Counting

    Science.gov (United States)

    Gebala, Magdalena; Giambasu, George M.; Lipfert, Jan; Bisaria, Namita; Bonilla, Steve; Li, Guangchao; York, Darrin M.; Herschlag, Daniel

    2016-01-01

    The ion atmosphere is a critical structural, dynamic, and energetic component of nucleic acids that profoundly affects their interactions with proteins and ligands. Experimental methods that “count” the number of ions thermodynamically associated with the ion atmosphere allow dissection of energetic properties of the ion atmosphere, and thus provide direct comparison to theoretical results. Previous experiments have focused primarily on the cations that are attracted to nucleic acid polyanions, but have also showed that anions are excluded from the ion atmosphere. Herein, we have systematically explored the properties of anion exclusion, testing the zeroth-order model that anions of different identity are equally excluded due to electrostatic repulsion. Using a series of monovalent salts, we find, surprisingly, that the extent of anion exclusion and cation inclusion significantly depends on salt identity. The differences are prominent at higher concentrations and mirror trends in mean activity coefficients of the electrolyte solutions. Salts with lower activity coefficients exhibit greater accumulation of both cations and anions within the ion atmosphere, strongly suggesting that cation–anion correlation effects are present in the ion atmosphere and need to be accounted for to understand electrostatic interactions of nucleic acids. To test whether the effects of cation–anion correlations extend to nucleic acid kinetics and thermodynamics, we followed the folding of P4–P6, a domain of the Tetrahymena group I ribozyme, via single-molecule fluorescence resonance energy transfer in solutions with different salts. Solutions of identical concentration but lower activity gave slower and less favorable folding. Our results reveal hitherto unknown properties of the ion atmosphere and suggest possible roles of oriented ion pairs or anion-bridged cations in the ion atmosphere for electrolyte solutions of salts with reduced activity. Consideration of these new

  2. Mean force potential of interaction between Na+ and Cl- ions in planar nanopores in contact with water under pressure

    Science.gov (United States)

    Shevkunov, S. V.

    2017-11-01

    The mean force potential (MFP) of interaction between counterions Na+ and Cl- in a planar nanopore with structureless hydrophobic walls is calculated via computer simulation under the condition that the nanopore is in contact with water at an external pressure that exceeds the saturation pressure but remains insufficient to fill the nanopore with water. For a nanopore with a liquid phase, the MFP dependence on the interionic distance indicates the dissociation of an ion pair into two hydrated ions in a nanopore that is not completely filled with water. Fluctuations in the number of water molecules drawn into the interionic space decisively influence the dissociation. The attraction between counterions, averaged over thermal fluctuations, depends largely on the pore width and grows as the shielding of the ions' electric field by water molecules in a narrow pore diminishes. The contributions from energy and entropy to the free energy of hydration are analyzed.

  3. A new class of organogelators based on triphenylmethyl derivatives of primary alcohols: hydrophobic interactions alone can mediate gelation.

    Science.gov (United States)

    Singh, Wangkhem P; Singh, Rajkumar S

    2017-01-01

    In the present work, we have explored the use of the triphenylmethyl group, a commonly used protecting group for primary alcohols as a gelling structural component in the design of molecular gelators. We synthesized a small library of triphenylmethyl derivatives of simple primary alcohols and studied their gelation properties in different solvents. Gelation efficiency for some of the derivatives was moderate to excellent with a minimum gelation concentration ranging between 0.5-4.0% w/v and a gel-sol transition temperature range of 31-75 °C. 1,8-Bis(trityloxy)octane, the ditrityl derivative of 1,8-octanediol was the most efficient organogelator. Detailed characterizations of the gel were carried out using scanning electron microscopy, FTIR spectroscopy, rheology and powder XRD techniques. This gel also showed a good absorption profile for a water soluble dye. Given the non-polar nature of this molecule, gel formation is likely to be mediated by hydrophobic interactions between the triphenylmethyl moieties and alkyl chains. Possible self-assembled packing arrangements in the gel state for 1,8-bis(trityloxy)octane and (hexadecyloxymethanetriyl)tribenzene are presented. Results from this study strongly indicate that triphenylmethyl group is a promising gelling structural unit which may be further exploited in the design of small molecule based gelators.

  4. Optimization of non-linear gradient in hydrophobic interaction chromatography for the analytical characterization of antibody-drug conjugates.

    Science.gov (United States)

    Bobály, Balázs; Randazzo, Giuseppe Marco; Rudaz, Serge; Guillarme, Davy; Fekete, Szabolcs

    2017-01-20

    The goal of this work was to evaluate the potential of non-linear gradients in hydrophobic interaction chromatography (HIC), to improve the separation between the different homologous species (drug-to-antibody, DAR) of commercial antibody-drug conjugates (ADC). The selectivities between Brentuximab Vedotin species were measured using three different gradient profiles, namely linear, power function based and logarithmic ones. The logarithmic gradient provides the most equidistant retention distribution for the DAR species and offers the best overall separation of cysteine linked ADC in HIC. Another important advantage of the logarithmic gradient, is its peak focusing effect for the DAR0 species, which is particularly useful to improve the quantitation limit of DAR0. Finally, the logarithmic behavior of DAR species of ADC in HIC was modelled using two different approaches, based on i) the linear solvent strength theory (LSS) and two scouting linear gradients and ii) a new derived equation and two logarithmic scouting gradients. In both cases, the retention predictions were excellent and systematically below 3% compared to the experimental values. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. A new class of organogelators based on triphenylmethyl derivatives of primary alcohols: hydrophobic interactions alone can mediate gelation

    Directory of Open Access Journals (Sweden)

    Wangkhem P. Singh

    2017-01-01

    Full Text Available In the present work, we have explored the use of the triphenylmethyl group, a commonly used protecting group for primary alcohols as a gelling structural component in the design of molecular gelators. We synthesized a small library of triphenylmethyl derivatives of simple primary alcohols and studied their gelation properties in different solvents. Gelation efficiency for some of the derivatives was moderate to excellent with a minimum gelation concentration ranging between 0.5–4.0% w/v and a gel–sol transition temperature range of 31–75 °C. 1,8-Bis(trityloxyoctane, the ditrityl derivative of 1,8-octanediol was the most efficient organogelator. Detailed characterizations of the gel were carried out using scanning electron microscopy, FTIR spectroscopy, rheology and powder XRD techniques. This gel also showed a good absorption profile for a water soluble dye. Given the non-polar nature of this molecule, gel formation is likely to be mediated by hydrophobic interactions between the triphenylmethyl moieties and alkyl chains. Possible self-assembled packing arrangements in the gel state for 1,8-bis(trityloxyoctane and (hexadecyloxymethanetriyltribenzene are presented. Results from this study strongly indicate that triphenylmethyl group is a promising gelling structural unit which may be further exploited in the design of small molecule based gelators.

  6. One-step synthesis of layered yttrium hydroxides in immiscible liquid-liquid systems: Intercalation of sterically-bulky hydrophobic organic anions and doping of europium ions

    Science.gov (United States)

    Watanabe, Mebae; Fujihara, Shinobu

    2014-02-01

    Inorganic-organic layered rare-earth compounds were synthesized on the basis of a biphasic liquid-liquid system in one pot. Layered yttrium hydroxides (LYHs) were chosen as a host material for the intercalation of hydrophobic organic guest anions such as benzoate, sebacate, or laurate. In a typical synthesis, an organic phase dissolving carboxylic acid was placed in contact with an equal amount of an aqueous phase dissolving yttrium nitrate n-hydrate and urea. At elevated temperatures up to 80 °C, urea was hydrolyzed to release hydroxyl anions which were used to form yttrium hydroxide layers. LYHs were then precipitated with the intercalation of carboxylate anions delivered from the organic phase under the distribution law. The structure and the morphology of the LYHs could be modulated by the intercalated anions. Doped with Eu3+ ions, the LYHs exhibited red photoluminescence which was enhanced by the intercalated anions due to the antenna effect.

  7. A Single-Ion Trap with Minimized Ion-Environment Interactions

    CERN Document Server

    Nisbet-Jones, P B R; Jones, J M; Godun, R M; Baynham, C F A; Bongs, K; Doležal, M; Balling, P; Gill, P

    2015-01-01

    We present a new single-ion endcap trap for high precision spectroscopy that has been designed to minimize ion-environment interactions. We describe the design in detail and then characterize the working trap using a single trapped 171 Yb ion. Excess micromotion has been eliminated to the resolution of the detection method and the trap exhibits an anomalous phonon heating rate of d /dt = 24 +30/-24 per second. The thermal properties of the trap structure have also been measured with an effective temperature rise at the ion's position of 0.14 +/- 0.14 K. The small perturbations to the ion caused by this trap make it suitable to be used for an optical frequency standard with fractional uncertainties below the 10^-18 level.

  8. One-step synthesis of layered yttrium hydroxides in immiscible liquid–liquid systems: Intercalation of sterically-bulky hydrophobic organic anions and doping of europium ions

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Mebae; Fujihara, Shinobu, E-mail: shinobu@applc.keio.ac.jp

    2014-02-15

    Inorganic–organic layered rare-earth compounds were synthesized on the basis of a biphasic liquid–liquid system in one pot. Layered yttrium hydroxides (LYHs) were chosen as a host material for the intercalation of hydrophobic organic guest anions such as benzoate, sebacate, or laurate. In a typical synthesis, an organic phase dissolving carboxylic acid was placed in contact with an equal amount of an aqueous phase dissolving yttrium nitrate n-hydrate and urea. At elevated temperatures up to 80 °C, urea was hydrolyzed to release hydroxyl anions which were used to form yttrium hydroxide layers. LYHs were then precipitated with the intercalation of carboxylate anions delivered from the organic phase under the distribution law. The structure and the morphology of the LYHs could be modulated by the intercalated anions. Doped with Eu{sup 3+} ions, the LYHs exhibited red photoluminescence which was enhanced by the intercalated anions due to the antenna effect. - Graphical abstract: The Eu{sup 3+}-doped layered yttrium hydroxide exhibits intense red photoluminescence after intercalation of benzoate ions. Display Omitted - Highlights: • Immiscible biphasic liquid systems were introduced to synthesize layered yttrium hydroxides. • The temperature of the biphasic systems does not exceed 80 °C in one step of the synthesis. • Hydrophobic organic anions were intercalated between the hydroxide layers in one pot. • Structure and morphology of the hydroxides were modulated by changing the kind of organic anions. • Eu{sup 3+}-doping led to red luminescence from the hydroxides in association with the intercalated organic anions.

  9. Fundamentals of ion-solid interaction. A compact introduction

    Energy Technology Data Exchange (ETDEWEB)

    Moeller, Wolfhard [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany). Inst. of Ion Beam Physics and Materials Research

    2017-09-01

    Since Rutherford's famous paper which first described the scattering of α-particles in matter, the field of ion-solid interaction has matured by now during one entire century. First theoretical concepts addressing particle penetration of solids were given by Thomson and Bohr. Quantum theory entered the field in treatments of ion stopping by Born and Bethe. Still on classical grounds, transport theory was first introduced in a paper on multiple scattering by Bothe. The discovery of nuclear fission launched theoretical studies by Bohr on the scattering and stopping of fission products. A further milestone in the understanding of particle penetration phenomena is the 1948 paper by Bohr. On this basis, the theoretical understanding was enhanced in the early 1960's in particular by a series of papers by Lindhard. Simultaneously, an increasing amount of experimental studies on ion stopping and scattering were launched in connection with the development of ion acceleration devices and corresponding equipment for particle detection. During this period, also first computer simulation studies came up which later proved to be an utmost efficient tool for the description of collisional phenomena in ion-solid interaction. The relevance for numerous applications became evident, such as for the compositional and structural analysis of thin films and near-surface layers, for semiconductor technology, and nuclear fission and fusion technology. This caused increasing interest not only in the penetration and the scattering of the impinging ions, but also in the modification of the irradiated material due to ion implantation, radiation damage and surface erosion by sputtering. Consequently, ion-solid interaction established around 1970 internationally as a quickly expanding field at the intersection of solid-state physics and nuclear physics. Numerous reviews and textbooks are available which cover the fundamentals of ion-solid interaction. Torrens reviewed the knowledge

  10. Cooperative Noncovalent Interactions Induce Ion Pair Separation in Diphenylsilanides.

    Science.gov (United States)

    Marro, Eric A; Press, Eric M; Purkait, Tapas K; Jimenez, Daniel; Siegler, Maxime A; Klausen, Rebekka S

    2017-11-07

    This crystallographic and computational study describes an unusual potassium silanide structure. A contact ion pair is expected in the solid state between potassium and silicon, yet the potassium cation binds an aromatic ring and the anionic silanide interacts with CH bonds on neighboring crown ether molecules. These structure-bonding phenomena are attributed to strong soft-soft interactions. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Two dimensional simulation of ion beam-plasm interaction | Echi ...

    African Journals Online (AJOL)

    Journal of the Nigerian Association of Mathematical Physics ... Abstract. Hybrid plasma simulation is a model in which different components of the plasma are treated differently. ... Deuterium ion beams incident on the tritium plasma interact with the plasma through the wake electric and magnetic fields of the beam currents.

  12. The Role of Hydrophobicity and Surface Receptors at Hyphae of Lyophyllum sp. Strain Karsten in the Interaction with Burkholderia terrae BS001 – Implications for Interactions in Soil

    Science.gov (United States)

    Vila, Taissa; Nazir, Rashid; Rozental, Sonia; dos Santos, Giulia M. P.; Calixto, Renata O. R.; Barreto-Bergter, Eliana; Wick, Lukas Y.; van Elsas, Jan Dirk

    2016-01-01

    The soil bacterium Burkholderia terrae strain BS001 can interact with varying soil fungi, using mechanisms that range from the utilization of carbon/energy sources such as glycerol to the ability to reach novel territories in soil via co-migration with growing fungal mycelia. Here, we investigate the intrinsic properties of the B. terrae BS001 interaction with the basidiomycetous soil fungus Lyophyllum sp. strain Karsten. In some experiments, the ascomycetous Trichoderma asperellum 302 was also used. The hyphae of Lyophyllum sp. strain Karsten were largely hydrophilic on water-containing media versus hydrophobic when aerial, as evidenced by contact angle analyses (CA). Co-migration of B. terrae strain BS001 cells with the hyphae of the two fungi occurred preferentially along the - presumably hydrophilic - soil-dwelling hyphae, whereas aerial hyphae did not allow efficient migration, due to reduced thickness of their surrounding mucous films. Moreover, the cell numbers over the length of the hyphae in soil showed an uneven distribution, i.e., the CFU numbers increased from minima at the inoculation point to maximal numbers in the middle of the extended hyphae, then decreasing toward the terminal side. Microscopic analyses of the strain BS001 associations with the Lyophyllum sp. strain Karsten hyphae in the microcosms confirmed the presence of B. terrae BS001 cells on the mucous matter that was present at the hyphal surfaces of the fungi used. Cell agglomerates were found to accumulate at defined sites on the hyphal surfaces, which were coined ‘fungal-interactive’ hot spots. Evidence was further obtained for the contention that receptors for a physical bacterium-fungus interaction occur at the Lyophyllum sp. strain Karsten hyphal surface, in which the specific glycosphingolipid ceramide monohexoside (CMH) plays an important role. Thus, bacterial adherence may be mediated by heterogeneously distributed fungal-specific receptors, implying the CMH moieties. This

  13. Four faces of the interaction between ions and aromatic rings.

    Science.gov (United States)

    Papp, Dóra; Rovó, Petra; Jákli, Imre; Császár, Attila G; Perczel, András

    2017-07-15

    Non-covalent interactions between ions and aromatic rings play an important role in the stabilization of macromolecular complexes; of particular interest are peptides and proteins containing aromatic side chains (Phe, Trp, and Tyr) interacting with negatively (Asp and Glu) and positively (Arg and Lys) charged amino acid residues. The structures of the ion-aromatic-ring complexes are the result of an interaction between the large quadrupole moment of the ring and the charge of the ion. Four attractive interaction types are proposed to be distinguished based on the position of the ion with respect to the plane of the ring: perpendicular cation-π (CP⊥ ), co-planar cation-π (CP∥ ), perpendicular anion-π (AP⊥ ), and co-planar anion-π (AP∥ ). To understand more than the basic features of these four interaction types, a systematic, high-level quantum chemical study is performed, using the X-  + C6 H6 , M+  + C6 H6 , X-  + C6 F6 , and M+  + C6 F6 model systems with X-  = H- , F- , Cl- , HCOO- , CH3 COO- and M+  = H+ , Li+ , Na+ , NH4+, CH3 NH3+, whereby C6 H6 and C6 F6 represent an electron-rich and an electron-deficient π system, respectively. Benchmark-quality interaction energies with small uncertainties, obtained via the so-called focal-point analysis (FPA) technique, are reported for the four interaction types. The computations reveal that the interactions lead to significant stabilization, and that the interaction energy order, given in kcal mol-1 in parentheses, is CP⊥ (23-37) > AP⊥ (14-21) > CP∥ (9-22) > AP∥ (6-16). A natural bond orbital analysis performed leads to a deeper qualitative understanding of the four interaction types. To facilitate the future quantum chemical characterization of ion-aromatic-ring interactions in large biomolecules, the performance of three density functional theory methods, B3LYP, BHandHLYP, and M06-2X, is tested against the FPA benchmarks, with the result that the M06-2X

  14. Simultaneous determination of ionic and neutral preservatives by inline dialysis-ion chromatography coupled with a hydrophobic-ion exchange mixed mode column.

    Science.gov (United States)

    Nakashima, Yasuo; Suzuki, Seiichi; Yamazaki, Makiko; Inoue, Yoshinori; Fukatsu, Yuta; Yamamoto, Atsushi

    2011-01-01

    A quantitative analysis was developed for eight acidic and neutral preservatives in foods and daily necessities using the inline dialysis-IC combined with hydrophobic anion-exchange separation. The eight preservatives were dialyzed by inline dialysis and separated on a hydrophobic anion exchange column. Under the optimized separation conditions, the detection limits (S/N = 3) for the eight preservatives were from 0.08 to 0.66 mg L(-1), moreover, a good linearity (R(2) > 0.998) for each preservative was obtained in the range to 100 mg L(-1). Although the dialysis rate of the neutral preservatives was not so high, a good repeatability (RSD, n = 8) of less than 1.5% for the eight preservatives was obtained. The inline dialysis-IC method was applied to the determination of the preservatives in foods and daily necessities. The preservatives were quantified without any interference. The proposed method will be useful for the determination of the preservatives in foods and daily necessities containing high concentration matrices. 2011 © The Japan Society for Analytical Chemistry

  15. Cerato-populin and cerato-platanin, two non-catalytic proteins from phytopathogenic fungi, interact with hydrophobic inanimate surfaces and leaves.

    Science.gov (United States)

    Martellini, Federica; Faoro, Franco; Carresi, Lara; Pantera, Barbara; Baccelli, Ivan; Maffi, Dario; Tiribilli, Bruno; Sbrana, Francesca; Luti, Simone; Comparini, Cecilia; Bernardi, Rodolfo; Cappugi, Gianni; Scala, Aniello; Pazzagli, Luigia

    2013-09-01

    Based on sequence homology, several fungal Cys-rich secreted proteins have been grouped in the cerato-platanin (CP) family, which comprises at least 40 proteins involved mainly in eliciting defense-related responses. The core member of this family is cerato-platanin, a moderately hydrophobic protein with a double ψ-β barrel fold. CP and the recently identified orthologous cerato-populin (Pop1) are involved in host-fungus interaction, and can be considered non-catalytic fungal PAMPs. CP is more active in inducing defense when in an aggregated conformation than in its native form, but little is known about other CP-orthologous proteins. Here, we cloned, expressed, and purified recombinant Pop1, which was used to characterize the protein aggregates. Our results suggest that the unfolded, self-assembled Pop1 is more active in inducing defense, and that the unfolding process can be induced by interaction with hydrophobic inanimate surfaces such as Teflon, treated mica, and gold sheets. In vivo, we found that both CP and Pop1 interact with the hydrophobic cuticle of leaves. Therefore, we propose that the interaction of these proteins with host cuticle waxes could induce unfolding and consequently trigger their PAMP-like activity.

  16. Semi-automated hydrophobic interaction chromatography column scouting used in the two-step purification of recombinant green fluorescent protein.

    Science.gov (United States)

    Stone, Orrin J; Biette, Kelly M; Murphy, Patrick J M

    2014-01-01

    Hydrophobic interaction chromatography (HIC) most commonly requires experimental determination (i.e., scouting) in order to select an optimal chromatographic medium for purifying a given target protein. Neither a two-step purification of untagged green fluorescent protein (GFP) from crude bacterial lysate using sequential HIC and size exclusion chromatography (SEC), nor HIC column scouting elution profiles of GFP, have been previously reported. Bacterial lysate expressing recombinant GFP was sequentially adsorbed to commercially available HIC columns containing butyl, octyl, and phenyl-based HIC ligands coupled to matrices of varying bead size. The lysate was fractionated using a linear ammonium phosphate salt gradient at constant pH. Collected HIC eluate fractions containing retained GFP were then pooled and further purified using high-resolution preparative SEC. Significant differences in presumptive GFP elution profiles were observed using in-line absorption spectrophotometry (A395) and post-run fluorimetry. SDS-PAGE and western blot demonstrated that fluorometric detection was the more accurate indicator of GFP elution in both HIC and SEC purification steps. Comparison of composite HIC column scouting data indicated that a phenyl ligand coupled to a 34 µm matrix produced the highest degree of target protein capture and separation. Conducting two-step protein purification using the preferred HIC medium followed by SEC resulted in a final, concentrated product with >98% protein purity. In-line absorbance spectrophotometry was not as precise of an indicator of GFP elution as post-run fluorimetry. These findings demonstrate the importance of utilizing a combination of detection methods when evaluating purification strategies. GFP is a well-characterized model protein, used heavily in educational settings and by researchers with limited protein purification experience, and the data and strategies presented here may aid in development other of HIC-compatible protein

  17. Semi-Automated Hydrophobic Interaction Chromatography Column Scouting Used in the Two-Step Purification of Recombinant Green Fluorescent Protein

    Science.gov (United States)

    Murphy, Patrick J. M.

    2014-01-01

    Background Hydrophobic interaction chromatography (HIC) most commonly requires experimental determination (i.e., scouting) in order to select an optimal chromatographic medium for purifying a given target protein. Neither a two-step purification of untagged green fluorescent protein (GFP) from crude bacterial lysate using sequential HIC and size exclusion chromatography (SEC), nor HIC column scouting elution profiles of GFP, have been previously reported. Methods and Results Bacterial lysate expressing recombinant GFP was sequentially adsorbed to commercially available HIC columns containing butyl, octyl, and phenyl-based HIC ligands coupled to matrices of varying bead size. The lysate was fractionated using a linear ammonium phosphate salt gradient at constant pH. Collected HIC eluate fractions containing retained GFP were then pooled and further purified using high-resolution preparative SEC. Significant differences in presumptive GFP elution profiles were observed using in-line absorption spectrophotometry (A395) and post-run fluorimetry. SDS-PAGE and western blot demonstrated that fluorometric detection was the more accurate indicator of GFP elution in both HIC and SEC purification steps. Comparison of composite HIC column scouting data indicated that a phenyl ligand coupled to a 34 µm matrix produced the highest degree of target protein capture and separation. Conclusions Conducting two-step protein purification using the preferred HIC medium followed by SEC resulted in a final, concentrated product with >98% protein purity. In-line absorbance spectrophotometry was not as precise of an indicator of GFP elution as post-run fluorimetry. These findings demonstrate the importance of utilizing a combination of detection methods when evaluating purification strategies. GFP is a well-characterized model protein, used heavily in educational settings and by researchers with limited protein purification experience, and the data and strategies presented here may aid in

  18. Ion interactions with non-polar and amphiphilic solutes in water.

    Science.gov (United States)

    Bowron, D T; Finney, J L

    2013-01-01

    Despite its extensive use in, for example, the concentration and crystallization of proteins, the salting out phenomenon remains poorly understood, with many--sometimes contradictory--explanations found in the literature. Following our earlier work using isotope substitution neutron scattering on an aqueous tertiary butyl alcohol (TBA) with added NaCl that examined in detail the molecular-level interactions in the system, and suggested that attempts to understand salting out through ion perturbation of the non-polar hydration shell may not be appropriate, we report here on two further sets of high resolution structural experiments that detail the structural interactions between ion, solvent and amphiphile in a wider range of relevant systems. First, a set of X-ray absorption spectroscopy experiments probed the effects on the hydrophobic hydration shell of Kr of adding a range of different salts (specifically Na2SO4, NaClO4, NaCl, NaNO3 and Mg(ClO4)2). The bottom line from these experiments is that the hydration shell is essentially unaffected by the added ions, underlining further the stability of the shell to such perturbations. The second set of experiments was a further isotope substitution neutron scattering study of the molecular-level solution structures of aqueous TBA, this time for a range of different added ions (CsF, NaBr, and NaCl at three concentrations), for which we have in addition extracted equilibrium constants to quantify the relative strengths of the various interactions. From this second set of results, we can conclude again that the solvent structure is essentially unperturbed by both the various ions and the amphiphile, and also identify a number of ion-specific effects. Comparing our results with those obtained from simulations that are not constrained by the experimental data underlines how sensitive structural conclusions are to the assumed potential functions, and that drawing conclusions from simulations not constrained to fit

  19. High-Resolution Coarse-Grained Model of Hydrated Anion-Exchange Membranes that Accounts for Hydrophobic and Ionic Interactions through Short-Ranged Potentials.

    Science.gov (United States)

    Lu, Jibao; Jacobson, Liam C; Perez Sirkin, Yamila A; Molinero, Valeria

    2017-01-10

    Molecular simulations provide a versatile tool to study the structure, anion conductivity, and stability of anion-exchange membrane (AEM) materials and can provide a fundamental understanding of the relation between structure and property of membranes that is key for their use in fuel cells and other applications. The quest for large spatial and temporal scales required to model the multiscale structure and transport processes in the polymer electrolyte membranes, however, cannot be met with fully atomistic models, and the available coarse-grained (CG) models suffer from several challenges associated with their low-resolution. Here, we develop a high-resolution CG force field for hydrated polyphenylene oxide/trimethylamine chloride (PPO/TMACl) membranes compatible with the mW water model using a hierarchical parametrization approach based on Uncertainty Quantification and reference atomistic simulations modeled with the Generalized Amber Force Field (GAFF) and TIP4P/2005 water. The parametrization weighs multiple properties, including coordination numbers, radial distribution functions (RDFs), self-diffusion coefficients of water and ions, relative vapor pressure of water in the solution, hydration enthalpy of the tetramethylammonium chloride (TMACl) salt, and cohesive energy of its aqueous solutions. We analyze the interdependence between properties and address how to compromise between the accuracies of the properties to achieve an overall best representability. Our optimized CG model FFcomp quantitatively reproduces the diffusivities and RDFs of the reference atomistic model and qualitatively reproduces the experimental relative vapor pressure of water in solutions of tetramethylammonium chloride. These properties are of utmost relevance for the design and operation of fuel cell membranes. To our knowledge, this is the first CG model that includes explicitly each water and ion and accounts for hydrophobic, ionic, and intramolecular interactions explicitly

  20. INTERACTION REGION DESIGN FOR THE ELECTRON-ION COLLIDER ERHIC.

    Energy Technology Data Exchange (ETDEWEB)

    MONTAG, C.; PARKER, B.; TEPIKIAN, S.; ET AL.

    2005-05-16

    To facilitate the study of collisions between 10 GeV polarized electrons and 100 GeV/u heavy ions or 250 GeV polarized protons at luminosities in the 10{sup 33} cm{sup -2} sec{sup -1} range (e-p case), adding a 10 GeV electron storage ring to the existing RHIC complex has been proposed. The interaction region of this electron-ion collider eRHIC has to provide the required low-beta focusing, while simultaneously accommodating the synchrotron radiation fan generated by beam separation close to the interaction point, which is particularly challenging. The latest design status of the eRHIC interaction region will be presented.

  1. Explaining Ionic Liquid Water Solubility in Terms of Cation and Anion Hydrophobicity

    Science.gov (United States)

    Ranke, Johannes; Othman, Alaa; Fan, Ping; Müller, Anja

    2009-01-01

    The water solubility of salts is ordinarily dictated by lattice energy and ion solvation. However, in the case of low melting salts also known as ionic liquids, lattice energy is immaterial and differences in hydrophobicity largely account for differences in their water solubility. In this contribution, the activity coefficients of ionic liquids in water are split into cation and anion contributions by regression against cation hydrophobicity parameters that are experimentally determined by reversed phase liquid chromatography. In this way, anion hydrophobicity parameters are derived, as well as an equation to estimate water solubilities for cation-anion combinations for which the water solubility has not been measured. Thus, a new pathway to the quantification of aqueous ion solvation is shown, making use of the relative weakness of interactions between ionic liquid ions as compared to their hydrophobicities. PMID:19399248

  2. Explaining ionic liquid water solubility in terms of cation and anion hydrophobicity.

    Science.gov (United States)

    Ranke, Johannes; Othman, Alaa; Fan, Ping; Müller, Anja

    2009-03-01

    The water solubility of salts is ordinarily dictated by lattice energy and ion solvation. However, in the case of low melting salts also known as ionic liquids, lattice energy is immaterial and differences in hydrophobicity largely account for differences in their water solubility. In this contribution, the activity coefficients of ionic liquids in water are split into cation and anion contributions by regression against cation hydrophobicity parameters that are experimentally determined by reversed phase liquid chromatography. In this way, anion hydrophobicity parameters are derived, as well as an equation to estimate water solubilities for cation-anion combinations for which the water solubility has not been measured. Thus, a new pathway to the quantification of aqueous ion solvation is shown, making use of the relative weakness of interactions between ionic liquid ions as compared to their hydrophobicities.

  3. Explaining Ionic Liquid Water Solubility in Terms of Cation and Anion Hydrophobicity

    Directory of Open Access Journals (Sweden)

    Johannes Ranke

    2009-03-01

    Full Text Available The water solubility of salts is ordinarily dictated by lattice energy and ion solvation. However, in the case of low melting salts also known as ionic liquids, lattice energy is immaterial and differences in hydrophobicity largely account for differences in their water solubility. In this contribution, the activity coefficients of ionic liquids in water are split into cation and anion contributions by regression against cation hydrophobicity parameters that are experimentally determined by reversed phase liquid chromatography. In this way, anion hydrophobicity parameters are derived, as well as an equation to estimate water solubilities for cation-anion combinations for which the water solubility has not been measured. Thus, a new pathway to the quantification of aqueous ion solvation is shown, making use of the relative weakness of interactions between ionic liquid ions as compared to their hydrophobicities.

  4. Gold Ion-Angiotensin Peptide Interaction by Mass Spectrometry

    Science.gov (United States)

    Lee, Jenny; Jayathilaka, Lasanthi P.; Gupta, Shalini; Huang, Jin-Sheng; Lee, Bao-Shiang

    2012-05-01

    Stimulated by the interest in developing gold compounds for treating cancer, gold ion-angiotensin peptide interactions are investigated by mass spectrometry. Under the experimental conditions used, the majority of gold ion-angiotensin peptide complexes contain gold in the oxidation states I and III. Both ESI-MS and MALDI-TOF MS detect singly/multiply charged ions for mononuclear/multinuclear gold-attached peptides, which are represented as [peptide + a Au(I) + b Au(III) + (e - a -3b) H]e+, where a,b ≥ 0 and e is charge. ESI-MS data shows singly/multiply charged ions of Au(I)-peptide and Au(III)-peptide complexes. This study reveals that MALDI-TOF MS mainly detects singly charged Au(I)-peptide complexes, presumably due to the ionization process. The electrons in the MALDI plume seem to efficiently reduce Au(III) to Au(I). MALDI also tends to enhance the higher polymeric forms of gold-peptide complexes regardless of the laser power used. Collision-induced dissociation experiments of the mononuclear and dinuclear gold-attached peptide ions for angiotensin peptides show that the gold ion (a soft acid) binding sites are in the vicinity of Cys (a soft ligand), His (a major anchor of peptide for metal ion chelation), and the basic residue Arg. Data also suggests that the abundance of gold-attached peptides increases with higher gold concentration until saturation, after which an increase in gold ion concentration leads to the aggregation and/or precipitation of gold-bound peptides.

  5. Are the interactions between recombinant prion proteins and polymeric surfaces related to the hydrophilic/hydrophobic balance?

    Science.gov (United States)

    Vrlinic, Tjasa; Debarnot, Dominique; Legeay, Gilbert; Coudreuse, Arnaud; El Moualij, Benaissa; Zorzi, Willy; Perret-Liaudet, Armand; Quadrio, Isabelle; Mozetic, Miran; Poncin-Epaillard, Fabienne

    2012-06-01

    New non-fouling tubes are developed and their influence on the adhesion of neuroproteins is studied. Recombinant prion proteins are considered as a single component representative of hydrophobic proteins. Samples are stored for 24 h at 4 °C in tubes coated with two different coatings: poly(N-isopropylacrylamide) as a hydrophilic surface and a plasma-fluorinated coating as a hydrophobic one. The protein adhesion is monitored by ELISA tests, XPS and confocal microscopy. It appears that the highest recovery of recombinant prion protein in the liquid phase is obtained with the hydrophilic surface while the hydrophobic character of the storage tube induces an important amount of biological loss. However, the recovery is not complete even for tubes coated with poly(N-isopropylacrylamide). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Investigation of Cellular Interactions of Nanoparticles by Helium Ion Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Arey, Bruce W.; Shutthanandan, V.; Xie, Yumei; Tolic, Ana; Williams, Nolann G.; Orr, Galya

    2011-06-01

    The helium ion mircroscope (HIM) probes light elements (e.g. C, N, O, P) with high contrast due to the large variation in secondary electron yield, which minimizes the necessity of specimen staining. A defining characteristic of HIM is its remarkable capability to neutralize charge by the implementation of an electron flood gun, which eliminates the need for coating non-conductive specimens for imaging at high resolution. In addition, the small convergence angle in HeIM offers a large depth of field (~5x FE-SEM), enabling tall structures to be viewed in focus within a single image. Taking advantage of these capabilities, we investigate the interactions of engineered nanoparticles (NPs) at the surface of alveolar type II epithelial cells grown at the air-liquid interface (ALI). The increasing use of nanomaterials in a wide range of commercial applications has the potential to increase human exposure to these materials, but the impact of such exposure on human health is still unclear. One of the main routs of exposure is the respiratory tract, where alveolar epithelial cells present a vulnerable target at the interface with ambient air. Since the cellular interactions of NPs govern the cellular response and ultimately determine the impact on human health, our studies will help delineating relationships between particle properties and cellular interactions and response to better evaluate NP toxicity or biocompatibility. The Rutherford backscattered ion (RBI) is a helium ions imaging mode, which backscatters helium ions from every element except hydrogen, with a backscatter yield that depends on the atomic number of the target. Energy-sensitive backscatter analysis is being developed, which when combined with RBI image information, supports elemental identification at helium ion nanometer resolution. This capability will enable distinguishing NPs from cell surface structures with nanometer resolution.

  7. Interaction of alkali and alkaline earth ions with Ochratoxin A

    Energy Technology Data Exchange (ETDEWEB)

    Poor, Miklos [Institute of Laboratory Medicine, University of Pecs, Pecs H-7624 (Hungary); Kunsagi-Mate, Sandor; Matisz, Gergely; Li, Yin; Czibulya, Zsuzsanna [Department of General and Physical Chemistry, University of Pecs, Pecs H-7624 (Hungary); Janos Szentagothai Research Center, Pecs H-7624 (Hungary); Peles-Lemli, Beata [Department of General and Physical Chemistry, University of Pecs, Pecs H-7624 (Hungary); Koszegi, Tamas, E-mail: koszegit@freemail.hu [Institute of Laboratory Medicine, University of Pecs, Pecs H-7624 (Hungary)

    2013-03-15

    The effect of alkali and alkaline earth ions on the chemical equilibrium of mono- and dianionic forms of the mycotoxin Ochratoxin A (OTA) and their bonding onto the surface of Bovine Serum Albumin (BSA) have been investigated by fluorescence spectroscopy and fluorescence polarization techniques. Our results show that alkali metal ions shift the chemical equilibrium towards formation of dianionic form of OTA. Furthermore, the alkaline earth ions can compete with BSA for binding to OTA when these ions are present in millimolar concentrations. Our data also highlight the possibility that the 'free' fraction of OTA (not bound onto the surface of albumin) or at least a part of it is present in cation-bound form in body fluids. These observations are supported by stability constants and quantum-chemical calculations. Among the studied alkaline metal ions magnesium showed the highest affinity towards OTA under physiological conditions. Further research is required to analyze the potential significance of Mg{sup 2+}-OTA complex in cellular uptake and/or elimination of the toxin in the human body. - Highlights: Black-Right-Pointing-Pointer Fluorescence spectroscopy reveals cation-Ochratoxin A (OTA) interactions. Black-Right-Pointing-Pointer Alkali ions shift the equilibrium of OTA to formation of a dianionic structure. Black-Right-Pointing-Pointer Alkaline earth ions directly bind to OTA in the order: Mg{sup 2+}, Ca{sup 2+}, Ba{sup 2+}. Black-Right-Pointing-Pointer Quantum chemical calculations and logK values support our experimental data.

  8. ENERGETIC PHOTON AND ELECTRON INTERACTIONS WITH POSITIVE IONS

    Energy Technology Data Exchange (ETDEWEB)

    Phaneuf, Ronald A. [UNR

    2013-07-01

    The objective of this research is a deeper understanding of the complex multi-electron interactions that govern inelastic processes involving positive ions in plasma environments, such as those occurring in stellar cares and atmospheres, x-ray lasers, thermonuclear fusion reactors and materials-processing discharges. In addition to precision data on ionic structure and transition probabilities, high resolution quantitative measurements of ionization test the theoretical methods that provide critical input to computer codes used for plasma modeling and photon opacity calculations. Steadily increasing computational power and a corresponding emphasis on simulations gives heightened relevance to precise and accurate benchmark data. Photons provide a highly selective probe of the internal electronic structure of atomic and molecular systems, and a powerful means to better understand more complex electron-ion interactions.

  9. Hydrophilic and hydrophobic adsorption on Y zeolites

    Science.gov (United States)

    Halasz, Istvan; Kim, Song; Marcus, Bonnie

    The uniform large micropores of hydrothermally stable Y zeolites are used widely to confine both polar and non-polar molecules. This paper compares the physisorption of water, methanol, cyclohexane, benzene and other adsorbates over various Y zeolites. These adsorbents are commercial products with reproducibly controllable physical and chemical characteristics. Results indicate that the type I isotherms typical for micropore adsorption can turn into type II or type III isotherms depending on either or both the hydrophobicity of the adsorbent and the polarity of the adsorbate. Methanol produced a rare type V isotherm not reported over zeolites before. Canonical and grand canonical Monte Carlo molecular simulations with Metropolis importance sampling reproduced the experimental isotherms and showed characteristic geometric patterns for molecules confined in Na-X, Na-Y, dealuminated Y, and ZSM5 structures. Adsorbate-adsorbate interactions seem to determine the micropore condensation of both polar and non-polar molecules. Exchanged ions and lattice defects play a secondary role in shaping the adsorption isotherms. The force field of hydrophobic Y appears to exert an as yet unexplored sieving effect on adsorbates having different dipole moments and partial charge distributions. This mechanism is apparently different from both the monolayer formation controlled adsorption on hydrophobic mesopores and macropores and the polarizability and small-pore opening controlled micropore confinement in hydrophobic ZSM5.

  10. Functional bacterial amyloid increases Pseudomonas biofilm hydrophobicity and stiffness

    DEFF Research Database (Denmark)

    Zeng, Guanghong; Vad, Brian S; Dueholm, Morten S

    2015-01-01

    hydrophobicity and mechanical properties. Using atomic force microscopy imaging and force spectroscopy, we show that the amyloid renders individual cells more resistant to drying and alters their interactions with hydrophobic probes. Importantly, amyloid makes Pseudomonas more hydrophobic and increases biofilm...

  11. Ion Acceleration by Laser Plasma Interaction from Cryogenic Microjets

    Energy Technology Data Exchange (ETDEWEB)

    Propp, Adrienne [Harvard Univ., Cambridge, MA (United States)

    2015-08-16

    Processes that occur in extreme conditions, such as in the center of stars and large planets, can be simulated in the laboratory using facilities such as SLAC National Accelerator Laboratory and the Jupiter Laser Facility (JLF) at Lawrence Livermore National Laboratory (LLNL). These facilities allow scientists to investigate the properties of matter by observing their interactions with high-power lasers. Ion acceleration from laser plasma interaction is gaining greater attention today due to its widespread potential applications, including proton beam cancer therapy and fast ignition for energy production. Typically, ion acceleration is achieved by focusing a high power laser on thin foil targets through a mechanism called Target Normal Sheath Acceleration. However, this mechanism is not ideal for creating the high-energy proton beams needed for future applications. Based on research and recent experiments, we hypothesized that a pure liquid cryogenic jet would be an ideal target for exploring new regimes of ion acceleration. Furthermore, it would provide a continuous, pure target, unlike metal foils which are consumed in the interaction and easily contaminated. In an effort to test this hypothesis, we used the 527 nm split beam, frequency-doubled TITAN laser at JLF. Data from the cryogenic jets was limited due to the flow of current up the jet into the nozzle during the interaction, heating the jet and damaging the orifice. However, we achieved a pure proton beam with evidence of a monoenergetic feature. Furthermore, data from gold and carbon wires showed surprising and interesting results. Preliminary analysis of data from two ion emission diagnostics, Thomson parabola spectrometers (TPs) and radio chromic films (RCFs), suggests that shockwave acceleration occurred rather than target normal sheath acceleration, the standard mechanism of ion acceleration. Upon completion of the experiment at TITAN, I researched the possibility of transforming our liquid cryogenic

  12. Polyelectrolyte conformational transition in aqueous solvent mixture influenced by hydrophobic interactions and hydrogen bonding effects: PAA-water-ethanol.

    Science.gov (United States)

    Sappidi, Praveenkumar; Natarajan, Upendra

    2016-03-01

    Molecular dynamics simulations of poly(acrylic acid) PAA chain in water-ethanol mixture were performed for un-ionized and ionized cases at different degree-of-ionization 0%, 80% and 100% of PAA chain by Na(+) counter-ions and co-solvent (ethanol) concentration in the range 0-90vol% ethanol. Aspects of structure and dynamics were investigated via atom pair correlation functions, number and relaxation of hydrogen bonds, nearest-neighbor coordination numbers, and dihedral angle distribution function for back-bone and side-groups of the chain. With increase in ethanol concentration, chain swelling is observed for un-ionized chain (f=0) and on the contrary chain shrinkage is observed for partially and fully ionized cases (i.e., f=0.8 and 1). For un-ionized PAA, with increase in ethanol fraction ϕeth the number of PAA-ethanol hydrogen bonds increases while PAA-water decreases. Increase in ϕeth leads to PAA chain expansion for un-ionized case and chain shrinkage for ionized case, in agreement with experimental observations on this system. For ionized-PAA case, chain shrinkage is found to be influenced by intermolecular hydrogen bonding with water as well as ethanol. The localization of ethanol molecules near the un-ionized PAA backbone at higher levels of ethanol is facilitated by a displacement of water molecules indicating presence of specific ethanol hydration shell, as confirmed by results of the RDF curves and coordination number calculations. This behavior, controlled by hydrogen bonding provides a significant contribution to such a conformational transition behavior of the polyelectrolyte chain. The interactions between counter-ions and charges on the PAA chain also influence chain collapse. The underlying origins of polyelectrolyte chain collapse in water-alcohol mixtures are brought out for the first time via explicit MD simulations by this study. Copyright © 2016 Elsevier Inc. All rights reserved.

  13. Taking into Account the Ion-induced Dipole Interaction in the Nonbonded Model of Ions.

    Science.gov (United States)

    Li, Pengfei; Merz, Kenneth M

    2014-01-14

    Metal ions exist in almost half of the proteins in the protein databank and they serve as structural, electron-transfer and catalytic elements in the metabolic processes of organisms. Molecular Dynamics (MD) simulation is a powerful tool that provides information about biomolecular systems at the atomic level. Coupled with the growth in computing power, algorithms like the Particle Mesh Ewald (PME) method have become the accepted standard when dealing with long-range interactions in MD simulations. The nonbonded model of metal ions consists of an electrostatic plus 12-6 Lennard Jones (LJ) potential and is used largely because of its speed relative to more accurate models. In previous work we found that ideal parameters do not exist that reproduce several experimental properties for M(II) ions simultaneously using the nonbonded model coupled with the PME method due to the underestimation of metal ion-ligand interactions. Via a consideration of the nature of the nonbonded model, we proposed that the observed error largely arises from overlooking charge-induced dipole interactions. The electrostatic plus 12-6 LJ potential model works reasonably well for neutral systems but does struggle with more highly charged systems. In the present work we designed and parameterized a new nonbonded model for metal ions by adding a 1/r4 term to the 12-6 model. We call it the 12-6-4 LJ-type nonbonded model due to its mathematical construction. Parameters were determined for 16 +2 metal ions for the TIP3P, SPC/E and TIP4PEW water models. The final parameters reproduce the experimental hydration free energies (HFE), ion-oxygen distances (IOD) in the first solvation shell and coordination numbers (CN) accurately for the metal ions investigated. Preliminary tests on MgCl2 at different concentrations in aqueous solution and Mg2+--nucleic acid systems show reasonable results suggesting that the present parameters can work in mixed systems. The 12-6-4 LJ-type nonbonded model is readily

  14. Chandrayaan-1 results on the solar wind ion - regolith interaction

    Science.gov (United States)

    Barabash, Stas

    Recently several missions (Kaguya, Chandrayaan-1, IBEX) revealed for the first time the complexity of the solar wind ions interaction with the lunar regolith. In this review we focus on the observations performed by the Chandrayaan-1 mission at the Moon but similar interaction processes take place on all airless bodies covered by regolith. Contrary to early assumptions the solar wind ions are not fully absorbed by the regolith but experience strong (10-20% of the impinging flux) backscattering. Only hydrogen was firmly identified. Helium for the helium enriched solar wind was detected only tentatively. The charge - state of the backscattered particles is mainly neutral. The fraction of H (+) varies strongly with the impinging solar wind velocity and constitutes 0.01 - 10% of the total backscattered flux. No H (-) ions were detected. The spectrum of the backscattered hydrogen is best-fitted by a Maxwellian distribution with a temperature of 40 - 160 eV linearly proportional to the solar wind velocity. The spectrum of the backscattered protons is also Maxwellian although shifted to a velocity some what smaller than the solar wind velocity. The scattering function of the neutrals is close to isotropic at large impinging angles (small solar zenith angles) and becomes backward peaked at shallow impinging angles. The scattering function and energy spectra of the backscatters indicate that the solar wind protons experience multiple collisions with surfaces of individual grain when traveling in the inter-grain space. Why the reflection efficiency is so high in this case is a puzzle. The solar wind also causes sputtering of elements composing the regolith minerals. Only sputtered oxygen was identified although at levels lower than expected. Chandrayaan-1 results on the solar wind ion - regolith interaction still remain to be explained. The orbital measurements should be complemented by measurements from landers revealing the “ground true”. Further studies of the

  15. 1. part: strong interactions 1: heavy ions; 1. partie: interactions fortes 1: ions lourds

    Energy Technology Data Exchange (ETDEWEB)

    Suire, Ch

    2007-07-01

    This article is an introduction to the study of the quark-gluon plasma obtained through heavy ion collisions at ultra-relativistic range. In such collisions the energy density can exceed about 1 GeV/fm{sup 3} which implies that matter no longer exists as separate hadrons but rather as their fundamental constituents: quarks and gluons. The experimental difficulty lies in the fact that both the lifetime and size of the system are very limited. The signatures of the quark gluon plasma are of 3 types according to the parameters on which they are based: -) the change in the equation of state of the matter, -) the chiral symmetry, and -) the properties of the medium.

  16. Real-time monitoring of hydrophobic aggregation reveals a critical role of cooperativity in hydrophobic effect

    Science.gov (United States)

    Jiang, Liguo; Cao, Siqin; Cheung, Peter Pak-Hang; Zheng, Xiaoyan; Leung, Chris Wai Tung; Peng, Qian; Shuai, Zhigang; Tang, Ben Zhong; Yao, Shuhuai; Huang, Xuhui

    2017-05-01

    The hydrophobic interaction drives nonpolar solutes to aggregate in aqueous solution, and hence plays a critical role in many fundamental processes in nature. An important property intrinsic to hydrophobic interaction is its cooperative nature, which is originated from the collective motions of water hydrogen bond networks surrounding hydrophobic solutes. This property is widely believed to enhance the formation of hydrophobic core in proteins. However, cooperativity in hydrophobic interactions has not been successfully characterized by experiments. Here, we quantify cooperativity in hydrophobic interactions by real-time monitoring the aggregation of hydrophobic solute (hexaphenylsilole, HPS) in a microfluidic mixer. We show that association of a HPS molecule to its aggregate in water occurs at sub-microsecond, and the free energy change is -5.8 to -13.6 kcal mol-1. Most strikingly, we discover that cooperativity constitutes up to 40% of this free energy. Our results provide quantitative evidence for the critical role of cooperativity in hydrophobic interactions.

  17. Pressure versus heat-induced unfolding of ribonuclease A: the case of hydrophobic interactions within a chain-folding initiation site.

    Science.gov (United States)

    Torrent, J; Connelly, J P; Coll, M G; Ribó, M; Lange, R; Vilanova, M

    1999-11-30

    To investigate the characteristics of the postulated carboxy terminal chain-folding initiation site in bovine pancreatic ribonuclease A (RNase A) (residues 106-118), important in the early stages of the folding pathway, we have engineered by site-directed mutagenesis a set of 14 predominantly conservative hydrophobic variants of the protein. The stability of each variant has been compared by pressure and temperature-induced unfolding, monitored by fourth derivative UV absorbance spectroscopy. Apparently simple two-state, reversible unfolding transitions are observed, suggesting that the disruption of tertiary structure of each protein at high pressure or temperature is strongly cooperative. Within the limits of the technique, we are unable to detect significant differences between the two processes of denaturation. Both steady-state kinetic parameters for the enzyme reaction and UV CD spectra of each RNase A variant indicate that truncation of hydrophobic side chains in this region has, in general, little or no effect on the native structure and function of the enzyme. Furthermore, the decreases in free energy of unfolding upon pressure and thermal denaturation of all the variants, particularly those modified at residues 106 and 108, suggest that the hydrophobic residues and side chain packing interactions of this region play an important role in maintaining the conformational stability of RNase A. We also demonstrate the potential of Tyr115 replacement by Trp as a non-destabilizing fluorescence probe of conformational changes local to the region.

  18. Hydrophobic interaction between contiguous residues in the S6 transmembrane segment acts as a stimuli integration node in the BK channel

    Science.gov (United States)

    Carrasquel-Ursulaez, Willy; Contreras, Gustavo F.; Sepúlveda, Romina V.; Aguayo, Daniel; González-Nilo, Fernando

    2015-01-01

    Large-conductance Ca2+- and voltage-activated K+ channel (BK) open probability is enhanced by depolarization, increasing Ca2+ concentration, or both. These stimuli activate modular voltage and Ca2+ sensors that are allosterically coupled to channel gating. Here, we report a point mutation of a phenylalanine (F380A) in the S6 transmembrane helix that, in the absence of internal Ca2+, profoundly hinders channel opening while showing only minor effects on the voltage sensor active–resting equilibrium. Interpretation of these results using an allosteric model suggests that the F380A mutation greatly increases the free energy difference between open and closed states and uncouples Ca2+ binding from voltage sensor activation and voltage sensor activation from channel opening. However, the presence of a bulky and more hydrophobic amino acid in the F380 position (F380W) increases the intrinsic open–closed equilibrium, weakening the coupling between both sensors with the pore domain. Based on these functional experiments and molecular dynamics simulations, we propose that F380 interacts with another S6 hydrophobic residue (L377) in contiguous subunits. This pair forms a hydrophobic ring important in determining the open–closed equilibrium and, like an integration node, participates in the communication between sensors and between the sensors and pore. Moreover, because of its effects on open probabilities, the F380A mutant can be used for detailed voltage sensor experiments in the presence of permeant cations. PMID:25548136

  19. Hydrophobic repulsion and its origin

    OpenAIRE

    Schlesinger, Itai; Sivan, Uri

    2016-01-01

    The fundamental role of hydrophobic interactions in nature and technology has motivated decades long research aimed at measuring the distance-dependent hydrophobic force and identifying its origin. This quest has nevertheless proved more elusive than anticipated and the nature of the interaction at distances shorter than 2-3 nanometers, or even its sign, have never been conclusively determined. Employing an ultra-high resolution frequency-modulation atomic force microscope (FM-AFM) we succeed...

  20. Calcium ion-protein interactions in prothrombin activation

    Energy Technology Data Exchange (ETDEWEB)

    Brenckle, G.M.; Carlisle, T.L.; Jackson, C.M.

    1981-01-01

    1. The protein concentration dependence observed in the calcium binding to fragment 1 indicates that calcium-mediated dimerization is responsible for the cooperative calcium binding behavior usually observed. ''Unusual'' fragment 1, which exhibits negative cooperativity (the type of binding behavior expected for ions interacting with a charged protein) at high concentration, also exhibit altered self-association behavior. 2. The calcium-induced spectral perturbations that are observed by fluorescence and ultraviolet difference spectroscopy are influenced by calcium-mediated dimerization. Similar spectral perturbations may also be induced by other divalent, trivalent, and monovalent ions, as well as changes in pH. Because this is a multi-site system, only limited interpretation of the spectral data is possible without calcium binding data. 3. Although strong side chain CD signals make estimation of fragment 1 secondary structure ambiguous, the CD data do indicate small changes in structure during calcium binding. Similar changes are observed upon addition of monovalent ions at high concentration or after lowering the pH. No coupling between changes in conformation and the cooperative calcium binding behavior has yet been observed to exist.

  1. Exploring Non-obvious Hydrophobic Binding Pockets on Protein Surfaces: Increasing Affinities in Peptide-Protein Interactions.

    Science.gov (United States)

    Balliu, Aleksandra; Baltzer, Lars

    2017-07-18

    A 42-residue polypeptide conjugated to a small-molecule organic ligand capable of targeting the phosphorylated side chain of Ser15 was shown to bind glycogen phosphorylase a (GPa) with a KD value of 280 nm. The replacement of hydrophobic amino acids by Ala reduced affinities, whereas the incorporation of l-2-aminooctanoic acid (Aoc) increased them. Replacing Nle5, Ile9 and Leu12 by Aoc reduced the KD value from 280 to 27 nm. "Downsizing" the 42-mer to an undecamer gave rise to an affinity for GPa an order of magnitude lower, but the undecamer in which Nle5, Ile9 and Leu12 were replaced by Aoc showed a KD value of 550 nm, comparable with that of the parent 42-mer. The use of Aoc residues offers a convenient route to increased affinity in protein recognition as well as a strategy for the "downsizing" of peptides essentially without loss of affinity. The results show that hydrophobic binding sites can be found on protein surfaces by comparing the affinities of polypeptide conjugates in which Aoc residues replace Nle, Ile, Leu or Phe with those of their unmodified counterparts. Polypeptide conjugates thus provide valuable opportunities for the optimization of peptides and small organic compounds in biotechnology and biomedicine. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Efficiency of blocking of non-specific interaction of different proteins by BSA adsorbed on hydrophobic and hydrophilic surfaces.

    Science.gov (United States)

    Jeyachandran, Y L; Mielczarski, J A; Mielczarski, E; Rai, B

    2010-01-01

    The efficiency of a pre-absorbed bovine serum albumin (BSA) layer in blocking the non-specific adsorption of different proteins on hydrophobic and hydrophilic surfaces was evaluated qualitatively and quantitatively using infrared reflection spectroscopy supported by spectral simulations. A BSA layer with a surface coverage of 35% of a close-packed monolayer exhibited a blocking efficiency of 90-100% on a hydrophobic and 68-100% on a hydrophilic surface, with respect to the non-specific adsorption of concanavalin A (Con A), immunoglobulin G (IgG), and staphylococcal protein A (SpA). This BSA layer was produced using a solution concentration of 1 mg/mL and 30 min incubation time. BSA layers that were adsorbed at conditions commonly employed for blocking (a 12 h incubation time and a solution concentration of 10 mg/mL) exhibited a blocking activity that involved competitive adsorption-desorption. This activity resulted from the formation of BSA-phosphate surface complexes, which correlated with the conformation of adsorbed BSA molecules that was favourable for blocking. The importance of optimisation of the adsorbed BSA layer for different surfaces and proteins to achieve efficient blocking was addressed in this study.

  3. Surface Deposition and Phase Behavior of Oppositely Charged Polyion–Surfactant Ion Complexes. Delivery of Silicone Oil Emulsions to Hydrophobic and Hydrophilic Surfaces

    Science.gov (United States)

    2011-01-01

    The adsorption from mixed polyelectrolyte–surfactant solutions at hydrophobized silica surfaces was investigated by in situ null-ellipsometry, and compared to similar measurements for hydrophilic silica surfaces. Three synthetic cationic copolymers of varying hydrophobicity and one cationic hydroxyethyl cellulose were compared in mixtures with the anionic surfactant sodium dodecylsulfate (SDS) in the absence or presence of a dilute silicone oil emulsion. The adsorption behavior was mapped while stepwise increasing the concentration of SDS to a polyelectrolyte solution of constant concentration. The effect on the deposition of dilution of the bulk solution in contact with the surface was also investigated by gradual replacement of the bulk solution with 1 mM aqueous NaCl. An adsorbed layer remained after complete exchange of the polyelectrolyte/surfactant solution for aqueous NaCl. In most cases, there was a codeposition of silicone oil droplets, if such droplets were present in the formulation before dilution. The overall features of the deposition were similar at hydrophobic and hydrophilic surfaces, but there were also notable differences. SDS molecules adsorbed selectively at the hydrophobized silica surface, but not at the hydrophilic silica, which influenced the coadsorption of the cationic polymers. The largest amount of deposited material after dilution was found for hydrophilic silica and for the least-hydrophobic cationic polymers. For the least-hydrophobic polyions, no significant codeposition of silicone oil was detected at hydrophobized silica after dilution if the initial SDS concentration was high. PMID:21667982

  4. Synthetic ion transporters that work with anion-π interactions, halogen bonds, and anion-macrodipole interactions.

    Science.gov (United States)

    Vargas Jentzsch, Andreas; Hennig, Andreas; Mareda, Jiri; Matile, Stefan

    2013-12-17

    The transport of ions and molecules across lipid bilayer membranes connects cells and cellular compartments with their environment. This biological process is central to a host of functions including signal transduction in neurons and the olfactory and gustatory sensing systems, the translocation of biosynthetic intermediates and products, and the uptake of nutrients, drugs, and probes. Biological transport systems are highly regulated and selectively respond to a broad range of physical and chemical stimulation. A large percentage of today's drugs and many antimicrobial or antifungal agents take advantage of these systems. Other biological transport systems are highly toxic, such as the anthrax toxin or melittin from bee venom. For more than three decades, organic and supramolecular chemists have been interested in developing new transport systems. Over time, curiosity about the basic design has evolved toward developing of responsive systems with applications in materials sciences and medicine. Our early contributions to this field focused on the introduction of new structural motifs with emphasis on rigid-rod scaffolds, artificial β-barrels, or π-stacks. Using these scaffolds, we have constructed selective systems that respond to voltage, pH, ligands, inhibitors, or light (multifunctional photosystems). We have described sensing applications that cover the three primary principles of sensor development: immunosensors that use aptamers, biosensors (an "artificial" tongue), and differential sensors (an "artificial" nose). In this Account, we focus on our recent interest in applying synthetic transport systems as analytical tools to identify the functional relevance of less common noncovalent interactions, anion-π interactions, halogen bonds, and anion-macrodipole interactions. Anion-π interactions, the poorly explored counterpart of cation-π interactions, occur in aromatic systems with a positive quadrupole moment, such as TNT or hexafluorobenzene. To observe

  5. Interaction between ions in hot dense plasma via screened Cornell potential

    Energy Technology Data Exchange (ETDEWEB)

    Ramazanov, T. S.; Moldabekov, Zh. A.; Gabdullin, M. T. [Institute for Experimental and Theoretical Physics, Al-Farabi Kazakh National University, 71 Al-Farabi Str., 050040 Almaty (Kazakhstan)

    2016-04-15

    Hot dense plasma with non-ideal ions and weakly coupled electrons is studied analytically in the framework of the random phase approximation. It is shown that at some plasma parameters ions interact by a screened Cornell potential. The reduction in the transport coefficients due to the localization of the electron around the ion is predicted. This prediction is confirmed by the molecular dynamics simulation of the one-component ion plasma interacting via the obtained screened Cornell type potential.

  6. Combined effects of potassium chloride and ethanol as mobile phase modulators on hydrophobic interaction and reversed-phase chromatography of three insulin variants.

    Science.gov (United States)

    Johansson, Karolina; Frederiksen, Søren S; Degerman, Marcus; Breil, Martin P; Mollerup, Jørgen M; Nilsson, Bernt

    2015-02-13

    The two main chromatographic modes based on hydrophobicity, hydrophobic interaction chromatography (HIC) and reversed-phase chromatography (RPC), are widely used for both analytical and preparative chromatography of proteins in the pharmaceutical industry. Despite the extensive application of these separation methods, and the vast amount of studies performed on HIC and RPC over the decades, the underlying phenomena remain elusive. As part of a systematic study of the influence of mobile phase modulators in hydrophobicity-based chromatography, we have investigated the effects of both KCl and ethanol on the retention of three insulin variants on two HIC adsorbents and two RPC adsorbents. The focus was on the linear adsorption range, separating the modulator effects from the capacity effects, but some complementary experiments at higher load were included to further investigate observed phenomena. The results show that the modulators have the same effect on the two RPC adsorbents in the linear range, indicating that the modulator concentration only affects the activity of the solute in the mobile phase, and not that of the solute-ligand complex, or that of the ligand. Unfortunately, the HIC adsorbents did not show the same behavior. However, the insulin variants displayed a strong tendency toward self-association on both HIC adsorbents; on one in particular. Since this causes peak fronting, the retention is affected, and this could probably explain the lack of congruity. This conclusion was supported by the results from the non-linear range experiments which were indicative of double-layer adsorption on the HIC adsorbents, while the RPC adsorbents gave the anticipated increased tailing at higher load. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Thermochemistry of non-covalent ion-molecule interactions.

    Science.gov (United States)

    Armentrout, P B; Rodgers, M T

    2013-01-01

    The thermochemistry of non-covalent ion-molecule complexes has been examined by measuring quantitative bond dissociation energies using threshold collision-induced dissociation in guided ion beam tandem mass spectrometers (GIBMS). The methods used are briefly reviewed and several examples of the types of information and insight that can be obtained from such thermodynamic information are discussed. The hydration of metal cations, both singly and doubly charged, is reviewed and the trends elucidated, mainly on the basis of electrostatic contributions. The binding of alkali metal cations to amino acids has been examined for a range of systems, with both the overall polarizability of the amino acid and the local dipole moment of heteroatomic side-chains shown to be important contributors. The gas-phase interactions of the 12-crown-4 (12C4) polyether with alkali metal cations, classic molecular recognition systems in solution, have been newly compared to previous GIBMS work. These results validate the previous hypothesis that excited conformers were present for Rb(+)(12C4) and Cs(+)(12C4) and offer clues as to how and why they are formed.

  8. Single column comprehensive analysis of pharmaceutical preparations using dual-injection mixed-mode (ion-exchange and reversed-phase) and hydrophilic interaction liquid chromatography.

    Science.gov (United States)

    Kazarian, Artaches A; Taylor, Mark R; Haddad, Paul R; Nesterenko, Pavel N; Paull, Brett

    2013-12-01

    The comprehensive separation and detection of hydrophobic and hydrophilic active pharmaceutical ingredients (APIs), their counter-ions (organic, inorganic) and excipients, using a single mixed-mode chromatographic column, and a dual injection approach is presented. Using a mixed-mode Thermo Fisher Acclaim Trinity P1 column, APIs, their counter-ions and possible degradants were first separated using a combination of anion-exchange, cation-exchange and hydrophobic interactions, using a mobile phase consisting of a dual organic modifier/salt concentration gradient. A complementary method was also developed using the same column for the separation of hydrophilic bulk excipients, using hydrophilic interaction liquid chromatography (HILIC) under high organic solvent mobile phase conditions. These two methods were then combined within a single gradient run using dual sample injection, with the first injection at the start of the applied gradient (mixed-mode retention of solutes), followed by a second sample injection at the end of the gradient (HILIC retention of solutes). Detection using both ultraviolet absorbance and refractive index enabled the sensitive detection of APIs and UV-absorbing counter-ions, together with quantitative determination of bulk excipients. The developed approach was applied successfully to the analysis of a dry powder inhalers (Flixotide(®), Spiriva(®)), enabling comprehensive quantification of all APIs and excipients in the sample. Copyright © 2013 Elsevier B.V. All rights reserved.

  9. Role of hydrogen bonding in ligand interaction with the N-methyl-D-aspartate receptor ion channel

    Energy Technology Data Exchange (ETDEWEB)

    Leeson, P.D.; Carling, R.W.; James, K.; Smith, J.D.; Moore, K.W.; Wong, E.H.; Baker, R. (Merck Sharp Laboratory, Harlow, Essex (England))

    1990-05-01

    Displacement of (3H)MK-801 (dizocilpine, 1) binding to rat brain membranes has been used to evaluate the affinities of novel dibenzocycloalkenimines related to 1 for the ion channel binding site (also known as the phencyclidine or PCP receptor) on the N-methyl-D-aspartate (NMDA) subtype of excitory amino acid receptor. In common with many other agents having actions in the central nervous system, these compounds contain a hydrophobic aromatic moiety and a basic nitrogen atom. The conformational rigidity of these ligands provides a unique opportunity to evaluate the importance of specific geometrical properties that influence active-site recognition, in particular the role of the nitrogen atom in hydrogen-bonding interactions. The relative affinities (IC50s) of hydrocarbon-substituted analogues of 1 and ring homologated cyclooctenimines illustrate the importance of size-limited hydrophobic binding of both aryl rings and of the quaternary C-5 methyl group. Analysis of the binding of a series of the 10 available structurally rigid dibenzoazabicyclo(x.y.z)alkanes, by using molecular modeling techniques, uncovered a highly significant correlation between affinity and a proposed ligand-active site hydrogen bonding vector (r = 0.950, p less than 0.001). These results are used to generate a pharmacophore of the MK-801 recognition site/PCP receptor, which accounts for the binding of all of the known ligands.

  10. Hydrophobic photolabeling identifies BHA2 as the subunit mediating the interaction of bromelain-solubilized influenza virus hemagglutinin with liposomes at low pH

    Energy Technology Data Exchange (ETDEWEB)

    Harter, C.; Baechi, T.S.; Semenza, G.; Brunner, J.

    1988-03-22

    To investigate the molecular basis of the low-pH-mediated interaction of the bromelain-solubilized ectodomain of influenza virus hemagglutinin (BHA) with membranes, we have photolabeled BHA in the presence of liposomes with the two carbene-generating, membrane-directed reagents 3-(trifluoromethyl)-3-(m-(/sup 125/I)iodophenyl)diazirine ((/sup 125/I)TID) and a new analogue of a phospholipid, 1-palmitoyl-2-(11-(4-(3-(trifluoromethyl)diazirinyl)phenyl)(2-/sup 3/H) undecanoyl)-sn-glycero-3-phosphocholine ((/sup 3/H)-PTPC/11). With the latter reagent, BHA was labeled in a strictly pH-dependent manner, i.e., at pH 5 only, whereas with (/sup 125/I)TID, labeling was seen also at pH 7. In all experiments, the label was selectively incorporated into the BHA2 polypeptide, demonstrating that the interaction of BHA with membranes is mediated through this subunit, possibly via its hydrophobic N-terminal segment. Similar experiments with a number of other water-soluble proteins (ovalbumin, carbonic anhydrase, alpha-lactalbumin, trypsin, and soybean trypsin inhibitor) indicate that the ability to interact with liposomes at low pH is not a property specific for BHA but is observed with other, perhaps most, proteins.

  11. Speciation of heavy metal ions as influenced by interactions with montmorillonite, Al hydroxide polymers and citrate

    NARCIS (Netherlands)

    Janssen, R.P.T.

    1995-01-01

    Clay minerals, metal-hydroxides and organic matter can bind metal ions; moreover they also interact with each other. These mutual interactions influence the metal binding to a significant extent. In this study, the speciation of the heavy metal ions Zn and Ph was investigated in model

  12. Spectroscopic investigations of beam-plasma interactions in an ion plume

    Science.gov (United States)

    Ruyten, W. M.; Friedly, V. J.; Peng, X.; Celenza, J. A.; Keefer, D.

    1993-01-01

    We report the results of spectroscopic investigations of beam-plasma interactions in the plume from a 3 cm ion source operated on argon. Ion-electron, ion-neutral, and electron-neutral scattering are identified by studying the dependence of neutral and ion emission intensities on chamber pressure and mass flow rate, and by analyzing the emission lineshapes at a non-orthogonal angle to the plume axis. Through the Doppler shift, we are able to separate contributions from fast beam ions and fast charge-exchange neutrals on the one hand, and of slow neutrals and slow ions on the other. We discuss the application of this new technique to the characterization of beam plasma interactions in the downstream region of ion thruster engines, and its potential for identifying the processes which lead to grid erosion.

  13. The role of correlation and solvation in ion interactions with B-DNA

    Energy Technology Data Exchange (ETDEWEB)

    Sushko, Maria L.; Thomas, Dennis G.; Pabit, Suzette; Pollack, Lois; Onufriev, Alexey; Baker, Nathan A.

    2016-01-19

    Ionic atmosphere around nucleic acids plays important roles in biological function. Large-scale explicit solvent simulations coupled to experimental assays such as anomalous small-angle X-ray scattering (ASAXS) can provide important insights into the structure and energetics of the ionic atmosphere but are time- and resource-intensive. In this paper, we demonstrate the use of classical density functional theory to model DNA-ion interactions and explore the balance between ion-DNA, ion-water, and ion-ion interactions. In particular, we compute the distribution of RbCl, SrCl2, and CoHexCl3 (cobalt hexammine chlo- ride) around a B-form DNA molecule. The accuracy of the DFT calculations was assessed by comparison between simulated and experimental ASAXS curves. As expected, these calculations revealed significant differences between the monovalent, divalent, and trivalent cations. About half of the DNA-bound Rb+ ions penetrate into the minor groove of the DNA and half adsorb on the DNA strands. The fraction of cations in the minor groove decreases for the larger Sr2+ ions and becomes zero for CoHex3+ ions, which all adsorb on the DNA strands. The distribution of CoHex3+ ions is mainly determined by Coulomb interactions, while ion-correlation forces play a central role in the monovalent Rb+ distribution and a combination of ion-correlation and hydration forces affect the Sr2+ distribution around DNA.

  14. Nature of interactions between PEO-PPO-PEO triblock copolymers and lipid membranes: (I) effect of polymer hydrophobicity on its ability to protect liposomes from peroxidation.

    Science.gov (United States)

    Wang, Jia-Yu; Marks, Jeremy; Lee, Ka Yee C

    2012-09-10

    PEO-PPO-PEO triblock copolymers have opposing effects on lipid membrane integrity: they can behave either as membrane sealants or as membrane permeabilizers. To gain insights into their biomembrane activities, the fundamental interactions between a series of PEO-based polymers and phospholipid vesicles were investigated. Specifically, the effect of copolymer hydrophobicity on its ability to prevent liposomes from peroxidation was evaluated, and partitioning free energy and coefficient involved in the interactions were derived. Our results show that the high degree of hydrophilicity is a key feature of the copolymers that can effectively protect liposomes from peroxidation and the protective effect of the copolymers stems from their adsorption at the membrane surface without penetrating into the bilayer core. The origin of this protective effect induced by polymer absorption is attributed to the retardation of membrane hydration dynamics, which is further illustrated in the accompanying study on dynamic nuclear polarization (DNP)-derived hydration dynamics (Cheng, C.-Y.; Wang, J.-Y.; Kausik, R.; Lee, K. Y. C.; Han S. Biomacromolecules, 2012, DOI: 10.1021/bm300848c).

  15. Characterisation of nanomaterial hydrophobicity using engineered surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Desmet, Cloé; Valsesia, Andrea; Oddo, Arianna; Ceccone, Giacomo; Spampinato, Valentina; Rossi, François; Colpo, Pascal, E-mail: pascal.colpo@ec.europa.eu [Directorate Health, Consumer and Reference Materials, Consumer Products Safety Unit (Italy)

    2017-03-15

    Characterisation of engineered nanomaterials (NMs) is of outmost importance for the assessment of the potential risks arising from their extensive use. NMs display indeed a large variety of physico-chemical properties that drastically affect their interaction with biological systems. Among them, hydrophobicity is an important property that is nevertheless only slightly covered by the current physico-chemical characterisation techniques. In this work, we developed a method for the direct characterisation of NM hydrophobicity. The determination of the nanomaterial hydrophobic character is carried out by the direct measurement of the affinity of the NMs for different collectors. Each collector is an engineered surface designed in order to present specific surface charge and hydrophobicity degrees. Being thus characterised by a combination of surface energy components, the collectors enable the NM immobilisation with surface coverage in relation to their hydrophobicity. The experimental results are explained by using the extended DLVO theory, which takes into account the hydrophobic forces acting between NMs and collectors.

  16. Ion-atom interaction potential effects on the shape of energy spectra of ions backscattered by a thick target

    Energy Technology Data Exchange (ETDEWEB)

    Urmanov, A.R.; Bazhukov, S.I.; Puzanov, A.A.

    1986-06-01

    Based on the general Gaudsmit-Saunderson-Lewis model for multiple scattering in a semi-infinite medium, an expression accounting for the effects of multiple scattering on the shape of the backscattering energy spectrum has been obtained. This expression is represented by a series of ion angular distribution moments. The limits of the applicability of the small-angle approximation to the description of multiple scattering are defined. It is shown that the sensitivity of the angular distribution moments of multiple scattered ions to the type of ion-atom potential increases with an increase in the moment order. The possibility of investigation of the ion-atom interaction potential experimentally over a wide range of impact parameters by the backscattering method is discussed.

  17. Comprehensive Computational and Experimental Analysis of Biomaterial toward the Behavior of Imidazolium-Based Ionic Liquids: An Interplay between Hydrophilic and Hydrophobic Interactions.

    Science.gov (United States)

    Umapathi, Reddicherla; Vepuri, Suresh B; Venkatesu, Pannuru; Soliman, Mahmoud E

    2017-05-11

    by the ILs because of their hydrophobic interaction with the polymer.

  18. Cluster observations of trapped ions interacting with magnetosheath mirror modes

    Directory of Open Access Journals (Sweden)

    J. Soucek

    2011-06-01

    Full Text Available Mirror modes are among the most intense low frequency plasma wave phenomena observed in the magnetosheaths of magnetized planets. They appear as large amplitude non-propagating fluctuations in the magnetic field magnitude and plasma density. These structures are widely accepted to represent a non-linear stage of the mirror instability, dominant in plasmas with large ion beta and a significant ion temperature anisotropy T/T>1. It has long been recognized that the mirror instability both in the linear and non-linear stage is a kinetic process and that the behavior of resonant particles at small parallel velocities is crucial for its development and saturation. While the dynamics of the instability and the effect of trapped particles have been studied extensively in theoretical models and numerical simulations, only spurious observations of the trapped ions were published to date. In this work we used data from the Cluster spacecraft to perform the first detailed experimental study of ion velocity distribution associated with mirror mode oscillations. We show a conclusive evidence for the predicted cooling of resonant ions at small parallel velocities and heating of trapped ions at intermediate pitch angles.

  19. Cluster observations of trapped ions interacting with magnetosheath mirror modes

    Directory of Open Access Journals (Sweden)

    J. Soucek

    2011-06-01

    Full Text Available Mirror modes are among the most intense low frequency plasma wave phenomena observed in the magnetosheaths of magnetized planets. They appear as large amplitude non-propagating fluctuations in the magnetic field magnitude and plasma density. These structures are widely accepted to represent a non-linear stage of the mirror instability, dominant in plasmas with large ion beta and a significant ion temperature anisotropy T⊥/T∥>1. It has long been recognized that the mirror instability both in the linear and non-linear stage is a kinetic process and that the behavior of resonant particles at small parallel velocities is crucial for its development and saturation. While the dynamics of the instability and the effect of trapped particles have been studied extensively in theoretical models and numerical simulations, only spurious observations of the trapped ions were published to date. In this work we used data from the Cluster spacecraft to perform the first detailed experimental study of ion velocity distribution associated with mirror mode oscillations. We show a conclusive evidence for the predicted cooling of resonant ions at small parallel velocities and heating of trapped ions at intermediate pitch angles.

  20. Purification of chimeric heavy chain monoclonal antibody EG2-hFc using hydrophobic interaction membrane chromatography: an alternative to protein-A affinity chromatography.

    Science.gov (United States)

    Sadavarte, Rahul; Spearman, Maureen; Okun, Natalie; Butler, Michael; Ghosh, Raja

    2014-06-01

    Heavy chain monoclonal antibodies are being considered as alternative to whole-IgG monoclonal antibodies for certain niche applications. Protein-A chromatography which is widely used for purifying IgG monoclonal antibodies is also used for purifying heavy chain monoclonal antibodies as these molecules possess fully functional Fc regions. However, the acidic conditions used to elute bound antibody may sometimes also leach protein-A, which is immunotoxic. Low pH conditions also tend to make the mAb molecules unstable and prone to aggregation. Moreover, protein-A affinity chromatography does not remove aggregates already present in the feed. Hydrophobic interaction membrane chromatography (or HIMC) has already been studied as an alternative to protein-A chromatography for purifying whole-IgG monoclonal antibodies. This paper describes the use of HIMC for capturing a humanized chimeric heavy chain monoclonal antibody (EG2-hFC). Binding and eluting conditions were suitably optimized using pure EG2-hFC. Based on this, an HIMC method was developed for capture of EG2-hFC directly from cell culture supernatant. The EG2-hFc purity obtained in this single-step process was high. The glycan profiles of protein-A and HIMC purified monoclonal antibody samples were similar, clearly demonstrating that both techniques captured similarly glycosylated population of EG2-hFc. Moreover, this technique was able to resolve aggregates from monomeric form of the EG2-hFc. © 2014 Wiley Periodicals, Inc.

  1. [Thermodynamic approach to the selection of polyuronide sequestrants for protection of the human body from toxic metal ions. Interactions of polyuronides with lead ions].

    Science.gov (United States)

    Braudo, E E; Danilova, I V; Dianova, V T; Kobak, V V; Plashchina, I G

    2001-01-01

    Binding isotherms of Pb2+ ions with potassium pectate and potassium alginate with relatively low content of blocks of L-guluronic residues (20%) have been determined. Interactions of Pb2+ ions with polyuronides studied is cooperative. Maximum values of binding constants are an order of magnitude higher than previously determined ones for Ca2+ and Sr2+ ions. Along with ion-coordination ("stoichiometric") interactions, alginate is typified by so-called extra-stoichiometric binding of Pb2+ ions, which presumably proceeds by a coprecipitation mechanism. Limitations of the thermodynamic approach to the selection of sequestrants for human body protection from toxic metal ions are discussed.

  2. Incident ion charge state dependence of electron emission during slow multicharged ion-surface interactions

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, I.G. (Oak Ridge National Laboratory, Oak Ridge, TN 37831-6372 (United States) Joint Institute for Heavy Ion Research, Holifield Heavy Ion Research, Facility, Oak Ridge, TN 37831-6734 (United States)); Havener, C.C.; Overbury, S.H.; Robinson, M.T.; Zehner, D.M. (Oak Ridge National Laboratory, Oak Ridge, TN 37831-6732 (United States)); Zeijlmans van Emmichoven, P.A. (Oak Ridge National Laboratory, Oak Ridge, TN 37831-6732 (United States) Joint Institute for Heavy Ion Research, Holifield Heavy Ion Research Facility, Oak Ridge, TN 37821-6734 (United States)); Meyer, F.W. (Oak Ridge National Laboratory, Oak Ridge, TN 37831-6732 (United States))

    1993-06-05

    Characteristic variations in the total electron yield [gamma] as a function of crystal azimuthal orientation are reported for slow N[sup 2+], N[sup 5+] and N[sup 6+] ions incident on a Au(011) single crystal, together with measurements of [gamma] as a function of incident ion velocity. Kinetic electron emission is shown to arise predominantly in close collisions between incident ions and target atoms, and potential electron emission is found to be essentially constant within our present velocity range. The incident ion charge state is shown to play no role in kinetic electron emission. Extremely fast neutralization times of the order of 10[sup [minus]15] secs are needed to explain the observations.

  3. Ion-dipole interactions are asymptotically unscreened by water in dipolar nanopores, yielding patterned ion distributions

    OpenAIRE

    Leung, Kevin

    2008-01-01

    The permeation, rejection, and transport of electrolytes in water-filled nanopores are critical to ion current gating and desalinalion processes in synthetic porous membranes and the functions of biological ion channels. Mile the effects of confinement pore polarizability, and discrete channel charge sites have been much studied, the potentially dramatic impact of dipole-lined synthetic pores on electrolytes has seldom been addressed. Dipole layers naturally occur on the interior surfaces of ...

  4. Interaction of Hydroxyproline with Bivalent Metal Ions in Chemical ...

    African Journals Online (AJOL)

    Arecent technique involving the use of paper electrophoresis is described for the study of equilibria in binary complex systems in solution. The stability constants of the ML and ML2 complex species of some metal ions, namely beryllium(II) and cobalt(II), with hydroxyproline were determined in 0.1 mol L–1 perchloric acid ...

  5. Interaction of Hydroxyproline with Bivalent Metal Ions in Chemical ...

    African Journals Online (AJOL)

    NICO

    A recent technique involving the use of paper electrophoresis is described for the study of equilibria in binary complex systems in solution. The stability ... metal ions have several significant applications in biological systems.3–20 Beryllium is ... complexes and no reports on Be(II)-hydroxyproline binary complexes. In view of ...

  6. Donor-acceptor interactions between resonance-excited silver nanoparticles and halide ions in water solutions

    Science.gov (United States)

    Konstantinova, E. I.; Tikhomirova, N. S.; Samusev, I. G.; Slezhkin, V. A.; Bryukhanov, V. V.

    2017-10-01

    Donor-acceptor interactions between silver nanoparticles (NPs), resonance-excited by optical quanta of light, and halide ions are studied in aqueous solutions. It is shown that deactivation of the plasmon excitation of Ag NP proceeds according to the exchange mechanism of electron transfer. Plasmon excitation quenching constants are determined and a correlation between quenching and the donor properties of halide ions is found. The efficiency of electrostatic interaction between resonantly-excited Ag NPs and halide ions is studied, and their dipole moment is determined.

  7. Computational study of the effective three-ion interaction potentials in liquid metals with high density of electron gas

    OpenAIRE

    Vasiliu, E. V.

    2002-01-01

    Based on the many-body theory of metals in the third order of the perturbation expansion in electron-ion interaction pseudopotential, the potentials of pair and three-ion interactions are calculated in liquid lead, aluminium and beryllium at their melting temperatures. The reducible and irreducible three-ion interactions have an attractive nature on distances approximately equal to an average distance between ions in metals. It results in the shortening of average interatomic distance in an e...

  8. Ion beam profiling from the interaction with a freestanding 2D layer

    Directory of Open Access Journals (Sweden)

    Ivan Shorubalko

    2017-03-01

    Full Text Available Recent years have seen a great potential of the focused ion beam (FIB technology for the nanometer-scale patterning of a freestanding two-dimensional (2D layer. Experimentally determined sputtering yields of the perforation process can be quantitatively explained using the binary collision theory. The main peculiarity of the interaction between the ion beams and the suspended 2D material lies in the absence of collision cascades, featured by no interaction volume. Thus, the patterning resolution is directly set by the beam diameters. Here, we demonstrate pattern resolution beyond the beam size and precise profiling of the focused ion beams. We find out that FIB exposure time of individual pixels can influence the resultant pore diameter. In return, the pore dimension as a function of the exposure dose brings out the ion beam profiles. Using this method of determining an ion-beam point spread function, we verify a Gaussian profile of focused gallium ion beams. Graphene sputtering yield is extracted from the normalization of the measured Gaussian profiles, given a total beam current. Interestingly, profiling of unbeknown helium ion beams in this way results in asymmetry of the profile. Even triangular beam shapes are observed at certain helium FIB conditions, possibly attributable to the trimer nature of the beam source. Our method of profiling ion beams with 2D-layer perforation provides more information on ion beam profiles than the conventional sharp-edge scan method does.

  9. Resonant interactions between cometary ions and low frequency electromagnetic waves

    Science.gov (United States)

    Thorne, Richard M.; Tsurutani, Bruce T.

    1987-01-01

    The conditions for resonant wave amplification in a plasma with a ring-beam distribution which is intended to model pick-up ions in a cometary environment are investigated. The inclination between the interplanetary field and the solar wind is found to play a crucial role in governing both the resonant frequency and the growth rate of any unstable mode. It is suggested that the low-frequency MHD mode should experience the most rapid amplification for intermediate inclination. In the frame of the solar wind, such waves should propagate along the field in the direction upstream toward the sun with a phase speed lower than the beaming velocity of the pick-up ions. This mechanism may account for the presence of the interior MHD waves noted by satellites over a region surrounding comets Giacobini-Zinner and Halley.

  10. Students' Understanding of External Representations of the Potassium Ion Channel Protein, Part I: Affordances and Limitations of Ribbon Diagrams, Vines, and Hydrophobic/Polar Representations

    Science.gov (United States)

    Harle, Marissa; Towns, Marcy H.

    2012-01-01

    Research on external representations in biochemistry has uncovered student difficulties in comprehending and interpreting external representations. This project focuses on students' understanding of three external representations of the potassium ion channel protein. This is part I of a two-part study, which focuses on the affordances and…

  11. Hydrophobicity of carbohydrates and related hydroxy compounds.

    Science.gov (United States)

    Buttersack, Christoph

    2017-06-29

    The hydrophobic interaction of carbohydrates and other hydroxy compounds with a C18-modified silica gel column was measured with pure water as eluent, thereby expanding the range of measurements already published. The interaction is augmented by structure strengthening salts and decreasing temperature. Although the interaction of the solute with the hydrophobic interface is expected to only imperfectly reflect its state in aqueous bulk solution, the retention can be correlated to hydration numbers calculated from molecular mechanics studies given in the literature. No correlation can be established towards published hydration numbers obtained by physical methods (isentropic compressibility, O-17 NMR relaxation, terahertz spectroscopy, and viscosity). The hydrophobicity is discussed with respect to the chemical structure. It increases with the fraction and size of hydrophobic molecular surface regions. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Interaction of an ion bunch with a plasma slab

    Energy Technology Data Exchange (ETDEWEB)

    Krasovitskiy, V. B., E-mail: krasovit@mail.ru [Russian Academy of Sciences, Keldysh Institute of Applied Mathematics (Russian Federation); Turikov, V. A. [Peoples’ Friendship University of Russia (Russian Federation)

    2016-11-15

    Charge neutralization of a short ion bunch passing through a plasma slab is studied by means of numerical simulation. It is shown that a fraction of plasma electrons are trapped by the bunch under the action of the collective charge separation field. The accelerated electrons generated in this process excite beam−plasma instability, thereby violating the trapping conditions. The process of electron trapping is also strongly affected by the high-frequency electric field caused by plasma oscillations at the slab boundaries. It is examined how the degree of charge neutralization depends on the parameters of the bunch and plasma slab.

  13. A search for quarks produced in heavy-ion interactions

    CERN Multimedia

    2002-01-01

    We propose to search for free fractional charges produced in 225~GeV/A heavy-ion collisions at the SPS. A tank of mercury placed in the NA38 beam stop will serve both as a production target and as an absorber to stop reaction products. Mercury from the tank will subsequently be distilled.\\\\ \\\\ This process will decrease the amount of mercury that has to be processed by a factor of about $10^{5}$. The concentrate will be searched for quarks using the proven SFSU automated Millikan apparatus.\\\\ \\\\ This experiment will be sensitive to about one quark produced per $2 \\times 10^{8}$ beam particles.

  14. Hydrophobicity and its applications

    Science.gov (United States)

    Rios, Fabian

    Two different types of smart surfaces that are able to change their hydrophobicity by different stimuli are presented. In both types, the self assembled mono-layers have mixtures of hydrophobic moieties with active ligands. In the first, with biotin being the ligand, wetting changes induced by streptavidin binding onto the biotin were demonstrated and evaluated for different biotin concentrations on the surface and streptavidin concentrations in solution. In the second, aminated silanes allow wetting to be sensitive to pH changes and, by choosing their appropriate proportion of amines on the surface, can be made to switch hydrophobicity at a desired pH. Wetting of hydrophobic porous substrates induced by pressure, surfactants and pH was also studied for the pore diameters in the range 20-200 nm. Different mechanisms of wetting by amphiphiles were identified for high cmc and low cmc cases. In the latter, represented by phospholipids of the cell membrane, wetting occurs only in contact between the hydrophobic pores and the membrane, as was experimentally illustrated. It led to formulation of a new concept of drug delivery using hydrophobicity switching by membrane amphiphiles. Hydrophobic nanocontainers with dual release mechanism combining hydrophobicity switching by amphiphiles and by pH were explored as a potential new drug delivery system.

  15. Molecular microenvironments: Solvent interactions with nucleic acid bases and ions

    Science.gov (United States)

    Macelroy, R. D.; Pohorille, A.

    1986-01-01

    The possibility of reconstructing plausible sequences of events in prebiotic molecular evolution is limited by the lack of fossil remains. However, with hindsight, one goal of molecular evolution was obvious: the development of molecular systems that became constituents of living systems. By understanding the interactions among molecules that are likely to have been present in the prebiotic environment, and that could have served as components in protobiotic molecular systems, plausible evolutionary sequences can be suggested. When stable aggregations of molecules form, a net decrease in free energy is observed in the system. Such changes occur when solvent molecules interact among themselves, as well as when they interact with organic species. A significant decrease in free energy, in systems of solvent and organic molecules, is due to entropy changes in the solvent. Entropy-driven interactioins played a major role in the organization of prebiotic systems, and understanding the energetics of them is essential to understanding molecular evolution.

  16. A QMD description of the interaction of ion beams with matter

    CERN Document Server

    Garzelli, M V; Battistoni, G.; Cerutti, F.; Ferrari, A.; Gadioli, E.; Ballarini, F.; Ottolenghi, A.; Fasso, A.; Pinsky, Lawrence S.; Ranft, J.

    2006-01-01

    Heavy-ion collisions can be simulated by means of comprehensive approaches, to include the many different reaction mechanisms which may contribute. QMD models and their relativistic extensions are examples of these approaches based on Monte Carlo techniques. In this paper are shown some results obtained by coupling a new QMD code, which describes the fast stage of ion-ion collisions, to the evaporation /fission/Fermi break-up and photon de-excitation routines present in the FLUKA multipurpose Monte Carlo transport and interaction code. In particular, we compare the predicted neutron spectra to available experimental data from thin and thick target irradiations. We show also some predictions of particle and charged fragment fluences for the interaction of C and Fe ions with a thick PMMA target, which may be useful to assess the risk of side-effects in the hadron therapy of tumours.

  17. Interactions in 1-ethyl-3-methyl imidazolium tetracyanoborate ion pair: Spectroscopic and density functional study

    Energy Technology Data Exchange (ETDEWEB)

    Mao, James X.; Lee, Anita S.; Kitchin, John R.; Nulwala, Hunaid B.; Luebke, David R.; Damodaran, Krishnan

    2013-01-25

    Density Functional Theory is used to investigate a weakly coordinating room-temperature ionic liquid, 1-ethyl-3-methyl imidazolium tetracyanoborate ([Emim]{sup +}[TCB]{sup -}). Four locally stable conformers of the ion pair were located. Atoms-in-molecules (AIM) and electron density analysis indicated the existence of several hydrogen bonds. Further investigation through the Natural Bond Orbital (NBO) and Natural Energy Decomposition Analysis (NEDA) calculations provided insight into the origin of interactions in the [Emim]{sup +}[TCB]{sup -} ion pair. Strength of molecular interactions in the ionic liquid was correlated with frequency shifts of the characteristic vibrations of the ion pair. Harmonic vibrations of the ion pair were also compared with the experimental Raman and Infrared spectra. Vibrational frequencies were assigned by visualizing displacements of atoms around their equilibrium positions and through Potential Energy Distribution (PED) analysis.

  18. Interaction of intense laser pulses with atomic clusters: Measurements of ion emission, simulations and applications

    Energy Technology Data Exchange (ETDEWEB)

    Tisch, J.W.G. E-mail: john.tisch@ic.ac.uk; Hay, N.; Mendham, K.J.; Springate, E.; Symes, D.R.; Comley, A.J.; Mason, M.B.; Gumbrell, E.T.; Ditmire, T.; Smith, R.A.; Marangos, J.P.; Hutchinson, M.H.R

    2003-05-01

    This review paper provides a general introduction to the interaction of intense (>10{sup 15} W cm{sup -2}), femtosecond laser pulses with atomic clusters in the size range 500-10{sup 5} atoms. A nanoplasma model of the laser-cluster interaction is used to elucidate the underlying physics. Measurements of ion emission from the laser-cluster interaction are presented together with numerical simulations. Emerging applications are described.

  19. Interaction of a sodium ion with the water liquid-vapor interface

    Science.gov (United States)

    Wilson, M. A.; Pohorille, A.; Pratt, L. R.; MacElroy, R. D. (Principal Investigator)

    1989-01-01

    Molecular dynamics results are presented for the density profile of a sodium ion near the water liquid-vapor interface at 320 K. These results are compared with the predictions of a simple dielectric model for the interaction of a monovalent ion with this interface. The interfacial region described by the model profile is too narrow and the profile decreases too abruptly near the solution interface. Thus, the simple model does not provide a satisfactory description of the molecular dynamics results for ion positions within two molecular diameters from the solution interface where appreciable ion concentrations are observed. These results suggest that surfaces associated with dielectric models of ionic processes at aqueous solution interfaces should be located at least two molecular diameters inside the liquid phase. A free energy expense of about 2 kcal/mol is required to move the ion within two molecular layers of the free water liquid-vapor interface.

  20. Sodium ion interaction with psyllium husk (Plantago sp.)

    OpenAIRE

    Jimoh, M.A.; MacNaughtan, W.; Williams, H.E.L.; Greetham, D.; Linforth, R.L.; Fisk, Ian D.

    2016-01-01

    The nature of and factors effecting sodium interactions with psyllium were investigated in vitro. In a batch extraction system, psyllium mucilage gel retained at least 50% of sodium across a range of concentrations (5–300 mg sodium per g psyllium) and pH (2–10) environments. FTIR and Na NMR analyses of psyllium gels indicated that binding was complex with non-specific multi-site interactions. The potential use of psyllium husk as a binding agent for the reduction of bioavailable sodium was th...

  1. Modelling RF-plasma interaction in ECR ion sources

    Science.gov (United States)

    Mascali, David; Torrisi, Giuseppe; Galatà, Alessio; Sorbello, Gino; Castro, Giuseppe; Celona, Luigi; Lega, Lorenzo; Leonardi, Ornella; Mazzaglia, Maria; Naselli, Eugenia; Neri, Lorenzo; Gammino, Santo

    2017-10-01

    This paper describes three-dimensional self-consistent numerical simulations of wave propagation in magnetoplasmas of Electron cyclotron resonance ion sources (ECRIS). Numerical results can give useful information on the distribution of the absorbed RF power and/or efficiency of RF heating, especially in the case of alternative schemes such as mode-conversion based heating scenarios. Ray-tracing approximation is allowed only for small wavelength compared to the system scale lengths: as a consequence, full-wave solutions of Maxwell-Vlasov equation must be taken into account in compact and strongly inhomogeneous ECRIS plasmas. This contribution presents a multi-scale temporal domains approach for simultaneously including RF dynamics and plasma kinetics in a "cold-plasma", and some perspectives for "hot-plasma" implementation. The presented results rely with the attempt to establish a modal-conversion scenario of OXB-type in double frequency heating inside an ECRIS testbench.

  2. Modelling RF-plasma interaction in ECR ion sources

    Directory of Open Access Journals (Sweden)

    Mascali David

    2017-01-01

    Full Text Available This paper describes three-dimensional self-consistent numerical simulations of wave propagation in magnetoplasmas of Electron cyclotron resonance ion sources (ECRIS. Numerical results can give useful information on the distribution of the absorbed RF power and/or efficiency of RF heating, especially in the case of alternative schemes such as mode-conversion based heating scenarios. Ray-tracing approximation is allowed only for small wavelength compared to the system scale lengths: as a consequence, full-wave solutions of Maxwell-Vlasov equation must be taken into account in compact and strongly inhomogeneous ECRIS plasmas. This contribution presents a multi-scale temporal domains approach for simultaneously including RF dynamics and plasma kinetics in a “cold-plasma”, and some perspectives for “hot-plasma” implementation. The presented results rely with the attempt to establish a modal-conversion scenario of OXB-type in double frequency heating inside an ECRIS testbench.

  3. Interaction between lanthanide ions and Saccharomyces cerevisiae cells.

    Science.gov (United States)

    Ene, Cristian D; Ruta, Lavinia L; Nicolau, Ioana; Popa, Claudia V; Iordache, Virgil; Neagoe, Aurora D; Farcasanu, Ileana C

    2015-10-01

    Lanthanides are a group of non-essential elements with important imaging and therapeutic applications. Although trivalent lanthanide ions (Ln³⁺) are used as potent blockers of Ca²⁺ channels, the systematic studies correlating Ln³⁺ accumulation and toxicity to Ca²⁺ channel blocking activity are scarce. In this study, we made use of the eukaryotic model Saccharomyces cerevisiae to investigate the correlation between Ln³⁺ accumulation, their toxicity and their capacity to block the exogenous stress-induced Ca²⁺ influx into the cytosol. It was found that the Ln³⁺ blocked the Ca²⁺ entry into the yeast cells only when present at concentration high enough to allow rapid binding to cell surface. At lower concentrations, Ln³⁺ were taken up by the cell, but Ca²⁺ blockage was no longer achieved. At 1 mM concentration, all ions from the Ln³⁺ series could block Ca²⁺ entry into cytosol with the exception of La³⁺, and to a lesser extent, Pr³⁺ and Nd³⁺. The plasma membrane Ca²⁺-channel Cch1/Mid1 contributed to La³⁺ and Gd³⁺ entry into the cells, with a significant preference for La³⁺. The results open the possibility to obtain cells loaded with controlled amounts and ratios of Ln³⁺.

  4. Interaction of human endothelial cells and nickel-titanium materials modified with silicon ions

    Energy Technology Data Exchange (ETDEWEB)

    Lotkov, Aleksandr I., E-mail: lotkov@ispms.tsc.ru; Kashin, Oleg A., E-mail: okashin@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); Kudryavtseva, Yuliya A., E-mail: yulia-k1970@mail.ru; Antonova, Larisa V., E-mail: antonova.la@mail.ru; Matveeva, Vera G., E-mail: matveeva-vg@mail.ru; Sergeeva, Evgeniya A., E-mail: sergeewa.ew@yandex.ru [Research Institute for Complex Issues of Cardiovascular Diseases, Kemerovo, 650002 (Russian Federation); Kudryashov, Andrey N., E-mail: kudryashov@angioline.ru [Angioline Interventional Device Ltd, Novosibirsk, 630090 (Russian Federation)

    2015-10-27

    The paper studies the influence of chemical and phase compositions of NiTi surface layers modified with Si ions by plasma immersion implantation on their interaction with endothelial cells. It is shown that certain technological modes of Si ion implantation enhance the adhesion, proliferation, and viability of endothelial cells. It is found that the Si-modified NiTi surface is capable of stimulating the formation of capillary-like structures in the cell culture.

  5. Analysis of low energy electron emission arising during slow multicharged ion-surface interactions

    Energy Technology Data Exchange (ETDEWEB)

    Emmichoven, P.A.Z.v. (Oak Ridge National Laboratory, Oak Ridge, TN 37831-6372 (United States) Joint Institute for Heavy Ion Research, Holified Heavy Ion Research Facility, Oak Ridge, TN 37831-6734 (United States)); Havener, C.C. (Oak Ridge National Laboratory, Oak Ridge, TN 37831-6372 (United States)); Hughes, I.G. (Oak Ridge National Laboratory, Oak Ridge, TN 37831-6372 (United States) Joint Institute for Heavy Ion Research, Holifield Heavy Ion Research Facility, Oak Ridge, TN 37831-6374 (United States)); Zehner, D.M.; Meyer, F.W. (Oak Ridge National Laboratory, Oak Ridge, TN 37831-6732 (United States))

    1993-06-05

    We have undertaken a search for low energy electrons expected to arise in low energy multicharged ion-surface interactions when electrons captured into Rydberg levels of the projectile are promoted to the continuum as the projectile impacts the surface. Measurements are presented for 30--100 keV N[sup 2+] -N[sup 6+] ions incident at 20[degree] with the surface on Cu(001) and Au(011) single crystals, for a series of observation angles.

  6. Analysis of low energy electron emission arising during slow multicharged ion-surface interactions

    Energy Technology Data Exchange (ETDEWEB)

    Zeijlmans van Emmichoven, P.A.; Hughes, I.G. (Oak Ridge National Lab., TN (United States) Joint Institute for Heavy Ion Research, Holifield Heavy Ion Research Facility, Oak Ridge, TN (United States)); Havener, C.C.; Zehner, D.M.; Meyer, F.W. (Oak Ridge National Lab., TN (United States))

    1992-01-01

    We have undertaken a search for low energy electrons expected to arise in low energy multicharged ion-surface interactions when electrons captured into Rydberg levels of the projectile are promoted to the continuum as the projectile impacts the surface. Measurements are presented for 30--100 keV N{sup 2+} -- N{sup 6+} ions incident at 20{sup o} with the surface on Cu(001) and Au(0ll) single crystals, for a series of observation angles.

  7. Nickel (II) Ions Interaction with Polynucleotides and DNA of Different GC Composition

    OpenAIRE

    Bregadze, Vasil G.; Khutsishvili, Irina G.; Melikishvili, Sophie Z.; Melikishvili, Zaza G.

    2009-01-01

    The goal of the work was to study the role of GC alternative dimmers in the binding of DNA with Ni (II) ions. The method of ultraviolet difference spectroscopy has been applied to investigate Ni (II) ions interactions with DNA extracted from Clostridium perfringens, Mice liver (C3HA line), Calf thymus, Salmon sperm, Herring sperm, E.coli, Micrococcus luteus and polynucleotides Poly (dA-dT)xPoly (dA-dT), Poly (dG)x Poly (dC), Poly (dG-dC)xPoly (dG-dC). It is shown that Ni (II) ions at outer-sp...

  8. Ion beam experiments for the study of plasma-surface interactions

    Science.gov (United States)

    Karahashi, Kazuhiro; Hamaguchi, Satoshi

    2014-06-01

    Experimental studies based on mass-selected ion beams are reviewed as a means to examine plasma-surface interactions for industrial plasma processing. Plasma etching and deposition processes widely used in the microelectronics industry exploit surface chemical reactions induced by plasmas. Such reactions typically result from a conglomeration of complex interactions of the surface material with incident free radicals and ions. While it is in general difficult to analyse individual surface reactions separately in a plasma system, ion and/or charge-neutral beam experiments allow one to analyse specific surface reactions involving only selected gaseous species. In this review, experiments on beam-surface interactions are discussed in detail and beam reaction data for silicon surfaces are presented as sample data.

  9. Sodium ion interaction with psyllium husk (Plantago sp.).

    Science.gov (United States)

    Jimoh, M A; MacNaughtan, W; Williams, H E L; Greetham, D; Linforth, R L; Fisk, I D

    2016-09-14

    The nature of and factors effecting sodium interactions with psyllium were investigated in vitro. In a batch extraction system, psyllium mucilage gel retained at least 50% of sodium across a range of concentrations (5-300 mg sodium per g psyllium) and pH (2-10) environments. FTIR and Na NMR analyses of psyllium gels indicated that binding was complex with non-specific multi-site interactions. The potential use of psyllium husk as a binding agent for the reduction of bioavailable sodium was therefore evaluated. The binding of sodium at physiologically relevant conditions (pH 1.2 (stomach) and 6.8 (intestine)) was studied in a gastrointestinal tract (GIT) pH simulated model. Results show consistently high sodium retention (∼50%) across the GIT model and less than 20% loss of bound sodium under the simulated intestinal pH conditions after repeated washings.

  10. DFT study on the interaction between hydrogen sulfide ions and cerussite (110) surface

    Science.gov (United States)

    Feng, Qicheng; Wen, Shuming; Deng, Jiushuai; Zhao, Wenjuan

    2017-02-01

    The interaction between hydrogen sulfide ions (HS-) and the cerussite surface was simulated using density functional theory (DFT) calculations. The calculated results show that Pb atoms are the dominating active sites for the subsequent reaction on the cerussite (110) surface. The S atom in HS- ions can readily interact with the Pb atoms at the cerussite surface layers with the interaction energy of -5.19 eV, resulting in the formation of lead sulfide species. An obvious difference occurs when HS- ions interact with the various Pb atoms on the cerussite surface. The density of state analysis reveals that the Pb 6p orbital at the mineral surface layers and S 3p orbital from HS- ions are overlapped between -1.5 and 0.5 eV near the Fermi level, indicating a stable chemical adsorption. The Mulliken population result suggests that the electron transfer exists between the bonding atoms and the oxidation of the HS- ions is involved in the adsorption process. This study provides an insight into the sulfidization mechanism at an atomic level, and further confirms the experimental phenomenon proposed in our previous work.

  11. Hexagonal plaquette spin-spin interactions and quantum magnetism in a two-dimensional ion crystal

    Science.gov (United States)

    Nath, R.; Dalmonte, M.; Glaetzle, A. W.; Zoller, P.; Schmidt-Kaler, F.; Gerritsma, R.

    2015-06-01

    We propose a trapped ion scheme en route to realize spin Hamiltonians on a Kagome lattice which, at low energies, are described by emergent {{{Z}}}2 gauge fields, and support a topological quantum spin liquid ground state. The enabling element in our scheme is the hexagonal plaquette spin-spin interactions in a two-dimensional ion crystal. For this, the phonon-mode spectrum of the crystal is engineered by standing-wave optical potentials or by using Rydberg excited ions, thus generating localized phonon-modes around a hexagon of ions selected out of the entire two-dimensional crystal. These tailored modes can mediate spin-spin interactions between ion-qubits on a hexagonal plaquette when subject to state-dependent optical dipole forces. We discuss how these interactions can be employed to emulate a generalized Balents-Fisher-Girvin model in minimal instances of one and two plaquettes. This model is an archetypical Hamiltonian in which gauge fields are the emergent degrees of freedom on top of the classical ground state manifold. Under realistic situations, we show the emergence of a discrete Gauss’s law as well as the dynamics of a deconfined charge excitation on a gauge-invariant background using the two-plaquettes trapped ions spin-system. The proposed scheme in principle allows further scaling in a future trapped ion quantum simulator, and we conclude that our work will pave the way towards the simulation of emergent gauge theories and quantum spin liquids in trapped ion systems.

  12. Electron Bubbles in Superfluid (3) 3 He-A: Exploring the Quasiparticle-Ion Interaction

    Science.gov (United States)

    Shevtsov, Oleksii; Sauls, J. A.

    2017-06-01

    When an electron is forced into liquid ^3He, it forms an "electron bubble", a heavy ion with radius, R˜eq 1.5 nm, and mass, M˜eq 100 m_3, where m_3 is the mass of a ^3He atom. These negative ions have proven to be powerful local probes of the physical properties of the host quantum fluid, especially the excitation spectra of the superfluid phases. We recently developed a theory for Bogoliubov quasiparticles scattering off electron bubbles embedded in a chiral superfluid that provides a detailed understanding of the spectrum of Weyl Fermions bound to the negative ion, as well as a theory for the forces on moving electron bubbles in superfluid ^3He-A (Shevtsov and Sauls in Phys Rev B 94:064511, 2016). This theory is shown to provide quantitative agreement with measurements reported by the RIKEN group (Ikegami et al. in Science 341(6141):59, 2013) for the drag force and anomalous Hall effect of moving electron bubbles in superfluid ^3He-A. In this report, we discuss the sensitivity of the forces on the moving ion to the effective interaction between normal-state quasiparticles and the ion. We consider models for the quasiparticle-ion (QP-ion) interaction, including the hard-sphere potential, constrained random-phase-shifts, and interactions with short-range repulsion and intermediate-range attraction. Our results show that the transverse force responsible for the anomalous Hall effect is particularly sensitive to the structure of the QP-ion potential and that strong short-range repulsion, captured by the hard-sphere potential, provides an accurate model for computing the forces acting on the moving electron bubble in superfluid 3He-A.

  13. Ions in solution basic principles of chemical interactions

    CERN Document Server

    Burgess, J

    1999-01-01

    This outline of the principles and chemical interactions in inorganic solution chemistry delivers a course module in an area of considerable complexity. Problems with solutions and tutorial hints to test comprehension have been added as a feature to check readers' understanding and assist self-study. Exercises and projects are also provided to help readers deepen and extend their knowledge and understanding. Inorganic solution chemistry is treated thoroughly Emphasis is placed upon NMR, UV-VIS, IR Raman spectroscopy, X-ray diffraction, and such topics as acid-base behaviour, stability constants and kinetics.

  14. Monte Carlo studies of the interaction of relativistic ions with nuclear emulsion

    Energy Technology Data Exchange (ETDEWEB)

    Hashemi-Nezhad, S.R., E-mail: reza@physics.usyd.edu.au [School of Physics, A28, University of Sydney, NSW 2006 (Australia); Brandt, R. [Kernchemie, Fachbereich Chemie, Philipps-Universität, 35043 Marburg (Germany); Ditlov, V.A. [Alikhanov Institute of Theoretical and Experimental Physics, Moscow (Russian Federation); Firu, E. [Bucharest Institute of Space Sciences, Bucharest (Romania); Ganssauge, E. [Fachbereich Physik, Philipps-Universität, Marburg (Germany); Haiduc, M.; Neagu, A.T. [Bucharest Institute of Space Sciences, Bucharest (Romania); Westmeier, W. [Kernchemie, Fachbereich Chemie, Philipps-Universität, 35043 Marburg (Germany); Dr. Westmeier GmbH, 35085 Ebsdorfergrund (Germany)

    2017-01-01

    Interaction of high energy heavy ions with nuclear emulsion simulated using MCNPX 2.7 and its associated Monte Carlo codes. The simulations were performed for interactions of 4.1 AGeV/c {sup 22}Ne ions with nuclear emulsion event by event via batch files written for this purpose. It is shown that MCNPX correctly simulates the spallation as well as “complete destruction” interactions using the same physics principles and models. Cross-sections for interaction of 4.1 AGeV/c {sup 22}Ne ions with emulsion, Ag and Br in emulsion and rest of the nuclei in the emulsion were determined. Good agreements between calculations and experimental results were obtained. - Highlights: • Interaction of 4.1 A GeV/c {sup 22}Ne ions with Ilford G5 nuclear emulsion studies using MCNPX 2.7 Monte Carlo code. • Procedures for simulations of the intaractions event by event have been described. • Spallation and “total destruction” events in the emulsion were investigated. • MC predictions are in good agreement with experimental findings.

  15. Attractive double-layer forces between neutral hydrophobic and neutral hydrophilic surfaces.

    Science.gov (United States)

    Lima, Eduardo R A; Boström, Mathias; Schwierz, Nadine; Sernelius, Bo E; Tavares, Frederico W

    2011-12-01

    The interaction between surface patches of proteins with different surface properties has a vital role to play driving conformational changes in proteins in different salt solutions. We demonstrate the existence of ion-specific attractive double-layer forces between neutral hydrophobic and hydrophilic surfaces in the presence of certain salt solutions. This is performed by solving a generalized Poisson-Boltzmann equation for two unequal surfaces. In the calculations, we utilize parametrized ion-surface potentials and dielectric-constant profiles deduced from recent non-primitive-model molecular dynamics simulations that partially account for molecular structure and hydration effects.

  16. Understanding the interactions of neptunium and plutonium ions with graphene oxide: scalar-relativistic DFT investigations.

    Science.gov (United States)

    Wu, Qun-Yan; Lan, Jian-Hui; Wang, Cong-Zhi; Zhao, Yu-Liang; Chai, Zhi-Fang; Shi, Wei-Qun

    2014-11-06

    Due to the vast application potential of graphene oxide (GO)-based materials in nuclear waste processing, it is of pivotal importance to investigate the interaction mechanisms between actinide cations such as Np(V) and Pu(IV, VI) ions and GO. In this work, we have considered four types of GOs modified by hydroxyl, carboxyl, and carbonyl groups at the edge and epoxy group on the surface, respectively. The structures, bonding nature, and binding energies of Np(V) and Pu(IV, VI) complexes with GOs have been investigated systematically using scalar-relativistic density functional theory (DFT). Geometries and harmonic frequencies suggest that Pu(IV) ions coordinate more easily with GOs compared to Np(V) and Pu(VI) ions. NBO and electron density analyses reveal that the coordination bond between Pu(IV) ions and GO possesses more covalency, whereas for Np(V) and Pu(VI) ions electrostatic interaction dominates the An-OG bond. The binding energies in aqueous solution reveal that the adsorption abilities of all GOs for actinide ions follow the order of Pu(IV) > Pu(VI) > Np(V), which is in excellent agreement with experimental observations. It is expected that this study can provide useful information for developing more efficient GO-based materials for radioactive wastewater treatment.

  17. Proton-ion collisions: behind the scenes of an exotic interaction

    CERN Document Server

    Antonella Del Rosso

    2012-01-01

    Protons to the right, ions to the left: the basic principle of proton-ion collisions at the LHC might seem straightforward. However, this is an almost unprecedented mode of collider operation, certainly unique at the energy provided by the LHC. In addition to being a remarkable technical achievement, this interaction between a proton and an ion can potentially contribute a lot to the understanding of the properties of matter in its primordial state.   Prior to last week, the LHC had only collided protons with protons and lead ions with lead ions. These were indeed the two operational schemes the LHC was designed for. However, since science can often evolve in directions that were not necessarily expected at the beginning of a project, over the years the scientific community has become more and more interested in the hybrid type of interaction – that between protons and ions. Last week’s collisions were only a test for the teams involved in the operation of the LHC, in prepara...

  18. MODEL PSEUDOPOTENTIAL OF THE ELECTRON - NEGATIVE ION INTERACTION

    Directory of Open Access Journals (Sweden)

    Yu.Rudavskii

    2003-01-01

    Full Text Available Generalization of the Anderson model to describe the states of electronegative impurities in liquid-metal alloys is the main aim of the present paper. The effects of the random inner field on the charge impurity states is accounted for selfconsistently. Qualitative and quantitative estimation of hamiltonian parameters has been carried out. The limits of the proposed model applicability to a description of real systems are considered. Especially, the case of the oxygen impurity in liquid sodium is studied. The modelling of the proper electron-ionic interaction potential is the main goal of the paper. The parameters of the proposed pseudopotential are analyzed in detail. The comparison with other model potentials have been carried out. Resistivity of liquid sodium containing the oxygen impurities is calculated with utilizing the form-factor of the proposed model potential. Dependence of the resistivity on impurity concentration and on the charge states is received.

  19. Electrohydrodynamics near hydrophobic surfaces.

    Science.gov (United States)

    Maduar, S R; Belyaev, A V; Lobaskin, V; Vinogradova, O I

    2015-03-20

    We show that an electro-osmotic flow near the slippery hydrophobic surface depends strongly on the mobility of surface charges, which are balanced by counterions of the electrostatic diffuse layer. For a hydrophobic surface with immobile charges, the fluid transport is considerably amplified by the existence of a hydrodynamic slippage. In contrast, near the hydrophobic surface with mobile adsorbed charges, it is also controlled by an additional electric force, which increases the shear stress at the slipping interface. To account for this, we formulate electrohydrodynamic boundary conditions at the slipping interface, which should be applied to quantify electro-osmotic flows instead of hydrodynamic boundary conditions. Our theoretical predictions are fully supported by dissipative particle dynamics simulations with explicit charges. These results lead to a new interpretation of zeta potential of hydrophobic surfaces.

  20. Characterisation of nanomaterial hydrophobicity using engineered surfaces.

    Science.gov (United States)

    Desmet, Cloé; Valsesia, Andrea; Oddo, Arianna; Ceccone, Giacomo; Spampinato, Valentina; Rossi, François; Colpo, Pascal

    2017-01-01

    Characterisation of engineered nanomaterials (NMs) is of outmost importance for the assessment of the potential risks arising from their extensive use. NMs display indeed a large variety of physico-chemical properties that drastically affect their interaction with biological systems. Among them, hydrophobicity is an important property that is nevertheless only slightly covered by the current physico-chemical characterisation techniques. In this work, we developed a method for the direct characterisation of NM hydrophobicity. The determination of the nanomaterial hydrophobic character is carried out by the direct measurement of the affinity of the NMs for different collectors. Each collector is an engineered surface designed in order to present specific surface charge and hydrophobicity degrees. Being thus characterised by a combination of surface energy components, the collectors enable the NM immobilisation with surface coverage in relation to their hydrophobicity. The experimental results are explained by using the extended DLVO theory, which takes into account the hydrophobic forces acting between NMs and collectors. Graphical abstractDetermination of hydrophobicity character of nanomaterials by measuring their affinity to engineered surfaces.

  1. FTIR spectroscopy structural analysis of the interaction between Lactobacillus kefir S-layers and metal ions

    Science.gov (United States)

    Gerbino, E.; Mobili, P.; Tymczyszyn, E.; Fausto, R.; Gómez-Zavaglia, A.

    2011-02-01

    FTIR spectroscopy was used to structurally characterize the interaction of S-layer proteins extracted from two strains of Lactobacillus kefir (the aggregating CIDCA 8348 and the non-aggregating JCM 5818) with metal ions (Cd +2, Zn +2, Pb +2 and Ni +2). The infrared spectra indicate that the metal/protein interaction occurs mainly through the carboxylate groups of the side chains of Asp and Glut residues, with some contribution of the NH groups belonging to the peptide backbone. The frequency separation between the νCOO - anti-symmetric and symmetric stretching vibrations in the spectra of the S-layers in presence of the metal ions was found to be ca. 190 cm -1 for S-layer CIDCA 8348 and ca. 170 cm -1 for JCM 5818, denoting an unidentate coordination in both cases. Changes in the secondary structures of the S-layers induced by the interaction with the metal ions were also noticed: a general trend to increase the amount of β-sheet structures and to reduce the amount of α-helices was observed. These changes allow the proteins to adjust their structure to the presence of the metal ions at minimum energy expense, and accordingly, these adjustments were found to be more important for the bigger ions.

  2. Electron-Anode Interactions in Particle-in-Cell Simulations of Applied-B Ion Diodes

    Energy Technology Data Exchange (ETDEWEB)

    Bailey, J.E.; Cuneo, M.D.; Johnson, D.J.; Mehlhorn, T.A.; Pointon, T.D.; Renk, T.J.; Stygar, W.A.; Vesey, R.A.

    1998-11-12

    Particle-in-cell simulations of applied-B ion diodes using the QUICKSILVER code have been augmented with Monte Carlo calculations of electron-anode interactions (reflection and energy deposition). Extraction diode simulations demonstrate a link between the instability evolution and increased electron loss and anode heating. Simulations of radial and extraction ion diodes show spatial non-uniformity in the predicted electron loss profile leading to hot spots on the anode that rapidly exceed the 350-450 {degree}C range, known to be sufficient for plasma formation on electron-bombarded surfaces. Thermal resorption calculations indicate complete resorption of contaminants with 15-20 kcal/mole binding energies in high-dose regions of the anode during the power pulse. Comparisons of parasitic ion emission simulations and experiment show agreement in some aspects; but also highlight the need for better ion source, plasma, and neutral gas models.

  3. Concentration Dependent Ion-Protein Interaction Patterns Underlying Protein Oligomerization Behaviours.

    Science.gov (United States)

    Batoulis, Helena; Schmidt, Thomas H; Weber, Pascal; Schloetel, Jan-Gero; Kandt, Christian; Lang, Thorsten

    2016-04-07

    Salts and proteins comprise two of the basic molecular components of biological materials. Kosmotropic/chaotropic co-solvation and matching ion water affinities explain basic ionic effects on protein aggregation observed in simple solutions. However, it is unclear how these theories apply to proteins in complex biological environments and what the underlying ionic binding patterns are. Using the positive ion Ca(2+) and the negatively charged membrane protein SNAP25, we studied ion effects on protein oligomerization in solution, in native membranes and in molecular dynamics (MD) simulations. We find that concentration-dependent ion-induced protein oligomerization is a fundamental chemico-physical principle applying not only to soluble but also to membrane-anchored proteins in their native environment. Oligomerization is driven by the interaction of Ca(2+) ions with the carboxylate groups of aspartate and glutamate. From low up to middle concentrations, salt bridges between Ca(2+) ions and two or more protein residues lead to increasingly larger oligomers, while at high concentrations oligomers disperse due to overcharging effects. The insights provide a conceptual framework at the interface of physics, chemistry and biology to explain binding of ions to charged protein surfaces on an atomistic scale, as occurring during protein solubilisation, aggregation and oligomerization both in simple solutions and membrane systems.

  4. Electrophoretic studies of polygalacturonate oligomers and their interactions with metal ions.

    Science.gov (United States)

    Wiedmer, S K; Cassely, A; Hong, M; Novotny, M V; Riekkola, M L

    2000-09-01

    Polygalacturonic acid, a linear homopolysaccharide, was investigated by capillary electrophoresis (CE) using linear polyacrylamide-coated capillaries and laser-induced fluorescence (LIF) detection. A successful separation of its fluorescently labeled oligomers was achieved through sieving in polyacrylamide entangled matrices. The reaction conditions for the derivatization of polygalacturonic acid were optimized. In studying the interactions between polygalacturonic acid and various metal ions, the end-label, free-solution electrophoretic (ELFSE) technique, developed earlier in our laboratory (Sudor, J., Novotny, M. V., Anal. Chem. 1995, 67, 4205-4209) was found preferable to the sieving method. ELFSE is fast and convenient in that no polymer solutions are needed for the separation. The investigation showed that for the moderately large oligomers, the strongest binding occurred with calcium and cadmium ions, while the smallest interaction was observed with magnesium ions.

  5. Non-linear interaction between high energy ions and MHD-modes

    Energy Technology Data Exchange (ETDEWEB)

    Bergkvist, Tommy

    2001-12-01

    When heating a fusion plasma with ICRE or NBI a non-Maxwellian distribution function with high energy ions is created. Ions which are in resonance with a MHD mode will interact with the electric field from the mode and in some circumstances energy will flow from the particles to the mode or opposite. A quasi-linear model for the interaction between high energy ions and a MHD mode has been developed. To solve the time evolution of the MHD mode a module has been implemented into the Monte Carlo code FIDO, which is used for calculating a 3-dimensional distribution function. The model has been tested for an internal kink mode during fishbone oscillations.

  6. Polymerization effect of electrolytes on hydrogen-bonding cryoprotectants: ion-dipole interactions between metal ions and glycerol.

    Science.gov (United States)

    Weng, Lindong; Elliott, Gloria D

    2014-12-11

    Protectants which are cell membrane permeable, such as glycerol, have been used effectively in the cryopreservation field for a number of decades, for both slow cooling and vitrification applications. In the latter case, the glass transition temperature (Tg) of the vitrification composition is key to its application, dictating the ultimate storage conditions. It has been observed that the addition of some electrolytes to glycerol, such as MgCl2, could elevate the Tg of the mixture, thus potentially providing more storage condition flexibility. The microscopic mechanisms that give rise to the Tg-enhancing behavior of these electrolytes are not yet well understood. The current study focuses on molecular dynamics simulation of glycerol mixed with a variety of metal chlorides (i.e., NaCl, KCl, MgCl2, and CaCl2), covering a temperature range that spans both the liquid and glassy states. The characteristics of the ion-dipole interactions between metal cations and hydroxyl groups of glycerol were analyzed. The interruption of the original hydrogen-bonding network among glycerol molecules by the addition of ions was also investigated in the context of hydrogen-bonding quantity and lifetime. Divalent metal cations were found to significantly increase the Tg by strengthening the interacting network in the electrolyte/glycerol mixture via strong cation-dipole attractions. In contrast, monovalent cations increased the Tg insignificantly, as the cation-dipole attraction was only slightly stronger than the original hydrogen-bonding network among glycerol molecules. The precursor of crystallization of NaCl and KCl was also observed in these compositions, potentially contributing to weak Tg-enhancing ability. The Tg-enhancing mechanisms elucidated in this study suggest a structure-enhancing role for divalent ions that could be of benefit in the design of protective formulations for biopreservation purposes.

  7. Electromagnetic Waves Dispersion and Interaction of an Annular Beam-Ion Channel System in Plasma Waveguide

    Directory of Open Access Journals (Sweden)

    Jixiong Xiao

    2017-01-01

    Full Text Available A linear theory for the electromagnetic properties and interactions of an annular beam-ion channel system in plasma waveguide is presented. The dispersion relations for two families of propagating modes, including the electrostatic and transverse magnetic modes, are derived. The dependencies of the dispersion behavior and interaction for different wave modes on the thickness of the annular beam and betatron oscillation frequency are studied in detail by numerical calculations. The results show that the inner and outer radii of the beam have different influences on propagation properties of the electrostatic and electromagnetic modes with different betatron oscillation parameters. In the weak ion channel situation, the two types of electrostatic waves, that is, space charge and betatron modes, have no interaction with the transverse magnetic modes. However, in the strong ion channel situation, the transverse magnetic modes will have two branches and a low frequency mode emerged as the new branch. In this case, compared with the solid beam case, the betatron modes not only can interact with the high frequency branch at small wavenumber but also can interact with the low frequency branch at large wavenumber.

  8. Molecular dynamics simulations of hydrophobous ions at the liquid-liquid interfaces: case of dicarbollide anions as synergy agents and of ionic liquids as extracting medium; Simulations par dynamique moleculaire d'ions hydrophobes aux interfaces liquide - liquide: le cas des anions dicarbollides comme agents de synergie et celui des liquides ioniques comme milieu extractant

    Energy Technology Data Exchange (ETDEWEB)

    Chevrot, G

    2008-01-15

    Based on molecular dynamics simulations, we first describe the distribution of dicarbollide salts (CCD{sup -}, Mn{sup +}) in concentrated monophasic solutions (water, chloroform, octanol, nitrobenzene) and in the corresponding biphasic 'oil' - water solutions. We point to the importance of surface activity of the CCD{sup -}s and of their self-aggregation in water, with marked counterions effects, and we explain the synergistic effect of CCD{sup -}s in the Eu{sup 3+} extraction by BTP ligands. In the second part of the thesis we report exploratory simulations on the extraction of Sr{sup 2+} by 18-crown-6 to an hydrophobic ionic liquid ([BMI][PF6]), focusing on the liquid - liquid interface. Analogies and differences with a classical aqueous interface are outlined. (author)

  9. Charged patchy particle models in explicit salt: Ion distributions, electrostatic potentials, and effective interactions.

    Science.gov (United States)

    Yigit, Cemil; Heyda, Jan; Dzubiella, Joachim

    2015-08-14

    We introduce a set of charged patchy particle models (CPPMs) in order to systematically study the influence of electrostatic charge patchiness and multipolarity on macromolecular interactions by means of implicit-solvent, explicit-ion Langevin dynamics simulations employing the Gromacs software. We consider well-defined zero-, one-, and two-patched spherical globules each of the same net charge and (nanometer) size which are composed of discrete atoms. The studied mono- and multipole moments of the CPPMs are comparable to those of globular proteins with similar size. We first characterize ion distributions and electrostatic potentials around a single CPPM. Although angle-resolved radial distribution functions reveal the expected local accumulation and depletion of counter- and co-ions around the patches, respectively, the orientation-averaged electrostatic potential shows only a small variation among the various CPPMs due to space charge cancellations. Furthermore, we study the orientation-averaged potential of mean force (PMF), the number of accumulated ions on the patches, as well as the CPPM orientations along the center-to-center distance of a pair of CPPMs. We compare the PMFs to the classical Derjaguin-Verwey-Landau-Overbeek theory and previously introduced orientation-averaged Debye-Hückel pair potentials including dipolar interactions. Our simulations confirm the adequacy of the theories in their respective regimes of validity, while low salt concentrations and large multipolar interactions remain a challenge for tractable theoretical descriptions.

  10. Charged patchy particle models in explicit salt: Ion distributions, electrostatic potentials, and effective interactions

    Energy Technology Data Exchange (ETDEWEB)

    Yigit, Cemil; Dzubiella, Joachim, E-mail: joachim.dzubiella@helmholtz-berlin.de [Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin, 14109 Berlin (Germany); Helmholtz Virtual Institute “Multifunctional Biomaterials for Medicine,” 14513 Teltow (Germany); Institut für Physik, Humboldt-Universität zu Berlin, 12489 Berlin (Germany); Heyda, Jan [Department of Physical Chemistry, University of Chemistry and Technology, Prague, 166 28 Praha 6 (Czech Republic)

    2015-08-14

    We introduce a set of charged patchy particle models (CPPMs) in order to systematically study the influence of electrostatic charge patchiness and multipolarity on macromolecular interactions by means of implicit-solvent, explicit-ion Langevin dynamics simulations employing the Gromacs software. We consider well-defined zero-, one-, and two-patched spherical globules each of the same net charge and (nanometer) size which are composed of discrete atoms. The studied mono- and multipole moments of the CPPMs are comparable to those of globular proteins with similar size. We first characterize ion distributions and electrostatic potentials around a single CPPM. Although angle-resolved radial distribution functions reveal the expected local accumulation and depletion of counter- and co-ions around the patches, respectively, the orientation-averaged electrostatic potential shows only a small variation among the various CPPMs due to space charge cancellations. Furthermore, we study the orientation-averaged potential of mean force (PMF), the number of accumulated ions on the patches, as well as the CPPM orientations along the center-to-center distance of a pair of CPPMs. We compare the PMFs to the classical Derjaguin-Verwey-Landau-Overbeek theory and previously introduced orientation-averaged Debye-Hückel pair potentials including dipolar interactions. Our simulations confirm the adequacy of the theories in their respective regimes of validity, while low salt concentrations and large multipolar interactions remain a challenge for tractable theoretical descriptions.

  11. Interactions in ion pairs of protic ionic liquids: Comparison with aprotic ionic liquids

    Energy Technology Data Exchange (ETDEWEB)

    Tsuzuki, Seiji, E-mail: s.tsuzuki@aist.go.jp [Research Initiative of Computational Sciences (RICS), Nanosystem Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Shinoda, Wataru [Health Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan); Miran, Md. Shah; Kinoshita, Hiroshi; Yasuda, Tomohiro; Watanabe, Masayoshi [Department of Chemistry and Biotechnology, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501 (Japan)

    2013-11-07

    The stabilization energies for the formation (E{sub form}) of 11 ion pairs of protic and aprotic ionic liquids were studied by MP2/6-311G{sup **} level ab initio calculations to elucidate the difference between the interactions of ions in protic ionic liquids and those in aprotic ionic liquids. The interactions in the ion pairs of protic ionic liquids (diethylmethylammonium [dema] and dimethylpropylammonium [dmpa] based ionic liquids) are stronger than those of aprotic ionic liquids (ethyltrimethylammonium [etma] based ionic liquids). The E{sub form} for the [dema][CF{sub 3}SO{sub 3}] and [dmpa][CF{sub 3}SO{sub 3}] complexes (−95.6 and −96.4 kcal/mol, respectively) are significantly larger (more negative) than that for the [etma][CF{sub 3}SO{sub 3}] complex (−81.0 kcal/mol). The same trend was observed for the calculations of ion pairs of the three cations with the Cl{sup −}, BF{sub 4}{sup −}, TFSA{sup −} anions. The anion has contact with the N–H bond of the dema{sup +} or dmpa{sup +} cations in the most stable geometries of the dema{sup +} and dmpa{sup +} complexes. The optimized geometries, in which the anions locate on the counter side of the cations, are 11.0–18.0 kcal/mol less stable, which shows that the interactions in the ions pairs of protic ionic liquids have strong directionality. The E{sub form} for the less stable geometries for the dema{sup +} and dmpa{sup +} complexes are close to those for the most stable etma{sup +} complexes. The electrostatic interaction, which is the major source of the attraction in the ion pairs, is responsible for the directionality of the interactions and determining the magnitude of the interaction energy. Molecular dynamic simulations of the [dema][TFSA] and [dmpa][TFSA] ionic liquids show that the N–H bonds of the cations have contact with the negatively charged (oxygen and nitrogen) atoms of TFSA{sup −} anion, while the strong directionality of the interactions was not suggested from the simulation

  12. Ion bunch length effects on the beam-beam interaction and its compensation in a high-luminosity ring-ring electron-ion collider

    Energy Technology Data Exchange (ETDEWEB)

    Montag C.; Oeftiger, A.; Fischer, W.

    2012-05-20

    One of the luminosity limits in a ring-ring electron-ion collider is the beam-beam effect on the electrons. In the limit of short ion bunches, simulation studies have shown that this limit can be significantly increased by head-on beam-beam compensation with an electron lens. However, with an ion bunch length comparable to the beta-function at the IP in conjunction with a large beam-beam parameter, the electrons perform a sizeable fraction of a betatron oscillation period inside the long ion bunches. We present recent simulation results on the compensation of this beam-beam interaction with multiple electron lenses.

  13. On resonant interactions of ions with plasma waves in a reduced quasi-linear theory

    Directory of Open Access Journals (Sweden)

    E. Marsch

    2002-01-01

    Full Text Available Based on quasi-linear theory (involving pitch angle scattering, the resonant interactions between ions and waves in an anisotropic multi-component plasma are discussed. In particular, electromagnetic Alfvén and ion-cyclotron waves propagating along or obliquely to the magnetic field are considered. A set of reduced (with respect to the perpendicular velocity component quasi-linear diffusion equations is derived, involving reduced 1-D velocity distribution functions (VDFs, as they occur in wave dispersion relations. A 2-D model VDF can be constructed when using the Gaussian approximation. Wave-particle heating and acceleration rates are calculated.

  14. Solute partitioning in aqueous surfactant assemblies: comparison of hydrophobic-hydrophilic interactions in micelles, alcohol-swollen micelles, microemulsions, and synthetic vesicles

    Energy Technology Data Exchange (ETDEWEB)

    Russell, J.C.; Whitten, D.G.

    1982-11-03

    The structures of anionic assemblies including sodium lauryl sulfate (SLS) micelles, alcohol-swollen SLS micelles, microemulsions, and vesicles of a mixture of dipalmitoyllecithin and dicetyl phosphate are investigated by using the ground-state complexation of a hydrophilic quencher (methyl viologen) with several hydrophobic fluorescent probes, including surfactant stilbenes and 1,4-diphenylbutadiene. In SLS micelles this complexation can be decreased nearly an order of magnitude by addition of 1-heptanol, indicating that the structure of the micelle can be adjusted from the highly open structure of the pure micelle to a much more closed structure in which hydrophobic solubilizates can be sequestered from hydrophilic reagents bound to the surface. The fluorescence quenching process in anionic vesicles is strongly dependent on temperature; at low temperatures quenching occurs, while at higher temperatures addition of methyl viologen appears to increase the stilbene fluorescence, indicating that the dicationic quencher binds to the vesicle surface, increasing the order of the system. These results indicate that the degree of organization of surfactant systems can be adjusted by simple changes in composition. 33 references.

  15. STIM1 activates CRAC channels through rotation of the pore helix to open a hydrophobic gate

    Science.gov (United States)

    Yamashita, Megumi; Yeung, Priscilla S.-W.; Ing, Christopher E.; McNally, Beth A.; Pomès, Régis; Prakriya, Murali

    2017-02-01

    Store-operated Ca2+ release-activated Ca2+ (CRAC) channels constitute a major pathway for Ca2+ influx and mediate many essential signalling functions in animal cells, yet how they open remains elusive. Here, we investigate the gating mechanism of the human CRAC channel Orai1 by its activator, stromal interacting molecule 1 (STIM1). We find that two rings of pore-lining residues, V102 and F99, work together to form a hydrophobic gate. Mutations of these residues to polar amino acids produce channels with leaky gates that conduct ions in the resting state. STIM1-mediated channel activation occurs through rotation of the pore helix, which displaces the F99 residues away from the pore axis to increase pore hydration, allowing ions to flow through the V102-F99 hydrophobic band. Pore helix rotation by STIM1 also explains the dynamic coupling between CRAC channel gating and ion selectivity. This hydrophobic gating mechanism has implications for CRAC channel function, pharmacology and disease-causing mutations.

  16. Ion dynamics in electron beam–plasma interaction: particle-in-cell simulations

    Directory of Open Access Journals (Sweden)

    K. Baumgärtel

    2014-08-01

    Full Text Available Electron beam–plasma interaction including ions is studied by particle-in-cell (PIC simulations using a one-dimensional, electrostatic code. Evidence for Langmuir wave decay is given for sufficiently energetic beams, as in previous Vlasov–Maxwell simulations. The mechanism for the generation of localized finite-amplitude ion density fluctuations is analyzed. Amplitude modulation due to interference between the beam-generated Langmuir waves causes random wave localization including strong transient spikes in field intensity which create bursty ion density structures via ponderomotive forces. More dense beams may quench the decay instability and generate low-frequency variations dominated by the wave number of the fastest growing Langmuir mode.

  17. Investigation of ion acceleration mechanism through laser-matter interaction in femtosecond domain

    Energy Technology Data Exchange (ETDEWEB)

    Altana, C., E-mail: altana@lns.infn.it [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, Via S. Sofia 62, 95123 Catania (Italy); Dipartimento di Fisica e Astronomia, Università degli Studi di Catania, Via S. Sofia 64, 95123 Catania (Italy); Muoio, A. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, Via S. Sofia 62, 95123 Catania (Italy); Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Messina, Viale F.S. D’Alcontres 31, 98166 Messina (Italy); Lanzalone, G. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, Via S. Sofia 62, 95123 Catania (Italy); Università degli Studi di Enna “Kore”, Via delle Olimpiadi, 94100 Enna (Italy); Tudisco, S. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, Via S. Sofia 62, 95123 Catania (Italy); Brandi, F. [CNR, Intense Laser Irradiation Laboratory, Via G. Moruzzi 1, 56124 Pisa (Italy); Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova (Italy); Cirrone, G.A.P. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, Via S. Sofia 62, 95123 Catania (Italy); Cristoforetti, G. [CNR, Intense Laser Irradiation Laboratory, Via G. Moruzzi 1, 56124 Pisa (Italy); Fazzi, A. [Energy Department, Polytechnic of Milan and INFN, Milan (Italy); Ferrara, P.; Fulgentini, L. [CNR, Intense Laser Irradiation Laboratory, Via G. Moruzzi 1, 56124 Pisa (Italy); Giove, D. [Energy Department, Polytechnic of Milan and INFN, Milan (Italy); Koester, P. [CNR, Intense Laser Irradiation Laboratory, Via G. Moruzzi 1, 56124 Pisa (Italy); Labate, L. [CNR, Intense Laser Irradiation Laboratory, Via G. Moruzzi 1, 56124 Pisa (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, Largo B. Pontecorvo 3, 56127 Pisa (Italy); and others

    2016-09-01

    An experimental campaign aiming to investigate the ion acceleration mechanisms through laser-matter interaction in the femtosecond domain has been carried out at the ILIL facility at a laser intensity of up to 2×10{sup 19} W/cm{sup 2}. A Thomson Parabola Spectrometer was used to identify different ion species and measure the energy spectra and the corresponding temperature parameters. We discuss the dependence of the protons spectra upon the structural characteristics of the targets (thickness and atomic mass) and the role of surface versus target bulk during acceleration process. - Highlights: • Ion acceleration mechanism in TNSA regime was investigated. • The energy spectra and the corresponding temperature parameters were measured. • Dependence of the spectra upon the target structural characteristics was discussed.

  18. Ioninteractions in ligand design for anions and main group cations.

    Science.gov (United States)

    Watt, Michelle M; Collins, Mary S; Johnson, Darren W

    2013-04-16

    Interactions between ions and aromatic rings are now a mainstay in the field of supramolecular chemistry. The prototypical cation-π interaction, first characterized in the gas phase, is now well-known as an important contributor to protein structure and enzyme function and as a noncovalent force found in many synthetic systems. The complementary "anion-π interaction"-defined as an electrostatic attraction between an anion positioned over the centroid of an aromatic ring-has recently emerged as another reversible ioninteraction in supramolecular systems. This type of interaction could offer new selectivity in binding poorly basic, strongly solvated anions and may also affect structure, biological function, and anion transport. This Account describes our group's efforts in ioninteractions in two areas. We first describe a series of self-assembled Group 15 (pnictogen)-thiolate complexes, all featuring prominent cation-π interactions between the trivalent pnictogen and an aromatic ring of the ligand. This structural feature appears to stabilize a variety of self-assembled dinuclear macrocycles, dinuclear M2L3 cryptand-analogues, and a tetranuclear As4L2 metallocyclophane. These complexes are all remarkably robust and feature intramolecular cation-π interactions, which suggest that these interactions could be an important feature in ligand design for the Group 15 elements. We also highlight our efforts to characterize the interaction between anions and electron-deficient aromatic rings in solution. Complementary crystallographic and computational studies suggest that off-center weak-σ interactions play the dominant role in stabilizing the anion-arene adducts unless an acidic CH bond is present to participate in favorable CH···anion hydrogen bonds. In solution the weak-σ complexes show downfield shifts of the proton resonances in their NMR spectra. With more polarizable anions such as bromide and iodide, we also observe anion binding by UV

  19. Controlling interlayer interactions in vanadium pentoxide-poly(ethylene oxide) nanocomposites for enhanced magnesium-ion charge transport and storage

    Science.gov (United States)

    Perera, Sanjaya D.; Archer, Randall B.; Damin, Craig A.; Mendoza-Cruz, Rubén; Rhodes, Christopher P.

    2017-03-01

    Rechargeable magnesium batteries provide the potential for lower cost and improved safety compared with lithium-ion batteries, however obtaining cathode materials with highly reversible Mg-ion capacities is hindered by the high polarizability of divalent Mg-ions and slow solid-state Mg-ion diffusion. We report that incorporating poly(ethylene oxide) (PEO) between the layers of hydrated vanadium pentoxide (V2O5) xerogels results in significantly improved reversible Mg-ion capacities. X-ray diffraction and high resolution transmission electron microscopy show that the interlayer spacing between V2O5 layers was increased by PEO incorporation. Vibrational spectroscopy supports that the polymer interacts with the V2O5 lattice. The V2O5-PEO nanocomposite exhibited a 5-fold enhancement in Mg-ion capacity, improved stability, and improved rate capabilities compared with V2O5 xerogels. The Mg-ion diffusion coefficient of the nanocomposite was increased compared with that of V2O5 xerogels which is attributed to enhanced Mg-ion mobility due to the shielding interaction of PEO with the V2O5 lattice. This study shows that beyond only interlayer spacing, the nature of interlayer interactions of Mg-ions with V2O5, PEO, and H2O are key factors that affect Mg-ion charge transport and storage in layered materials. The design of layered materials with controlled interlayer interactions provides a new approach to develop improved cathodes for magnesium batteries.

  20. DFT study of the interaction between DOTA chelator and competitive alkali metal ions.

    Science.gov (United States)

    Frimpong, E; Skelton, A A; Honarparvar, B

    2017-09-01

    1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetracetic acid (DOTA) is an important chelator for radiolabeling of pharmaceuticals. The ability of alkali metals found in the body to complex with DOTA and compete with radio metal ions can alter the radiolabeling process. Non-covalent interactions between DOTA complexed with alkali metals Li + , Na + , K + and Rb + , are investigated with density functional theory using B3LYP and ωB97XD functionals. Conformational possibilities of DOTA were explored with a varying number of carboxylic pendant arms of DOTA in close proximity to the ions. It is found that the case in which four arms of DOTA are interacting with ions is more stable than other conformations. The objective of this study is to explore the electronic structure properties upon complexation of alkali metals Li + Na + , K + and Rb + with a DOTA chelator. Interaction energies, relaxation energies, entropies, Gibbs free energies and enthalpies show that the stability of DOTA, complexed with alkali metals decreases down the group of the periodic table. Implicit water solvation affects the complexation of DOTA-ions leading to decreases in the stability of the complexes. NBO analysis through the natural population charges and the second order perturbation theory, revealed a charge transfer between DOTA and alkali metals. Conceptual DFT-based properties such as HOMO/LUMO energies, ΔE HOMO-LUMO and chemical hardness and softness indicated a decrease in the chemical stability of DOTA-alkali metal complexes down the alkali metal series. This study serves as a guide to researchers in the field of organometallic chelators, particularly, radiopharmaceuticals in finding the efficient optimal match between chelators and various metal ions. Copyright © 2017 Elsevier Inc. All rights reserved.

  1. Non-Native Metal Ion Reveals the Role of Electrostatics in Synaptotagmin 1-Membrane Interactions.

    Science.gov (United States)

    Katti, Sachin; Nyenhuis, Sarah B; Her, Bin; Srivastava, Atul K; Taylor, Alexander B; Hart, P John; Cafiso, David S; Igumenova, Tatyana I

    2017-06-27

    C2 domains are independently folded modules that often target their host proteins to anionic membranes in a Ca2+-dependent manner. In these cases, membrane association is triggered by Ca2+ binding to the negatively charged loop region of the C2 domain. Here, we used a non-native metal ion, Cd2+, in lieu of Ca2+ to gain insight into the contributions made by long-range Coulombic interactions and direct metal ion-lipid bridging to membrane binding. Using X-ray crystallography, NMR, Förster resonance energy transfer, and vesicle cosedimentation assays, we demonstrate that, although Cd2+ binds to the loop region of C2A/B domains of synaptotagmin 1 with high affinity, long-range Coulombic interactions are too weak to support membrane binding of individual domains. We attribute this behavior to two factors: the stoichiometry of Cd2+ binding to the loop regions of the C2A and C2B domains and the impaired ability of Cd2+ to directly coordinate the lipids. In contrast, electron paramagnetic resonance experiments revealed that Cd2+ does support membrane binding of the C2 domains in full-length synaptotagmin 1, where the high local lipid concentrations that result from membrane tethering can partially compensate for lack of a full complement of divalent metal ions and specific lipid coordination in Cd2+-complexed C2A/B domains. Our data suggest that long-range Coulombic interactions alone can drive the initial association of C2A/B with anionic membranes and that Ca2+ further augments membrane binding by the formation of metal ion-lipid coordination bonds and additional Ca2+ ion binding to the C2 domain loop regions.

  2. Effects of the Surface Morphology and Conformations of Lignocellulosic Biomass Biopolymers on Their Nanoscale Interactions with Hydrophobic Self-Assembled Monolayers.

    Science.gov (United States)

    Arslan, Baran; Egerton, Kirstin; Zhang, Xiao; Abu-Lail, Nehal I

    2017-07-11

    The effects of the morphology and conformations of the surface biopolymers present on lignocellulosic biomass as well as their steric hindrance on enzymatic adsorption to biomass surfaces remain elusive. In a step to better understand these effects, nanoscale steric forces between a model surface that represents the hydrophobic residues of a cellulase enzyme and a set of reference lignocellulosic substrates were measured using atomic force microscopy (AFM) in liquid media. The reference substrates investigated were prepared by kraft, sulfite, and organosolv pulping pretreatment methods and varied in their surface lignin, xylan, and acetone extractives' contents. Measured steric forces were quantified through fitting to a model developed to describe polyelectrolytes brushes in terms of a brush thickness and a brush grafting density. Our data indicated that cellulose microfibrils extend from the microfibril matrix leading to a long-range steric repulsion and low attractive forces to the hydrophobic model of the enzyme, suggesting that steric hindering can be a possible mechanism for nonproductive binding of enzymes to cellulose. When the amount of xylan increased in the absence of lignin, steric repulsions between the hydrophobic model of the enzyme, and biomass biopolymers decreased as a result of collapsed cellulose microfibrils and adhesion forces increased. This suggests that leaving a small amount of xylan after biomass pretreatment can help improve enzymatic binding to cellulose. Irrespective of the type of lignin present on biomass, grafting densities increased and brush thicknesses decreased compared to those of lignin-free substrates. When compared to lignin-free substrates, lignin-containing substrates had higher attractive forces and lower steric repulsive forces. In addition, AFM images of the reference substrates in the wet and dry states showed that lignin precipitates on the biomass surface where kraft lignin had the highest particle size leading to a

  3. Ion Acceleration by Laser Plasma Interaction from Cryogenic Micro Jets - Oral Presentation

    Energy Technology Data Exchange (ETDEWEB)

    Propp, Adrienne [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-08-25

    Processes that occur in extreme conditions, such as in the center of stars and large planets, can be simulated in the laboratory using facilities such as SLAC National Accelerator Laboratory and the Jupiter Laser Facility (JLF) at Lawrence Livermore National Laboratory (LLNL). These facilities allow scientists to investigate the properties of matter by observing their interactions with high power lasers. Ion acceleration from laser plasma interaction is gaining greater attention today due to its widespread potential applications, including proton beam cancer therapy and fast ignition for energy production. Typically, ion acceleration is achieved by focusing a high power laser on thin foil targets through a mechanism called Target Normal Sheath Acceleration. Based on research and recent experiments, we hypothesized that a pure liquid cryogenic jet would be an ideal target for this type of interaction, capable of producing the highest proton energies possible with today’s laser technologies. Furthermore, it would provide a continuous, pure target, unlike metal foils which are consumed in the interaction and easily contaminated. In an effort to test this hypothesis and investigate new, potentially more efficient mechanisms of ion acceleration, we used the 527 nm split beam, frequency-doubled TITAN laser at JLF. Data from the cryogenic jets was limited due to the flow of current up the jet into the nozzle during the interaction, heating the jet and damaging the orifice. However, we acheived a pure proton beam with an indiciation of a monoenergetic feature. Furthermore, data from gold and carbon wires showed surprising and interesting results. Preliminary analysis of data from two ion emission diagnostics, Thomson parabola spectrometers (TPs) and radio chromic films (RCFs), suggests that shockwave acceleration occurred rather than target normal sheath acceleration, the standard mechanism of ion acceleration. Upon completion of the experiment at TITAN, I researched the

  4. Emission of low-energy electrons from multicharged ions interacting with metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Zeijlmans van Emmichoven, P.A. (Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6372 (United States) Joint Institute for Heavy Ion Research, Holifield Heavy Ion Research Facility, Oak Ridge, Tennessee 37831-6374 (United States)); Havener, C.C. (Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6372 (United States)); Hughes, I.G. (Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6372 (United States) Joint Institute for Heavy Ion Research, Holifield Heavy Ion Research Facility, Oak Ridge, Tennessee 37831-6374 (United States)); Zehner, D.M.; Meyer, F.W. (Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6372 (United States))

    1993-05-01

    Low-energy electron spectra are reported for 60- and 100-keV multicharged ions interacting at an incident angle of 20[degree] with Au and Cu surfaces. Analysis of the spectra indicate that at least two features contribute. The first feature represents the major contribution to the total electron yield and consists of 5--10-eV electrons emitted over a wide range of angles. The angular distribution of this component is not symmetric with respect to the surface normal, but shows an increase in the forward direction of the incident ions. It will be shown that this component arises predominantly from below the surface. Possible potential-emission mechanisms which may contribute will be discussed. The second feature, which constitutes a minor part of the overall electron emission, occurs at higher electron energies ([similar to]20 eV), and is peaked at the extreme forward angles. Binary encounters between incident ions and metal electrons at the surface-vacuum interface will be shown to describe the main features of this component. At even higher electron energies ([gt]40 eV) the spectra show a tail whose slope does not depend on either the initial charge state or kinetic energy of the incident ions. The invariance with kinetic energy is in sharp contrast with the corresponding experimental results from ion-atom collisions.

  5. Interaction of low-energy highly charged ions with matter; Wechselwirkung niederenergetischer hochgeladener Ionen mit Materie

    Energy Technology Data Exchange (ETDEWEB)

    Ginzel, Rainer

    2010-06-09

    The thesis presented herein deals with experimental studies of the interaction between highly charged ions and neutral matter at low collision energies. The energy range investigated is of great interest for the understanding of both charge exchange reactions between ions comprising the solar wind and various astrophysical gases, as well as the creation of near-surface nanostructures. Over the course of this thesis an experimental setup was constructed, capable of reducing the kinetic energy of incoming ions by two orders of magnitude and finally focussing the decelerated ion beam onto a solid or gaseous target. A coincidence method was employed for the simultaneous detection of photons emitted during the charge exchange process together with the corresponding projectile ions. In this manner, it was possible to separate reaction channels, whose superposition presumably propagated large uncertainties and systematic errors in previous measurements. This work has unveiled unexpectedly strong contributions of slow radiative decay channels and clear evidence of previously only postulated decay processes in charge exchange-induced X-ray spectra. (orig.)

  6. Conditions for Debris-Background Ion Interactions and Collisionless Shock Wave Generation

    Energy Technology Data Exchange (ETDEWEB)

    Winske, Dan [Los Alamos National Laboratory; Cowee, Misa [Los Alamos National Laboratory

    2012-07-10

    We use hybrid simulations and simple theoretical arguments to determine when debris ions streaming relative to background ions in a collisionless, magnetized plasma couple strongly enough to generate a magnetosonic shock wave. We consider three types of configurations: one-dimensional, the two-dimensional extension of the 1-D case, and a more complex 2-D geometry that contains some effects that would be found in a laser-produced, laboratory plasma. We show that the simulation results as well as previous Russian and LLNL results reduce to a simple condition (R{sub m}/{rho}{sub d} = equal mass radius/debris ion gyroradius {ge} 0.7) for the generation of a shock wave. Strong debris interaction with the background is characterized by the formation of a magnetic pulse that steepens and speeds up as it encounters the debris ions deflected by the magnetic field. The pulse further evolves into a shock. As the earlier work has indicated, the process also involves the generation of a transverse electric field perpendicular to the flow and the magnetic field that accelerates the background ions radially outward, which in turn causes the speedup of the pulse. With electric and magnetic field probes, the UCLA laser experiments should be able to detect these signatures of coupling as well as the generation of the shock wave.

  7. Coulombic interactions during advection-dominated transport of ions in porous media

    DEFF Research Database (Denmark)

    Muniruzzaman, Muhammad; Stolze, Lucien; Rolle, Massimo

    2017-01-01

    Solute transport of charged species in porous media is significantly affected by the electrochemical migration term resulting from the charge-induced interactions among dissolved ions and with solid surfaces. Therefore, the characterization of such Coulombic interactions and their effect...... on multicomponent ionic transport is of critical importance for assessing the fate of charged solutes in porous media. In this work we present a detailed investigation of the electrochemical effects during conservative multicomponent ionic transport in homogeneous and heterogeneous domains by means of laboratory...... focus our attention on transient transport and pulse injection of the electrolytes. In these experiments high-resolution spatial and temporal monitoring of the ions' concentrations (600 samples; 1800 concentration measurements), at closely spaced outlet ports (5 mm), allowed us resolving the effects...

  8. Two-Photon Interactions with Nuclear Breakup in Relativistic Heavy Ion Collisions

    Energy Technology Data Exchange (ETDEWEB)

    Baltz, Anthony J.; Gorbunov, Yuri; R Klein, Spencer; Nystrand, Joakim

    2010-07-07

    Highly charged relativistic heavy ions have high cross-sections for two-photon interactions. The photon flux is high enough that two-photon interactions may be accompanied by additional photonuclear interactions. Except for the shared impact parameter, these interactions are independent. Additional interactions like mutual Coulomb excitation are of experimental interest, since the neutrons from the nuclear dissociation provide a simple, relatively unbiased trigger. We calculate the cross sections, rapidity, mass and transverse momentum (p{sub T}) distributions for exclusive {gamma}{gamma} production of mesons and lepton pairs, and for {gamma}{gamma} reactions accompanied by mutual Coulomb dissociation. The cross-sections for {gamma}{gamma} interactions accompanied by multiple neutron emission (XnXn) and single neutron emission (1n1n) are about 1/10 and 1/100 of that for the unaccompanied {gamma}{gamma} interactions. We discuss the accuracy with which these cross-sections may be calculated. The typical p{sub T} of {gamma}{gamma} final states is several times smaller than for comparable coherent photonuclear interactions, so p{sub T} may be an effective tool for separating the two classes of interactions.

  9. Final Report - Assessment of Potential Phosphate Ion-Cementitious Materials Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Naus, Dan J [ORNL; Mattus, Catherine H [ORNL; Dole, Leslie Robert [ORNL

    2007-06-01

    The objectives of this limited study were to: (1) review the potential for degradation of cementitious materials due to exposure to high concentrations of phosphate ions; (2) provide an improved understanding of any significant factors that may lead to a requirement to establish exposure limits for concrete structures exposed to soils or ground waters containing high levels of phosphate ions; (3) recommend, as appropriate, whether a limitation on phosphate ion concentration in soils or ground water is required to avoid degradation of concrete structures; and (4) provide a "primer" on factors that can affect the durability of concrete materials and structures in nuclear power plants. An assessment of the potential effects of phosphate ions on cementitious materials was made through a review of the literature, contacts with concrete research personnel, and conduct of a "bench-scale" laboratory investigation. Results of these activities indicate that: no harmful interactions occur between phosphates and cementitious materials unless phosphates are present in the form of phosphoric acid; phosphates have been incorporated into concrete as set retarders, and phosphate cements have been used for infrastructure repair; no standards or guidelines exist pertaining to applications of reinforced concrete structures in high-phosphate environments; interactions of phosphate ions and cementitious materials has not been a concern of the research community; and laboratory results indicate similar performance of specimens cured in phosphate solutions and those cured in a calcium hydroxide solution after exposure periods of up to eighteen months. Relative to the "primer," a separate NUREG report has been prepared that provides a review of pertinent factors that can affect the durability of nuclear power plant reinforced concrete structures.

  10. Ion-Beam-Induced Defects and Defect Interactions in Perovskite-Structure Titanates

    Energy Technology Data Exchange (ETDEWEB)

    Boatner, L.A.; Jiang, W.; Meldrum, A.; Thevuthasan, S.; Weber, W.J.; Williford, R.E.

    1999-08-23

    Ion-beam irradiation of perovskite structures results in the production and accumulation of defects. Below a critical temperature, irradiation also leads to a crystalline-to-amorphous transformation. The critical temperature for amorphization under 800 keV Kr{sup +} ion irradiation is 425,440 and 550 K for SrTiO{sub 3}, CaTiO{sub 3} and BaTiO{sub 3}, respectively. The results of ion-channeling studies on SrTiO{sub 3} irradiated with 1.0 MeV Au{sup 2+} ions suggest that the crystalline-to-amorphous transformation is dominated by the accumulation and interaction of irradiation-induced defects. In SiTiO{sub 3} irradiated with He{sup +} and 0{sup +} ions at 180 K, isochronal annealing studies indicate that there is significant recovery of defects on both the oxygen and cation sublattices between 200 and 400 K. These results suggest that defect recovery processes may control the kinetics of amorphization. A fit of the direct-impact/defect-stimulated model to the data for SrTiO{sub 3} suggests that the kinetics of amorphization are controlled by both a nearly athermal irradiation-assisted recovery process with an activation energy of 0.1 plus or minus 0.05 eV and a thermal defect recovery process with an activation energy of 0.6 plus or minus 0.1 eV. In SrTi0{sub 3} implanted with 40 keV H{sup +} to 5.0 x 10{sup 16} and 1.0 x 10{sup 17} ions/cm{sup 2}, annealing at 470 K increases the backscattering yield from Sr and Ti and is mostly likely due to the coalescence of H{sub 2} into bubble nuclei. Annealing at 570 K and higher results in the formation of blisters or large cleaved areas.

  11. Protein-induced bilayer Perturbations: Lipid ordering and hydrophobic coupling

    DEFF Research Database (Denmark)

    Petersen, Frederic Nicolas Rønne; Laursen, Ib; Bohr, Henrik

    2009-01-01

    The host lipid bilayer is increasingly being recognized as an important non-specific regulator of membrane protein function. Despite considerable progress the interplay between hydrophobic coupling and lipid ordering is still elusive. We use electron spin resonance (ESR) to study the interaction...... and hydrophobic mismatch. Our findings also show that at high protein:lipid ratios the lipids are motionally restricted but not completely immobilized. Both exchange on and off rate values for the lipid ↔ gramicidin interaction are lowest at optimal hydrophobic matching. Hydrophobic mismatch of few Å results...... in up to 10-fold increased exchange rates as compared to the ‘optimal’ match situation pointing to the regulatory role of hydrophobic coupling in lipid–protein interactions....

  12. Motion of the plasma critical layer during relativistic-electron laser interaction with immobile and comoving ion plasma for ion accelerationa)

    OpenAIRE

    Sahai, AA

    2014-01-01

    We analyze the motion of the plasma critical layer by two different processes in the relativistic-electron laser-plasma interaction regime ($a_0>1$). The differences are highlighted when the critical layer ions are stationary in contrast to when they move with it. Controlling the speed of the plasma critical layer in this regime is essential for creating low-$\\beta$ traveling acceleration structures of sufficient laser-excited potential for laser ion accelerators (LIA). In Relativistically In...

  13. Interaction between alpha-synuclein and metal ions, still looking for a role in the pathogenesis of Parkinson's disease.

    Science.gov (United States)

    Bisaglia, Marco; Tessari, Isabella; Mammi, Stefano; Bubacco, Luigi

    2009-01-01

    The most recent literature on the interaction between alpha-synuclein in its several aggregation states and metal ions is discussed. This analysis shows two major types of interactions. Binding sites are present in the C-terminal region, and similar, low affinity (in the millimolar range) is exhibited toward many different metal ions, including copper and iron. A more complex scenario emerges for these latter metal ions, which are also able to coordinate with high affinity (in the micromolar range) to the N-terminal region of alpha-synuclein. Moreover, these redox-active metal ions may induce chemical modifications on the protein in vitro and in the reducing intracellular environment, and these modifications might be relevant for the aggregation properties of alpha-synuclein. Finally, an attempt is made to contextualize the interaction between alpha-synuclein and these metal ions in the framework of the elusive and multifactorial pathogenesis of Parkinson's disease.

  14. Phactr3/scapinin, a member of protein phosphatase 1 and actin regulator (phactr family, interacts with the plasma membrane via basic and hydrophobic residues in the N-terminus.

    Directory of Open Access Journals (Sweden)

    Akihiro Itoh

    Full Text Available Proteins that belong to the protein phosphatase 1 and actin regulator (phactr family are involved in cell motility and morphogenesis. However, the mechanisms that regulate the actin cytoskeleton are poorly understood. We have previously shown that phactr3, also known as scapinin, localizes to the plasma membrane, including lamellipodia and membrane ruffles. In the present study, experiments using deletion and point mutants showed that the basic and hydrophobic residues in the N-terminus play crucial roles in the localization to the plasma membrane. A BH analysis (http://helixweb.nih.gov/bhsearch is a program developed to identify membrane-binding domains that comprise basic and hydrophobic residues in membrane proteins. We applied this program to phactr3. The results of the BH plot analysis agreed with the experimentally determined region that is responsible for the localization of phactr3 to the plasma membrane. In vitro experiments showed that the N-terminal itself binds to liposomes and acidic phospholipids. In addition, we showed that the interaction with the plasma membrane via the N-terminal membrane-binding sequence is required for phactr3-induced morphological changes in Cos7 cells. The membrane-binding sequence in the N-terminus is highly conserved in all members of the phactr family. Our findings may provide a molecular basis for understanding the mechanisms that allow phactr proteins to regulate cell morphogenesis.

  15. Interaction between fast ions and ion cyclotron heating in a tokamak plasma; Interaction des ions rapides avec les ondes a la frequence cyclotronique ionique dans un plasma de tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Bergeaud, V

    2001-11-01

    In an ignited fusion reactor, the plasma temperature is sustained by the fusion reactions. However, before this regime is reached, it is necessary to bring an additional power to the plasma. One of the methods that enables the coupling of power is the use of an electromagnetic wave in the ion cyclotron range of frequencies (ICRF). This thesis deals with the interaction between ICRF heating and the fast ions. The thesis contains a theoretical study of the influence of ICRF heating on the ion distribution function. A particular emphasis is put on the importance of the toroidal spectrum of the modes of propagation of the wave in the tokamak. It is necessary to take into account all these modes in order to correctly assess the strength of the wave particle interaction, especially for high energy particles (of the order of hundreds of keV). The classical treatment of the wave particle interaction is based on the hypothesis that the cyclotron phase of the particle and the wave phase are de-correlated between successive resonant interactions. One is therefore led to consider ICRF heating as a diffusive process. This hypothesis is reconsidered in this thesis and it is shown that strong correlations exist in a large part of the velocity space. For this study, a numerical code that computes the full trajectory of particles interacting with a complete electromagnetic field has been developed. The thesis also deals with the problem of fast ion losses due to the breaking of the toroidal symmetry of the confinement magnetic field (called the ripple modulation). Between two toroidal coils, local magnetic wells exist, and particles can be trapped there. When trapped they undergo a vertical drift that makes them quit the plasma rapidly. The ripple modulation also causes an enhancement of the radial diffusion, thereby increasing the losses. A Monte Carlo model describing these mechanisms is presented. This model is validated thanks to a comparison with an experimental database from

  16. Interaction of fast ions with ion cyclotron electromagnetic waves in tokamak plasma; Interaction des ions rapides avec les ondes a la frequence cyclotronique ionique dans un plasma de tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Bergeaud, V

    2000-12-01

    In an ignited fusion reactor, the plasma temperature is sustained by the fusion reactions. However, before this regime is reached, it is necessary to bring an additional power to the plasma. One of the methods that enables the coupling of power is the use of an electromagnetic wave in the ion cyclotron range of frequencies (ICRF). This thesis deals with the interaction between ICRF heating and the fast ions. The thesis contains a theoretical study of the influence of ICRF heating on the ion distribution function. A particular emphasis is put on the importance of the toroidal spectrum of the modes of propagation of the wave in the tokamak. It is necessary to take into account all these modes in order to correctly assess the strength of the wave particle interaction, especially for high energy particles (of the order of hundreds of keV). The classical treatment of the wave particle interaction is based on the hypothesis that the cyclotron phase of the particle and the wave phase are de-correlated between successive resonant interactions. One is therefore led to consider ICRF heating as a diffusive process. This hypothesis is reconsidered in this thesis and it is shown that strong correlations exist in a large part of the velocity space. For this study, a numerical code that computes the full trajectory of particles interacting with a complete electromagnetic field has been developed. The thesis also deals with the problem of fast ion losses due to the breaking of the toroidal symmetry of the confinement magnetic field (called the ripple modulation). Between two toroidal coils, local magnetic wells exist, and particles can be trapped there. When trapped they undergo a vertical drift that makes them quit the plasma rapidly. The ripple modulation also causes an enhancement of the radial diffusion, thereby increasing the losses. A Monte Carlo model describing these mechanisms is presented. This model is validated thanks to a comparison with an experimental database from

  17. Measurement of the magnetic interaction between two bound electrons of two separate ions.

    Science.gov (United States)

    Kotler, Shlomi; Akerman, Nitzan; Navon, Nir; Glickman, Yinnon; Ozeri, Roee

    2014-06-19

    Electrons have an intrinsic, indivisible, magnetic dipole aligned with their internal angular momentum (spin). The magnetic interaction between two electronic spins can therefore impose a change in their orientation. Similar dipolar magnetic interactions exist between other spin systems and have been studied experimentally. Examples include the interaction between an electron and its nucleus and the interaction between several multi-electron spin complexes. The challenge in observing such interactions for two electrons is twofold. First, at the atomic scale, where the coupling is relatively large, it is often dominated by the much larger Coulomb exchange counterpart. Second, on scales that are substantially larger than the atomic, the magnetic coupling is very weak and can be well below the ambient magnetic noise. Here we report the measurement of the magnetic interaction between the two ground-state spin-1/2 valence electrons of two (88)Sr(+) ions, co-trapped in an electric Paul trap. We varied the ion separation, d, between 2.18 and 2.76 micrometres and measured the electrons' weak, millihertz-scale, magnetic interaction as a function of distance, in the presence of magnetic noise that was six orders of magnitude larger than the magnetic fields the electrons apply on each other. The cooperative spin dynamics was kept coherent for 15 seconds, during which spin entanglement was generated, as verified by a negative measured value of -0.16 for the swap entanglement witness. The sensitivity necessary for this measurement was provided by restricting the spin evolution to a decoherence-free subspace that is immune to collective magnetic field noise. Our measurements show a d(-3.0(4)) distance dependence for the coupling, consistent with the inverse-cube law.

  18. Insights into the Hendra virus NTAIL-XD complex: Evidence for a parallel organization of the helical MoRE at the XD surface stabilized by a combination of hydrophobic and polar interactions.

    Science.gov (United States)

    Erales, Jenny; Beltrandi, Matilde; Roche, Jennifer; Maté, Maria; Longhi, Sonia

    2015-08-01

    The Hendra virus is a member of the Henipavirus genus within the Paramyxoviridae family. The nucleoprotein, which consists of a structured core and of a C-terminal intrinsically disordered domain (N(TAIL)), encapsidates the viral genome within a helical nucleocapsid. N(TAIL) partly protrudes from the surface of the nucleocapsid being thus capable of interacting with the C-terminal X domain (XD) of the viral phosphoprotein. Interaction with XD implies a molecular recognition element (MoRE) that is located within N(TAIL) residues 470-490, and that undergoes α-helical folding. The MoRE has been proposed to be embedded in the hydrophobic groove delimited by helices α2 and α3 of XD, although experimental data could not discriminate between a parallel and an antiparallel orientation of the MoRE. Previous studies also showed that if the binding interface is enriched in hydrophobic residues, charged residues located close to the interface might play a role in complex formation. Here, we targeted for site directed mutagenesis two acidic and two basic residues within XD and N(TAIL). ITC studies showed that electrostatics plays a crucial role in complex formation and pointed a parallel orientation of the MoRE as more likely. Further support for a parallel orientation was afforded by SAXS studies that made use of two chimeric constructs in which XD and the MoRE were covalently linked to each other. Altogether, these studies unveiled the multiparametric nature of the interactions established within this complex and contribute to shed light onto the molecular features of protein interfaces involving intrinsically disordered regions. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Temperature dependence of the kinetics of the urea-induced dissociation of human plasma alpha 2-macroglobulin into half-molecules. A minimum rate at 15 degrees C indicates hydrophobic interaction between the subunits.

    Science.gov (United States)

    Sjöberg, B; Pap, S; Mortensen, K

    1992-05-20

    The kinetics of the urea-induced dissociation of human plasma alpha 2-macroglobulin to half-molecules has been studied as a function of temperature by using small-angle scattering of X-rays and neutrons. The most striking result of the present investigation is that there is a minimum in reaction rate at about 15 degrees C, and that the rate increases when the temperature is lowered, or raised, from that value. By analyzing the first-order rate constants in terms of transition-state theory it was found that the dissociation is associated with a large and positive change in heat capacity between the activated complex and native alpha 2-macroglobulin (delta CP is in the range 5 to 6 kJ mol-1 K-1). In analogy with pure thermodynamic investigations, where a large change in heat capacity normally is interpreted as a melting of hydrophobic interaction, we therefore propose that hydrophobic interaction is involved in the so-called non-covalent interactions between the subunits of alpha 2-macroglobulin. As a result of the present investigation, it also follows that the free energy of activation delta G has a maximum at about 32 degrees C, whereas the enthalpy of activation delta H and the entropy of activation delta S are zero at about 15 degrees C and 32 degrees C, respectively. These temperatures are slightly dependent upon the concentration of urea and upon whether the reaction is run in a 1H or a 2H medium. Furthermore, from the kinetic point of view, at low temperature the reaction can be characterized as enthalpy driven, whereas at high temperature, it can be characterized as entropy driven.

  20. Interaction of Fast Ions with Global Plasma Modes in the C-2 Field Reversed Configuration Experiment

    Science.gov (United States)

    Smirnov, Artem; Dettrick, Sean; Clary, Ryan; Korepanov, Sergey; Thompson, Matthew; Trask, Erik; Tuszewski, Michel

    2012-10-01

    A high-confinement operating regime [1] with plasma lifetimes significantly exceeding past empirical scaling laws was recently obtained by combining plasma gun edge biasing and tangential Neutral Beam Injection (NBI) in the C-2 field-reversed configuration (FRC) experiment [2, 3]. We present experimental and computational results on the interaction of fast ions with the n=2 rotational and n=1 wobble modes in the C-2 FRC. It is found that the n=2 mode is similar to quadrupole magnetic fields in its detrimental effect on the fast ion transport due to symmetry breaking. The plasma gun generates an inward radial electric field, thus stabilizing the n=2 rotational instability without applying the quadrupole magnetic fields. The resultant FRCs are nearly axisymmetric, which enables fast ion confinement. The NBI further suppresses the n=2 mode, improves the plasma confinement characteristics, and increases the plasma configuration lifetime [4]. The n=1 wobble mode has relatively little effect on the fast ion transport, likely due to the approximate axisymmetry about the displaced plasma column. [4pt] [1] M. Tuszewski et al., Phys. Rev. Lett. 108, 255008 (2012).[0pt] [2] M. Binderbauer et al., Phys. Rev. Lett. 105, 045003 (2010).[0pt] [3] H.Y. Guo et al., Phys. Plasmas 18, 056110 (2011).[0pt] [4] M. Tuszewski et al., Phys. Plasmas 19, 056108 (2012)

  1. Silkworm eggs: An ideal model for studying the biological effects of low energy Ar{sup +} ion interaction in animals

    Energy Technology Data Exchange (ETDEWEB)

    Ling Lin; Liu Xuelan [School of Life Sciences, Anhui Agricultural University, Hefei 230031 (China); Xu Jiaping, E-mail: jiapingxu@163.com [School of Life Sciences, Anhui Agricultural University, Hefei 230031 (China); You Zhengying; Zhou Jingbo [School of Life Sciences, Anhui Agricultural University, Hefei 230031 (China)

    2011-09-15

    Highlights: {yields} Low energy Ar{sup +} ion beam interactions with silkworm eggs. {yields} Ion beam bombardment as a novel method for gene transfer in silkworm. {yields} Provide evidence for studying the mechanisms of ion beam interaction in animals. - Abstract: The object of the current work was to study low energy Ar{sup +} ion beam interactions with silkworm eggs and thus provide further understanding of the mechanisms involved in ion bombardment-induced direct gene transfer into silkworm eggs. In this paper, using low-energy Ar{sup +} ion beam bombardment combined with piggyBac transposon, we developed a novel method to induce gene transfer in silkworm. Using bombardment conditions optimized for egg-incubation (25 keV with ion fluences of 800 x 2.6 x 10{sup 15} ions/cm{sup 2} in dry state under vacuum), vector pBac{l_brace}3 x P3-EGFPaf{r_brace} and helper plasmid pHA3pig were successfully transferred into the silkworm eggs. Our results obtained from by PCR assay and genomic Southern blotting analysis of the G1 generations provide evidence that low-energy ion beam can generate some craters that play a role in acting as pathways of exogenous DNA molecules into silkworm eggs.

  2. Structural interaction of novel dendrimer and subunits with water ...

    African Journals Online (AJOL)

    ... decrease with much disruption in molecular interaction similar to surfactant behavior. The lowest ΔGE values were with the 2,4,6-trichlorotriazine (TCT) due to comparatively higher interactions of the chloride ion. KEY WORDS: Excess viscosity, Trichlorotriazine, Hydrophilic, Hydrophobic, Hydrodynamic. Bull. Chem. Soc.

  3. A Comment on Interaction of Lower Hybrid Waves with the Current-Driven Ion-Acoustic Instability

    DEFF Research Database (Denmark)

    Schrittwieser, R.; Juul Rasmussen, Jens

    1985-01-01

    Majeski et al. (1984) have investigated the interaction between the current-driven 'ion-acoustic' instability and high frequency lower hybrid waves. The 'ion-acoustic' instability was excited by drawing an electron current through the plasma column of a single-ended Q-machine by means...

  4. Optical properties of voltage sensitive hemicyanine dyes of variable hydrophobicity confined within surfactant micelles

    Science.gov (United States)

    Naeem, Kashif; Naseem, Bushra; Shah, S. S.; Shah, Syed W. H.

    2017-11-01

    The optical properties of amphiphilic hemicyanine dyes with variable hydrophobicity, confined within anionic micelles of sodium dodecylbenzenesulfonate (NaDDBS) have been studied by UV–visible absorption spectroscopy. The confinement constant, K conf has been determined for each entrapped dye. The ion-pair formation between dye and surfactant causes a decline in electronic transition energy (ΔE T) when dye alkyl chains are smaller due to stabilization of both the ground and excited state. ΔE T values gradually increase with increase in dye hydrophobicity that hampers the electrostatic interaction with dialkylammonium moiety and consequently excited state stabilization is compromised. The average number of dye molecules trapped in a single micelle was also determined. The negative values of Gibbs free energy indicate that the dye entrapment within micelles is energetically favored. These findings have significance for developing functional materials with peculiar luminescent properties, especially for more effective probing of complex biological systems.

  5. Effects of the ion-solid interaction in glow discharge vapour deposition polymerization of pyromellitic dianhydride

    Energy Technology Data Exchange (ETDEWEB)

    Maggioni, G. E-mail: maggioni@inl.infn.it; Carturan, S.; Rigato, V.; Pieri, U

    2000-05-02

    Low energy He ion bombardment of pyromellitic dianhydride monomer used in glow discharge vapour deposition polymerization (GDVDP) of polyimide coatings and its effects on the film deposition process have been studied. The sublimation of the monomer molecules and the simultaneous formation of a damaged, carbon-rich surface layer on the target are discussed from a theoretical point of view based on simulations of the ion-solid interaction. Optical emission and mass spectrometry have been used to analyse the species emitted from the target. In order to study the time evolution of the PMDA target damage, the deposition rate of monomer molecules has been monitored. FT-IR spectroscopy has been used to determine the molecular damaging of the target monomer and deposited films.

  6. Transferred hyperfine interaction between the rare-earth ions and the fluorine nuclei in rare-earth trifluorides

    DEFF Research Database (Denmark)

    Hansen, P. E.; Nevald, Rolf; Guggenheim, H. G.

    1978-01-01

    The isotropic and anisotropic transferred hyperfine interactions between F ions in the two chemically inequivalent sites and the rare-earth ions (R) have been derived from 19F NMR measurements in the temperature region 100-300 K on single crystals of TbF3 and DyF3. The isotropic interactions are ...... to vary only slightly with temperature. They are further assigned to definite R's in the unit cell, which cannot be done from macroscopic magnetic measurements....

  7. Learning ion-solid interactions hands-on: An activity based, inquiry oriented, graduate course

    Energy Technology Data Exchange (ETDEWEB)

    Braunstein, Gabriel [Department of Physics, University of Central Florida, 4000 Central Florida Blvd., Orlando, FL 32816 (United States)]. E-mail: braunstein@physics.ucf.edu

    2005-12-15

    Experimental work, using state of the art instrumentation, is integrated with lectures in a 'real life', learning by discovery approach, in the Ion-Solid Interactions graduate/undergraduate course offered by the Department of Physics of University of Central Florida. The lecture component of the course covers the underlying physical principles, and related scientific and technological applications, associated with the interaction of energetic ions with matter. In the experimental section the students form small groups and perform a variety of projects, experimental and computational, as part of a participative, inquiry oriented, learning process. In the most recent offering of the class, the students deposited a compound semiconductor thin film by dual-gun sputtering deposition, where each group aimed at a different stoichiometry of the same compound (Zn{sub 1-x}S {sub x}O {sub y}). Then they analyzed the composition using Rutherford backscattering spectrometry, measured electrical transport properties using Hall effect and conductivity measurements, and determined the band gap using spectrophotometry. Finally the groups shared their results and each wrote a 'journal-like' technical article describing the entire work. In a different assignment, each group also developed a Monte Carlo computer program ('TRIM-like') to simulate the penetration of ions into a solid, in ion implantation, calculating the stopping cross-sections with approximate models, taught in class, which can be analytically solved. The combination of classroom/laboratory activities is very well received by the students. They gain real life experience operating state of the art equipment, and working in teams, while performing research-like projects, and simultaneously they learn the theoretical foundations of the discipline.

  8. Learning ion solid interactions hands-on: An activity based, inquiry oriented, graduate course

    Science.gov (United States)

    Braunstein, Gabriel

    2005-12-01

    Experimental work, using state of the art instrumentation, is integrated with lectures in a "real life", learning by discovery approach, in the Ion-Solid Interactions graduate/undergraduate course offered by the Department of Physics of the University of Central Florida. The lecture component of the course covers the underlying physical principles, and related scientific and technological applications, associated with the interaction of energetic ions with matter. In the experimental section the students form small groups and perform a variety of projects, experimental and computational, as part of a participative, inquiry oriented, learning process. In the most recent offering of the class, the students deposited a compound semiconductor thin film by dual-gun sputtering deposition, where each group aimed at a different stoichiometry of the same compound (Zn1-xSxOy). Then they analyzed the composition using Rutherford backscattering spectrometry, measured electrical transport properties using Hall effect and conductivity measurements, and determined the band gap using spectrophotometry. Finally the groups shared their results and each wrote a 'journal-like' technical article describing the entire work. In a different assignment, each group also developed a Monte Carlo computer program ('TRIM-like') to simulate the penetration of ions into a solid, in ion implantation, calculating the stopping cross-sections with approximate models, taught in class, which can be analytically solved. The combination of classroom/laboratory activities is very well received by the students. They gain real life experience operating state of the art equipment, and working in teams, while performing research-like projects, and simultaneously they learn the theoretical foundations of the discipline.

  9. Ion-nanostructure interaction. Comparing simulation and experiment towards surface structuring using nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Holland-Moritz, Henry

    2016-10-18

    Nanotechnology is a buzzword in context of the proceeding miniaturization of devices and their components. Nanoparticles (NPs) can nowadays easily be synthesized from different material compositions by different chemical and physical processes. However, most of these techniques work close to or at the thermal equilibrium. One subsequent approach to tune materials beyond equilibrium conditions is ion beam irradiation. An important effect of this approach is sputtering. Sputtering is enhanced in NPs compared to their bulk counterparts due to their large surface-to-volume ratio, especially when the ion range matches the NP size. In this work, the sputtering effects of Ar{sup +} and Ga{sup +} ion irradiated Au nanoparticles are investigated in detail by Monte Carlo (MC) and molecular dynamics (MD) simulations and a variety of experiments. The sputtering of Ar{sup +} and Ga{sup +} irradiated Au NPs was investigated as a function of ion energy, NP size and impact parameter by the MC code iradina and MD code parcas. The simulation results are directly compared to experiments using high resolution scanning electron microscopy (SEM) of Au NPs on top of Si, whereat the sputter yields are significantly enhanced compared to the MC simulations. Additionally, the interaction of NPs and substrate were investigated by Rutherford backscatter spectrometry (RBS), atomic force microscopy (AFM) and scanning transmission electron microscopy (STEM). A new MC code was developed to study the redeposition of sputtered atoms of Ga{sup +} irradiated Au NP arrays on neighboring NPs. The redeposition can lead to growth of NPs with diameters of 1 nm in vicinity of ∝50 nm NP. These simulations are directly compared to an in situ experiment. Nanostructures, spherical NPs as well as nanowires (NWs) are used as irradiation masks to structure lithium niobate (LNO) using the ion beam enhanced etching (IBEE) technique. The aspect ratio of the obtained structures can be enhanced by a second IBEE step

  10. Interaction of High Flash Point Electrolytes and PE-Based Separators for Li-Ion Batteries

    Directory of Open Access Journals (Sweden)

    Andreas Hofmann

    2015-08-01

    Full Text Available In this study, promising electrolytes for use in Li-ion batteries are studied in terms of interacting and wetting polyethylene (PE and particle-coated PE separators. The electrolytes are characterized according to their physicochemical properties, where the flow characteristics and the surface tension are of particular interest for electrolyte–separator interactions. The viscosity of the electrolytes is determined to be in a range of η = 4–400 mPa∙s and surface tension is finely graduated in a range of γL = 23.3–38.1 mN∙m−1. It is verified that the technique of drop shape analysis can only be used in a limited matter to prove the interaction, uptake and penetration of electrolytes by separators. Cell testing of Li|NMC half cells reveals that those cell results cannot be inevitably deduced from physicochemical electrolyte properties as well as contact angle analysis. On the other hand, techniques are more suitable which detect liquid penetration into the interior of the separator. It is expected that the results can help fundamental researchers as well as users of novel electrolytes in current-day Li-ion battery technologies for developing and using novel material combinations.

  11. Interaction of High Flash Point Electrolytes and PE-Based Separators for Li-Ion Batteries.

    Science.gov (United States)

    Hofmann, Andreas; Kaufmann, Christoph; Müller, Marcus; Hanemann, Thomas

    2015-08-27

    In this study, promising electrolytes for use in Li-ion batteries are studied in terms of interacting and wetting polyethylene (PE) and particle-coated PE separators. The electrolytes are characterized according to their physicochemical properties, where the flow characteristics and the surface tension are of particular interest for electrolyte-separator interactions. The viscosity of the electrolytes is determined to be in a range of η = 4-400 mPa∙s and surface tension is finely graduated in a range of γL = 23.3-38.1 mN∙m(-1). It is verified that the technique of drop shape analysis can only be used in a limited matter to prove the interaction, uptake and penetration of electrolytes by separators. Cell testing of Li|NMC half cells reveals that those cell results cannot be inevitably deduced from physicochemical electrolyte properties as well as contact angle analysis. On the other hand, techniques are more suitable which detect liquid penetration into the interior of the separator. It is expected that the results can help fundamental researchers as well as users of novel electrolytes in current-day Li-ion battery technologies for developing and using novel material combinations.

  12. Interaction of different metal ions with carboxylic acid group: a quantitative study.

    Science.gov (United States)

    Bala, Tanushree; Prasad, B L V; Sastry, Murali; Kahaly, Mousumi Upadhyay; Waghmare, Umesh V

    2007-07-19

    The binding strength of the carboxylic acid group (-COOH) with different divalent metal ions displays considerable variation in arachidic acid (AA) thin films. It is considered that in AA thin films the metal ions straddle the hydrophilic regions of the stacked bilayers of AA molecules via formation of carboxylates. In this study first the uptake of different divalent cations in films of AA is estimated by atomic absorption spectroscopy (AAS). Through the amount of cation uptake, it is found that the strength of binding of different cations varies as Ca2+>Co2+>Pb2+>Cd2+. Variation in the binding strength of different ions is also manifested in experiments where AA thin films are exposed to metal ion mixtures. The higher binding strength of AA with certain metal ions when exposed individually, as well as the preference over the other metal ions when exposed to mixtures, reveal some interesting deviation from the expected behavior based on considerations of ionic radii. For example, Pb2+ is always found to bind to AA much more strongly than Cd2+ even though the latter has smaller ionic radius, indicating that other factors also play an important role in governing the binding strength trends apart from the effects of ionic radii. Then, to get a more meaningful knowledge regarding the binding capability, first-principles calculations based on density functional theory have been applied to study the interaction of different cations with the simplest carboxylic acid, acetic acid, that can result in formation of metal diacetates. Their electronic and molecular structures, cohesive energies, and stiffness of the local potential energy well at the cation (M) site are determined and attempts are made to understand the diversity in geometry and the properties of binding of different metal ions with -COOH group. We find that the calculated M-O bond energies depend sensitively on the chemistry of M atom and follow the experimentally observed trends quite accurately. The trends

  13. Heavy Inertial Confinement Energy: Interactions Involoving Low charge State Heavy Ion Injection Beams

    Energy Technology Data Exchange (ETDEWEB)

    DuBois, Robert D

    2006-04-14

    During the contract period, absolute cross sections for projectile ionization, and in some cases for target ionization, were measured for energetic (MeV/u) low-charge-state heavy ions interacting with gases typically found in high and ultra-high vacuum environments. This information is of interest to high-energy-density research projects as inelastic interactions with background gases can lead to serious detrimental effects when intense ion beams are accelerated to high energies, transported and possibly confined in storage rings. Thus this research impacts research and design parameters associated with projects such as the Heavy Ion Fusion Project, the High Current and Integrated Beam Experiments in the USA and the accelerator upgrade at GSI-Darmstadt, Germany. Via collaborative studies performed at GSI-Darmstadt, at the University of East Carolina, and Texas A&M University, absolute cross sections were measured for a series of collision systems using MeV/u heavy ions possessing most, or nearly all, of their bound electrons, e.g., 1.4 MeV/u Ar{sup +}, Xe{sup 3+}, and U{sup 4,6,10+}. Interactions involving such low-charge-state heavy ions at such high energies had never been previously explored. Using these, and data taken from the literature, an empirical model was developed for extrapolation to much higher energies. In order to extend our measurements to much higher energies, the gas target at the Experimental Storage Ring in GSI-Darmstadt was used. Cross sections were measured between 20 and 50 MeV/u for U{sup 28+}- H{sub 2} and - N{sub 2}, the primary components found in high and ultra-high vacuum systems. Storage lifetime measurements, information inversely proportional to the cross section, were performed up to 180 MeV/u. The lifetime and cross section data test various theoretical approaches used to calculate cross sections for many-electron systems. Various high energy density research projects directly benefit by this information. As a result, the general

  14. Interaction of slow and highly charged ions with surfaces: formation of hollow atoms

    Energy Technology Data Exchange (ETDEWEB)

    Stolterfoht, N.; Grether, M.; Spieler, A.; Niemann, D. [Hahn-Meitner Institut, Berlin (Germany). Bereich Festkoerperphysik; Arnau, A.

    1997-03-01

    The method of Auger spectroscopy was used to study the interaction of highly charged ions with Al and C surfaces. The formation of hollow Ne atoms in the first surface layers was evaluated by means of a Density Functional theory including non-linear screening effects. The time-dependent filling of the hollow atom was determined from a cascade model yielding information about the structure of the K-Auger spectra. Variation of total intensities of the L- and K-Auger peaks were interpreted by the cascade model in terms of attenuation effects on the electrons in the solid. (author)

  15. Evidence for strong Breit interaction in dielectronic recombination of highly charged heavy ions.

    Science.gov (United States)

    Nakamura, Nobuyuki; Kavanagh, Anthony P; Watanabe, Hirofumi; Sakaue, Hiroyuki A; Li, Yueming; Kato, Daiji; Currell, Fred J; Ohtani, Shunsuke

    2008-02-22

    Resonant strengths have been measured for dielectronic recombination of Li-like iodine, holmium, and bismuth using an electron beam ion trap. By observing the atomic number dependence of the state-resolved resonant strength, clear experimental evidence has been obtained that the importance of the generalized Breit interaction (GBI) effect on dielectronic recombination increases as the atomic number increases. In particular, it has been shown that the GBI effect is exceptionally strong for the recombination through the resonant state [1s2s(2)2p(1/2)](1).

  16. Lamb Shift in Radical-Ion Pairs is Physically Equivalent to a Spin-Exchange Interaction

    CERN Document Server

    Vitalis, K M

    2013-01-01

    Radical-ion pairs, fundamental for understanding photosynthesis and the avian magnetic compass, were recently shown to be biological open quantum systems. We here show that the coupling of the radical-pair's spin degrees of freedom to its decohering vibrational reservoir leads to a shift of the radical-pair's magnetic energy levels. The Lamb shift Hamiltonian is diagonal in the singlet-triplet basis, and results in a singlet-triplet energy splitting physically indistinguishable from an exchange interaction. This could have profound implications for understanding photosynthetic reaction centers.

  17. Computational Protein Design with Explicit Consideration of Surface Hydrophobic Patches

    Science.gov (United States)

    Jacak, Ron; Leaver-Fay, Andrew; Kuhlman, Brian

    2011-01-01

    De novo protein design requires the identification of amino-acid sequences that favor the target folded conformation and are soluble in water. One strategy for promoting solubility is to disallow hydrophobic residues on the protein surface during design. However, naturally occurring proteins often have hydrophobic amino acids on their surface that contribute to protein stability via the partial burial of hydrophobic surface area or play a key role in the formation of protein-protein interactions. A less restrictive approach for surface design that is used by the modeling program Rosetta is to parameterize the energy function so that the number of hydrophobic amino acids designed on the protein surface is similar to what is observed in naturally occurring monomeric proteins. Previous studies with Rosetta have shown that this limits surface hydrophobics to the naturally occurring frequency (~28%) but that it does not prevent the formation of hydrophobic patches that are considerably larger than those observed in naturally occurring proteins. Here, we describe a new score term that explicitly detects and penalizes the formation of hydrophobic patches during computational protein design. With the new term we are able to design protein surfaces that include hydrophobic amino acids at naturally occurring frequencies, but do not have large hydrophobic patches. By adjusting the strength of the new score term the emphasis of surface redesigns can be switched between maintaining solubility and maximizing folding free energy. PMID:22223219

  18. The new view of hydrophobic free energy.

    Science.gov (United States)

    Baldwin, Robert L

    2013-04-17

    In the new view, hydrophobic free energy is measured by the work of solute transfer of hydrocarbon gases from vapor to aqueous solution. Reasons are given for believing that older values, measured by solute transfer from a reference solvent to water, are not quantitatively correct. The hydrophobic free energy from gas-liquid transfer is the sum of two opposing quantities, the cavity work (unfavorable) and the solute-solvent interaction energy (favorable). Values of the interaction energy have been found by simulation for linear alkanes and are used here to find the cavity work, which scales linearly with molar volume, not accessible surface area. The hydrophobic free energy is the dominant factor driving folding as judged by the heat capacity change for transfer, which agrees with values for solvating hydrocarbon gases. There is an apparent conflict with earlier values of hydrophobic free energy from studies of large-to-small mutations and an explanation is given. Copyright © 2013 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

  19. A selective chemosensor for fluoride ion and its interaction with Calf Thymus DNA

    Science.gov (United States)

    Ghosh, Soumen; Al Masum, Abdulla; Ganguly, Aniruddha; Islam, Md. Maidul; Alam, Md. Akhtarul; Guchhait, Nikhil

    2017-05-01

    The amido-Schiff base 1 (N1, N3-bis (2-nitrobenzylidene)benzene-1,3-dicabohydrazide) containing a sbnd CONHsbnd group and sbnd CHdbnd Nsbnd linkage has been synthesized by the condensation between isophthalic acid dihydrazide and o-nitrobenzaldehyde. This molecule can act as a fluoride ion sensor with high selectivity and sensitivity. Presence of nitro group in the phenyl ring may be responsible for the detection of fluoride ion visually with a dramatic color change from colorless to deep red in aqueous dimethyl sulphoxide solution. This Schiff base can be used as test kit for sensing of fluoride ion in the solid state. Compound 1 can detect fluoride also in commercially available toothpaste. As the compound has adequate solubility in DMSO-water mixture (7:93, v/v) and having some hydrogen bond donor and acceptor centers, we have investigated its nature of binding with Calf Thymus-DNA (CT-DNA) using theoretical molecular modelling and other experimental methods like UV-vis spectroscopy, circular dichroic and thermal melting studies. Thermodynamic parameters have been obtained using the well known Van't Hoff's equation. From both theoretical and experimental findings it has been observed that it can interact effectively with CT-DNA with binding energy - 7.55 kcal/mol to - 7.50 kcal/mol.

  20. Interaction of 3d transition metal atoms with charged ion projectiles from Electron Nuclear Dynamics computation

    Science.gov (United States)

    Hagelberg, Frank

    2003-03-01

    Computational results on atomic scattering between charged projectiles and transition metal target atoms are presented. This work aims at obtaining detailed information about charge, spin and energy transfer processes that occur between the interacting particles. An in-depth understanding of these phenomena is expected to provide a theoretical basis for the interpretation of various types of ion beam experiments, ranging from gas phase chromatography to spectroscopic observations of fast ions in ferromagnetic media. This contribution focuses on the scattering of light projectiles ranging from He to O, that are prepared in various initial charge states, by 3d transition metal atoms. The presented computations are performed in the framework of Electron Nuclear Dynamics (END)^1 theory which incorporates the coupling between electronic and nuclear degrees of freedom without reliance on the computationally cumbersome and frequently intractable determination of potential energy surfaces. In the present application of END theory to ion - transition metal atom scattering, a supermolecule approach is utilized in conjunction with a spin-unrestricted single determinantal wave function describing the electronic system. Integral scattering, charge and spin exchange cross sections are discussed as functions of the elementary parameters of the problem, such as projectile and target atomic numbers as well as projectile charge and initial kinetic energy. ^1 E.Deumens, A.Diz, R.Longo, Y.Oehrn, Rev.Mod.Phys. 66, 917 (1994)

  1. Ions interacting with complex molecular systems: The effect of a surrounding environment

    Science.gov (United States)

    Zettergren, Henning

    2015-07-01

    This paper highlight results from studies of keV-ion impact on complex molecules and molecular clusters, which have been carried out at the ARIBE facility in Caen (France) during the last decade. Studies of fullerenes, Polycyclic Aromatic Hydrocarbons (PAHs), and biomolecules are reviewed with focus on the effect of a surrounding environment when ions interact with weakly bound clusters of theses species. One common result is that charge and energy are rapidly shared between the individual molecules in the clusters, in contrast to e.g. weakly bound atomic clusters where the charge stay localized to a few atoms from which the electrons are removed during the collisions. Another important finding is that ion collisions may induce reactions within clusters such as e.g. proton transfer and different types of molecular growth processes. In the latter case, these processes may be driven by prompt non-statistical atom knockouts in billiard-ball like atom-atom collisions favouring highly reactive fragments. In contrast, statistical fragmentation in general yields different and less reactive fragments.

  2. Nickel (II) Ions Interaction with Polynucleotides and DNA of Different GC Composition

    CERN Document Server

    Bregadze, Vasil G; Melikishvili, Sophie Z; Melikishvili, Zaza G

    2009-01-01

    The goal of the work was to study the role of GC alternative dimmers in the binding of DNA with Ni (II) ions. The method of ultraviolet difference spectroscopy has been applied to investigate Ni (II) ions interactions with DNA extracted from Clostridium perfringens, Mice liver (C3HA line), Calf thymus, Salmon sperm, Herring sperm, E.coli, Micrococcus luteus and polynucleotides Poly (dA-dT)xPoly (dA-dT), Poly (dG)x Poly (dC), Poly (dG-dC)xPoly (dG-dC). It is shown that Ni (II) ions at outer-spherical binding with DNA double helix from the side of the major groove choose more stable dimmers 3^'-C-G-5^' . . 5^'-G-C-3^' and get bound with N7 atoms of both guanines in dimmer forming G-G interstrand crosslink. It directly correlates to the process of forming point defects of Watson-Crick wrong pair type (creation of rare keto-enolic and amino-imino tautomeric forms) and depurinization.

  3. STEREO observations of the energetic ions in tilted corotating interaction regions

    CERN Document Server

    Bucik, R; Korth, A; Mason, G M; 10.1029/2010JA016311

    2013-01-01

    In this paper we examine suprathermal He ions measured by the SIT (Suprathermal Ion Telescope) instrument associated with tilted corotating interaction regions (CIRs). We use observations of the two STEREO spacecraft (s/c) for the first 2.7 years of the mission, along with ground-based measurements of the solar magnetic field during the unusually long minimum of Solar Cycle 23. Due to the unique configuration of the STEREO s/c orbits we are able to investigate spatial variations in the intensity of the corotating ions on time scales of less than one solar rotation. The observations reveal that the occurrence of the strong CIR events was the most frequent at the beginning of the period. The inclination of the heliospheric current sheet relative to the heliographic equator (the tilt angle) was quite high in the first stage of the mission and gradually flattened with the time, followed by a decrease in the CIR activity. By examining the differences between measurements on the two STEREO s/c we discuss how the ch...

  4. Consistent Treatment of Hydrophobicity in Protein Lattice Models Accounts for Cold Denaturation

    Science.gov (United States)

    van Dijk, Erik; Varilly, Patrick; Knowles, Tuomas P. J.; Frenkel, Daan; Abeln, Sanne

    2016-02-01

    The hydrophobic effect stabilizes the native structure of proteins by minimizing the unfavorable interactions between hydrophobic residues and water through the formation of a hydrophobic core. Here, we include the entropic and enthalpic contributions of the hydrophobic effect explicitly in an implicit solvent model. This allows us to capture two important effects: a length-scale dependence and a temperature dependence for the solvation of a hydrophobic particle. This consistent treatment of the hydrophobic effect explains cold denaturation and heat capacity measurements of solvated proteins.

  5. Three-nucleon interaction in heavy-ion collisions at intermediate energies

    Science.gov (United States)

    Wada, R.

    2017-09-01

    The effect of a three-nucleon (3 N ) interaction is studied for the production of high energy protons in heavy-ion collisions in the incident energy range of 44 to 400 A MeV . The 3 N interaction is incorporated into the antisymmetrized molecular dynamics transport model of Ono [A. Ono, Phys. Rev. C 59, 853 (1999), 10.1103/PhysRevC.59.853] as a 3 N collision term, following a diagram of three consecutive binary collisions. For the theoretical 40Ar+51V reaction studies, no contribution from the 3 N collisions is observed for high energy proton production at the incident energy of 44 A MeV . However when the incident energy increases, the contribution increases gradually. At 200 A MeV and above, the contribution is observed as distinctly harder energy slopes in the proton energy spectra. The model is applied to the available Bevalac data for 40Ar+40Ca at 42 ,92 , and 137 A MeV . The experimental proton energy spectra are reasonably well reproduced at angles θ ≥70∘ for all three incident energies, showing negligible 3 N contributions at 42 A MeV and significant contributions at 137 A MeV at the large laboratory angles. Good agreement at these large angles, where the 3 N collision is a major mechanism to produce such protons, strongly indicates for the first time the importance of the 3 N interaction in intermediate heavy ion reactions in a full transport calculation. The possible relation between the 3 N collision term and the short range and the tensor interactions is suggested.

  6. Protein C production: metal ion/protein interfacial interaction in immobilized metal affinity chromatography.

    Science.gov (United States)

    Lee, James J; Thiessen, Eileen; Bruley, Duane F

    2005-01-01

    Protein C (PC) is an essential blood factor in the human blood coagulation cascade. PC can help achieve blood hemostasis in many deadly disease conditions such as sepsis, cancer, HIV, etc.; reduced oxygen transport due to blood agglutination within the body can cause tissue death and organ failure as a result of low oxygen transport. Our goal is to produce large quantities of low cost zymogen PC for the treatment and prevention of blood clotting resulting from many disease states, as well as provide an effective therapy for PC deficiency. Current studies show that Immobilized Metal Affinity Chromatography (IMAC) has high specificity and can be used for difficult separations among homologous proteins at relatively low cost compared to current methods, such as Immunoaffinity Chromatography. Thus, we are investigating the optimization of IMAC for the separation and purification of PC from Cohn fraction IV-I. Molecular interactions within the chromatography column involve many parameters that include: the use and type of chromatographic gel and buffer solution, the pH, temperature, metal ion, chelator, and the sequence and structure of the protein itself. These parameters all influence the protein's interaction with the column. Experimental equilibrium isotherms show that PC has primary and secondary binding characteristics, demonstrating that the interaction is not just a simple process of one protein binding to one metal ion. Understanding the thermodynamics of interfacial interaction between proteins and surface-bound Cu2+ is essential to optimizing IMAC for PC purification, as well as for separation of other proteins in general. Hence we are undertaking theoretical and experimental studies of IDA-Cu/PC adsorption. The differences in structures of PC and other critical homologous blood factors are examined using the protein visualization program Cn3D. A better understanding of the interfacial phenomena will help determine the most effective conditions to achieve our

  7. Intra-pulse transition between ion acceleration mechanisms in intense laser-foil interactions

    Energy Technology Data Exchange (ETDEWEB)

    Padda, H.; King, M.; Gray, R. J.; Powell, H. W.; Gonzalez-Izquierdo, B.; Wilson, R.; Dance, R. J.; MacLellan, D. A.; Butler, N. M. H.; Capdessus, R.; McKenna, P., E-mail: paul.mckenna@strath.ac.uk [SUPA Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Stockhausen, L. C. [Centro de Laseres Pulsados (CLPU), Parque Cientifico, Calle del Adaja s/n. 37185 Villamayor, Salamanca (Spain); Carroll, D. C. [Central Laser Facility, STFC Rutherford Appleton Laboratory, Oxfordshire OX11 0QX (United Kingdom); Yuan, X. H. [Key Laboratory for Laser Plasmas (Ministry of Education) and Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Collaborative Innovation Center of IFSA (CICIFSA), Shanghai Jiao Tong University, Shanghai 200240 (China); Borghesi, M. [Centre for Plasma Physics, Queens University Belfast, Belfast BT7 1NN (United Kingdom); Neely, D. [SUPA Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Central Laser Facility, STFC Rutherford Appleton Laboratory, Oxfordshire OX11 0QX (United Kingdom)

    2016-06-15

    Multiple ion acceleration mechanisms can occur when an ultrathin foil is irradiated with an intense laser pulse, with the dominant mechanism changing over the course of the interaction. Measurement of the spatial-intensity distribution of the beam of energetic protons is used to investigate the transition from radiation pressure acceleration to transparency-driven processes. It is shown numerically that radiation pressure drives an increased expansion of the target ions within the spatial extent of the laser focal spot, which induces a radial deflection of relatively low energy sheath-accelerated protons to form an annular distribution. Through variation of the target foil thickness, the opening angle of the ring is shown to be correlated to the point in time transparency occurs during the interaction and is maximized when it occurs at the peak of the laser intensity profile. Corresponding experimental measurements of the ring size variation with target thickness exhibit the same trends and provide insight into the intra-pulse laser-plasma evolution.

  8. Ionic profiles close to dielectric discontinuities: Specific ion-surface interactions

    CERN Document Server

    Markovich, Tomer; Orland, Henri

    2016-01-01

    We study, by incorporating short-range ion-surface interactions, ionic profiles of electrolyte solutions close to a non-charged interface between two dielectric media. In order to account for important correlation effects close to the interface, the ionic profiles are calculated beyond mean-field theory, using the loop expansion of the free energy. We show how it is possible to overcome the well-known deficiency of the regular loop expansion close to the dielectric jump, and treat the non-linear boundary conditions within the framework of field theory. The ionic profiles are obtained analytically to one-loop order in the free energy, and their dependence on different ion-surface interactions is investigated. The Gibbs adsorption isotherm, as well as the ionic profiles are used to calculate the surface tension, in agreement with the reverse Hofmeister series. Consequently, from the experimentally-measured surface tension, one can extract a single adhesivity parameter, which can be used within our model to quan...

  9. Ion scale nonlinear interaction triggered by disparate scale electron temperature gradient mode

    Energy Technology Data Exchange (ETDEWEB)

    Moon, Chanho, E-mail: moon@nifs.ac.jp [Department of Electronic Engineering, Tohoku University, Sendai 980-8579 (Japan); National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Kobayashi, Tatsuya; Itoh, Kimitaka [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Hatakeyama, Rikizo; Kaneko, Toshiro [Department of Electronic Engineering, Tohoku University, Sendai 980-8579 (Japan)

    2015-05-15

    We have observed that the disparate scale nonlinear interactions between the high-frequency (∼0.4 MHz) electron temperature gradient (ETG) mode and the ion-scale low-frequency fluctuations (∼kHz) were enhanced when the amplitude of the ETG mode exceeded a certain threshold. The dynamics of nonlinear coupling between the ETG mode and the drift wave (DW) mode has already been reported [C. Moon, T. Kaneko, and R. Hatakeyama, Phys. Rev. Lett. (2013)]. Here, we have newly observed that another low-frequency fluctuation with f ≃ 3.6 kHz, i.e., the flute mode, was enhanced, corresponding to the saturation of the DW mode growth. Specifically, the bicoherence between the flute mode and the DW mode reaches a significant level when the ∇T{sub e}/T{sub e} strength exceeded 0.54 cm{sup −1}. Thus, it is shown that the ETG mode energy was transferred to the DW mode, and then the energy was ultimately transferred to the flute mode, which was triggered by the disparate scale nonlinear interactions between the ETG and ion-scale low-frequency modes.

  10. Oblique Interaction of Dust-ion Acoustic Solitons with Superthermal Electrons in a Magnetized Plasma

    Science.gov (United States)

    Parveen, Shahida; Mahmood, Shahzad; Adnan, Muhammad; Qamar, Anisa

    2018-01-01

    The oblique interaction between two dust-ion acoustic (DIA) solitons travelling in the opposite direction, in a collisionless magnetized plasma composed of dynamic ions, static dust (positive/negative) charged particles and interialess kappa distributed electrons is investigated. By employing extended Poincaré-Lighthill-Kuo (PLK) method, Korteweg-de Vries (KdV) equations are derived for the right and left moving low amplitude DIA solitons. Their trajectories and corresponding phase shifts before and after their interaction are also obtained. It is found that in negatively charged dusty plasma above the critical dust charged to ion density ratio the positive polarity pulse is formed, while below the critical dust charged density ratio the negative polarity pulse of DIA soliton exist. However it is found that only positive polarity pulse of DIA solitons exist for the positively charged dust particles case in a magnetized nonthermal plasma. The nonlinearity coefficient in the KdV equation vanishes for the negatively charged dusty plasma case for a particular set of parameters. Therefore, at critical plasma density composition for negatively charged dust particles case, the modified Korteweg-de Vries (mKdV) equations having cubic nonlinearity coefficient of the DIA solitons, and their corresponding phase shifts are derived for the left and right moving solitons. The effects of the system parameters including the obliqueness of solitons propagation with respect to magnetic field direction, superthermality of electrons and concentration of positively/negatively static dust charged particles on the phase shifts of the colliding solitons are also discussed and presented numerically. The results are applicable to space magnetized dusty plasma regimes.

  11. In vitro interaction between homocysteine and copper ions: Potential redox implications.

    Science.gov (United States)

    Carrasco-Pozo, Catalina; Alvarez-Lueje, Alejandro; Olea-Azar, Claudio; López-Alarcón, Camilo; Speisky, Hernán

    2006-10-01

    Homocysteine (Hcys) has been implicated in various oxidative stress-related disorders. The presence of a thiol on its structure allows Hcys to exert a double-edge redox action. Depending on whether Cu2+ ions occur concomitantly, Hcys can either promote or prevent free radical generation and its consequences. We have addressed in vitro the interaction between Hcys and Cu2+ ions, in terms of the consequences that such interaction may have on the free radical scavenging properties of Hcys and on the redox state and redox activity of the metal. To this end, we investigated the free radical-scavenging, O2(*-)-generating, and ascorbate-oxidizing properties of the interacting species by assessing the bleaching of ABTS*+ radicals, the reduction of O2(*-)-dependent cytochrome c, and the copper-dependent oxidation of ascorbate, respectively. In addition, electron paramagnetic resonance and Cu(I)-bathocuproine formation were applied to assess the formation of paramagnetic complexes and the metal redox state. Upon a brief incubation, the Hcys/Cu2+ interaction led to a decrease in the free radical-scavenging properties of Hcys, and to a comparable loss of the thiol density. Both effects were partial and were not modified by increasing the incubation time, despite the presence of Cu2+ excess. Depending on the molar Hcys:Cu2+ ratio, the interaction resulted in the formation of mixtures that appear to contain time-stable and ascorbate-reducible Cu(II) complexes (for ratios up to 2:1), and ascorbate- and oxygen-redox-inactive Cu(I) complexes (for ratios up to 4:1). Increasing the interaction ratio beyond 4:1 was associated with the sudden appearance of an O2(*-)-generating activity. The data indicate that depending on the molar ratio of interaction, Hcys and Cu2+ react to form copper complexes that can promote either antioxidant or pro-oxidant actions. We speculate that the redox activity arising from a large molar Hcys excess may partially underlie the association between hyper

  12. Accelerator-Based Studies of Heavy Ion Interactions Relevant to Space Biomedicine

    Science.gov (United States)

    Miller, J.; Heilbronn, L.; Zeitlin, C.

    1999-01-01

    Evaluation of the effects of space radiation on the crews of long duration space missions must take into account the interactions of high energy atomic nuclei in spacecraft and planetary habitat shielding and in the bodies of the astronauts. These heavy ions (i.e. heavier than hydrogen), while relatively small in number compared to the total galactic cosmic ray (GCR) charged particle flux, can produce disproportionately large effects by virtue of their high local energy deposition: a single traversal by a heavy charged particle can kill or, what may be worse, severely damage a cell. Research into the pertinent physics and biology of heavy ion interactions has consequently been assigned a high priority in a recent report by a task group of the National Research Council. Fragmentation of the incident heavy ions in shielding or in the human body will modify an initially well known radiation field and thereby complicate both spacecraft shielding design and the evaluation of potential radiation hazards. Since it is impractical to empirically test the radiation transport properties of each possible shielding material and configuration, a great deal of effort is going into the development of models of charged particle fragmentation and transport. Accurate nuclear fragmentation cross sections (probabilities), either in the form of measurements with thin targets or theoretical calculations, are needed for input to the transport models, and fluence measurements (numbers of fragments produced by interactions in thick targets) are needed both to validate the models and to test specific shielding materials and designs. Fluence data are also needed to characterize the incident radiation field in accelerator radiobiology experiments. For a number of years, nuclear fragmentation measurements at GCR-like energies have been carried out at heavy ion accelerators including the LBL Bevalac, Saturne (France), the Synchrophasotron and Nuklotron (Dubna, Russia), SIS-18 (GSI, Germany), the

  13. Nuclear-interaction correction of integrated depth dose in carbon-ion radiotherapy treatment planning

    Science.gov (United States)

    Inaniwa, T.; Kanematsu, N.; Hara, Y.; Furukawa, T.

    2015-01-01

    In treatment planning of charged-particle therapy, tissue heterogeneity is conventionally modeled as water with various densities, i.e. stopping effective densities {ρ\\text{S}}, and the integrated depth dose measured in water (IDD) is applied accordingly for the patient dose calculation. Since the chemical composition of body tissues is different from that of water, this approximation causes dose calculation errors, especially due to difference in nuclear interactions. Here, we propose and validate an IDD correction method for these errors in patient dose calculations. For accurate handling of nuclear interactions, {ρ\\text{S}} of the patient is converted to nuclear effective density {ρ\\text{N}}, defined as the ratio of the probability of nuclear interactions in the tissue to that in water using a recently formulated semi-empirical relationship between the two. The attenuation correction factor φ \\text{w}\\text{p}, defined as the ratio of the attenuation of primary carbon ions in a patient to that in water, is calculated from a linear integration of {ρ\\text{N}} along the beam path. In our treatment planning system, a carbon-ion beam is modeled to be composed of three components according to their transverse beam sizes: primary carbon ions, heavier fragments, and lighter fragments. We corrected the dose contribution from primary carbon ions to IDD as proportional to φ \\text{w}\\text{p}, and corrected that from lighter fragments as inversely proportional to φ \\text{w}\\text{p}. We tested the correction method for some non-water materials, e.g. milk, lard, ethanol and water solution of potassium phosphate (K2HPO4), with un-scanned and scanned carbon-ion beams. In un-scanned beams, the difference in IDD between a beam penetrating a 150 mm-thick layer of lard and a beam penetrating water of the corresponding thickness amounted to -4%, while it was +6% for a 150 mm-thick layer of 40% K2HPO4. The observed differences were accurately predicted by the

  14. Coulombic interactions during advection-dominated transport of ions in porous media

    Science.gov (United States)

    Muniruzzaman, Muhammad; Stolze, Lucien; Rolle, Massimo

    2017-04-01

    Solute transport of charged species in porous media is significantly affected by the electrochemical migration term resulting from the charge-induced interactions among dissolved ions and with solid surfaces. Therefore, the characterization of such Coulombic interactions and their effect on multicomponent ionic transport is of critical importance for assessing the fate of charged solutes in porous media. In this work we present a detailed investigation of the electrochemical effects during conservative multicomponent ionic transport in homogeneous and heterogeneous domains by means of laboratory bench-scale experiments and numerical simulations. The investigation aims at quantifying the key role of small-scale electrostatic interactions in flow-through systems, especially when advection is the dominant mass-transfer process. Considering dilute solutions of strong electrolytes (e.g., MgCl2 and NaBr) we report results showing the important role of Coulombic interactions in the lateral displacement of the different ionic species for steady-state transport scenarios in which the solutions are continuously injected through different portions of the flow-through chamber [1, 2]. Successively, we focus our attention on transient transport and pulse injection of the electrolytes. In these experiments high-resolution spatial and temporal monitoring of the ions' concentrations (600 samples; 1800 concentration measurements), at closely spaced outlet ports (5 mm), allowed us resolving the effects of charge interactions on the temporal breakthrough and spatial profiles of the cations and anions [3]. The interpretation of the experimental results requires a multicomponent modeling approach with an accurate description of local hydrodynamic dispersion, as well as the explicit quantification of the dispersive fluxes' cross-coupling due to the Coulombic interactions between the charged species. A new 2-D simulator [4], coupling the solution of the multicomponent ionic transport

  15. Specific ion and buffer effects on protein-protein interactions of a monoclonal antibody.

    Science.gov (United States)

    Roberts, D; Keeling, R; Tracka, M; van der Walle, C F; Uddin, S; Warwicker, J; Curtis, R

    2015-01-05

    Better predictive ability of salt and buffer effects on protein-protein interactions requires separating out contributions due to ionic screening, protein charge neutralization by ion binding, and salting-in(out) behavior. We have carried out a systematic study by measuring protein-protein interactions for a monoclonal antibody over an ionic strength range of 25 to 525 mM at 4 pH values (5, 6.5, 8, and 9) in solutions containing sodium chloride, calcium chloride, sodium sulfate, or sodium thiocyante. The salt ions are chosen so as to represent a range of affinities for protein charged and noncharged groups. The results are compared to effects of various buffers including acetate, citrate, phosphate, histidine, succinate, or tris. In low ionic strength solutions, anion binding affinity is reflected by the ability to reduce protein-protein repulsion, which follows the order thiocyanate > sulfate > chloride. The sulfate specific effect is screened at the same ionic strength required to screen the pH dependence of protein-protein interactions indicating sulfate binding only neutralizes protein charged groups. Thiocyanate specific effects occur over a larger ionic strength range reflecting adsorption to charged and noncharged regions of the protein. The latter leads to salting-in behavior and, at low pH, a nonmonotonic interaction profile with respect to sodium thiocyanate concentration. The effects of thiocyanate can not be rationalized in terms of only neutralizing double layer forces indicating the presence of an additional short-ranged protein-protein attraction at moderate ionic strength. Conversely, buffer specific effects can be explained through a charge neutralization mechanism, where buffers with greater valency are more effective at reducing double layer forces at low pH. Citrate binding at pH 6.5 leads to protein charge inversion and the formation of attractive electrostatic interactions. Throughout the report, we highlight similarities in the measured

  16. Interaction of plasma-generated water cluster ions with chemically-modified Si surfaces investigated by infrared absorption spectroscopy

    Directory of Open Access Journals (Sweden)

    Ayumi Hirano-Iwata

    2016-03-01

    Full Text Available We have investigated the interaction of water cluster ions generated by discharge plasma, with chemically modified Si surfaces using infrared absorption spectroscopy in the multiple internal reflection geometry. We observe that water cluster ions readily adsorb on SiO2-covered Si surfaces to form water droplets. We demonstrate that positively- and negatively-charged cluster ions adsorb on the SiO2-covered Si surface in different manners, indicating ionic interaction of the water droplets with the negatively-charged SiO2 surface. Water droplets formed on the protein-coated surface rupture the amide bond of the proteins, suggesting the function of protein decomposition of water cluster ions.

  17. Encapsulation and retention of chelated-copper inside hydrophobic nanoparticles

    DEFF Research Database (Denmark)

    Hervella, Pablo; Ortiz, Elisa Parra; Needham, David

    2016-01-01

    that our endogenous-inspired nanoparticle strategies for imaging and therapeutics are focused on encapsulating and retaining imaging ions such as copper inside novel hydrophobic nanoparticles. In this paper, we describe a new approach to label the core of hydrophobic nanoparticles composed of Glyceryl...... Trioleate (Triolein) with copper using the hydrophobic chelator Octaethyl porphyrin (OEP). RESEARCH PLAN AND METHODS: The research plan for this study was to (1) Formulate nanoparticles and control nanoparticle size using a modification of the solvent injection technique, named fast ethanol injection; (2...... to nanoparticles was >95% at low OEP-Cu concentrations. In the absence of OEP, copper was not detected in nanoparticles demonstrating the role of the hydrophobic chelator OEP in the encapsulation of the otherwise water-soluble copper inside lipid nanoparticles. (4) The in vitro retention upon incubation at 37°C...

  18. Exploration of electrostatic interaction in the hydrophobic pocket of lysozyme: Importance of ligand-induced perturbation of the secondary structure on the mode of binding of exogenous ligand and possible consequences.

    Science.gov (United States)

    Panja, Sudipta; Halder, Mintu

    2016-08-01

    Exogenous ligand binding can be adequate to alter the secondary structure of biomolecules besides other external stimuli. In such cases, structural alterations can complicate on the nature of interaction with the exogenous molecules. In order to accommodate the exogenous ligand, the biomolecule has to unfold resulting in a considerable change to its properties. If the bound ligand can be unbound, the biomolecule gets the opportunity to refold back and return to its native state. Keeping this in mind, we have purposely investigated the interaction of tartrazine (TZ), a well abundant azo food colorant, with two homologous lysozymes, namely, human lysozyme (HLZ) and chicken egg white lysozyme (CEWLZ) in physiological pH condition. The binding of TZ with lysozymes has been identified to accompany a ligand-induced secondary structure alteration as indicated by the circular dichroism spectra, and the reduction of α-helical content is more with HLZ than CEWLZ. Interestingly, the binding is identified to occur in the electronic ground state of TZ with lysozyme in its hydrophobic cavity, containing excess of positive charge, predominantly via electrostatic interaction. With increase of salinity of the medium the protein tends to refold back due to wakening of electrostatic forces and consequent reduction of strength of ligand interaction and unbinding. The entropy enthalpy compensation (EEC) has been probed to understand the binding features and it is found that CEWLZ-TZ shows better compensation than HLZ-TZ complex. This is presumably due to the fact that with CEWLZ the binding does not accompany substantial change in the protein secondary structure and hence ineffective to scramble the EEC. The present study initiates the importance of ligand-perturbed structural alteration of biomolecule in controlling the thermodynamics of binding. If there is a considerable alteration of the protein secondary structure due to binding, it is indicative that such changes should bring in

  19. Hydrophobic collapse of trigger factor monomer in solution.

    Directory of Open Access Journals (Sweden)

    Kushagra Singhal

    Full Text Available Trigger factor (TF is a chaperone, found in bacterial cells and chloroplasts, that interacts with nascent polypeptide chains to suppress aggregation. While its crystal structure has been resolved, the solution structure and dynamics are largely unknown. We performed multiple molecular dynamics simulations on Trigger factor in solution, and show that its tertiary domains display collective motions hinged about inter-domain linkers with minimal or no loss in secondary structure. Moreover, we find that isolated TF typically adopts a collapsed state, with the formation of domain pairs. This collapse of TF in solution is induced by hydrophobic interactions and stabilised by hydrophilic contacts. To determine the nature of the domain interactions, we analysed the hydrophobicity of the domain surfaces by using the hydrophobic probe method of Acharya et al., as the standard hydrophobicity scales predictions are limited due to the complex environment. We find that the formation of domain pairs changes the hydrophobic map of TF, making the N-terminal and arm2 domain pair more hydrophilic and the head and arm1 domain pair more hydrophobic. These insights into the dynamics and interactions of the TF domains are important to eventually understand chaperone-substrate interactions and chaperone function.

  20. Experimental and computational surface hydrophobicity analysis of a non-enveloped virus and proteins.

    Science.gov (United States)

    Heldt, Caryn L; Zahid, Amna; Vijayaragavan, K Saagar; Mi, Xue

    2017-05-01

    The physical characteristics of viruses needs to be understood in order to manipulate the interaction of viruses with host cells, as well as to create specific molecular recognition techniques to detect, purify, and remove viruses. Viruses are generally believed to be positively charged at physiological pH, but there are few other defining characteristics. Here, we have experimentally and computationally demonstrated that a non-enveloped virus is more hydrophobic than a panel of model proteins. Reverse-phase and hydrophobic interaction chromatography and ANS fluorescence determined the experimental hydrophobic strength of each entity. Computational surface hydrophobicity was calculated by the solvent exposed surface area of the protein weighted by the hydrophobicity of each amino acid. The results obtained indicate a strong correlation between the computational surface hydrophobicity and experimentally determined hydrophobicity using reverse-phase chromatography and ANS fluorescence. The surface hydrophobicity did not compare strongly to the weighted average of the amino acid sequence hydrophobicity. This demonstrates that our simple method of calculating the surface hydrophobicity gives general hydrophobicity information about proteins and viruses with crystal structures. In the process, this method demonstrated that porcine parvovirus (PPV) is more hydrophobic than the model proteins used in this study. This adds an additional dimension to currently known virus characteristics and can improve our manipulation of viruses for gene therapy targeting, surface adsorption and general understanding of virus interactions. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Adsorption of antimicrobial indolicidin-derived peptides on hydrophobic surfaces.

    Science.gov (United States)

    Tsai, Ching-Wei; Ruaan, Ruoh-Chyu; Liu, Chih-I

    2012-07-17

    The hydrophobic interaction between antimicrobial peptides and membrane hydrophobic cores is usually related to their cytotoxicity. In this study, the adsorption mechanism of five plasma membrane-associated peptides, indolicidin (IL) and its four derivatives, with hydrophobic ligands was investigated to understand the relationship between peptide hydrophobicity and bioactivity. The hydrophobic adsorption mechanisms of IL and its derivatives were interpreted thermodynamically and kinetically by reversed-phase chromatography (RPC) analysis and surface plasmon resonance (SPR) measurement, respectively. IL and its derivatives possess a similar random coil structure in both aqueous and organic solvents. Thermodynamic analysis showed that the binding enthalpy of peptides with higher electropositivity was lower than those with lower electropositivity and exhibited unfavorable binding entropy. Higher electropositivity peptides adsorbed to the hydrophobic surface arising from the less bound solvent on the peptide surface. A comparison with the kinetic analysis showed that IL and its derivatives adopt a two-state binding model (i.e., adsorption onto and self-association on the hydrophobic acyl chain) to associate with the hydrophobic surface, and the binding affinity of peptide self-association correlates well with peptide hemolysis. Consequently, this study provided a novel concept for understanding the action of plasma membrane-associated peptides.

  2. Structure of aqueous electrolyte solutions near a hydrophobic surface

    Directory of Open Access Journals (Sweden)

    M.Kinoshita

    2007-09-01

    Full Text Available The structure of aqueous solutions of 1:1 salts (KCl, NaCl, KF,and CsI near a hydrophobic surface is analysed using the angle-dependent integral equation theory. Water molecules are taken to be hard spheres imbedded with multipolar moments including terms up to octupole order, and hard spherical ions are immersed in this model water. The many-body interactions associated with molecular polarizability are treated at the self-consistent mean field level. The effects of cationic and anionic sizes and salt concentration in the bulk are discussed in detail. As the salt concentration increases, the layer of water molecules next to the surface becomes denser but its orientational order remains almost unchanged. The concentration of each ion at the surface can be drastically different from that in the bulk. Asa striking example, at sufficiently low salt concentrations, the concentration of I- is about 500 times higher than that of F- at the surface.

  3. Effects of protein-protein interactions and ligand binding on the ion permeation in KCNQ1 potassium channel.

    Science.gov (United States)

    Jalily Hasani, Horia; Ganesan, Aravindhan; Ahmed, Marawan; Barakat, Khaled H

    2018-01-01

    The voltage-gated KCNQ1 potassium ion channel interacts with the type I transmembrane protein minK (KCNE1) to generate the slow delayed rectifier (IKs) current in the heart. Mutations in these transmembrane proteins have been linked with several heart-related issues, including long QT syndromes (LQTS), congenital atrial fibrillation, and short QT syndrome. Off-target interactions of several drugs with that of KCNQ1/KCNE1 ion channel complex have been known to cause fatal cardiac irregularities. Thus, KCNQ1/KCNE1 remains an important avenue for drug-design and discovery research. In this work, we present the structural and mechanistic details of potassium ion permeation through an open KCNQ1 structural model using the combined molecular dynamics and steered molecular dynamics simulations. We discuss the processes and key residues involved in the permeation of a potassium ion through the KCNQ1 ion channel, and how the ion permeation is affected by (i) the KCNQ1-KCNE1 interactions and (ii) the binding of chromanol 293B ligand and its derivatives into the complex. The results reveal that interactions between KCNQ1 with KCNE1 causes a pore constriction in the former, which in-turn forms small energetic barriers in the ion-permeation pathway. These findings correlate with the previous experimental reports that interactions of KCNE1 dramatically slows the activation of KCNQ1. Upon ligand-binding onto the complex, the energy-barriers along ion permeation path are more pronounced, as expected, therefore, requiring higher force in our steered-MD simulations. Nevertheless, pulling the ion when a weak blocker is bound to the channel does not necessitate high force in SMD. This indicates that our SMD simulations have been able to discern between strong and week blockers and reveal their influence on potassium ion permeation. The findings presented here will have some implications in understanding the potential off-target interactions of the drugs with the KCNQ1/KCNE1 channel

  4. Fluorescence quenching studies on the interaction of a novel deepened cavitand towards some transition metal ions.

    Science.gov (United States)

    Li, Yin; Csók, Zsolt; Szuroczki, Péter; Kollár, László; Kiss, László; Kunsági-Máté, Sándor

    2013-10-17

    A novel 'three-level' deepened cavitand featuring a significantly sizable portal has been synthesized and its interaction with some transition metal ions has been investigated in THF/H2O binary solvent using fluorescence quenching technique. The results suggest that among the used transition metal ions including Ag(+), Cd(2+), Cu(2+), Fe(3+), Cr(3+), Hg(2+), La(3+), Mn(2+), Ni(2+), Zn(2+) and Co(2+), only Fe(3+) and Cu(2+) show good quenching ability. In order to interpret the quenching mechanism, the Stern-Volmer kinetics, and the presence of both the dynamic and static quenching have been discussed. It was found that the simultaneous presence of the sphere-of-action static quenching and dynamic quenching model agrees very well with the experimental results. The limits of detection for Fe(3+) and Cu(2+) were found to be 2.1×10(-6) mol L(-1) (3σ) and 3.6×10(-6) mol L(-1) (3σ), respectively. Cations with potential interference, such as K(+), Na(+), Mg(2+), Ca(2+), Co(2+), La(3+) and Mn(2+) do not have significant effects on the determinations of Fe(3+) and Cu(2+). This cavitand can be potentially applied as optical sensor for the detection of Fe(3+) and Cu(2+). Copyright © 2013 Elsevier B.V. All rights reserved.

  5. Ion-beam-plasma interaction effects on electrostatic solitary wave propagation in ultradense relativistic quantum plasmas

    Science.gov (United States)

    Elkamash, I. S.; Kourakis, I.; Haas, F.

    2017-10-01

    Understanding the transport properties of charged particle beams is important not only from a fundamental point of view but also due to its relevance in a variety of applications. A theoretical model is established in this article, to model the interaction of a tenuous positively charged ion beam with an ultradense quantum electron-ion plasma, by employing a rigorous relativistic quantum-hydrodynamic (fluid plasma) electrostatic model proposed in McKerr et al. [M. McKerr, F. Haas, and I. Kourakis, Phys. Rev. E 90, 033112 (2014), 10.1103/PhysRevE.90.033112]. A nonlinear analysis is carried out to elucidate the propagation characteristics and the existence conditions of large amplitude electrostatic solitary waves propagating in the plasma in the presence of the beam. Anticipating stationary profile excitations, a pseudomechanical energy balance formalism is adopted to reduce the fluid evolution equation to an ordinary differential equation. Exact solutions are thus obtained numerically, predicting localized excitations (pulses) for all of the plasma state variables, in response to an electrostatic potential disturbance. An ambipolar electric field form is also obtained. Thorough analysis of the reality conditions for all variables is undertaken in order to determine the range of allowed values for the solitonic pulse speed and how it varies as a function of the beam characteristics (beam velocity and density).

  6. Hadron production in relativistic heavy ion interactions and the search for the quark-gluon plasma

    Energy Technology Data Exchange (ETDEWEB)

    Tannenbaum, M.J.

    1989-12-01

    The course starts with an introduction, from the experimentalist's point of view, of the challenge of measuring Relativistic Heavy Ion interactions. A review of some theoretical predictions for the expected signatures of the quark gluon plasma will be made, with a purpose to understand how they relate to quantities which may be experimentally measured. A short exposition of experimental techniques and details is given including charged particles in matter, momentum resolution, kinematics and Lorentz Transformations, calorimetry. Principles of particle identification including magnetic spectrometers, time of flight measurement. Illustrations using the E802 spectrometer and other measured results. Resolution smearing of spectra, and binning effects. Parent to daughter effects in decay, with {pi}{sup 0} {yields} {gamma} {gamma} as an example. The experimental situation from the known data in p -- p collisions and proton-nucleus reactions is reviewed and used as a basis for further discussions. The Cronin Effect'' and the Seagull Effect'' being two arcana worth noting. Then, selected experiments from the BNL and CERN heavy ion programs are discussed in detail. 118 refs., 45 figs.

  7. The hydrophobic effect: Molecular dynamics simulations of water confined between extended hydrophobic and hydrophilic surfaces

    DEFF Research Database (Denmark)

    Jensen, Morten Østergaard; Mouritsen, Ole G.; Peters, Günther H.J.

    2004-01-01

    -correlation functions reveal that water molecules have characteristic diffusive behavior and orientational ordering due to the lack of hydrogen bonding interactions with the surface. These observations suggest that the altered dynamical properties of water in contact with extended hydrophobic surfaces together...... experimental data from x-ray reflectivity measurements, reveal a uniform weak de-wetting characteristic for the extended hydrophobic surface, while the hydrophilic surface is weakly wetted. These microscopic data are consistent with macroscopic contact angle measurements. Specific water orientation is present...... at both surfaces. The ordering is characteristically different between the surfaces and of longer range at the hydrophilic surface. Furthermore, the dynamic properties of water are different at the two surfaces and different from the bulk behavior. In particular, at the hydrophobic surface, time...

  8. Non-resonant interacting ion acoustic waves in a magnetized plasma

    Energy Technology Data Exchange (ETDEWEB)

    Maccari, Attilio [Technical Institute ' G Cardano' , Monterotondo, Rome (Italy)

    1999-01-29

    We perform an analytical and numerical investigation of the interaction among non-resonant ion acoustic waves in a magnetized plasma. Waves are supposed to be non-resonant, i.e. with different group velocities that are not close to each other. We use an asymptotic perturbation method, based on Fourier expansion and spatio-temporal rescaling. We show that the amplitude slow modulation of Fourier modes cannot be described by the usual nonlinear Schroedinger equation but by a new model system of nonlinear evolution equations. This system is C-integrable, i.e. it can be linearized through an appropriate transformation of the dependent and independent variables. We demonstrate that a subclass of solutions gives rise to envelope solitons. Each envelope soliton propagates with its own group velocity. During a collision solitons maintain their shape, the only change being a phase shift. Numerical results are used to check the validity of the asymptotic perturbation method. (author)

  9. Interactions of Native Cyclodextrins with Metal Ions and Inorganic Nanoparticles: Fertile Landscape for Chemistry and Materials Science.

    Science.gov (United States)

    Prochowicz, Daniel; Kornowicz, Arkadiusz; Lewiński, Janusz

    2017-11-22

    Readily available cyclodextrins (CDs) with an inherent hydrophobic internal cavity and hydrophilic external surface are macrocyclic entities that display a combination of molecular recognition and complexation properties with vital implications for host-guest supramolecular chemistry. While the host-guest chemistry of CDs has been widely recognized and led to their exploitation in a variety of important functions over the last five decades, these naturally occurring macrocyclic systems have emerged only recently as promising macrocyclic molecules to fabricate environmentally benign functional nanomaterials. This review surveys the development in the field paying special attention to the synthesis and emerging uses of various unmodified CD-metal complexes and CD-inorganic nanoparticle systems and identifies possible future directions. The association of a hydrophobic cavity of CDs with metal ions or various inorganic nanoparticles is a very appealing strategy for controlling the inorganic subunits properties in the very competitive water environment. In this review we provide the most prominent examples of unmodified CDs' inclusion complexes with organometallic guests and update the research in this field from the past decade. We discuss also the coordination flexibility of native CDs to metal ions in CD-based metal complexes and summarize the progress in the synthesis and characterization of CD-metal complexes and their use in catalysis and sensing as well as construction of molecular magnets. Then we provide a comprehensive overview of emerging applications of native CDs in materials science and nanotechnology. Remarkably, in the past few years CDs have appeared as attractive building units for the synthesis of carbohydrate metal-organic frameworks (CD-MOFs) in a combination of alkali-metal cations. The preparation of this new class of highly porous materials and their applications in the separation of small molecules, the loading of drug molecules, as well as

  10. The acute and chronic toxicity of major geochemical ions to Hyalella azteca Ion interactions and comparisons to other species

    Science.gov (United States)

    We have previously reported that the acute and chronic toxicities of major geochemical ions (Na, K, Ca, Mg, Cl, SO4, HCO3) to Ceriodaphnia dubia can involve multiple, independent mechanisms. The toxicities of K, Mg, and Ca salts were best related to the chemical activity of the c...

  11. Precision Tests of the Electroweak Interaction using Trapped Atoms and Ions

    Energy Technology Data Exchange (ETDEWEB)

    Melconian, Daniel George [Texas A & M Univ., College Station, TX (United States)

    2017-06-21

    The objective of the proposed research is to study fundamental aspects of the electroweak interaction via precision measurements in beta decay to test our current understanding of fundamental particles and forces as contained in the so-called "Standard Model" of particle physics. By comparing elegant experiments to rigorous theoretical predictions, we will either confirm the Standard Model to a higher degree and rule out models which seek to extend it, or find evidence of new physics and help guide theorists in developing the New Standard Model. The use of ion and neutral atom traps at radioactive ion beam facilities has opened up a new vista in precision low-energy nuclear physics experiments. Traps provide an ideal source of decaying atoms: they can be extremely cold (~1 mK); they are compact (~1 mm^3); and perhaps most importantly, the daughter particles escape with negligible distortions to their momenta in a scattering-free, open environment. The project is taking advantage of these technologies and applying them to precision beta-decay studies at radioactive beam facilities. The program consists of two complementary efforts: 1) Ion traps are an extremely versatile tool for purifying, cooling and bunching low-energy beams of short-lived nuclei. A large-bore (210~mm) superconducting 7-Tesla solenoid is at the heart of a Penning trap system for which there is a dedicated beamline at T-REX, the upgraded radioactive beam facility at the Cyclotron Institute, Texas A&M University. In addition to providing a general-purpose decay station, the flagship program for this system is measuring the ft-values and beta-neutrino correlation parameters from isospin T=2 superallowed beta-delayed proton decays, complimenting and expanding the already strong program in fundamental interactions at the Institute. 2) A magneto-optical trap is being used at the TRIUMF Neutral Atom Trap facility to observe the (un)polarized angular distribution parameters of isotopes of potassium. We

  12. Effects of copper ions on the characteristics of egg white gel induced by strong alkali.

    Science.gov (United States)

    Shao, Yaoyao; Zhao, Yan; Xu, Mingsheng; Chen, Zhangyi; Wang, Shuzhen; Tu, Yonggang

    2017-09-01

    This study investigated the effects of copper ions on egg white (EW) gel induced by strong alkali. Changes in gel characteristics were examined through texture profile analysis, scanning electron microscopy (SEM), and chemical methods. The value of gel strength reached its maximum when 0.1% copper ions was added. However, the lowest cohesiveness values were observed at 0.1%. The springiness of gel without copper ions was significantly greater than the gel with copper ions added. SEM results illustrated that the low concentration of copper ions contributes to a dense and uniform gel network, and an open matrix was formed at 0.4%. The free and total sulphhydryl group content in the egg white protein gel significantly decreased with the increased copper. The increase of copper ions left the contents of ionic and hydrogen bonds basically unchanged, hydrophobic interaction presented an increasing trend, and the disulfide bond exhibited a completely opposite change. The change of surface hydrophobicity proved that the main binding force of copper induced gel was hydrophobic interaction. However, copper ions had no effect on the protein component of the gels. Generally, a low level of copper ions facilitates protein-protein association, which is involved in the characteristics of gels. Instead, high ionic strength had a negative effect on gels induced by strong alkali. © 2017 Poultry Science Association Inc.

  13. Hydrophobicity – Shake Flasks, Protein Folding and Drug Discovery

    Science.gov (United States)

    Sarkar, Aurijit; Kellogg, Glen E.

    2009-01-01

    Hydrophobic interactions are some of the most important interactions in nature. They are the primary driving force in a number of phenomena. This is mostly an entropic effect and can account for a number of biophysical events such as protein-protein or protein-ligand binding that are of immense importance in drug design. The earliest studies on this phenomenon can be dated back to the end of the 19th century when Meyer and Overton independently correlated the hydrophobic nature of gases to their anesthetic potency. Since then, significant progress has been made in this realm of science. This review briefly traces the history of hydrophobicity research along with the theoretical estimation of partition coefficients. Finally, the application of hydrophobicity estimation methods in the field of drug design and protein folding is discussed. PMID:19929828

  14. Study of interactions between metal ions and protein model compounds by energy decomposition analyses and the AMOEBA force field

    Science.gov (United States)

    Jing, Zhifeng; Qi, Rui; Liu, Chengwen; Ren, Pengyu

    2017-10-01

    The interactions between metal ions and proteins are ubiquitous in biology. The selective binding of metal ions has a variety of regulatory functions. Therefore, there is a need to understand the mechanism of protein-ion binding. The interactions involving metal ions are complicated in nature, where short-range charge-penetration, charge transfer, polarization, and many-body effects all contribute significantly, and a quantitative description of all these interactions is lacking. In addition, it is unclear how well current polarizable force fields can capture these energy terms and whether these polarization models are good enough to describe the many-body effects. In this work, two energy decomposition methods, absolutely localized molecular orbitals and symmetry-adapted perturbation theory, were utilized to study the interactions between Mg2+/Ca2+ and model compounds for amino acids. Comparison of individual interaction components revealed that while there are significant charge-penetration and charge-transfer effects in Ca complexes, these effects can be captured by the van der Waals (vdW) term in the AMOEBA force field. The electrostatic interaction in Mg complexes is well described by AMOEBA since the charge penetration is small, but the distance-dependent polarization energy is problematic. Many-body effects were shown to be important for protein-ion binding. In the absence of many-body effects, highly charged binding pockets will be over-stabilized, and the pockets will always favor Mg and thus lose selectivity. Therefore, many-body effects must be incorporated in the force field in order to predict the structure and energetics of metalloproteins. Also, the many-body effects of charge transfer in Ca complexes were found to be non-negligible. The absorption of charge-transfer energy into the additive vdW term was a main source of error for the AMOEBA many-body interaction energies.

  15. Fast, Statistical Model of Surface Roughness for Ion-Solid Interaction Simulations and Efficient Code Coupling

    Science.gov (United States)

    Drobny, Jon; Curreli, Davide; Ruzic, David; Lasa, Ane; Green, David; Canik, John; Younkin, Tim; Blondel, Sophie; Wirth, Brian

    2017-10-01

    Surface roughness greatly impacts material erosion, and thus plays an important role in Plasma-Surface Interactions. Developing strategies for efficiently introducing rough surfaces into ion-solid interaction codes will be an important step towards whole-device modeling of plasma devices and future fusion reactors such as ITER. Fractal TRIDYN (F-TRIDYN) is an upgraded version of the Monte Carlo, BCA program TRIDYN developed for this purpose that includes an explicit fractal model of surface roughness and extended input and output options for file-based code coupling. Code coupling with both plasma and material codes has been achieved and allows for multi-scale, whole-device modeling of plasma experiments. These code coupling results will be presented. F-TRIDYN has been further upgraded with an alternative, statistical model of surface roughness. The statistical model is significantly faster than and compares favorably to the fractal model. Additionally, the statistical model compares well to alternative computational surface roughness models and experiments. Theoretical links between the fractal and statistical models are made, and further connections to experimental measurements of surface roughness are explored. This work was supported by the PSI-SciDAC Project funded by the U.S. Department of Energy through contract DOE-DE-SC0008658.

  16. Interaction mechanism between Cd2+ ions and DNA from the kidney of the silver crucian carp.

    Science.gov (United States)

    Hong, Fashui; Wu, Cheng; Liu, Chao; Wu, Kang; Gao, Fengqing; Yang, Fan

    2006-04-01

    Cadmium is one of the most toxic heavy metals and is known to accumulate in freshwater food chains. The underlying mechanism for its genotoxicity has not been investigated for any freshwater fish. It has, however, been suggested that cadmium-induced carcinogenesis might involve either direct or indirect interaction of Cd2+ with DNA. The interaction between Cd2+ and DNA from the kidney of the silver crucian carp (Carassius auratus gibelio) in vitro and in vivo is investigated by spectrophotometric methods and agarose gel electrophoresis methods. Cd2+ could insert into DNA basepairs, bind to nucleic acid, and result in notable hypochromicities. The analysis of agarose gel electrophoresis proves that Cd2+ at different concentrations does not cause DNA cleavage in vitro; however, kidneys display the classical laddering degradation of DNA in vivo, which is the result of the promotion of deoxyribonuclease activity or inhibition of superoxide dismutase and catalyse activity and the accumulation of reactive oxygen species caused by Cd2+ ions in vivo.

  17. Hydrophobic-hydrophilic forces in protein folding.

    Science.gov (United States)

    Durell, Stewart R; Ben-Naim, Arieh

    2017-08-01

    The process of protein folding is obviously driven by forces exerted on the atoms of the amino-acid chain. These forces arise from interactions with other parts of the protein itself (direct forces), as well as from interactions with the solvent (solvent-induced forces). We present a statistical-mechanical formalism that describes both these direct and indirect, solvent-induced thermodynamic forces on groups of the protein. We focus on 2 kinds of protein groups, commonly referred to as hydrophobic and hydrophilic. Analysis of this result leads to the conclusion that the forces on hydrophilic groups are in general stronger than on hydrophobic groups. This is then tested and verified by a series of molecular dynamics simulations, examining both hydrophobic alkanes of different sizes and hydrophilic moieties represented by polar-neutral hydroxyl groups. The magnitude of the force on assemblies of hydrophilic groups is dependent on their relative orientation: with 2 to 4 times larger forces on groups that are able to form one or more direct hydrogen bonds. © 2017 Wiley Periodicals, Inc.

  18. A Novel Experimental Technique to Monitor the Time-Dependent Water and Ions Uptake when Shale Interacts with Aqueous Solutions

    Science.gov (United States)

    AL-Bazali, Talal

    2013-09-01

    The time-dependent water and ions uptake when shale interacts with aqueous solutions is quantified using a combination of immersion and gravimetric techniques. Results show that when shale interacts with salt solutions, water uptake into shale goes through three distinct stages; water movement out of shale (due to chemical osmosis), water movement into shale (due to diffusion osmosis) and stationary state (equilibrium stage). This work shows that chemical osmosis dominates water movement in early times while diffusion osmosis takes over later. In addition, it is shown that the amount of water movement due to chemical osmosis depends on the chemical potential gradient while the amount of water movement due to diffusion osmosis is highly related to the ionic concentration imbalance. In addition, the amount of ions uptake into shale at equilibrium is shown to depend on the type and concentration of salt solution. Furthermore, this work shows that potassium ion has a strengthening effect on shale while sodium and calcium ions have a weakening effect on shale. Results also show that the shale's compressive strength alteration is greatly influenced by the type and concentration of the salt solution. Furthermore, the shale's compressive strength alteration is shown to be time dependent and correlates very well with the time-dependent flux of water and ions. Finally, it is shown that chemical osmosis and diffusion osmosis take place simultaneously when shale interacts with water-based muds. The overall impact on shale stability is governed by the net water flow resulting from chemical osmosis and diffusion osmosis.

  19. Multi-charged heavy ion acceleration from the ultra-intense short pulse laser system interacting with the metal target.

    Science.gov (United States)

    Nishiuchi, M; Sakaki, H; Maeda, S; Sagisaka, A; Pirozhkov, A S; Pikuz, T; Faenov, A; Ogura, K; Kanasaki, M; Matsukawa, K; Kusumoto, T; Tao, A; Fukami, T; Esirkepov, T; Koga, J; Kiriyama, H; Okada, H; Shimomura, T; Tanoue, M; Nakai, Y; Fukuda, Y; Sakai, S; Tamura, J; Nishio, K; Sako, H; Kando, M; Yamauchi, T; Watanabe, Y; Bulanov, S V; Kondo, K

    2014-02-01

    Experimental demonstration of multi-charged heavy ion acceleration from the interaction between the ultra-intense short pulse laser system and the metal target is presented. Al ions are accelerated up to 12 MeV/u (324 MeV total energy). To our knowledge, this is far the highest energy ever reported for the case of acceleration of the heavy ions produced by the <10 J laser energy of 200 TW class Ti:sapphire laser system. Adding to that, thanks to the extraordinary high intensity laser field of ∼10(21) W cm(-2), the accelerated ions are almost fully stripped, having high charge to mass ratio (Q/M).

  20. Ion chemistry at elevated ion-molecule interaction energies in a selected ion flow-drift tube: reactions of H3O+, NO+ and O2+ with saturated aliphatic ketones.

    Science.gov (United States)

    Spesyvyi, Anatolii; Smith, David; Španěl, Patrik

    2017-12-06

    The reactions of H3O+, NO+ and O2+ ions with a homologous series of six aliphatic ketones, viz. acetone through 2-octanone, have been investigated in a helium-buffered selected ion flow-drift tube, SIFDT, in order to reveal their dependencies on ion-molecule interaction energies, Er, and to gain insight into their mechanisms. The ultimate motivation is to allow analysis and absolute quantification of trace amounts of ketones and other volatile organic compounds in air using selected ion flow-drift tube mass spectrometry, SIFDT-MS. The reactions of H3O+ with the ketone molecules, M, proceed via exothermic proton transfer producing MH+ ions, the collisional rate coefficients, kc, for which can be calculated as a function of Er and are seen to reduce by about one third over the Er range from 0.05 eV up to 0.5 eV. The rate coefficients, k, and product ion distributions for the NO+ and O2+ reactions with M had to be obtained experimentally relative to the calculated kc for the H3O+ reactions. The product ions of the NO+/ketones reactions initially proceed via the formation of excited (NO+M)* adduct ions that partially fragment, and the k reduces with Er as much as four times for the acetone reactions but remains close to their respective kc for the higher-order ketones indicating long lifetimes of the (NO+M)* ions with respect to the stabilising collision times with He atoms. The k for the O2+/ketones dissociative charge transfer reactions are observed to be greater than their calculated kc implying that long distance electron transfer occurs.

  1. The interaction between light heavy-ions and what it tells us

    Energy Technology Data Exchange (ETDEWEB)

    Brandan, M.E. [Universidad Nacional Autonoma de Mexico, Mexico City (Mexico). Inst. de Fisica; Satchler, G.R. [Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996 (United States)]|[Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6373 (United States)

    1997-06-01

    Significant progress has been achieved during the last decade in our knowledge and understanding of the optical potential between two light heavy-ions. This has mostly been a consequence of the measurement of accurate and extensive elastic differential cross sections. Some of these data, covering over eight orders of magnitude in cross section, extend to sufficiently large scattering angles that they show remarkable refractive effects which remind one of features of the scattering of alpha particles by nuclei that have been known since the work of Goldberg some twenty years ago. Refractive effects, particularly nuclear rainbows, are evident in {sup 12}C+{sup 12}C and {sup 16}O+{sup 16}O angular distributions at bombarding energies between 6 and 100 MeV per nucleon. Their angular location and cross section have led to the determination of the gross features of the local optical potentials and in many cases have removed ambiguities in the depths of the real parts of the potentials. The resulting phenomenological potentials are strongly attractive (``deep``), with relatively weak absorption, and depend upon the bombarding energy. The optical model potential for such heavy-ions is no longer simply a way to parameterize scattering data (or perhaps just one of many ways). Ambiguities have been resolved, and a good understanding of the theoretical basis of its features has been attained. The folding model is central to this understanding, coupled with increased insight into the nature of realistic effective nucleon-nucleon interactions. This Report reviews the experimental evidence, its interpretation, and what we have learnt from it. Much of the interpretation becomes especially transparent when couched in the language of semiclassical scattering theory. We summarize this language, as well as the basic features of the theory of the optical model. (orig.).

  2. High-resolution helium ion microscopy of epididymal epithelial cells and their interaction with spermatozoa.

    Science.gov (United States)

    Păunescu, Teodor G; Shum, Winnie W C; Huynh, Chuong; Lechner, Lorenz; Goetze, Bernhard; Brown, Dennis; Breton, Sylvie

    2014-10-01

    We examined the rat and mouse epididymis using helium ion microscopy (HIM), a novel imaging technology that uses a scanning beam of He(+) ions to produce nanometer resolution images of uncoated biological samples. Various tissue fixation, sectioning and dehydration methods were evaluated for their ability to preserve tissue architecture. The cauda epididymidis was luminally perfused in vivo to remove most spermatozoa and the apical surface of the epithelial lining was exposed. Fixed epididymis samples were then subjected to critical point drying (CPD) and HIM. Apical stereocilia in principal cells and smaller apical membrane extensions in clear cells were clearly distinguishable in both rat and mouse epididymis using this technology. After perfusion with an activating solution containing CPT-cAMP, a permeant analog of cAMP, clear cells exhibited an increase in the number and size of membrane ruffles or microplicae. In contrast, principal cells did not exhibit detectable structural modifications. High-resolution HIM imaging clearly showed the ultrastructure of residual sperm cells, including the presence of concentric rings on the midpiece, and of cytoplasmic droplets in some spermatozoa. Close epithelium-sperm interactions were also detected. We found a number of sperm cells whose heads were anchored within the epididymal epithelium. In certain cases, the surface of the sperm cytoplasmic droplet was covered with vesicle-like structures whose size is consistent with that of epididymosomes. In conclusion, we describe here the first application of HIM technology to the study of the structure and morphology of the rodent epididymis. HIM technology represents a major imaging breakthrough that can be successfully applied to study the epididymis and spermatozoa, with the goal of advancing our understanding of their structure and function. © The Author 2014. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All

  3. New water-soluble polyanionic dendrimers and binding to acetylcholine in water by means of contact ion-pairing interactions.

    Science.gov (United States)

    Ornelas, Cátia; Boisselier, Elodie; Martinez, Victor; Pianet, Isabelle; Ruiz Aranzaes, Jaime; Astruc, Didier

    2007-12-21

    A new water-soluble polyanionic dendrimer containing 81 benzoate termini (diameter: 11+/-1 nm from DOSY NMR spectroscopy) has been synthesized; it interacts with acetylcholine cations in water-soluble assemblies in which each carboxylate terminus reversibly forms contact ion pairs and aggregates at the tether termini, as shown by 1H NMR spectroscopy.

  4. STUDY OF ELECTRIC QUADRUPOLE INTERACTIONS OF IN-111 AND CD-111 FOLLOWING ION-IMPLANTATION OF IN-111 INTO GRAPHITE

    NARCIS (Netherlands)

    KASTELEIN, B; VANDERMAREL, HJ; ANDRIESSEN, J; POSTMA, H; PLEITER, F

    1992-01-01

    The nuclear electric quadrupole interaction of In-111 ion-implanted in hightly oriented pyrolytic graphite has been observed by means of low-temperature nuclear orientation and by means of perturbed angular correlations. From the first kind of experiment, it is concluded that a relatively large

  5. Insights into Mollusk Shell Formation: Interlamellar and Lamellar-Specific Nacre Protein Hydrogels Differ in Ion Interaction Signatures.

    Science.gov (United States)

    Pendola, Martin; Evans, John Spencer

    2018-01-08

    In the mollusk shell nacre layer, there exist hydrogelator proteomes that play important roles in the formation of the mineral phase. Two of these proteomes, the intracrystalline and the framework, reside in the interior and exterior, respectively, of the nacre tablets. To date there is no clear evidence of what distinguishes an intracrystalline protein from a framework protein regarding the nucleation process. Using Eu(III), phosphate anions, and recombinant versions of the intracrystalline protein, AP7 and the framework protein, n16.3 we probed each protein hydrogel for its interactions with these model ions. Fluorescence spectroscopy of Eu(III) interactions with both protein hydrogels revealed that r-AP7 exhibited enhanced effects on Eu(III) fluorescence compared to r-n16.3, and, 31P NMR experiments demonstrated that r-AP7 had a more significant impact on phosphate anions compared to r-n16.3. Thus, r-AP7 was found to be more of an ion "disruptor" than r-n16.3. Interestingly, these findings correlate with the particle size distributions and internal structure of the hydrogel particles themselves, suggesting that the physical and chemical properties of the hydrogels dictate hydrogel-ion interactions. In conclusion, we confirm that hydrogelator proteomes possess distinguishable ion interaction properties that may impact the nucleation processes in these regions and control the overall formation of mesoscale nacre tablets.

  6. Azimuthal anisotropy and formation of an extreme state of strongly interacting matter at the relativistic heavy-ion collider (RHIC)

    NARCIS (Netherlands)

    Okorokov, V. A.

    Experimental results obtained by studying the azimuthal anisotropy of final states in nucleus-nucleus interactions at the energies of the relativistic heavy-ion collider (RHIC) are systematized. The medium is found to exhibit a pronounced collective behavior, which is likely to be formed at an

  7. Interactions between metal ions and biogeo-surfaces in soil and water : basis for quantitative risk assessment

    NARCIS (Netherlands)

    Weng, L.P.

    2002-01-01

    To provide the basis for an improved quantitative risk assessment of heavy metals in the environment, the interactions between the metal ions and the biogeo-surfaces in soil and water were studied using both experimental and modelling approaches.

    The

  8. Cholesterol binding to ion channels

    Directory of Open Access Journals (Sweden)

    Irena eLevitan

    2014-02-01

    Full Text Available Numerous studies demonstrated that membrane cholesterol is a major regulator of ion channel function. The goal of this review is to discuss significant advances that have been recently achieved in elucidating the mechanisms responsible for cholesterol regulation of ion channels. The first major insight that comes from growing number of studies that based on the sterol specificity of cholesterol effects, show that several types of ion channels (nAChR, Kir, BK, TRPV are regulated by specific sterol-protein interactions. This conclusion is supported by demonstrating direct saturable binding of cholesterol to a bacterial Kir channel. The second major advance in the field is the identification of putative cholesterol binding sites in several types of ion channels. These include sites at locations associated with the well-known cholesterol binding motif CRAC and its reversed form CARC in nAChR, BK, and TRPV, as well as novel cholesterol binding regions in Kir channels. Notably, in the majority of these channels, cholesterol is suggested to interact mainly with hydrophobic residues in non-annular regions of the channels being embedded in between transmembrane protein helices. We also discuss how identification of putative cholesterol binding sites is an essential step to understand the mechanistic basis of cholesterol-induced channel regulation. Clearly, however, these are only the first few steps in obtaining a general understanding of cholesterol-ion channels interactions and their roles in cellular and organ functions.

  9. Tri- and tetra-substituted cyclen based lanthanide(III) ion complexes as ribonuclease mimics: a study into the effect of log Ka, hydration and hydrophobicity on phosphodiester hydrolysis of the RNA-model 2-hydroxypropyl-4-nitrophenyl phosphate (HPNP).

    Science.gov (United States)

    Fanning, Ann-Marie; Plush, Sally E; Gunnlaugsson, Thorfinnur

    2015-05-28

    A series of tetra-substituted 'pseudo' dipeptide ligands of cyclen (1,4,7,10,-tetraazacyclododecane) and a tri-substituted 3'-pyridine ligand of cyclen, and the corresponding lanthanide(III) complexes were synthesised and characterised as metallo-ribonuclease mimics. All complexes were shown to promote hydrolysis of the phosphodiester bond of 2-hydroxypropyl-4-nitrophenyl phosphate (HPNP, τ1/2 = 5.87 × 10(3) h), a well known RNA mimic. The La(III) and Eu(III) tri-substituted 3'-pyridine lanthanide(III) complexes being the most efficient in promoting such hydrolysis at pH 7.4 and at 37 °C; with τ1/2 = 1.67 h for La(III) and 1.74 h for Eu(III). The series was developed to provide the opportunity to investigate the consequences of altering the lanthanide(III) ion, coordination ability and hydrophobicity of a metallo-cavity on the rate of hydrolysis using the model phosphodiester, HPNP, at 37 °C. To further provide information on the role that the log Ka of the metal bound water plays in phosphodiester hydrolysis the protonation constants and the metal ion stability constants of both a tri and tetra-substituted 3'pyridine complex were determined. Our results highlighted several key features for the design of lanthanide(III) ribonucelase mimics; the presence of two metal bound water molecules are vital for pH dependent rate constants for Eu(III) complexes, optimal pH activity approximating physiological pH (∼7.4) may be achieved if the log Ka values for both MLOH and ML(OH)2 species occur in this region, small changes to hydrophobicity within the metallo cavity influence the rate of hydrolysis greatly and an amide adjacent to the metal ion capable of forming hydrogen bonds with the substrate is required for achieving fast hydrolysis.

  10. Thermo-super-hydrophobic effect

    Science.gov (United States)

    Floryan, Jerzy M.

    2012-02-01

    Super-hydrophobic effect involves capture of gas bubbles in pores of solid wall. These bubbles separate moving liquid from the solid surface resulting in a substantial reduction of shear drag experienced by the liquid. The super-hydrophobic effect requires presence of two phases and thus drag reduction can be accomplished only for liquids. Thermo-super-hydrophobic effect takes advantage of the localized heating to create separation bubbles and thus can work with single phase flow systems. Analysis of a simple model problem shows that this effect is very strong in the case of small Re flows such as those found in micro-channels and can reduce pressure drop down to 50% of the reference value if the heating pattern as well as the heating intensity are suitable chosen. The thermo-super-hydrophobic effect becomes marginal when Re increases above a certain critical value.

  11. Titration of hydrophobic polyelectrolytes using Monte Carlo simulations

    Science.gov (United States)

    Ulrich, Serge; Laguecir, Abohachem; Stoll, Serge

    2005-03-01

    The conformation and titration curves of weak (or annealed) hydrophobic polyelectrolytes have been examined using Monte Carlo simulations with screened Coulomb potentials in the grand canonical ensemble. The influence of the ionic concentration pH and presence of hydrophobic interactions has been systematically investigated. A large number of conformations such as extended, pearl-necklace, cigar-shape, and collapsed structures resulting from the subtle balance of short-range hydrophobic attractive interactions and long-range electrostatic repulsive interactions between the monomers have been observed. Titration curves were calculated by adjusting the pH-pK0 values (pK0 represents the intrinsic dissociation constant of an isolated monomer) and then calculating the ionization degree α of the polyelectrolyte. Important transitions related to cascades of conformational changes were observed in the titration curves, mainly at low ionic concentration and with the presence of strong hydrophobic interactions. We demonstrated that the presence of hydrophobic interactions plays an important role in the acid-base properties of a polyelectrolyte in promoting the formation of compact conformations and hence decreasing the polyelectrolyte degree of ionization for a given pH-pK0 value.

  12. Hydrophobic interactions of phenoxazine modulators with bovine ...

    Indian Academy of Sciences (India)

    The binding of phenothiazine drugs to bovine serum albumin (BSA) has been studied 1. Although most of the authors obtained total binding constants of the same order of magnitude, the number of binding sites varied considerably. It has been found 2 that the number of binding sites on BSA for promazine and ...

  13. Hydrophobic interactions of phenoxazine modulators with bovine ...

    Indian Academy of Sciences (India)

    Author Affiliations. H N Kalpana1 B C Channu1 Chhabil Dass2 P J Houghton3 K N Thimmaiah1. Department of Studies in Chemistry, University of Mysore, Manasagangotri, Mysore 570 006, India; Department of Chemistry, University of Memphis, Memphis, TN 38151, USA; Department of Molecular Pharmacology, St. Jude ...

  14. Wear resistance of hydrophobic surfaces

    Science.gov (United States)

    Martinez, MA; Abenojar, J.; Pantoja, M.; López de Armentia, S.

    2017-05-01

    Nature has been an inspiration source to develop artificial hydrophobic surfaces. During the latest years the development of hydrophobic surfaces has been widely researched due to their numerous ranges of industrial applications. Industrially the use of hydrophobic surfaces is being highly demanded. This is why many companies develop hydrophobic products to repel water, in order to be used as coatings. Moreover, these coating should have the appropriated mechanical properties and wear resistance. In this work wear study of a hydrophobic coating on glass is carried out. Hydrophobic product used was Sika Crystal Dry by Sika S.A.U. (Alcobendas, Spain). This product is currently used on car windshield. To calculate wear resistance, pin-on-disk tests were carried out in dry and water conditions. The test parameters were rate, load and sliding distance, which were fixed to 60 rpm, 5 N and 1000 m respectively. A chamois was used as pin. It allows to simulate a real use. The friction coefficient and loss weight were compared to determinate coating resistance

  15. A study of effective atomic numbers and electron densities of some vitamins for electron, H, He and C ion interactions

    Science.gov (United States)

    Büyükyıldız, M.

    2017-09-01

    The radiological properties of some vitamins such as Retinol, Beta-carotene, Riboflavin, Niacin, Niacinamide, Pantothenic acid, Pyridoxine, Pyridoxamine, Pyridoxal, Biotin, Folic acid, Ascorbic acid, Cholecalciferol, Alpha-tocopherol, Gamma-tocopherol, Phylloquinone have been investigated with respect to total electron interaction and some heavy charged particle interaction as means of effective atomic numbers (Z_{eff}) and electron densities (N_{eff}) for the first time. Calculations were performed for total electron interaction and heavy ions such as H, He and C ion interactions in the energy region 10keV-10MeV by using a logarithmic interpolation method. Variations in Z_{eff}'s and N_{eff}'s of given vitamins have been studied according to the energy of electron or heavy charged particles, and significant variations have been observed for all types of interaction in the given energy region. The maximum values of Z_{eff} have been found in the different energy regions for different interactions remarkably and variations in N_{eff} seem approximately to be the same with variation in Z_{eff} for the given vitamins as expected. Z_{eff} values of some vitamins were plotted together and compared with each other for electron, H, He and C interactions and the ratios of Z_{eff}/ have been changed in the range of 0.25-0.36, 0.20-0.36, 0.22-0.35 and 0.20-0.35 for electron, H, He and C interactions, respectively.

  16. Ion Acceleration from the Interaction of Ultra-Intense Lasers with Solid Foils

    Energy Technology Data Exchange (ETDEWEB)

    Allen, Matthew M. [Univ. of California, Berkeley, CA (United States)

    2004-01-01

    The discovery that ultra-intense laser pulses (I > 1018 W/cm2) can produce short pulse, high energy proton beams has renewed interest in the fundamental mechanisms that govern particle acceleration from laser-solid interactions. Experiments have shown that protons present as hydrocarbon contaminants on laser targets can be accelerated up to energies > 50 MeV. Different theoretical models that explain the observed results have been proposed. One model describes a front-surface acceleration mechanism based on the ponderomotive potential of the laser pulse. At high intensities (I > 1018 W/cm2), the quiver energy of an electron oscillating in the electric field of the laser pulse exceeds the electron rest mass, requiring the consideration of relativistic effects. The relativistically correct ponderomotive potential is given by Up = ([1 + Iλ2/1.3 x 1018]1/2 - 1) m{sub o}c2, where Iλ2 is the irradiance in W μm2/cm2 and moc2 is the electron rest mass. At laser irradiance of Iλ2 ~ 1020 W μm2/cm2, the ponderomotive potential can be of order several MeV. A few recent experiments--discussed in Chapter 3 of this thesis--consider this ponderomotive potential sufficiently strong to accelerate protons from the front surface of the target to energies up to tens of MeV. Another model, known as Target Normal Sheath Acceleration (TNSA), describes the mechanism as an electrostatic sheath on the back surface of the laser target. According to the TNSA model, relativistic hot electrons created at the laser-solid interaction penetrate the foil where a few escape to infinity. The remaining hot electrons are retained by the target potential and establish an electrostatic sheath on the back surface of the target. In this thesis we present several experiments that study the accelerated ions by

  17. 5f state interaction with inner coordination sphere ligands: einsteinium 3+ ion fluorescence in aqueous and organic phases

    Energy Technology Data Exchange (ETDEWEB)

    Beitz, J.V.; Wester, D.W.; Williams, C.W.

    1983-01-01

    The interaction between 5f electron states of einsteinium 3+ ion and coordinated ligands in solution has been probed using laser-induced fluorescence. Aquo einsteinium 3+ ion was observed to fluoresce from its first excited J = 5 state in a broad-band peaking at 9260 wavenumbers. The observed fluorescence lifetimes were 1.05 microseconds and 2.78 microseconds in H/sub 2/O and D/sub 2/O (99+ % D atom), respectively. The non-radiative decay rates derived from the lifetime data are compared with previously reported data for Cm, Sm, Eu, Tb, and Dy aquo 3+ ions. The 5f actinide states exhibit substantially greater non-radiative decay rates than do lanthanide 4f states of similar energy gap. This provides evidence that actinide 5f electrons interact more strongly with their inner coordination sphere than do lanthanide ion 4f electrons. The fluorescence lifetime of einsteinium 3+ ion complexed with 1 formal di(2-ethylhexyl)orthophosphoric acid in h-heptane was 2.34 microseconds. 3 figures, 1 table.

  18. Thermodynamics of protein denaturation at temperatures over 100 °C: CutA1 mutant proteins substituted with hydrophobic and charged residues.

    Science.gov (United States)

    Matsuura, Yoshinori; Takehira, Michiyo; Joti, Yasumasa; Ogasahara, Kyoko; Tanaka, Tomoyuki; Ono, Naoko; Kunishima, Naoki; Yutani, Katsuhide

    2015-10-26

    Although the thermodynamics of protein denaturation at temperatures over 100 °C is essential for the rational design of highly stable proteins, it is not understood well because of the associated technical difficulties. We designed certain hydrophobic mutant proteins of CutA1 from Escherichia coli, which have denaturation temperatures (Td) ranging from 101 to 113 °C and show a reversible heat denaturation. Using a hydrophobic mutant as a template, we successfully designed a hyperthermostable mutant protein (Td = 137 °C) by substituting six residues with charged ones. Thermodynamic analyses of these mutant proteins indicated that the hydrophobic mutants were stabilized by the accumulation of denaturation enthalpy (ΔH) with no entropic gain from hydrophobic solvation around 100 °C, and that the stabilization due to salt bridges resulted from both the increase in ΔH from ion-ion interactions and the entropic effect of the electrostatic solvation over 113 °C. This is the first experimental evidence that has successfully overcome the typical technical difficulties.

  19. Latitudinal dependence of nonlinear interaction between electromagnetic ion cyclotron wave and radiation belt relativistic electrons

    Science.gov (United States)

    Su, Zhenpeng; Zhu, Hui; Xiao, Fuliang; Zheng, Huinan; Shen, Chao; Wang, Yuming; Wang, Shui

    2013-06-01

    Electromagnetic ion cyclotron (EMIC) waves are long suggested to account for the rapid loss of radiation belt relativistic electrons. Here we perform both theoretical analysis and numerical simulation to comprehensively investigate the nonlinear interaction between EMIC wave and relativistic electrons. In particular, we emphasize the dependence of nonlinear processes on the electron initial latitude. The nonlinear phase trapping yields negative equatorial pitch angle transport, with efficiency varying over the electron initial latitude, implying that it can increase the loss rate predicted by quasilinear theory. The nonlinear channel effect phase bunching produces positive equatorial pitch angle transport, less dependent on the electron initial latitude, suggesting that it can decrease the loss rate predicted by quasilinear theory. The nonlinear cluster effect phase bunching alternately causes positive and negative equatorial pitch angle transport, quasi-periodically dependent on the electron initial latitude, suggesting that it can either decrease or increase the loss rate predicted by the quasilinear theory. Such latitudinal dependence of nonlinear processes should be taken into account in the evaluation of radiation belt electron loss rate driven by EMIC waves.

  20. Interaction of ions, atoms, and small molecules with quantized vortex lines in superfluid (4)He.

    Science.gov (United States)

    Mateo, David; Eloranta, Jussi; Williams, Gary A

    2015-02-14

    The interaction of a number of impurities (H2, Ag, Cu, Ag2, Cu2, Li, He3 (+), He(*) ((3)S), He2 (∗) ((3)Σu), and e(-)) with quantized rectilinear vortex lines in superfluid (4)He is calculated by using the Orsay-Trento density functional theory (DFT) method at 0 K. The Donnelly-Parks (DP) potential function binding ions to the vortex is combined with DFT data, yielding the impurity radius as well as the vortex line core parameter. The vortex core parameter at 0 K (0.74 Å) obtained either directly from the vortex line geometry or through the DP potential fitting is smaller than previously suggested but is compatible with the value obtained from re-analysis of the Rayfield-Reif experiment. All of the impurities have significantly higher binding energies to vortex lines below 1 K than the available thermal energy, where the thermally assisted escape process becomes exponentially negligible. Even at higher temperatures 1.5-2.0 K, the trapping times for larger metal clusters are sufficiently long that the previously observed metal nanowire assembly in superfluid helium can take place at vortex lines. The binding energy of the electron bubble is predicted to decrease as a function of both temperature and pressure, which allows adjusting the trap depth for either permanent trapping or to allow thermally assisted escape. Finally, a new scheme for determining the trapping of impurities on vortex lines by optical absorption spectroscopy is outlined and demonstrated for He(*).

  1. Silkworm eggs: An ideal model for studying the biological effects of low energy Ar + ion interaction in animals

    Science.gov (United States)

    Ling, Lin; Liu, Xuelan; Xu, Jiaping; You, Zhengying; Zhou, Jingbo

    2011-09-01

    The object of the current work was to study low energy Ar + ion beam interactions with silkworm eggs and thus provide further understanding of the mechanisms involved in ion bombardment-induced direct gene transfer into silkworm eggs. In this paper, using low-energy Ar + ion beam bombardment combined with piggyBac transposon, we developed a novel method to induce gene transfer in silkworm. Using bombardment conditions optimized for egg-incubation (25 keV with ion fluences of 800 × 2.6 × 10 15 ions/cm 2 in dry state under vacuum), vector pBac{3 × P3-EGFPaf} and helper plasmid pHA3pig were successfully transferred into the silkworm eggs. Our results obtained from by PCR assay and genomic Southern blotting analysis of the G1 generations provide evidence that low-energy ion beam can generate some craters that play a role in acting as pathways of exogenous DNA molecules into silkworm eggs.

  2. Hydrogels with smart systems for delivery of hydrophobic drugs.

    Science.gov (United States)

    Gu, Dunyin; O'Connor, Andrea J; G H Qiao, Greg; Ladewig, Katharina

    2017-07-01

    Smart hydrogel systems present opportunities to not only provide hydrophobic molecule encapsulation capability but to also respond to specific delivery routes. Areas covered: An overview of the design principles, preparation methods and applications of hydrogel systems for delivery of hydrophobic drugs is given. It begins with a summary of the advantages of hydrogels as delivery vehicles over other approaches, particularly macromolecular nanocarriers, before proceeding to address the design and preparation strategies and chemistry involved, with a particular focus on the introduction of hydrophobic domains into (naturally) hydrophilic hydrogels. Finally, the applications in different delivery routes are discussed. Expert opinion: Modifications to conventional hydrogels can endow them with the capability to carry hydrophobic drugs but other functions as well, such as the improved mechanical stability, which is important for long-term in vivo residence and/or self-healing properties useful for injectable delivery pathways. These modifications harness hydrophobic-hydrophobic forces, physical interactions and inclusion complexes. The lack of in-depth understanding of these interactions, currently limits more delicate and application-oriented designs. Increased efforts are needed in (i) understanding the interplay of gel formation and simultaneous drug loading; (ii) improving hydrogel systems with respect to their biosafety; and (iii) control over release mechanism and profile.

  3. Aggregation of amyloidogenic peptides near hydrophobic and hydrophilic surfaces.

    Science.gov (United States)

    Brovchenko, Ivan; Singh, Gurpreet; Winter, Roland

    2009-07-21

    The general effect of surface hydrophobicity/hydrophilicity on the aggregation of peptides is studied by simulations of oversaturated aqueous solutions of hydrophobic and hydrophilic amyloidogenic peptides. Peptide aggregation was studied in bulk solution, in solutions confined between hydrophobic boundaries (smooth planar paraffin-like surfaces and liquid-vapor interfaces) and in solutions confined between hydrophilic surfaces (smooth planar silica-like surfaces). Aggregation of hydrophobic peptides strongly enhances due to the confinement between hydrophobic surfaces with all peptides adsorbed at the boundaries and aligned predominantly parallel to them. In the other three cases considered, the peptides are repelled from the walls and do not reveal orientational ordering with respect to the surface. The degree of peptide aggregation in these cases is only slightly affected by the confinement (it is enhanced for hydrophobic peptides and decreased for hydrophilic peptides). Our results show that even a single environmental factor such as water-mediated peptide-surface interaction has a drastic effect on the degree and character of peptide aggregation. A wide diversity of possible scenarios can be expected when specific peptide-surface interactions are additionally taken into account.

  4. Isolation and kinetic characterisation of hydrophobically distinct populations of form I Rubisco

    Science.gov (United States)

    2014-01-01

    Background Rubisco (Ribulose-1,5-bisphosphate carboxylase/oxygenase) is a Calvin Cycle enzyme involved in CO2 assimilation. It is thought to be a major cause of photosynthetic inefficiency, suffering from both a slow catalytic rate and lack of specificity due to a competing reaction with oxygen. Revealing and understanding the engineering rules that dictate Rubisco’s activity could have a significant impact on photosynthetic efficiency and crop yield. Results This paper describes the purification and characterisation of a number of hydrophobically distinct populations of Rubisco from both Spinacia oleracea and Brassica oleracea extracts. The populations were obtained using a novel and rapid purification protocol that employs hydrophobic interaction chromatography (HIC) as a form I Rubisco enrichment procedure, resulting in distinct Rubisco populations of expected enzymatic activities, high purities and integrity. Conclusions We demonstrate here that HIC can be employed to isolate form I Rubisco with purities and activities comparable to those obtained via ion exchange chromatography (IEC). Interestingly, and in contrast to other published purification methods, HIC resulted in the isolation of a number of hydrophobically distinct Rubisco populations. Our findings reveal a so far unaccounted diversity in the hydrophobic properties within form 1 Rubisco. By employing HIC to isolate and characterise Spinacia oleracea and Brassica oleracea, we show that the presence of these distinct Rubisco populations is not species specific, and we report for the first time the kinetic properties of Rubisco from Brassica oleracea extracts. These observations may aid future studies concerning Rubisco’s structural and functional properties. PMID:24987448

  5. Partitioning of dissolved organic matter-bound mercury between a hydrophobic surface and polysulfide-rubber polymer

    Science.gov (United States)

    Kim, Eun-Ah

    2011-01-01

    This study investigated the role of dissolved organic matter on mercury partitioning between a hydrophobic surface (polyethylene, PE) and a reduced sulfur-rich surface (polysulfide rubber, PSR). Comparative sorption studies employed polyethylene and polyethylene coated with PSR for reactions with DOM-bound mercuric ions. These studies revealed that PSR enhanced the Hg-DOM removal from water when DOM was Suwannee River natural organic matter (NOM), fulvic acid (FA), or humic acid (HA), while the same amount of 1,3-propanedithiol-bound mercuric ion was removed by both PE and PSR-PE. The differences for Hg-DOM removal efficiencies between PE and PSR-PE varied depending on which DOM was bound to mercuric ion as suggested by the PE/water and PSR-PE/water partition coefficients for mercury. The surface concentrations of mercury on PE and PSR-PE with the same DOM measured by x-ray – photoelectron spectroscopy were similar, which indicated the comparable amounts of immobilized mercury on PE and PSR-PE being exposed to the aqueous phase. With these observations, two major pathways for the immobilization reactions between PSR-PE and Hg- DOM were examined: 1) adsorption of Hg-DOM on PE by hydrophobic interactions between DOM and PE, and 2) addition reaction of Hg-DOM onto PSR by a complexation reaction between Hg and PSR. The percent contribution of each pathway was derived from a mass balance and the ratios among aqueous mercury, PE-bound Hg-DOM, and PSR-bound Hg-DOM concentrations. The results indicate strong binding of mercuric ion with both dissolved organic matter and PSR polymer. The FT-IR examination of Hg-preloaded-PSR-PEs after the reaction with DOM corroborated a strong interaction between mercuric ion and 1,3-propanedithiol compared to Hg-HA, Hg-FA, or Hg-NOM interactions. PMID:21872900

  6. Influence of Hydrophobicity on Polyelectrolyte Complexation

    Energy Technology Data Exchange (ETDEWEB)

    Sadman, Kazi [Department; amp, Engineering, Northwestern University, Evanston, Illinois 60208, United States; Wang, Qifeng [Department; amp, Engineering, Northwestern University, Evanston, Illinois 60208, United States; Chen, Yaoyao [Department; amp, Engineering, Northwestern University, Evanston, Illinois 60208, United States; Keshavarz, Bavand [Department; Jiang, Zhang [X-ray; Shull, Kenneth R. [Department; amp, Engineering, Northwestern University, Evanston, Illinois 60208, United States

    2017-11-16

    Polyelectrolyte complexes are a fascinating class of soft materials that can span the full spectrum of mechanical properties from low viscosity fluids to glassy solids. This spectrum can be accessed by modulating the extent of electrostatic association in these complexes. However, to realize the full potential of polyelectrolyte complexes as functional materials their molecular level details need to be clearly correlated with their mechanical response. The present work demonstrates that by making simple amendments to the chain architecture it is possible to affect the salt responsiveness of polyelectrolyte complexes in a systematic manner. This is achieved by quaternizing poly(4-vinylpyridine) (QVP) with methyl, ethyl and propyl substituents– thereby increasing the hydrophobicity with increasing side chain length– and complexing them with a common anionic polyelectrolyte, poly(styrene sulfonate). The mechanical 1 ACS Paragon Plus Environment behavior of these complexes is compared to the more hydrophilic system of poly(styrene sulfonate) and poly(diallyldimethylammonium) by quantifying the swelling behavior in response to salt stimuli. More hydrophobic complexes are found to be more resistant to doping by salt, yet the mechanical properties of the complex remain contingent on the overall swelling ratio of the complex itself, following near universal swelling-modulus master curves that are quantified in this work. The rheological behavior of QVP complex coacervates are found to be approximately the same, only requiring higher salt concentrations to overcome strong hydrophobic interactions, demonstrating that hydrophobicity can be used as an important parameter for tuning the stability of polyelectrolyte complexes in general, while still preserving the ability to be processed “saloplastically”.

  7. Collisionless electrostatic shock formation and ion acceleration in intense laser interactions with near critical density plasmas

    CERN Document Server

    Liu, M; Li, Y T; Yuan, D W; Chen, M; Mulser, P; Sheng, Z M; Murakami, M; Yu, L L; Zheng, X L; Zhang, J

    2016-01-01

    Laser-driven collisonless electrostatic shock formation and the subsequent ion acceleration have been studied in near critical density plasmas. Particle-in-cell simulations show that both the speed of laser-driven collisionless electrostatic shock and the energies of shock-accelerated ions can be greatly enhanced due to fast laser propagation in near critical density plasmas. However, a response time longer than tens of laser wave cycles is required before the shock formation in a near critical density plasma, in contrast to the quick shock formation in a highly overdense target. More important, we find that some ions can be reflected by the collisionless shock even if the electrostatic potential jump across the shock is smaller than the ion kinetic energy in the shock frame, which seems against the conventional ion-reflection condition. These anomalous ion reflections are attributed to the strongly time-oscillating electric field accompanying laser-driven collisionless shock in a near critical density plasma...

  8. Crystal lattice properties fully determine short-range interaction parameters for alkali and halide ions

    OpenAIRE

    Mao, Albert H.; Pappu, Rohit V.

    2012-01-01

    Accurate models of alkali and halide ions in aqueous solution are necessary for computer simulations of a broad variety of systems. Previous efforts to develop ion force fields have generally focused on reproducing experimental measurements of aqueous solution properties such as hydration free energies and ion-water distribution functions. This dependency limits transferability of the resulting parameters because of the variety and known limitations of water models. We present a solvent-indep...

  9. Influence of hydrophobic modification in alginate-based hydrogels for biomedical applications

    Science.gov (United States)

    Choudhary, Soumitra

    Alginate has been exploited commercially for decades in foods, textiles, paper, pharmaceutical industries, and also as a detoxifier for removing heavy metals. Alginate is also popular in cell encapsulation because of its relatively mild gelation protocol and simple chemistry with which biological active entities can be immobilized. Surface modification of alginate gels has been explored to induce desired cell interactions with the gel matrix. These modifications alter the bulk properties, which strongly determine on how cells feel and response to the three-dimensional microenvironment. However, there is a need to develop strategies to engineer functionalities into bulk alginate hydrogels that not only preserve their inherent qualities but are also less toxic. In this thesis, our main focus was to optimize the mechanical properties of alginate-based hydrogels, and by doing so control the performance of the biomaterials. In the first scheme, we used alginate and hydrophobically modified ethyl hydroxy ethyl cellulose as components in interpenetrating polymer network (IPN) gels. The second network was used to control gelation time and rheological properties. We believe these experiments also may provide insight into the mechanical and structural properties of more complex biopolymer gels and naturally-occurring IPNs. Next, we worked on incorporating a hydrophobic moiety directly into the alginate chain, resulting in materials for extended release of hydrophobic drugs. We successfully synthesized hydrophobically modified alginate (HMA) by attaching octylamine groups onto the alginate backbone by standard carbodiimide based amide coupling reaction. Solubility of several model hydrophobic drugs in dilute HMA solutions was found to be increased by more than an order of magnitude. HMA hydrogels, prepared by crosslinking the alginate chains with calcium ions, were found to exhibit excellent mechanical properties (modulus ˜100 kPa) with release extended upto 5 days. Ability

  10. Changing nanoslot ion flux with a dynamic nanocolloid ion-selective filter: secondary overlimiting currents due to nanocolloid-nanoslot interaction.

    Science.gov (United States)

    Yossifon, Gilad; Chang, Hsueh-Chia

    2010-06-01

    Nanocolloids trapped at the depleted side (anodic) of a fluidic nanoslot entrance are shown to sensitively regulate dc ion transport through the nanoslot, such that a second limiting-overlimiting transition occurs in its nonlinear current-voltage characteristics. The nanocolloids, brought to the entrance by electro-osmosis, are not stationary but are confined to closed circular and toroidal streamlines, driven by a back-pressure corner vortex and an orthogonal electroconvection vortex instability. The transition from the corner vortex to a complex torus with both vortical motions coincides with the first overlimiting transition, while electrostatic interaction of nanocolloids in these vortices with the nanoslot entrance drives the second limiting transition.

  11. Magnetic exchange interaction between rare-earth and Mn ions in multiferroic hexagonal manganites

    Energy Technology Data Exchange (ETDEWEB)

    Talbayev, Diyar [Los Alamos National Laboratory; Trugman, Stuart A [Los Alamos National Laboratory; Taylor, Antoinette J [Los Alamos National Laboratory; Averitt, Richard D [Los Alamos National Laboratory; Namjung, Hur [INHA UNIV; Andrew, Laforge D [UCSD; Dimitri, Basov N [UCSD

    2008-01-01

    The authors report a study of magnetic dynamics in multiferroic hexagonal manganite HoMnO{sub 3} by far-infrared spectroscopy. Low-temperature magnetic excitation spectrum of HoMnO{sub 3} consists of magnetic-dipole transitions of Ho ions within the crystal-field split J = 8 manifold and of the triangular antiferromagnetic resonance of Mn ions. They determine the effective spin Hamiltonian for the Ho ion ground state. The magnetic-field splitting of the Mn antiferromagnetic resonance allows us to measure the magnetic exchange coupling between the rare-earth and Mn ions.

  12. Comprehensive analysis of pharmaceutical products using simultaneous mixed-mode (ion-exchange/reversed-phase) and hydrophilic interaction liquid chromatography.

    Science.gov (United States)

    Kazarian, Artaches A; Nesterenko, Pavel N; Soisungnoen, Phimpha; Burakham, Rodjana; Srijaranai, Supalax; Paull, Brett

    2014-08-01

    Liquid chromatographic assays were developed using a mixed-mode column coupled in sequence with a hydrophilic interaction liquid chromatography column to allow the simultaneous comprehensive analysis of inorganic/organic anions and cations, active pharmaceutical ingredients, and excipients (carbohydrates). The approach utilized dual sample injection and valve-mediated column switching and was based upon a single high-performance liquid chromatography gradient pump. The separation consisted of three distinct sequential separation mechanisms, namely, (i) ion-exchange, (ii) mixed-mode interactions under an applied dual gradient (reversed-phase/ion-exchange), and (iii) hydrophilic interaction chromatography. Upon first injection, the Scherzo SS C18 column (Imtakt) provided resolution of inorganic anions and cations under isocratic conditions, followed by a dual organic/salt gradient to elute active pharmaceutical ingredients and their respective organic counterions and potential degradants. At the top of the mixed-mode gradient (high acetonitrile content), the mobile phase flow was switched to a preconditioned hydrophilic interaction liquid chromatography column, and the standard/sample was reinjected for the separation of hydrophilic carbohydrates, some of which are commonly known excipients in drug formulations. The approach afforded reproducible separation and resolution of up to 23 chemically diverse solutes in a single run. The method was applied to investigate the composition of commercial cough syrups (Robitussin®), allowing resolution and determination of inorganic ions, active pharmaceutical ingredients, excipients, and numerous well-resolved unknown peaks. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Probing nucleic acid-ion interactions with buffer exchange-atomic emission spectroscopy.

    Science.gov (United States)

    Greenfeld, Max; Herschlag, Daniel

    2009-01-01

    The ion atmosphere of nucleic acids directly affects measured biochemical and biophysical properties. However, study of the ion atmosphere is difficult due to its diffuse and dynamic nature. Standard techniques available have significant limitations in sensitivity, specificity, and directness of the assays. Buffer exchange-atomic emission spectroscopy (BE-AES) was developed to overcome many of the limitations of previously available techniques. This technique can provide a complete accounting of all ions constituting the ionic atmosphere of a nucleic acid at thermodynamic equilibrium. Although initially developed for the study of the ion atmosphere of nucleic acids, BE-AES has also been applied to study site-bound ions in RNA and protein. Copyright © 2009 Elsevier Inc. All rights reserved.

  14. The acid-catalyzed interaction of melanin with nitrite ions. An EPR investigation

    Directory of Open Access Journals (Sweden)

    Matuszak Zenon

    2015-07-01

    Full Text Available The interaction of synthetic dihydroxyphenylalanine (DOPA melanin (DM with nitrite ions, NO2−, in the pH 3.6–7.0 range, has been investigated using electron paramagnetic resonance (EPR. We found that especially at pH <5.5 (from ca. 5.5 to 3.6 the reaction of DM with nitrite generated large quantities of new melanin radicals, which implies the involvement of nitrous acid, HNO2, in the radical formation process. Measurements carried out at constant pH of 3.6 showed that the melanin signal increased together with nitrite concentration, reaching a plateau level which was more than fourfold larger compared to the initial signal amplitude observed in a nitrite-free buffer of the same pH. The effects of nitrite and DM concentrations on the melanin-free radical content were also investigated. It is proposed that the radicals are generated by one electron oxidation of melanin ortho-hydroquinone groups to ortho-semiquinones by HNO2 or related nitrogen oxides such as NO2• radicals. The possible involvement of nitric oxide (•NO and peroxynitrite (ONOO− in DM oxidation was also examined. In air-free solutions, nitric oxide per se did not generate melanin radicals; however, in the presence of oxygen a marked increase in the melanin EPR signal intensity was observed. This result is interpreted in terms of the generation of radicals via the oxidation of DM by peroxynitrite. Our findings suggest that melanin can function as a natural scavenger of nitrous acid and some nitrous acid-derived species. This property may be relevant to physiological functions of melanin pigments in vivo.

  15. Systematic comparison of barriers for heavy-ion fusion calculated on the basis of the double-folding model by employing two versions of nucleon–nucleon interaction

    Energy Technology Data Exchange (ETDEWEB)

    Gontchar, I. I. [Omsk State Transport University (Russian Federation); Chushnyakova, M. V., E-mail: maria.chushnyakova@gmail.com [Omsk State Technical University (Russian Federation)

    2016-07-15

    A systematic calculation of barriers for heavy-ion fusion was performed on the basis of the double-folding model by employing two versions of an effective nucleon–nucleon interaction: M3Y interaction and Migdal interaction. The results of calculations by the Hartree–Fockmethod with the SKX coefficients were taken for nuclear densities. The calculations reveal that the fusion barrier is higher in the case of employing theMigdal interaction than in the case of employing the Ðœ3Y interaction. In view of this, the use of the Migdal interaction in describing heavy-ion fusion is questionable.

  16. Interaction between the exchanged Mn2+ and Yb3+ ions confined in zeolite-Y and their luminescence behaviours

    Science.gov (United States)

    Ye, Shi; Sun, Jiayi; Yi, Xiong; Wang, Yonggang; Zhang, Qinyuan

    2017-01-01

    Luminescent zeolites exchanged with two distinct and interacted emissive ions are vital but less-studied for the potential applications in white light emitting diodes, solar cells, optical codes, biomedicine and so on. Typical transition metal ion Mn2+ and lanthanide ion Yb3+ are adopted as a case study via their characteristic transitions and the interaction between them. The option is considered with that the former with d-d transition has a large gap between the first excited state 4T1 and the ground state 6A1 (normally >17,000 cm−1) while the latter with f-f transition has no metastable excited state above 10,000 cm−1, which requires the vicinity of these two ions for energy transfer. The results of various characterizations, including BET measurement, photoluminescence spectroscopy, solid-state NMR, and X-ray absorption spectroscopy, etc., show that Yb3+ would preferably enter into the zeolite-Y pores and introduction of Mn2+ would cause aggregation of each other. Herein, cation-cation repulsion may play a significant role for the high valence of Mn2+ and Yb3+ when exchanging the original cations with +1 valence. Energy transfer phenomena between Mn2+ and Yb3+ occur only at elevated contents in the confined pores of zeolite. The research would benefit the design of zeolite composite opto-functional materials. PMID:28393920

  17. Interaction between the exchanged Mn2+ and Yb3+ ions confined in zeolite-Y and their luminescence behaviours

    Science.gov (United States)

    Ye, Shi; Sun, Jiayi; Yi, Xiong; Wang, Yonggang; Zhang, Qinyuan

    2017-04-01

    Luminescent zeolites exchanged with two distinct and interacted emissive ions are vital but less-studied for the potential applications in white light emitting diodes, solar cells, optical codes, biomedicine and so on. Typical transition metal ion Mn2+ and lanthanide ion Yb3+ are adopted as a case study via their characteristic transitions and the interaction between them. The option is considered with that the former with d-d transition has a large gap between the first excited state 4T1 and the ground state 6A1 (normally >17,000 cm-1) while the latter with f-f transition has no metastable excited state above 10,000 cm-1, which requires the vicinity of these two ions for energy transfer. The results of various characterizations, including BET measurement, photoluminescence spectroscopy, solid-state NMR, and X-ray absorption spectroscopy, etc., show that Yb3+ would preferably enter into the zeolite-Y pores and introduction of Mn2+ would cause aggregation of each other. Herein, cation-cation repulsion may play a significant role for the high valence of Mn2+ and Yb3+ when exchanging the original cations with +1 valence. Energy transfer phenomena between Mn2+ and Yb3+ occur only at elevated contents in the confined pores of zeolite. The research would benefit the design of zeolite composite opto-functional materials.

  18. Fluoroalkyl and Alkyl Chains Have Similar Hydrophobicities in Binding to the “Hydrophobic Wall” of Carbonic Anhydrase

    Energy Technology Data Exchange (ETDEWEB)

    J Mecinovic; P Snyder; K Mirica; S Bai; E Mack; R Kwant; D Moustakas; A Heroux; G Whitesides

    2011-12-31

    entropic contributions to the hydrophobic effect in this representative system of protein and ligand: hydrophobic interactions, here, seem to comprise approximately equal contributions from enthalpy (plausibly from strengthening networks of hydrogen bonds among molecules of water) and entropy (from release of water from configurationally restricted positions).

  19. Aspheric Solute Ions Modulate Gold Nanoparticle Interactions in an Aqueous Solution: An Optimal Way To Reversibly Concentrate Functionalized Nanoparticles.

    Science.gov (United States)

    Villarreal, Oscar D; Chen, Liao Y; Whetten, Robert L; Demeler, Borries

    2015-12-17

    Nanometer-sized gold particles (AuNPs) are of peculiar interest because their behaviors in an aqueous solution are sensitive to changes in environmental factors including the size and shape of the solute ions. In order to determine these important characteristics, we performed all-atom molecular dynamics simulations on the icosahedral Au144 nanoparticles each coated with a homogeneous set of 60 thiolates (4-mercaptobenzoate, pMBA) in eight aqueous solutions having ions of varying sizes and shapes (Na(+), K(+), tetramethylamonium cation TMA(+), tris-ammonium cation TRS(+), Cl(-), and OH(-)). For each solution, we computed the reversible work (potential of mean of force) to bring two nanoparticles together as a function of their separation distance. We found that the behavior of pMBA protected Au144 nanoparticles can be readily modulated by tuning their aqueous environmental factors (pH and solute ion combinations). We examined the atomistic details on how the sizes and shapes of solute ions quantitatively factor in the definitive characteristics of nanoparticle-environment and nanoparticle-nanoparticle interactions. We predict that tuning the concentrations of nonspherical composite ions such as TRS(+) in an aqueous solution of AuNPs be an effective means to modulate the aggregation propensity desired in biomedical and other applications of small charged nanoparticles.

  20. Interactions of anti-Parkinson drug benserazide with Zn(II), Cu(II), Fe(II) ions.

    Science.gov (United States)

    Szyrwiel, Lukasz; Pap, József S; Malinka, Wieslaw; Szewczuk, Zbigniew; Kotynia, Aleksandra; Brasun, Justyna

    2013-03-25

    One of the treatments of Parkinson disease is based on increasing the brain dopamine level by L-DOPA (LD) applications. To prevent the peripheral degradation of levodopa, another drug, benserazide is applied. On the other hand, during this neurodegenerative disease changes in the homeostasis of metals are observed and the increasing brain zinc levels are postulated to have therapeutic effects. Here we present studies on interactions of Zn(II), Cu(II), Fe(II) ions with benserazide and with benserazide/levodopa in ternary system. By applying mass spectrometry and UV-vis methods we describe the interactions between selected metal ions and the drug additives in the investigated systems. The results show forming of equimolar complexes in the binary and ternary systems. Copyright © 2012 Elsevier B.V. All rights reserved.

  1. Interaction of clozapine and its nitrenium ion with rat D2 dopamine receptors: in vitro binding and computational study

    Science.gov (United States)

    Dilly, Sébastien; Liégeois, Jean-François

    2011-02-01

    The interaction of diazepine analogues like clozapine or olanzapine with D2 receptor was greatly affected by a mixture of HRP/H2O2 known to induce the formation of nitrenium ion. Unlike diazepine derivatives, the oxidative mixture had low impact on the affinity of oxa- and thiazepine derivatives such as loxapine, clothiapine or JL13 for the D2 receptor. Molecular docking simulations revealed a huge difference between the mode of interaction of clozapine nitrenium ion and the parent drug. Electronic and geometric changes of the tricyclic ring system caused by the oxidation appeared to prevent the compound finding the correct binding mode and could therefore explain the difference observed in binding affinities.

  2. Comparative study of collision cross-sections and ion transport coefficients from several He+/He interaction potentials

    Science.gov (United States)

    Chicheportiche, A.; Lepetit, B.; Benhenni, M.; Gadea, F. X.; Yousfi, M.

    2013-03-01

    Ion-atom collision cross-sections and transport coefficients are computed from several He2+ interaction potentials. Differential and integral momentum transfer cross-sections are obtained with a close-coupling quantum method using several literature interaction potentials. These collision cross-sections are used in an optimized Monte Carlo code to calculate the ion transport coefficients over a wide range of reduced electric field considering first the scattering anisotropy by using a differential cross-section and then an isotropic scattering approximation based on momentum transfer cross-section. Reduced mobilities are compared with available experimental data. This allows us to segregate accurate potentials which provide reduced mobilities falling within experimental error bars.

  3. Effects of vortex-vortex interactions on ion-track pinning in high T{sub c} superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Gray, K.E.; Steel, D.G.; Hettinger, J.D. [and others

    1996-12-31

    Many superconductor applications rely on the ability to pin vortex lattices. This ability depends on structural defects to pin individual vortices, but vortex-vortex interactions often play an important role in pinning the other vortices. Experimental progress on this complex problem can be made by introducing random arrays of well-defined pinning centers and studying the flux dynamics for a range of vortex densities (i.e., fields). Results of such studies in epitaxial Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub y} films containing ion tracks show the importance of vortex-vortex interactions. As an example, the effective pinning field of the defects rises to many times the ion-dose field for temperatures well below {Tc}.

  4. Closed form S matrix in terms of matter distributions and nucleon-nucleon interaction for heavy ion scattering

    Energy Technology Data Exchange (ETDEWEB)

    Gambhir, Y.K.; Shastry, C.S.

    1984-10-01

    We derive an approximate analytical expression for the S matrix in terms of the parameters of the nuclear matter distributions and nucleon-nucleon interaction in the framework of folding model for heavy ion scattering. The numerical calculations carried out for /sup 18/O+ /sup 58/Ni scattering (E/sub lab/ = 60 MeV), a test case, agree well with the corresponding results of the phenomenological optical model.

  5. Condensation Dynamics on Mimicked Metal Matrix Hydrophobic Nanoparticle-Composites

    Science.gov (United States)

    Damle, Viraj; Sun, Xiaoda; Rykaczewski, Konrad

    2014-11-01

    Use of hydrophobic surfaces promotes condensation in the dropwise mode, which is significantly more efficient than the common filmwise mode. However, limited longevity of hydrophobic surface modifiers has prevented their wide spread use in industry. Recently, metal matrix composites (MMCs) having microscale hydrophobic heterogeneities dispersed in hydrophilic metal matrix have been proposed as durable and self-healing alternative to hydrophobic surface coatings interacting with deposited water droplets. While dispersion of hydrophobic microparticles in MMC is likely to lead to surface flooding during condensation, the effect of dispersion of hydrophobic nanoparticles (HNPs) with size comparable to water nuclei critical radii and spacing is not obvious. To this end, we fabricated highly ordered arrays of Teflon nanospheres on silicon substrates that mimic the top surface of the MMCs with dispersed HNPs. We used light and electron microscopy to observe breath figures resulting from condensation on these surfaces at varied degrees of subcooling. Here, we discuss the relation between the droplet size distribution, Teflon nanosphere diameter and spacing, and condensation mode. KR acknowledges startup funding from ASU.

  6. Experiments on Interactions of Electrons with Molecular Ions in Fusion and Astrophysical Plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Bannister, Mark E [ORNL; Aliabadi, Habib [ORNL; Bahati, Eric [ORNL; Fogle, Mark R. [Oak Ridge National Laboratory (ORNL); Krstic, Predrag S [ORNL; Vane, C Randy [ORNL; Ehlerding, A. [Stockholm University, Sweden; Geppert, W. [Stockholm University, Sweden; Hellberg, F. [Stockholm University, Sweden; Zhaunerchyk, Vitali [Stockholm University, Sweden; Larsson, Mats [Stockholm University, Sweden; Thomas, Richard D [ORNL

    2007-01-01

    Through beam-beam experiments at the Multicharged Ion Research Facility (MIRF) at Oak Ridge National Laboratory (ORNL) and at the CRYRING heavy ion storage ring at Stockholm University, we are seeking to formulate a more complete picture of electron-impact dissociation of molecular ions. These inelastic collisions play important roles in many low temperature plasmas such as in divertors of fusion devices and in astrophysical environments. An electron-ion crossed beams experiment at ORNL investigates the dissociative excitation and dissociative ionization of molecular ions from a few eV up to 100 eV. Measurements on dissociative recombination (DR) experiments are made at CRYRING, where chemical branching fractions and fragmentation dynamics are studied. Taking advantage of a 250-kV acceleration platform at the MIRF, a merged electron-ion beams energy loss apparatus is employed to study DR down to zero energy. Recent results on the dissociation of molecular ions of importance in fusion and astrophysics are presented.

  7. Angular studies of potential electron emission in the interaction of slow ions with Al surfaces

    Science.gov (United States)

    Riccardi; Barone; Bonanno; Oliva; Baragiola

    2000-01-10

    We report energy distributions of electrons emitted from Al surfaces under impact by 1 keV Ar+ and 1-5 keV Ne+ ions. The variation of the energy distributions with the angle of incidence is different for both ions and provides information on the mechanism responsible for electron emission. For Ar+ electron emission results mainly from Auger neutralization, while for Ne+ an important emission mechanism is the decay of plasmon excitations. We find a transition between surface and bulk plasmon excitations as the energy of the ion is increased.

  8. Dynamic Behaviors and Energy Transition Mechanism of Droplets Impacting on Hydrophobic Surfaces

    OpenAIRE

    Qiaogao Huang; Ya Zhang; Guang Pan

    2016-01-01

    The wettability of hydrophobic surfaces and the dynamic behaviors of droplets impacting on hydrophobic surfaces are simulated using a lattice Boltzmann method, and the condition for the rebound phenomenon of droplets impacting on solid surfaces is analyzed. The results show that there is a linear relationship between the intrinsic contact angle and the interaction strength of fluid-wall particles. For hydrophobic surfaces with the same intrinsic contact angle, the micromorphology can increase...

  9. Single-ion quantum Otto engine with always-on bath interaction

    Science.gov (United States)

    Chand, Suman; Biswas, Asoka

    2017-06-01

    We demonstrate how the reciprocating heat cycle of a quantum Otto engine (QOE) can be implemented using a single ion and an always-on thermal environment. The internal degree of freedom of the ion is chosen as the working fluid, while the motional degree of freedom can be used as the cold bath. We show, that by adiabatically changing the local magnetic field, the work efficiency can be asymptotically made unity. We propose a projective measurement of the internal state of the ion that mimics the release of heat from the working fluid during the engine cycle. In our proposal, the coupling to the hot and the cold baths need not be switched off and on in an alternate fashion during the engine cycle, unlike other existing proposals of QOE. This renders the proposal experimentally feasible using the available tapped-ion engineering technology.

  10. Metal ion-humic acid nanoparticle interactions: role of both complexation and condensation mechanisms.

    Science.gov (United States)

    Town, Raewyn M; van Leeuwen, Herman P

    2016-07-21

    Purely Donnan type models for electrostatic binding by humic acid (HA) nanoparticles are shown to be physically incomplete. To describe the extent of ion binding by HA, such models need to invoke parameters that are not consistent with experimental observations. These disparate parameters include anomalously high Donnan potentials, as well as intrinsic affinity constants for electrostatically associating ions such as Ca(2+). In contrast, the recently introduced counterion condensation - Donnan model (CCD) provides a physicochemically realistic description of the electrostatic contribution to metal ion binding by humic acid nanoparticles. The extent of Ca(2+)-HA association can be adequately described solely in terms of electrostatics only, including counterion condensation in the intraparticulate double layer in addition to Donnan partitioning in the remainder of the particle body. The binding of Cd(ii), Pb, (ii) and Cu(ii) by HA also involves inner-sphere complex formation leading to intraparticulate metal species distributions with major proportions of condensed and complexed ions.

  11. The interaction of actinide and lanthanide ions with hemoglobin and its relevance to human and environmental toxicology

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Amit, E-mail: amitk@barc.gov.in [Radiation Biology and Health Sciences Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Ali, Manjoor [Radiation Biology and Health Sciences Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Ningthoujam, Raghumani S. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Gaikwad, Pallavi [Department of Zoology, Savitribai Phule Pune University, Pune 411 007, Mumbai (India); Kumar, Mukesh [Solid State, Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Nath, Bimalendu B. [Department of Zoology, Savitribai Phule Pune University, Pune 411 007, Mumbai (India); Pandey, Badri N. [Radiation Biology and Health Sciences Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

    2016-04-15

    Highlights: • The sites of Ln and An interaction in Hb depend upon their charge-to-ionic-radii ratio. • Th(IV), Ce(IV) and U(VI) altered structure and oxygen-binding of Hb. • Spectroscopic studies determined binding characteristics of actinides. • Metal–Hb interaction was tested in an environmentally-important aquatic midge, Chironomus. - Abstract: Due to increasing use of lanthanides/actinides in nuclear and civil applications, understanding the impact of these metal ions on human health and environment is a growing concern. Hemoglobin (Hb), which occurs in all the kingdom of living organism, is the most abundant protein in human blood. In present study, effect of lanthanides and actinides [thorium: Th(IV), uranium: U(VI), lanthanum: La(III), cerium: Ce(III) and (IV)] on the structure and function of Hb has been investigated. Results showed that these metal ions, except Ce(IV) interacted with carbonyl and amide groups of Hb, which resulted in the loss of its alpha-helix conformation. However, beyond 75 μM, these ions affected heme moiety. Metal–heme interaction was found to affect oxygen-binding of Hb, which seems to be governed by their closeness with the charge-to-ionic-radius ratio of iron(III). Consistently, Ce(IV) being closest to iron(III), exhibited a greater effect on heme. Binding constant and binding stoichiometry of Th(IV) were higher than that of U(VI). Experiments using aquatic midge Chironomus (possessing human homologous Hb) and human blood, further validated metal–Hb interaction and associated toxicity. Thus, present study provides a biochemical basis to understand the actinide/lanthanide-induced interference in heme, which may have significant implications for the medical and environmental management of lanthanides/actinides toxicity.

  12. Mono-energetic ion beams accelerated in the interaction of an ultrashort intense laser with ultra-thin solid targets

    Science.gov (United States)

    Li, Jun; Arefiev, Alexey; McGuffey, Christopher; Beg, Farhat

    2017-10-01

    We performed particle-in-cell (PIC) simulations to study the ion acceleration by the interaction of an ultra-short (35fs) intense laser (1020W/cm2) with ultra-thin (6-100nm) copper targets. We aimed at investigating how ions are accelerated from thin targets, and focus on the regime in which targets remain intact and not broken through by the laser pulse. The target thicknesses were scanned, and we found that the ionization of copper ions to high Z states occurred during the acceleration. The mono-energetic high Z ion beams were observed only for the target thickness of 20nm with energies near 400 MeV. We conducted the particle tracking diagnostic to study the underline physics and mechanism of the acceleration, and the details will be presented in the meeting. This material is based upon work supported by the Air Force Office of Scientific Research under Award Number FA FA9550-14-1-0282. This work was performed using HPC resources provided by the Texas Advanced Computing Center at the University of Texas; This work also used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation Grant Number ACI-1548562.

  13. Study of quantitative interactions of potato and corn starch granules with ions in diluted solutions of heavy metal salts.

    Science.gov (United States)

    Szymońska, Joanna; Molenda, Marcin; Wieczorek, Jerzy

    2015-12-10

    Interactions of potato and corn starch granules with ions in diluted solutions of silver, lead, copper or iron salts were investigated. It was shown experimentally that granules accumulated the cations in amounts depending on the granule structure and water content as well as a type of both metal and counter-ions present in solution. Potato starch retained almost three times more cations compared to corn starch what was proportional to the total phosphorous content in these starches. Quantity of milligrams of cations bound by 1g of starch was inversely correlated with the cation hydration. Ag(+), Pb(2+) and Cu(2+) were connected in stoichiometric amounts of moles to semicrystalline and amorphous parts of the granules. Fe(3+) ions were accumulated in higher than stoichiometric quantities mainly in granule amorphous regions. Metal ions penetrated into granules together with anions except nitrates which remained on surface of potato starch granules. Cations facilitated the starch thermal decomposition in accordance with values of their standard redox potentials. Nitrates supported this process only in the presence of base metal cations. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Interaction of singly and multiply charged ions with a lithium-fluoride surface

    CERN Document Server

    Wirtz, L

    2001-01-01

    Charge transfer between slow ions and an ionic crystal surface still poses a considerable challenge to theory due to the intrinsic many-body character of the system. For the neutralization of multiply charged ions in front of metal surfaces, the Classical Over the Barrier (COB) model is a widely used tool. We present an extension of this model to ionic crystal surfaces where the localization of valence electrons at the anion sites and the lack of cylindrical symmetry of the ion-surface system impede a simple analytical estimate of electron transfer rates. We use a classical trajectory Monte Carlo approach to calculate electron transfer rates for different charge states of the projectile ion. With these rates we perform a Monte Carlo simulation of the neutralization of slow Ne10+ ions in vertical incidence on an LiF surface. Capture of one or several electrons may lead to a local positive charge up of the surface. The projectile dynamics depends on the balance between the repulsion due to this charge and the a...

  15. Photophysical studies of the interactions of poly(amidoamine) generation zero (PAMAM G0) with copper and zinc ions

    Energy Technology Data Exchange (ETDEWEB)

    López-Cabaña, Z.E. [Laboratory of Asymmetric Synthesis, Chemistry Institute of Natural Resources, University of Talca (Chile); Valdés, O. [Nanobiotechnology Division at University of Talca, Fraunhofer Chile Research Foundation – Center for Systems Biotechnology, FCR-CSB, P.O. Box 747 Talca (Chile); Vergara, C.E. [Laboratory of Asymmetric Synthesis, Chemistry Institute of Natural Resources, University of Talca (Chile); Camarada, M.B. [Universidad Andrés Bello, Facultad de Biología, Center for Bioinformatics and Integrative Biology (CBIB), República 239, Santiago (Chile); Fundación Fraunhofer Chile Research, M. Sánchez Fontecilla 310 piso 14, Las Condes (Chile); Nachtigall, F.M. [Nanobiotechnology Division at University of Talca, Fraunhofer Chile Research Foundation – Center for Systems Biotechnology, FCR-CSB, P.O. Box 747 Talca (Chile); González-Nilo, F.D. [Universidad Andrés Bello, Facultad de Biología, Center for Bioinformatics and Integrative Biology (CBIB), República 239, Santiago (Chile); Fundación Fraunhofer Chile Research, M. Sánchez Fontecilla 310 piso 14, Las Condes (Chile); Santos, Leonardo S., E-mail: lssantos@utalca.cl [Laboratory of Asymmetric Synthesis, Chemistry Institute of Natural Resources, University of Talca (Chile); Nanobiotechnology Division at University of Talca, Fraunhofer Chile Research Foundation – Center for Systems Biotechnology, FCR-CSB, P.O. Box 747 Talca (Chile)

    2015-08-15

    This study reports the photophysical behavior of poly(amidoamine) generation zero (PAMAM G0) in the presence of Cu(II) and Zn(II) ions in aqueous solutions using absorption and fluorescence spectroscopy. Theoretical and experimental results confirmed the presence of a strong covalent metal–ligand interaction between PAMAM G0 and copper ion that favored the formation of a ligand–metal charge transfer band coordination complex. In the case of Zn(II), no complex formation with PAMAM G0 was registered. Structure analysis identified the presence of aggregate like PAMAM G0–Zn moieties that generated an enhancement in the fluorescence emission of PAMAM G0. - Highlights: • Photophysical behavior of PAMAM G0 dendrimer with Cu and Zn ions was studied. • Strong covalent metal–ligand interaction was confirmed between PAMAM G0–Cu(II). • No complex formation with PAMAM G0 was registered in the case of Zn(II). • Dendrimer aggregate generated an enhancement in fluorescence emission.

  16. GUMBOS matrices of variable hydrophobicity for matrix-assisted laser desorption/ionization mass spectrometry.

    Science.gov (United States)

    Al Ghafly, Hashim; Siraj, Noureen; Das, Susmita; Regmi, Bishnu P; Magut, Paul K S; Galpothdeniya, Waduge Indika S; Murray, Kermit K; Warner, Isiah M

    2014-11-15

    Detection of hydrophobic peptides remains a major obstacle for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). This stems from the fact that most matrices for MALDI are hydrophilic and therefore have low affinities for hydrophobic peptides. Herein, 1-aminopyrene (AP) and AP-derived group of uniform materials based on organic salts (GUMBOS) as novel matrices for MALDI-MS analyses of peptides were investigated for hydrophobic and hydrophilic peptides. A number of solid-phase AP-based GUMBOS are synthesized with variable hydrophobicity simply by changing the counterions. Structures were confirmed by use of (1)H NMR and electrospray ionization mass spectrometry (ESI-MS). 1-Octanol/water partition coefficients (Ko/w) were used to measure the hydrophobicity of the matrices. A dried-droplet method was used for sample preparation. All spectra were obtained using a MALDI-TOF mass spectrometer in positive ion reflectron mode. A series of AP-based GUMBOS was synthesized including [AP][chloride] ([AP][Cl]), [AP][ascorbate] ([AP][Asc]) and [AP][bis(trifluoromethane)sulfonimide] ([AP][NTf2]). The relative hydrophobicities of these compounds and α-cyano-4-hydroxycinnamic acid (CHCA, a common MALDI matrix) indicated that AP-based GUMBOS can be tuned to be much more hydrophobic than CHCA. A clear trend is observed between the signal intensities of hydrophobic peptides and hydrophobicity of the matrix. MALDI matrices of GUMBOS with tunable hydrophobicities are easily obtained simply by varying the counterion. We have found that hydrophobic matrix materials are very effective for MALDI determination of hydrophobic peptides and, similarly, the more hydrophilic peptides displayed greater intensity in the more hydrophilic matrix. Copyright © 2014 John Wiley & Sons, Ltd.

  17. Switchable Pickering emulsions stabilized by silica nanoparticles hydrophobized in situ with a conventional cationic surfactant.

    Science.gov (United States)

    Zhu, Yue; Jiang, Jianzhong; Liu, Kaihong; Cui, Zhenggang; Binks, Bernard P

    2015-03-24

    A stable oil-in-water Pickering emulsion stabilized by negatively charged silica nanoparticles hydrophobized in situ with a trace amount of a conventional cationic surfactant can be rendered unstable on addition of an equimolar amount of an anionic surfactant. The emulsion can be subsequently restabilized by adding a similar trace amount of cationic surfactant along with rehomogenization. This destabilization-stabilization behavior can be cycled many times, demonstrating that the Pickering emulsion is switchable. The trigger is the stronger electrostatic interaction between the oppositely charged ionic surfactants compared with that between the cationic surfactant and the (initially) negatively charged particle surfaces. The cationic surfactant prefers to form ion pairs with the added anionic surfactant and thus desorbs from particle surfaces rendering them surface-inactive. This access to switchable Pickering emulsions is easier than those employing switchable surfactants, polymers, or surface-active particles, avoiding both the complicated synthesis and the stringent switching conditions.

  18. Measurement of attractive interactions produced by the ion wakefield in dusty plasmas using a constrained collision geometry.

    Science.gov (United States)

    Hebner, G A; Riley, M E

    2003-10-01

    Plasma dust particle interactions, charges, and screening lengths are derived from measurements of time-dependent particle positions in a simplified geometry. The magnitude and structure of the ion wakefield potential below a negatively charged dust particle levitated in the plasma sheath region were measured as functions of the pressure and interparticle spacing. Attractive and repulsive components of the interaction force were extracted from a trajectory analysis of low-energy dust collisions between different mass particles in a well-defined electrostatic potential that constrained the dynamics of the collisions to be one-dimensional. Typical peak attractions varied between 60 and 230 fN while the peak particle-particle repulsion was on the order of 60 fN. Random thermal motion of the particles contributed to observable rates for transitions between different equilibrium configurations of vertically separated particles. The influence of nearest- and non-nearest-neighbor interactions on calculated particle parameters is examined using several methods.

  19. Predicting Enzyme Adsorption to Lignin Films by Calculating Enzyme Surface Hydrophobicity*

    Science.gov (United States)

    Sammond, Deanne W.; Yarbrough, John M.; Mansfield, Elisabeth; Bomble, Yannick J.; Hobdey, Sarah E.; Decker, Stephen R.; Taylor, Larry E.; Resch, Michael G.; Bozell, Joseph J.; Himmel, Michael E.; Vinzant, Todd B.; Crowley, Michael F.

    2014-01-01

    The inhibitory action of lignin on cellulase cocktails is a major challenge to the biological saccharification of plant cell wall polysaccharides. Although the mechanism remains unclear, hydrophobic interactions between enzymes and lignin are hypothesized to drive adsorption. Here we evaluate the role of hydrophobic interactions in enzyme-lignin binding. The hydrophobicity of the enzyme surface was quantified using an estimation of the clustering of nonpolar atoms, identifying potential interaction sites. The adsorption of enzymes to lignin surfaces, measured using the quartz crystal microbalance, correlates to the hydrophobic cluster scores. Further, these results suggest a minimum hydrophobic cluster size for a protein to preferentially adsorb to lignin. The impact of electrostatic contribution was ruled out by comparing the isoelectric point (pI) values to the adsorption of proteins to lignin surfaces. These results demonstrate the ability to predict enzyme-lignin adsorption and could potentially be used to design improved cellulase cocktails, thus lowering the overall cost of biofuel production. PMID:24876380

  20. Surface Electrical Potentials of Root Cell Plasma Membranes: Implications for Ion Interactions, Rhizotoxicity, and Uptake

    Directory of Open Access Journals (Sweden)

    Yi-Min Wang

    2014-12-01

    Full Text Available Many crop plants are exposed to heavy metals and other metals that may intoxicate the crop plants themselves or consumers of the plants. The rhizotoxicity of heavy metals is influenced strongly by the root cell plasma membrane (PM surface’s electrical potential (ψ0. The usually negative ψ0 is created by negatively charged constituents of the PM. Cations in the rooting medium are attracted to the PM surface and anions are repelled. Addition of ameliorating cations (e.g., Ca2+ and Mg2+ to the rooting medium reduces the effectiveness of cationic toxicants (e.g., Cu2+ and Pb2+ and increases the effectiveness of anionic toxicants (e.g., SeO42− and H2AsO4−. Root growth responses to ions are better correlated with ion activities at PM surfaces ({IZ}0 than with activities in the bulk-phase medium ({IZ}b (IZ denotes an ion with charge Z. Therefore, electrostatic effects play a role in heavy metal toxicity that may exceed the role of site-specific competition between toxicants and ameliorants. Furthermore, ψ0 controls the transport of ions across the PM by influencing both {IZ}0 and the electrical potential difference across the PM from the outer surface to the inner surface (Em,surf. Em,surf is a component of the driving force for ion fluxes across the PM and controls ion-channel voltage gating. Incorporation of {IZ}0 and Em,surf into quantitative models for root metal toxicity and uptake improves risk assessments of toxic metals in the environment. These risk assessments will improve further with future research on the application of electrostatic theory to heavy metal phytotoxicity in natural soils and aquatic environments.

  1. Crystal lattice properties fully determine short-range interaction parameters for alkali and halide ions.

    Science.gov (United States)

    Mao, Albert H; Pappu, Rohit V

    2012-08-14

    Accurate models of alkali and halide ions in aqueous solution are necessary for computer simulations of a broad variety of systems. Previous efforts to develop ion force fields have generally focused on reproducing experimental measurements of aqueous solution properties such as hydration free energies and ion-water distribution functions. This dependency limits transferability of the resulting parameters because of the variety and known limitations of water models. We present a solvent-independent approach to calibrating ion parameters based exclusively on crystal lattice properties. Our procedure relies on minimization of lattice sums to calculate lattice energies and interionic distances instead of equilibrium ensemble simulations of dense fluids. The gain in computational efficiency enables simultaneous optimization of all parameters for Li+, Na+, K+, Rb+, Cs+, F-, Cl-, Br-, and I- subject to constraints that enforce consistency with periodic table trends. We demonstrate the method by presenting lattice-derived parameters for the primitive model and the Lennard-Jones model with Lorentz-Berthelot mixing rules. The resulting parameters successfully reproduce the lattice properties used to derive them and are free from the influence of any water model. To assess the transferability of the Lennard-Jones parameters to aqueous systems, we used them to estimate hydration free energies and found that the results were in quantitative agreement with experimentally measured values. These lattice-derived parameters are applicable in simulations where coupling of ion parameters to a particular solvent model is undesirable. The simplicity and low computational demands of the calibration procedure make it suitable for parametrization of crystallizable ions in a variety of force fields.

  2. Facilitated Ion Transport in Smectic Ordered Ionic Liquid Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jin Hong [Materials Architecturing Research Center, Korea Institute of Science and Technology, Hwarang-ro 14-gil 5 Seongbuk-gu Seoul 136-791 South Korea; School of Chemical and Biological Engineering and Institute of Chemical Process, Seoul National University, 599 Gwanak-ro Gwanak-gu Seoul 151-742 South Korea; Han, Kee Sung [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland WA 99354 USA; Lee, Je Seung [Department of Chemistry, Kyung Hee University, 26 Kyungheedae-ro Dongdaemun-gu Seoul 02447 South Korea; Lee, Albert S. [Materials Architecturing Research Center, Korea Institute of Science and Technology, Hwarang-ro 14-gil 5 Seongbuk-gu Seoul 136-791 South Korea; Park, Seo Kyung [Department of Chemistry, Kyung Hee University, 26 Kyungheedae-ro Dongdaemun-gu Seoul 02447 South Korea; Hong, Sung Yun [Department of Chemistry, Kyung Hee University, 26 Kyungheedae-ro Dongdaemun-gu Seoul 02447 South Korea; Lee, Jong-Chan [School of Chemical and Biological Engineering and Institute of Chemical Process, Seoul National University, 599 Gwanak-ro Gwanak-gu Seoul 151-742 South Korea; Mueller, Karl T. [Department of Chemistry, Pennsylvania State University, University Park PA 16802 USA; Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland WA 99352 USA; Hong, Soon Man [Materials Architecturing Research Center, Korea Institute of Science and Technology, Hwarang-ro 14-gil 5 Seongbuk-gu Seoul 136-791 South Korea; Nanomaterials Science and Engineering, University of Science and Technology, Gajeong-ro Yuseong-gu Daejeon 305-350 South Korea; Koo, Chong Min [Materials Architecturing Research Center, Korea Institute of Science and Technology, Hwarang-ro 14-gil 5 Seongbuk-gu Seoul 136-791 South Korea; Nanomaterials Science and Engineering, University of Science and Technology, Gajeong-ro Yuseong-gu Daejeon 305-350 South Korea

    2016-09-08

    We investigated a novel ionic mixture of an imidazolium-based room temperature IL containing ethylene oxide functionalized phosphite anion and a lithium salt that self-assembles into a smectic-ordered IL crystal. The two key features in this work are the unique origin of the smectic order of the ionic mixtures and the facilitated ion transport behavior in the smectic ordered IL crystal. In fact, the IL crystals are self-assembled through Coulombic interactions between ion species, not through the hydrophilic-phobic interactions between charged ion heads and hydrophobic long alkyl pendants or the steric interaction between mesogenic moieties. Furthermore, the smectic order in the IL crystal ionogel facilitates exceptional and remarkable ionic transport. Large ionic conductivity, viscoelastic robustness, and additional electrochemical stability of the IL crystal ionogels provide promising opportunities for future electrochemical applications.

  3. Electron Bubbles in Superfluid $^3$He-A: Exploring the Quasiparticle-Ion Interaction

    OpenAIRE

    Shevtsov, Oleksii; Sauls, J. A.

    2016-01-01

    When an electron is forced into liquid $^3$He it forms an "electron bubble", a heavy ion with radius, $R\\simeq 1.5$ nm, and mass, $M\\simeq 100\\,m_3$, where $m_3$ is the mass of a $^3$He atom. These negative ions have proven to be powerful local probes of the physical properties of the host quantum fluid, especially the excitation spectra of the superfluid phases. We recently developed a theory for Bogoliubov quasiparticles scattering off electron bubbles embedded in a chiral superfluid that p...

  4. Efficient ion beam generation in laser interactions with micro-structured targets

    Science.gov (United States)

    Limpouch, J.; Klimo, O.; Psikal, J.; Proska, J.; Novotny, F.; Margarone, D.; Velyhan, A.; Cutroneo, M.; Torrisi, L.

    2013-11-01

    The maximum ion energy and acceleration efficiency have to be increased for practical applications of intense ion beams produced by intense short laser pulses incident on a thin foil. For this aim, we propose to use foil with a microscopic structure on the front size. We have prepared such targets by depositing a monolayer of polystyrene nanospheres of a size comparable to laser wavelength on a thin foil. The damage threshold of the produced targets is found experimentally above 3.5 × 109 W/cm2 for a nanosecond pedestal and above 1011 W/cm2 for femtosecond prepulses.

  5. Efficient ion beam generation in laser interactions with micro-structured targets

    Directory of Open Access Journals (Sweden)

    Limpouch J.

    2013-11-01

    Full Text Available The maximum ion energy and acceleration efficiency have to be increased for practical applications of intense ion beams produced by intense short laser pulses incident on a thin foil. For this aim, we propose to use foil with a microscopic structure on the front size. We have prepared such targets by depositing a monolayer of polystyrene nanospheres of a size comparable to laser wavelength on a thin foil. The damage threshold of the produced targets is found experimentally above 3.5 × 109  W/cm2 for a nanosecond pedestal and above 1011  W/cm2 for femtosecond prepulses.

  6. Efficient ion beam generation in laser interactions with micro-structured targets

    OpenAIRE

    Limpouch J.; Klimo O.; Psikal J.; Proska J.; Novotny F.; Margarone D.; Velyhan A.; Cutroneo M.; Torrisi L.

    2013-01-01

    The maximum ion energy and acceleration efficiency have to be increased for practical applications of intense ion beams produced by intense short laser pulses incident on a thin foil. For this aim, we propose to use foil with a microscopic structure on the front size. We have prepared such targets by depositing a monolayer of polystyrene nanospheres of a size comparable to laser wavelength on a thin foil. The damage threshold of the produced targets is found experimentally above 3.5 × 109  W/...

  7. Water structuring and collagen adsorption at hydrophilic and hydrophobic silicon surfaces.

    Science.gov (United States)

    Cole, Daniel J; Payne, Mike C; Ciacchi, Lucio Colombi

    2009-12-28

    The adsorption of a collagen fragment on both a hydrophobic, hydrogen-terminated and a hydrophilic, natively oxidised Si surface is investigated using all-atom molecular dynamics. While favourable direct protein-surface interactions via localised contact points characterise adhesion to the hydrophilic surface, evenly spread surface/molecule contacts and stabilisation of the helical structure occurs upon adsorption on the hydrophobic surface. In the latter case, we find that adhesion is accompanied by a mutual fit between the hydrophilic/hydrophobic pattern within the protein and the layered water structure at the solid/liquid interface, which may provide an additional driving force to the classic hydrophobic effect.

  8. Control of energy spread and dark current in proton and ion beams generated in high-contrast laser solid interactions.

    Science.gov (United States)

    Dollar, F; Matsuoka, T; Petrov, G M; Thomas, A G R; Bulanov, S S; Chvykov, V; Davis, J; Kalinchenko, G; McGuffey, C; Willingale, L; Yanovsky, V; Maksimchuk, A; Krushelnick, K

    2011-08-05

    By using temporal pulse shaping of high-contrast, short pulse laser interactions with solid density targets at intensities of 2 × 10(21) W cm(-2) at a 45° incident angle, we show that it is possible to reproducibly generate quasimonoenergetic proton and ion energy spectra. The presence of a short pulse prepulse 33 ps prior to the main pulse produced proton spectra with an energy spread between 25% and 60% (ΔE/E) with energy of several MeV, with light ions becoming quasimonoenergetic for 50 nm targets. When the prepulse was removed, the energy spectra was broad. Numerical simulations suggest that expansion of the rear-side contaminant layer allowed for density conditions that prevented the protons from being screened from the sheath field, thus providing a low energy cutoff in the observed spectra normal to the target surface.

  9. Measuring the spacecraft and environmental interactions of the 8-cm mercury ion thrusters on the P80-1 mission

    Science.gov (United States)

    Power, J. L.

    1981-01-01

    The subject interface measurements are described for the Ion Auxiliary Propulsion System (IAPS) flight test of two 8-cm thrusters. The diagnostic devices and the effects to be measured include: 1) quartz crystal microbalances to detect nonvolatile deposition due to thruster operation; 2) warm and cold solar cell monitors for nonvolatile and volatile (mercury) deposition; 3) retarding potential ion collectors to characterize the low energy thruster ionic efflux; and 4) a probe to measure the spacecraft potential and thruster generated electron currents to biased spacecraft surfaces. The diagnostics will also assess space environmental interactions of the spacecraft and thrusters. The diagnostic data will characterize mercury thruster interfaces and provide data useful for future applications.

  10. Super-Hydrophobic Green Corrosion Inhibitor On Carbon Steel

    Science.gov (United States)

    Hassan, H.; Ismail, A.; Ahmad, S.; Soon, C. F.

    2017-06-01

    There are many examples of organic coatings used for corrosion protection. In particular, hydrophobic and super-hydrophobic coatings are shown to give good protection because of their enhanced ability to slow down transport of water and ions through the coating. The purpose of this research is to develop water repellent coating to avoid direct contact between metal and environment corrosive and mitigate corrosion attack at pipeline system. This water repellent characteristic on super-hydrophobic coating was coated by electrodeposition method. Wettability of carbon steel with super-hydrophobic coating (cerium chloride and myristic acid) and oxidized surface was investigated through contact angle and inhibitor performance test. The inhibitor performance was studied in 25% tannin acid corrosion test at 30°C and 3.5% sodium chloride (NaCl). The water contact angle test was determined by placing a 4-μL water droplet of distilled water. It shows that the wettability of contact angle super-hydrophobic with an angle of 151.60° at zero minute can be classified as super-hydrophobic characteristic. By added tannin acid as inhibitor the corrosion protection on carbon steel becomes more consistent. This reveals that the ability of the coating to withstand with the corrosion attack in the seawater at different period of immersions. The results elucidate that the weight loss increased as the time of exposure increased. However, the corrosion rates for uncoated carbon steel is high compared to coated carbon steel. As a conclusion, from both samples it can be seen that the coated carbon steel has less corrosion rated compared to uncoated carbon steel and addition of inhibitor to the seawater provides more protection to resist corrosion attack on carbon steel.

  11. 3D Simulations of Ultra-small MOSFETs with Real-space Treatment of the Electron – Electron and Electron-ion Interactions

    OpenAIRE

    Gross, W. J.; Vasileska, D.; Ferry, D. K.

    2000-01-01

    We present a 3D Ensemble Monte Carlo particle-based simulator with a novel realspace treatment of the short-range electron – electron and electron-ion interactions. By using a corrected Coulomb force in conjunction with a proper cutoff range, the shortrange portion of the force is properly accounted for, and the ‘double counting’ of the long-range interaction is eliminated. The proposed method naturally incorporates the multi-ion contributions, local distortions in the scatteri...

  12. Novel lanthanide doped micro- and mesoporous solids. Characterization of ion-host-interactions, species distribution and luminescence properties using time-resolved luminescence spectroscopy; Neuartige Lanthanoid-dotierte mikro- und mesoporoese Feststoffe. Charakterisierung von Ion-Wirt-Wechselwirkungen, Speziesverteilung und Lumineszenzeigenschaften mittels zeitaufgeloester Lumineszenzspektroskopie

    Energy Technology Data Exchange (ETDEWEB)

    Gessner, Andre

    2010-12-15

    mesopores. Lanthanide ions located here, are easily accessible for water and thus show shorter luminescence decay times and a more symmetrical coordination sphere, which is mostly made up by water molecules. Another investigated aspect was the influence of surface modifications on the luminescence behavior of the lanthanide ions inside the material. Here we could show, that surface modifications hydrophobize the material and thus are able to protect the lanthanide ions from water, which is important for the conservation of the luminescence properties. Concerning the mesoporous silicates, again a heterogeneous distribution of the lanthanide ions in the pore system was found. A part of the lanthanide ions interacts with the pore wall, while the other part is located in the aqueous phase inside the pores. Surface modification led to a interaction of the lanthanide ions with the modification. This was reflected in the luminescence properties depending on the structure of the modification and the surface loading.

  13. Rheological Properties in Aqueous Solution for Hydrophobically Modified Polyacrylamides Prepared in Inverse Emulsion Polymerization

    Directory of Open Access Journals (Sweden)

    Shirley Carro

    2017-01-01

    Full Text Available Inverse emulsion polymerization technique was employed to synthesize hydrophobically modified polyacrylamide polymers with hydrophobe contents near to feed composition. Three different structures were obtained: multisticker, telechelic, and combined. N-Dimethyl-acrylamide (DMAM, n-dodecylacrylamide (DAM, and n-hexadecylacrylamide (HDAM were used as hydrophobic comonomers. The effect of the hydrophobe length of comonomer, the initial monomer, and surfactant concentrations on shear viscosity was studied. Results show that the molecular weight of copolymer increases with initial monomer concentration and by increasing emulsifier concentration it remained almost constant. Shear viscosity measurements results show that the length of the hydrophobic comonomer augments the hydrophobic interactions causing an increase in viscosity and that the polymer thickening ability is higher for combined polymers.

  14. Structure of Hydrophobically Modified Phytoglycogen Nanoparticles

    Science.gov (United States)

    Atkinson, John; Nickels, Jonathan; Dutcher, John; Katsaras, John

    Phytoglycogen is a highly branched, polysaccharide nanoparticle produced by some varieties of plants including sweet corn. These particles are attractive candidates for cosmetic, industrial and biomedical applications. Many of these applications result from phytoglycogen's unique interaction with water: (1) high solubility; (2) low viscosity and high stability in aqueous dispersions; and (3) a remarkable capacity to sequester and retain water. Neutron scattering measurements of native phytoglycogen revealed that the particles have uniform size, uniform radial particle density, and a high level of hydration. Hydrophobically modifying the outer surface of the hydrophilic nanoparticles opens up new applications in food and biomedicine, such as solubilizing and stabilizing bioactive compounds. One such modification is octenyl succinate anhydride (OSA), where the hydrophobicity can be tuned by adjusting the degree of substitution. I will present the results of small angle neutron scattering (SANS) measurements of aqueous dispersions of OSA-modified phytoglycogen with two different degrees of modification. Contrast series SANS measurements have yielded information about the radial density profile, providing insight into the nature of the chemical modification of the particles.

  15. Hydrophobic Calcium Carbonate for Cement Surface

    Directory of Open Access Journals (Sweden)

    Shashi B. Atla

    2017-12-01

    Full Text Available This report describes a novel way to generate a highly effective hydrophobic cement surface via a carbonation route using sodium stearate. Carbonation reaction was carried out at different temperatures to investigate the hydrophobicity and morphology of the calcium carbonate formed with this process. With increasing temperatures, the particles changed from irregular shapes to more uniform rod-like structures and then aggregated to form a plate-like formation. The contact angle against water was found to increase with increasing temperature; after 90 °C there was no further increase. The maximum contact angle of 129° was obtained at the temperature of 60 °C. It was also found that carbonation increased the micro hardness of the cement material. The micro hardness was found to be dependent on the morphology of the CaCO3 particles. The rod like structures which caused increased mineral filler produced a material with enhanced strength. The 13C cross polarization magic-angle spinning NMR spectra gave plausible explanation of the interaction of organic-inorganic moieties.

  16. Interaction between High-Voltage Cathode Materials and Ionic Liquids for Novel Li-Ion Batteries

    NARCIS (Netherlands)

    Locati, C.

    2012-01-01

    The fast-growing market on electronic portable devices is possibly due to the development of Li-ion batteries. Besides, such batteries are the most promising candidates as energy storage media in (hybrid) electric vehicles, in the near future. However, improvements on electrochemical performances

  17. Constructed molecular sensor to enhance metal detection by bacterial ribosomal switch-ion channel protein interaction.

    Science.gov (United States)

    Cuero, Raul; Lilly, J; McKay, David S

    2012-03-31

    Molecular biosensors are useful tools that detect metal ions or other potentially toxic chemicals. However, the efficiency of conventional sensors is limited in mixed metals substrates, which is the common way they are found in nature. The use of biosensors constructed from genetically modified living microbial systems has the potential of providing sensitive detection systems for specific toxic targets. Consequently, our investigation was aimed at assembling different genetic building blocks to produce a focused microbial biosensor with the ability to detect specific metals. This objective was achieved by using a synthetic biology approach. Our genetic building blocks, including a synchronized ribosomal switch-iron ion channel, along with sequences of promoters, metal-binding proteins (Fe, Pb), ribosomal binding sites, yellow fluorescence reporter protein (YFRP), and terminators, were constructed within the same biobrick in Escherichia coli. We used an rpoS ribosomal switch containing an aptamer, which responds to the specific metal ligands, in synchronization with an iron ion channel, TonB. This switch significantly stimulates translation, as expressed by higher fluorescence, number of colonies, and concentration of RNA in E. coli. The positive results show the effectiveness of using genetically tailored synchronized ribosomal switch-ion channels to construct microbial biosensors to detect specific metals, as tested in iron solutions. Copyright © 2012 Elsevier B.V. All rights reserved.

  18. Interactions between humic acid and hematite and their effects on metal ion speciation

    NARCIS (Netherlands)

    Vermeer, A.W.P.

    1996-01-01


    The impact of toxic chemicals (like metal ions) on the environment is a phenomenon that has been recognised as a mayor problem over the last decades. The speciation of these chemicals determines whether or not a contaminated site has to be regarded as dangerous. The fate of the

  19. Explaining Ionic Liquid Water Solubility in Terms of Cation and Anion Hydrophobicity

    OpenAIRE

    Johannes Ranke; Alaa Othman; Ping Fan; Anja Müller

    2009-01-01

    The water solubility of salts is ordinarily dictated by lattice energy and ion solvation. However, in the case of low melting salts also known as ionic liquids, lattice energy is immaterial and differences in hydrophobicity largely account for differences in their water solubility. In this contribution, the activity coefficients of ionic liquids in water are split into cation and anion contributions by regression against cation hydrophobicity parameters that are experimentally determined by r...

  20. A script to highlight hydrophobicity and charge on protein surfaces

    Directory of Open Access Journals (Sweden)

    Dominique eHagemans

    2015-10-01

    Full Text Available The composition of protein surfaces determines both affinity and specificity of protein-protein interactions. Matching of hydrophobic contacts and charged groups on both sites of the interface are crucial to ensure specificity. Here, we propose a highlighting scheme, YRB, which highlights both hydrophobicity and charges in protein structures. YRB highlighting visualises hydrophobicity by highlighting all carbon atoms that are not bound to nitrogen and oxygen atoms. The charged oxygens of glutamate and aspartate are highlighted red and the charged nitrogens of arginine and lysine are highlighted blue. For a set of representative examples, we demonstrate that YRB highlighting intuitively visualises segments on protein surfaces that contribute to specificity in protein-protein interfaces, including Hsp90/co-chaperone complexes, SNARE complex and a transmembrane domain. We provide YRB highlighting in form of a script that runs using the software PyMOL.

  1. $p\\Xi^- $ Correlation in Relativistic Heavy Ion Collisions with Nucleon-Hyperon Interaction from Lattice QCD

    OpenAIRE

    Hatsuda, Tetsuo(Theoretical Research Division, Nishina Center, RIKEN, Saitama 351-0198, Japan); Morita, Kenji; Ohnishi, Akira; Sasaki, Kenji

    2017-01-01

    On the basis of the $p\\Xi^-$ interaction extracted from (2+1)-flavor lattice QCD simulations at the physical point, the momentum correlation of $p$ and $\\Xi^-$ produced in relativistic heavy ion collisions is evaluated. $C_{\\rm SL}(Q)$ defined by a ratio of the momentum correlations between the systems with different source sizes is shown to be largely enhanced at low momentum due to the strong attraction between $p$ and $\\Xi^-$ in the $I=J=0$ channel. Thus, measuring this ratio at RHIC and L...

  2. Above-surface neutralization of slow N[sup 6+] ions during interactions with a Cu(001) target

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, F.W.; Havener, C.C.; Zeijlmans van Emmichoven, P.A. (Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6372 (United States) Joint Institute for Heavy Ion Research, Holifield Heavy Ion Research Facility, Oak Ridge, Tennessee 37831-6374 (United States))

    1993-12-01

    Measurements are reported for projectile [ital K]-Auger-electron emission, observed at 90[degree] to the incident beam direction, during interactions of 60-keV N[sup 6+] ions with a clean Cu(001) target at grazing incidence angles in the range 0.2[degree]--20[degree]. Spectral features in the projectile [ital K]-Auger-electron spectra consistent with above-surface [ital K]-Auger-electron emission were observed at perpendicular velocities below 1.37[times]10[sup [minus]2] a.u. (incidence angle [Psi][lt]1.9[degree]). At incidence angles below 0.8[degree] ([ital v][sub [perpendicular

  3. Energy dissipation of highly charged ions interacting with solid surfaces; Energieeintrag langsamer hochgeladener Ionen in Festkoerperoberflaechen

    Energy Technology Data Exchange (ETDEWEB)

    Kost, D.

    2006-07-01

    Motivated by the incomplete scientific description of the relaxation of highly charged ions in front of solid surfaces and their energy balance, this thesis describes an advanced complementary study of determining deposited fractions and re-emitted fractions of the potential energy of highly charged ions. On one side, a calorimetric measurement setup is used to determine the retained potential energy and on the other side, energy resolved electron spectroscopy is used for measuring the reemitted energy due to secondary electron emission. In order to study the mechanism of energy retention in detail, materials with different electronic structures are investigated: Cu, n-Si, p-Si and SiO{sub 2}. In the case of calorimetry, a linear relationship between the deposited potential energy and the inner potential energy of the ions was determined. The total potential energy which stays in the solid remains almost constant at about (80 {+-} 10) %. Comparing the results of the Cu, n-Si and p-Si targets, no significant difference could be shown. Therefore we conclude that the difference in energy deposition between copper, n-doped Si and p-doped Si is below 10 %, which is significantly lower than using SiO{sub 2} targets. For this purpose, electron spectroscopy provides a complementary result. For Cu and Si surfaces, an almost linear increase of the re-emitted energy with increasing potential energy of the ion up to Ar{sup 7+} was also observed. The ratio of the re-emitted energy is about (10 {+-} 5) % of the total potential energy of the incoming ion, almost independent of the ion charge state. In contrast, an almost vanishing electron emission was observed for SiO{sub 2} and for charge states below q=7. For Ar{sup 8+} and Ar{sup 9+}, the electron emission increased due to the contribution of the projectile LMM Auger electrons and the re-emitted energy amounts up to 20 % for Cu and Si and around 10 % for SiO{sub 2}. These results are in good agreement with the calorimetric

  4. Biomimetic solution against dewetting in a highly hydrophobic nanopore.

    Science.gov (United States)

    Picaud, Fabien; Paris, Guillaume; Gharbi, Tijani; Balme, Sébastien; Lepoitevin, Mathilde; Tangaraj, Vidhyadevi; Bechelany, Mikhael; Janot, Jean Marc; Balanzat, Emmanuel; Henn, François

    2016-06-14

    A water molecule is the foundation of life and is the primary compound in every living system. While many of its properties are understood in a bulk solvent, its behavior in a small hydrophobic nanopore still raises fundamental questions. For instance, a wetting/dewetting transition in a hydrophobic solid-state or a polymer nanopore occurs stochastically and can only be prevented by external physical stimuli. Controlling these transitions would be a primary requirement to improve many applications. Some biological channels, such as gramicidin A (gA) proteins, show a high rate of water and ion diffusion in their central subnanochannel while their external surface is highly hydrophobic. The diameter of this channel is significantly smaller than the inner size of the lowest artificial nanopore in which water drying occurs (i.e. 1.4 nm). In this paper, we propose an innovative idea to generate nanopore wetting as a result of which the application of an external field is no longer required. In a nanopore, the drying or wetting of the inner walls occurs randomly (in experiments and in simulations). However, we have shown how the confinement of gA, in a dried hydrophobic nanopore, rapidly generates a stable wetting of the latter. We believe that this simple idea, based on biomimetism, could represent a real breakthrough that could help to improve and develop new nanoscale applications.

  5. Hydrophobic-Core Microcapsules and Their Formation

    Science.gov (United States)

    Calle, Luz M. (Inventor); Li, Wenyan (Inventor); Buhrow, Jerry W. (Inventor); Jolley, Scott T. (Inventor)

    2016-01-01

    Hydrophobic-core microcapsules and methods of their formation are provided. A hydrophobic-core microcapsule may include a shell that encapsulates a hydrophobic substance with a core substance, such as dye, corrosion indicator, corrosion inhibitor, and/or healing agent, dissolved or dispersed therein. The hydrophobic-core microcapsules may be formed from an emulsion having hydrophobic-phase droplets, e.g., containing the core substance and shell-forming compound, dispersed in a hydrophilic phase. The shells of the microcapsules may be capable of being broken down in response to being contacted by an alkali, e.g., produced during corrosion, contacting the shell.

  6. Fiber Optic Sensors for the Study of Spacecraft-Thruster Interactions: Ion Sputtering

    National Research Council Canada - National Science Library

    Ketsdever, Andrew D

    2001-01-01

    .... Typically, quartz crystal microbalances (QCMs) are used to investigate spacecraft-thruster interactions where the major contamination mechanism is the adsorption of molecular species on critical surfaces...

  7. The effect of electrostatic interactions on conformational equilibria of multiply substituted tetrahydropyran oxocarbenium ions.

    Science.gov (United States)

    Yang, Michael T; Woerpel, K A

    2009-01-16

    The three-dimensional structures of dioxocarbenium ions related to glycosyl cations were determined by an analysis of spectroscopic, computational, and reactivity data. Hypothetical low-energy structures of the dioxocarbenium ions were correlated with both experimentally determined (1)H NMR coupling constants and diastereoselectivity results from nucleophilic substitution reactions. This method confirmed the pseudoaxial preference of C-3 alkoxy-substituted systems and revealed the conformational preference of the C-5 alkoxymethyl group. Although the monosubstituted C-5 alkoxymethyl substituent preferred a pseudoequatorial orientation, the C-5-C-6 bond rotation was controlled by an electrostatic effect. The preferred diaxial conformer of the trans-4,5-disubstituted tetrahydropyranyl system underscored the importance of electrostatic effects in dictating conformational equilibria. In the 2-deoxymannose system, although steric effects influenced the orientation of the C-5 alkoxymethyl substituent, the all-axial conformer was favored because of electrostatic stabilization.

  8. The rotation of NO3− as a probe of molecular ion - water interactions

    Directory of Open Access Journals (Sweden)

    Ogden T.

    2013-03-01

    Full Text Available The hydration dynamics of aqueous nitrate, NO3−(aq, is studied by 2D-IR spectroscopy, UV-IR- and UV-UV transient absorption spectroscopy. The experimental results are compared to Car-Parinello molecular dynamics (MD simulations. The 2D-IR measurements and MD simulations of the non-degenerate asymmetric stretch vibrations of nitrate reveal an intermodal energy exchange occurring on a 0.2 ps time scale related to hydrogen bond fluctuations. The transient absorption measurements find that the nitrate ions rotate in 2 ps. The MD simulations indicate that the ion rotation is associated with the formation of new hydrogen bonds. The 2 ps rotation time thus indicates that the hydration shell of aqueous nitrate is rather labile.

  9. Interaction of the model alkyltrimethylammonium ions with alkali halide salts: an explicit water molecular dynamics study

    Directory of Open Access Journals (Sweden)

    M. Druchok

    2013-01-01

    Full Text Available We present an explicit water molecular dynamics simulation of dilute solutions of model alkyltrimethylammonium surfactant ions (number of methylene groups in the tail is 3, 5, 8, 10, and 12 in mixture with NaF, NaCl, NaBr, and NaI salts, respectively. The SPC/E model is used to describe water molecules. Results of the simulation at 298 K are presented in form of the radial distribution functions between nitrogen and carbon atoms of CH2 groups on the alkyltrimethylammonium ion, and the counterion species in the solution. The running coordination numbers between carbon atoms of surfactants and counterions are also calculated. We show that I- counterion exhibits the highest, and F- the lowest affinity to "bind" to the model surfactants. The results are discussed in view of the available experimental and simulation data for this and similar solutions.

  10. Exchange interaction of strongly anisotropic tripodal erbium single-ion magnets with metallic surfaces

    DEFF Research Database (Denmark)

    Dreiser, Jan; Wäckerlin, Christian; Ali, Md. Ehesan

    2014-01-01

    on a Ni thin film on Cu(100) single-crystalline surfaces. X-ray magnetic circular dichroism (XMCD) measurements performed on Au(111) samples covered with molecular monolayers held at temperatures down to 4 K suggest that the easy axes of the strongly anisotropic molecules are randomly oriented......We present a comprehensive study of Er(trensal) single-ion magnets deposited in ultrahigh vacuum onto metallic surfaces. X-ray photoelectron spectroscopy reveals that the molecular structure is preserved after sublimation, and that the molecules are physisorbed on Au(111) while they are chemisorbed....... Furthermore XMCD indicates a weak antiferromagnetic exchange coupling between the single-ion magnets and the ferromagnetic Ni/Cu(100) substrate. For the latter case, spin-Hamiltonian fits to the XMCD M(H) suggest a significant structural distortion of the molecules. Scanning tunneling microscopy reveals...

  11. Ion Beam Pulse Interaction with Background Plasma in a Solenoidal Magnetic Field

    CERN Document Server

    Kaganovich, Igor D; Startsev, Edward

    2005-01-01

    Background plasma can be used as an effective neutralization scheme to transport and compress intense ion beam pulses, and the application of a solenoidal magnetic field allows additional control and focusing of the beam pulse. Ion beam pulse propagation in a background plasma immersed in an applied solenoidal magnetic field has been studied both analytically and numerically with three different particle-in-cell codes (LSP, OOPIC-Pro and EDPIC) to cross-check the validity of the results. Very good charge and current neutralization is observed for high values of the solenoidal magnetic field.* However, for intermediate values of the solenoidal magnetic field, current neutralization is a complex process, and a sizable self-magnetic field is generated at the head of the beam. Collective wave excitations are also generated ahead of the beam pulse.

  12. Impurity/defect interactions during MeV Si{sup +} ion implantation annealing

    Energy Technology Data Exchange (ETDEWEB)

    Agarwal, A.; Koveshnikov, S.; Christensen, K. [North Carolina State Univ., Raleigh, NC (United States)] [and others

    1995-08-01

    Ion implantation of dopant atoms at MeV energies is currently being explored in several integrated circuit device manufacturing processes. MeV implantation offers immediate advantages such as vertical well modulation, latch-up protection, device structure isolation, and reduced temperature processing. Simultaneously, it presents an opportunity to achieve {open_quotes}proximity{close_quotes} gettering of impurities from the active device region by placing high impurity solubility and/or secondary defect gettering sites within microns of the surface. If the MeV implanted species is a dopant ion, all three gettering mechanisms, i.e, segregation, relaxation and injection, can be involved in the gettering process, complicating the analysis and optimization of the process. However, investigation of gettering using non-dopant Si{sup +} ion damage allows the relaxation component of the gettering process to be isolated and examined separately. In general, gettering is verified by a reduction in impurity concentration in the region of interest, usually the device region, and/or a build-up of concentration/precipitation in a non-device sink region. An alternate and more meaningful approach is to use simple devices as materials characterization probes via changes in the electrical activity of the gettering sites. Device space charge probes also allow the evolution of the defect sites upon contamination to be tracked. We report here results of the electrical, structural, and chemical characterization of MeV implanted Si{sup +} damage using Deep Level Transient Spectroscopy (DLTS), Transmission Electron Microscopy (TEM), and Secondary Ion Mass Spectroscopy (SIMS). The damage has been characterized both as a function of annealing from 600 to 1100{degrees}C for 1 hr, and after contamination with Fe followed by low temperature gettering annealing.

  13. Ni ion release, osteoblast-material interactions, and hemocompatibility of hafnium-implanted NiTi alloy.

    Science.gov (United States)

    Zhao, Tingting; Li, Yan; Zhao, Xinqing; Chen, Hong; Zhang, Tao

    2012-04-01

    Hafnium ion implantation was applied to NiTi alloy to suppress Ni ion release and enhance osteoblast-material interactions and hemocompatibility. The auger electron spectroscopy, x-ray photoelectron spectroscopy, and atomic force microscope results showed that a composite TiO(2)/HfO(2) nanofilm with increased surface roughness was formed on the surface of NiTi, and Ni concentration was reduced in the superficial surface layer. Potentiodynamic polarization tests displayed that 4 mA NiTi sample possessed the highest E(br) - E(corr), 470 mV higher than that of untreated NiTi, suggesting a significant improvement on pitting corrosion resistance. Inductively coupled plasma mass spectrometry tests during 60 days immersion demonstrated that Ni ion release rate was remarkably decreased, for example, a reduction of 67% in the first day. The water contact angle increased and surface energy decreased after Hf implantation. Cell culture and methyl-thiazol-tetrazolium indicated that Hf-implanted NiTi expressed enhanced osteoblasts adhesion and proliferation, especially after 7 days culture. Hf implantation decreased fibrinogen adsorption, but had almost no effect on albumin adsorption. Platelets adhesion and activation were suppressed significantly (97% for 4 mA NiTi) and hemolysis rate was decreased by at least 57% after Hf implantation. Modified surface composition and morphology and decreased surface energy should be responsible for the improvement of cytocompatibility and hemocompatibility. Copyright © 2011 Wiley Periodicals, Inc.

  14. Acid-base characterization, coordination properties towards copper(II) ions and DNA interaction studies of ribavirin, an antiviral drug.

    Science.gov (United States)

    Nagaj, Justyna; Starosta, Radosław; Jeżowska-Bojczuk, Małgorzata

    2015-01-01

    We have studied processes of copper(II) ion binding by ribavirin, an antiviral agent used in treating hepatitis C, which is accompanied usually by an increased copper level in the serum and liver tissue. Protonation equilibria and Cu(II) binding were investigated using the UV-visible, EPR and NMR spectroscopic techniques as well as the DFT (density functional theory) calculations. The spectroscopic data suggest that the first complex is formed in the water solution at pH as low as 0.5. In this compound Cu(II) ion is bound to one of the nitrogen atoms from the triazole ring. Above pH6.0, the metal ion is surrounded by two nitrogen and two oxygen atoms from two ligand molecules. The DFT calculations allowed to determine the exact structure of this complex. We found that in the lowest energy isomer two molecules of the ligand coordinate via O and N4 atoms in trans positions. The hypothetical oxidative properties of the investigated system were also examined. It proved not to generate plasmid DNA scission products. However, the calf thymus (CT)-DNA binding studies showed that it reacts with ribavirin and its cupric complex. Moreover, the interaction with the complex is much more efficient. Copyright © 2014 Elsevier Inc. All rights reserved.

  15. The role of kinetic ion physics in the interaction of magnetic islands

    Science.gov (United States)

    Stanier, A.

    2016-12-01

    Magnetic islands are two-dimensional representations of magnetic flux-ropes, a fundamental building block of magnetized plasmas. Here we model magnetic reconnection during the coalescence of magnetic islands with a range of guide fields that have application to the Earth's magnetosphere. It is demonstrated that the Hall-MHD model is able to reproduce the reconnection rates of the fully kinetic system only in the presence of a fairly strong guide field (Bg≥ 3Bx). In the weak guide field limit non-isotropic ion pressure tensor effects that are missing from Hall-MHD are crucial to describe many key features of this reconnection test-problem [1], including the peak and average rates, pile-up field, outflow velocity, and global evolution of the system. A hybrid model which retains the full kinetic physics for ions along with mass-less fluid electrons gives good agreement with fully kinetic results for the full range of guide fields considered. These results suggest that kinetic ions may be important for a large number of reconnection events in the Earth's magnetosphere. References: [1] A. Stanier, W. Daughton, L. Chacon, H. Karimabadi, J. Ng, Y.-M. Huang, A. Hakim, and A. Bhattacharjee, Phys. Rev. Lett. 115, 175004 (2015).

  16. Gamma ray interaction with vanadyl ions in barium metaphosphate glasses; spectroscopic and ESR studies

    Science.gov (United States)

    Abdelghany, A. M.; ElBatal, H. A.; EzzElDin, F. M.

    2017-11-01

    Optical, FTIR, ESR investigations of prepared undoped barium metaphosphate glass and other samples with the same basic composition containing varying V2O5 contents (0.5, 1, 2, 3%) were carried out before and after gamma irradiation. The undoped glass shows a strong UV optical absorption which is correlated with unavoidable contaminated trace iron impurities. The V2O5-doped samples reveal two additional strong broad visible bands centered at 450 and 680 nm. Such extra peculiar and strong two broad visible bands are related to both tetravalent and trivalent vanadium ions in measurable percent due to the reducing behavior of barium phosphate host glass. Gamma irradiation on the undoped glass results in the generation of collective induced UV and visible bands which are originating from positive hole and electron centers. Glasses containing V2O5 reveal upon gamma irradiation induced defects in the UV as the undoped sample together with distinct splitting within the first broad visible band while the second broad band remains unchanged. This behavior is related to limited photoionization upon the addition of V2O5 indicating specific shielding effect of the vanadium ions towards gamma irradiation. It was noticed that irradiation causes no distinct variations in the FTIR spectra due to the presence of 50% of heavy metal oxide (BaO) and some shielding effect of vanadium ions.

  17. A shape memory hydrogel induced by the interactions between metal ions and phosphate.

    Science.gov (United States)

    Yasin, Akram; Li, Huazhen; Lu, Zhao; ur Rehman, Saif; Siddiq, Mohammad; Yang, Haiyang

    2014-02-21

    A novel ferric-phosphate induced shape memory (SM) hydrogel is prepared by the one-step copolymerization of isopropenyl phosphonic acid (IPPA) and acrylamide (AM) in the presence of a crosslinker polyethylene glycol diacrylate (PEGDA). Different from the traditional SM hydrogels, our SM hydrogel can be processed into various shapes as needed and recovers to its original form in ‘multiconditions’ such as in the presence of a reducing agent or in the presence of a competitive complexing agent. This unique feature is attributed to the fact that the oxidized ferric ions show a high complexation ability with phosphate groups of IPPA, which acts as a physical crosslinker to form the secondary networks within the hydrogels to induce the shape memory effect. The memory behavior was totally reversible, owing to Fe3+ that can be reduced to Fe2+ and extracted by the complexing agent. Particularly, the SM hydrogels exhibit controllable and good mechanical characteristics by introduction of the ferric ions, i.e., the elastic modulus can increase from 2 kPa to 70 kPa dramatically. Learning from biological systems, phosphate-metal ion based hydrogels could become an attractive candidate for various biomedical and environmental applications.

  18. In silico assessment of interaction of sea anemone toxin APETx2 and acid sensing ion channel 3

    Energy Technology Data Exchange (ETDEWEB)

    Rahman, Taufiq, E-mail: mtur2@cam.ac.uk; Smith, Ewan St. John

    2014-07-18

    Highlights: • We have made a reasonable model of rat ASIC3 using published structure of chicken ASIC1. • We have docked sea anemone toxin APETx2 on the model. • We have identified two putative sites for toxin binding. • We have argued for plausibility one site over the other. • We have identified the residues that are likely to be critical for APETx2–ASIC3 interaction. - Abstract: Acid sensing ion channels (ASICs) are proton-gated cation channels that are expressed throughout the nervous system and have been implicated in mediating sensory perception of noxious stimuli. Amongst the six ASIC isoforms, ASIC1a, 1b, 2a and 3 form proton-gated homomers, which differ in their activation and inactivation kinetics, expression profiles and pharmacological modulation; protons do not gate ASIC2b and ASIC4. As with many other ion channels, structure-function studies of ASICs have been greatly aided by the discovery of some toxins that act in isoform-specific ways. ASIC3 is predominantly expressed by sensory neurons of the peripheral nervous system where it acts to detect acid as a noxious stimulus and thus plays an important role in nociception. ASIC3 is the only ASIC subunit that is inhibited by the sea anemone (Anthopleura elegantissima)-derived toxin APETx2. However, the molecular mechanism by which APETx2 interacts with ASIC3 remains largely unknown. In this study, we made a homology model of ASIC3 and used extensive protein–protein docking to predict for the first time, the probable sites of APETx2 interaction on ASIC3. Additionally, using computational alanine scanning, we also suggest the ‘hot-spots’ that are likely to be critical for ASIC3–APETx2 interaction.

  19. Basic investigations of electrostatic turbulence and its interaction with plasma and suprathermal ions in a simple magnetized toroidal plasma

    Science.gov (United States)

    Fasoli, A.; Avino, F.; Bovet, A.; Furno, I.; Gustafson, K.; Jolliet, S.; Loizu, J.; Malinverni, D.; Ricci, P.; Riva, F.; Theiler, C.; Spolaore, M.; Vianello, N.

    2013-06-01

    Progress in basic understanding of turbulence and its influence on the transport both of the plasma bulk and of suprathermal components is achieved in the TORPEX simple magnetized torus. This configuration combines a microwave plasma production scheme with a quasi-equilibrium generated by a toroidal magnetic field, onto which a small vertical component is superimposed, simulating a simplified form of tokamak scrape-off layers. After having clarified the formation of blobs in ideal interchange turbulence, TORPEX experiments elucidated the mechanisms behind the blob motion, with a general scaling law relating their size and speed. The parallel currents associated with the blobs, responsible for the damping of the charge separation that develops inside them, hence determining their cross-field velocity, have been measured. The blob dynamics is influenced by creating convective cells with biased electrodes, arranged in an array on a metal limiter. Depending on the biasing scheme, radial and vertical blob velocities can be varied. Suprathermal ion transport in small-scale turbulence is also investigated on TORPEX. Suprathermal ions are generated by a miniaturized lithium source, and are detected using a movable double-gridded energy analyser. We characterize vertical and radial spreading of the ion beam, associated with the ideal interchange-dominated plasma turbulence, as a function of the suprathermal ion energy and the plasma temperature. Experimental results are in good agreement with global fluid simulations, including in cases of non-diffusive behaviour. To investigate the interaction of plasma and suprathermal particles with instabilities and turbulence in magnetic configurations of increasing complexity, a closed field line configuration has recently been implemented on TORPEX, based on a current-carrying wire suspended in the vacuum chamber. First measurements indicate the creation of circular symmetric profiles centred on the magnetic axis, and instabilities

  20. Diverse wave-particle interactions for energetic ions that traverse Alfvén eigenmodes on their first full orbit

    Energy Technology Data Exchange (ETDEWEB)

    Heidbrink, W. W.; Persico, E. A. D. [University of California Irvine, Irvine, California 92697 (United States); Austin, M. E. [University of Texas, Austin, Texas 78705 (United States); Chen, Xi; Pace, D. C.; Van Zeeland, M. A. [General Atomics, San Diego, California 92186 (United States)

    2016-02-15

    Neutral-beam ions that are deflected onto loss orbits by Alfvén eigenmodes (AE) on their first bounce orbit and are detected by a fast-ion loss detector (FILD) satisfy the “local resonance” condition proposed by Zhang et al. [Nucl. Fusion 55, 22002 (2015)]. This theory qualitatively explains FILD observations for a wide variety of AE-particle interactions. When coherent losses are measured for multiple AE, oscillations at the sum and difference frequencies of the independent modes are often observed in the loss signal. The amplitudes of the sum and difference peaks correlate weakly with the amplitudes of the fundamental loss-signal amplitudes but do not correlate with the measured mode amplitudes. In contrast to a simple uniform-plasma theory of the interaction [Chen et al., Nucl. Fusion 54, 083005 (2014)], the loss-signal amplitude at the sum frequency is often larger than the loss-signal amplitude at the difference frequency, indicating a more detailed computation of the orbital trajectories through the mode eigenfunctions is needed.

  1. Quantitative EPR study on free radicals in the natural polyphenols interacting with metal ions and other environmental pollutants

    Science.gov (United States)

    Jezierski, Adam; Czechowski, Franciszek; Jerzykiewicz, Maria; Golonka, Iwona; Drozd, Jerzy; Bylinska, Ewa; Chen, Yona; Seaward, Mark R. D.

    2002-04-01

    Quantitative electron paramagnetic resonance (EPR) method was applied to characterise radicals stabilised in polyphenolic matrices of various biogenic materials: lichens, mosses, composts, soils, peats, brown coals and sewage sludge sediments. The investigations were carried out on raw materials and extracted fractions of humic acids (HA). General trends of g value and spin concentration changes were found. These parameters in lichens strongly depend on lichen species and air pollution. Determination of the g value and semiquinone spin concentration allows to assess degree of transformation of organic matter in compost, soil, peat and lignite. Application of gaseous ammonia as a base penetrating the organic matrices extends the possibilities and usefulness of the method. Interaction of metal ions with humic materials is illustrated by interaction of VO 2+ ion with peat and lignite HA as well as demineralised (raw and carbonised) brown coal. Our investigations demonstrate that quantitative EPR is a rapid and effective monitoring method to study the influence of various environmental factors on substances containing polyphenolic matrices.

  2. Experimental study and modeling of the influence of mixed electrolytes on adsorption of macromolecules on a hydrophobic resin.

    Science.gov (United States)

    Werner, Albert; Hasse, Hans

    2013-11-08

    The influence of mixed electrolytes on the adsorption of macromolecules on a hydrophobic resin is explored. The macromolecules are native lysozyme, di-PEG-lysozyme-5kDa and pure PEG-6kDa, the adsorbent is Toyopearl PPG-600M, a mildly hydrophobic resin. The solvent is a 25 mM aqueous sodium phosphate buffer at pH 7.0 containing additional salts with an overall ionic strength of 3000 mM. The studied salts are sodium chloride, ammonium sulfate, sodium sulfate and ammonium chloride. Both pure salts as well as binary and ternary mixtures of these salts with varying ratios of the amounts of the salts are studied. For all solvents adsorption equilibrium isotherms are measured at 25°C. Mixing electrolytes can lead to synergetic effects, i.e. the adsorption in the mixed electrolyte system is sometimes distinctly larger than expected from the results of the single electrolyte systems. The single ions, not the salts, drive the adsorption. A mathematical model is developed, which describes the influence of the different ions and their cross-interactions on the studied adsorption process. Copyright © 2013 Elsevier B.V. All rights reserved.

  3. Using ion exchange chromatography to purify a recombinantly expressed protein.

    Science.gov (United States)

    Duong-Ly, Krisna C; Gabelli, Sandra B

    2014-01-01

    Ion exchange chromatography (IEX) separates molecules by their surface charge, a property that can vary vastly between different proteins. There are two types of IEX, cation exhange and anion exchange chromatography. The protocol that follows was designed by the authors for anion exchange chromatography of a recombinantly expressed protein having a pI of 4.9 and containing two cysteine residues and one tryptophan residue, using an FPLC system. Prior to anion exchange, the protein had been salted out using ammonium sulfate precipitation and partially purified via hydrophobic interaction chromatography (see Salting out of proteins using ammonium sulfate precipitation and Use and Application of Hydrophobic Interaction Chromatography for Protein Purification). Slight modifications to this protocol may be made to accommodate both the protein of interest and the availability of equipment. © 2014 Elsevier Inc. All rights reserved.

  4. Guanidinium Toxins and Their Interactions with Voltage-Gated Sodium Ion Channels

    Directory of Open Access Journals (Sweden)

    Lorena M. Durán-Riveroll

    2017-10-01

    Full Text Available Guanidinium toxins, such as saxitoxin (STX, tetrodotoxin (TTX and their analogs, are naturally occurring alkaloids with divergent evolutionary origins and biogeographical distribution, but which share the common chemical feature of guanidinium moieties. These guanidinium groups confer high biological activity with high affinity and ion flux blockage capacity for voltage-gated sodium channels (NaV. Members of the STX group, known collectively as paralytic shellfish toxins (PSTs, are produced among three genera of marine dinoflagellates and about a dozen genera of primarily freshwater or brackish water cyanobacteria. In contrast, toxins of the TTX group occur mainly in macrozoa, particularly among puffer fish, several species of marine invertebrates and a few terrestrial amphibians. In the case of TTX and analogs, most evidence suggests that symbiotic bacteria are the origin of the toxins, although endogenous biosynthesis independent from bacteria has not been excluded. The evolutionary origin of the biosynthetic genes for STX and analogs in dinoflagellates and cyanobacteria remains elusive. These highly potent molecules have been the subject of intensive research since the latter half of the past century; first to study the mode of action of their toxigenicity, and later as tools to characterize the role and structure of NaV channels, and finally as therapeutics. Their pharmacological activities have provided encouragement for their use as therapeutants for ion channel-related pathologies, such as pain control. The functional role in aquatic and terrestrial ecosystems for both groups of toxins is unproven, although plausible mechanisms of ion channel regulation and chemical defense are often invoked. Molecular approaches and the development of improved detection methods will yield deeper understanding of their physiological and ecological roles. This knowledge will facilitate their further biotechnological exploitation and point the way towards

  5. Towards hot electron mediated charge exchange in hyperthermal energy ion-surface interactions

    DEFF Research Database (Denmark)

    Ray, M. P.; Lake, R. E.; Thomsen, Lasse Bjørchmar

    2010-01-01

    We have made Na + and He + ions incident on the surface of solid state tunnel junctions and measured the energy loss due to atomic displacement and electronic excitations. Each tunnel junction consists of an ultrathin film metal–oxide–semiconductor device which can be biased to create a band of hot...... shows that the primary energy loss mechanism is the atomic displacement of Au atoms in the thin film of the metal–oxide–semiconductor device. We propose that neutral particle detection of the scattered flux from a biased device could be a route to hot electron mediated charge exchange....

  6. Probing the hydrophobic effect of noncovalent complexes by mass spectrometry.

    Science.gov (United States)

    Bich, Claudia; Baer, Samuel; Jecklin, Matthias C; Zenobi, Renato

    2010-02-01

    The study of noncovalent interactions by mass spectrometry has become an active field of research in recent years. The role of the different noncovalent intermolecular forces is not yet fully understood since they tend to be modulated upon transfer into the gas phase. The hydrophobic effect, which plays a major role in protein folding, adhesion of lipid bilayers, etc., is absent in the gas phase. Here, noncovalent complexes with different types of interaction forces were investigated by mass spectrometry and compared with the complex present in solution. Creatine kinase (CK), glutathione S-transferase (GST), ribonuclease S (RNase S), and leucine zipper (LZ), which have dissociation constants in the nM range, were studied by native nanoelectrospray mass spectrometry (nanoESI-MS) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) combined with chemical cross-linking (XL). Complexes interacting with hydrogen bonds survived the transfer into gas phase intact and were observed by nanoESI-MS. Complexes that are bound largely by the hydrophobic effect in solution were not detected or only at very low intensity. Complexes with mixed polar and hydrophobic interactions were detected by nanoESI-MS, most likely due to the contribution from polar interactions. All noncovalent complexes could easily be studied by XL MALDI-MS, which demonstrates that the noncovalently bound complexes are conserved, and a real "snap-shot" of the situation in solution can be obtained. 2010 American Society for Mass Spectrometry. Published by Elsevier Inc. All rights reserved.

  7. Interaction mechanism for energy transfer from Ce to Tb ions in silica

    Energy Technology Data Exchange (ETDEWEB)

    Seed Ahmed, H.A.A. [Department of Physics, University of the Free State, Bloemfontein (South Africa); Department of Physics, University of Khartoum, Khartoum (Sudan); Chae, W.S. [Korea Basic Science Institute (KBSI), Gangneung (Korea, Republic of); Ntwaeaborwa, O.M. [Department of Physics, University of the Free State, Bloemfontein (South Africa); Kroon, R.E., E-mail: KroonRE@ufs.ac.za [Department of Physics, University of the Free State, Bloemfontein (South Africa)

    2016-01-01

    Energy transfer phenomena can play an important role in the development of luminescent materials. In this study, numerical simulations based on theoretical models of non-radiative energy transfer are compared to experimental results for Ce, Tb co-doped silica. Energy transfer from the donor (Ce) to the acceptor (Tb) resulted in a decrease in the Ce luminescence intensity and lifetime. The decrease in intensity corresponded best with the energy transfer models based on the exchange interaction and the dipole-dipole interaction. The critical transfer distance obtained from the fitting using both these models is around 2 nm. Since the exchange interaction requires a distance shorter than 1 nm to occur, the mechanism most likely to account for the energy transfer is concluded to be the dipole–dipole interaction. This is supported by an analysis of the lifetime data.

  8. Utilizing ion-pairing hydrophilic interaction chromatography solid phase extraction for efficient glycopeptide enrichment in glycoproteomics

    DEFF Research Database (Denmark)

    Mysling, Simon; Palmisano, Giuseppe; Højrup, Peter

    2010-01-01

    Glycopeptide enrichment is a prerequisite to enable structural characterization of protein glycosylation in glycoproteomics. Here we present an improved method for glycopeptide enrichment based on zwitter-ionic hydrophilic interaction chromatography solid phase extraction (ZIC-HILIC SPE...

  9. Microbial cell surface characteristics: Elucidating attachment/detachment using hydrophobicity and electrokinetic measurements

    Science.gov (United States)

    The surface properties of microorganisms play an important role in their behavior within the environment. Electrophoretic mobility and cell surface hydrophobicity of bacterial cells influence their initial interaction with surfaces and mediate their stability within an aqueous su...

  10. Hydrogen cold plasma for synthesizing Pd/C catalysts: the effect of support–metal ion interaction

    Science.gov (United States)

    Zhuang, LI; Xiuling, ZHANG; Yuzhuo, ZHANG; Dongzhi, DUAN; Lanbo, DI

    2018-01-01

    It has been found that cold plasma is a facile and environmentally benign method for synthesizing supported metal catalysts, and great efforts have been devoted to enlarging its applications. However, little work has been done to disclose the influence mechanism, which is significant for controllable synthesis. In this work, hydrogen cold plasma was adopted to synthesize a palladium catalyst supported on activated carbon (Pd/C-P) using H2PdCl4 as a Pd precursor followed by calcination in hydrogen gas to remove the chlorine ions. The Pd/C-P catalyst was found to be made of larger Pd nanoparticles showing a decreased migration to the support outer surface than that prepared by the conventional thermal hydrogen reduction method (Pd/C-C). Meanwhile, the pore diameter of the activated carbon support is small (∼4 nm). Therefore, Pd/C-P exhibits lower CO oxidation activity than Pd/C-C. It was proposed that the strong interaction between the activated carbon and {{{{PdCl}}}4}2-, and the enhanced metal–support interaction caused by hydrogen cold plasma reduction made it difficult for Pd nanoparticles to migrate to the support outer surface. The larger-sized Pd nanoparticles for Pd/C-P may be due to the Coulomb interaction resulting in the disturbance of the metal–support interaction. This work has important guiding significance for the controllable synthesis of supported metal catalysts by hydrogen cold plasma.

  11. A novel cell-scale bio-nanogenerator based on electron-ion interaction for fast light power conversion.

    Science.gov (United States)

    Li, Yu-Tao; Tian, He; Zhao, Hai-Ming; Jian, Mu-Qiang; Lv, Yu-Jia; Tian, Ye; Wang, Qian; Yang, Yi; Xiang, Yan; Zhang, Yingying; Ren, Tian-Ling

    2018-01-03

    Natural energy haversting devices serve as an alternative candidate for power supply in many micro-/nano-systems. However, traditional nanogenerators based on piezoelectricity or triboelectric power generation face challenges in terms of biocompatibility and stability in various biological systems. The bacteriorhodopsin (bR) protein in Halobacterium halobium is an ideal biocompatible material for photoelectric conversion. Conventional bR systems based on ion transport or enhanced light absorption layers have a limited light power conversion speed. On the other hand, bR-based biohybrid devices have a great potential for sensitive light power conversion as compared to conventional nanogenerators. Herein, we present a biohybrid nanogenerator made of bR and horizontally aligned-long carbon nanotubes (CNTs) with electron-ion interaction for the first time for sensitive light power conversion. The bR layer serves as the proton pump, whereas CNTs are utilized to enhance the photocurrent; thus, the photocurrent frequency response improves significantly because of the effect of the electron-ion interaction. The photocurrent shows a linear relationship with the intensity of light and can still obtain a stable signal at a light intensity of 0.03 mW cm-2. With regard to the influence of the light on-off period, the photocurrent initially increases and then decreases with an increase in flickering frequency up to 360 Hz; this can be ascribed to the combinational influence of light switch speed and photocycle decay time. The photocurrent shows highest value (99 nA cm-2) at a frequency of about 50 Hz at a light intensity of 0.43 mW cm-2, which matches well with the frequency standard of the electrical power supply system. Moreover, we found that a higher density of CNTs contributed to improve performance of the nanogenerators. Furthermore, a H+ ion releasing model was proposed to interpret the operating mechanism of the biohybrid nanogenerator. The biohybrid nanogenerator shows

  12. [Thermodynamic approach to the selection of polyuronide sequestrants for the protection of the human body from toxic metal ions. Interactions of polyuronides with strontium and calcium ions].

    Science.gov (United States)

    Braudo, E E; Danilova, I V; Dianova, V T; Kobak, V V; Plashchina, I G

    2001-01-01

    Selectivity of polyuronide sequestrants (pectate, alginates of various uronide composition) in respect to Sr2+ and Ca2+ ions has been evaluated in terms of thermodynamic affinity. It is suggested that there is no point in the use of pectate as a Sr(2+)-binding agent because at initial stages of reaction it reveals higher affinity to Ca2+ ions in comparison to Sr2+ ions. Contrary to pectate, alginates under similar conditions have higher affinity to Sr2+ ions. It is shown that these ions are bound only by blocks of L-guluronic acid residues in alginate macromolecules. The results obtained lend support to the advisability of the use of alginate preparations with the high content of L-guluronic acid residues for the excretion of Sr2+ ions from human body.

  13. Mechanism of negative ion formation from phenol and para-chlorophenol by interaction with free electrons

    Science.gov (United States)

    Muftakhov; Khatymov; Mazunov

    2000-01-01

    Dissociative electron attachment (DEA) to phenol and para-chlorophenol in the energy range 0-12 eV is studied. Analogies in formation of the resonance states in an ionic benzene and its derivatives are found to arise from the similarity of the aromatic base of the molecules. Differences in DEA processes are defined mainly by the influence of the functional OH-group and, to a lesser degree, by the presence of a chlorine atom. A correlation between the energies of the resonance states and ionization energies of p-chlorophenol and phenol, analogous to that found previously for phenol, is proved. On this basis it is established that the dominating mechanism for formation of molecular negative ions at energies above 5 eV is Feshbach resonance.Copyright 2000 John Wiley & Sons, Ltd.

  14. Interaction of powerful hot plasma and fast ion streams with materials in dense plasma focus devices

    Energy Technology Data Exchange (ETDEWEB)

    Chernyshova, M., E-mail: maryna.chernyshova@ipplm.pl [Institute of Plasma Physics and Laser Microfusion, Warsaw (Poland); Gribkov, V.A. [Institute of Plasma Physics and Laser Microfusion, Warsaw (Poland); Institution of Russian Academy of Sciences A.A. Baikov Institute of Metallurgy and Material Science RAS, Moscow (Russian Federation); Kowalska-Strzeciwilk, E.; Kubkowska, M.; Miklaszewski, R.; Paduch, M.; Pisarczyk, T.; Zielinska, E. [Institute of Plasma Physics and Laser Microfusion, Warsaw (Poland); Demina, E.V.; Pimenov, V.N.; Maslyaev, S.A. [Institution of Russian Academy of Sciences A.A. Baikov Institute of Metallurgy and Material Science RAS, Moscow (Russian Federation); Bondarenko, G.G. [National Research University Higher School of Economics (HSE), Moscow (Russian Federation); Vilemova, M.; Matejicek, J. [Institute of Plasma Physics of the CAS, Prague (Czech Republic)

    2016-12-15

    Highlights: • Materials perspective for use in mainstream nuclear fusion facilities were studied. • Powerful streams of hot plasma and fast ions were used to induce irradiation. • High temporal, spatial, angular and spectral resolution available in experiments. • Results of irradiation were investigated by number of analysis techniques. - Abstract: A process of irradiating and ablating solid-state targets with hot plasma and fast ion streams in two Dense Plasma Focus (DPF) devices – PF-6 and PF-1000 was examined by applying a number of diagnostics of nanosecond time resolution. Materials perspective for use in chambers of the mainstream nuclear fusion facilities (mainly with inertial plasma confinement like NIF and Z-machine), intended both for the first wall and for constructions, have been irradiated in these simulators. Optical microscopy, SEM, Atomic Emission Spectroscopy, images in secondary electrons and in characteristic X-ray luminescence of different elements, and X-ray elemental analysis, gave results on damageability for a number of materials including low-activated ferritic and austenitic stainless steels, β-alloy of Ti, as well as two types of W and a composite on its base. With an increase of the number of shots irradiating the surface, its morphology changes from weakly pronounced wave-like structures or ridges to strongly developed ones. At later stages, due to the action of the secondary plasma produced near the target materials they melted, yielding both blisters and a fracturing pattern: first along the grain and then “in-between” the grains creating an intergranular net of microcracks. At the highest values of power flux densities multiple bubbles appeared. Furthermore, in this last case the cracks were developed because of microstresses at the solidification of melt. Presence of deuterium within the irradiated ferritic steel surface nanolayers is explained by capture of deuterons in lattice defects of the types of impurity atoms

  15. Synthesis and characterization of hydrophobically modified xanthan

    OpenAIRE

    Roy, Audrey

    2015-01-01

    Hydrophobically modified polysaccharides show unusual rheological and interfacial properties in solution due to the self association of hydrophobic entities grafted onto their hydrophilic backbone. Their properties are tunable according to some well known parameters, such as the length of the hydrophobic moieties or the grafting density. However, very few studies deal with the influence of the backbone conformation on the properties of such systems in solution. Therefore, the objective of thi...

  16. Ligand binding induces a sharp decrease in hydrophobicity of folate binding protein assessed by 1-anilinonaphthalene-8-sulphonate which suppresses self-association of the hydrophobic apo-protein

    DEFF Research Database (Denmark)

    Holm, Jan; Lawaetz, Anders Juul; Hansen, Steen I.

    2012-01-01

    decrease of the surface hydrophobicity associated with the ligand-induced conformation change of FBP, and protein-inter-protein interactions involved in self-association of hydrophobic apo-FBP. The extrinsic fluorescent apolar dye 1-anilinonaphthalene-8-sulphonate (ANS) exhibited enhanced fluorescence...... decrease in surface hydrophobicity of holo-FBP could have bearings on the biological function of FBP since changes in surface hydrophobicity have critical effects on the biological function of receptors and transport proteins. ANS interacts with exposed hydrophobic surfaces on proteins and may thereby...... intensity and a blueshift of emission maximum from 510-520 nm to 460-470 nm upon addition of apo-FBP indicating binding to a strongly hydrophobic environment. Neither enhancement of fluorescence nor blueshift of ANS emission maximum occurred when folate-ligated holo-FBP replaced apo-FBP. The drastic...

  17. A new numerical description of the interaction of an ion beam with a magnetized plasma in an ECR-based charge breeding device

    Science.gov (United States)

    Galatà, A.; Mascali, D.; Neri, L.; Celona, L.

    2016-08-01

    The ion beam-plasma interaction is a relevant topic in several fields of plasma physics, from fusion devices to modern ion sources. This paper discusses the numerical modelling of the whole beam-plus-plasma-target system in case of 1+  ions entering an ECR-based charge breeder (ECR-CB). The model is able to reproduce the ion capture and the creation of the first charge states in the selected physics case, i.e. the interaction of a 85Rb1+ ions with the plasma of the 14.5 GHz PHOENIX ECR-CB installed at the Laboratoire de Physique Subatomique et de Cosmologie (LPSC) of Grenoble. The results show that a very narrow window of physical parameters for both the beam (energy and energy spread especially) and plasma (ion temperature, density, density structural distribution, self-generated ambipolar fields) exists which is able to reproduce very well the experimental results, providing an exhaustive picture of the involved phenomena. Possible non-linear interactions and the role played by the eventual onset of instabilities are also discussed.

  18. Separation of polythionates and the gold thiosulfate complex in gold thiosulfate leach solutions by ion-interaction chromatography.

    Science.gov (United States)

    O'Reilly, John W; Shaw, Matthew J; Dicinoski, Greg W; Grosse, Andrew C; Miura, Yasuyuki; Haddad, Paul R

    2002-07-01

    A method for the separation of the polythionates (SxO6(2-), x = 3-5) in gold thiosulfate leach solutions using ion-interaction chromatography with conductivity and ultraviolet (UV) detection is described. Polythionates were eluted within 18 min using an eluent comprising an acetonitrile step gradient at 0.0 min from 15% v/v to 28% v/v, 3 mM TBAOH, and 2.5 mM sodium carbonate, operated using a Dionex NS1-5 micron column with guard. The developed method was capable of separating the gold thiosulfate complex ion in standard solutions, but quantification of this species in realistic leach solutions proved impractical due to a self-elution effect that caused the gold peak to be eluted as a broad band. Detection limits for polythionates using a 10 microL injection volume ranged between 1-6 mg L(-1) (5-23 microM) for conductivity and 0.8-13 mg L(-1) (4-68 microM) for UV detection, based on a signal-to-noise ratio of 2. Calibration was linear over the ranges 5-2000, 10-2000 and 25-2500 mg L(-1) for trithionate, tetrathionate and pentathionate, respectively. The technique was applied successfully to leach liquors containing 0.5 M ammonium thiosulfate, 2 M ammonia, 0.05 M copper sulfate and 20 % m/v gold ore.

  19. Structure/Function Analysis of Protein-Protein Interactions and Role of Dynamic Motions in Mercuric Ion Reductase

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Susan M.

    2005-05-18

    This report summarizes the activities and findings of our structure/function studies of the bacterial detoxification enzyme mercuric ion reductase. The objectives of the work were to obtain crystal structure information for the catalytic core of this enzyme, use the information to investigate the importance of specific parts of the enzyme to its function, and investigate the role of one domain of the enzyme in its function within cells. We describe the accomplishments towards these goals including many structures of the wild type and mutant forms of the enzyme that highlight its interactions with its Hg(II) substrate, elucidation of the role of the N-terminal domain in vitro and in vivo, and elucidation of the roles of at two conserved residues in the core in the mechanism of catalysis.

  20. X-Ray Spectroscopy: An Experimental Technique to Measure Charge State Distribution Right at the Ion-Solid Interaction

    CERN Document Server

    Sharma, Prashant

    2015-01-01

    Charge state distributions of $^{56}$Fe and $^{58}$Ni projectile ions passing through thin carbon foils have been studied in the energy range of 1.44 - 2.69 MeV/u using a novel method from the x-ray spectroscopy technique. Interestingly the charge state distribution in the bulk show Lorentzian behavior instead of usual Gaussian distribution. Further, different parameters of charge state distribution like mean charge state, distribution width and asymmetric parameter are determined and compared with the empirical calculations and ETACHA predictions. It is found that the x-ray measurement technique is appropriate to determine the mean charge state right at the interaction zone or in the bulk. Interestingly, empirical formalism predicts much lower projectile mean charge states compare to x-ray measurements which clearly indicate multi-electron capture from the target surface. The ETACHA predictions and experimental results are found to be comparable for energies $\\geq$ 2 MeV/u.

  1. Probing regA/RNA interactions using electrospray ionization-Fourier transform ion cyclotron resonance-mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C.; Tolic, L.P.; Hofstadler, S.A.; Harms, A.C.; Smith, R.D. [Pacific Northwest National Lab., Richland, WA (United States). Environmental Molecular Sciences Lab.; Kang, C.H. [Washington State Univ., Pullman, WA (United States). Dept. of Biochemistry and Biophysics; Sinha, N. [Boston Biosystems, Inc., Bedford, MA (United States)

    1998-08-15

    The interactions of bacteriophage T4 regA protein, a unique translational regulator, with RNAs of various size and sequence were studied using electrospray ionization-Fourier transform ion cyclotron resonance-mass spectrometry. Using very gentle interface conditions, regA/RNA complexes with a 1:1 binding stoichiometry were observed for all four target RNAs studied, consistent with solution binding studies. Competitive binding of target RNAs and their degradation products with regA demonstrated that the loss of a single nucleotide resulted in a dramatic change in binding affinity in some cases. Competitive binding of regA with four target RNAs revealed similar relative binding affinity order to that suggested by previous in vitro repression experiments. The use of sustained off-resonance irradiation for collisionally induced dissociation of a regA/RNA complex suggested the potential for directly obtaining information regarding the regA binding domain.

  2. Applications of Frontal Affinity Chromatography to the Study of Interactions between Metal Ions and a Complex Biomaterial.

    Science.gov (United States)

    Lin, S; Drake, L R; Rayson, G D

    1996-12-01

    The use of frontal affinity chromatography for the study of metal-biomaterial interactions is described. Both normal frontal affinity chromatography and a modification of this methodology were used to generate metal binding isotherms to a biomaterial. This modification enabled the acquisition of binding isotherms with extended concentration ranges at the expense of time-dependent binding information. Comparison between normal and modified mode was made by using a well-defined commercial resin. Similar performance of these two modes was obtained. The biomaterial investigated was composed of cell fragments from the plant Datura innoxia which were immobilized within a polysilicate matrix. The application of a regularized least-squares method indicated the existence of two classes of sites on this biosorbent involved in the binding of Ag(+). A total metal-ion binding affinity order at solution pH 3-5 was determined to be Cu(2+) > Cd(2+) ≈ Ag(+) > Ca(2+).

  3. Hyperfine-interaction-driven suppression of quantum tunneling at zero field in a holmium(III) single-ion magnet

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yan-Cong; Liu, Jun-Liang; Chen, Xiao-Ming; Tong, Ming-Liang [Key Lab. of Bioinorganic and Synthetic Chemistry of Ministry of Education, School of Chemistry, Sun Yat-Sen Univ., Guangzhou (China); Wernsdorfer, Wolfgang [Institut Neel, CNRS and Universite Joseph Fournier, Grenoble (France); Institute of Nanotechnology, Karlsruhe Institute of Technology (Germany); Physikalisches Institut, Karlsruhe Institute of Technology (Germany); Liu, Dan; Chibotaru, Liviu F. [Theory of Nanomaterials Group and INPAC-Institute of Nanoscale Physics and Chemistry, Katholieke Universiteit Leuven (Belgium)

    2017-04-24

    An extremely rare non-Kramers holmium(III) single-ion magnet (SIM) is reported to be stabilized in the pentagonal-bipyramidal geometry by a phosphine oxide with a high energy barrier of 237(4) cm{sup -1}. The suppression of the quantum tunneling of magnetization (QTM) at zero field and the hyperfine structures originating from field-induced QTMs can be observed even from the field-dependent alternating-current magnetic susceptibility in addition to single-crystal hysteresis loops. These dramatic dynamics were attributed to the combination of the favorable crystal-field environment and the hyperfine interactions arising from {sup 165}Ho (I=7/2) with a natural abundance of 100 %. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. The impact of plasma-wall interaction on the gas mixing efficiency in electron cyclotron resonance ion source.

    Science.gov (United States)

    Schachter, L; Stiebing, K E; Dobrescu, S

    2012-02-01

    It is generally accepted that different effects are necessary to explain the gas mixing method of increasing the output of highly charged ions from an ECRIS. The two most important effects are the mass effect and the dilution effect. Their relative weights have not been determined experimentally yet, but it is generally assumed that the mass effect is dominant in standard ECRIS installations with stainless steel plasma chambers. In order to gain more insight into the physics of the gas mixing effect and in particular on the relevance of the dilution process, we have carried out a study where we have investigated the role of the plasma-wall interaction on the gas mixing effect. In this contribution, we shall discuss Charge state distributions spectra, measured at the Frankfurt ECRIS using different working gases, pure argon, a mixture of argon and oxygen, and argon mixed with neon.

  5. Interaction between coordinated metal ions and a metal substrate: Differently substituted cobalt porphyrins on Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Yun; Buchner, Florian; Schmid, Martin; Kellner, Ina; Vollnhals, Florian; Marbach, Hubertus; Steinrueck, Hans-Peter; Gottfried, J. Michael [Universitaet Erlangen-Nuernberg, Lehrstuhl fuer Physikalische Chemie II, Egerlandstr. 3, 91058 Erlangen (Germany)

    2009-07-01

    Adsorbed metalloporphyrins are of increasing interest due to their potential applications in heterogeneous catalysis and in sensor systems. Previous studies from our group have suggested the existence of an electronic interaction between the metal centers of the adsorbed porphyrin complexes of iron and cobalt and the underlying substrate surface, which plays an important role in modifying the electronic structure and, thereby, the reactivity of these metal centers. However, with the previously used tetraphenylporphyrin (TPP) ligands, the adsorbed complexes undergo saddle-shape distortion, which could also influence the electronic structure. To separate the effects of distortion on the one hand and the coupling to the substrate on the other, we have studied cobalt octaethylporphyrin, which adsorbs in a flat, undistorted conformation on Ag(111). Comparison of our XPS, UPS, and STM results with previous CoTPP data confirms that indeed the metal center plays an essential role in the electronic interaction between the porphyrin complexes and the substrate.

  6. Excessive production of electron pairs by soft photons in low multiplicity ion interactions

    Science.gov (United States)

    Burnett, T. H.; Dake, S.; Fuki, M.; Gregory, J. C.; Hayashi, T.; Holynski, R.; Iwai, J.; Jones, W. V.; Jurak, A.; Lord, J. J.

    1985-01-01

    Three multiply charged primary cosmic ray interactions with carbon nuclei are reported, in which the number of materialized electron pairs within a distance of about 0.3 conversion length is larger than predicted from isospin considerations. These are the most energetic (sigma E gamma 4 TeV) of the low multiplicity ( 15 tracks) events observed in the Japanese-American Cooperative Experiment (JACEE-2) emulsion chamber.

  7. Polymerization Effect of Electrolytes on Hydrogen-Bonding Cryoprotectants: Ion–Dipole Interactions between Metal Ions and Glycerol

    Science.gov (United States)

    2015-01-01

    Protectants which are cell membrane permeable, such as glycerol, have been used effectively in the cryopreservation field for a number of decades, for both slow cooling and vitrification applications. In the latter case, the glass transition temperature (Tg) of the vitrification composition is key to its application, dictating the ultimate storage conditions. It has been observed that the addition of some electrolytes to glycerol, such as MgCl2, could elevate the Tg of the mixture, thus potentially providing more storage condition flexibility. The microscopic mechanisms that give rise to the Tg-enhancing behavior of these electrolytes are not yet well understood. The current study focuses on molecular dynamics simulation of glycerol mixed with a variety of metal chlorides (i.e., NaCl, KCl, MgCl2, and CaCl2), covering a temperature range that spans both the liquid and glassy states. The characteristics of the ion–dipole interactions between metal cations and hydroxyl groups of glycerol were analyzed. The interruption of the original hydrogen-bonding network among glycerol molecules by the addition of ions was also investigated in the context of hydrogen-bonding quantity and lifetime. Divalent metal cations were found to significantly increase the Tg by strengthening the interacting network in the electrolyte/glycerol mixture via strong cation–dipole attractions. In contrast, monovalent cations increased the Tg insignificantly, as the cation–dipole attraction was only slightly stronger than the original hydrogen-bonding network among glycerol molecules. The precursor of crystallization of NaCl and KCl was also observed in these compositions, potentially contributing to weak Tg-enhancing ability. The Tg-enhancing mechanisms elucidated in this study suggest a structure-enhancing role for divalent ions that could be of benefit in the design of protective formulations for biopreservation purposes. PMID:25405831

  8. Case study of hydrogen bonding in a hydrophobic cavity.

    Science.gov (United States)

    Chen, Yi-Chen; Cheng, Chao-Sheng; Tjong, Siu-Cin; Yin, Hsien-Sheng; Sue, Shih-Che

    2014-12-18

    Protein internal hydrogen bonds and hydrophobicity determine protein folding and structure stabilization, and the introduction of a hydrogen bond has been believed to represent a better interaction for consolidating protein structure. We observed an alternative example for chicken IL-1β. The native IL-1β contains a hydrogen bond between the Y157 side-chain OηH and I133 backbone CO, whereby the substitution from Tyr to Phe abolishes the connection and the mutant without the hydrogen bond is more stable. An attempt to explain the energetic view of the presence of the hydrogen bond fails when only considering the nearly identical X-ray structures. Here, we resolve the mechanism by monitoring the protein backbone dynamics and interior hydrogen bond network. IL-1β contains a hydrophobic cavity in the protein interior, and Y157 is one of the surrounding residues. The Y157 OηH group introduces an unfavorable energy in the hydrophobic cavity, therefore sequestering itself by forming a hydrogen bond with the proximate residue I133. The hydrogen bonding confines Y157 orientation but exerts a force to disrupt the hydrogen bond network surrounding the cavity. The effect propagates over the entire protein and reduces the stability, as reflected in the protein backbone dynamics observed by an NMR hydrogen-deuterium (H/D) exchange experiment. We describe the particular case in which a hydrogen bond does not necessarily confer enhanced protein stability while the disruption of hydrophobicity must be integrally considered.

  9. Electric polarization and the viability of living systems: ion cyclotron resonance-like interactions.

    Science.gov (United States)

    Liboff, A R

    2009-01-01

    Wellness can be described in physical terms as a state that is a function of the organism's electric polarization vector P(r, t). One can alter P by invasive application of electric fields or by non invasive external pulsed magnetic fields (PMF) or ion cyclotron resonance (ICR)-like combinations of static and sinusoidal magnetic fields. Changes in human (total) body bioimpedance are significantly altered during exposure to ICR magnetic field combinations. The conductivities of polar amino acids in solution exhibit sharp discontinuities at ICR magnetic fields tuned to the specific charge to mass ratio of the amino acid. It has been reported that protein peptide bonds are broken by such amino acid ICR fields. Remarkably, some of these effects are only found at ultra-low AC magnetic intensities, on the order of .05 muT. This is approximately 10(3) below accepted levels determined by engineering estimates. Such strikingly low magnetic intensities imply the existence of physically equivalent endogenous weak electric field oscillations. These observations not only make claims related to electromagnetic pollution more credible but also provide a basis for future electromagnetic applications in medicine. They also reinforce the notion that physical factors acting to influence the electric polarization in living organisms play a key role in biology.

  10. Targeting of the hydrophobic metabolome by pathogens.

    Science.gov (United States)

    Helms, J Bernd; Kaloyanova, Dora V; Strating, Jeroen R P; van Hellemond, Jaap J; van der Schaar, Hilde M; Tielens, Aloysius G M; van Kuppeveld, Frank J M; Brouwers, Jos F

    2015-05-01

    The hydrophobic molecules of the metabolome - also named the lipidome - constitute a major part of the entire metabolome. Novel technologies show the existence of a staggering number of individual lipid species, the biological functions of which are, with the exception of only a few lipid species, unknown. Much can be learned from pathogens that have evolved to take advantage of the complexity of the lipidome to escape the immune system of the host organism and to allow their survival and replication. Different types of pathogens target different lipids as shown in interaction maps, allowing visualization of differences between different types of pathogens. Bacterial and viral pathogens target predominantly structural and signaling lipids to alter the cellular phenotype of the host cell. Fungal and parasitic pathogens have complex lipidomes themselves and target predominantly the release of polyunsaturated fatty acids from the host cell lipidome, resulting in the generation of eicosanoids by either the host cell or the pathogen. Thus, whereas viruses and bacteria induce predominantly alterations in lipid metabolites at the host cell level, eukaryotic pathogens focus on interference with lipid metabolites affecting systemic inflammatory reactions that are part of the immune system. A better understanding of the interplay between host-pathogen interactions will not only help elucidate the fundamental role of lipid species in cellular physiology, but will also aid in the generation of novel therapeutic drugs. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  11. The in vitro antimicrobial activity of Cymbopogon essential oil (lemon grass) and its interaction with silver ions.

    Science.gov (United States)

    Ahmad, Aijaz; Viljoen, Alvaro

    2015-06-01

    It is well known that Cymbopogon (lemon grass) essential oil exhibits antimicrobial activity while the efficacy of silver ions as a disinfectant is equally well reported. The antimicrobial activity of CEO and Ag(+) and their synergistic combinations will be useful in improving the current treatment strategies for various infections. In the present study, we determined the chemical composition and in vitro antimicrobial activity of six different Cymbopogon essential oils (CEO's) alone and in combination with silver ions (Ag(+)) against two Gram-positive (Staphylococcus aureus and Enterococcus faecalis), two Gram-negative (Escherichia coli and Moraxella catarrhalis) and two yeast species (Candida albicans and Candida tropicalis). The nature of potential interactions was determined by fractional inhibitory concentration indices (FICIs) for CEO's and Ag(+) calculated from microdilution assays and time-kill curves. Gas chromatography-mass spectrometry results confirmed the presence of nerol, geranial and geraniol as major volatile compounds. Minimum inhibitory concentration (MIC) values confirmed that all the tested pathogens are variably susceptible to both CEO's as well as Ag(+). The MIC of CEO's and Ag(+) against all the tested pathogens ranged from 0.032 mg/ml to 1 mg/ml and 0.004 and 0.064 mg/ml respectively, whereas when assayed in combination the FICI values were drastically reduced to range between 0.258 and 2.186, indicating synergy, additive and indifferent interactions. The most prominent interaction was observed between Cymbopogon flexuosus essential oil and Ag(+) against C. albicans with ∑FIC = 0.254. The synergistic interactions were further confirmed through the construction of isobolograms and time-kill plots. Transmission electron microscopy showed disturbance in the cell envelope upon the concomitant treatment of CEO's and Ag(+), which ultimately leads to cell death. Results suggest that CEO's and Ag(+) when used in combination offers an opportunity

  12. Infrared Spectroscopy of Metal Ion Complexes: Models for Metal Ligand Interactions and Solvation

    Science.gov (United States)

    Duncan, Michael

    2006-03-01

    Weakly bound complexes of the form M^+-Lx (M=Fe, Ni, Co, etc.; L=CO2, C2H2, H2O, benzene, N2) are prepared in supersonic molecular beams by laser vaporization in a pulsed-nozzle cluster source. These species are mass analyzed and size-selected in a reflectron time-of-flight mass spectrometer. Clusters are photodissociated at infrared wavelengths with a Nd:YAG pumped infrared optical parametric oscillator/amplifier (OPO/OPA) laser or with a tunable infrared free-electron laser. M^+-(CO2)x complexes absorb near the free CO2 asymmetric stretch near 2349 cm-1 but with an interesting size dependent variation in the resonances. Small clusters have blue-shifted resonances, while larger complexes have additional bands due to surface CO2 molecules not attached to the metal. M^+(C2H2)n complexes absorb near the C-H stretches in acetylene, but resonances in metal complexes are red-shifted with repect to the isolated molecule. Ni^+ and Co^+ complexes with acetylene undergo intracluster cyclization reactions to form cyclobutadiene. Transition metal water complexes are studied in the O-H stretch region, and partial rotational structure can be measured. M^+(benzene) and M^+(benzene)2 ions (M=V, Ti, Al) represent half-sandwich and sandwich species, whose spectra are measured near the free benzene modes. These new IR spectra and their assignments will be discussed as well as other new IR spectra for similar complexes.

  13. Colloid properties of hydrophobic modified alginate: Surface tension, ζ-potential, viscosity and emulsification.

    Science.gov (United States)

    Wu, Zongmei; Wu, Jie; Zhang, Ruling; Yuan, Shichao; Lu, Qingliang; Yu, Yueqin

    2018-02-01

    Micelle properties of hydrophobic modified alginate (HM-alginate) in various dispersion media have been studied by surface tension, ζ-potential, and viscosity measurements. Effect of salt on micelle properties showed that the presence of counter ion weakened the repulsive interaction between surfactant ions, decreased the critical micelle concentration (CMC) value of the HM-alginate, reduced the effective volume dimensions of HM-alginate and hence viscosity, which coincide with the corresponding ζ-potential values. Soy oil-in-water emulsions, stabilized solely by HM-alginate, were produced in high speed homogenization conditions and their stability properties were studied by visual inspection, optical microscopy and droplet size measurements. The results showed that emulsions (oil-water ratio was 1:7) containing 15mg/mL HM-alginate presented better stability during 15days storage, which stating clearly that HM-alginate is an effective emulsifier to stabilize oil-in-water emulsions. The herein presented homogeneous method for preparation of emulsion has the potential to be used in food industry. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Reaction mechanisms and their interaction time in dissipative heavy-ion collisions

    Energy Technology Data Exchange (ETDEWEB)

    De Rosa, A.; Fioretto, E.; Inglima, G.; Romoli, M.; Sandoli, M.; Setola, R. (Dipartimento di Scienze Fisiche Universita di Napoli Federico II Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, Pad. 20 Mostra d' Oltremare, Napoli, (Italy)); Cardella, G.; Papa, M.; Pappalardo, G.; Rizzo, F.; Wang, Q. (Dipartimento di Fisica Universita di Catania Istituto Nazionale di Fisica Nucleare, Sezione di Catania, Corso Italia, 57 Catania, (Italy)); Napoli, D.R.; Scarlassara, F.; Segato, G.F.; Signorini, C.; Stefanini, A.M. (Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, Legnaro, Padova, (Italy))

    1990-05-01

    Angular distributions of fragments emitted in the reaction {sup 19}F+{sup 63}Cu measured in the range {theta}{sub lab}=10{degree} to 120{degree} at incident energy between 100 to 108 MeV (lab) have been analyzed according to available models for deep inelastic collisions with the aim to evidence different mechanisms contributing to such reactions. The analysis was performed in the framework of Strutinsky model taking into account both the development of Kun and of Abul-Magd and Simbel. To determine the interaction times, previously published excitation functions were also analyzed in the framework of Kun's model of cross section statistical fluctuations and near-side and far-side scattering were taken into account separately. It was pointed out that the rotational energy dissipation occurs in a limited angular range around the grazing angle. The presence of two distinct reaction mechanisms, each of them characterized by an interaction time, was also evidenced by comparing the energy averaged angular distributions to the Abul-Magd and Simbel model for dissipative collisions.

  15. Studies of nuclear matter under extreme conditions: Heavy-ion interactions at ultra-relativistic energies

    Energy Technology Data Exchange (ETDEWEB)

    Nystrand, J.

    1996-10-01

    The charged particle production in ultra-relativistic nucleus-nucleus collisions in the energy range 4-200 A GeV has been studied. Two different experimental techniques have been utilized: nuclear emulsions and multi-step avalanche chambers. The performance of the chambers in the experiment as well as the analysis of the chamber data are described in the thesis. The reconstructed particle momenta have been used to study transverse momentum distribution of negatively charged particles, and to perform intensity interferometry analyses in order to determine the source size and study the time-evolution of the interactions. Multiplicity and pseudorapidity distributions of singly charged particles obtained from interactions in nuclear emulsion have been studied. Simulations have been performed with various Monte-Carlo models, and particularly the effects of the hadronic rescattering have been studied. The results of the analysis have illustrated the great importance of the nuclear geometry in ultra-relativistic nucleus-nucleus collisions. Based on gaussian parametrizations a method of predicting the pseudorapidity distributions in systems of different sizes and at different energies has been developed. Furthermore, the multiplicity and angular distributions of slow, target associated particles have been analyzed. 99 refs, 19 figs.

  16. Characterization of the interaction of uranyl ions with humic acids by x-ray absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Reich, T.; Denecke, M.A.; Pompe, S. [Inst. of Radiochemistry, Dresden (Germany)] [and others

    1995-11-01

    Humic substances are present throughout the environment in soil and natural water. They are organic macromolecules with a variable structural formula, molecular weight, and a wide variety of functional groups depending on their origin. In natural waters, humic substances represent the main component of the {open_quotes}dissolved organic carbon{close_quotes} (DOC). The DOC may vary considerably from 1 mg/L at sea water surfaces to 50 mg/L at the surface in dark water swamps. There is strong evidence that all actinides form complexes with humic substances in natural waters. Therefore, humic substances can play an important role in the environmental migration of radionuclides by enhancing their transport. Retardation through humic substance interaction may be also possible due to formation of precipitating agglomerates. For remediation and restoration of contaminated environmental sites and risk assessment of future nuclear waste repositories, it is important to improve the predictive capabilities for radionuclide migration through a better understanding of the interaction of radionuclides with humic substances.

  17. Physical and functional interaction of KV10.1 with Rabaptin-5 impacts ion channel trafficking.

    Science.gov (United States)

    Ninkovic, Milena; Mitkovski, Mišo; Kohl, Tobias; Stühmer, Walter; Pardo, Luis A

    2012-09-21

    K(V)10.1 is a potassium channel expressed in brain and implicated in tumor progression. We have searched for proteins interacting with K(V)10.1 and identified Rabaptin-5, an effector of the Rab5 GTPase. Both proteins co-localize on large early endosomes induced by Rab5 hyperactivity. Silencing of Rabaptin-5 induces down-regulation of recycling of K(V)10.1 channel in transfected cells and reduction of K(V)10.1 current density in cells natively expressing K(V)10.1, indicating a role of Rabaptin-5 in channel trafficking. K(V)10.1 co-localizes, but does not physically interact, with Rab7 and Rab11. Our data highlights the complex control of the amount of K(V)10.1 channels on the cell surface. Copyright © 2012 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

  18. Durability of hydrophobic treatment of concrete

    NARCIS (Netherlands)

    Vries, J. de; Polder, R.B.; Borsje, H.

    1998-01-01

    The subject of this study was the performance of hydrophobic treatment to protect concrete against chloride penetration from de-icing salts. Hydrophobic treatment makes a concrete surface absorb less water and less chloride. Several types of tests were carried out to study the performance of