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Sample records for randomly crosslinked macromolecular

  1. Computer simulation of randomly cross-linked polymer networks

    International Nuclear Information System (INIS)

    Williams, Timothy Philip

    2002-01-01

    In this work, Monte Carlo and Stochastic Dynamics computer simulations of mesoscale model randomly cross-linked networks were undertaken. Task parallel implementations of the lattice Monte Carlo Bond Fluctuation model and Kremer-Grest Stochastic Dynamics bead-spring continuum model were designed and used for this purpose. Lattice and continuum precursor melt systems were prepared and then cross-linked to varying degrees. The resultant networks were used to study structural changes during deformation and relaxation dynamics. The effects of a random network topology featuring a polydisperse distribution of strand lengths and an abundance of pendant chain ends, were qualitatively compared to recent published work. A preliminary investigation into the effects of temperature on the structural and dynamical properties was also undertaken. Structural changes during isotropic swelling and uniaxial deformation, revealed a pronounced non-affine deformation dependant on the degree of cross-linking. Fractal heterogeneities were observed in the swollen model networks and were analysed by considering constituent substructures of varying size. The network connectivity determined the length scales at which the majority of the substructure unfolding process occurred. Simulated stress-strain curves and diffraction patterns for uniaxially deformed swollen networks, were found to be consistent with experimental findings. Analysis of the relaxation dynamics of various network components revealed a dramatic slowdown due to the network connectivity. The cross-link junction spatial fluctuations for networks close to the sol-gel threshold, were observed to be at least comparable with the phantom network prediction. The dangling chain ends were found to display the largest characteristic relaxation time. (author)

  2. Macromolecular therapeutics.

    Science.gov (United States)

    Yang, Jiyuan; Kopeček, Jindřich

    2014-09-28

    This review covers water-soluble polymer-drug conjugates and macromolecules that possess biological activity without attached low molecular weight drugs. The main design principles of traditional and backbone degradable polymer-drug conjugates as well as the development of a new paradigm in nanomedicines - (low molecular weight) drug-free macromolecular therapeutics are discussed. To address the biological features of cancer, macromolecular therapeutics directed to stem/progenitor cells and the tumor microenvironment are deliberated. Finally, the future perspectives of the field are briefly debated. Copyright © 2014 Elsevier B.V. All rights reserved.

  3. Collagen macromolecular drug delivery systems

    International Nuclear Information System (INIS)

    Gilbert, D.L.

    1988-01-01

    The objective of this study was to examine collagen for use as a macromolecular drug delivery system by determining the mechanism of release through a matrix. Collagen membranes varying in porosity, crosslinking density, structure and crosslinker were fabricated. Collagen characterized by infrared spectroscopy and solution viscosity was determined to be pure and native. The collagen membranes were determined to possess native vs. non-native quaternary structure and porous vs. dense aggregate membranes by electron microscopy. Collagen monolithic devices containing a model macromolecule (inulin) were fabricated. In vitro release rates were found to be linear with respect to t 1/2 and were affected by crosslinking density, crosslinker and structure. The biodegradation of the collagen matrix was also examined. In vivo biocompatibility, degradation and 14 C-inulin release rates were evaluated subcutaneously in rats

  4. [Prevention of intrauterine adhesion with auto-crosslinked hyaluronic acid gel: a prospective, randomized, controlled clinical study].

    Science.gov (United States)

    Xiao, Songshu; Wan, Yajun; Zou, Fangjun; Ye, Mingzhu; Deng, Henan; Ma, Jiezhi; Wei, Yingying; Tan, Chen; Xue, Min

    2015-01-01

    To evaluate the efficacy and safety of auto-crosslinked hyaluronic acid (HA) gel for preventing intrauterine adhesion (IUA) after hysteroscopic adhesiolysis. A prospective, randomized, double blinded and controlled clinical trial (level I) was performed. According to American Fertility Society (AFS) scoring system, 120 patients (treatment group: 60 cases, control group: 60 cases) with moderate to severe IUA were enrolled. Upon completion of adhesiolysis, a Foley balloon catheter was first introduced into the uterine cavity and then 3 ml of auto-crosslinked HA gel for patients in the treatment group; patients in the control group, however, only received Foley balloon catheter. Second-look hysteroscopic examination was performed to all patients at 3 months postoperatively for evaluation of IUA. Primary endpoint was the reduction rate of IUA at 3 months after surgery. The secondary endpoints include total AFS score, score of each individual AFS category. At 3 months after surgery, auto-crosslinked HA gel resulted in significantly higher effective rate for reduction of adhesion, the effective rate were 76% (42/55) and 48% (27/56) respectively (P = 0.000 9); the total AFS score of treatment group was 2.1 ± 1.1, and significantly lower than that of control group (3.7 ± 2.5, P = 0.000 8). Application of auto-crosslinked HA gel after surgery significantly enhanced the improvement for each individual patient with regard to their adhesive type and menstrual pattern (P = 0.037 8, P = 0.000 4). The treatment group had significantly lower proportion of patients with moderate to severe adhesive stages than that of control group [13% (7/55) versus 38% (21/56), P = 0.000 6]. No adverse events and complications were observed. Auto-crosslinked HA gel coule be able to reduce IUA, decrease adhesion severity, and improve menopause postoperatively. This absorbable auto-crosslinked HA gel is proposed as a barrier for preventing IUA after intrauterine procedures.

  5. Compartmentalization Technologies via Self-Assembly and Cross-Linking of Amphiphilic Random Block Copolymers in Water.

    Science.gov (United States)

    Matsumoto, Mayuko; Terashima, Takaya; Matsumoto, Kazuma; Takenaka, Mikihito; Sawamoto, Mitsuo

    2017-05-31

    Orthogonal self-assembly and intramolecular cross-linking of amphiphilic random block copolymers in water afforded an approach to tailor-make well-defined compartments and domains in single polymer chains and nanoaggregates. For a double compartment single-chain polymer, an amphiphilic random block copolymer bearing hydrophilic poly(ethylene glycol) (PEG) and hydrophobic dodecyl, benzyl, and olefin pendants was synthesized by living radical polymerization (LRP) and postfunctionalization; the dodecyl and benzyl units were incorporated into the different block segments, whereas PEG pendants were statistically attached along a chain. The copolymer self-folded via the orthogonal self-assembly of hydrophobic dodecyl and benzyl pendants in water, followed by intramolecular cross-linking, to form a single-chain polymer carrying double yet distinct hydrophobic nanocompartments. A single-chain cross-linked polymer with a chlorine terminal served as a globular macroinitiator for LRP to provide an amphiphilic tadpole macromolecule comprising a hydrophilic nanoparticle and a hydrophobic polymer tail; the tadpole thus self-assembled into multicompartment aggregates in water.

  6. Practical macromolecular cryocrystallography

    Energy Technology Data Exchange (ETDEWEB)

    Pflugrath, J. W., E-mail: jim.pflugrath@gmail.com [Rigaku Americas Corp., 9009 New Trails Drive, The Woodlands, TX 77381 (United States)

    2015-05-27

    Current methods, reagents and experimental hardware for successfully and reproducibly flash-cooling macromolecular crystals to cryogenic temperatures for X-ray diffraction data collection are reviewed. Cryocrystallography is an indispensable technique that is routinely used for single-crystal X-ray diffraction data collection at temperatures near 100 K, where radiation damage is mitigated. Modern procedures and tools to cryoprotect and rapidly cool macromolecular crystals with a significant solvent fraction to below the glass-transition phase of water are reviewed. Reagents and methods to help prevent the stresses that damage crystals when flash-cooling are described. A method of using isopentane to assess whether cryogenic temperatures have been preserved when dismounting screened crystals is also presented.

  7. Macromolecular crystallization in microgravity

    International Nuclear Information System (INIS)

    Snell, Edward H; Helliwell, John R

    2005-01-01

    Density difference fluid flows and sedimentation of growing crystals are greatly reduced when crystallization takes place in a reduced gravity environment. In the case of macromolecular crystallography a crystal of a biological macromolecule is used for diffraction experiments (x-ray or neutron) so as to determine the three-dimensional structure of the macromolecule. The better the internal order of the crystal then the greater the molecular structure detail that can be extracted. It is this structural information that enables an understanding of how the molecule functions. This knowledge is changing the biological and chemical sciences, with major potential in understanding disease pathologies. In this review, we examine the use of microgravity as an environment to grow macromolecular crystals. We describe the crystallization procedures used on the ground, how the resulting crystals are studied and the knowledge obtained from those crystals. We address the features desired in an ordered crystal and the techniques used to evaluate those features in detail. We then introduce the microgravity environment, the techniques to access that environment and the theory and evidence behind the use of microgravity for crystallization experiments. We describe how ground-based laboratory techniques have been adapted to microgravity flights and look at some of the methods used to analyse the resulting data. Several case studies illustrate the physical crystal quality improvements and the macromolecular structural advances. Finally, limitations and alternatives to microgravity and future directions for this research are covered. Macromolecular structural crystallography in general is a remarkable field where physics, biology, chemistry and mathematics meet to enable insight to the fundamentals of life. As the reader will see, there is a great deal of physics involved when the microgravity environment is applied to crystallization, some of it known, and undoubtedly much yet to

  8. In situ crosslinking of surface-initiated ring opening metathesis polymerization of polynorbornene for improved stability.

    Science.gov (United States)

    Fursule, Ishan A; Abtahi, Ashkan; Watkins, Charles B; Graham, Kenneth R; Berron, Brad J

    2018-01-15

    In situ crosslinking is expected to increase the solvent stability of coatings formed by surface-initiated ring opening metathesis polymerization (SI ROMP). Solvent-associated degradation limits the utility of SI ROMP coatings. SI ROMP coatings have a unique capacity for post-functionalization through reaction of the unsaturated site on the polymer backbone. Any post-reaction scheme which requires a liquid solvent has the potential to degrade the coating and lower the thickness of the resulting film. We designed a macromolecular crosslinking group based on PEG dinorbornene. The PEG length is tailored to the expected mean chain to chain distance during surface-initiated polymerization. This crosslinking macromer is randomly copolymerized with norbornene through SI ROMP on a gold coated substrate. The solvent stability of polynorbornene coatings with and without PEG dinorbornene is quantitatively determined, and the mechanism of degradation is further supported through XPS and AFM analyses. The addition of the 0.25mol% PEG dinorbornene significantly increases the solvent stability of the SI ROMP coatings. The crosslinker presence in the more stable films is supported with observable PEG absorbances by FTIR and an increase in contact angle hysteresis when compared to non-crosslinked coatings. The oxidation of the SI ROMP coatings is supported by the observation of carbonyl oxygen in the polynorbornene coatings. The rapid loss of the non-crosslinked SI ROMP coating corresponds to nanoscale pitting across the surface and micron-scale regions of widespread film loss. The crosslinked coatings have uniform nanoscale pitting, but the crosslinked films show no evidence of micron-scale film damage. In all, the incorporation of minimal crosslinking content is a simple strategy for improving the solvent stability of SI ROMP coatings. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. Macromolecular crystallography using synchrotron radiation

    International Nuclear Information System (INIS)

    Bartunik, H.D.; Phillips, J.C.; Fourme, R.

    1982-01-01

    The use of synchrotron X-ray sources in macromolecular crystallography is described. The properties of synchrotron radiation relevant to macromolecular crystallography are examined. The applications discussed include anomalous dispersion techniques, the acquisition of normal and high resolution data, and kinetic studies of structural changes in macromolecules; protein data are presented illustrating these applications. The apparatus used is described including information on the electronic detectors, the monitoring of the incident beam and crystal cooling. (U.K.)

  10. Design of polymer networks by variation of precursor structure and crosslinking regime

    Czech Academy of Sciences Publication Activity Database

    Dušek, Karel; Dušková, Miroslava; Huybrecht, J.

    2003-01-01

    Roč. 44, č. 1 (2003), s. 62-63 ISSN 0032-3934. [ACS National Meeting "Crosslinking Materials and Processes"/254./. New Orleans, 23.03.2003-27.03.2003] R&D Projects: GA AV ČR KSK4050111 Keywords : polymer networks * designed precursor * crosslinking Subject RIV: CD - Macromolecular Chemistry

  11. Crosslinking of epoxy-oligoesteric mixtures in the presence of dioxydiphenylpropane diglycidyl ether modified with adipic acid

    Czech Academy of Sciences Publication Activity Database

    Bratychak, M.; Zubal, O.; Bashta, Bogdana; Ivashkiv, O.; Shyshchak, O.; Haponiuk, J.

    2017-01-01

    Roč. 11, č. 2 (2017), s. 180-187 ISSN 1996-4196 Institutional support: RVO:61389013 Keywords : crosslinking * polymer films * epoxy resin Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science

  12. Swelling of cross-linked polymers: interpretations and misinterpretations

    Czech Academy of Sciences Publication Activity Database

    Dušek, Karel; Dušková-Smrčková, Miroslava

    2017-01-01

    Roč. 254, 20 August (2017), s. 102 ISSN 0065-7727. [ACS National Meeting & Exposition /254./. 20.08.2017-24.08.2017, Washington] Institutional support: RVO:61389013 Keywords : swelling * cross-linked polymer Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science

  13. Recent advances in macromolecular prodrugs

    DEFF Research Database (Denmark)

    Riber, Camilla Frich; Zelikin, Alexander N.

    2017-01-01

    Macromolecular prodrugs (MP) are high molar mass conjugates, typically carrying several copies of a drug or a drug combination, designed to optimize delivery of the drug, that is — its pharmacokinetics. From its advent several decades ago, design of MP has undergone significant development and es...

  14. Higher order optical aberrations and visual acuity in a randomized controlled trial comparing transepithelial versus epithelium-off corneal crosslinking for progressive keratoconus

    Directory of Open Access Journals (Sweden)

    Godefrooij DA

    2017-10-01

    Full Text Available Daniel A Godefrooij, Mustapha El Kandoussi, Nienke Soeters, Robert PL Wisse Utrecht Cornea Research Group, Department of Ophthalmology, University Medical Center Utrecht, Utrecht, the Netherlands Purpose: The purpose of this study was to compare the effects of transepithelial crosslinking (trans-CXL versus epithelium-off crosslinking (epi-off CXL for progressive keratoconus with respect to the development of higher order aberrations (HOAs and their effects on visual acuity.Materials and methods: A total of 61 patients were randomized and examined preoperatively and 1, 3, 6, and 12 months postoperatively in an academic referral center. Total corneal HOAs were compared between the two treatment groups using mixed linear modeling. Types of HOAs (coma, trefoil, and spherical aberration that differed between groups were entered in a multivariable analysis to test their effect on uncorrected distance visual acuity (UDVA and corrected distance visual acuity (CDVA.Results: The epi-off CXL group had more flattening in maximal keratometry compared to the trans-CXL group (P=0.02. UDVA did not differ significantly between the groups (P=0.59; however, CDVA was significantly more improved in the trans-CXL group (P=0.02. Horizontal trefoil improved more in the epi-off group compared to the trans-CXL group (P=0.04, whereas the other HOAs were virtually unchanged in both groups. Differences in changes in HOAs between the two groups had no effect on either UCVA (P=0.76 or CDVA (P=0.96.Conclusion: Although HOAs are clinically relevant determinants of vision quality in keratoconus patients, the change in total HOAs post treatment did not differ between the trans-CXL and epi-off CXL groups. Only horizontal trefoil differed significantly post treatment between the trans-CXL and epi-off CXL groups. However, this difference did not independently affect either UDVA or CDVA. Trans-CXL provides no benefit over epi-off CXL regarding visual relevant HOAs. Keywords

  15. Structure studies of macromolecular systems

    Czech Academy of Sciences Publication Activity Database

    Hašek, Jindřich; Dohnálek, Jan; Skálová, Tereza; Dušková, Jarmila; Kolenko, Petr

    2006-01-01

    Roč. 13, č. 3 (2006), s. 136 ISSN 1211-5894. [Czech and Slovak Crystallographic Colloquium. 22.06.2006-24.06.2006, Grenoble] R&D Projects: GA AV ČR IAA4050811; GA MŠk 1K05008 Keywords : structure * X-ray diffraction * synchrotron Subject RIV: CD - Macromolecular Chemistry http://www. xray .cz/ms/default.htm

  16. A Randomized Controlled Trial on the Efficacy and Safety of a New Crosslinked Hyaluronan Gel in Reducing Adhesions after Gynecologic Laparoscopic Surgeries.

    Science.gov (United States)

    Liu, Chongdong; Lu, Qi; Zhang, Zhiqiang; Xue, Min; Zhang, Youzhong; Zhang, Yi; Wang, Huilan; Li, Huajun; Zhou, Yingfang; Zhang, Zhenyu; Li, Wei

    2015-01-01

    To evaluate the safety and efficacy of a new crosslinked hyaluronan (NCH) gel in reducing postoperative adhesions. Randomized controlled trial (Canadian Task Force classification I). Seven departments of obstetrics and gynecology in China. A total of 216 women scheduled for gynecologic laparoscopic surgery for primary removal of adhesions, myomas, ovarian cysts, or endometriotic cysts. Patients were randomized to receive either NCH gel or saline with 1:1 allocation. All patients were evaluated using a modified American Fertility Society (mAFS) scoring system for the incidence, extent, and severity of pre-existing and postoperative adhesions at the 10 anatomic sites of ovaries/tubes and at the expanded 23 or 24 anatomic sites throughout the abdominopelvic cavity by laparoscopy. A total of 215 randomized patients were treated with either saline solution (108 of 108) or NCH gel (107 of 108), composing the full analysis set (FAS), and 196 patients (94 of 108 in the saline control group and 102 of 108 in the NCH gel group) completed the entire study, composing the per protocol set (PPS). The postoperative incidence of moderate or severe adhesions evaluated at the 10 sites (the primary endpoint for efficacy) was 27.7% in the control group and 9.8% in the NCH gel group, a difference of 14.4% (95% confidence interval [CI], 2.6%-20.6%) in the PPS, and 37.0% in the control group and 14.0% in the NCH gel group, a difference of 20.0% (95% CI, 8.9%-26.8%) in the FAS. The postoperative incidence of moderate or severe adhesions evaluated at the 24 sites was also significantly lower in the NCH gel group compared with the control group (5.9% vs 14.9%; p = .036) in the PPS. Also in the PPS, the NCH gel group had significantly lower postoperative adhesion scores of severity, extent, and mAFS: 60.0%, 50.8%, and 76.9%, respectively (median scores of the 10 sites; p = .002) and 48.5%, 50.0%, and 72.2% (median scores of the 24 sites; p = .001) lower than those recorded in the control

  17. The effect of an advanced glycation end-product crosslink breaker and exercise training on vascular function in older individuals: a randomized factorial design trial.

    NARCIS (Netherlands)

    Oudegeest-Sander, M.H.; Olde Rikkert, M.G.M.; Smits, P.; Thijssen, D.H.J.; Dijk, A.P.J. van; Levine, B.D.; Hopman, M.T.E.

    2013-01-01

    Aging leads to accumulation of irreversible advanced glycation end-products (AGEs), contributing to vascular stiffening and endothelial dysfunction. When combined with the AGE-crosslink breaker Alagebrium, exercise training reverses cardiovascular aging in experimental animals. This study is the

  18. Macromolecular systems for vaccine delivery.

    Science.gov (United States)

    MuŽíková, G; Laga, R

    2016-10-20

    Vaccines have helped considerably in eliminating some life-threatening infectious diseases in past two hundred years. Recently, human medicine has focused on vaccination against some of the world's most common infectious diseases (AIDS, malaria, tuberculosis, etc.), and vaccination is also gaining popularity in the treatment of cancer or autoimmune diseases. The major limitation of current vaccines lies in their poor ability to generate a sufficient level of protective antibodies and T cell responses against diseases such as HIV, malaria, tuberculosis and cancers. Among the promising vaccination systems that could improve the potency of weakly immunogenic vaccines belong macromolecular carriers (water soluble polymers, polymer particels, micelles, gels etc.) conjugated with antigens and immunistumulatory molecules. The size, architecture, and the composition of the high molecular-weight carrier can significantly improve the vaccine efficiency. This review includes the most recently developed (bio)polymer-based vaccines reported in the literature.

  19. Macromolecular crystallography research at Trombay

    International Nuclear Information System (INIS)

    Kannan, K.K.; Chidamrabam, R.

    1983-01-01

    Neutron diffraction studies of hydrogen positions in small molecules of biological interest at Trombay have provided valuable information that has been used in protein and enzyme structure model-building and in developing hydrogen bond potential functions. The new R-5 reactor is expected to provide higher neutron fluxes and also make possible small-angle neutron scattering studies of large biomolecules and bio-aggregates. In the last few years infrastructure facilities have also been established for macromolecular x-ray crystallography research. Meanwhile, the refinement of carbonic hydrases and lyysozyme structures have been carried out and interesting results obtained on protein dynamics and structure-function relationships. Some interesting presynaptic toxin phospholipases have also taken up for study. (author)

  20. The radiation crosslinking of ethylene copolymers

    International Nuclear Information System (INIS)

    Burns, N.M.

    1979-01-01

    The enhanced radiation crosslinking tendency of ethylene-vinyl acetate and ethylene-ethyl acrylate copolymers over ethylene homopolymer is proportional to the comonomer content. This is caused by an increase in the amorphous polymer content and by structure-related factors. The copolymers crosslink by a random process that for ethylene-vinyl acetate copolymer involves some crosslinking through the acetoxy group of the comonomer. While knowledge of the process for the crosslinking of ethylene-ethyl acrylate copolymer is less certain, it is currently believed to occur primarily at the branch point on the polymer backbone. Data relating comonomer content and the molecular weight of the copolymers to the radiation crosslinking levels realized were developed to aid in resin selection by the formulator. Triallyl cyanurate cure accelerator was found to be less effective in ethylene-vinyl acetate copolymer than in homopolymer and to have no effect on gel development in ethylene-ethyl acrylate copolymer. (author)

  1. Status and prospects of macromolecular crystallography

    Indian Academy of Sciences (India)

    technique that could be completely automated in most cases. ... major challenge in macromolecular crystallography today is ... tial characterization of crystals in the home source and make a ... opportunities for a generation of structural biolo-.

  2. Constrained swelling of polymer networks: characterization of vapor-deposited cross-linked polymer thin films

    Czech Academy of Sciences Publication Activity Database

    Dušek, Karel; Choukourov, A.; Dušková-Smrčková, Miroslava; Biederman, H.

    2014-01-01

    Roč. 47, č. 13 (2014), s. 4417-4427 ISSN 0024-9297 R&D Projects: GA ČR GAP101/12/1306 Institutional support: RVO:61389013 Keywords : swelling * cross-linked polymer * elasticity Subject RIV: CD - Macromolecular Chemistry Impact factor: 5.800, year: 2014

  3. Macromolecular synthesis in algal cells

    International Nuclear Information System (INIS)

    Ishida, M.R.; Kikuchi, Tadatoshi

    1980-01-01

    The present paper is a review of our experimental results obtained previously on the macromolecular biosyntheses in the cells of blue-green alga Anacystis nidulans as a representative species of prokaryote, and also in those of three species of eukaryotic algae, i.e. Euglena gracilis strain Z, Chlamydomonas reinhardi, and Cyanidium caldarium. In these algal cells, the combined methods consisting of pulse-labelling using 32 P, 3 H- and 14 C-labelled precursors for macromolecules, of their chasing and of the use of inhibitors which block specifically the syntheses of macromolecules such as proteins, RNA and DNA in living cells were very effectively applied for the analyses of the regulatory mechanism in biosyntheses of macromolecules and of the mode of their assembly into the cell structure, especially organelle constituents. Rased on the results obtained thus, the following conclusions are reached: (1) the metabolic pool for syntheses of macromolecules in the cells of prokaryotic blue-green alga is limited to the small extent and such activities couple largely with the photosynthetic mechanism; (2) 70 S ribosomes in the blue-green algal cells are assembled on the surface of thylakoid membranes widely distributed in their cytoplasm; and (3) the cells of eukaryotic unicellular algae used here have biochemical characters specific for already differentiated enzyme system involving in transcription and translation machineries as the same as in higher organisms, but the control mechanism concerning with such macromolecule syntheses are different among each species. (author)

  4. Topology evolution in macromolecular networks

    NARCIS (Netherlands)

    Kryven, I.

    2014-01-01

    Governed by various intermolecular forces, molecular networks tend to evolve from simple to very complex formations that have random structure. This randomness in the connectivity of the basic units can still be captured employing distributional description of the state of the system; the evolution

  5. The design of macromolecular crystallography diffraction experiments

    International Nuclear Information System (INIS)

    Evans, Gwyndaf; Axford, Danny; Owen, Robin L.

    2011-01-01

    Thoughts about the decisions made in designing macromolecular X-ray crystallography experiments at synchrotron beamlines are presented. The measurement of X-ray diffraction data from macromolecular crystals for the purpose of structure determination is the convergence of two processes: the preparation of diffraction-quality crystal samples on the one hand and the construction and optimization of an X-ray beamline and end station on the other. Like sample preparation, a macromolecular crystallography beamline is geared to obtaining the best possible diffraction measurements from crystals provided by the synchrotron user. This paper describes the thoughts behind an experiment that fully exploits both the sample and the beamline and how these map into everyday decisions that users can and should make when visiting a beamline with their most precious crystals

  6. Radiation crosslinking of polypropylene

    International Nuclear Information System (INIS)

    Nojiri, A.; Sawasaki, T.

    1984-01-01

    The radiation crosslinking of polypropylene with several kinds of polyfunctional monomers has been examined, and it has been clarified that the enhanced crosslinking may be classified into two types. In particular, the irradiation crosslinking process of polypropylene containing a polyfunctional monomer having an acryloyloxy group giving a specific gel - dose curve has been studied by infrared absorption spectrum and oxygen absorptivity measurement in comparison with the non-enhanced system. (author)

  7. Automated data collection for macromolecular crystallography.

    Science.gov (United States)

    Winter, Graeme; McAuley, Katherine E

    2011-09-01

    An overview, together with some practical advice, is presented of the current status of the automation of macromolecular crystallography (MX) data collection, with a focus on MX beamlines at Diamond Light Source, UK. Copyright © 2011 Elsevier Inc. All rights reserved.

  8. Macromolecular crowding-assisted fabrication of liquid-crystalline imprinted polymers.

    Science.gov (United States)

    Zhang, Chen; Zhang, Jing; Huang, Yan-Ping; Liu, Zhao-Sheng

    2015-04-01

    A macromolecular crowding-assisted liquid-crystalline molecularly imprinted monolith (LC-MIM) was prepared successfully for the first time. The imprinted stationary phase was synthesized with polymethyl methacrylate (PMMA) or polystyrene (PS) as the crowding agent, 4-cyanophenyl dicyclohexyl propylene (CPCE) as the liquid-crystal monomer, and hydroquinidine as the pseudo-template for the chiral separation of cinchona alkaloids in HPLC. A low level of cross-linker (26%) has been found to be sufficient to achieve molecular recognition on the crowding-assisted LC-MIM due to the physical cross-linking of mesogenic groups in place of chemical cross-linking, and baseline separation of quinidine and quinine could be achieved with good resolution (R(s) = 2.96), selectivity factor (α = 2.16), and column efficiency (N = 2650 plates/m). In contrast, the LC-MIM prepared without crowding agents displayed the smallest diastereoselectivity (α = 1.90), while the crowding-assisted MIM with high level of cross-linker (80%) obtained the greatest selectivity factor (α = 7.65), but the lowest column efficiency (N = 177 plates/m).

  9. In situ macromolecular crystallography using microbeams.

    Science.gov (United States)

    Axford, Danny; Owen, Robin L; Aishima, Jun; Foadi, James; Morgan, Ann W; Robinson, James I; Nettleship, Joanne E; Owens, Raymond J; Moraes, Isabel; Fry, Elizabeth E; Grimes, Jonathan M; Harlos, Karl; Kotecha, Abhay; Ren, Jingshan; Sutton, Geoff; Walter, Thomas S; Stuart, David I; Evans, Gwyndaf

    2012-05-01

    Despite significant progress in high-throughput methods in macromolecular crystallography, the production of diffraction-quality crystals remains a major bottleneck. By recording diffraction in situ from crystals in their crystallization plates at room temperature, a number of problems associated with crystal handling and cryoprotection can be side-stepped. Using a dedicated goniometer installed on the microfocus macromolecular crystallography beamline I24 at Diamond Light Source, crystals have been studied in situ with an intense and flexible microfocus beam, allowing weakly diffracting samples to be assessed without a manual crystal-handling step but with good signal to noise, despite the background scatter from the plate. A number of case studies are reported: the structure solution of bovine enterovirus 2, crystallization screening of membrane proteins and complexes, and structure solution from crystallization hits produced via a high-throughput pipeline. These demonstrate the potential for in situ data collection and structure solution with microbeams. © 2012 International Union of Crystallography

  10. Macromolecular Networks Containing Fluorinated Cyclic Moieties

    Science.gov (United States)

    2015-12-12

    Briefing Charts 3. DATES COVERED (From - To) 17 Nov 2015 – 12 Dec 2015 4. TITLE AND SUBTITLE Macromolecular Networks Containing Fluorinated Cyclic... FLUORINATED CYCLIC MOIETIES 12 December 2015 Andrew J. Guenthner,1 Scott T. Iacono,2 Cynthia A. Corley,2 Christopher M. Sahagun,3 Kevin R. Lamison,4...Reinforcements Good Flame, Smoke, & Toxicity Characteristics Low Water Uptake with Near Zero Coefficient of Hygroscopic Expansion ∆ DISTRIBUTION A

  11. Macromolecular nanotheranostics for multimodal anticancer therapy

    Science.gov (United States)

    Huis in't Veld, Ruben; Storm, Gert; Hennink, Wim E.; Kiessling, Fabian; Lammers, Twan

    2011-10-01

    Macromolecular carrier materials based on N-(2-hydroxypropyl)methacrylamide (HPMA) are prototypic and well-characterized drug delivery systems that have been extensively evaluated in the past two decades, both at the preclinical and at the clinical level. Using several different imaging agents and techniques, HPMA copolymers have been shown to circulate for prolonged periods of time, and to accumulate in tumors both effectively and selectively by means of the Enhanced Permeability and Retention (EPR) effect. Because of this, HPMA-based macromolecular nanotheranostics, i.e. formulations containing both drug and imaging agents within a single formulation, have been shown to be highly effective in inducing tumor growth inhibition in animal models. In patients, however, as essentially all other tumor-targeted nanomedicines, they are generally only able to improve the therapeutic index of the attached active agent by lowering its toxicity, and they fail to improve the efficacy of the intervention. Bearing this in mind, we have recently reasoned that because of their biocompatibility and their beneficial biodistribution, nanomedicine formulations might be highly suitable systems for combination therapies. In the present manuscript, we briefly summarize several exemplary efforts undertaken in this regard in our labs in the past couple of years, and we show that long-circulating and passively tumor-targeted macromolecular nanotheranostics can be used to improve the efficacy of radiochemotherapy and of chemotherapy combinations.

  12. A public database of macromolecular diffraction experiments.

    Science.gov (United States)

    Grabowski, Marek; Langner, Karol M; Cymborowski, Marcin; Porebski, Przemyslaw J; Sroka, Piotr; Zheng, Heping; Cooper, David R; Zimmerman, Matthew D; Elsliger, Marc André; Burley, Stephen K; Minor, Wladek

    2016-11-01

    The low reproducibility of published experimental results in many scientific disciplines has recently garnered negative attention in scientific journals and the general media. Public transparency, including the availability of `raw' experimental data, will help to address growing concerns regarding scientific integrity. Macromolecular X-ray crystallography has led the way in requiring the public dissemination of atomic coordinates and a wealth of experimental data, making the field one of the most reproducible in the biological sciences. However, there remains no mandate for public disclosure of the original diffraction data. The Integrated Resource for Reproducibility in Macromolecular Crystallography (IRRMC) has been developed to archive raw data from diffraction experiments and, equally importantly, to provide related metadata. Currently, the database of our resource contains data from 2920 macromolecular diffraction experiments (5767 data sets), accounting for around 3% of all depositions in the Protein Data Bank (PDB), with their corresponding partially curated metadata. IRRMC utilizes distributed storage implemented using a federated architecture of many independent storage servers, which provides both scalability and sustainability. The resource, which is accessible via the web portal at http://www.proteindiffraction.org, can be searched using various criteria. All data are available for unrestricted access and download. The resource serves as a proof of concept and demonstrates the feasibility of archiving raw diffraction data and associated metadata from X-ray crystallographic studies of biological macromolecules. The goal is to expand this resource and include data sets that failed to yield X-ray structures in order to facilitate collaborative efforts that will improve protein structure-determination methods and to ensure the availability of `orphan' data left behind for various reasons by individual investigators and/or extinct structural genomics

  13. Celebrating macromolecular crystallography: A personal perspective

    Directory of Open Access Journals (Sweden)

    Abad-Zapatero, Celerino

    2015-04-01

    Full Text Available The twentieth century has seen an enormous advance in the knowledge of the atomic structures that surround us. The discovery of the first crystal structures of simple inorganic salts by the Braggs in 1914, using the diffraction of X-rays by crystals, provided the critical elements to unveil the atomic structure of matter. Subsequent developments in the field leading to macromolecular crystallography are presented with a personal perspective, related to the cultural milieu of Spain in the late 1950’s. The journey of discovery of the author, as he developed professionally, is interwoven with the expansion of macromolecular crystallography from the first proteins (myoglobin, hemoglobin to the ‘coming of age’ of the field in 1971 and the discoveries that followed, culminating in the determination of the structure of the ribosomes at the turn of the century. A perspective is presented exploring the future of the field and also a reflection about the future generations of Spanish scientists.El siglo XX ha sido testigo del increíble avance que ha experimentado el conocimiento de la estructura atómica de la materia que nos rodea. El descubrimiento de las primeras estructuras atómicas de sales inorgánicas por los Bragg en 1914, empleando difracción de rayos X con cristales, proporcionó los elementos clave para alcanzar tal conocimiento. Posteriores desarrollos en este campo, que condujeron a la cristalografía macromolecular, se presentan aquí desde una perspectiva personal, relacionada con el contexto cultural de la España de la década de los 50. La experiencia del descubrimiento científico, durante mi desarrollo profesional, se integra en el desarrollo de la cristalografía macromolecular, desde las primeras proteínas (míoglobina y hemoglobina, hasta su madurez en 1971 que, con los posteriores descubrimientos, culmina con la determinación del la estructura del ribosoma. Asimismo, se explora el futuro de esta disciplina y se

  14. In situ macromolecular crystallography using microbeams

    Energy Technology Data Exchange (ETDEWEB)

    Axford, Danny; Owen, Robin L.; Aishima, Jun [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom); Foadi, James [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom); Imperial College, London SW7 2AZ (United Kingdom); Morgan, Ann W.; Robinson, James I. [University of Leeds, Leeds LS9 7FT (United Kingdom); Nettleship, Joanne E.; Owens, Raymond J. [Research Complex at Harwell, Rutherford Appleton Laboratory R92, Didcot, Oxfordshire OX11 0DE (United Kingdom); Moraes, Isabel [Imperial College, London SW7 2AZ (United Kingdom); Fry, Elizabeth E.; Grimes, Jonathan M.; Harlos, Karl; Kotecha, Abhay; Ren, Jingshan; Sutton, Geoff; Walter, Thomas S. [University of Oxford, Roosevelt Drive, Oxford OX3 7BN (United Kingdom); Stuart, David I. [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom); University of Oxford, Roosevelt Drive, Oxford OX3 7BN (United Kingdom); Evans, Gwyndaf, E-mail: gwyndaf.evans@diamond.ac.uk [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom)

    2012-04-17

    A sample environment for mounting crystallization trays has been developed on the microfocus beamline I24 at Diamond Light Source. The technical developments and several case studies are described. Despite significant progress in high-throughput methods in macromolecular crystallography, the production of diffraction-quality crystals remains a major bottleneck. By recording diffraction in situ from crystals in their crystallization plates at room temperature, a number of problems associated with crystal handling and cryoprotection can be side-stepped. Using a dedicated goniometer installed on the microfocus macromolecular crystallography beamline I24 at Diamond Light Source, crystals have been studied in situ with an intense and flexible microfocus beam, allowing weakly diffracting samples to be assessed without a manual crystal-handling step but with good signal to noise, despite the background scatter from the plate. A number of case studies are reported: the structure solution of bovine enterovirus 2, crystallization screening of membrane proteins and complexes, and structure solution from crystallization hits produced via a high-throughput pipeline. These demonstrate the potential for in situ data collection and structure solution with microbeams.

  15. In situ macromolecular crystallography using microbeams

    International Nuclear Information System (INIS)

    Axford, Danny; Owen, Robin L.; Aishima, Jun; Foadi, James; Morgan, Ann W.; Robinson, James I.; Nettleship, Joanne E.; Owens, Raymond J.; Moraes, Isabel; Fry, Elizabeth E.; Grimes, Jonathan M.; Harlos, Karl; Kotecha, Abhay; Ren, Jingshan; Sutton, Geoff; Walter, Thomas S.; Stuart, David I.; Evans, Gwyndaf

    2012-01-01

    A sample environment for mounting crystallization trays has been developed on the microfocus beamline I24 at Diamond Light Source. The technical developments and several case studies are described. Despite significant progress in high-throughput methods in macromolecular crystallography, the production of diffraction-quality crystals remains a major bottleneck. By recording diffraction in situ from crystals in their crystallization plates at room temperature, a number of problems associated with crystal handling and cryoprotection can be side-stepped. Using a dedicated goniometer installed on the microfocus macromolecular crystallography beamline I24 at Diamond Light Source, crystals have been studied in situ with an intense and flexible microfocus beam, allowing weakly diffracting samples to be assessed without a manual crystal-handling step but with good signal to noise, despite the background scatter from the plate. A number of case studies are reported: the structure solution of bovine enterovirus 2, crystallization screening of membrane proteins and complexes, and structure solution from crystallization hits produced via a high-throughput pipeline. These demonstrate the potential for in situ data collection and structure solution with microbeams

  16. Efficacy and safety of single injection of cross-linked sodium hyaluronate vs. three injections of high molecular weight sodium hyaluronate for osteoarthritis of the knee: a double-blind, randomized, multi-center, non-inferiority study.

    Science.gov (United States)

    Ha, Chul-Won; Park, Yong-Beom; Choi, Chong-Hyuk; Kyung, Hee-Soo; Lee, Ju-Hong; Yoo, Jae Doo; Yoo, Ju-Hyung; Choi, Choong-Hyeok; Kim, Chang-Wan; Kim, Hee-Chun; Oh, Kwang-Jun; Bin, Seong-Il; Lee, Myung Chul

    2017-05-26

    This randomized, double-blind, multi-center, non-inferiority trial was conducted to assess the efficacy and safety of a cross-linked hyaluronate (XLHA, single injection form) compared with a linear high molecular hyaluronate (HMWHA, thrice injection form) in patients with symptomatic knee osteoarthritis. Two hundred eighty seven patients with osteoarthritis (Kellgren-Lawrence grade I to III) were randomized to each group. Three weekly injections were given in both groups but two times of saline injections preceded XLHA injection to maintain double-blindness. Primary endpoint was the change of weight-bearing pain (WBP) at 12 weeks after the last injection. Secondary endpoints included Western Ontario and McMaster Universities Osteoarthritis index; patient's and investigator's global assessment; pain at rest, at night, or in motion; OMERACT-OARSI responder rate; proportion of patients achieving at least 20 mm or 40% decrease in WBP; and rate of rescue medicine use and its total consumption. Mean changes of WBP at 12 weeks after the last injection were -33.3 mm with XLHA and -29.2 mm with HMWHA, proving non-inferiority of XLHA to HMWHA as the lower bound of 95% CI (-1.9 mm, 10.1 mm) was well above the predefined margin (-10 mm). There were no significant between-group differences in all secondary endpoints. Injection site pain was the most common adverse event and no remarkable safety issue was identified. This study demonstrated that a single injection of XLHA was non-inferior to three weekly injections of HMWHA in terms of WBP reduction, and supports XLHA as an effective and safe treatment for knee osteoarthritis. ClinicalTrials.gov ( NCT01510535 ). This trial was registered on January 6, 2012.

  17. The role of macromolecular stability in desiccation tolerance

    NARCIS (Netherlands)

    Wolkers, W.F.

    1998-01-01

    The work presented in this thesis concerns a study on the molecular interactions that play a role in the macromolecular stability of desiccation-tolerant higher plant organs. Fourier transform infrared microspectroscopy was used as the main experimental technique to assess macromolecular

  18. Generalized Born Models of Macromolecular Solvation Effects

    Science.gov (United States)

    Bashford, Donald; Case, David A.

    2000-10-01

    It would often be useful in computer simulations to use a simple description of solvation effects, instead of explicitly representing the individual solvent molecules. Continuum dielectric models often work well in describing the thermodynamic aspects of aqueous solvation, and approximations to such models that avoid the need to solve the Poisson equation are attractive because of their computational efficiency. Here we give an overview of one such approximation, the generalized Born model, which is simple and fast enough to be used for molecular dynamics simulations of proteins and nucleic acids. We discuss its strengths and weaknesses, both for its fidelity to the underlying continuum model and for its ability to replace explicit consideration of solvent molecules in macromolecular simulations. We focus particularly on versions of the generalized Born model that have a pair-wise analytical form, and therefore fit most naturally into conventional molecular mechanics calculations.

  19. Radiation crosslinking of elastomers

    International Nuclear Information System (INIS)

    Pearson, D.S.

    1981-01-01

    In the first part of this paper a review is presented of recent results which show that the tensile strength and fatigue life of synthetic elastomers cured by radiation are essentially equivalent to those prepared by other crosslinking techniques. An explanation for the conflict of these new results with the earlier studies on natural rubber is presented. Investigations into the mechanisms and kinetics of crosslinking mentioned above have also shown that the irradiation method should be ideal for preparing well characterized networks. Such materials are useful for testing theoretical relationships between the structure of rubber networks and their stress-strain behavior. The second part of this paper is devoted to this aspect. (author)

  20. UV-crosslinkable photoreactive self-adhesive hydrogels based on acrylics

    Directory of Open Access Journals (Sweden)

    Czech Zbigniew

    2016-06-01

    Full Text Available Hydrogels are a unique class of macromolecular networks that can hold a large fraction of an aqueous solvent within their structure. They are suitable for biomedical area including controlled drug delivery and for technical applications as self-adhesive materials for bonding of wet surfaces. This paper describes photoreactive self-adhesive hydrogels based on acrylics crosslinked using UV radiation. They are prepared in ethyl acetate through radical polymerization of monomers mixture containing 2-ethylhexyl acrylate (2-EHA, butyl acrylate (BA, acrylic acid (AA and copolymerizable photoinitiator 4-acryloyloxy benzophenone (ABP at presence of radical starter 2.2’-azobis-diisobutyronitrile AIBN. The synthesized acrylic copolymers were determined by viscosity and GPC analysis and later modified using ethoxylated amines. 4-acryloyloxy benzophenone (ABP was used as crosslinking monomer. After UV crosslinking the properties of these novel synthesized hydrogels, such as tack, peel adhesion, shears strength, elongation and water adsorption were also studied.

  1. Structural changes in the ordering processes of macromolecular compounds

    International Nuclear Information System (INIS)

    Kobayashi, M.; Tashiro, K.

    1998-01-01

    In order to clarify the microscopically-viewed relationship between the conformational ordering process and the aggregation process of the macromolecular chains in the phase transitions from melt to solid or from solution to gel, the time-resolved Fourier-transform infrared spectra and small-angle X-ray or neutron scattering data have been analyzed in an organized manner. Two concrete examples were presented. (1) In the gelation phenomenon of syndiotactic polystyrene-organic solvent system, the ordered TTGG conformation is formed and develops with time. This conformational ordering is accelerated by the aggregation of these chain segments, resulting in the formation of macroscopic gel network. (2) In the isothermal crystallization process from the melt of polyethylene, the following ordering mechanism was revealed. The conformationally-disordered short trans conformers appear at first in the random coils of the melt. These disordered trans sequences grow to longer and more regular trans sequences of the orthorhombic-type crystal and then the isolated lamellae are formed. Afterwards, the stacked lamellar structure is developed without change of lamellar thickness but with small decrease in the long period, indicating an insertion of new lamellae between the already produced lamellar layers

  2. Effect of crosslinking chemistry of albumin/heparin multilayers on FGF-2 adsorption and endothelial cell behavior

    Czech Academy of Sciences Publication Activity Database

    Kumorek, Marta M.; Janoušková, Olga; Höcherl, Anita; Houska, Milan; Mázl Chánová, Eliška; Kasoju, Naresh; Cuchalová, Lucie; Matějka, R.; Kubies, Dana

    2017-01-01

    Roč. 411, 31 July (2017), s. 240-250 ISSN 0169-4332 R&D Projects: GA MŠk(CZ) LQ1604; GA MŠk(CZ) ED1.1.00/02.0109 Institutional support: RVO:61389013 Keywords : basic fibroblast growth factor * heparin * cross-linking Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 3.387, year: 2016

  3. [Riboflavin UVA crosslinking in progressive keratoconus].

    Science.gov (United States)

    Maier, P; Reinhard, T

    2017-06-01

    In patients with keratoconus, a progressive, ectatic disease of the cornea, the shape of the cornea is continuously changing leading to a reduction in visual acuity by progressive myopia and more and more (irregular) astigmatism. The symptomatic treatment consists of the prescription of glasses or special gas-permeable rigid contact lenses. Corneal tomography is generally used for diagnosis. After initial diagnosis of keratoconus, regular tomographic follow-ups should be performed. If clinically significant progression is found and confirmed by repeated measurements, riboflavin UVA collagen crosslinking should be offered to the patients. The aim of riboflavin UVA collagen crosslinking is to halt the progression of the disease to avoid further complications. The therapeutic principle is a combined effect of the photosensitizer riboflavin and UVA light. This stiffening effect of the corneal tissue halts the progression of keratoconus. The efficacy of this treatment has been demonstrated in various randomized, controlled trials.

  4. Sequential recovery of macromolecular components of the nucleolus.

    Science.gov (United States)

    Bai, Baoyan; Laiho, Marikki

    2015-01-01

    The nucleolus is involved in a number of cellular processes of importance to cell physiology and pathology, including cell stress responses and malignancies. Studies of macromolecular composition of the nucleolus depend critically on the efficient extraction and accurate quantification of all macromolecular components (e.g., DNA, RNA, and protein). We have developed a TRIzol-based method that efficiently and simultaneously isolates these three macromolecular constituents from the same sample of purified nucleoli. The recovered and solubilized protein can be accurately quantified by the bicinchoninic acid assay and assessed by polyacrylamide gel electrophoresis or by mass spectrometry. We have successfully applied this approach to extract and quantify the responses of all three macromolecular components in nucleoli after drug treatments of HeLa cells, and conducted RNA-Seq analysis of the nucleolar RNA.

  5. Macromolecular Crystal Growth by Means of Microfluidics

    Science.gov (United States)

    vanderWoerd, Mark; Ferree, Darren; Spearing, Scott; Monaco, Lisa; Molho, Josh; Spaid, Michael; Brasseur, Mike; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    We have performed a feasibility study in which we show that chip-based, microfluidic (LabChip(TM)) technology is suitable for protein crystal growth. This technology allows for accurate and reliable dispensing and mixing of very small volumes while minimizing bubble formation in the crystallization mixture. The amount of (protein) solution remaining after completion of an experiment is minimal, which makes this technique efficient and attractive for use with proteins, which are difficult or expensive to obtain. The nature of LabChip(TM) technology renders it highly amenable to automation. Protein crystals obtained in our initial feasibility studies were of excellent quality as determined by X-ray diffraction. Subsequent to the feasibility study, we designed and produced the first LabChip(TM) device specifically for protein crystallization in batch mode. It can reliably dispense and mix from a range of solution constituents into two independent growth wells. We are currently testing this design to prove its efficacy for protein crystallization optimization experiments. In the near future we will expand our design to incorporate up to 10 growth wells per LabChip(TM) device. Upon completion, additional crystallization techniques such as vapor diffusion and liquid-liquid diffusion will be accommodated. Macromolecular crystallization using microfluidic technology is envisioned as a fully automated system, which will use the 'tele-science' concept of remote operation and will be developed into a research facility for the International Space Station as well as on the ground.

  6. Atomic force microscopy imaging of macromolecular complexes.

    Science.gov (United States)

    Santos, Sergio; Billingsley, Daniel; Thomson, Neil

    2013-01-01

    This chapter reviews amplitude modulation (AM) AFM in air and its applications to high-resolution imaging and interpretation of macromolecular complexes. We discuss single DNA molecular imaging and DNA-protein interactions, such as those with topoisomerases and RNA polymerase. We show how relative humidity can have a major influence on resolution and contrast and how it can also affect conformational switching of supercoiled DNA. Four regimes of AFM tip-sample interaction in air are defined and described, and relate to water perturbation and/or intermittent mechanical contact of the tip with either the molecular sample or the surface. Precise control and understanding of the AFM operational parameters is shown to allow the user to switch between these different regimes: an interpretation of the origins of topographical contrast is given for each regime. Perpetual water contact is shown to lead to a high-resolution mode of operation, which we term SASS (small amplitude small set-point) imaging, and which maximizes resolution while greatly decreasing tip and sample wear and any noise due to perturbation of the surface water. Thus, this chapter provides sufficient information to reliably control the AFM in the AM AFM mode of operation in order to image both heterogeneous samples and single macromolecules including complexes, with high resolution and with reproducibility. A brief introduction to AFM, its versatility and applications to biology is also given while providing references to key work and general reviews in the field.

  7. Study of the direct detection of crosslinking in hydrocarbons by 13C-NMR. II. Identification of crosslink in model compound and application to irradiate paraffins

    International Nuclear Information System (INIS)

    Bennett, R.L.; Keller, A.; Stejny, H.H.; Murray, M.

    1976-01-01

    A 13 C-NMR investigation was carried out in aid of direct detection of crosslinks in hydrocarbons with the future objective of studying radiation-induced crosslinking in polyethylene by a direct method. The resonance signal due to a tertiary carbon atom appropriate to a crosslink far remote from molecular ends has been identified in a definitive manner with the aid of the H-shaped model compound 1,1,2,2-tetra(tridecyl)ethane synthetized in Part I of this study. This identification was then put to use in the examination of the irradiated linear paraffins n-hexadecane and n-eicosane, where it enabled the detection of radiation-induced crosslinks. This crosslinking could then be associated with corresponding changes in molecular weight (dimer, trimer formation) as revealed by discrete peaks in the gel-permeation chromatograms of the same samples and randomness of the crosslinking process in the liquid state of these compounds being inferred

  8. Laser welding and collagen crosslinks

    Energy Technology Data Exchange (ETDEWEB)

    Reiser, K.M.; Last, J.A. [California Univ., Davis, CA (United States). Dept. of Medicine; Small, W. IV; Maitland, D.J.; Heredia, N.J.; Da Silva, L.B.; Matthews, D.L. [Lawrence Livermore National Lab., CA (United States)

    1997-02-20

    Strength and stability of laser-welded tissue may be influenced, in part, by effects of laser exposure on collagen crosslinking. We therefore studied effects of diode laser exposure (805 nm, 1-8 watts, 30 seconds) + indocyanine green dye (ICG) on calf tail tendon collagen crosslinks. Effect of ICG dye alone on crosslink content prior to laser exposure was investigated; unexpectedly, we found that ICG-treated tissue had significantly increased DHLNL and OHP, but not HLNL. Laser exposure after ICG application reduced elevated DHLNL and OHP crosslink content down to their native levels. The monohydroxylated crosslink HLNL was inversely correlated with laser output (p<0.01 by linear regression analysis). DHLNL content was highly correlated with content of its maturational product, OHP, suggesting that precursor-product relations are maintained. We conclude that: (1)ICG alone induces DHLNL and OHP crosslink formation; (2)subsequent laser exposure reduces the ICG-induced crosslinks down to native levels; (3)excessive diode laser exposure destroys normally occurring HLNL crosslinks.

  9. Radiation crosslinking of polymer materials

    International Nuclear Information System (INIS)

    Yoshii, Fumio

    2004-01-01

    It was found that some polyfunctional monomers (PFM) like triallyl isocyanurate (TAIC) and trimethallyl isocyanurate (TMAIC) when incorporated at low concentrations, are effective for promotion of crosslinking of biodegradable polymers such as polycaprolactone (PCL), poly(butylene succinate-co-adipate) (PBS) and poly(lactic acid) (PLA). PFM are kneaded with biodegradable polymers at molten condition before irradiation. Radiation crosslinking of PBS and PCL with 1% TAIC gave gel fractions of 80% at 20 kGy. This crosslinking is effective to improve deformation of biodegradable polymers at high temperature. The irradiated materials retained their biodegradability even after crosslinking when subjected to soil burial test. Irradiation at molten state (melting temperature, 340degC) led to crosslinking structures for polytetrafluoroethylene (PTFE). Crosslinked PTFE forms transparent films with high abrasion property and high radiation resistance. High-density polyethylene (HDPE) has a higher gel fraction in irradiation at molten state than irradiation at ordinary temperature. Crosslinked HDPE has been applied as knee joints in order to have high abrasion. Radiation crosslinked polycarbosilane (PCS) fiber gives high heat resistant silicon carbide (SiC) after firing. EB irradiation of PCS is effective to improve strength of product and to inhibit flow during carbonization. SiC, being resistant to high temperature will be applied in turbine and body of rockets. (author)

  10. DNA Photolithography with Cinnamate Crosslinkers

    Science.gov (United States)

    Feng, Lang (Inventor); Chaikin, Paul Michael (Inventor)

    2016-01-01

    The present invention relates generally to cinnamate crosslinkers. Specifically, the present invention relates to gels, biochips, and functionalized surfaces useful as probes, in assays, in gels, and for drug delivery, and methods of making the same using a newly-discovered crosslinking configuration.

  11. Characterisation of radiation crosslinked polydimethylsiloxane

    International Nuclear Information System (INIS)

    Preston, C.M.L.; Hill, D.J.T.; Pomery, P.J.; Whittaker, A.K.

    1998-01-01

    Polysiloxanes, or silicones, are used widely in industry, as lubricants and process additives, as well as in many household products. The most common of the silicones is polydimethylsiloxane (PDMS). The fact that silicones crosslink during exposure to high energy radiation is well established. However, despite the number of studies performed on these systems, the exact mechanism of crosslinking has yet to be determined. Nuclear Magnetic Resonance spectroscopy (NMR) provides a useful method for the analysis of crosslinked polymer systems. Linear uncrosslinked PDMS is easily characterised in the solution state by NMR, as PDMS is readily soluble in common organic solvents. However, the onset of gelation caused by crosslinking results in an insoluble polymer network. The use of cross-polarisation (CP) and magic-angle spinning (MAS) in conjunction with high power decoupling has been shown to greatly enhance sensitivity of the NMR technique in solids. The true mechanism of crosslinking between polymer chains will be discussed

  12. Intracellular Crosslinking of Filoviral Nucleoproteins with Xintrabodies Restricts Viral Packaging

    Directory of Open Access Journals (Sweden)

    Tamarand Lee Darling

    2017-09-01

    Full Text Available Viruses assemble large macromolecular repeat structures that become part of the infectious particles or virions. Ribonucleocapsids (RNCs of negative strand RNA viruses are a prime example where repetition of nucleoprotein (NP along the genome creates a core polymeric helical scaffold that accommodates other nucleocapsid proteins including viral polymerase. The RNCs are transported through the cytosol for packaging into virions through association with viral matrix proteins at cell membranes. We hypothesized that RNC would be ideal targets for crosslinkers engineered to promote aberrant protein–protein interactions, thereby blocking their orderly transport and packaging. Previously, we had generated single-domain antibodies (sdAbs against Filoviruses that have all targeted highly conserved C-terminal regions of NP known to be repetitively exposed along the length of the RNCs of Marburgvirus (MARV and Ebolavirus (EBOV. Our crosslinker design consisted of dimeric sdAb expressed intracellularly, which we call Xintrabodies (X- for crosslinking. Electron microscopy of purified NP polymers incubated with purified sdAb constructs showed NP aggregation occurred in a genus-specific manner with dimeric and not monomeric sdAb. A virus-like particle (VLP assay was used for initial evaluation where we found that dimeric sdAb inhibited NP incorporation into VP40-based VLPs whereas monomeric sdAb did not. Inhibition of NP packaging was genus specific. Confocal microscopy revealed dimeric sdAb was diffuse when expressed alone but focused on pools of NP when the two were coexpressed, while monomeric sdAb showed ambivalent partition. Infection of stable Vero cell lines expressing dimeric sdAb specific for either MARV or EBOV NP resulted in smaller plaques and reduced progeny of cognate virus relative to wild-type Vero cells. Though the impact was marginal at later time-points, the collective data suggest that viral replication can be reduced by crosslinking

  13. Structure and distribution of cross-links in boron-modified phenol-formaldehyde resins designed for soft magnetic composites: a multiple-quantum 11B-11B MAS NMR correlation spectroscopy study

    Czech Academy of Sciences Publication Activity Database

    Kobera, Libor; Czernek, Jiří; Strečková, M.; Urbanová, Martina; Abbrent, Sabina; Brus, Jiří

    2015-01-01

    Roč. 48, č. 14 (2015), s. 4874-4881 ISSN 0024-9297 R&D Projects: GA MŠk(CZ) LD14010 Grant - others:European Commission(XE) COST Action MP1202 HINT Institutional support: RVO:61389013 Keywords : phenol-formaldehyde polymers * boron crosslinks * soft magnetic composites Subject RIV: CD - Macromolecular Chemistry Impact factor: 5.554, year: 2015

  14. Radiation crosslinking of polymer blends

    International Nuclear Information System (INIS)

    Spenadel, L.

    1979-01-01

    Rocked by the one-two punch of rising energy costs and tougher pollution controls, a growing number of companies are looking to radiation crosslinking as a cheaper, cleaner alternative to heat and costly chemical crosslinking agents such as peroxides. With the development of larger, more powerful electron beam machines it is now possible to irradiate parts as thick as 400 mils in a single pass. Two application areas which have been investigated at our laboratory are the electron beam processing of thermoplastic elastomeric automotive parts and EPDM electrical insulation. This paper covers work carried out to develop the necessary technology base for the radiation crosslinking of ethylene propylene/polyolefin blends. Initial results indicate that EP/PE blends of electrical insulation quality cross-link quite readily when irradiated. On the other hand, EP/PP blends developed for automotive fascia require the addition of crosslinking monomers such as trimethylol propane trimethacrylate in order for crosslinking to predominate over chain scission. Crosslinking EP/PP blends improve mar resistance, flexural set and deformation at elevated temperatures. These are all key properties for automotive fascia. (author)

  15. Donor cross-linking for keratoplasty: a laboratory evaluation.

    Science.gov (United States)

    Mukherjee, Achyut; Hayes, Sally; Aslanides, Ioannis; Lanchares, Elena; Meek, Keith M

    2015-12-01

    This laboratory-based investigation compares the topographic outcomes of conventional penetrating keratoplasty with that of a novel procedure in which donor corneas are cross-linked prior to keratoplasty. Penetrating keratoplasty procedures with continuous running sutures were carried out in a porcine whole globe model. Sixty eyes were randomly paired as 'donor' and 'host' tissue before being assigned to one of two groups. In the cross-linked group, donor corneas underwent riboflavin/UVA cross-linking prior to being trephined and sutured to untreated hosts. In the conventional keratoplasty group, both host and donor corneas remained untreated prior to keratoplasty. Topographic and corneal wavefront measurements were performed following surgery, and technical aspects of the procedure evaluated. Mean keratometric astigmatism was significantly lower in the cross-linked donor group at 3.67D (SD 1.8 D), vs. 8.43 D (SD 2.4 D) in the conventional keratoplasty group (p < 0.005). Mean wavefront astigmatism was also significantly reduced in the cross-linked donor group 4.71 D (SD 2.1) vs. 8.29D (SD 3.6) in the conventional keratoplasty group (p < 0.005). Mean RMS higher order aberration was significantly lower in the cross-linked donor group at 1.79 um (SD 0.98), vs. 3.05 um (SD 1.9) in the conventional keratoplasty group (P = 0.02). Qualitative analysis revealed less tissue distortion at the graft-host junction in the cross-linked group. Cross-linking of donor corneas prior to keratoplasty reduces intraoperative induced astigmatism and aberrations in an animal model. Further studies are indicated to evaluate the implications of this potential modification of keratoplasty surgery.

  16. Complex Macromolecular Architectures by Living Cationic Polymerization

    KAUST Repository

    Alghamdi, Reem D.

    2015-05-01

    Poly (vinyl ether)-based graft polymers have been synthesized by the combination of living cationic polymerization of vinyl ethers with other living or controlled/ living polymerization techniques (anionic and ATRP). The process involves the synthesis of well-defined homopolymers (PnBVE) and co/terpolymers [PnBVE-b-PCEVE-b-PSiDEGVE (ABC type) and PSiDEGVE-b-PnBVE-b-PSiDEGVE (CAC type)] by sequential living cationic polymerization of n-butyl vinyl ether (nBVE), 2-chloroethyl vinyl ether (CEVE) and tert-butyldimethylsilyl ethylene glycol vinyl ether (SiDEGVE), using mono-functional {[n-butoxyethyl acetate (nBEA)], [1-(2-chloroethoxy) ethyl acetate (CEEA)], [1-(2-(2-(t-butyldimethylsilyloxy)ethoxy) ethoxy) ethyl acetate (SiDEGEA)]} or di-functional [1,4-cyclohexanedimethanol di(1-ethyl acetate) (cHMDEA), (VEMOA)] initiators. The living cationic polymerizations of those monomers were conducted in hexane at -20 0C using Et3Al2Cl3 (catalyst) in the presence of 1 M AcOEt base.[1] The PCEVE segments of the synthesized block terpolymers were then used to react with living macroanions (PS-DPE-Li; poly styrene diphenyl ethylene lithium) to afford graft polymers. The quantitative desilylation of PSiDEGVE segments by n-Bu4N+F- in THF at 0 °C led to graft co- and terpolymers in which the polyalcohol is the outer block. These co-/terpolymers were subsequently subjected to “grafting-from” reactions by atom transfer radical polymerization (ATRP) of styrene to afford more complex macromolecular architectures. The base assisted living cationic polymerization of vinyl ethers were also used to synthesize well-defined α-hydroxyl polyvinylether (PnBVE-OH). The resulting polymers were then modified into an ATRP macro-initiator for the synthesis of well-defined block copolymers (PnBVE-b-PS). Bifunctional PnBVE with terminal malonate groups was also synthesized and used as a precursor for more complex architectures such as H-shaped block copolymer by “grafting-from” or

  17. Macromolecular crystallography beamline X25 at the NSLS

    Energy Technology Data Exchange (ETDEWEB)

    Héroux, Annie; Allaire, Marc; Buono, Richard; Cowan, Matthew L.; Dvorak, Joseph; Flaks, Leon; LaMarra, Steven; Myers, Stuart F.; Orville, Allen M.; Robinson, Howard H.; Roessler, Christian G.; Schneider, Dieter K.; Shea-McCarthy, Grace; Skinner, John M.; Skinner, Michael; Soares, Alexei S.; Sweet, Robert M.; Berman, Lonny E., E-mail: berman@bnl.gov [Brookhaven National Laboratory, PO Box 5000, Upton, NY 11973-5000 (United States)

    2014-04-08

    A description of the upgraded beamline X25 at the NSLS, operated by the PXRR and the Photon Sciences Directorate serving the Macromolecular Crystallography community, is presented. Beamline X25 at the NSLS is one of the five beamlines dedicated to macromolecular crystallography operated by the Brookhaven National Laboratory Macromolecular Crystallography Research Resource group. This mini-gap insertion-device beamline has seen constant upgrades for the last seven years in order to achieve mini-beam capability down to 20 µm × 20 µm. All major components beginning with the radiation source, and continuing along the beamline and its experimental hutch, have changed to produce a state-of-the-art facility for the scientific community.

  18. Macromolecular crystallography beamline X25 at the NSLS

    International Nuclear Information System (INIS)

    Héroux, Annie; Allaire, Marc; Buono, Richard; Cowan, Matthew L.; Dvorak, Joseph; Flaks, Leon; LaMarra, Steven; Myers, Stuart F.; Orville, Allen M.; Robinson, Howard H.; Roessler, Christian G.; Schneider, Dieter K.; Shea-McCarthy, Grace; Skinner, John M.; Skinner, Michael; Soares, Alexei S.; Sweet, Robert M.; Berman, Lonny E.

    2014-01-01

    A description of the upgraded beamline X25 at the NSLS, operated by the PXRR and the Photon Sciences Directorate serving the Macromolecular Crystallography community, is presented. Beamline X25 at the NSLS is one of the five beamlines dedicated to macromolecular crystallography operated by the Brookhaven National Laboratory Macromolecular Crystallography Research Resource group. This mini-gap insertion-device beamline has seen constant upgrades for the last seven years in order to achieve mini-beam capability down to 20 µm × 20 µm. All major components beginning with the radiation source, and continuing along the beamline and its experimental hutch, have changed to produce a state-of-the-art facility for the scientific community

  19. Enzymatic cross-linking of human recombinant elastin (HELP) as biomimetic approach in vascular tissue engineering.

    Science.gov (United States)

    Bozzini, Sabrina; Giuliano, Liliana; Altomare, Lina; Petrini, Paola; Bandiera, Antonella; Conconi, Maria Teresa; Farè, Silvia; Tanzi, Maria Cristina

    2011-12-01

    The use of polymers naturally occurring in the extracellular matrix (ECM) is a promising strategy in regenerative medicine. If compared to natural ECM proteins, proteins obtained by recombinant DNA technology have intrinsic advantages including reproducible macromolecular composition, sequence and molecular mass, and overcoming the potential pathogens transmission related to polymers of animal origin. Among ECM-mimicking materials, the family of recombinant elastin-like polymers is proposed for drug delivery applications and for the repair of damaged elastic tissues. This work aims to evaluate the potentiality of a recombinant human elastin-like polypeptide (HELP) as a base material of cross-linked matrices for regenerative medicine. The cross-linking of HELP was accomplished by the insertion of cross-linking sites, glutamine and lysine, in the recombinant polymer and generating ε-(γ-glutamyl) lysine links through the enzyme transglutaminase. The cross-linking efficacy was estimated by infrared spectroscopy. Freeze-dried cross-linked matrices showed swelling ratios in deionized water (≈2500%) with good structural stability up to 24 h. Mechanical compression tests, performed at 37°C in wet conditions, in a frequency sweep mode, indicated a storage modulus of 2/3 kPa, with no significant changes when increasing number of cycles or frequency. These results demonstrate the possibility to obtain mechanically resistant hydrogels via enzymatic crosslinking of HELP. Cytotoxicity tests of cross-linked HELP were performed with human umbilical vein endothelial cells, by use of transwell filter chambers for 1-7 days, or with its extracts in the opportune culture medium for 24 h. In both cases no cytotoxic effects were observed in comparison with the control cultures. On the whole, the results suggest the potentiality of this genetically engineered HELP for regenerative medicine applications, particularly for vascular tissue regeneration.

  20. Automobile parts by radiation crosslinking

    International Nuclear Information System (INIS)

    Yoshii, Fumio

    2008-01-01

    Radiation crosslinking, graft polymerization and degradation are useful technologies to improve polymer materials. The crosslinking causes improvement in strength, heat stability and processability to gives network structure for polymer materials and hence crosslinked materials are used in various fields, especially car parts. Electron beam (EB) of short time irradiation is used for these modifications. Irradiated (pre-vulcanized) before sulfur vulcanization rubber tires, heat resistant wires/cables, shrinkable tubes and foams of car parts are achieved by EB crosslinking. Polyethylene and polyvinyl chloride are used in cables and wires, polypropylene in plastic foams and natural rubber etc. In this paper radiation processing of tire, wire/cables, foams, shrinkable tubes and circuit protection devices (CPT) are explained. (author)

  1. Covalent crosslinking of carbon nanostructures

    Indian Academy of Sciences (India)

    Composites of the binary conjugates with polymer can be readily prepared by using the ... Besides the preparation of crosslinked ... of graphite oxide following the procedure described ... several times to remove the metal nanoparticles and.

  2. Radiation induced crosslinking of polytetrafluoroethylene

    International Nuclear Information System (INIS)

    Oshima, Akihiro; Tabata, Yoneho; Ikeda, Shigetoshi; Otsuhata, Kazushige; Kudoh, Hisaaki; Seguchi, Tadao.

    1995-01-01

    The Irradiation temperature effect on polytetrafluoroethylene (PTFE) from room temperature to 380degC was investigated by tensile test and thermal analysis. The behavior of tensile properties and changes of crystallinity on irradiation indicated the formation of a network structure in PTFE by radiation induced crosslinking in inert gas in the molten state just above the melting temperature of PTFE (327degC). The crosslinked PTFE showed a much improved radiation resistance in an atmospheric radiation field. (author)

  3. Control of Macromolecular Architectures for Renewable Polymers: Case Studies

    Science.gov (United States)

    Tang, Chuanbing

    The development of sustainable polymers from nature biomass is growing, but facing fierce competition from existing petrochemical-based counterparts. Controlling macromolecular architectures to maximize the properties of renewable polymers is a desirable approach to gain advantages. Given the complexity of biomass, there needs special consideration other than traditional design. In the presentation, I will talk about a few case studies on how macromolecular architectures could tune the properties of sustainable bioplastics and elastomers from renewable biomass such as resin acids (natural rosin) and plant oils.

  4. Crosslinking of agarose bioplastic using citric acid.

    Science.gov (United States)

    Awadhiya, Ankur; Kumar, David; Verma, Vivek

    2016-10-20

    We report chemical crosslinking of agarose bioplastic using citric acid. Crosslinking was confirmed using Fourier transform infrared (FTIR) spectroscopy. The effects of crosslinking on the tensile strength, swelling, thermal stability, and degradability of the bioplastic were studied in detail. The tensile strength of the bioplastic films increased from 25.1MPa for control films up to a maximum of 52.7MPa for citric acid crosslinked films. At 37°C, the amount of water absorbed by crosslinked agarose bioplastic was only 11.5% of the amount absorbed by non-crosslinked controls. Thermogravimetric results showed that the crosslinked samples retain greater mass at high temperature (>450°C) than control samples. Moreover, while the crosslinked films were completely degradable, the rate of degradation was lower compared to non-crosslinked controls. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Analytical model for macromolecular partitioning during yeast cell division

    International Nuclear Information System (INIS)

    Kinkhabwala, Ali; Khmelinskii, Anton; Knop, Michael

    2014-01-01

    Asymmetric cell division, whereby a parent cell generates two sibling cells with unequal content and thereby distinct fates, is central to cell differentiation, organism development and ageing. Unequal partitioning of the macromolecular content of the parent cell — which includes proteins, DNA, RNA, large proteinaceous assemblies and organelles — can be achieved by both passive (e.g. diffusion, localized retention sites) and active (e.g. motor-driven transport) processes operating in the presence of external polarity cues, internal asymmetries, spontaneous symmetry breaking, or stochastic effects. However, the quantitative contribution of different processes to the partitioning of macromolecular content is difficult to evaluate. Here we developed an analytical model that allows rapid quantitative assessment of partitioning as a function of various parameters in the budding yeast Saccharomyces cerevisiae. This model exposes quantitative degeneracies among the physical parameters that govern macromolecular partitioning, and reveals regions of the solution space where diffusion is sufficient to drive asymmetric partitioning and regions where asymmetric partitioning can only be achieved through additional processes such as motor-driven transport. Application of the model to different macromolecular assemblies suggests that partitioning of protein aggregates and episomes, but not prions, is diffusion-limited in yeast, consistent with previous reports. In contrast to computationally intensive stochastic simulations of particular scenarios, our analytical model provides an efficient and comprehensive overview of partitioning as a function of global and macromolecule-specific parameters. Identification of quantitative degeneracies among these parameters highlights the importance of their careful measurement for a given macromolecular species in order to understand the dominant processes responsible for its observed partitioning

  6. Robust cross-links in molluscan adhesive gels: testing for contributions from hydrophobic and electrostatic interactions.

    Science.gov (United States)

    Smith, A M; Robinson, T M; Salt, M D; Hamilton, K S; Silvia, B E; Blasiak, R

    2009-02-01

    The cross-linking interactions that provide cohesive strength to molluscan adhesive gels were investigated. Metal-based interactions have been shown to play an important role in the glue of the slug Arion subfuscus (Draparnaud), but other types of interactions may also contribute to the glue's strength and their role has not been investigated. This study shows that treatments that normally disrupt hydrophobic or electrostatic interactions have little to no effect on the slug glue. High salt concentrations and non-ionic detergent do not affect the solubility of the proteins in the glue or the ability of the glue proteins to stiffen gels. In contrast, metal chelation markedly disrupts the gel. Experiments with gel filtration chromatography identify a 40 kDa protein that is a central component of the cross-links in the glue. This 40 kDa protein forms robust macromolecular aggregations that are stable even in the presence of high concentrations of salt, non-ionic detergent, urea or metal chelators. Metal chelation during glue secretion, however, may block some of these cross-links. Such robust, non-specific interactions in an aqueous environment are highly unusual for hydrogels and reflect an intriguing cross-linking mechanism.

  7. Effect of crosslink torsional stiffness on elastic behavior of semiflexible polymer networks

    Science.gov (United States)

    Hatami-Marbini, H.

    2018-02-01

    Networks of semiflexible filaments are building blocks of different biological and structural materials such as cytoskeleton and extracellular matrix. The mechanical response of these systems when subjected to an applied strain at zero temperature is often investigated numerically using networks composed of filaments, which are either rigidly welded or pinned together at their crosslinks. In the latter, filaments during deformation are free to rotate about their crosslinks while the relative angles between filaments remain constant in the former. The behavior of crosslinks in actual semiflexible networks is different than these idealized models and there exists only partial constraint on torques at crosslinks. The present work develops a numerical model in which two intersecting filaments are connected to each other by torsional springs with arbitrary stiffness. We show that fiber networks composed of rigid and freely rotating crosslinks are the limiting case of the present model. Furthermore, we characterize the effects of stiffness of crosslinks on effective Young's modulus of semiflexible networks as a function of filament flexibility and crosslink density. The effective Young's modulus is determined as a function of the mechanical properties of crosslinks and is found to vanish for networks composed of very weak torsional springs. Independent of the stiffness of crosslinks, it is found that the effective Young's modulus is a function of fiber flexibility and crosslink density. In low density networks, filaments primarily bend and the effective Young's modulus is much lower than the affine estimate. With increasing filament bending stiffness and/or crosslink density, the mechanical behavior of the networks becomes more affine and the stretching of filaments depicts itself as the dominant mode of deformation. The torsional stiffness of the crosslinks significantly affects the effective Young's modulus of the semiflexible random fiber networks.

  8. EB radiation crosslinking of elastomers

    International Nuclear Information System (INIS)

    Bik, J.; Rzymski, M.; Gluszewski, W.; Zagorski, Z.P.

    2002-01-01

    Complete text of publication follows. The first paper in the series described by the general title, starts with radiation crosslinking of hydrogenated butadiene-nitrile rubber (HBNR). This high-tech elastomer is obtained by catalytic hydrogenation of >C=C 99.5 and 94.5% of starting double bonds. Samples were irradiated with 10 MeV electrons, monoenergetical, 6 kW power, used as scanned beam over the conveyor, securing homogeneity of dose distribution. The doses were up to 300 kGy, applied in 20 kGy increments to avoid radiation generated heating of the material. The influence of presence or absence of oxygen was considered. Irradiated samples were investigated for the extend of crosslinking in the function of dose and for properties important for understanding of mechanisms. Samples are transparent, what allowed conventional absorption spectrophotometry, also time resolved. The quantitative interpretation of results shows that for 100 crosslinks there are 6-9 acts of chain-scission. It is less, than expected from the participation of multi-ionization spurs, also in the solid state, as announced during the previous, 9th Tihany Conference. However, the apparent lower yield of multi-ionization spurs is explained by partial conversion of products into crosslinks of specific type. Our investigations confirm the usefulness of consideration of radiation spurs in polymers as well as in all, low LET irradiated media

  9. Isotope labeling for NMR studies of macromolecular structure and interactions

    International Nuclear Information System (INIS)

    Wright, P.E.

    1994-01-01

    Implementation of biosynthetic methods for uniform or specific isotope labeling of proteins, coupled with the recent development of powerful heteronuclear multidimensional NMR methods, has led to a dramatic increase in the size and complexity of macromolecular systems that are now amenable to NMR structural analysis. In recent years, a new technology has emerged that combines uniform 13 C, 15 N labeling with heteronuclear multidimensional NMR methods to allow NMR structural studies of systems approaching 25 to 30 kDa in molecular weight. In addition, with the introduction of specific 13 C and 15 N labels into ligands, meaningful NMR studies of complexes of even higher molecular weight have become feasible. These advances usher in a new era in which the earlier, rather stringent molecular weight limitations have been greatly surpassed and NMR can begin to address many central biological problems that involve macromolecular structure, dynamics, and interactions

  10. Crowding-facilitated macromolecular transport in attractive micropost arrays.

    Science.gov (United States)

    Chien, Fan-Tso; Lin, Po-Keng; Chien, Wei; Hung, Cheng-Hsiang; Yu, Ming-Hung; Chou, Chia-Fu; Chen, Yeng-Long

    2017-05-02

    Our study of DNA dynamics in weakly attractive nanofabricated post arrays revealed crowding enhances polymer transport, contrary to hindered transport in repulsive medium. The coupling of DNA diffusion and adsorption to the microposts results in more frequent cross-post hopping and increased long-term diffusivity with increased crowding density. We performed Langevin dynamics simulations and found maximum long-term diffusivity in post arrays with gap sizes comparable to the polymer radius of gyration. We found that macromolecular transport in weakly attractive post arrays is faster than in non-attractive dense medium. Furthermore, we employed hidden Markov analysis to determine the transition of macromolecular adsorption-desorption on posts and hopping between posts. The apparent free energy barriers are comparable to theoretical estimates determined from polymer conformational fluctuations.

  11. Isotope labeling for NMR studies of macromolecular structure and interactions

    Energy Technology Data Exchange (ETDEWEB)

    Wright, P.E. [Scripps Research Institute, La Jolla, CA (United States)

    1994-12-01

    Implementation of biosynthetic methods for uniform or specific isotope labeling of proteins, coupled with the recent development of powerful heteronuclear multidimensional NMR methods, has led to a dramatic increase in the size and complexity of macromolecular systems that are now amenable to NMR structural analysis. In recent years, a new technology has emerged that combines uniform {sup 13}C, {sup 15}N labeling with heteronuclear multidimensional NMR methods to allow NMR structural studies of systems approaching 25 to 30 kDa in molecular weight. In addition, with the introduction of specific {sup 13}C and {sup 15}N labels into ligands, meaningful NMR studies of complexes of even higher molecular weight have become feasible. These advances usher in a new era in which the earlier, rather stringent molecular weight limitations have been greatly surpassed and NMR can begin to address many central biological problems that involve macromolecular structure, dynamics, and interactions.

  12. Stochastic reaction-diffusion algorithms for macromolecular crowding

    Science.gov (United States)

    Sturrock, Marc

    2016-06-01

    Compartment-based (lattice-based) reaction-diffusion algorithms are often used for studying complex stochastic spatio-temporal processes inside cells. In this paper the influence of macromolecular crowding on stochastic reaction-diffusion simulations is investigated. Reaction-diffusion processes are considered on two different kinds of compartmental lattice, a cubic lattice and a hexagonal close packed lattice, and solved using two different algorithms, the stochastic simulation algorithm and the spatiocyte algorithm (Arjunan and Tomita 2010 Syst. Synth. Biol. 4, 35-53). Obstacles (modelling macromolecular crowding) are shown to have substantial effects on the mean squared displacement and average number of molecules in the domain but the nature of these effects is dependent on the choice of lattice, with the cubic lattice being more susceptible to the effects of the obstacles. Finally, improvements for both algorithms are presented.

  13. Diffusion accessibility as a method for visualizing macromolecular surface geometry.

    Science.gov (United States)

    Tsai, Yingssu; Holton, Thomas; Yeates, Todd O

    2015-10-01

    Important three-dimensional spatial features such as depth and surface concavity can be difficult to convey clearly in the context of two-dimensional images. In the area of macromolecular visualization, the computer graphics technique of ray-tracing can be helpful, but further techniques for emphasizing surface concavity can give clearer perceptions of depth. The notion of diffusion accessibility is well-suited for emphasizing such features of macromolecular surfaces, but a method for calculating diffusion accessibility has not been made widely available. Here we make available a web-based platform that performs the necessary calculation by solving the Laplace equation for steady state diffusion, and produces scripts for visualization that emphasize surface depth by coloring according to diffusion accessibility. The URL is http://services.mbi.ucla.edu/DiffAcc/. © 2015 The Protein Society.

  14. Modeling the multi-scale mechanisms of macromolecular resource allocation

    DEFF Research Database (Denmark)

    Yang, Laurence; Yurkovich, James T; King, Zachary A

    2018-01-01

    As microbes face changing environments, they dynamically allocate macromolecular resources to produce a particular phenotypic state. Broad 'omics' data sets have revealed several interesting phenomena regarding how the proteome is allocated under differing conditions, but the functional consequen...... and detail how mathematical models have aided in our understanding of these processes. Ultimately, such modeling efforts have helped elucidate the principles of proteome allocation and hold promise for further discovery....

  15. What Macromolecular Crowding Can Do to a Protein

    Science.gov (United States)

    Kuznetsova, Irina M.; Turoverov, Konstantin K.; Uversky, Vladimir N.

    2014-01-01

    The intracellular environment represents an extremely crowded milieu, with a limited amount of free water and an almost complete lack of unoccupied space. Obviously, slightly salted aqueous solutions containing low concentrations of a biomolecule of interest are too simplistic to mimic the “real life” situation, where the biomolecule of interest scrambles and wades through the tightly packed crowd. In laboratory practice, such macromolecular crowding is typically mimicked by concentrated solutions of various polymers that serve as model “crowding agents”. Studies under these conditions revealed that macromolecular crowding might affect protein structure, folding, shape, conformational stability, binding of small molecules, enzymatic activity, protein-protein interactions, protein-nucleic acid interactions, and pathological aggregation. The goal of this review is to systematically analyze currently available experimental data on the variety of effects of macromolecular crowding on a protein molecule. The review covers more than 320 papers and therefore represents one of the most comprehensive compendia of the current knowledge in this exciting area. PMID:25514413

  16. Macromolecular target prediction by self-organizing feature maps.

    Science.gov (United States)

    Schneider, Gisbert; Schneider, Petra

    2017-03-01

    Rational drug discovery would greatly benefit from a more nuanced appreciation of the activity of pharmacologically active compounds against a diverse panel of macromolecular targets. Already, computational target-prediction models assist medicinal chemists in library screening, de novo molecular design, optimization of active chemical agents, drug re-purposing, in the spotting of potential undesired off-target activities, and in the 'de-orphaning' of phenotypic screening hits. The self-organizing map (SOM) algorithm has been employed successfully for these and other purposes. Areas covered: The authors recapitulate contemporary artificial neural network methods for macromolecular target prediction, and present the basic SOM algorithm at a conceptual level. Specifically, they highlight consensus target-scoring by the employment of multiple SOMs, and discuss the opportunities and limitations of this technique. Expert opinion: Self-organizing feature maps represent a straightforward approach to ligand clustering and classification. Some of the appeal lies in their conceptual simplicity and broad applicability domain. Despite known algorithmic shortcomings, this computational target prediction concept has been proven to work in prospective settings with high success rates. It represents a prototypic technique for future advances in the in silico identification of the modes of action and macromolecular targets of bioactive molecules.

  17. Design and application of a C++ macromolecular class library.

    Science.gov (United States)

    Chang, W; Shindyalov, I N; Pu, C; Bourne, P E

    1994-01-01

    PDBlib is an extensible object oriented class library written in C++ for representing the 3-dimensional structure of biological macromolecules. PDBlib forms the kernel of a larger software framework being developed for assiting in knowledge discovery from macromolecular structure data. The software design strategy used by PDBlib, how the library may be used and several prototype applications that use the library are summarized. PDBlib represents the structural features of proteins, DNA, RNA, and complexes thereof, at a level of detail on a par with that which can be parsed from a Protein Data Bank (PDB) entry. However, the memory resident representation of the macromolecule is independent of the PDB entry and can be obtained from other back-end data sources, for example, existing relational databases and our own object oriented database (OOPDB) built on top of the commercial object oriented database, ObjectStore. At the front-end are several prototype applications that use the library: Macromolecular Query Language (MMQL) is based on a separate class library (MMQLlib) for building complex queries pertaining to macromolecular structure; PDBtool is an interactive structure verification tool; and PDBview, is a structure rendering tool used either as a standalone tool or as part of another application. Each of these software components are described. All software is available via anonymous ftp from cuhhca.hhmi.columbia.edu.

  18. Dynamics simulations for engineering macromolecular interactions

    Science.gov (United States)

    Robinson-Mosher, Avi; Shinar, Tamar; Silver, Pamela A.; Way, Jeffrey

    2013-01-01

    The predictable engineering of well-behaved transcriptional circuits is a central goal of synthetic biology. The artificial attachment of promoters to transcription factor genes usually results in noisy or chaotic behaviors, and such systems are unlikely to be useful in practical applications. Natural transcriptional regulation relies extensively on protein-protein interactions to insure tightly controlled behavior, but such tight control has been elusive in engineered systems. To help engineer protein-protein interactions, we have developed a molecular dynamics simulation framework that simplifies features of proteins moving by constrained Brownian motion, with the goal of performing long simulations. The behavior of a simulated protein system is determined by summation of forces that include a Brownian force, a drag force, excluded volume constraints, relative position constraints, and binding constraints that relate to experimentally determined on-rates and off-rates for chosen protein elements in a system. Proteins are abstracted as spheres. Binding surfaces are defined radially within a protein. Peptide linkers are abstracted as small protein-like spheres with rigid connections. To address whether our framework could generate useful predictions, we simulated the behavior of an engineered fusion protein consisting of two 20 000 Da proteins attached by flexible glycine/serine-type linkers. The two protein elements remained closely associated, as if constrained by a random walk in three dimensions of the peptide linker, as opposed to showing a distribution of distances expected if movement were dominated by Brownian motion of the protein domains only. We also simulated the behavior of fluorescent proteins tethered by a linker of varying length, compared the predicted Förster resonance energy transfer with previous experimental observations, and obtained a good correspondence. Finally, we simulated the binding behavior of a fusion of two ligands that could

  19. Microfabrication of crosslinked PTFE by synchrotron radiation

    International Nuclear Information System (INIS)

    Sato, Yasunori; Yamaguchi, Daichi; Oshima, Akihiro; Washio, Masakazu; Katoh, Takanori; Aoki, Yasushi; Ikeda, Shigetoshi; Tanaka, Shigeru

    2003-01-01

    Microfabrication of crosslinked polytetrafluoroethylene (PTFE) using synchrotron radiation (SR) has been demonstrated for production of micro-components applicable to radiation fields. The method of microfabrication was readily capable of obtaining a microstructure with aspect-ratio of 25 made of crosslinked PTFE. The etching rate of crosslinked PTFE was higher than that of non-crosslinked PTFE. The results show that the etching rate of crosslinked PTFE depends only on the degree of crosslinking. The effect of molecular motion on etching process was discussed from temperature dependence on etching rate. Moreover, in order to examine whether any change of chemical structures and crystallinity would be induced by SR-irradiation on PTFE, SR-irradiated PTFE was measured by NMR spectroscopy and DSC analysis. The results showed that the crosslinking reaction of PTFE would be induced by SR-irradiation in the solid state. (author)

  20. Repair of 8-methoxypsoralen induced DNA interstrand cross-links in Tetrahymena thermophila. The effect of inhibitors of macromolecular synthesis

    DEFF Research Database (Denmark)

    Nielsen, P E; Køber, L

    1985-01-01

    -beta-D-arabinofuranoside (10 mM), puromycin (1 mM), hydroxyurea (5 mM) or 3-aminobenzamide (2.5 mM). None of the compounds showed any effect on the protein-DNA complexing step, and the ligation was partly inhibited only by nalidixic acid (150 micrograms/ml). The involvement of topoisomerases...

  1. Predictive Mechanical Characterization of Macro-Molecular Material Chemistry Structures of Cement Paste at Nano Scale - Two-phase Macro-Molecular Structures of Calcium Silicate Hydrate, Tri-Calcium Silicate, Di-Calcium Silicate and Calcium Hydroxide

    Science.gov (United States)

    Padilla Espinosa, Ingrid Marcela

    Concrete is a hierarchical composite material with a random structure over a wide range of length scales. At submicron length scale the main component of concrete is cement paste, formed by the reaction of Portland cement clinkers and water. Cement paste acts as a binding matrix for the other components and is responsible for the strength of concrete. Cement paste microstructure contains voids, hydrated and unhydrated cement phases. The main crystalline phases of unhydrated cement are tri-calcium silicate (C3S) and di-calcium silicate (C2S), and of hydrated cement are calcium silicate hydrate (CSH) and calcium hydroxide (CH). Although efforts have been made to comprehend the chemical and physical nature of cement paste, studies at molecular level have primarily been focused on individual components. Present research focuses on the development of a method to model, at molecular level, and analysis of the two-phase combination of hydrated and unhydrated phases of cement paste as macromolecular systems. Computational molecular modeling could help in understanding the influence of the phase interactions on the material properties, and mechanical performance of cement paste. Present work also strives to create a framework for molecular level models suitable for potential better comparisons with low length scale experimental methods, in which the sizes of the samples involve the mixture of different hydrated and unhydrated crystalline phases of cement paste. Two approaches based on two-phase cement paste macromolecular structures, one involving admixed molecular phases, and the second involving cluster of two molecular phases are investigated. The mechanical properties of two-phase macromolecular systems of cement paste consisting of key hydrated phase CSH and unhydrated phases C3S or C2S, as well as CSH with the second hydrated phase CH were calculated. It was found that these cement paste two-phase macromolecular systems predicted an isotropic material behavior. Also

  2. Synthesis of Hydrophobic, Crosslinkable Resins.

    Science.gov (United States)

    1985-12-01

    product by methanol precipitation the majority of the first oligomer was L-"- lost. 4.14 DIFFERENTIAL SCANNING CALORIMETRY. The DSC trace of a typical...polymer from the DSC traces obtained to dcte. Preliminary studies using an automated torsional pendulum indicate that the Tg of the crosslinked polymer is...enabling water to be used in the purification steps. The diethyl phosphonates are readily prepared by heating triethyl phosphite with the chloromethyl

  3. Destruction and cross-linking of dextran during γ-radiolysis of its aqueous solutions. Effect of hydrogen ions

    International Nuclear Information System (INIS)

    Kovalev, G.V.; Sinitsin, A.P.; Bugaenko, L.T.

    2000-01-01

    Conditions of primary proceeding either cross-linking process or destruction one during γ-radiolysis in the range of 0-0.32 MGy doses of acid aqueous solutions of dextran macromolecules (P W =930) are determined by the methods of viscosimetry and gel-chromatography. It is shown that initial acidification of dextran solutions results in increasing of the role of cross-linking of macromolecules in the process of formation of molecular-mass distribution of the polymer but continued acidification promotes destruction. It is established that the former is caused by transformation of hydrated electron in hydrogen atoms and the second - by catalytic effect of protons on macromolecular destruction of primary macroradicals being accompanied by breakage of glucoside bonds. It is shown that so far as dextran concentration increase transmission of radical center can to occur on macroradical-macromolecule reaction. As a result macroradical able to monomolecular decomposition transforms in macroradical not able to this transformation [ru

  4. Workshop on algorithms for macromolecular modeling. Final project report, June 1, 1994--May 31, 1995

    Energy Technology Data Exchange (ETDEWEB)

    Leimkuhler, B.; Hermans, J.; Skeel, R.D.

    1995-07-01

    A workshop was held on algorithms and parallel implementations for macromolecular dynamics, protein folding, and structural refinement. This document contains abstracts and brief reports from that workshop.

  5. The contrasting effect of macromolecular crowding on amyloid fibril formation.

    Directory of Open Access Journals (Sweden)

    Qian Ma

    Full Text Available Amyloid fibrils associated with neurodegenerative diseases can be considered biologically relevant failures of cellular quality control mechanisms. It is known that in vivo human Tau protein, human prion protein, and human copper, zinc superoxide dismutase (SOD1 have the tendency to form fibril deposits in a variety of tissues and they are associated with different neurodegenerative diseases, while rabbit prion protein and hen egg white lysozyme do not readily form fibrils and are unlikely to cause neurodegenerative diseases. In this study, we have investigated the contrasting effect of macromolecular crowding on fibril formation of different proteins.As revealed by assays based on thioflavin T binding and turbidity, human Tau fragments, when phosphorylated by glycogen synthase kinase-3β, do not form filaments in the absence of a crowding agent but do form fibrils in the presence of a crowding agent, and the presence of a strong crowding agent dramatically promotes amyloid fibril formation of human prion protein and its two pathogenic mutants E196K and D178N. Such an enhancing effect of macromolecular crowding on fibril formation is also observed for a pathological human SOD1 mutant A4V. On the other hand, rabbit prion protein and hen lysozyme do not form amyloid fibrils when a crowding agent at 300 g/l is used but do form fibrils in the absence of a crowding agent. Furthermore, aggregation of these two proteins is remarkably inhibited by Ficoll 70 and dextran 70 at 200 g/l.We suggest that proteins associated with neurodegenerative diseases are more likely to form amyloid fibrils under crowded conditions than in dilute solutions. By contrast, some of the proteins that are not neurodegenerative disease-associated are unlikely to misfold in crowded physiological environments. A possible explanation for the contrasting effect of macromolecular crowding on these two sets of proteins (amyloidogenic proteins and non-amyloidogenic proteins has been

  6. Structural analysis of nanoparticulate carriers for encapsulation of macromolecular drugs

    Czech Academy of Sciences Publication Activity Database

    Angelov, Borislav; Garamus, V.M.; Drechsler, M.; Angelova, A.

    2017-01-01

    Roč. 235, Jun (2017), s. 83-89 ISSN 0167-7322 R&D Projects: GA MŠk EF15_003/0000447; GA MŠk EF15_008/0000162 Grant - others:OP VVV - ELIBIO(XE) CZ.02.1.01/0.0/0.0/15_003/0000447; ELI Beamlines(XE) CZ.02.1.01/0.0/0.0/15_008/0000162 Institutional support: RVO:68378271 Keywords : self-assembled nanocarriers * liquid crystalline phase transitions * cationic lipids * macromolecular drugs Subject RIV: BO - Biophysics OBOR OECD: Biophysics Impact factor: 3.648, year: 2016

  7. Bringing macromolecular machinery to life using 3D animation.

    Science.gov (United States)

    Iwasa, Janet H

    2015-04-01

    Over the past decade, there has been a rapid rise in the use of three-dimensional (3D) animation to depict molecular and cellular processes. Much of the growth in molecular animation has been in the educational arena, but increasingly, 3D animation software is finding its way into research laboratories. In this review, I will discuss a number of ways in which 3d animation software can play a valuable role in visualizing and communicating macromolecular structures and dynamics. I will also consider the challenges of using animation tools within the research sphere. Copyright © 2015. Published by Elsevier Ltd.

  8. Protein crystal growth studies at the Center for Macromolecular Crystallography

    International Nuclear Information System (INIS)

    DeLucas, Lawrence J.; Long, Marianna M.; Moore, Karen M.; Harrington, Michael; McDonald, William T.; Smith, Craig D.; Bray, Terry; Lewis, Johanna; Crysel, William B.; Weise, Lance D.

    2000-01-01

    The Center for Macromolecular Crystallography (CMC) has been involved in fundamental studies of protein crystal growth (PCG) in microgravity and in our earth-based laboratories. A large group of co-investigators from academia and industry participated in these experiments by providing protein samples and by performing the x-ray crystallographic analysis. These studies have clearly demonstrated the usefulness of a microgravity environment for enhancing the quality and size of protein crystals. Review of the vapor diffusion (VDA) PCG results from nineteen space shuttle missions is given in this paper

  9. Endothelial cell seeding on crosslinked collagen : Effects of crosslinking on endothelial cell proliferation and functional parameters

    NARCIS (Netherlands)

    Wissink, MJB; van Luyn, MJA; Dijk, F; Poot, AA; Engbers, GHM; Beugeling, T; van Aken, WG; Feijen, J

    Endothelial cell seeding, a promising method to improve the performance of small-diameter vascular grafts, requires a suitable substrate, such as crosslinked collagen. Commonly used crosslinking agents such as glutaraldehyde and formaldehyde cause, however, cytotoxic reactions and thereby hamper

  10. Thiomers for oral delivery of hydrophilic macromolecular drugs.

    Science.gov (United States)

    Bernkop-Schnürch, Andreas; Hoffer, Martin H; Kafedjiiski, Krum

    2004-11-01

    In recent years thiolated polymers (thiomers) have appeared as a promising new tool in oral drug delivery. Thiomers are obtained by the immobilisation of thio-bearing ligands to mucoadhesive polymeric excipients. By the formation of disulfide bonds with mucus glycoproteins, the mucoadhesive properties of thiomers are up to 130-fold improved compared with the corresponding unmodified polymers. Owing to the formation of inter- and intramolecular disulfide bonds within the thiomer itself, matrix tablets and particulate delivery systems show strong cohesive properties, resulting in comparatively higher stability, prolonged disintegration times and a more controlled drug release. The permeation of hydrophilic macromolecular drugs through the gastrointestinal (GI) mucosa can be improved by the use of thiomers. Furthermore, some thiomers exhibit improved inhibitory properties towards GI peptidases. The efficacy of thiomers in oral drug delivery has been demonstrated by various in vivo studies. A pharmacological efficacy of 1%, for example, was achieved in rats by oral administration of calcitonin tablets comprising a thiomer. Furthermore, tablets comprising a thiomer and pegylated insulin resulted in a pharmacological efficacy of 7% after oral application to diabetic mice. Low-molecular-weight heparin embedded in thiolated polycarbophil led to an absolute bioavailability of > or = 20% after oral administration to rats. In these studies, formulations comprising the corresponding unmodified polymer had only a marginal or no effect. These results indicate drug carrier systems based on thiomers appear to be a promising tool for oral delivery of hydrophilic macromolecular drugs.

  11. Outrunning free radicals in room-temperature macromolecular crystallography

    Energy Technology Data Exchange (ETDEWEB)

    Owen, Robin L., E-mail: robin.owen@diamond.ac.uk; Axford, Danny [Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom); Nettleship, Joanne E.; Owens, Raymond J. [Rutherford Appleton Laboratory, Didcot OX11 0FA (United Kingdom); The Henry Wellcome Building for Genomic Medicine, Roosevelt Drive, Oxford OX3 7BN (United Kingdom); Robinson, James I.; Morgan, Ann W. [University of Leeds, Leeds LS9 7FT (United Kingdom); Doré, Andrew S. [Heptares Therapeutics Ltd, BioPark, Welwyn Garden City AL7 3AX (United Kingdom); Lebon, Guillaume; Tate, Christopher G. [MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH (United Kingdom); Fry, Elizabeth E.; Ren, Jingshan [The Henry Wellcome Building for Genomic Medicine, Roosevelt Drive, Oxford OX3 7BN (United Kingdom); Stuart, David I. [Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom); The Henry Wellcome Building for Genomic Medicine, Roosevelt Drive, Oxford OX3 7BN (United Kingdom); Evans, Gwyndaf [Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom)

    2012-06-15

    A systematic increase in lifetime is observed in room-temperature protein and virus crystals through the use of reduced exposure times and a fast detector. A significant increase in the lifetime of room-temperature macromolecular crystals is reported through the use of a high-brilliance X-ray beam, reduced exposure times and a fast-readout detector. This is attributed to the ability to collect diffraction data before hydroxyl radicals can propagate through the crystal, fatally disrupting the lattice. Hydroxyl radicals are shown to be trapped in amorphous solutions at 100 K. The trend in crystal lifetime was observed in crystals of a soluble protein (immunoglobulin γ Fc receptor IIIa), a virus (bovine enterovirus serotype 2) and a membrane protein (human A{sub 2A} adenosine G-protein coupled receptor). The observation of a similar effect in all three systems provides clear evidence for a common optimal strategy for room-temperature data collection and will inform the design of future synchrotron beamlines and detectors for macromolecular crystallography.

  12. Outrunning free radicals in room-temperature macromolecular crystallography

    International Nuclear Information System (INIS)

    Owen, Robin L.; Axford, Danny; Nettleship, Joanne E.; Owens, Raymond J.; Robinson, James I.; Morgan, Ann W.; Doré, Andrew S.; Lebon, Guillaume; Tate, Christopher G.; Fry, Elizabeth E.; Ren, Jingshan; Stuart, David I.; Evans, Gwyndaf

    2012-01-01

    A systematic increase in lifetime is observed in room-temperature protein and virus crystals through the use of reduced exposure times and a fast detector. A significant increase in the lifetime of room-temperature macromolecular crystals is reported through the use of a high-brilliance X-ray beam, reduced exposure times and a fast-readout detector. This is attributed to the ability to collect diffraction data before hydroxyl radicals can propagate through the crystal, fatally disrupting the lattice. Hydroxyl radicals are shown to be trapped in amorphous solutions at 100 K. The trend in crystal lifetime was observed in crystals of a soluble protein (immunoglobulin γ Fc receptor IIIa), a virus (bovine enterovirus serotype 2) and a membrane protein (human A 2A adenosine G-protein coupled receptor). The observation of a similar effect in all three systems provides clear evidence for a common optimal strategy for room-temperature data collection and will inform the design of future synchrotron beamlines and detectors for macromolecular crystallography

  13. Variable effects of soman on macromolecular secretion by ferret trachea

    International Nuclear Information System (INIS)

    McBride, R.K.; Zwierzynski, D.J.; Stone, K.K.; Culp, D.J.; Marin, M.G.

    1991-01-01

    The purpose of this study was to examine the effect of the anticholinesterase agent, soman, on macromolecular secretion by ferret trachea, in vitro. We mounted pieces of ferret trachea in Ussing-type chambers. Secreted sulfated macromolecules were radiolabeled by adding 500 microCi of 35 SO 4 to the submucosal medium and incubating for 17 hr. Soman added to the submucosal side produced a concentration-dependent increase in radiolabeled macromolecular release with a maximal secretory response (mean +/- SD) of 202 +/- 125% (n = 8) relative to the basal secretion rate at a concentration of 10 - 7 M. The addition of either 10 -6 M pralidoxime (acetylcholinesterase reactivator) or 10 -6 M atropine blocked the response to 10 -7 M soman. At soman concentrations greater than 10 -7 M, secretion rate decreased and was not significantly different from basal secretion. Additional experiments utilizing acetylcholine and the acetylcholinesterase inhibitor, physostigmine, suggest that inhibition of secretion by high concentrations of soman may be due to a secondary antagonistic effect of soman on muscarinic receptors

  14. Dendrimer-based Macromolecular MRI Contrast Agents: Characteristics and Application

    Directory of Open Access Journals (Sweden)

    Hisataka Kobayashi

    2003-01-01

    Full Text Available Numerous macromolecular MRI contrast agents prepared employing relatively simple chemistry may be readily available that can provide sufficient enhancement for multiple applications. These agents operate using a ~100-fold lower concentration of gadolinium ions in comparison to the necessary concentration of iodine employed in CT imaging. Herein, we describe some of the general potential directions of macromolecular MRI contrast agents using our recently reported families of dendrimer-based agents as examples. Changes in molecular size altered the route of excretion. Smaller-sized contrast agents less than 60 kDa molecular weight were excreted through the kidney resulting in these agents being potentially suitable as functional renal contrast agents. Hydrophilic and larger-sized contrast agents were found better suited for use as blood pool contrast agents. Hydrophobic variants formed with polypropylenimine diaminobutane dendrimer cores created liver contrast agents. Larger hydrophilic agents are useful for lymphatic imaging. Finally, contrast agents conjugated with either monoclonal antibodies or with avidin are able to function as tumor-specific contrast agents, which also might be employed as therapeutic drugs for either gadolinium neutron capture therapy or in conjunction with radioimmunotherapy.

  15. PRIGo: a new multi-axis goniometer for macromolecular crystallography

    Energy Technology Data Exchange (ETDEWEB)

    Waltersperger, Sandro; Olieric, Vincent, E-mail: vincent.olieric@psi.ch; Pradervand, Claude [Paul Scherrer Institute, Villigen PSI (Switzerland); Glettig, Wayne [Centre Suisse d’Electronique et Microtechnique SA, Neuchâtel 2002 (Switzerland); Salathe, Marco; Fuchs, Martin R.; Curtin, Adrian; Wang, Xiaoqiang; Ebner, Simon; Panepucci, Ezequiel; Weinert, Tobias [Paul Scherrer Institute, Villigen PSI (Switzerland); Schulze-Briese, Clemens [Dectris Ltd, Baden 5400 (Switzerland); Wang, Meitian, E-mail: vincent.olieric@psi.ch [Paul Scherrer Institute, Villigen PSI (Switzerland)

    2015-05-09

    The design and performance of the new multi-axis goniometer PRIGo developed at the Swiss Light Source at Paul Scherrer Institute is described. The Parallel Robotics Inspired Goniometer (PRIGo) is a novel compact and high-precision goniometer providing an alternative to (mini-)kappa, traditional three-circle goniometers and Eulerian cradles used for sample reorientation in macromolecular crystallography. Based on a combination of serial and parallel kinematics, PRIGo emulates an arc. It is mounted on an air-bearing stage for rotation around ω and consists of four linear positioners working synchronously to achieve x, y, z translations and χ rotation (0–90°), followed by a ϕ stage (0–360°) for rotation around the sample holder axis. Owing to the use of piezo linear positioners and active correction, PRIGo features spheres of confusion of <1 µm, <7 µm and <10 µm for ω, χ and ϕ, respectively, and is therefore very well suited for micro-crystallography. PRIGo enables optimal strategies for both native and experimental phasing crystallographic data collection. Herein, PRIGo hardware and software, its calibration, as well as applications in macromolecular crystallography are described.

  16. Data Management System at the Photon Factory Macromolecular Crystallography Beamline

    International Nuclear Information System (INIS)

    Yamada, Y; Matsugaki, N; Chavas, L M G; Hiraki, M; Igarashi, N; Wakatsuki, S

    2013-01-01

    Macromolecular crystallography is a very powerful tool to investigate three-dimensional structures of macromolecules at the atomic level, and is widely spread among structural biology researchers. Due to recent upgrades of the macromolecular crystallography beamlines at the Photon Factory, beamline throughput has improved, allowing more experiments to be conducted during a user's beam time. Although the number of beamlines has increased, so has the number of beam time applications. Consequently, both the experimental data from users' experiments and data derived from beamline operations have dramatically increased, causing difficulties in organizing these diverse and large amounts of data for the beamline operation staff and users. To overcome this problem, we have developed a data management system by introducing commercial middleware, which consists of a controller, database, and web servers. We have prepared several database projects using this system. Each project is dedicated to a certain aspect such as experimental results, beam time applications, beam time schedule, or beamline operation reports. Then we designed a scheme to link all the database projects.

  17. Enzymes as Green Catalysts for Precision Macromolecular Synthesis.

    Science.gov (United States)

    Shoda, Shin-ichiro; Uyama, Hiroshi; Kadokawa, Jun-ichi; Kimura, Shunsaku; Kobayashi, Shiro

    2016-02-24

    The present article comprehensively reviews the macromolecular synthesis using enzymes as catalysts. Among the six main classes of enzymes, the three classes, oxidoreductases, transferases, and hydrolases, have been employed as catalysts for the in vitro macromolecular synthesis and modification reactions. Appropriate design of reaction including monomer and enzyme catalyst produces macromolecules with precisely controlled structure, similarly as in vivo enzymatic reactions. The reaction controls the product structure with respect to substrate selectivity, chemo-selectivity, regio-selectivity, stereoselectivity, and choro-selectivity. Oxidoreductases catalyze various oxidation polymerizations of aromatic compounds as well as vinyl polymerizations. Transferases are effective catalysts for producing polysaccharide having a variety of structure and polyesters. Hydrolases catalyzing the bond-cleaving of macromolecules in vivo, catalyze the reverse reaction for bond forming in vitro to give various polysaccharides and functionalized polyesters. The enzymatic polymerizations allowed the first in vitro synthesis of natural polysaccharides having complicated structures like cellulose, amylose, xylan, chitin, hyaluronan, and chondroitin. These polymerizations are "green" with several respects; nontoxicity of enzyme, high catalyst efficiency, selective reactions under mild conditions using green solvents and renewable starting materials, and producing minimal byproducts. Thus, the enzymatic polymerization is desirable for the environment and contributes to "green polymer chemistry" for maintaining sustainable society.

  18. Progress in rational methods of cryoprotection in macromolecular crystallography

    International Nuclear Information System (INIS)

    Alcorn, Thomas; Juers, Douglas H.

    2010-01-01

    Measurements of the average thermal contractions (294→72 K) of 26 different cryosolutions are presented and discussed in conjunction with other recent advances in the rational design of protocols for cryogenic cooling in macromolecular crystallography. Cryogenic cooling of macromolecular crystals is commonly used for X-ray data collection both to reduce crystal damage from radiation and to gather functional information by cryogenically trapping intermediates. However, the cooling process can damage the crystals. Limiting cooling-induced crystal damage often requires cryoprotection strategies, which can involve substantial screening of solution conditions and cooling protocols. Here, recent developments directed towards rational methods for cryoprotection are described. Crystal damage is described in the context of the temperature response of the crystal as a thermodynamic system. As such, the internal and external parts of the crystal typically have different cryoprotection requirements. A key physical parameter, the thermal contraction, of 26 different cryoprotective solutions was measured between 294 and 72 K. The range of contractions was 2–13%, with the more polar cryosolutions contracting less. The potential uses of these results in the development of cryocooling conditions, as well as recent developments in determining minimum cryosolution soaking times, are discussed

  19. Radiation induced estane polymer crosslinking

    International Nuclear Information System (INIS)

    Fletcher, M.; Foster, P.

    1997-01-01

    The exposure of polymeric materials to radiation has been known to induce the effects of crosslinking and degradation. The crosslinking phenomena comes about when two long chain polymers become linked together by a primary bond that extends the chain and increases the viscosity, molecular weight and the elastic modules of the polymer. This process has been observed in relatively short periods of time with fairly high doses of radiation, on the order of several megarads/hour. This paper address low dose exposure over long periods of time to determine what the radiation effects are on the polymeric binder material in PBX 9501. An experimental sample of binder material without explosives will be placed into a thermal and radiation field produced from a W-48 put mod 0. Another sample will be placed in a thermal environment without the radiation. The following is the test plan that was submitted to the Pantex process. The data presented here will be from the first few weeks of exposure and this test will be continued over the next few years. Subsequent data will hopefully be presented in the next compatibility and aging conference

  20. Preparation of the Crosslinked Polyethersulfone Films by High Temperature Electron-Beam Irradiation

    International Nuclear Information System (INIS)

    Li, J.

    2006-01-01

    The aromatic polymers, mainly so called engineering plastics, were famed for the good stability under irradiation. However, high temperature irradiation of the aromatic polymers can result the crosslinked structure, due to the improved molecular mobility. Polyethersulfone (PES) is a wide used engineering plastic because of the high performance and high thermal stability. PES films were irradiated by electron-beam under nitrogen atmosphere above the glass transition temperature and then the covalently crosslinked PES (RX-PES) films were obtained. The irradiations were also performed at ambient temperature for comparison. The network structure formation of the RX-PES films was confirmed by the appearance of the gel, which were measured by soaking the irradiated PES films in the N,N-dimethylformamide (DMF) at room temperature. When the PES films were irradiated to 300 kGy, there was gel appeared. The gel percent increased with the increasing in the absorbed dose, and saturated when the absorbed dose exceeded 1200 kGy. However, there was no gel formed for the PES films irradiated at ambient temperature even to 2250 kGy. The G(S) and G(X) were calculated according to the Y-crosslinking mechanism. The results values are consistent in error range. G(S) of 0.10 and G(X) of 0.23 were obtained. As calculated, almost all the macromolecular radicals produced by chain scission were used for crosslinking. Also, the glass transition temperature of the RX-PES films increased with the increasing in the absorbed doses, while the glass transition temperature of the PES films irradiated at ambient temperature decreased with the increasing in the absorbed doses. The blending films of the PES with FEP or ETFE were prepared and the high temperature irradiation effects were also studies

  1. Macromolecular crowding directs extracellular matrix organization and mesenchymal stem cell behavior.

    Directory of Open Access Journals (Sweden)

    Adam S Zeiger

    Full Text Available Microenvironments of biological cells are dominated in vivo by macromolecular crowding and resultant excluded volume effects. This feature is absent in dilute in vitro cell culture. Here, we induced macromolecular crowding in vitro by using synthetic macromolecular globules of nm-scale radius at physiological levels of fractional volume occupancy. We quantified the impact of induced crowding on the extracellular and intracellular protein organization of human mesenchymal stem cells (MSCs via immunocytochemistry, atomic force microscopy (AFM, and AFM-enabled nanoindentation. Macromolecular crowding in extracellular culture media directly induced supramolecular assembly and alignment of extracellular matrix proteins deposited by cells, which in turn increased alignment of the intracellular actin cytoskeleton. The resulting cell-matrix reciprocity further affected adhesion, proliferation, and migration behavior of MSCs. Macromolecular crowding can thus aid the design of more physiologically relevant in vitro studies and devices for MSCs and other cells, by increasing the fidelity between materials synthesized by cells in vivo and in vitro.

  2. Macromolecular crowding directs extracellular matrix organization and mesenchymal stem cell behavior.

    Science.gov (United States)

    Zeiger, Adam S; Loe, Felicia C; Li, Ran; Raghunath, Michael; Van Vliet, Krystyn J

    2012-01-01

    Microenvironments of biological cells are dominated in vivo by macromolecular crowding and resultant excluded volume effects. This feature is absent in dilute in vitro cell culture. Here, we induced macromolecular crowding in vitro by using synthetic macromolecular globules of nm-scale radius at physiological levels of fractional volume occupancy. We quantified the impact of induced crowding on the extracellular and intracellular protein organization of human mesenchymal stem cells (MSCs) via immunocytochemistry, atomic force microscopy (AFM), and AFM-enabled nanoindentation. Macromolecular crowding in extracellular culture media directly induced supramolecular assembly and alignment of extracellular matrix proteins deposited by cells, which in turn increased alignment of the intracellular actin cytoskeleton. The resulting cell-matrix reciprocity further affected adhesion, proliferation, and migration behavior of MSCs. Macromolecular crowding can thus aid the design of more physiologically relevant in vitro studies and devices for MSCs and other cells, by increasing the fidelity between materials synthesized by cells in vivo and in vitro.

  3. Chemical cross-linking of Chlamydia trachomatis

    DEFF Research Database (Denmark)

    Birkelund, Svend; Lundemose, AG; Christiansen, Gunna

    1988-01-01

    Purified elementary bodies (EBs) of Chlamydia trachomatis serovar L2 were analyzed by chemical cross-linking with disuccinimidyl selenodipropionate. The effect of the cross-linking was analyzed by immunoblotting sodium dodecyl sulfate-polyacrylamide gel electrophoresis-separated components which...

  4. Poly(tetramethyleneterephthalate) crosslinked by irradiation

    International Nuclear Information System (INIS)

    Nyberg, D.D.

    1978-01-01

    Crosslinking, e.g., by irradiation, of a polymer comprising poly(tetramethyleneterephthalate) is made possible by the addition of a member selected from the group consisting of triallyl cyanurate and N,N'-m-phenylenedimaleimide. The resulting crosslinked modified polymer may be rendered heat recoverable

  5. Formation of interfacial network structure via photo-crosslinking in carbon fiber/epoxy composites

    Directory of Open Access Journals (Sweden)

    S. H. Deng

    2014-07-01

    Full Text Available A series of diblock copolymers (poly(n-butylacrylate-co-poly(2-hydroxyethyl acrylate-b-poly(glycidyl methacrylate ((PnBA-co-PHEA-b-PGMA, containing a random copolymer block PnBA-co-PHEA, were successfully synthesized by atom transfer radical polymerization (ATRP. After being chemically grafted onto carbon fibers, the photosensitive methacrylic groups were introduced into the random copolymer, giving a series of copolymers (poly(n-butylacrylate-co-poly(2-methacryloyloxyethyl acrylate-b-poly(glycidyl methacrylate((PnBA-co-PMEA-b-PGMA. Dynamic mechanical analysis indicated that the random copolymer block after ultraviolet (UV irradiation was a lightly crosslinked polymer and acted as an elastomer, forming a photo-crosslinked network structure at the interface of carbon fiber/epoxy composites. Microbond test showed that such an interfacial network structure greatly improved the cohesive strength and effectively controlled the deformation ability of the flexible interlayer. Furthermore, three kinds of interfacial network structures, i physical crosslinking by H-bonds, ii chemical crosslinking by photopolymerization, and iii interpenetrating crosslinked network by photopolymerization and epoxy curing reaction were received in carbon fiber/epoxy composite, depending on the various preparation processes.

  6. Cross-linking of polymeric materials

    International Nuclear Information System (INIS)

    Bloom, L.I.; Du Plessis, T.A.; Meij, G.O.

    1991-01-01

    The invention provides a method of producing a cured polymeric artifact from a polymeric thermoplastic starting material, the material of the artifact having reduced thermoplasticity relative to the starting material and exhibiting an enhanced degree of cross-linking relative to the starting material. The method includes subjecting a polymeric thermoplastic starting material, which is capable of being cross-linked by irradiation, to sufficient irradiation partially to cross-linked the starting material to produce a thermoplastic partially cross-linked intermediate material. The thermoplasticity of the intermediate material is then reduced by heating it to raise its melting point. The invention also provides a method of making a partially cross-linked feedstocks and a master batch for use in making such artifacts

  7. The role of crosslinkers in epoxy-amine crosslinked silicon sol-gel barrier protection coatings

    International Nuclear Information System (INIS)

    Vreugdenhil, A.J.; Gelling, V.J.; Woods, M.E.; Schmelz, J.R.; Enderson, B.P.

    2008-01-01

    The search for chromate replacements in corrosion prevention materials has identified the use of hybrid sol-gel coatings as one, very promising approach. Appropriately functionalized hybrid sol-gel materials can be crosslinked to enhance their chemical durability and mechanical strength. In this work, we evaluate three crosslinkers used in a tetramethoxysilane-glycidoxypropyltrimethoxysilane binary sol-gel system in order to identify the role of the crosslinkers in corrosion protection. The crosslinkers examined were ethylenediamine, N-aminethylepiperazine, and diethylenetriamine. The sol-gel coatings were examined by contact angle, atomic force microscopy, and electrochemical impedance spectroscopy (EIS). Circuit modeling of the EIS results yielded valuable insights into the significant differences between the durabilities of the variously crosslinked coatings. Crosslinker hydrophobicity was identified as not playing a significant role whereas the number of reactive sites per crosslinker and the resulting morphology of the material may be an important parameter

  8. New insight on aliphatic linkages in the macromolecular organic fraction of Orgueil and Murchison meteorites through ruthenium tetroxide oxidation

    Science.gov (United States)

    Remusat, Laurent; Derenne, Sylvie; Robert, François

    2005-09-01

    Ruthenium tetroxide oxidation was used to examine the macromolecular insoluble organic matter (IOM) from the Orgueil and Murchison meteorites and especially to characterize the aliphatic linkages. Already applied to various terrestrial samples, ruthenium tetroxide is a selective oxidant which destroys aromatic units, converting them into CO 2, and yields aliphatic and aromatic acids. In our experiment on chondritic IOM, it produces mainly short aliphatic diacids and polycarboxylic aromatic acids. Some short hydroxyacids are also detected. Aliphatic diacids are interpreted as aliphatic bridges between aromatic units in the chemical structure, and polycarboxylic aromatic acids are the result of the fusion of polyaromatic units. The product distribution shows that aliphatic links are short with numerous substitutions. No indigenous monocarboxylic acid was detected, showing that free aliphatic chains must be very short (less than three carbon atoms). The hydroxyacids are related to the occurrence of ester and ether functional groups within the aliphatic bridges between the aromatic units. This technique thus allows us to characterize in detail the aliphatic linkages of the IOMs, and the derived conclusions are in agreement with spectroscopic, pyrolytic, and degradative results previously reported. Compared to terrestrial samples, the aliphatic part of chondritic IOM is shorter and highly substituted. Aromatic units are smaller and more cross-linked than in coals, as already proposed from NMR data. Orgueil and Murchison IOM exhibit some tiny differences, especially in the length of aliphatic chains.

  9. In-vacuum long-wavelength macromolecular crystallography.

    Science.gov (United States)

    Wagner, Armin; Duman, Ramona; Henderson, Keith; Mykhaylyk, Vitaliy

    2016-03-01

    Structure solution based on the weak anomalous signal from native (protein and DNA) crystals is increasingly being attempted as part of synchrotron experiments. Maximizing the measurable anomalous signal by collecting diffraction data at longer wavelengths presents a series of technical challenges caused by the increased absorption of X-rays and larger diffraction angles. A new beamline at Diamond Light Source has been built specifically for collecting data at wavelengths beyond the capability of other synchrotron macromolecular crystallography beamlines. Here, the theoretical considerations in support of the long-wavelength beamline are outlined and the in-vacuum design of the endstation is discussed, as well as other hardware features aimed at enhancing the accuracy of the diffraction data. The first commissioning results, representing the first in-vacuum protein structure solution, demonstrate the promising potential of the beamline.

  10. Efficient analysis of macromolecular rotational diffusion from heteronuclear relaxation data

    International Nuclear Information System (INIS)

    Dosset, Patrice; Hus, Jean-Christophe; Blackledge, Martin; Marion, Dominique

    2000-01-01

    A novel program has been developed for the interpretation of 15 N relaxation rates in terms of macromolecular anisotropic rotational diffusion. The program is based on a highly efficient simulated annealing/minimization algorithm, designed specifically to search the parametric space described by the isotropic, axially symmetric and fully anisotropic rotational diffusion tensor models. The high efficiency of this algorithm allows extensive noise-based Monte Carlo error analysis. Relevant statistical tests are systematically applied to provide confidence limits for the proposed tensorial models. The program is illustrated here using the example of the cytochrome c' from Rhodobacter capsulatus, a four-helix bundle heme protein, for which data at three different field strengths were independently analysed and compared

  11. Macromolecular Crystallization in Microfluidics for the International Space Station

    Science.gov (United States)

    Monaco, Lisa A.; Spearing, Scott

    2003-01-01

    At NASA's Marshall Space Flight Center, the Iterative Biological Crystallization (IBC) project has begun development on scientific hardware for macromolecular crystallization on the International Space Station (ISS). Currently ISS crystallization research is limited to solution recipes that were prepared on the ground prior to launch. The proposed hardware will conduct solution mixing and dispensing on board the ISS, be fully automated, and have imaging functions via remote commanding from the ground. Utilizing microfluidic technology, IBC will allow for on orbit iterations. The microfluidics LabChip(R) devices that have been developed, along with Caliper Technologies, will greatly benefit researchers by allowing for precise fluid handling of nano/pico liter sized volumes. IBC will maximize the amount of science return by utilizing the microfluidic approach and be a valuable tool to structural biologists investigating medically relevant projects.

  12. Macromolecular and dendrimer-based magnetic resonance contrast agents

    Energy Technology Data Exchange (ETDEWEB)

    Bumb, Ambika; Brechbiel, Martin W. (Radiation Oncology Branch, National Cancer Inst., National Inst. of Health, Bethesda, MD (United States)), e-mail: pchoyke@mail.nih.gov; Choyke, Peter (Molecular Imaging Program, National Cancer Inst., National Inst. of Health, Bethesda, MD (United States))

    2010-09-15

    Magnetic resonance imaging (MRI) is a powerful imaging modality that can provide an assessment of function or molecular expression in tandem with anatomic detail. Over the last 20-25 years, a number of gadolinium-based MR contrast agents have been developed to enhance signal by altering proton relaxation properties. This review explores a range of these agents from small molecule chelates, such as Gd-DTPA and Gd-DOTA, to macromolecular structures composed of albumin, polylysine, polysaccharides (dextran, inulin, starch), poly(ethylene glycol), copolymers of cystamine and cystine with GD-DTPA, and various dendritic structures based on polyamidoamine and polylysine (Gadomers). The synthesis, structure, biodistribution, and targeting of dendrimer-based MR contrast agents are also discussed

  13. The monitoring system for macromolecular crystallography beamlines at BSRF

    International Nuclear Information System (INIS)

    Guo Xian; Chang Guangcai; Gan Quan; Shi Hong; Liu Peng; Sun Gongxing

    2012-01-01

    The monitoring system for macromolecular crystallography beamlines at BSRF (Beijing Synchrotron Radiation Facility) based on LabVIEW is introduced. In order to guarantee a safe, stable, and reliable running for the beamline devices, the system monitors the state of vacuum, cooling-water, optical components, beam, Liquid nitrogen in the beamlines in real time, detects faults and gives the alarm timely. System underlying uses the driver developed for the field devices for data acquisition, Data of collection is uploaded to the data-sharing platform makes it accessible via a network share. The upper system divides modules according to the actual function, and establishes the main interface of the monitoring system of beamline. To Facilitate data storage, management and inquiry, the system use LabSQL toolkit to achieve the interconnection with MySQL database which data of collection is sent to. (authors)

  14. 129 Xe NMR Relaxation-Based Macromolecular Sensing

    Energy Technology Data Exchange (ETDEWEB)

    Gomes, Muller D. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Dao, Phuong [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Jeong, Keunhong [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Slack, Clancy C. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Vassiliou, Christophoros C. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Finbloom, Joel A. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Francis, Matthew B. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Wemmer, David E. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Physical Biosciences Division; Pines, Alexander [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Chemistry

    2016-07-29

    A 129Xe NMR relaxation-based sensing approach is reported on that exploits changes in the bulk xenon relaxation rate induced by slowed tumbling of a cryptophane-based sensor upon target binding. The amplification afforded by detection of the bulk dissolved xenon allows sensitive detection of targets. The sensor comprises a xenon-binding cryptophane cage, a target interaction element, and a metal chelating agent. Xenon associated with the target-bound cryptophane cage is rapidly relaxed and then detected after exchange with the bulk. Here we show that large macromolecular targets increase the rotational correlation time of xenon, increasing its relaxation rate. Upon binding of a biotin-containing sensor to avidin at 1.5 μM concentration, the free xenon T2 is reduced by a factor of 4.

  15. E-MSD: the European Bioinformatics Institute Macromolecular Structure Database.

    Science.gov (United States)

    Boutselakis, H; Dimitropoulos, D; Fillon, J; Golovin, A; Henrick, K; Hussain, A; Ionides, J; John, M; Keller, P A; Krissinel, E; McNeil, P; Naim, A; Newman, R; Oldfield, T; Pineda, J; Rachedi, A; Copeland, J; Sitnov, A; Sobhany, S; Suarez-Uruena, A; Swaminathan, J; Tagari, M; Tate, J; Tromm, S; Velankar, S; Vranken, W

    2003-01-01

    The E-MSD macromolecular structure relational database (http://www.ebi.ac.uk/msd) is designed to be a single access point for protein and nucleic acid structures and related information. The database is derived from Protein Data Bank (PDB) entries. Relational database technologies are used in a comprehensive cleaning procedure to ensure data uniformity across the whole archive. The search database contains an extensive set of derived properties, goodness-of-fit indicators, and links to other EBI databases including InterPro, GO, and SWISS-PROT, together with links to SCOP, CATH, PFAM and PROSITE. A generic search interface is available, coupled with a fast secondary structure domain search tool.

  16. NATO Advanced Study Institute on Evolving Methods for Macromolecular Gystallography

    CERN Document Server

    Read, Randy J

    2007-01-01

    X-ray crystallography is the pre-eminent technique for visualizing the structures of macromolecules at atomic resolution. These structures are central to understanding the detailed mechanisms of biological processes, and to discovering novel therapeutics using a structure-based approach. As yet, structures are known for only a small fraction of the proteins encoded by human and pathogenic genomes. To counter the myriad modern threats of disease, there is an urgent need to determine the structures of the thousands of proteins whose structure and function remain unknown. This volume draws on the expertise of leaders in the field of macromolecular crystallography to illuminate the dramatic developments that are accelerating progress in structural biology. Their contributions span the range of techniques from crystallization through data collection, structure solution and analysis, and show how modern high-throughput methods are contributing to a deeper understanding of medical problems.

  17. MR lymphography with macromolecular Gd-DTPA compounds

    International Nuclear Information System (INIS)

    Hamm, B.; Wagner, S.; Branding, G.; Taupitz, M.; Wolf, K.J.

    1990-01-01

    This paper investigates the suitability of macromolecular Gd-DTPA compounds as signal-enhancing lymphographic agents in MR imaging. Two Gd-DTPA polylysin compounds and Gd-DTPA albumin, with molecular weights of 48,000,170,000, and 87,000 daltons, respectively, were tested in rabbits at gadolinium doses of 5 and 15 μmol per animal. Three animals were examined at each dose with T1-weighted sequences. The iliac lymph nodes were imaged prior to and during unilateral endolymphatic infusion into a femoral lymph vessel as well as over a period of 2 hours thereafter. All contrast media showed a homogeneous and pronounced signal enhancement in the lymph nodes during infusion at both doses

  18. THESEUS: maximum likelihood superpositioning and analysis of macromolecular structures.

    Science.gov (United States)

    Theobald, Douglas L; Wuttke, Deborah S

    2006-09-01

    THESEUS is a command line program for performing maximum likelihood (ML) superpositions and analysis of macromolecular structures. While conventional superpositioning methods use ordinary least-squares (LS) as the optimization criterion, ML superpositions provide substantially improved accuracy by down-weighting variable structural regions and by correcting for correlations among atoms. ML superpositioning is robust and insensitive to the specific atoms included in the analysis, and thus it does not require subjective pruning of selected variable atomic coordinates. Output includes both likelihood-based and frequentist statistics for accurate evaluation of the adequacy of a superposition and for reliable analysis of structural similarities and differences. THESEUS performs principal components analysis for analyzing the complex correlations found among atoms within a structural ensemble. ANSI C source code and selected binaries for various computing platforms are available under the GNU open source license from http://monkshood.colorado.edu/theseus/ or http://www.theseus3d.org.

  19. Extracting trends from two decades of microgravity macromolecular crystallization history.

    Science.gov (United States)

    Judge, Russell A; Snell, Edward H; van der Woerd, Mark J

    2005-06-01

    Since the 1980s hundreds of macromolecular crystal growth experiments have been performed in the reduced acceleration environment of an orbiting spacecraft. Significant enhancements in structural knowledge have resulted from X-ray diffraction of the crystals grown. Similarly, many samples have shown no improvement or degradation in comparison to those grown on the ground. A complex series of interrelated factors affect these experiments and by building a comprehensive archive of the results it was aimed to identify factors that result in success and those that result in failure. Specifically, it was found that dedicated microgravity missions increase the chance of success when compared with those where crystallization took place as a parasitic aspect of the mission. It was also found that the chance of success could not be predicted based on any discernible property of the macromolecule available to us.

  20. Macromolecular contrast agents for MR mammography: current status

    International Nuclear Information System (INIS)

    Daldrup-Link, Heike E.; Brasch, Robert C.

    2003-01-01

    Macromolecular contrast media (MMCM) encompass a new class of diagnostic drugs that can be applied with dynamic MRI to extract both physiologic and morphologic information in breast lesions. Kinetic analysis of dynamic MMCM-enhanced MR data in breast tumor patients provides useful estimates of tumor blood volume and microvascular permeability, typically increased in cancer. These tumor characteristics can be applied to differentiate benign from malignant lesions, to define the angiogenesis status of cancers, and to monitor tumor response to therapy. The most immediate challenge to the development of MMCM-enhanced mammography is the identification of those candidate compounds that demonstrate the requisite long intravascular distribution and have the high tolerance necessary for clinical use. Potential mammographic applications and limitations of various MMCM, defined by either experimental animal testing or clinical testing in patients, are reviewed in this article. (orig.)

  1. Macromolecular organization of xyloglucan and cellulose in pea epicotyls

    International Nuclear Information System (INIS)

    Hayashi, T.; Maclachlan, G.

    1984-01-01

    Xyloglucan is known to occur widely in the primary cell walls of higher plants. This polysaccharide in most dicots possesses a cellulose-like main chain with three of every four consecutive residues substituted with xylose and minor addition of other sugars. Xyloglucan and cellulose metabolism is regulated by different processes; since different enzyme systems are probably required for the synthesis of their 1,4-β-linkages. A macromolecular complex composed of xyloglucan and cellulose only was obtained from elongating regions of etiolated pea stems. It was examined by light microscopy using iodine staining, by radioautography after labeling with [ 3 H]fructose, by fluorescence microscopy using a fluorescein-lectin (fructose-binding) as probe, and by electron microscopy after shadowing. The techniques all demonstrated that the macromolecule was present in files of cell shapes, referred to here as cell-wall ghosts, in which xyloglucan was localized both on and between the cellulose microfibrils

  2. Probing the hydration water diffusion of macromolecular surfaces and interfaces

    International Nuclear Information System (INIS)

    Ortony, Julia H; Cheng, Chi-Yuan; Franck, John M; Pavlova, Anna; Hunt, Jasmine; Han, Songi; Kausik, Ravinath

    2011-01-01

    We probe the translational dynamics of the hydration water surrounding the macromolecular surfaces of selected polyelectrolytes, lipid vesicles and intrinsically disordered proteins with site specificity in aqueous solutions. These measurements are made possible by the recent development of a new instrumental and methodological approach based on Overhauser dynamic nuclear polarization (DNP)-enhanced nuclear magnetic resonance (NMR) spectroscopy. This technique selectively amplifies 1 H NMR signals of hydration water around a spin label that is attached to a molecular site of interest. The selective 1 H NMR amplification within molecular length scales of a spin label is achieved by utilizing short-distance range (∼r -3 ) magnetic dipolar interactions between the 1 H spin of water and the electron spin of a nitroxide radical-based label. Key features include the fact that only minute quantities (<10 μl) and dilute (≥100 μM) sample concentrations are needed. There is no size limit on the macromolecule or molecular assembly to be analyzed. Hydration water with translational correlation times between 10 and 800 ps is measured within ∼10 A distance of the spin label, encompassing the typical thickness of a hydration layer with three water molecules across. The hydration water moving within this time scale has significant implications, as this is what is modulated whenever macromolecules or molecular assemblies undergo interactions, binding or conformational changes. We demonstrate, with the examples of polymer complexation, protein aggregation and lipid-polymer interaction, that the measurements of interfacial hydration dynamics can sensitively and site specifically probe macromolecular interactions.

  3. Radiation damage to nucleoprotein complexes in macromolecular crystallography

    International Nuclear Information System (INIS)

    Bury, Charles; Garman, Elspeth F.; Ginn, Helen Mary; Ravelli, Raimond B. G.; Carmichael, Ian; Kneale, Geoff; McGeehan, John E.

    2015-01-01

    Quantitative X-ray induced radiation damage studies employing a model protein–DNA complex revealed a striking partition of damage sites. The DNA component was observed to be far more resistant to specific damage compared with the protein. Significant progress has been made in macromolecular crystallography over recent years in both the understanding and mitigation of X-ray induced radiation damage when collecting diffraction data from crystalline proteins. In contrast, despite the large field that is productively engaged in the study of radiation chemistry of nucleic acids, particularly of DNA, there are currently very few X-ray crystallographic studies on radiation damage mechanisms in nucleic acids. Quantitative comparison of damage to protein and DNA crystals separately is challenging, but many of the issues are circumvented by studying pre-formed biological nucleoprotein complexes where direct comparison of each component can be made under the same controlled conditions. Here a model protein–DNA complex C.Esp1396I is employed to investigate specific damage mechanisms for protein and DNA in a biologically relevant complex over a large dose range (2.07–44.63 MGy). In order to allow a quantitative analysis of radiation damage sites from a complex series of macromolecular diffraction data, a computational method has been developed that is generally applicable to the field. Typical specific damage was observed for both the protein on particular amino acids and for the DNA on, for example, the cleavage of base-sugar N 1 —C and sugar-phosphate C—O bonds. Strikingly the DNA component was determined to be far more resistant to specific damage than the protein for the investigated dose range. At low doses the protein was observed to be susceptible to radiation damage while the DNA was far more resistant, damage only being observed at significantly higher doses

  4. Role of special cross-links in structure formation of bacterial DNA polymer

    Science.gov (United States)

    Agarwal, Tejal; Manjunath, G. P.; Habib, Farhat; Lakshmi Vaddavalli, Pavana; Chatterji, Apratim

    2018-01-01

    Using data from contact maps of the DNA-polymer of Escherichia coli (E. Coli) (at kilobase pair resolution) as an input to our model, we introduce cross-links between monomers in a bead-spring model of a ring polymer at very specific points along the chain. Via suitable Monte Carlo simulations, we show that the presence of these cross-links leads to a particular organization of the chain at large (micron) length scales of the DNA. We also investigate the structure of a ring polymer with an equal number of cross-links at random positions along the chain. We find that though the polymer does get organized at the large length scales, the nature of the organization is quite different from the organization observed with cross-links at specific biologically determined positions. We used the contact map of E. Coli bacteria which has around 4.6 million base pairs in a single circular chromosome. In our coarse-grained flexible ring polymer model, we used 4642 monomer beads and observed that around 80 cross-links are enough to induce the large-scale organization of the molecule accounting for statistical fluctuations caused by thermal energy. The length of a DNA chain even of a simple bacterial cell such as E. Coli is much longer than typical proteins, hence we avoided methods used to tackle protein folding problems. We define new suitable quantities to identify the large scale structure of a polymer chain with a few cross-links.

  5. Fluid Physics and Macromolecular Crystal Growth in Microgravity

    Science.gov (United States)

    Helliwell, John R.; Snell, Edward H.; Chayen, Naomi E.; Judge, Russell A.; Boggon, Titus J.; Pusey, M. L.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    The first protein crystallization experiment in microgravity was launched in April, 1981 and used Germany's Technologische Experimente unter Schwerelosigkeit (TEXUS 3) sounding rocket. The protein P-galactosidase (molecular weight 465Kda) was chosen as the sample with a liquid-liquid diffusion growth method. A sliding device brought the protein, buffer and salt solution into contact when microgravity was reached. The sounding rocket gave six minutes of microgravity time with a cine camera and schlieren optics used to monitor the experiment, a single growth cell. In microgravity a strictly laminar diffusion process was observed in contrast to the turbulent convection seen on the ground. Several single crystals, approx 100micron in length, were formed in the flight which were of inferior but of comparable visual quality to those grown on the ground over several days. A second experiment using the same protocol but with solutions cooled to -8C (kept liquid with glycerol antifreeze) again showed laminar diffusion. The science of macromolecular structural crystallography involves crystallization of the macromolecule followed by use of the crystal for X-ray diffraction experiments to determine the three dimensional structure of the macromolecule. Neutron protein crystallography is employed for elucidation of H/D exchange and for improved definition of the bound solvent (D20). The structural information enables an understanding of how the molecule functions with important potential for rational drug design, improved efficiency of industrial enzymes and agricultural chemical development. The removal of turbulent convection and sedimentation in microgravity, and the assumption that higher quality crystals will be produced, has given rise to the growing number of crystallization experiments now flown. Many experiments can be flown in a small volume with simple, largely automated, equipment - an ideal combination for a microgravity experiment. The term "protein crystal growth

  6. Functionalization of Planet-Satellite Nanostructures Revealed by Nanoscopic Localization of Distinct Macromolecular Species

    KAUST Repository

    Rossner, Christian; Roddatis, Vladimir; Lopatin, Sergei; Vana, Philipp

    2016-01-01

    The development of a straightforward method is reported to form hybrid polymer/gold planet-satellite nanostructures (PlSNs) with functional polymer. Polyacrylate type polymer with benzyl chloride in its backbone as a macromolecular tracer

  7. Crosslinkable coatings from phosphorylcholine-based polymers.

    Science.gov (United States)

    Lewis, A L; Cumming, Z L; Goreish, H H; Kirkwood, L C; Tolhurst, L A; Stratford, P W

    2001-01-01

    2-Methacryloyloxyethyl phosphorylcholine (MPC) was synthesised and then used in the preparation of crosslinked polymer membranes with lauryl methacrylate, hydroxypropyl methacrylate and trimethoxysilylpropyl methacrylate (crosslinker) comonomers. Some physical aspects of the membrane properties were evaluated in order to establish the basis for the synthesis of a series of post-crosslinkable polymers. These materials were made by copolymerisation of the constituent monomers via a free radical method, and characterised using NMR, FT-IR, viscometry and elemental analysis. The optimum crosslink density and conditions required for curing coatings of these polymers were investigated using atomic force microscopy (AFM) and showed the inclusion of 5 mol% silyl crosslinking agent to be ideal. A nanoindentation technique was employed to determine if the coating developed elasticity upon crosslinking. The biological properties of the coatings were evaluated using a variety of protein adsorption assays and blood contacting experiments, and an enzyme immunoassay was developed to detect E. coli in order to assess the level of bacterial adhesion to these biomaterials. Polymers of this type were shown to be very useful as coating materials for improving the biocompatibility of, or reducing the levels of adherent bacteria to medical devices.

  8. Grafting functional antioxidants on highly crosslinked polyethylene

    Science.gov (United States)

    Al-Malaika, S.; Riasat, S.; Lewucha, C.

    2016-05-01

    The problem of interference of antioxidants, such as hindered phenols, with peroxide-initiated crosslinking of polyethylene was addressed through the use of functional (reactive) graftable antioxidants (g-AO). Reactive derivatives of hindered phenol and hindered amine antioxidants were synthesised, characterised and used to investigate their grafting reactions in high density polyethylene; both non-crosslinked (PE) and highly peroxide-crosslinked (PEXa). Assessment of the extent of in-situ grafting of the antioxidants, their retention after exhaustive solvent extraction in PE and PEXa, and the stabilising performance of the grafted antioxidants (g-AO) in the polymer were examined and benchmarked against conventionally stabilised crosslinked & non-crosslinked polyethylene. It was shown that the functional antioxidants graft to a high extent in PEXa, and that the level of interference of the g-AOs with the polymer crosslinking process was minimal compared to that of conventional antioxidants which bear the same antioxidant function. The much higher level of retention of the g-AOs in PEXa after exhaustive solvent extraction, compared to that of the corresponding conventional antioxidants, accounts for their superior long-term thermal stabilising performance under severe extractive conditions.

  9. Detecting onset of chain scission and crosslinking of {gamma}-ray irradiated elastomer surfaces using frictional force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, S [Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 TN (India); Sinha, N K [Innovative Design Engineering and Synthesis Section, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 TN (India); Gayathri, N [Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 TN (India); Ponraju, D [Radiological Safety Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 TN (India); Dash, S [Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 TN (India); Tyagi, A K [Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 TN (India); Raj, Baldev [Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 TN (India)

    2007-02-07

    We report here that atomic force microscopy (AFM) in frictional force mode can be used to detect the onset of chain scission and crosslinking in polymeric and macromolecular samples upon irradiation. A systematic investigation to detect chain scission and crosslinking of two elastomers (1) ethylene-propylene-diene monomer rubber and (2) fluorocarbon rubber, upon {gamma}-ray irradiation has been carried out using frictional force microscopy (FFM). From the AFM results we observed that both the elastomers show a systematic smoothening of its surfaces, as the {gamma}-ray dose rate increases. However, the frictional property studied using FFM of the sample surfaces show an initial increase and then a decrease as a function of dose rate. This behaviour of increase in its frictional property has been attributed to the onset of chain scission, and the subsequent decrease in friction has been attributed to the onset of crosslinking of the polymer chains. The evaluated qualitative and semi-quantitative changes observed in the overall frictional property as a function of the {gamma}-ray dose rate for the two elastomers are presented in this paper.

  10. Detecting onset of chain scission and crosslinking of γ-ray irradiated elastomer surfaces using frictional force microscopy

    International Nuclear Information System (INIS)

    Banerjee, S; Sinha, N K; Gayathri, N; Ponraju, D; Dash, S; Tyagi, A K; Raj, Baldev

    2007-01-01

    We report here that atomic force microscopy (AFM) in frictional force mode can be used to detect the onset of chain scission and crosslinking in polymeric and macromolecular samples upon irradiation. A systematic investigation to detect chain scission and crosslinking of two elastomers (1) ethylene-propylene-diene monomer rubber and (2) fluorocarbon rubber, upon γ-ray irradiation has been carried out using frictional force microscopy (FFM). From the AFM results we observed that both the elastomers show a systematic smoothening of its surfaces, as the γ-ray dose rate increases. However, the frictional property studied using FFM of the sample surfaces show an initial increase and then a decrease as a function of dose rate. This behaviour of increase in its frictional property has been attributed to the onset of chain scission, and the subsequent decrease in friction has been attributed to the onset of crosslinking of the polymer chains. The evaluated qualitative and semi-quantitative changes observed in the overall frictional property as a function of the γ-ray dose rate for the two elastomers are presented in this paper

  11. Nitrogen isotopic composition of macromolecular organic matter in interplanetary dust particles

    Science.gov (United States)

    Aléon, Jérôme; Robert, François; Chaussidon, Marc; Marty, Bernard

    2003-10-01

    Nitrogen concentrations and isotopic compositions were measured by ion microprobe scanning imaging in two interplanetary dust particles L2021 K1 and L2036 E22, in which imaging of D/H and C/H ratios has previously evidenced the presence of D-rich macromolecular organic components. High nitrogen concentrations of 10-20 wt% and δ 15N values up to +400‰ are observed in these D-rich macromolecular components. The previous study of D/H and C/H ratios has revealed three different D-rich macromolecular phases. The one previously ascribed to macromolecular organic matter akin the insoluble organic matter (IOM) from carbonaceous chondrites is enriched in nitrogen by one order of magnitude compared to the carbonaceous chondrite IOM, although its isotopic composition is still similar to what is known from Renazzo (δ 15N = +208‰). The correlation observed in macromolecular organic material between the D- and 15N-excesses suggests that the latter originate probably from chemical reactions typical of the cold interstellar medium. These interstellar materials preserved to some extent in IDPs are therefore macromolecular organic components with various aliphaticity and aromaticity. They are heavily N-heterosubstituted as shown by their high nitrogen concentrations >10 wt%. They have high D/H ratios >10 -3 and δ 15N values ≥ +400‰. In L2021 K1 a mixture is observed at the micron scale between interstellar and chondritic-like organic phases. This indicates that some IDPs contain organic materials processed at various heliocentric distances in a turbulent nebula. Comparison with observation in comets suggests that these molecules may be cometary macromolecules. A correlation is observed between the D/H ratios and δ 15N values of macromolecular organic matter from IDPs, meteorites, the Earth and of major nebular reservoirs. This suggests that most macromolecular organic matter in the inner solar system was probably issued from interstellar precursors and further processed

  12. Timely deposition of macromolecular structures is necessary for peer review

    International Nuclear Information System (INIS)

    Joosten, Robbie P.; Soueidan, Hayssam; Wessels, Lodewyk F. A.; Perrakis, Anastassis

    2013-01-01

    Deposition of crystallographic structures should be concurrent with or prior to manuscript submission for peer review, enabling validation and increasing reliability of the PDB. Most of the macromolecular structures in the Protein Data Bank (PDB), which are used daily by thousands of educators and scientists alike, are determined by X-ray crystallography. It was examined whether the crystallographic models and data were deposited to the PDB at the same time as the publications that describe them were submitted for peer review. This condition is necessary to ensure pre-publication validation and the quality of the PDB public archive. It was found that a significant proportion of PDB entries were submitted to the PDB after peer review of the corresponding publication started, and many were only submitted after peer review had ended. It is argued that clear description of journal policies and effective policing is important for pre-publication validation, which is key in ensuring the quality of the PDB and of peer-reviewed literature

  13. Timely deposition of macromolecular structures is necessary for peer review

    Energy Technology Data Exchange (ETDEWEB)

    Joosten, Robbie P. [Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam (Netherlands); Soueidan, Hayssam; Wessels, Lodewyk F. A. [Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX, Amsterdam (Netherlands); Perrakis, Anastassis, E-mail: a.perrakis@nki.nl [Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam (Netherlands)

    2013-12-01

    Deposition of crystallographic structures should be concurrent with or prior to manuscript submission for peer review, enabling validation and increasing reliability of the PDB. Most of the macromolecular structures in the Protein Data Bank (PDB), which are used daily by thousands of educators and scientists alike, are determined by X-ray crystallography. It was examined whether the crystallographic models and data were deposited to the PDB at the same time as the publications that describe them were submitted for peer review. This condition is necessary to ensure pre-publication validation and the quality of the PDB public archive. It was found that a significant proportion of PDB entries were submitted to the PDB after peer review of the corresponding publication started, and many were only submitted after peer review had ended. It is argued that clear description of journal policies and effective policing is important for pre-publication validation, which is key in ensuring the quality of the PDB and of peer-reviewed literature.

  14. JBluIce-EPICS control system for macromolecular crystallography

    International Nuclear Information System (INIS)

    Stepanov, S.; Makarov, O.; Hilgart, M.; Pothineni, S.; Urakhchin, A.; Devarapalli, S.; Yoder, D.; Becker, M.; Ogata, C.; Sanishvili, R.; Nagarajan, V.; Smith, J.L.; Fischetti, R.F.

    2011-01-01

    The trio of macromolecular crystallography beamlines constructed by the General Medicine and Cancer Institutes Collaborative Access Team (GM/CA-CAT) in Sector 23 of the Advanced Photon Source (APS) have been in growing demand owing to their outstanding beam quality and capacity to measure data from crystals of only a few micrometres in size. To take full advantage of the state-of-the-art mechanical and optical design of these beamlines, a significant effort has been devoted to designing fast, convenient, intuitive and robust beamline controls that could easily accommodate new beamline developments. The GM/CA-CAT beamline controls are based on the power of EPICS for distributed hardware control, the rich Java graphical user interface of Eclipse RCP and the task-oriented philosophy as well as the look and feel of the successful SSRL BluIce graphical user interface for crystallography. These beamline controls feature a minimum number of software layers, the wide use of plug-ins that can be written in any language and unified motion controls that allow on-the-fly scanning and optimization of any beamline component. This paper describes the ways in which BluIce was combined with EPICS and converted into the Java-based JBluIce, discusses the solutions aimed at streamlining and speeding up operations and gives an overview of the tools that are provided by this new open-source control system for facilitating crystallographic experiments, especially in the field of microcrystallography.

  15. On macromolecular refinement at subatomic resolution with interatomic scatterers

    Energy Technology Data Exchange (ETDEWEB)

    Afonine, Pavel V., E-mail: pafonine@lbl.gov; Grosse-Kunstleve, Ralf W.; Adams, Paul D. [Lawrence Berkeley National Laboratory, One Cyclotron Road, BLDG 64R0121, Berkeley, CA 94720 (United States); Lunin, Vladimir Y. [Institute of Mathematical Problems of Biology, Russian Academy of Sciences, Pushchino 142290 (Russian Federation); Urzhumtsev, Alexandre [IGMBC, 1 Rue L. Fries, 67404 Illkirch and IBMC, 15 Rue R. Descartes, 67084 Strasbourg (France); Faculty of Sciences, Nancy University, 54506 Vandoeuvre-lès-Nancy (France); Lawrence Berkeley National Laboratory, One Cyclotron Road, BLDG 64R0121, Berkeley, CA 94720 (United States)

    2007-11-01

    Modelling deformation electron density using interatomic scatters is simpler than multipolar methods, produces comparable results at subatomic resolution and can easily be applied to macromolecules. A study of the accurate electron-density distribution in molecular crystals at subatomic resolution (better than ∼1.0 Å) requires more detailed models than those based on independent spherical atoms. A tool that is conventionally used in small-molecule crystallography is the multipolar model. Even at upper resolution limits of 0.8–1.0 Å, the number of experimental data is insufficient for full multipolar model refinement. As an alternative, a simpler model composed of conventional independent spherical atoms augmented by additional scatterers to model bonding effects has been proposed. Refinement of these mixed models for several benchmark data sets gave results that were comparable in quality with the results of multipolar refinement and superior to those for conventional models. Applications to several data sets of both small molecules and macromolecules are shown. These refinements were performed using the general-purpose macromolecular refinement module phenix.refine of the PHENIX package.

  16. Polycapillary x-ray optics for macromolecular crystallography

    International Nuclear Information System (INIS)

    Owens, S.M.; Gibson, W.M.; Carter, D.C.; Sisk, R.C.; Ho, J.X.

    1996-01-01

    Polycapillary x-ray optics have found potential application in many different fields, including antiscatter and magnification in mammography, radiography, x-ray fluorescence, x-ray lithography, and x-ray diffraction techniques. In x-ray diffraction, an optic is used to collect divergent x-rays from a point source and redirect them into a quasi-parallel, or slightly focused beam. Monolithic polycapillary optics have been developed recently for macromolecular crystallography and have already shown considerable gains in diffracted beam intensity over pinhole collimation. Development is being pursued through a series of simulations and prototype optics. Many improvements have been made over the stage 1 prototype reported previously, which include better control over the manufacturing process, reducing the diameter of the output beam, and addition of a slight focusing at the output of the optic to further increase x-ray flux at the sample. The authors report the characteristics and performance of the stage 1 and stage 2 optics

  17. A beamline for macromolecular crystallography at the Advanced Light Source

    International Nuclear Information System (INIS)

    Padmore, H.A.; Earnest, T.; Kim, S.H.; Thompson, A.C.; Robinson, A.L.

    1994-08-01

    A beamline for macromolecular crystallography has been designed for the ALS. The source will be a 37-pole wiggler with a, 2-T on-axis peak field. The wiggler will illuminate three beamlines, each accepting 3 mrad of horizontal aperture. The central beamline will primarily be used for multiple-wavelength anomalous dispersion measurements in the wavelength range from 4 to 0.9 angstrom. The beamline optics will comprise a double-crystal monochromator with a collimating pre-mirror and a double-focusing mirror after the monochromator. The two side stations will be used for fixed-wavelength experiments within the wavelength range from 1.5 to 0.95 angstrom. The optics will consist of a conventional vertically focusing cylindrical mirror followed by an asymmetrically cut curved-crystal monochromator. This paper presents details of the optimization of the wiggler source for crystallography, gives a description of the beamline configuration, and discusses the reasons for the choices made

  18. Macromolecular crystallization in microgravity generated by a superconducting magnet.

    Science.gov (United States)

    Wakayama, N I; Yin, D C; Harata, K; Kiyoshi, T; Fujiwara, M; Tanimoto, Y

    2006-09-01

    About 30% of the protein crystals grown in space yield better X-ray diffraction data than the best crystals grown on the earth. The microgravity environments provided by the application of an upward magnetic force constitute excellent candidates for simulating the microgravity conditions in space. Here, we describe a method to control effective gravity and formation of protein crystals in various levels of effective gravity. Since 2002, the stable and long-time durable microgravity generated by a convenient type of superconducting magnet has been available for protein crystal growth. For the first time, protein crystals, orthorhombic lysozyme, were grown at microgravity on the earth, and it was proved that this microgravity improved the crystal quality effectively and reproducibly. The present method always accompanies a strong magnetic field, and the magnetic field itself seems to improve crystal quality. Microgravity is not always effective for improving crystal quality. When we applied this microgravity to the formation of cubic porcine insulin and tetragonal lysozyme crystals, we observed no dependence of effective gravity on crystal quality. Thus, this kind of test will be useful for selecting promising proteins prior to the space experiments. Finally, the microgravity generated by the magnet is compared with that in space, considering the cost, the quality of microgravity, experimental convenience, etc., and the future use of this microgravity for macromolecular crystal growth is discussed.

  19. Macromolecular crystallography with a large format CMOS detector

    Energy Technology Data Exchange (ETDEWEB)

    Nix, Jay C., E-mail: jcnix@lbl.gov [Molecular Biology Consortium 12003 S. Pulaski Rd. #166 Alsip, IL 60803 U.S.A (United States)

    2016-07-27

    Recent advances in CMOS technology have allowed the production of large surface area detectors suitable for macromolecular crystallography experiments [1]. The Molecular Biology Consortium (MBC) Beamline 4.2.2 at the Advanced Light Source in Berkeley, CA, has installed a 2952 x 2820 mm RDI CMOS-8M detector with funds from NIH grant S10OD012073. The detector has a 20nsec dead pixel time and performs well with shutterless data collection strategies. The sensor obtains sharp point response and minimal optical distortion by use of a thin fiber-optic plate between the phosphor and sensor module. Shutterless data collections produce high-quality redundant datasets that can be obtained in minutes. The fine-sliced data are suitable for processing in standard crystallographic software packages (XDS, HKL2000, D*TREK, MOSFLM). Faster collection times relative to the previous CCD detector have resulted in a record number of datasets collected in a calendar year and de novo phasing experiments have resulted in publications in both Science and Nature [2,3]. The faster collections are due to a combination of the decreased overhead requirements of shutterless collections combined with exposure times that have decreased by over a factor of 2 for images with comparable signal to noise of the NOIR-1 detector. The overall increased productivity has allowed the development of new beamline capabilities and data collection strategies.

  20. Macromolecular refinement by model morphing using non-atomic parameterizations.

    Science.gov (United States)

    Cowtan, Kevin; Agirre, Jon

    2018-02-01

    Refinement is a critical step in the determination of a model which explains the crystallographic observations and thus best accounts for the missing phase components. The scattering density is usually described in terms of atomic parameters; however, in macromolecular crystallography the resolution of the data is generally insufficient to determine the values of these parameters for individual atoms. Stereochemical and geometric restraints are used to provide additional information, but produce interrelationships between parameters which slow convergence, resulting in longer refinement times. An alternative approach is proposed in which parameters are not attached to atoms, but to regions of the electron-density map. These parameters can move the density or change the local temperature factor to better explain the structure factors. Varying the size of the region which determines the parameters at a particular position in the map allows the method to be applied at different resolutions without the use of restraints. Potential applications include initial refinement of molecular-replacement models with domain motions, and potentially the use of electron density from other sources such as electron cryo-microscopy (cryo-EM) as the refinement model.

  1. Hypoxic tumor environments exhibit disrupted collagen I fibers and low macromolecular transport.

    Directory of Open Access Journals (Sweden)

    Samata M Kakkad

    Full Text Available Hypoxic tumor microenvironments result in an aggressive phenotype and resistance to therapy that lead to tumor progression, recurrence, and metastasis. While poor vascularization and the resultant inadequate drug delivery are known to contribute to drug resistance, the effect of hypoxia on molecular transport through the interstitium, and the role of the extracellular matrix (ECM in mediating this transport are unexplored. The dense mesh of fibers present in the ECM can especially influence the movement of macromolecules. Collagen 1 (Col1 fibers form a key component of the ECM in breast cancers. Here we characterized the influence of hypoxia on macromolecular transport in tumors, and the role of Col1 fibers in mediating this transport using an MDA-MB-231 breast cancer xenograft model engineered to express red fluorescent protein under hypoxia. Magnetic resonance imaging of macromolecular transport was combined with second harmonic generation microscopy of Col1 fibers. Hypoxic tumor regions displayed significantly decreased Col1 fiber density and volume, as well as significantly lower macromolecular draining and pooling rates, than normoxic regions. Regions adjacent to severely hypoxic areas revealed higher deposition of Col1 fibers and increased macromolecular transport. These data suggest that Col1 fibers may facilitate macromolecular transport in tumors, and their reduction in hypoxic regions may reduce this transport. Decreased macromolecular transport in hypoxic regions may also contribute to poor drug delivery and tumor recurrence in hypoxic regions. High Col1 fiber density observed around hypoxic regions may facilitate the escape of aggressive cancer cells from hypoxic regions.

  2. Macromolecular query language (MMQL): prototype data model and implementation.

    Science.gov (United States)

    Shindyalov, I N; Chang, W; Pu, C; Bourne, P E

    1994-11-01

    Macromolecular query language (MMQL) is an extensible interpretive language in which to pose questions concerning the experimental or derived features of the 3-D structure of biological macromolecules. MMQL portends to be intuitive with a simple syntax, so that from a user's perspective complex queries are easily written. A number of basic queries and a more complex query--determination of structures containing a five-strand Greek key motif--are presented to illustrate the strengths and weaknesses of the language. The predominant features of MMQL are a filter and pattern grammar which are combined to express a wide range of interesting biological queries. Filters permit the selection of object attributes, for example, compound name and resolution, whereas the patterns currently implemented query primary sequence, close contacts, hydrogen bonding, secondary structure, conformation and amino acid properties (volume, polarity, isoelectric point, hydrophobicity and different forms of exposure). MMQL queries are processed by MMQLlib; a C++ class library, to which new query methods and pattern types are easily added. The prototype implementation described uses PDBlib, another C(++)-based class library from representing the features of biological macromolecules at the level of detail parsable from a PDB file. Since PDBlib can represent data stored in relational and object-oriented databases, as well as PDB files, once these data are loaded they too can be queried by MMQL. Performance metrics are given for queries of PDB files for which all derived data are calculated at run time and compared to a preliminary version of OOPDB, a prototype object-oriented database with a schema based on a persistent version of PDBlib which offers more efficient data access and the potential to maintain derived information. MMQLlib, PDBlib and associated software are available via anonymous ftp from cuhhca.hhmi.columbia.edu.

  3. Macromolecular weight specificity in covalent binding of bromobenzene

    International Nuclear Information System (INIS)

    Sun, J.D.; Dent, J.G.

    1984-01-01

    Bromobenzene is a hepatotoxicant that causes centrilobular necrosis. Pretreatment of animals with 3-methylcholanthrene decreases and phenobarbital pretreatment enhances the hepatotoxic action of this compound. We have investigated the macromolecular weight specificity of the covalent interactions of bromobenzene with liver macromolecules following incubation of [ 14 C]bromobenzene in isolated hepatocytes. Hepatocytes were prepared from Fischer-344 rats treated for 3 days with 3-methylcholanthrene, phenobarbital, or normal saline. After a 1-hr incubation, total covalent binding, as measured by sodium dodecyl sulfate-equilibrium dialysis, was twofold less in hepatocytes from 3-methylcholanthrene-treated rats and sixfold greater in hepatocytes from phenobarbital-treated rats, as compared to hepatocytes from control animals. Analysis of the arylated macromolecules by electrophoresis on 15% sodium dodecyl sulfate-polyacrylamide disc gels indicated that in the first 1 to 3 min of incubation substantial amounts of covalently bound radiolabel were associated with macromolecules of between 20,000 and 40,000. The amount of radioactivity associated with these macromolecules rapidly diminished in hepatocytes from control and 3-methylcholanthrene-treated animals. In hepatocytes from phenobarbital-treated animals, the amount of radioactivity associated with macromolecules, 20,000, increased throughout the incubation. The amount of radiolabel associated with macromolecules, 20,000, increased in all incubations. When nontoxic doses of phenylmethylsulfonyl fluoride, a specific inhibitor of serine proteases, were added to control hepatocytes incubated with [ 14 C]-bromobenzene, the decrease in radioactivity associated with larger (greater than 20,000) macromolecules was inhibited and a corresponding lack of increase in radioactivity associated with smaller macromolecules was observed

  4. Crosslinked polytriazole membranes for organophilic filtration

    KAUST Repository

    Chisca, Stefan

    2016-12-30

    We report the preparation of crosslinked membranes for organophilic filtration, by reacting a new polytriazole with free OH groups, using non-toxic poly (ethylene glycol) diglycidyl ether (PEGDE). The OH-functionalized polymer was obtained by converting the oxadiazole to triazole rings with high yield (98%). The maximum degree of crosslinking is achieved after 6 h of reaction. The crosslinked polytriazole membranes are stable in a wide range of organic solvents and show high creep recovery, indicating the robustness of crosslinked membranes. The influence of different casting solutions and different crosslinking time on the membrane morphology and membrane performance was investigated. The membranes performance was studied in dimethylformamide (DMF) and (tetrahydrofuran) THF. We achieved a permeance for THF of 49 L m−2 h−1 bar−1 for membranes with molecular weight cut off (MWCO) of 7 kg mol−1 and a permeance for THF of 17.5 L m−2 h−1 bar−1 for membranes with MWCO of 3 kg mol−1. Our data indicate that by using the new polytriazole is possible to adjust the pore dimensions of the membranes to have a MWCO, which covers ultra- and nanofiltration range.

  5. Radiation crosslinking of highly plasticized PVC

    Science.gov (United States)

    Mendizabal, E.; Cruz, L.; Jasso, C. F.; Burillo, G.; Dakin, V. I.

    1996-02-01

    To improve the physical properties of highly plasticized PVC, the polymer was crosslinked by gamma irradiation using a dose rate of 91 kGy/h. The effect of plasticizer type was studied by using three different plasticizers, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB), di(2-ethyl hexyl) phthalate (DOP), and di(2-ethylhexyl terephthalate) (DOTP), and varying irradiation doses. Gel content was determined by soxhlet extraction, tensile measurements were made on a universal testing machine and the mechano-dynamic measurements were made in a dynamic rheometer. It was found that a considerable bonding of plasticizer molecules to macromolelcules takes place along with crosslinking, so that the use of the solvent extraction method for measuring the degree of crosslinking can give erroneous information. Radiation-chemical crosslinking yield ( Gc) and molecular weight of interjunctions chains ( Mc), were calculated for different systems studied. Addition of ethylene glycol dimethacrylate (EGDM) as a crosslinking coagent and dioctyl tin oxide (DOTO) as a stabilizer was also studied. Plasticizers extraction resistance was increased by irradiation treatment.

  6. Radiation crosslinking of highly plasticized PVC

    International Nuclear Information System (INIS)

    Mendizabal, E.; Cruz, L.; Jasso, C.F.; Burillo, G.; Dakin, V.I.

    1996-01-01

    To improve the physical properties of highly plasticized PVC, the polymer was crosslinked by gamma irradiation using a dose rate of 91 kGy/h. The effect of plasticizer type was studied by using three different plasticizers, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB), di(2-ethyl hexyl) phthalate (DOP), and di(2-ethylhexyl terephthalate) (DOTP), and varying irradiation doses. Gel content was determined by soxhlet extraction, tensile measurements were made on a universal testing machine and the mechano-dynamic measurements were made in a dynamic rheometer. It was found that a considerable bonding of plasticizer molecules to macromolecules takes place along with crosslinking, so that the use of the solvent extraction method for measuring the degree of crosslinking can give erroneous information. Radiation-chemical crosslinking yield (G c ) and molecular weight of interjunctions chains (M c ), were calculated for different systems studied. Addition of ethylene glycol dimethyacrylate (EGDM) as a crosslinking coagent and dioctyl tin oxide (DOTO) as a stabilizer was also studied. Plasticizers extraction resistance was increased by irradiation treatment. (author)

  7. Crosslinked polytriazole membranes for organophilic filtration

    KAUST Repository

    Chisca, Stefan; Falca, Gheorghe; Musteata, Valentina-Elena; Boi, Cristiana; Nunes, Suzana Pereira

    2016-01-01

    We report the preparation of crosslinked membranes for organophilic filtration, by reacting a new polytriazole with free OH groups, using non-toxic poly (ethylene glycol) diglycidyl ether (PEGDE). The OH-functionalized polymer was obtained by converting the oxadiazole to triazole rings with high yield (98%). The maximum degree of crosslinking is achieved after 6 h of reaction. The crosslinked polytriazole membranes are stable in a wide range of organic solvents and show high creep recovery, indicating the robustness of crosslinked membranes. The influence of different casting solutions and different crosslinking time on the membrane morphology and membrane performance was investigated. The membranes performance was studied in dimethylformamide (DMF) and (tetrahydrofuran) THF. We achieved a permeance for THF of 49 L m−2 h−1 bar−1 for membranes with molecular weight cut off (MWCO) of 7 kg mol−1 and a permeance for THF of 17.5 L m−2 h−1 bar−1 for membranes with MWCO of 3 kg mol−1. Our data indicate that by using the new polytriazole is possible to adjust the pore dimensions of the membranes to have a MWCO, which covers ultra- and nanofiltration range.

  8. Collagen crosslinks in chondromalacia of the patella.

    Science.gov (United States)

    Väätäinen, U; Kiviranta, I; Jaroma, H; Arokosi, J; Tammi, M; Kovanen, V

    1998-02-01

    The aim of the study was to determine collagen concentration and collagen crosslinks in cartilage samples from chondromalacia of the patella. To study the extracellular matrix alterations associated to chondromalacia, we determined the concentration of collagen (hydroxyproline) and its hydroxylysylpyridinoline and lysylpyridinoline crosslinks from chondromalacia foci of the patellae in 12 patients and 7 controls from apparently normal cadavers. The structure of the collagen network in 8 samples of grades II-IV chondromalacia was examined under polarized light microscopy. The full-thickness cartilage samples taken with a surgical knife from chondromalacia lesions did not show changes in collagen, hydroxylysylpyridinoline and lysylpyridinoline concentration as compared with the controls. Polarized light microscopy showed decreased birefringence in the superficial cartilage of chondromalacia lesions, indicating disorganization or disappearance of collagen fibers in this zone. It is concluded that the collagen network shows gradual disorganization with the severity of chondromalacia lesion of the patella without changes in the concentration or crosslinks of collagen.

  9. Synthesis and Characterization of Ionically Crosslinked Elastomers

    Science.gov (United States)

    2016-01-01

    was prepared by quaternization of vinyl benzyl chloride, while a  common dicarboxylic RAFT agent was neutralized with  potassium . The ideal structure...polymerization  where each mole of RAFT agent will  produce one mole of crosslink  junctions.  Initial polymerizations of n‐butyl  acrylate  (BA) were...butyl  acrylate  was polymerized  with the RAFT crosslinking agent in  methanol to low conversion to  introduce BA units, but limit the crosslinking

  10. Crosslinked polyethylene foams, via eb radiation

    International Nuclear Information System (INIS)

    Cardoso, E.C.L.; Lugao, A. B.; Andrade e Silva, L. G.

    1998-01-01

    Polyethylene foams, produced by radio-induced crosslinking, show a smooth and homogeneous surface, when compared to chemical crosslinking method using peroxide as crosslinking agent. This process fosters excellent adhesive and printability properties. Besides that, closed cells, intrinsic to these foams, imparts optimum mechanical, shocks and insulation resistance, indicating these foams to some markets segments as: automotive and transport; buoyancy, flotation and marine; building and insulation; packaging; domestic sports and leisure goods. We were in search of an ideal foam, by adding 5 to 15% of blowing agent in LDPE. A series of preliminary trials defined 203 degree sign C as the right blowing agent decomposition temperature. At a 22.7 kGys/dose ratio, the lowest dose for providing an efficient foam was 30 kGy, for a formulation comprising 10% of azodicarbonamide in LDPE, within a 10 minutes foaming time

  11. A simple quantitative model of macromolecular crowding effects on protein folding: Application to the murine prion protein(121-231)

    Science.gov (United States)

    Bergasa-Caceres, Fernando; Rabitz, Herschel A.

    2013-06-01

    A model of protein folding kinetics is applied to study the effects of macromolecular crowding on protein folding rate and stability. Macromolecular crowding is found to promote a decrease of the entropic cost of folding of proteins that produces an increase of both the stability and the folding rate. The acceleration of the folding rate due to macromolecular crowding is shown to be a topology-dependent effect. The model is applied to the folding dynamics of the murine prion protein (121-231). The differential effect of macromolecular crowding as a function of protein topology suffices to make non-native configurations relatively more accessible.

  12. Shell-crosslinked knedel-like nanoparticles induce lower immunotoxicity than their non-crosslinked analogs.

    Science.gov (United States)

    Elsabahy, Mahmoud; Samarajeewa, Sandani; Raymond, Jeffery E; Clark, Corrie; Wooley, Karen L

    2013-10-21

    The development of stable nanoparticles that can withstand the changing conditions experienced in a biological setting and also be of low toxicity and immunogenicity is of particular importance to address the problems associated with currently utilized nanotechnology-based therapeutics and diagnostics. The use of crosslinked nanoparticles continues to receive special impetus, due to their robust structure and high kinetic stability, and they have recently been shown to induce lower cytotoxicity than their non-crosslinked micellar counterparts. In the current study, poly(acrylamidoethylamine)- block -poly(DL-lactide) (PAEA 90 - b -PDLLA 40 ) copolymers were synthesized, self-assembled in water to yield nanoscopic polymeric micelles, and the effects of decorating the micellar surface with poly(ethylene glycol) ( i.e. PEGylation) and crosslinking the PAEA layer to varying extents on the physicochemical characteristics, cytotoxicity and immunotoxicity of the nanoparticles were studied. Herein, we report for the first time that crosslinking can efficiently reduce the immunotoxicity of polymeric nanomaterials. In addition, increasing the degree of crosslinking further reduced the accessibility of biomolecules to the core of the nanoparticles and decreased their cytotoxicity and immunotoxicity. It is also highlighted that crosslinking can be more efficient than PEGylation in reducing the immunotoxicity of nanomaterials. Shell-crosslinking of block copolymer micelles, therefore, is expected to advance their clinical development beyond the earlier known effects, and to broaden the implications in the field of nanomedicine.

  13. Interpretation of ensembles created by multiple iterative rebuilding of macromolecular models

    International Nuclear Information System (INIS)

    Terwilliger, Thomas C.; Grosse-Kunstleve, Ralf W.; Afonine, Pavel V.; Adams, Paul D.; Moriarty, Nigel W.; Zwart, Peter; Read, Randy J.; Turk, Dusan; Hung, Li-Wei

    2007-01-01

    Heterogeneity in ensembles generated by independent model rebuilding principally reflects the limitations of the data and of the model-building process rather than the diversity of structures in the crystal. Automation of iterative model building, density modification and refinement in macromolecular crystallography has made it feasible to carry out this entire process multiple times. By using different random seeds in the process, a number of different models compatible with experimental data can be created. Sets of models were generated in this way using real data for ten protein structures from the Protein Data Bank and using synthetic data generated at various resolutions. Most of the heterogeneity among models produced in this way is in the side chains and loops on the protein surface. Possible interpretations of the variation among models created by repetitive rebuilding were investigated. Synthetic data were created in which a crystal structure was modelled as the average of a set of ‘perfect’ structures and the range of models obtained by rebuilding a single starting model was examined. The standard deviations of coordinates in models obtained by repetitive rebuilding at high resolution are small, while those obtained for the same synthetic crystal structure at low resolution are large, so that the diversity within a group of models cannot generally be a quantitative reflection of the actual structures in a crystal. Instead, the group of structures obtained by repetitive rebuilding reflects the precision of the models, and the standard deviation of coordinates of these structures is a lower bound estimate of the uncertainty in coordinates of the individual models

  14. Cross-linking for microbial keratitis

    Directory of Open Access Journals (Sweden)

    Jayesh Vazirani

    2013-01-01

    Full Text Available The success of collagen cross-linking as a clinical modality to modify the clinical course in keratoconus seems to have fueled the search for alternative applications for this treatment. Current clinical data on its efficacy is limited and laboratory data seems to indicate that it performs poorly against resistant strains of bacteria and against slow growing organisms. However, the biological plausibility of crosslinking and the lack of effective strategies in managing infections with these organisms continue to focus attention on this potential treatment. Well-conducted experimental and clinical studies with controls are required to answer the questions of its efficacy in future.

  15. Heating tubes of cross-linked polyethylene

    International Nuclear Information System (INIS)

    Knoeppler, H.; Hoffmann, M.

    1981-01-01

    Oxygen permeability of plastic tubes for floor heating systems was measured as a function of the reduced oxygen content of water in plastic tubes at a flow rate of 0.5 m/s and a temperature of 30 0 C and as a function of oxygen uptake of low-oxygen water in floor heating tubes. Pipes of VEP, periodically cross-linked polyethylene (Engels process), polypropylene copolymeride, and polybutene were compared. The permeability of periodically cross-linked polyethylene is twice as high as that of VEP. Measurements, results, and consequences for floor heating systems are discussed. (KH) [de

  16. Towards a compact and precise sample holder for macromolecular crystallography.

    Science.gov (United States)

    Papp, Gergely; Rossi, Christopher; Janocha, Robert; Sorez, Clement; Lopez-Marrero, Marcos; Astruc, Anthony; McCarthy, Andrew; Belrhali, Hassan; Bowler, Matthew W; Cipriani, Florent

    2017-10-01

    Most of the sample holders currently used in macromolecular crystallography offer limited storage density and poor initial crystal-positioning precision upon mounting on a goniometer. This has now become a limiting factor at high-throughput beamlines, where data collection can be performed in a matter of seconds. Furthermore, this lack of precision limits the potential benefits emerging from automated harvesting systems that could provide crystal-position information which would further enhance alignment at beamlines. This situation provided the motivation for the development of a compact and precise sample holder with corresponding pucks, handling tools and robotic transfer protocols. The development process included four main phases: design, prototype manufacture, testing with a robotic sample changer and validation under real conditions on a beamline. Two sample-holder designs are proposed: NewPin and miniSPINE. They share the same robot gripper and allow the storage of 36 sample holders in uni-puck footprint-style pucks, which represents 252 samples in a dry-shipping dewar commonly used in the field. The pucks are identified with human- and machine-readable codes, as well as with radio-frequency identification (RFID) tags. NewPin offers a crystal-repositioning precision of up to 10 µm but requires a specific goniometer socket. The storage density could reach 64 samples using a special puck designed for fully robotic handling. miniSPINE is less precise but uses a goniometer mount compatible with the current SPINE standard. miniSPINE is proposed for the first implementation of the new standard, since it is easier to integrate at beamlines. An upgraded version of the SPINE sample holder with a corresponding puck named SPINEplus is also proposed in order to offer a homogenous and interoperable system. The project involved several European synchrotrons and industrial companies in the fields of consumables and sample-changer robotics. Manual handling of mini

  17. Effects of macromolecular crowding on protein conformational changes.

    Directory of Open Access Journals (Sweden)

    Hao Dong

    2010-07-01

    Full Text Available Many protein functions can be directly linked to conformational changes. Inside cells, the equilibria and transition rates between different conformations may be affected by macromolecular crowding. We have recently developed a new approach for modeling crowding effects, which enables an atomistic representation of "test" proteins. Here this approach is applied to study how crowding affects the equilibria and transition rates between open and closed conformations of seven proteins: yeast protein disulfide isomerase (yPDI, adenylate kinase (AdK, orotidine phosphate decarboxylase (ODCase, Trp repressor (TrpR, hemoglobin, DNA beta-glucosyltransferase, and Ap(4A hydrolase. For each protein, molecular dynamics simulations of the open and closed states are separately run. Representative open and closed conformations are then used to calculate the crowding-induced changes in chemical potential for the two states. The difference in chemical-potential change between the two states finally predicts the effects of crowding on the population ratio of the two states. Crowding is found to reduce the open population to various extents. In the presence of crowders with a 15 A radius and occupying 35% of volume, the open-to-closed population ratios of yPDI, AdK, ODCase and TrpR are reduced by 79%, 78%, 62% and 55%, respectively. The reductions for the remaining three proteins are 20-44%. As expected, the four proteins experiencing the stronger crowding effects are those with larger conformational changes between open and closed states (e.g., as measured by the change in radius of gyration. Larger proteins also tend to experience stronger crowding effects than smaller ones [e.g., comparing yPDI (480 residues and TrpR (98 residues]. The potentials of mean force along the open-closed reaction coordinate of apo and ligand-bound ODCase are altered by crowding, suggesting that transition rates are also affected. These quantitative results and qualitative trends will

  18. Densely crosslinked polycarbosiloxanes .2. Thermal and mechanical properties

    NARCIS (Netherlands)

    Flipsen, T.A C; Derks, R.; van der Vegt, H.A.; Stenekes, R.; Pennings, A.J; Hadziioannou, G

    1997-01-01

    The thermal and mechanical properties of two densely crosslinked polycarbosiloxane systems were investigated in relation to the molecular structure. The networks were prepared from functional branched prepolymers and crosslinked via a hydrosilylation curing reaction. The prepolymers having only

  19. Thermal enhancement of x-ray induced DNA crosslinking

    International Nuclear Information System (INIS)

    Bowden, G.T.; Kasunic, M.; Cress, A.E.

    1982-01-01

    Ionizing radiation appears to crosslink nuclear DNA with chromosomal proteins. Important cellular processes such as transcription and DNA replication are likely to be compromised as a result of the DNA crosslinking. Heat treatment (43/sup o/C) of mouse leukemia cells (L1210) before X irradiation (50 Gy) was found to cause a doubling of the radiation-induced DNA crosslinking as measured by alkaline elution technique. By using proteinase K, a very active protease, to eliminate DNA-protein crosslinking in the alkaline elution assay, it was shown that the thermally enhanced DNA crosslinking was attributed to an increase in DNA-protein crosslinking. However, utilizing a protein radiolabel technique under conditions of increased DNA-protein crosslinking, the amount of protein left on the filter in the elution assay was not increased. These data suggest that qualitative rather than large quantitative differences in the crosslinked chromosomal proteins exist between irradiated cells and cells treated with heat prior to irradiation

  20. New Paradigm for Macromolecular Crystallography Experiments at SSRL: Automated Crystal Screening And Remote Data Collection

    International Nuclear Information System (INIS)

    Soltis, S.M.; Cohen, A.E.; Deacon, A.; Eriksson, T.; Gonzalez, A.; McPhillips, S.; Chui, H.; Dunten, P.; Hollenbeck, M.; Mathews, I.; Miller, M.; Moorhead, P.; Phizackerley, R.P.; Smith, C.; Song, J.; Bedem, H. van dem; Ellis, P.; Kuhn, P.; McPhillips, T.; Sauter, N.; Sharp, K.

    2009-01-01

    Complete automation of the macromolecular crystallography experiment has been achieved at Stanford Synchrotron Radiation Lightsource (SSRL) through the combination of robust mechanized experimental hardware and a flexible control system with an intuitive user interface. These highly reliable systems have enabled crystallography experiments to be carried out from the researchers' home institutions and other remote locations while retaining complete control over even the most challenging systems. A breakthrough component of the system, the Stanford Auto-Mounter (SAM), has enabled the efficient mounting of cryocooled samples without human intervention. Taking advantage of this automation, researchers have successfully screened more than 200 000 samples to select the crystals with the best diffraction quality for data collection as well as to determine optimal crystallization and cryocooling conditions. These systems, which have been deployed on all SSRL macromolecular crystallography beamlines and several beamlines worldwide, are used by more than 80 research groups in remote locations, establishing a new paradigm for macromolecular crystallography experimentation.

  1. Enzymatically crosslinked silk-hyaluronic acid hydrogels.

    Science.gov (United States)

    Raia, Nicole R; Partlow, Benjamin P; McGill, Meghan; Kimmerling, Erica Palma; Ghezzi, Chiara E; Kaplan, David L

    2017-07-01

    In this study, silk fibroin and hyaluronic acid (HA) were enzymatically crosslinked to form biocompatible composite hydrogels with tunable mechanical properties similar to that of native tissues. The formation of di-tyrosine crosslinks between silk fibroin proteins via horseradish peroxidase has resulted in a highly elastic hydrogel but exhibits time-dependent stiffening related to silk self-assembly and crystallization. Utilizing the same method of crosslinking, tyramine-substituted HA forms hydrophilic and bioactive hydrogels that tend to have limited mechanics and degrade rapidly. To address the limitations of these singular component scaffolds, HA was covalently crosslinked with silk, forming a composite hydrogel that exhibited both mechanical integrity and hydrophilicity. The composite hydrogels were assessed using unconfined compression and infrared spectroscopy to reveal of the physical properties over time in relation to polymer concentration. In addition, the hydrogels were characterized by enzymatic degradation and for cytotoxicity. Results showed that increasing HA concentration, decreased gelation time, increased degradation rate, and reduced changes that were observed over time in mechanics, water retention, and crystallization. These hydrogel composites provide a biologically relevant system with controllable temporal stiffening and elasticity, thus offering enhanced tunable scaffolds for short or long term applications in tissue engineering. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Cross-linked structure of network evolution

    Energy Technology Data Exchange (ETDEWEB)

    Bassett, Danielle S., E-mail: dsb@seas.upenn.edu [Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States); Department of Physics, University of California, Santa Barbara, California 93106 (United States); Sage Center for the Study of the Mind, University of California, Santa Barbara, California 93106 (United States); Wymbs, Nicholas F.; Grafton, Scott T. [Department of Psychology and UCSB Brain Imaging Center, University of California, Santa Barbara, California 93106 (United States); Porter, Mason A. [Oxford Centre for Industrial and Applied Mathematics, Mathematical Institute, University of Oxford, Oxford OX2 6GG (United Kingdom); CABDyN Complexity Centre, University of Oxford, Oxford, OX1 1HP (United Kingdom); Mucha, Peter J. [Carolina Center for Interdisciplinary Applied Mathematics, Department of Mathematics, University of North Carolina, Chapel Hill, North Carolina 27599 (United States); Department of Applied Physical Sciences, University of North Carolina, Chapel Hill, North Carolina 27599 (United States)

    2014-03-15

    We study the temporal co-variation of network co-evolution via the cross-link structure of networks, for which we take advantage of the formalism of hypergraphs to map cross-link structures back to network nodes. We investigate two sets of temporal network data in detail. In a network of coupled nonlinear oscillators, hyperedges that consist of network edges with temporally co-varying weights uncover the driving co-evolution patterns of edge weight dynamics both within and between oscillator communities. In the human brain, networks that represent temporal changes in brain activity during learning exhibit early co-evolution that then settles down with practice. Subsequent decreases in hyperedge size are consistent with emergence of an autonomous subgraph whose dynamics no longer depends on other parts of the network. Our results on real and synthetic networks give a poignant demonstration of the ability of cross-link structure to uncover unexpected co-evolution attributes in both real and synthetic dynamical systems. This, in turn, illustrates the utility of analyzing cross-links for investigating the structure of temporal networks.

  3. Cross-linked structure of network evolution

    International Nuclear Information System (INIS)

    Bassett, Danielle S.; Wymbs, Nicholas F.; Grafton, Scott T.; Porter, Mason A.; Mucha, Peter J.

    2014-01-01

    We study the temporal co-variation of network co-evolution via the cross-link structure of networks, for which we take advantage of the formalism of hypergraphs to map cross-link structures back to network nodes. We investigate two sets of temporal network data in detail. In a network of coupled nonlinear oscillators, hyperedges that consist of network edges with temporally co-varying weights uncover the driving co-evolution patterns of edge weight dynamics both within and between oscillator communities. In the human brain, networks that represent temporal changes in brain activity during learning exhibit early co-evolution that then settles down with practice. Subsequent decreases in hyperedge size are consistent with emergence of an autonomous subgraph whose dynamics no longer depends on other parts of the network. Our results on real and synthetic networks give a poignant demonstration of the ability of cross-link structure to uncover unexpected co-evolution attributes in both real and synthetic dynamical systems. This, in turn, illustrates the utility of analyzing cross-links for investigating the structure of temporal networks

  4. Mesoscopic simulations of crosslinked polymer networks

    NARCIS (Netherlands)

    Megariotis, G.; Vogiatzis, G.G.; Schneider, L.; Müller, M.; Theodorou, D.N.

    2016-01-01

    A new methodology and the corresponding C++ code for mesoscopic simulations of elastomers are presented. The test system, crosslinked ds-1'4-polyisoprene' is simulated with a Brownian Dynamics/kinetic Monte Carlo algorithm as a dense liquid of soft, coarse-grained beads, each representing 5-10 Kuhn

  5. Crosslinking of viral nanoparticles with “clickable” fluorescent crosslinkers at the interface

    Institute of Scientific and Technical Information of China (English)

    KAUR; Gagandeep; BARNHILL; Hannah

    2010-01-01

    Cu (I) catalyzed alkyne-azide cycloaddition (CuAAC) reaction,a typical "click" reaction,is one of the modular synthetic approaches which has been broadly used in various organic syntheses,medicinal chemistry,materials development and bioconjugation applications.We have for the first time synthesized two dialkyne derivatized fluorescent crosslinkers which could be applied to crosslink two biomolecules using CuAAC reaction.Turnip yellow mosaic virus,a plant virus with unique structural and chemical properties,was used as a prototypical scaffold to form a 2D single layer at the interface of two immiscible liquids and crosslinked with these two linkers by the CuAAC reaction.Upon crosslinking,the fluorescence of both linkers diminished,likely due to the distortion of the polymethylene backbone,which therefore could be used to indicate the completion of the reaction.

  6. ESR study on free radicals trapped in crosslinked polytetrafluoroethylene (PTFE)

    International Nuclear Information System (INIS)

    Oshima, Akihiro; Tabata, Yoneho; Seguchi, Tadao

    1997-01-01

    Free radicals in crosslinked PTFE which formed by 60 Co γ-rays irradiation at 77 K and at room temperature were studied by electron spin resonance (ESR) spectroscopy. The crosslinked PTFE specimens with different crosslinking density were prepared by electron beam irradiation in the molten state. The ESR spectra observed in the irradiated crosslinked PTFE are much different from those in non-crosslinked PTFE (virgin); a broad singlet component increases with increasing the crosslinking density, G-value of radicals is much higher in crosslinked PTFE than in non-crosslinked one. Free radicals related to the broad component are trapped in the non-crystalline region of crosslinked PTFE and rather stable at room temperature, whereas radicals trapped in amorphous non-crosslinked PTFE are unstable at room temperature. It is thought that most of free radicals trapped in the crosslinked PTFE are formed in the crosslinked amorphous region. The trapped radicals decays around 383 K (110 o C) due to the molecular motion of α-relaxation. (Author)

  7. [Biophysical principles of collagen cross-linking].

    Science.gov (United States)

    Spörl, E; Raiskup-Wolf, F; Pillunat, L E

    2008-02-01

    The reduced mechanical stability of the cornea in keratoconus or in keratectasia after Lasik may be increased by photooxidative cross-linking of corneal collagen. The biophysical principles are compiled for the safe and effective application of this new treatment method. The setting of the therapy parameters should be elucidated from the absorption behaviour of the cornea. The safety of the method for the endothelium cells and the lens will be discussed. The induced cross-links are shown to be the result of changes in the physico-chemical properties of the cornea. To reach a high absorption of the irradiation energy in the cornea, riboflavin of a concentration of 0.1% and UV light of a wavelength of 370 nm, corresponding to the relative maximum of absorption of riboflavin, were used. An irradiance of 3 mW/cm(2) and an irradiation time of 30 min lead to an increase of the mechanical stiffness. The endothelium cells will be protected due to the high absorption within the cornea, that means the damaging threshold of the endothelium cells will not be reached in a 400 microm thick stroma. As evidence for cross-links we can consider the increase of the biomechanical stiffness, the increased resistance against enzymatic degradation, a higher shrinkage temperature, a lower swelling rate and an increased diameter of collagen fibres. The therapy parameters were tested experimentally and have been proven clinically in the corneal collagen cross-linking. These parameters should be respected to reach a safe cross-linking effect without damage of the adjacent tissues.

  8. Dexamethasone attenuates grain sorghum dust extract-induced increase in macromolecular efflux in vivo.

    Science.gov (United States)

    Akhter, S R; Ikezaki, H; Gao, X P; Rubinstein, I

    1999-05-01

    The purpose of this study was to determine whether dexamethasone attenuates grain sorghum dust extract-induced increase in macromolecular efflux from the in situ hamster cheek pouch and, if so, whether this response is specific. By using intravital microscopy, we found that an aqueous extract of grain sorghum dust elicited significant, concentration-dependent leaky site formation and increase in clearance of FITC-labeled dextran (FITC-dextran; mol mass, 70 kDa) from the in situ hamster cheek pouch (P grain sorghum dust extract- and substance P-induced increases in macromolecular efflux from the in situ hamster cheek pouch in a specific fashion.

  9. An acoustic on-chip goniometer for room temperature macromolecular crystallography.

    Science.gov (United States)

    Burton, C G; Axford, D; Edwards, A M J; Gildea, R J; Morris, R H; Newton, M I; Orville, A M; Prince, M; Topham, P D; Docker, P T

    2017-12-05

    This paper describes the design, development and successful use of an on-chip goniometer for room-temperature macromolecular crystallography via acoustically induced rotations. We present for the first time a low cost, rate-tunable, acoustic actuator for gradual in-fluid sample reorientation about varying axes and its utilisation for protein structure determination on a synchrotron beamline. The device enables the efficient collection of diffraction data via a rotation method from a sample within a surface confined droplet. This method facilitates efficient macromolecular structural data acquisition in fluid environments for dynamical studies.

  10. The Joint Structural Biology Group beam lines at the ESRF: Modern macromolecular crystallography

    CERN Document Server

    Mitchell, E P

    2001-01-01

    Macromolecular crystallography has evolved considerably over the last decade. Data sets in under an hour are now possible on high throughput beam lines leading to electron density and, possibly, initial models calculated on-site. There are five beam lines currently dedicated to macromolecular crystallography: the ID14 complex and BM-14 (soon to be superseded by ID-29). These lines handle over five hundred projects every six months and demand is increasing. Automated sample handling, alignment and data management protocols will be required to work efficiently with this demanding load. Projects developing these themes are underway within the JSBG.

  11. Aging changes of macromolecular synthesis in the mitochondria of mouse hepatocytes as revealed by microscopic radioautography

    Energy Technology Data Exchange (ETDEWEB)

    Nagata, Tetsuji [Shinshu University, Matsumoto (Japan). Dept. of Anatomy and Cell Biology

    2007-07-01

    This mini-review reports aging changes of macromolecular synthesis in the mitochondria of mouse hepatocytes. We have observed the macromolecular synthesis, such as DNA, RNA and proteins, in the mitochondria of various mammalian cells by means of electron microscopic radioautography technique developed in our laboratory. The number of mitochondria per cell, number of labeled mitochondria per cell with 3H-thymidine, 3H-uridine and 3H-leucine, precursors for DNA, RNA and proteins, respectively, were counted and the labeling indices at various ages, from fetal to postnatal early days and several months to 1 and 2 years in senescence, were calculated, which showed variations due to aging. (author)

  12. Cross-linked compared with historical polyethylene in THA: an 8-year clinical study.

    Science.gov (United States)

    Geerdink, Carel H; Grimm, Bernd; Vencken, Wendy; Heyligers, Ide C; Tonino, Alphons J

    2009-04-01

    Wear particle-induced osteolysis is a major cause of aseptic loosening in THA. Increasing wear resistance of polyethylene (PE) occurs by increasing the cross-link density and early reports document low wear rates with such implants. To confirm longer-term reductions in wear we compared cross-linked polyethylene (irradiation in nitrogen, annealing) with historical polyethylene (irradiation in air) in a prospective, randomized clinical study involving 48 patients who underwent THAs with a minimum followup of 7 years (mean, 8 years; range, 7-9 years). The insert material was the only variable. The Harris hip score, radiographic signs of osteolysis, and polyethylene wear were recorded annually. Twenty-three historical and 17 moderately cross-linked polyethylene inserts were analyzed (five patients died, three were lost to followup). At 8 years, the wear rate was lower for cross-linked polyethylene (0.088 +/- 0.03 mm/year) than for the historical polyethylene (0.142 +/- 0.07 mm/year). This reduction (38%) did not diminish with time (33% at 5 years). Acetabular cyst formation was less frequent (39% versus 12%), affected fewer DeLee and Charnley zones (17% versus 4%), and was less severe for the cross-linked polyethylene. The only revision was for an aseptically loose cup in the historical polyethylene group. Moderately cross-linked polyethylene maintained its wear advantage with time and produced less osteolysis, showing no signs of aging at mid-term followup. Level I, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

  13. Radiation cross-linking of fluoropolymers: Pt.2

    International Nuclear Information System (INIS)

    Sun Jiazhen; Zhu Xianglin; Zhang Yuefang

    1987-01-01

    On the basis of the results of IR analysis, ESR, ESCA and chemical anlaysis, the mechanism of radiation crosslinking of fluoropolymer Fs-46 was suggested. The crosslinking point of Fs-46 is not on the side chain-CF 3 -group, as Bowers suggest with their theoretical analysis, it may carried out with recombination of two side chain radicals directly, crosslinking with H type, or recombination of side chain radicals and chain end radicals through branching and then crosslinking. It is crosslinking with T type or Y type. The later one is the probable mechanism

  14. The Fanconi anemia proteins FAA and FAC function in different cellular compartments to protect against cross-linking agent cytotoxicity.

    Science.gov (United States)

    Kruyt, F A; Youssoufian, H

    1998-10-01

    Fanconi anemia (FA) is an autosomal recessive disease characterized by chromosomal instability, bone marrow failure, and a high risk of developing malignancies. Although the disorder is genetically heterogeneous, all FA cells are defined by their sensitivity to the apoptosis-inducing effect of cross-linking agents, such as mitomycin C (MMC). The cloned FA disease genes, FAC and FAA, encode proteins with no homology to each other or to any known protein. We generated a highly specific antibody against FAA and found the protein in both the cytoplasm and nucleus of mammalian cells. By subcellular fractionation, FAA is also associated with intracellular membranes. To identify the subcellular compartment that is relevant for FAA activity, we appended nuclear export and nuclear localization signals to the carboxy terminus of FAA and enriched its localization in either the cytoplasm or the nucleus. Nuclear localization of FAA was both necessary and sufficient to correct MMC sensitivity in FA-A cells. In addition, we found no evidence for an interaction between FAA and FAC either in vivo or in vitro. Together with a previous finding that FAC is active in the cytoplasm but not in the nucleus, our results indicate that FAA and FAC function in separate subcellular compartments. Thus, FAA and FAC, if functionally linked, are more likely to be in a linear pathway rather than form a macromolecular complex to protect against cross-linker cytotoxicity.

  15. Desmosine-Inspired Cross-Linkers for Hyaluronan Hydrogels

    Science.gov (United States)

    Hagel, Valentin; Mateescu, Markus; Southan, Alexander; Wegner, Seraphine V.; Nuss, Isabell; Haraszti, Tamás; Kleinhans, Claudia; Schuh, Christian; Spatz, Joachim P.; Kluger, Petra J.; Bach, Monika; Tussetschläger, Stefan; Tovar, Günter E. M.; Laschat, Sabine; Boehm, Heike

    2013-06-01

    We designed bioinspired cross-linkers based on desmosine, the cross-linker in natural elastin, to prepare hydrogels with thiolated hyaluronic acid. These short, rigid cross-linkers are based on pyridinium salts (as in desmosine) and can connect two polymer backbones. Generally, the obtained semi-synthetic hydrogels are form-stable, can withstand repeated stress, have a large linear-elastic range, and show strain stiffening behavior typical for biopolymer networks. In addition, it is possible to introduce a positive charge to the core of the cross-linker without affecting the gelation efficiency, or consequently the network connectivity. However, the mechanical properties strongly depend on the charge of the cross-linker. The properties of the presented hydrogels can thus be tuned in a range important for engineering of soft tissues by controlling the cross-linking density and the charge of the cross-linker.

  16. Crosslinking of wire and cable insulation using electron accelerators

    International Nuclear Information System (INIS)

    Feng Yongxiang; Ma Zueteh

    1992-01-01

    Radiation crosslinking of wire and cable insulation is a well-established technology that is widely used in industry. The advantages of radiation crosslinking over chemical crosslinking have helped maintain its steady growth. Since successful utilization of electron beam processing relies on the formulation of compounds used in insulation, the radiation crosslinking of various polymers is reviewed. The handling technology for crosslinking wire and cable insulation and the throughput capacity of electron beam processors are also discussed. More than 30% of the industrial electron accelerators in the world are used for the radiation crosslinking of wire and cable insulation. Prospects of increased use of electron accelerators for crosslinking of wire and cable insulation are very good. (orig.)

  17. The Postgraduate Study of Macromolecular Sciences at the University of Zagreb (1971-1980

    Directory of Open Access Journals (Sweden)

    Kunst, B.

    2008-07-01

    Full Text Available The postgraduate study of macromolecular sciences (PSMS was established at the University of Zagreb in 1971 as a university study in the time of expressed interdisciplinary permeation of natural sciences - physics, chemistry and biology, and application of their achievements in technologicaldisciplines. PSMS was established by a group of prominent university professors from the schools of Science, Chemical Technology, Pharmacy and Medicine, as well as from the Institute of Biology. The study comprised basic fields of macromolecular sciences: organic chemistry of synthetic macromolecules, physical chemistry of macromolecules, physics of macromolecules, biological macromolecules and polymer engineering with polymer application and processing, and teaching was performed in 29 lecture courses lead by 30 professors with their collaborators. PSMS ceased to exist with the change of legislation in Croatia in 1980, when the attitude prevailed to render back postgraduate studies to the university schools. During 9 years of existence of PSMS the MSci grade was awarded to 37 macromolecular experts. It was assessed that the PSMS some thirty years ago was an important example of modern postgraduate education as compared with the international postgraduate development. In concordance with the recent introduction of similar interdisciplinary studies in macromolecular sciences elsewhere in the world, the establishment of a modern interdisciplinary study in the field would be of importance for further development of these sciences in Croatia.

  18. MMTF-An efficient file format for the transmission, visualization, and analysis of macromolecular structures.

    Directory of Open Access Journals (Sweden)

    Anthony R Bradley

    2017-06-01

    Full Text Available Recent advances in experimental techniques have led to a rapid growth in complexity, size, and number of macromolecular structures that are made available through the Protein Data Bank. This creates a challenge for macromolecular visualization and analysis. Macromolecular structure files, such as PDB or PDBx/mmCIF files can be slow to transfer, parse, and hard to incorporate into third-party software tools. Here, we present a new binary and compressed data representation, the MacroMolecular Transmission Format, MMTF, as well as software implementations in several languages that have been developed around it, which address these issues. We describe the new format and its APIs and demonstrate that it is several times faster to parse, and about a quarter of the file size of the current standard format, PDBx/mmCIF. As a consequence of the new data representation, it is now possible to visualize structures with millions of atoms in a web browser, keep the whole PDB archive in memory or parse it within few minutes on average computers, which opens up a new way of thinking how to design and implement efficient algorithms in structural bioinformatics. The PDB archive is available in MMTF file format through web services and data that are updated on a weekly basis.

  19. Synthesis and characterization of macromolecular rhodamine tethers and their interactions with P-glycoprotein.

    Science.gov (United States)

    Crawford, Lindsey; Putnam, David

    2014-08-20

    Rhodamine dyes are well-known P-glycoprotein (P-gp) substrates that have played an important role in the detection of inhibitors and other substrates of P-gp, as well as in the understanding of P-gp function. Macromolecular conjugates of rhodamines could prove useful as tethers for further probing of P-gp structure and function. Two macromolecular derivatives of rhodamine, methoxypolyethylene glycol-rhodamine6G and methoxypolyethylene glycol-rhodamine123, were synthesized through the 2'-position of rhodamine6G and rhodamine123, thoroughly characterized, and then evaluated by inhibition with verapamil for their ability to interact with P-gp and to act as efflux substrates. To put the results into context, the P-gp interactions of the new conjugates were compared to the commercially available methoxypolyethylene glycol-rhodamineB. FACS analysis confirmed that macromolecular tethers of rhodamine6G, rhodamine123, and rhodamineB were accumulated in P-gp expressing cells 5.2 ± 0.3%, 26.2 ± 4%, and 64.2 ± 6%, respectively, compared to a sensitive cell line that does not overexpress P-gp. Along with confocal imaging, the efflux analysis confirmed that the macromolecular rhodamine tethers remain P-gp substrates. These results open potential avenues for new ways to probe the function of P-gp both in vitro and in vivo.

  20. Interplay between the bacterial nucleoid protein H-NS and macromolecular crowding in compacting DNA

    NARCIS (Netherlands)

    Wintraecken, C.H.J.M.

    2012-01-01

    In this dissertation we discuss H-NS and its connection to nucleoid compaction and organization. Nucleoid formation involves a dramatic reduction in coil volume of the genomic DNA. Four factors are thought to influence coil volume: supercoiling, DNA charge neutralization, macromolecular

  1. Effect of macromolecular crowding on the rate of diffusion-limited ...

    Indian Academy of Sciences (India)

    The enzymatic reaction rate has been shown to be affected by the presence of such macromolecules. A simple numerical model is proposed here based on percolation and diffusion in disordered systems to study the effect of macromolecular crowding on the enzymatic reaction rates. The model qualitatively explains some ...

  2. Detection and cellular localisation of the synthetic soluble macromolecular drug carrier pHPMA

    Czech Academy of Sciences Publication Activity Database

    Kissel, M.; Peschke, P.; Šubr, Vladimír; Ulbrich, Karel; Strunz, A. M.; Kühnlein, R.; Debus, J.; Friedrich, E.

    2002-01-01

    Roč. 29, č. 8 (2002), s. 1055-1062 ISSN 1619-7070 R&D Projects: GA ČR GV307/96/K226 Institutional research plan: CEZ:AV0Z4050913 Keywords : EPR effect * Radiolabelled macromolecules * Pharmacokinetic Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.568, year: 2002

  3. Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy.

    Science.gov (United States)

    Loquet, Antoine; Tolchard, James; Berbon, Melanie; Martinez, Denis; Habenstein, Birgit

    2017-09-17

    Supramolecular protein assemblies play fundamental roles in biological processes ranging from host-pathogen interaction, viral infection to the propagation of neurodegenerative disorders. Such assemblies consist in multiple protein subunits organized in a non-covalent way to form large macromolecular objects that can execute a variety of cellular functions or cause detrimental consequences. Atomic insights into the assembly mechanisms and the functioning of those macromolecular assemblies remain often scarce since their inherent insolubility and non-crystallinity often drastically reduces the quality of the data obtained from most techniques used in structural biology, such as X-ray crystallography and solution Nuclear Magnetic Resonance (NMR). We here present magic-angle spinning solid-state NMR spectroscopy (SSNMR) as a powerful method to investigate structures of macromolecular assemblies at atomic resolution. SSNMR can reveal atomic details on the assembled complex without size and solubility limitations. The protocol presented here describes the essential steps from the production of 13 C/ 15 N isotope-labeled macromolecular protein assemblies to the acquisition of standard SSNMR spectra and their analysis and interpretation. As an example, we show the pipeline of a SSNMR structural analysis of a filamentous protein assembly.

  4. Thermodynamics of Macromolecular Association in Heterogeneous Crowding Environments: Theoretical and Simulation Studies with a Simplified Model.

    Science.gov (United States)

    Ando, Tadashi; Yu, Isseki; Feig, Michael; Sugita, Yuji

    2016-11-23

    The cytoplasm of a cell is crowded with many different kinds of macromolecules. The macromolecular crowding affects the thermodynamics and kinetics of biological reactions in a living cell, such as protein folding, association, and diffusion. Theoretical and simulation studies using simplified models focus on the essential features of the crowding effects and provide a basis for analyzing experimental data. In most of the previous studies on the crowding effects, a uniform crowder size is assumed, which is in contrast to the inhomogeneous size distribution of macromolecules in a living cell. Here, we evaluate the free energy changes upon macromolecular association in a cell-like inhomogeneous crowding system via a theory of hard-sphere fluids and free energy calculations using Brownian dynamics trajectories. The inhomogeneous crowding model based on 41 different types of macromolecules represented by spheres with different radii mimics the physiological concentrations of macromolecules in the cytoplasm of Mycoplasma genitalium. The free energy changes of macromolecular association evaluated by the theory and simulations were in good agreement with each other. The crowder size distribution affects both specific and nonspecific molecular associations, suggesting that not only the volume fraction but also the size distribution of macromolecules are important factors for evaluating in vivo crowding effects. This study relates in vitro experiments on macromolecular crowding to in vivo crowding effects by using the theory of hard-sphere fluids with crowder-size heterogeneity.

  5. Crosslinked polyurethanes based on hyperbranched polymers

    Directory of Open Access Journals (Sweden)

    Vuković Jasna

    2008-01-01

    Full Text Available In this paper, two samples of polyurethane (PU crosslinked with hydroxy -functonal hyperbranched aliphatic polyester of the second pseudo generation were investigated. For the synthesis of these crosslinked PUs two different macrodiols were used: poly(tetramethyleneoxide (PTMO for PUPTMO and ethylene oxide-poly(dimethylsiloxane-ethylene oxide (PDMS-EO for PUPDMS-EO sample. Synthesized samples behave as elastomers and have yellow color. Obtained results show that swelling degree of the sample PUPDMS-EO in N-methyl-2-pyrrolidinon (NMP determined at room temperature is higher than for the sample PUPTMO. It has been also observed that thermal properties of these polyurethane networks can be changed by incorporation of siloxane sequences in their structure.

  6. General protein-protein cross-linking.

    Science.gov (United States)

    Alegria-Schaffer, Alice

    2014-01-01

    This protocol describes a general protein-to-protein cross-linking procedure using the water-soluble amine-reactive homobifunctional BS(3) (bis[sulfosuccinimidyl] suberate); however, the protocol can be easily adapted using other cross-linkers of similar properties. BS(3) is composed of two sulfo-NHS ester groups and an 11.4 Å linker. Sulfo-NHS ester groups react with primary amines in slightly alkaline conditions (pH 7.2-8.5) and yield stable amide bonds. The reaction releases N-hydroxysuccinimide (see an application of NHS esters on Labeling a protein with fluorophores using NHS ester derivitization). © 2014 Elsevier Inc. All rights reserved.

  7. Mesoscopic Simulations of Crosslinked Polymer Networks

    Science.gov (United States)

    Megariotis, Grigorios; Vogiatzis, Georgios G.; Schneider, Ludwig; Müller, Marcus; Theodorou, Doros N.

    2016-08-01

    A new methodology and the corresponding C++ code for mesoscopic simulations of elastomers are presented. The test system, crosslinked ds-1’4-polyisoprene’ is simulated with a Brownian Dynamics/kinetic Monte Carlo algorithm as a dense liquid of soft, coarse-grained beads, each representing 5-10 Kuhn segments. From the thermodynamic point of view, the system is described by a Helmholtz free-energy containing contributions from entropic springs between successive beads along a chain, slip-springs representing entanglements between beads on different chains, and non-bonded interactions. The methodology is employed for the calculation of the stress relaxation function from simulations of several microseconds at equilibrium, as well as for the prediction of stress-strain curves of crosslinked polymer networks under deformation.

  8. Protein cross-linking by chlorinated polyamines and transglutamylation stabilizes neutrophil extracellular traps.

    Science.gov (United States)

    Csomós, Krisztián; Kristóf, Endre; Jakob, Bernadett; Csomós, István; Kovács, György; Rotem, Omri; Hodrea, Judit; Bagoly, Zsuzsa; Muszbek, Laszlo; Balajthy, Zoltán; Csősz, Éva; Fésüs, László

    2016-08-11

    Neutrophil extracellular trap (NET) ejected from activated dying neutrophils is a highly ordered structure of DNA and selected proteins capable to eliminate pathogenic microorganisms. Biochemical determinants of the non-randomly formed stable NETs have not been revealed so far. Studying the formation of human NETs we have observed that polyamines were incorporated into the NET. Inhibition of myeloperoxidase, which is essential for NET formation and can generate reactive chlorinated polyamines through hypochlorous acid, decreased polyamine incorporation. Addition of exogenous primary amines that similarly to polyamines inhibit reactions catalyzed by the protein cross-linker transglutaminases (TGases) has similar effect. Proteomic analysis of the highly reproducible pattern of NET components revealed cross-linking of NET proteins through chlorinated polyamines and ɛ(γ-glutamyl)lysine as well as bis-γ-glutamyl polyamine bonds catalyzed by the TGases detected in neutrophils. Competitive inhibition of protein cross-linking by monoamines disturbed the cross-linking pattern of NET proteins, which resulted in the loss of the ordered structure of the NET and significantly reduced capacity to trap bacteria. Our findings provide explanation of how NETs are formed in a reproducible and ordered manner to efficiently neutralize microorganisms at the first defense line of the innate immune system.

  9. Cross-linked polyethylene does not reduce wear in total knee arthroplasty.

    Science.gov (United States)

    Lasurt-Bachs, S; Torner, P; Maculé, F; Prats, E; Menéndez-García, F; Ríos-Guillermo, J; Torrents, A

    To compare two different types of inserts: Ultra-high molecular weight polyethylene (UHMWPE) and cross-linked polyethylene with a quantitative and qualitative study of polyethylene wear particles in synovial fluid 3 years after total knee arthroplasty. A prospective, randomized, controlled cohort study with blinded evaluation was carried out on 25 patients undergoing staged bilateral total knee replacement, 6 months apart. Knee arthrocentesis was performed on 12 patients 3 years after surgery, and the polyethylene particles were analyzed. No significant differences were found in the number of particles generated by the two different types of inserts at 3 years from total knee arthroplasty (3,000×: x¯ cross-linked=849.7; x¯ UHMWPE=796.9; P=.63; 20,000×: x¯ cross-linked=66.3; x¯ UHMWPE=73.1; P=.76). Likewise, no differences in the probability of finding elongated (χ 2 =0.19; P=.66) or rounded (χ 2 =1.44; P=.23) particles in both types of inserts were observed. However, the probability of finding fibrillar particles is 3.08 times greater in UHMWPE. Cross-linked polyethylene does not significantly reduce the generation of polyethylene particles in patients with total knee arthroplasty, 3 years after the surgical procedure. Copyright © 2018 SECOT. Publicado por Elsevier España, S.L.U. All rights reserved.

  10. Radiation crosslinking of PVC with polyfunctional monomers

    International Nuclear Information System (INIS)

    Dobo, J.; Takacs, E.; Csato, P.

    1984-01-01

    The radiation crosslinking of PVC in the presence of ethylene glycol dimethacrylate (EGDM) and of trimethylol propane trimethacrylate (TMPTM) was investigated. The effect of PVC powders of different types on the polymerization rate of these monomers was studied by a Calvet-type microcalorimeter. In the milled PVC sheets containing 50 part EGDM a high concentration of trapped free radicals was found by ESR after 16 months storage. (author)

  11. Intrastromal crosslinking in post-LASIK ectasia

    Directory of Open Access Journals (Sweden)

    Bernardo Kaplan Moscovici

    2014-06-01

    Full Text Available Descrevemos um caso de ectasia de córnea precoce após cirurgia de LASIK, detectado no primeiro semestre pós-operatório. Nós optamos tratar este paciente com "crosslinking" embaixo do "flap" , sem desepitelização com bons resultados. A paciente permaneceu sem progressão da ectasia até o momento atual, dois anos após o procedimento.

  12. Adhesion between Polydimethylsiloxane Layers by Crosslinking

    DEFF Research Database (Denmark)

    Yu, Liyun; Daugaard, Anders Egede; Skov, Anne Ladegaard

    2013-01-01

    Adhesion between two surfaces may be strongly improved by chemical crosslinking of the interfaces. Polydimethylsiloxane (PDMS) is a widely used polymer that has received considerable attention due to its unique properties, such as relatively low price, biocompatibility, flexibility, high thermal...... investigated by rheology and microscopy. The objective of this work was to create adhesion of two layers without destroying the original viscoelastic properties of the PDMS films....

  13. Hyperbranched Polyethylenebased Macromolecular Architectures: Synthesis, Characterization, and Selfassembly

    KAUST Repository

    Al-Sulami, Ahlam

    2018-05-01

    "Chain walking” catalytic polymerization CWCP is a powerful tool for the one-pot synthesis of a unique class of hyperbranched polyethylene HBPE-based macromolecules with a controllable molecular weight, topology, and composition. This dissertation focuses on new synthetic routes to prepare HBPE-based macromolecular architectures by combining the CWCP technique with ring opening polymerization ROP, atom–transfer radical polymerization ATRP, and “click” chemistry. Taking advantage of end-functionalized HBPE, and a new ethynyl-soketal star-shape agent, we were able to synthesize different types of the HBPE-based architectures including hyperbranched-on-hyperbranched core-shell nanostructure, and miktoarm-star-HBPE-based block copolymers. The first part of the dissertation provides a general introduction to the synthesis of polyethylene types with controllable structures. Well-defined polyethylene with different macromolecule architectures were synthesized either for academic or industrial purposes. In the second part, the HBPE with different topologies was synthesized by CWCP, using a α-diimine Pd (II) catalyst. The effect of the temperature and pressure on the catalyst activity and polymer properties, including branch content, molecular weight, distribution, and thermal properties were studied. Two series of samples were synthesized: a) serial samples (A) under pressures of 1, 5, and 27 atm at 5˚C, and b) serial samples (B) at temperatures of 5, 15, and 35 ˚C under 5 atm. Proton nuclear magnetic resonance spectroscopy, 1H NMR, and gel permeation chromatography, GPC, analysis were used to calculate the branching content, molecular weight, and distribution, whereas differential scanning calorimetry, DSC, was used to record the melting and glass transition temperatures as well as the degree of the crystallinity. Well-defined HBPE-based core diblock copolymers with predictable amphiphilic properties are studied in the third part of the project. Hyperbranched

  14. Electron beam crosslinked PVC : structure property relationships

    International Nuclear Information System (INIS)

    Gupta, Neeraj K.; Sabharwal, Sunil

    2001-01-01

    PVC is used extensively for its insulating properties for the manufacture of wires and cables and for other applications. Its gradual degradation, oxidation and even dehydro chlorination restricts use for long lasting period in installations such as high temperature zones, underground cables, communication systems, electro-nuclear facilities, etc. The technological properties and performance characteristics of PVC based insulation can be improved via crosslinking by high-energy electrons. PVC is however a polymer, which on irradiation predominantly undergoes degradation. To avoid degradation, it needs to be compounded with sensitizing agents or multifunctional monomers so that crosslinking is the predominant reaction. Radiation cross linkable formulations are complex mixtures of resin and various additives incorporated for achieving desired technological and performance characteristics, ease of processing and improving quality. The proper choice of additives and sensitizing agents enable low dose requirements for efficient crosslinking and improvements in various technological properties. The purposes of this work was to investigate the effect of using a binary sensitizer blend of a trifunctional monomer and a rubber in PVC, and develop suitable electron beam cross linkable formulations for wire insulation. This paper presents some aspects of the investigations and development of insulation demonstrated at industrial scale

  15. Epoxy Crosslinked Silica Aerogels (X-Aerogels)

    Science.gov (United States)

    fabrizio, Eve; Ilhan, Faysal; Meador, Mary Ann; Johnston, Chris; Leventis, Nicholas

    2004-01-01

    NASA is interested in the development of strong lightweight materials for the dual role of thermal insulator and structural component for space vehicles; freeing more weight for useful payloads. Aerogels are very-low density materials (0.010 to 0.5 g/cc) that, due to high porosity (meso- and microporosity), can be, depending on the chemical nature of the network, ideal thermal insulators (thermal conductivity approx. 15 mW/mK). However, aerogels are extremely fragile. For practical application of aerogels, one must increase strength without compromising the physical properties attributed to low density. This has been achieved by templated growth of an epoxy polymer layer that crosslinks the "pearl necklace" network of nanoparticles: the framework of a typical silica aerogel. The requirement for conformal accumulation of the epoxy crosslinker is reaction both with the surface of silica and with itself. After cross-linking, the strength of a typical aerogel monolith increases by a factor of 200, in the expense of only a 2-fold increase in density. Strength is increased further by coupling residual unreacted epoxides with diamine.

  16. Collagen cross-linking in thin corneas

    Directory of Open Access Journals (Sweden)

    Prema Padmanabhan

    2013-01-01

    Full Text Available Collagen cross-linking (CXL has become the standard of care for progressive keratoconus, after numerous clinical studies have established its efficacy and safety in suitably selected eyes. The standard protocol is applicable in eyes which have a minimum corneal thickness of 400 μm after epithelial debridement. This prerequisite was stipulated to protect the corneal endothelium and intraocular tissues from the deleterious effect of ultraviolet-A (UVA radiation. However, patients with keratoconus often present with corneal thickness of less than 400 μm and could have otherwise benefited from this procedure. A few modifications of the standard procedure have been suggested to benefit these patients without a compromise in safety. Transepithelial cross-linking, pachymetry-guided epithelial debridement before cross-linking, and the use of hypoosmolar riboflavin are some of the techniques that have been attempted. Although clinical data is limited at the present time, these techniques are worth considering in patients with thin corneas. Further studies are needed to scientifically establish their efficacy and safety.

  17. Crosslinked anion exchange membranes with primary diamine-based crosslinkers for vanadium redox flow battery application

    Science.gov (United States)

    Cha, Min Suc; Jeong, Hwan Yeop; Shin, Hee Young; Hong, Soo Hyun; Kim, Tae-Ho; Oh, Seong-Geun; Lee, Jang Yong; Hong, Young Taik

    2017-09-01

    A series of polysulfone-based crosslinked anion exchange membranes (AEMs) with primary diamine-based crosslinkers has been prepared via simple a crosslinking process as low-cost and durable membranes for vanadium redox flow batteries (VRFBs). Chloromethylated polysulfone is used as a precursor polymer for crosslinked AEMs (CAPSU-x) with different degrees of crosslinking. Among the developed AEMs, CAPSU-2.5 shows outstanding dimensional stability and anion (Cl-, SO42-, and OH-) conductivity. Moreover, CAPSU-2.5 exhibits much lower vanadium ion permeability (2.72 × 10-8 cm2 min-1) than Nafion 115 (2.88 × 10-6 cm2 min-1), which results in an excellent coulombic efficiency of 100%. The chemical and operational stabilities of the membranes have been investigated via ex situ soaking tests in 0.1 M VO2+ solution and in situ operation tests for 100 cycles, respectively. The excellent chemical, physical, and electrochemical properties of the CAPSU-2.5 membrane make it suitable for use in VRFBs.

  18. Corneal collagen crosslinking for keratoconus. A review

    Directory of Open Access Journals (Sweden)

    M. M. Bikbov

    2014-10-01

    Full Text Available Photochemical crosslinking is widely applied in ophthalmology. Its biochemical effect is due to the release of singlet oxygen that promotes anaerobic photochemical reaction. Keratoconus is one of the most common corneal ectasia affecting 1 in 250 to 250 000 persons. Currently, the rate of iatrogenic ectasia following eximer laser refractive surgery increases due to biomechanical weakening of the cornea. Morphologically and biochemically, ectasia is characterized by corneal layers thinning, contact between the stroma and epithelium resulting from Bowman’s membrane rupture, chromatin fragmentation in keratocyte nuclei, phagocytosis, abnormal staining and arrangement of collagen fibers, enzyme system disorders, and keratocyte apoptosis. In corneal ectasia, altered enzymatic processes result in the synthesis of abnormal collagen. Collagen packing is determined by the activity of various extracellular matrix enzymes which bind amines and aldehydes of collagen fiber amino acids. In the late stage, morphological changes of Descemet’s membrane (i.e., rupture and detachment develop. Abnormal hexagonal-shaped keratocytes and their apoptosis are the signs of endothelial dystrophy. The lack of analogs in domestic ophthalmology encouraged the scientists of Ufa Eye Research Institute to develop a device for corneal collagen crosslinking. The parameters of ultraviolet (i.e., wavelength, exposure time, power to achieve the desired effect were identified. The specifics of some photosensitizers in the course of the procedure were studied. UFalink, a device for UV irradiation of cornea, and photosensitizer Dextralink were developed and adopted. Due to the high risk of endothelial damage, this treatment is contraindicated in severe keratoconus (CCT less than 400 microns. Major effects of corneal collagen crosslinking are the following: Young’s modulus (modulus of elasticity increase by 328.9 % (on average, temperature tolerance increase by 5

  19. Cross-link guided molecular modeling with ROSETTA.

    Directory of Open Access Journals (Sweden)

    Abdullah Kahraman

    Full Text Available Chemical cross-links identified by mass spectrometry generate distance restraints that reveal low-resolution structural information on proteins and protein complexes. The technology to reliably generate such data has become mature and robust enough to shift the focus to the question of how these distance restraints can be best integrated into molecular modeling calculations. Here, we introduce three workflows for incorporating distance restraints generated by chemical cross-linking and mass spectrometry into ROSETTA protocols for comparative and de novo modeling and protein-protein docking. We demonstrate that the cross-link validation and visualization software Xwalk facilitates successful cross-link data integration. Besides the protocols we introduce XLdb, a database of chemical cross-links from 14 different publications with 506 intra-protein and 62 inter-protein cross-links, where each cross-link can be mapped on an experimental structure from the Protein Data Bank. Finally, we demonstrate on a protein-protein docking reference data set the impact of virtual cross-links on protein docking calculations and show that an inter-protein cross-link can reduce on average the RMSD of a docking prediction by 5.0 Å. The methods and results presented here provide guidelines for the effective integration of chemical cross-link data in molecular modeling calculations and should advance the structural analysis of particularly large and transient protein complexes via hybrid structural biology methods.

  20. Flexibility damps macromolecular crowding effects on protein folding dynamics: Application to the murine prion protein (121-231)

    Science.gov (United States)

    Bergasa-Caceres, Fernando; Rabitz, Herschel A.

    2014-01-01

    A model of protein folding kinetics is applied to study the combined effects of protein flexibility and macromolecular crowding on protein folding rate and stability. It is found that the increase in stability and folding rate promoted by macromolecular crowding is damped for proteins with highly flexible native structures. The model is applied to the folding dynamics of the murine prion protein (121-231). It is found that the high flexibility of the native isoform of the murine prion protein (121-231) reduces the effects of macromolecular crowding on its folding dynamics. The relevance of these findings for the pathogenic mechanism are discussed.

  1. New crosslinked polyvinyl chloride insulated wire by electron beam irradiation

    International Nuclear Information System (INIS)

    Takahata, Norio; Shingyouchi, Kazuo; Sato, Masakatsu; Sasaki, Hidemi; Terunuma, Haruji

    1978-01-01

    The polyvinyl chloride-coated wires crosslinked by electron beam irradiation have made rapid progress as electric and electronic wiring material and grown to hold a firm position in this field. In response to the requirements for wires with the advance of electronic equipments, Hitachi Cable Ltd. developed a peculiar graft polymer consisting of chlorinated polyethylene and polyvinyl chloride. To this polymer, the characteristics of a very wide range from toughness to flexibility can be given, and the crosslinked polyvinyl chloride wires utilizing these characteristics were put in practical use. Many kinds of the wires were developed as follows; 105 deg. C rating crosslinked vinyl-coated wires authorized by UL and CSA standards, crosslinked vinyl-coated wires with excellent flexibility, high strength crosslinked vinyl-coated wires with thin coating and crosslinked vinyl-coated wires for automobiles. They are expected to be developed into other new fields and applications. (Kobatake, H.)

  2. Crosslinking of thermoplastic composites using electron beam radiation

    International Nuclear Information System (INIS)

    Strong, A.B.; Black, S.R.; Bryce, G.R.; Olcott, D.D.

    1991-01-01

    The crosslinking of thermoset materials has been clearly demonstrated to improve many desirable physical and chemical properties for composite applications. While thermoplastic resins also offer many advantages for composite applications, they are not crosslinked and, therefore, may not meet the same property criteria as crosslinked thermosets. Electron beams have been used successfully for crosslinking non-reinforced thermoplastic materials. Electron beams have also been used for curing composite thermoset materials. This research utilizes electron beams to crosslink high performance thermoplastic composite materials (PEEK and PPS with glass and carbon fibers). The tensile strength and tensile modulus are compared under various crosslinking conditions. The method is found to have some advantages in potentially improving physical properties of thermoplastic composite materials

  3. A NOVEL APPROACH TO SYNTHESIZE CHITOSAN BEADS CROSSLINKED BY EPICHLOROHYDRIN

    Institute of Scientific and Technical Information of China (English)

    WANG Yongjian; BAI Shu; SUN Yan

    2001-01-01

    The present investigation describes a novel method for preparing spherical chitosan particles based on crosslinking with epichlorohydrin. Certain amount of pre-crosslinking agent was added to form chitosan gels by traditional inverse phase suspension polymerization. Then the gels were crosslinked by epichlorohydrin at basic condition to obtain chitosan beads. The effects of reaction conditions, such as crosslinking time, the amount of crosslinking agent and the NaOtt concentration,on the physical properties of the chitosan beads were investigated. The beads were found to have more amino groups in the polymer chains than the beads crosslinked by glutaraldehyde. The capacity for copper ions is as high as 40mg/g. The beads have good mechanical strength and can be reused.

  4. A NOVEL APPROACH TO SYNTHESIZE CHITOSAN BEADS CROSSLINKED BY EPICHLOROHYDRIN

    Institute of Scientific and Technical Information of China (English)

    WANGYongjina; BAIShu; 等

    2001-01-01

    The present investigation describes a novel method for preparing spherical chitosan particles based on crosslinking with epichlorohydrin.Certain amount of pre-crosslinking agent was added to form chitosan gels by traditional inverse phase suspension polymerization.Then the gels were crosslinked by epichlorohydrin at basic condition to obtain chitosan beads.The effects of reaction conditions,such as crosslinking time,the amount of crosslinking agent and the NaOH concentration,on the physical properties of the chitosan beads were investigated.The beads were found to have more amino groups in the polymer chains than the beads crosslinked by glutaraldehyde.The capacity for copper ions in as high as 40mg/g,The beads have good mechanical strength and can be reused.

  5. Crosslinkers of Different Types in Precipitation Polymerization of Acrylic Acid

    Directory of Open Access Journals (Sweden)

    H. Eshaghi

    2013-01-01

    Full Text Available Crosslinked poly(acrylic acids were prepared using two types of crosslinker by precipitation polymerization method in a binary organic solvent. N,N’-methylenebisacrylamide (MBA and polyethylene glycol dimethacrylate (PEGDMA-330 were used as low-molecular weight and long-chain crosslinkers, respectively. The effect of various types of crosslinkers on polymer characteristics (i.e., gel content, equilibrium swelling, glass transition temperature, and rheological properties was investigated. Maximum amount of viscosity was obtained by using long-chain crosslinker. The Flory-Rehner equation and rubber elasticity theory were used to discuss the network structure of polymer. It was observed that, the glass transition temperature (Tg of the synthesized polymer containing PEGDMA-330 is higher than that of polymer containing MBA. Apparent and rotational viscosity were used to determine the optimal crosslinker type. In addition, the consistencycoefficient (m and flow behavior index (n parameter of Ostwald equation were investigated as well.

  6. Interstrand DNA crosslinks due to AP (apurinic/apyrimidinic) sites

    International Nuclear Information System (INIS)

    Goffin, C.; Verly, W.G.

    1983-01-01

    Storage of a solution of DNA containing apurinic sites, even at 4 0 C leads to the appearance of interstrand crosslinks. Possible consequences of these crosslinks, when they appear in cell DNA, are briefly discussed. Formation of interstrand crosslinks in DNA containing tritium-labelled thymine and kept in an aqueous solution might be due, at least partly, to the loss of bases by the autoirradiated DNA. (Auth.)

  7. Covalent DNA-protein crosslinking occurs after hyperthermia and radiation

    International Nuclear Information System (INIS)

    Cress, A.E.; Bowden, G.T.

    1983-01-01

    Covalent DNA-protein crosslinks occur in exponentially growing mouse leukemia cells (L1210) after exposure to ionizing radiation. The amount of DNA-protein crosslinks as measured by a filter binding assay is dose dependent upon X irradiation. Although hyperthermia and radiation in combination are synergistic with respect to cell lethality, the combination does not result in an increase of DNA-protein crosslinks when assayed immediately following treatments. Hyperthermia (43 degrees C/15 min) given prior to radiation does not alter the radiation dose dependency of the amount of initial crosslinking. In addition, the amount of DNA-protein crosslinking produced by heat plus radiation is independent of the length of heating the cells at 43 degrees C. The DNA-protein crosslinks produced by 50-Gy X ray alone are removed after 2 hr at 37 degrees C. However, if hyperthermia (43 degrees C/15 min) is given prior to 100-Gy X ray, the removal of DNA-protein crosslinks is delayed until 4.0 hr after radiation. Phospho-serine and phospho-threonine bonds are not produced with either radiation or the combination of hyperthermia plus radiation as judged by the resistance of the bonds to guanidine hydrochloride. However, hyperthermia plus radiation causes an increase in phosphate to nitrogen type bonding. These results show that radiation alone causes covalent DNA-protein crosslinks. Hyperthermia in combination with radiation does not increase the total amount of the crosslinks but delays the removal of the crosslinks and alters the distribution of the types of chemical bonding. These data suggest that the synergistic action on hyperthermia with radiation is more related to the rate of removal and the type of chemical bonding involved in the covalent DNA-protein crosslinks rather than the amount of DNA-protein crosslinks

  8. Transepithelial photorefractive keratectomy with crosslinking for keratoconus.

    Science.gov (United States)

    Mukherjee, Achyut N; Selimis, Vasilis; Aslanides, Ioannis

    2013-01-01

    To analyse visual, refractive and topographic outcomes of combining transepithelial photorefractive keratectomy (tPRK) with simultaneous corneal crosslinking for the visual rehabilitation of contact lens intolerant keratoconus patients. Patients with topographically significant keratoconus, limited corrected vision and intolerant of contact lenses were prospectively recruited, subject to ethical approval and consent. All patients underwent single step aspheric tPRK and sequential crosslinking. Preoperative vision, refraction, corneal topography and wavefront were assessed, with postoperative assessment at 1, 3, 6, and 12 months. 22 eyes of 14 patients were included in the pilot study. Mean age was 32 years (SD 6.8, range 24 to 43). Mean preoperative unaided vision was 1.39 LogMAR (SD 0.5) best corrected 0.31 LogMAR (SD 0.2). Mean preoperative spherical equivalent was -2.74 Diopters (D) (SD 4.1 range -12.25 to +7.75), and mean cylinder -2.9 D (SD 1.2, range 0 to -5.5). Mean central corneal thickness was 461um (SD 29, range 411 to 516). Vision improved postoperatively; unaided 0.32 LogMAR (SD 0.4), best corrected 0.11 (SD 0.13) (P=<0.005). Mean postoperative cylinder was -1.4D (SD1.2), significantly reduced (p<0.005). Maximum keratometry (Kmax) was stable throughout postoperative follow up. (p<0.05). Non topographic transepithelial PRK with simultaneous crosslinking improves vision, and may offer an alternative to keratoplasty in contact lens intolerant keratoconus. Further comparative studies to topographic PRK techniques are indicated.

  9. Comparison study of crosslink density determination in cured rubber

    International Nuclear Information System (INIS)

    El-sabbagh, S.H.; Yehia, A.A.

    2005-01-01

    The crosslink density is an important property affecting the major characteristics of cured rubber. The crosslink density can be determined by different methods such as: 1. Dynamic mechanical method using the data of stress-strain relationship. 2. Mooney-Rivlin equation 3. Swelling in organic solvents measurements using Flory-Rehner equation. The crosslink density calculated by the previous methods were discussed and compared with each other for cured NR, SBR and NBR. The obtained data showed that the dynamic-mechanical method can be considered as a simple and reliable method for determination of crosslink density for cured rubbers

  10. Irradiation Crosslinking of Polyamides for the Electrical and Automotive Industry

    International Nuclear Information System (INIS)

    Gehring, J.

    2006-01-01

    Irradiation crosslinking of electrical cables and heat shrinkable tubes have been widely accepted in the automotive and electrical industry for a long time. Due higher demands regarding temperature resistance, arc resistance and good chemical resistance against oil and greases crosslinked injection moulded parts made out of polyamid and polybutylentherephtalate become also more and more interesting. Crosslinked polyamide can also replace thermosets for switches and offers therefore additional financial benefits. It will be shown on the basis of already realized projects, which basic requirements exist and how irradiation crosslinking can fulfil these demands

  11. Radiation crosslinking of polymers with segregated metallic particles. Final report, June 1, 1971--September 30, 1973

    International Nuclear Information System (INIS)

    Corneliussen, R.D.; Kamel, I.; Kusy, R.P.

    1973-01-01

    Through the past four years of research, a new approach to fabricating conductive polymer/metal composites has been developed. This approach consists of compacting mixtures of polymer and metal powders and then stabilizing the composite through radiation-induced crosslinking. The result is a mechanically strong, conductive materials consisting of two intertwining networks. One is a massive network consisting of fused crosslinked, large (greater than 100 μ) polymer particles while the other is a fine network of small, metallic particles (greater than 10 μ). Nine different systems including crystalline, amorphous, and rubbery polymers were studied. Processing at this time is limited to compression molding in a closed die because of network stability problems. Costs for processing were estimated at about $6.00/lb compared to $50.00 and up for commercial material based on random networks. (U.S.)

  12. Coevolutionary constraints in the sequence-space of macromolecular complexes reflect their self-assembly pathways.

    Science.gov (United States)

    Mallik, Saurav; Kundu, Sudip

    2017-07-01

    Is the order in which biomolecular subunits self-assemble into functional macromolecular complexes imprinted in their sequence-space? Here, we demonstrate that the temporal order of macromolecular complex self-assembly can be efficiently captured using the landscape of residue-level coevolutionary constraints. This predictive power of coevolutionary constraints is irrespective of the structural, functional, and phylogenetic classification of the complex and of the stoichiometry and quaternary arrangement of the constituent monomers. Combining this result with a number of structural attributes estimated from the crystal structure data, we find indications that stronger coevolutionary constraints at interfaces formed early in the assembly hierarchy probably promotes coordinated fixation of mutations that leads to high-affinity binding with higher surface area, increased surface complementarity and elevated number of molecular contacts, compared to those that form late in the assembly. Proteins 2017; 85:1183-1189. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  13. Clustering procedures for the optimal selection of data sets from multiple crystals in macromolecular crystallography

    International Nuclear Information System (INIS)

    Foadi, James; Aller, Pierre; Alguel, Yilmaz; Cameron, Alex; Axford, Danny; Owen, Robin L.; Armour, Wes; Waterman, David G.; Iwata, So; Evans, Gwyndaf

    2013-01-01

    A systematic approach to the scaling and merging of data from multiple crystals in macromolecular crystallography is introduced and explained. The availability of intense microbeam macromolecular crystallography beamlines at third-generation synchrotron sources has enabled data collection and structure solution from microcrystals of <10 µm in size. The increased likelihood of severe radiation damage where microcrystals or particularly sensitive crystals are used forces crystallographers to acquire large numbers of data sets from many crystals of the same protein structure. The associated analysis and merging of multi-crystal data is currently a manual and time-consuming step. Here, a computer program, BLEND, that has been written to assist with and automate many of the steps in this process is described. It is demonstrated how BLEND has successfully been used in the solution of a novel membrane protein

  14. Variationally optimal selection of slow coordinates and reaction coordinates in macromolecular systems

    Science.gov (United States)

    Noe, Frank

    To efficiently simulate and generate understanding from simulations of complex macromolecular systems, the concept of slow collective coordinates or reaction coordinates is of fundamental importance. Here we will introduce variational approaches to approximate the slow coordinates and the reaction coordinates between selected end-states given MD simulations of the macromolecular system and a (possibly large) basis set of candidate coordinates. We will then discuss how to select physically intuitive order paremeters that are good surrogates of this variationally optimal result. These result can be used in order to construct Markov state models or other models of the stationary and kinetics properties, in order to parametrize low-dimensional / coarse-grained model of the dynamics. Deutsche Forschungsgemeinschaft, European Research Council.

  15. Local analysis of strains and rotations for macromolecular electron microscopy maps

    Energy Technology Data Exchange (ETDEWEB)

    Martin-Ramos, A.; Prieto, F.; Melero, R.; Martin-Benito, J.; Jonic, S.; Navas-Calvente, J.; Vargas, J.; Oton, J.; Abrishami, V.; Rosa-Trevin, J.L. de la; Gomez-Blanco, J.; Vilas, J.L.; Marabini, R.; Carazo, R.; Sorzano, C.O.S.

    2016-07-01

    Macromolecular complexes can be considered as molecular nano-machines that must have mobile parts in order to perform their physiological functions. The reordering of their parts is essential to execute their task. These rearrangements induce local strains and rotations which, after analyzing them, may provide relevant information about how the proteins perform their function. In this project these deformations of the macromolecular complexes are characterized, translating into a “mathematical language” the conformational changes of the complexes when they perform their function. Electron Microscopy (EM) volumes are analyzed using a method that uses B-splines as its basis functions. It is shown that the results obtained are consistent with the conformational changes described in their corresponding reference publications. (Author)

  16. Macromolecularly crowded in vitro microenvironments accelerate the production of extracellular matrix-rich supramolecular assemblies.

    Science.gov (United States)

    Kumar, Pramod; Satyam, Abhigyan; Fan, Xingliang; Collin, Estelle; Rochev, Yury; Rodriguez, Brian J; Gorelov, Alexander; Dillon, Simon; Joshi, Lokesh; Raghunath, Michael; Pandit, Abhay; Zeugolis, Dimitrios I

    2015-03-04

    Therapeutic strategies based on the principles of tissue engineering by self-assembly put forward the notion that functional regeneration can be achieved by utilising the inherent capacity of cells to create highly sophisticated supramolecular assemblies. However, in dilute ex vivo microenvironments, prolonged culture time is required to develop an extracellular matrix-rich implantable device. Herein, we assessed the influence of macromolecular crowding, a biophysical phenomenon that regulates intra- and extra-cellular activities in multicellular organisms, in human corneal fibroblast culture. In the presence of macromolecules, abundant extracellular matrix deposition was evidenced as fast as 48 h in culture, even at low serum concentration. Temperature responsive copolymers allowed the detachment of dense and cohesive supramolecularly assembled living substitutes within 6 days in culture. Morphological, histological, gene and protein analysis assays demonstrated maintenance of tissue-specific function. Macromolecular crowding opens new avenues for a more rational design in engineering of clinically relevant tissue modules in vitro.

  17. Atomic force microscopy applied to study macromolecular content of embedded biological material

    Energy Technology Data Exchange (ETDEWEB)

    Matsko, Nadejda B. [Electron Microscopy Centre, Institute of Applied Physics, HPM C 15.1, ETH-Hoenggerberg, CH-8093, Zurich (Switzerland)]. E-mail: matsko@iap.phys.ethz.ch

    2007-02-15

    We demonstrate that atomic force microscopy represents a powerful tool for the estimation of structural preservation of biological samples embedded in epoxy resin, in terms of their macromolecular distribution and architecture. The comparison of atomic force microscopy (AFM) and transmission electron microscopy (TEM) images of a biosample (Caenorhabditis elegans) prepared following to different types of freeze-substitution protocols (conventional OsO{sub 4} fixation, epoxy fixation) led to the conclusion that high TEM stainability of the sample results from a low macromolecular density of the cellular matrix. We propose a novel procedure aimed to obtain AFM and TEM images of the same particular organelle, which strongly facilitates AFM image interpretation and reveals new ultrastructural aspects (mainly protein arrangement) of a biosample in addition to TEM data.

  18. Extraction of cobalt ion from textile using a complexing macromolecular surfactant in supercritical carbon dioxide

    International Nuclear Information System (INIS)

    Chirat, Mathieu; Ribaut, Tiphaine; Clerc, Sebastien; Lacroix-Desmazes, Patrick; Charton, Frederic; Fournel, Bruno

    2013-01-01

    Cobalt ion under the form of cobalt nitrate is removed from a textile lab coat using supercritical carbon dioxide extraction. The process involves a macromolecular additive of well-defined architecture, acting both as a surfactant and a complexing agent. The extraction efficiency of cobalt reaches 66% when using a poly(1,1,2,2-tetrahydroperfluoro-decyl-acrylate-co-vinyl-benzylphosphonic diacid) gradient copolymer in the presence of water at 160 bar and 40 C. The synergy of the two additives, namely the copolymer and water which are useless if used separately, is pointed out. The potential of the supercritical carbon dioxide process using complexing macromolecular surfactant lies in the ability to modulate the complexing unit as a function of the metal as well as the architecture of the surface-active agent for applications ranging for instance from nuclear decontamination to the recovery of strategic metals. (authors)

  19. Clustering procedures for the optimal selection of data sets from multiple crystals in macromolecular crystallography

    Energy Technology Data Exchange (ETDEWEB)

    Foadi, James [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom); Imperial College, London SW7 2AZ (United Kingdom); Aller, Pierre [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom); Alguel, Yilmaz; Cameron, Alex [Imperial College, London SW7 2AZ (United Kingdom); Axford, Danny; Owen, Robin L. [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom); Armour, Wes [Oxford e-Research Centre (OeRC), Keble Road, Oxford OX1 3QG (United Kingdom); Waterman, David G. [Research Complex at Harwell (RCaH), Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0FA (United Kingdom); Iwata, So [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom); Imperial College, London SW7 2AZ (United Kingdom); Evans, Gwyndaf, E-mail: gwyndaf.evans@diamond.ac.uk [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom)

    2013-08-01

    A systematic approach to the scaling and merging of data from multiple crystals in macromolecular crystallography is introduced and explained. The availability of intense microbeam macromolecular crystallography beamlines at third-generation synchrotron sources has enabled data collection and structure solution from microcrystals of <10 µm in size. The increased likelihood of severe radiation damage where microcrystals or particularly sensitive crystals are used forces crystallographers to acquire large numbers of data sets from many crystals of the same protein structure. The associated analysis and merging of multi-crystal data is currently a manual and time-consuming step. Here, a computer program, BLEND, that has been written to assist with and automate many of the steps in this process is described. It is demonstrated how BLEND has successfully been used in the solution of a novel membrane protein.

  20. Pi sampling: a methodical and flexible approach to initial macromolecular crystallization screening

    International Nuclear Information System (INIS)

    Gorrec, Fabrice; Palmer, Colin M.; Lebon, Guillaume; Warne, Tony

    2011-01-01

    Pi sampling, derived from the incomplete factorial approach, is an effort to maximize the diversity of macromolecular crystallization conditions and to facilitate the preparation of 96-condition initial screens. The Pi sampling method is derived from the incomplete factorial approach to macromolecular crystallization screen design. The resulting ‘Pi screens’ have a modular distribution of a given set of up to 36 stock solutions. Maximally diverse conditions can be produced by taking into account the properties of the chemicals used in the formulation and the concentrations of the corresponding solutions. The Pi sampling method has been implemented in a web-based application that generates screen formulations and recipes. It is particularly adapted to screens consisting of 96 different conditions. The flexibility and efficiency of Pi sampling is demonstrated by the crystallization of soluble proteins and of an integral membrane-protein sample

  1. Macromolecular Engineering: New Routes Towards the Synthesis of Well-??Defined Polyethers/Polyesters Co/Terpolymers with Different Architectures

    KAUST Repository

    Alamri, Haleema

    2016-01-01

    Macromolecular engineering (as discussed in the first chapter) of homo/copolymers refers to the specific tailoring of these materials for achieving an easy and reproducible synthesis that results in precise molecular

  2. The Postgraduate Study of Macromolecular Sciences at the University of Zagreb (1971-1980)

    OpenAIRE

    Kunst, B.; Dezelic, D.; Veksli, Z.

    2008-01-01

    The postgraduate study of macromolecular sciences (PSMS) was established at the University of Zagreb in 1971 as a university study in the time of expressed interdisciplinary permeation of natural sciences - physics, chemistry and biology, and application of their achievements in technologicaldisciplines. PSMS was established by a group of prominent university professors from the schools of Science, Chemical Technology, Pharmacy and Medicine, as well as from the Institute of Biology. The study...

  3. The Postgraduate Study of Macromolecular Sciences at the University of Zagreb (1971– 1980)

    OpenAIRE

    Deželić, D.; Kunst, B.; Veksli, Zorica

    2008-01-01

    The postgraduate study of macromolecular sciences (PSMS) was established at the University of Zagreb in 1971 as a university study in the time of expressed interdisciplinary permeation of natural sciences - physics, chemistry and biology, and application of their achievements in technological disciplines. PSMS was established by a group of prominent university professors from the schools of Science, Chemical Technology, Pharmacy and Medicine, as well as from the Institute of Biology. The s...

  4. Measurement and Interpretation of Diffuse Scattering in X-Ray Diffraction for Macromolecular Crystallography

    Energy Technology Data Exchange (ETDEWEB)

    Wall, Michael E. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-10-16

    X-ray diffraction from macromolecular crystals includes both sharply peaked Bragg reflections and diffuse intensity between the peaks. The information in Bragg scattering reflects the mean electron density in the unit cells of the crystal. The diffuse scattering arises from correlations in the variations of electron density that may occur from one unit cell to another, and therefore contains information about collective motions in proteins.

  5. Fully automated data collection and processing system on macromolecular crystallography beamlines at the PF

    International Nuclear Information System (INIS)

    Yamada, Yusuke; Hiraki, Masahiko; Matsugaki, Naohiro; Chavas, Leonard M.G.; Igarashi, Noriyuki; Wakatsuki, Soichi

    2012-01-01

    Fully automated data collection and processing system has been developed on macromolecular crystallography beamlines at the Photon Factory. In this system, the sample exchange, centering and data collection are sequentially performed for all samples stored in the sample exchange system at a beamline without any manual operations. Data processing of collected data sets is also performed automatically. These results are stored into the database system, and users can monitor the progress and results of automated experiment via a Web browser. (author)

  6. Macromolecular shape and interactions in layer-by-layer assemblies within cylindrical nanopores.

    Science.gov (United States)

    Lazzara, Thomas D; Lau, K H Aaron; Knoll, Wolfgang; Janshoff, Andreas; Steinem, Claudia

    2012-01-01

    Layer-by-layer (LbL) deposition of polyelectrolytes and proteins within the cylindrical nanopores of anodic aluminum oxide (AAO) membranes was studied by optical waveguide spectroscopy (OWS). AAO has aligned cylindrical, nonintersecting pores with a defined pore diameter d(0) and functions as a planar optical waveguide so as to monitor, in situ, the LbL process by OWS. The LbL deposition of globular proteins, i.e., avidin and biotinylated bovine serum albumin was compared with that of linear polyelectrolytes (linear-PEs), both species being of similar molecular weight. LbL deposition within the cylindrical AAO geometry for different pore diameters (d(0) = 25-80 nm) for the various macromolecular species, showed that the multilayer film growth was inhibited at different maximum numbers of LbL steps (n(max)). The value of n(max) was greatest for linear-PEs, while proteins had a lower value. The cylindrical pore geometry imposes a physical limit to LbL growth such that n(max) is strongly dependent on the overall internal structure of the LbL film. For all macromolecular species, deposition was inhibited in native AAO, having pores of d(0) = 25-30 nm. Both, OWS and scanning electron microscopy showed that LbL growth in larger AAO pores (d(0) > 25-30 nm) became inhibited when approaching a pore diameter of d(eff,n_max) = 25-35 nm, a similar size to that of native AAO pores, with d(0) = 25-30 nm. For a reasonable estimation of d(eff,n_max), the actual volume occupied by a macromolecular assembly must be taken into consideration. The results clearly show that electrostatic LbL allowed for compact macromolecular layers, whereas proteins formed loosely packed multilayers.

  7. Tuning the properties of an anthracene-based PPE-PPV copolymer by fine variation of its macromolecular parameters

    Czech Academy of Sciences Publication Activity Database

    Tinti, F.; Sabir, F. K.; Gazzano, M.; Righi, S.; Ulbricht, C.; Usluer, Ö.; Pokorná, Veronika; Cimrová, Věra; Yohannes, T.; Egbe, D. A. M.; Camaioni, N.

    2013-01-01

    Roč. 3, č. 19 (2013), s. 6972-6980 ISSN 2046-2069 R&D Projects: GA ČR GAP106/12/0827; GA ČR(CZ) GA13-26542S Institutional support: RVO:61389013 Keywords : anthracene-containing PPE-PPV copolymer * macromolecular parameters * structural and transport properties Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.708, year: 2013

  8. Macromolecular diffusion in crowded media beyond the hard-sphere model.

    Science.gov (United States)

    Blanco, Pablo M; Garcés, Josep Lluís; Madurga, Sergio; Mas, Francesc

    2018-04-25

    The effect of macromolecular crowding on diffusion beyond the hard-core sphere model is studied. A new coarse-grained model is presented, the Chain Entanglement Softened Potential (CESP) model, which takes into account the macromolecular flexibility and chain entanglement. The CESP model uses a shoulder-shaped interaction potential that is implemented in the Brownian Dynamics (BD) computations. The interaction potential contains only one parameter associated with the chain entanglement energetic cost (Ur). The hydrodynamic interactions are included in the BD computations via Tokuyama mean-field equations. The model is used to analyze the diffusion of a streptavidin protein among different sized dextran obstacles. For this system, Ur is obtained by fitting the streptavidin experimental long-time diffusion coefficient Dlongversus the macromolecular concentration for D50 (indicating their molecular weight in kg mol-1) dextran obstacles. The obtained Dlong values show better quantitative agreement with experiments than those obtained with hard-core spheres. Moreover, once parametrized, the CESP model is also able to quantitatively predict Dlong and the anomalous exponent (α) for streptavidin diffusion among D10, D400 and D700 dextran obstacles. Dlong, the short-time diffusion coefficient (Dshort) and α are obtained from the BD simulations by using a new empirical expression, able to describe the full temporal evolution of the diffusion coefficient.

  9. Homogenization Theory for the Prediction of Obstructed Solute Diffusivity in Macromolecular Solutions.

    Science.gov (United States)

    Donovan, Preston; Chehreghanianzabi, Yasaman; Rathinam, Muruhan; Zustiak, Silviya Petrova

    2016-01-01

    The study of diffusion in macromolecular solutions is important in many biomedical applications such as separations, drug delivery, and cell encapsulation, and key for many biological processes such as protein assembly and interstitial transport. Not surprisingly, multiple models for the a-priori prediction of diffusion in macromolecular environments have been proposed. However, most models include parameters that are not readily measurable, are specific to the polymer-solute-solvent system, or are fitted and do not have a physical meaning. Here, for the first time, we develop a homogenization theory framework for the prediction of effective solute diffusivity in macromolecular environments based on physical parameters that are easily measurable and not specific to the macromolecule-solute-solvent system. Homogenization theory is useful for situations where knowledge of fine-scale parameters is used to predict bulk system behavior. As a first approximation, we focus on a model where the solute is subjected to obstructed diffusion via stationary spherical obstacles. We find that the homogenization theory results agree well with computationally more expensive Monte Carlo simulations. Moreover, the homogenization theory agrees with effective diffusivities of a solute in dilute and semi-dilute polymer solutions measured using fluorescence correlation spectroscopy. Lastly, we provide a mathematical formula for the effective diffusivity in terms of a non-dimensional and easily measurable geometric system parameter.

  10. Principles and Overview of Sampling Methods for Modeling Macromolecular Structure and Dynamics.

    Science.gov (United States)

    Maximova, Tatiana; Moffatt, Ryan; Ma, Buyong; Nussinov, Ruth; Shehu, Amarda

    2016-04-01

    Investigation of macromolecular structure and dynamics is fundamental to understanding how macromolecules carry out their functions in the cell. Significant advances have been made toward this end in silico, with a growing number of computational methods proposed yearly to study and simulate various aspects of macromolecular structure and dynamics. This review aims to provide an overview of recent advances, focusing primarily on methods proposed for exploring the structure space of macromolecules in isolation and in assemblies for the purpose of characterizing equilibrium structure and dynamics. In addition to surveying recent applications that showcase current capabilities of computational methods, this review highlights state-of-the-art algorithmic techniques proposed to overcome challenges posed in silico by the disparate spatial and time scales accessed by dynamic macromolecules. This review is not meant to be exhaustive, as such an endeavor is impossible, but rather aims to balance breadth and depth of strategies for modeling macromolecular structure and dynamics for a broad audience of novices and experts.

  11. In Vitro and In Vivo Evaluation of Microparticulate Drug Delivery Systems Composed of Macromolecular Prodrugs

    Directory of Open Access Journals (Sweden)

    Yoshiharu Machida

    2008-08-01

    Full Text Available Macromolecular prodrugs are very useful systems for achieving controlled drug release and drug targeting. In particular, various macromolecule-antitumor drug conjugates enhance the effectiveness and improve the toxic side effects. Also, polymeric micro- and nanoparticles have been actively examined and their in vivo behaviors elucidated, and it has been realized that their particle characteristics are very useful to control drug behavior. Recently, researches based on the combination of the concepts of macromolecular prodrugs and micro- or nanoparticles have been reported, although they are limited. Macromolecular prodrugs enable drugs to be released at a certain controlled release rate based on the features of the macromolecule-drug linkage. Micro- and nanoparticles can control in vivo behavior based on their size, surface charge and surface structure. These merits are expected for systems produced by the combination of each concept. In this review, several micro- or nanoparticles composed of macromolecule-drug conjugates are described for their preparation, in vitro properties and/or in vivo behavior.

  12. Homogenization Theory for the Prediction of Obstructed Solute Diffusivity in Macromolecular Solutions.

    Directory of Open Access Journals (Sweden)

    Preston Donovan

    Full Text Available The study of diffusion in macromolecular solutions is important in many biomedical applications such as separations, drug delivery, and cell encapsulation, and key for many biological processes such as protein assembly and interstitial transport. Not surprisingly, multiple models for the a-priori prediction of diffusion in macromolecular environments have been proposed. However, most models include parameters that are not readily measurable, are specific to the polymer-solute-solvent system, or are fitted and do not have a physical meaning. Here, for the first time, we develop a homogenization theory framework for the prediction of effective solute diffusivity in macromolecular environments based on physical parameters that are easily measurable and not specific to the macromolecule-solute-solvent system. Homogenization theory is useful for situations where knowledge of fine-scale parameters is used to predict bulk system behavior. As a first approximation, we focus on a model where the solute is subjected to obstructed diffusion via stationary spherical obstacles. We find that the homogenization theory results agree well with computationally more expensive Monte Carlo simulations. Moreover, the homogenization theory agrees with effective diffusivities of a solute in dilute and semi-dilute polymer solutions measured using fluorescence correlation spectroscopy. Lastly, we provide a mathematical formula for the effective diffusivity in terms of a non-dimensional and easily measurable geometric system parameter.

  13. MxCuBE: a synchrotron beamline control environment customized for macromolecular crystallography experiments

    International Nuclear Information System (INIS)

    Gabadinho, José; Beteva, Antonia; Guijarro, Matias; Rey-Bakaikoa, Vicente; Spruce, Darren

    2010-01-01

    MxCuBE is a beamline control environment optimized for the needs of macromolecular crystallography. This paper describes the design of the software and the features that MxCuBE currently provides. The design and features of a beamline control software system for macromolecular crystallography (MX) experiments developed at the European Synchrotron Radiation Facility (ESRF) are described. This system, MxCuBE, allows users to easily and simply interact with beamline hardware components and provides automated routines for common tasks in the operation of a synchrotron beamline dedicated to experiments in MX. Additional functionality is provided through intuitive interfaces that enable the assessment of the diffraction characteristics of samples, experiment planning, automatic data collection and the on-line collection and analysis of X-ray emission spectra. The software can be run in a tandem client-server mode that allows for remote control and relevant experimental parameters and results are automatically logged in a relational database, ISPyB. MxCuBE is modular, flexible and extensible and is currently deployed on eight macromolecular crystallography beamlines at the ESRF. Additionally, the software is installed at MAX-lab beamline I911-3 and at BESSY beamline BL14.1

  14. A smooth and differentiable bulk-solvent model for macromolecular diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Fenn, T. D. [Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford, California (United States); Schnieders, M. J. [Department of Chemistry, Stanford, California (United States); Brunger, A. T., E-mail: brunger@stanford.edu [Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford, California (United States); Departments of Neurology and Neurological Sciences, Structural Biology and Photon Science, Stanford, California (United States)

    2010-09-01

    A new method for modeling the bulk solvent in macromolecular diffraction data based on Babinet’s principle is presented. The proposed models offer the advantage of differentiability with respect to atomic coordinates. Inclusion of low-resolution data in macromolecular crystallography requires a model for the bulk solvent. Previous methods have used a binary mask to accomplish this, which has proven to be very effective, but the mask is discontinuous at the solute–solvent boundary (i.e. the mask value jumps from zero to one) and is not differentiable with respect to atomic parameters. Here, two algorithms are introduced for computing bulk-solvent models using either a polynomial switch or a smoothly thresholded product of Gaussians, and both models are shown to be efficient and differentiable with respect to atomic coordinates. These alternative bulk-solvent models offer algorithmic improvements, while showing similar agreement of the model with the observed amplitudes relative to the binary model as monitored using R, R{sub free} and differences between experimental and model phases. As with the standard solvent models, the alternative models improve the agreement primarily with lower resolution (>6 Å) data versus no bulk solvent. The models are easily implemented into crystallographic software packages and can be used as a general method for bulk-solvent correction in macromolecular crystallography.

  15. A smooth and differentiable bulk-solvent model for macromolecular diffraction

    International Nuclear Information System (INIS)

    Fenn, T. D.; Schnieders, M. J.; Brunger, A. T.

    2010-01-01

    A new method for modeling the bulk solvent in macromolecular diffraction data based on Babinet’s principle is presented. The proposed models offer the advantage of differentiability with respect to atomic coordinates. Inclusion of low-resolution data in macromolecular crystallography requires a model for the bulk solvent. Previous methods have used a binary mask to accomplish this, which has proven to be very effective, but the mask is discontinuous at the solute–solvent boundary (i.e. the mask value jumps from zero to one) and is not differentiable with respect to atomic parameters. Here, two algorithms are introduced for computing bulk-solvent models using either a polynomial switch or a smoothly thresholded product of Gaussians, and both models are shown to be efficient and differentiable with respect to atomic coordinates. These alternative bulk-solvent models offer algorithmic improvements, while showing similar agreement of the model with the observed amplitudes relative to the binary model as monitored using R, R free and differences between experimental and model phases. As with the standard solvent models, the alternative models improve the agreement primarily with lower resolution (>6 Å) data versus no bulk solvent. The models are easily implemented into crystallographic software packages and can be used as a general method for bulk-solvent correction in macromolecular crystallography

  16. Properties of sericin films crosslinking with dimethylolurea

    International Nuclear Information System (INIS)

    Turbiani, Franciele R.B.; Stroher, Gylles Ricardo; Tomadon Junior, Jose; Seixas, Fernanda L.; Stroher, Gylles Ricardo; Gimenes, Marcelino L.

    2011-01-01

    Sericin is a natural silk protein which is removed from silk in a process called degumming. Thus, finding a use for the extracted sericin as a bio polymer film will create added value product which will benefit both the economy and society. The films were manufactured with silk sericin, using different dimethylolurea (DMU) concentrations as cross-linking agent and glycerol as plasticizer. Sericin films produced by crosslinking method were light yellow, homogeneous, transparent and visually attractive. The average film thickness was 0.10 ± 0.02 mm. The bio films show low water solubility (up to 30% of total dry mass), good tension strength and high elongation ability. The water vapor permeability is moderate, typical of highly hydrophilic films. Structural transformations in silk sericin films were analyzed using Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy and X-ray diffraction. This resulted in aggregated β-sheet structure (peak at 1616 cm-1 in the amide I absorption) by FTIR studies and increasing the DMU concentration in film decreased the peak intensity at 2θ = 20 degree. Sericin-based film properties are dependent on components used to form film, which can used to tailor the desired film flexibility and minimize permeability of films. (author)

  17. Properties of sericin films crosslinking with dimethylolurea

    Energy Technology Data Exchange (ETDEWEB)

    Turbiani, Franciele R.B.; Stroher, Gylles Ricardo [Federal Technology University - UTFPR, Campus Apucarana, PR (Brazil); Tomadon, Junior, Jose; Seixas, Fernanda L; Stroher, Gylles Ricardo; Gimenes, Marcelino L., E-mail: francieler@utfpr.edu.br [State University of Maringa. UEM, Campus Maringa, PR (Brazil)

    2011-07-01

    Sericin is a natural silk protein which is removed from silk in a process called degumming. Thus, finding a use for the extracted sericin as a bio polymer film will create added value product which will benefit both the economy and society. The films were manufactured with silk sericin, using different dimethylolurea (DMU) concentrations as cross-linking agent and glycerol as plasticizer. Sericin films produced by crosslinking method were light yellow, homogeneous, transparent and visually attractive. The average film thickness was 0.10 {+-} 0.02 mm. The bio films show low water solubility (up to 30% of total dry mass), good tension strength and high elongation ability. The water vapor permeability is moderate, typical of highly hydrophilic films. Structural transformations in silk sericin films were analyzed using Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy and X-ray diffraction. This resulted in aggregated {beta}-sheet structure (peak at 1616 cm-1 in the amide I absorption) by FTIR studies and increasing the DMU concentration in film decreased the peak intensity at 2{theta} = 20 degree. Sericin-based film properties are dependent on components used to form film, which can used to tailor the desired film flexibility and minimize permeability of films. (author)

  18. Gaussian-Based Smooth Dielectric Function: A Surface-Free Approach for Modeling Macromolecular Binding in Solvents

    Directory of Open Access Journals (Sweden)

    Arghya Chakravorty

    2018-03-01

    Full Text Available Conventional modeling techniques to model macromolecular solvation and its effect on binding in the framework of Poisson-Boltzmann based implicit solvent models make use of a geometrically defined surface to depict the separation of macromolecular interior (low dielectric constant from the solvent phase (high dielectric constant. Though this simplification saves time and computational resources without significantly compromising the accuracy of free energy calculations, it bypasses some of the key physio-chemical properties of the solute-solvent interface, e.g., the altered flexibility of water molecules and that of side chains at the interface, which results in dielectric properties different from both bulk water and macromolecular interior, respectively. Here we present a Gaussian-based smooth dielectric model, an inhomogeneous dielectric distribution model that mimics the effect of macromolecular flexibility and captures the altered properties of surface bound water molecules. Thus, the model delivers a smooth transition of dielectric properties from the macromolecular interior to the solvent phase, eliminating any unphysical surface separating the two phases. Using various examples of macromolecular binding, we demonstrate its utility and illustrate the comparison with the conventional 2-dielectric model. We also showcase some additional abilities of this model, viz. to account for the effect of electrolytes in the solution and to render the distribution profile of water across a lipid membrane.

  19. The effect of macromolecular crowding on the electrostatic component of barnase-barstar binding: a computational, implicit solvent-based study.

    Directory of Open Access Journals (Sweden)

    Helena W Qi

    Full Text Available Macromolecular crowding within the cell can impact both protein folding and binding. Earlier models of cellular crowding focused on the excluded volume, entropic effect of crowding agents, which generally favors compact protein states. Recently, other effects of crowding have been explored, including enthalpically-related crowder-protein interactions and changes in solvation properties. In this work, we explore the effects of macromolecular crowding on the electrostatic desolvation and solvent-screened interaction components of protein-protein binding. Our simple model enables us to focus exclusively on the electrostatic effects of water depletion on protein binding due to crowding, providing us with the ability to systematically analyze and quantify these potentially intuitive effects. We use the barnase-barstar complex as a model system and randomly placed, uncharged spheres within implicit solvent to model crowding in an aqueous environment. On average, we find that the desolvation free energy penalties incurred by partners upon binding are lowered in a crowded environment and solvent-screened interactions are amplified. At a constant crowder density (fraction of total available volume occupied by crowders, this effect generally increases as the radius of model crowders decreases, but the strength and nature of this trend can depend on the water probe radius used to generate the molecular surface in the continuum model. In general, there is huge variation in desolvation penalties as a function of the random crowder positions. Results with explicit model crowders can be qualitatively similar to those using a lowered "effective" solvent dielectric to account for crowding, although the "best" effective dielectric constant will likely depend on multiple system properties. Taken together, this work systematically demonstrates, quantifies, and analyzes qualitative intuition-based insights into the effects of water depletion due to crowding on the

  20. Cross-linked polyelectrolyte multilayers for marine antifouling applications

    NARCIS (Netherlands)

    Zhu, X.; Janczewski, D.; Lee, S.S.C.; Teo, S.L-M.; Vancso, Gyula J.

    2013-01-01

    A polyionic multilayer film was fabricated by layer-by-layer (LbL) sequential deposition followed by cross-linking under mild conditions on a substrate surface to inhibit marine fouling. A novel polyanion, featuring methyl ester groups for an easy cross-linking was used as a generic solution for

  1. Characterization of Aldehyde Crosslinked Kenaf Regenerated Cellulose Film

    Directory of Open Access Journals (Sweden)

    Hatika Kaco

    2015-08-01

    Full Text Available Regenerated cellulose film with better mechanical properties was successfully produced by introducing aldehyde crosslinker during the regeneration process. The cellulose source material was derived from kenaf core powder and dissolved in LiOH/urea solvent at −13 °C to form a cellulose solution. The cellulose solution was cast and coagulated in a crosslinker bath at different percentages of glutaraldehyde (GA and glyoxal (GX to form a regenerated cellulose film. According to Fourier transform infrared spectroscopy (FTIR spectra, the hydroxyl group of the cellulose was reduced, reducing the percentage of swelling as the percentage of crosslinker was increased. X-ray diffraction (XRD patterns showed that the crystallinity index of the crosslinked film was decreased. The pore size of the films decreased as the percentage of crosslinker was increased, resulting in decreased film transparency. The pore volume and percentage of swelling in water of the films also increased with decreases in the pore size as the percentage of crosslinker was increased. The tensile strengths of the GA- and GX-crosslinked films increased by 20 and 15% with the addition of 20% of each crosslinker, respectively.

  2. Hydrogels Prepared from Cross-Linked Nanofibrillated Cellulose

    Science.gov (United States)

    Sandeep S. Nair; J.Y. Zhu; Yulin Deng; Arthur J. Ragauskas

    2014-01-01

    Nanocomposite hydrogels were developed by cross-linking nanofibrillated cellulose with poly(methyl vinyl ether-co-maleic acid) and polyethylene glycol. The cross-linked hydrogels showed enhanced water absorption and gel content with the addition of nanocellulose. In addition, the thermal stability, mechanical strength, and modulus increased with an increase in the...

  3. Fabrication of homobifunctional crosslinker stabilized collagen for biomedical application

    International Nuclear Information System (INIS)

    Lakra, Rachita; Kiran, Manikantan Syamala; Sai, Korrapati Purna

    2015-01-01

    Collagen biopolymer has found widespread application in the field of tissue engineering owing to its excellent tissue compatibility and negligible immunogenicity. Mechanical strength and enzymatic degradation of the collagen necessitates the physical and chemical strength enhancement. One such attempt deals with the understanding of crosslinking behaviour of EGS (ethylene glycol-bis (succinic acid N-hydroxysuccinimide ester)) with collagen to improve the physico-chemical properties. The incorporation of a crosslinker during fibril formation enhanced the thermal and mechanical stability of collagen. EGS crosslinked collagen films exhibited higher denaturation temperature (T d ) and the residue left after thermogravimetric analysis was about 16  ±  5.2%. Mechanical properties determined by uniaxial tensile tests showed a threefold increase in tensile strength and Young’s modulus at higher concentration (100 μM). Water uptake capacity reduced up to a moderate extent upon crosslinking which is essential for the transport of nutrients to the cells. Cell viability was found to be 100% upon treatment with 100 μM EGS whereas only 30% viability could be observed with glutaraldehyde. Rheological studies of crosslinked collagen showed an increase in shear stress and shear viscosity at 37 °C. Crosslinking with EGS resulted in the formation of a uniform fibrillar network. Trinitrobenzene sulfonate (TNBS) assay confirmed that EGS crosslinked collagen by forming a covalent interaction with ε-amino acids of collagen. The homobifunctional crosslinker used in this study enhanced the effectiveness of collagen as a biomaterial for biomedical application. (paper)

  4. Nuclear magnetic resonance structure investigations on crosslinked polyesters

    International Nuclear Information System (INIS)

    Grobelny, J.

    1999-01-01

    Styrene-crosslinked mixed polyesters derived from maleic anhydride, 2,2-di(4-hydroxypropoxyphenyl)propane, oligo(propylene oxide) and 1,2-propylene glycol were investigated by high-resolution solid-state 13 C NMR spectroscopy. The structural modifications accompanying crosslinking were characterized in terms of spin-lattice relaxation times as a function of unsaturated polyester composition. Copolymerization and crosslinking effects were individually evaluated and the latter effect was related to variations in crosslinking density associated with the chemical structure of the unsaturated prepolymer. As the crosslinking effect is suppressed, the mechanical properties undergo expected changes, e.g., impact strength is increased and modulus of elasticity in tension is decreased. (author)

  5. Recent advances in corneal collagen cross-linking

    Directory of Open Access Journals (Sweden)

    Gitansha Shreyas Sachdev

    2017-01-01

    Full Text Available Corneal collagen cross-linking has become the preferred modality of treatment for corneal ectasia since its inception in late 1990s. Numerous studies have demonstrated the safety and efficacy of the conventional protocol. Our understanding of the cross-linking process is ever evolving, with its wide implications in the form of accelerated and pulsed protocols. Newer advancements in technology include various riboflavin formulations and the ability to deliver higher fluence protocols with customised irradiation patterns. A greater degree of customisation is likely the path forward, which will aim at achieving refractive improvements along with disease stability. The use of cross-linking for myopic correction is another avenue under exploration. Combination of half fluence cross-linking with refractive correction for high errors to prevent post LASIK regression is gaining interest. This review aims to highlight the various advancements in the cross-linking technology and its clinical applications.

  6. Carboxymethylcellulose hydrogel crosslinked with citric acid for biomedical application

    International Nuclear Information System (INIS)

    Capanema, Nadia S.V.; Mansur, Alexandra A.P.; Mansur, Herman S.; Universidade Federal de Minas Gerais

    2016-01-01

    The carboxymethylcellulose (CMCel) has been extensively used in order application as flexible polymer membrane. Biopolymers crosslinked have been studied to optimize their performance in biomedical applications. In this work, CMCel films with a degree of substitution (DS = 0.77) were prepared by evaporation of solvent and crosslinked with different concentrations of citric acid (CA). The synthesized CMCel was characterized by Infrared Spectroscopy by Fourier Transform X-ray spectroscopy (FTIR), and morphology assessed by scanning electron microscopy (SEM). Morphological analysis performed using the SEM indicated the crosslinked CMCel and not crosslinked with a very smooth and uniform appearance. The FTIR results indicated the modification of existing bands and appearance of a new band 1715 cm"-"1 suggesting that there has been change in the structure of the crosslinked CMCel. (author)

  7. Radiation-induced crosslinking of poly(vinylidene fluoride)

    International Nuclear Information System (INIS)

    Makuuchi, Keizo

    1977-07-01

    The factors influencing radiation-induced crosslinking efficiency of poly(vinylidene fluoride) (PVdF) have been studied. Results of the basic research on irradiation conditions (dose rate and atmosphere) and initial physical properties of PVdF (structure of molecular chain and molecular mobility of chain segment) showed that crosslinking efficiency is raised in irradiation at high temperature above 50 0 C under vacuum in the presence of an absorbent for the evolved hydrogen fluoride. The crosslinking reaction is also accelerated with irregular molecular structure such as head-to-head bond in main chain. High crosslinking efficiency is obtained by addition of a polyfunctional monomer having good solubility with PVdF. Mechanical properties of PVdF, the strength at high temperature near the melting point in particular, are improved by crosslinking in the presence of a polyfunctional monomer. (auth.)

  8. Covalent DNA-protein crosslinking occurs after hyperthermia and radiation

    International Nuclear Information System (INIS)

    Cress, A.E.; Bowden, G.T.

    1983-01-01

    Covalent DNA-protein crosslinks occur in exponentially growing mouse leukemia cells (L1210) after exposure to ionizing radiation. The amount of DNA-protein crosslinks as measured by a filter binding assay is dose dependent upon x irradiation. Although hyperthermia and radiation in combination are synergistic with respect to cell lethality, the combination does not result in an increase of DNA-protein crosslinks when assayed immediately following treatments. Hyperthermia (43 0 C/15 min) given prior to radiation dose not alter the radiation dose dependency of the amount of initial crosslinking. In addition, the amount of DNA-protein crosslinking produced by heat plus radiation is independent of the length of heating the cells at 43 0 C. The DNA-protein crosslinks produced y 50-Gy x ray alone are removed after 2 hr at 37 0 C. However, if hyperthermia (43 0 C/15 min) is given prior to 100-Gy x ray, the removal of DNA-protein crosslinks is delayed until 4.0 hr after radiation. Phospho-serine and phospho-threonine bonds are not produced with either radiation or the combination of hyperthermia plus radiation as judged by the resistance of the bonds to guanidine hydrochloride. However, hyperthermia plus radiation causes an increase in phosphate to nitrogen type bonding. These results show that radiation alone causes covalent DNA-protein crosslinks. Hyperthermia in combination with radiation does not increase the total amount of the crosslinks but delays the removal of the crosslinks and alters the distribution of the types of chemical bonding

  9. Gamma irradiation Effect on the Non-Crosslinked and Crosslinked Poly(vinyl alcohol) Films

    International Nuclear Information System (INIS)

    El-Sawy, N.M.; El-Arnaouty, M.B.; Abdel Ghaffar, A.M.

    2008-01-01

    The non-crosslinked and crosslinked poly(vinyl alcohol) (PVA) films were prepared by the cast method then irradiated with gamma rays for various doses up to 300 kGy. The structure and characterization of PVA were determined by using Infrared spectroscopy (FTIR), ultraviolet spectroscopy (UV). Swelling behaviour was also investigated. Mechanical properties have been examined with respect to the absorbed dose. The color of the films changed to yellowish-white after irradiation. Additional changes were observed using FTIR analysis on the degradation products demonstrated that the radiolysis of PVA was initiated by liberation of H and OH groups leading to scission of the main chains and formation of carbonyl and double bond groups. Thermogravimetric analysis (TGA) was performed

  10. Radiation crosslinked materials with antithrombotical properties

    International Nuclear Information System (INIS)

    Schunk, W.; Kloecking, H.P.; Merkmann, G.; Giessmann, C.; Knoll, H.; Borgmann, S.

    1991-01-01

    Described is a flexible drainage tube of good tissue tolerance developed for the postoperative continuous withdrawal of secretions from wounds which - owing to the addition of an active ingredient in sustained release dosage form (pentosanpolysulfate stored in the molecular sieve) - inhibits or considerably delays clogging as a result of coagulation processes. The tube is made of a mixture of natural or silicone rubbers and 4% coagulation inhibitor that is extruded onto a metal mandrel, crosslinked using electron rays (100 kGy, 20 s) and simultaneously sterilised. The mandrel is subsequently removed. In vitro trials (using blood plasm for open flow systems and blood for circulatory flow systems) provided evidence in confirmation of a continuous regular release of active ingredient that inhibited coagulation processes over prolonged periods of time. (orig.) [de

  11. Corneal collagen crosslinking and pigment dispersion syndrome.

    Science.gov (United States)

    LaHood, Benjamin R; Moore, Sacha

    2017-03-01

    We describe the case of a keratoconus patient with pigment dispersion syndrome (PDS) who was treated for progressive corneal ectasia with corneal collagen crosslinking (CXL). Pigment dispersion syndrome has been shown to have associated morphologic changes of the corneal endothelium. Corneal CXL has the potential to cause toxicity to the corneal endothelium, and adjacent pigment might increase the likelihood of damage. In this case, the presence of PDS had no detrimental effect on the outcome of treatment, and no complications were observed at 12 months follow-up, indicating that it may be safe to perform corneal CXL in the setting of PDS. This is an important observation as the number of indications for corneal CXL grows. Copyright © 2017 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  12. In vivo biocompatibility of carbodiimide-crosslinked collagen matrices : Effects of crosslink density, heparin immobilization, and bFGF loading

    NARCIS (Netherlands)

    van Wachem, PB; Plantinga, JA; Wissink, MJB; Poot, AA; Engbers, GHM; Beugeling, T; van Aken, WG; Feijen, J; van Luyn, MJA

    2001-01-01

    Collagen matrices, crosslinked using N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide (E) and N-hydroxvsuccinimide (N), were previously developed as a substrate for endothelial cell seeding of small-diameter vascular grafts. In the present study, the biocompatibility of various EN-crosslinked collagen

  13. Crosslinking of epoxy-polysiloxane system by reactive blending

    Czech Academy of Sciences Publication Activity Database

    Gonzales, M.; Kadlec, Petr; Štěpánek, Petr; Strachota, Adam; Matějka, Libor

    2004-01-01

    Roč. 45, č. 16 (2004), s. 5533-5541 ISSN 0032-3861 R&D Projects: GA AV ČR IAA4050008 Keywords : reactive blending * siloxane network * epoxy network Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.433, year: 2004

  14. Physical crosslinking effects in alpha,omega-dihydroxy terminated polybutadienes

    Czech Academy of Sciences Publication Activity Database

    Krakovský, I.; Hanyková, L.; Trchová, Miroslava; Baldrian, Josef; Wübbenhorst, M.

    2007-01-01

    Roč. 48, č. 7 (2007), s. 2079-2086 ISSN 0032-3861 Institutional research plan: CEZ:AV0Z40500505 Keywords : hydrogen bonding * glass transition * dielectric relaxation Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.065, year: 2007

  15. The Modification of PVDF Membrane via Crosslinking with Chitosan and Glutaraldehyde as the Crosslinking Agent

    OpenAIRE

    Silitonga, Romaya Sitha; Widiastuti, Nurul; Jaafar, Juhana; Ismail, Ahmad Fauzi; Abidin, Muhammad Nidzhom Zainol; Azelee, Ihsan Wan; Naidu, Mahesan

    2018-01-01

    Poly(vinylidene fluoride) (PVDF) has outstanding properties such as high thermal stability, resistance to acid solvents and good mechanical strength. Due to its properties, PVDF is widely used as a membrane matrix. However, PVDF membrane is hydrophobic properties, so as for specific applications, the surface of membrane needs to be modified to become hydrophilic. This research aims to modify PVDF membrane surface with chitosan and glutaraldehyde as a crosslinker agent. The FTIR spectra showed...

  16. Stress-Strain Relation of Tire Rubber Consist of Entangled Polymers, Fillers and Crosslink

    Science.gov (United States)

    Hagita, Katsumi; Bito, Y.; Minagawa, Y.; Omiya, M.; Morita, H.; Doi, M.; Takano, H.

    2009-03-01

    We presented a preliminary result of large scale coarse-grained Molecular Dynamics simulation of filled polymer melts with Sulfur-crosslink under an uni-axial deformation by using the Kremer-Grest Model. The size of simulation box under periodic boundary conditions (PBC) is set to about 66nm to consider length of entangled polymer chains, size and structure of fillers, and non-uniform distribution of crosslink. We put 640 polymer chains of 1024 particles and 32 fillers into the PBC box. Each filler consists of 1280 particles of the C1280 fullerene structure. A repulsive force from the center of the filler is applied to the particles. Here, the particles of the fillers are chosen to be the same as the particles of the polymers and the diameter of the filler is about 15nm. The distribution of the fillers used in this simulation is provided by the result of 2d pattern RMC analysis for 2D-USAXS experiments at SPring-8. Sulfur crosslink are randomly distributed in the system. It is found that stress-strain curves estimated by applying a certain uni-axial deformation to the system in simulations are in good agreement with those in experiments. It is successful to show difference on the S-S curve between existence / absence of fillers and qualitative dependence of attractive force between polymer and filler.

  17. Characterization of the degree of cross-linking in radiation cross-linked low and high density polyethylenes

    International Nuclear Information System (INIS)

    Posselt, K.; Haedrich, W.

    1986-01-01

    In practice the cross-linking of irradiated polyethylene is mostly characterized by solubility and thermomechanical data. The irradiation of samples of a LDPE and a HDPE yields very different gel-dose curves. But for a quantitative comparison the complicated connection between the gel values and the corresponding densities of cross-links, especially the dependence on the initial molecular size distribution, has to take into consideration. The analysis of the solubility data according to the statistical theory of cross-linking developed by Inokuti and Saito shows that at equal doses in both investigated PE types in spite of the different gel values nearly the same densities of cross-links are present. That result is confirmed by the densities of cross-links determined from stress-strain measurements at 423 K. (author)

  18. Multilayer composite membranes for gas separation based on crosslinked PTMSP gutter layer and partially crosslinked Matrimid R 5218 selective layer

    Czech Academy of Sciences Publication Activity Database

    Peter, Jakub; Peinemann, K.; V.

    2009-01-01

    Roč. 340, 1-2 (2009), s. 62-72 ISSN 0376-7388 Grant - others:Marie Curie fellowship(XE) HPMT-CT-2001-00220 Institutional research plan: CEZ:AV0Z40500505 Keywords : composite membrane * gas separation * PTMSP * Matrimid Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.203, year: 2009

  19. Moisture curable toughened poly(lactide utilizing vinyltrimethoxysilane based crosslinks

    Directory of Open Access Journals (Sweden)

    J. Schneider

    2016-10-01

    Full Text Available Vinyltrimethoxysilane (VTMOS was grafted on to the backbone of poly(lactide (PLA through a free radical grafting reaction using reactive extrusion (REX processing. The methoxy groups of the silane provide the modified PLA sites for crosslinking through a moisture induced pathway. VTMOS grafting efficiencies of up to 90% were obtained. The newly created methoxy functionality of the modified PLA readily undergoes hydrolysis and condensation forming siloxane crosslinks in the material. Crosslinking with VTMOS exhibited improved modulus, strength, and impact toughness while showing a decrease in ductility. Incorporating silanol-terminated poly(dimethylsiloxane (OH-PDMS resulted in the formation of longer siloxane crosslinks. These samples showed an increase in modulus and impact toughness due to the crosslinking, while the longer siloxane linkages resulted in improved ductility and tensile toughness. This is unusual for polymers toughened through crosslinking reactions. Scanning Electron Microscopy (SEM of the fractured surfaces showed the presence of these elongated siloxane crosslinks. This enhanced ability for the modified PLA to deform and absorb energy results in the increase in both impact and tensile toughness.

  20. Repair of DNA-polypeptide crosslinks by human excision nuclease

    Science.gov (United States)

    Reardon, Joyce T.; Sancar, Aziz

    2006-03-01

    DNA-protein crosslinks are relatively common DNA lesions that form during the physiological processing of DNA by replication and recombination proteins, by side reactions of base excision repair enzymes, and by cellular exposure to bifunctional DNA-damaging agents such as platinum compounds. The mechanism by which pathological DNA-protein crosslinks are repaired in humans is not known. In this study, we investigated the mechanism of recognition and repair of protein-DNA and oligopeptide-DNA crosslinks by the human excision nuclease. Under our assay conditions, the human nucleotide excision repair system did not remove a 16-kDa protein crosslinked to DNA at a detectable level. However, 4- and 12-aa-long oligopeptides crosslinked to the DNA backbone were recognized by some of the damage recognition factors of the human excision nuclease with moderate selectivity and were excised from DNA at relatively efficient rates. Our data suggest that, if coupled with proteolytic degradation of the crosslinked protein, the human excision nuclease may be the major enzyme system for eliminating protein-DNA crosslinks from the genome. damage recognition | nucleotide excision repair

  1. Development of new materials by utilizing radiation crosslinking

    International Nuclear Information System (INIS)

    Ueno, Keiji; Uda, Yujiro; Suzuki, Shizuo

    1989-01-01

    About 30 years have elapsed since the cables by electron beam crosslinking were developed as the first industrial utilization of radiation in Japan. At present about 200 electron beam accelerators are used industrially in Japan, and cable industry ranks at the top, followed by foaming polyethylene and curing, and the preliminary vulcanization of tires. The effect of these irradiations is the reforming of polymers by radiation crosslinking. In cables, the heat resistance and chemical resistance of insulators are improved by radiation crosslinking. By applying radiation crosslinking to polyurethane elastomer, its weakest point, waterproof property, was improved. Moreover, by using this crosslinked polyurethane elastomer for cable coating, the reliability of the sensor cables for brake system was able to be remarkably improved. As another new application of radiation crosslinking process, the improvement of the heat resistance of engineering plasties was examined. The structure of radiation crosslinked urethane elastomer cables, their endurance in hot water and oil, and the life, and the characteristics of sensor cables are reported. Multi-functional monomers, the molecular structure, and the various characteristics of engineering plastics are described. (K.I.)

  2. Manufacture of polyethylene foam by electron beam cross-linking

    International Nuclear Information System (INIS)

    Tamai, Isamu

    1976-01-01

    The manufacturing process of polyethylene foam, comparison between electron beam cross-linking process and chemical cross-linking process, the electron beam irradiation technique for continuous sheets, the characteristics and uses of polyethylene foam are reviewed. The pore diameter can be controlled by selecting the dose rate, because there is strong relationship between the pore diameter and the dose rate. As the dose if higher, the foam becomes finer. The electron accelerators having large capacity show the lowest cost as the radiation source, and are applicable industrially. If the production capacity exceeds about 200 tons per month, the costs of electron beam irradiation process may be more advantageous than that of chemical process according to the circumstances. It is difficult to obtain the uniform distribution of absorption dose in the direction of thickness. General characteristics of cross-linked polyethylene foam are listed. The special feature of electron beam process is that the degree of cross-linking can be controlled arbitrarily before foaming. The products obtained by the electron beam cross-linking process have finer foams and smoother surfaces than those obtained by the chemical process, because the separation of the decomposition of foaming agents from that of cross-linking agents in the chemical cross-linking is difficult. (Iwakiri, K.)

  3. Mechanism of melphalan crosslink enhancement by misonidazole pretreatment

    International Nuclear Information System (INIS)

    Taylor, Y.C.; Sawyer, J.M.; Hsu, B.; Brown, J.M.

    1984-01-01

    Sensitization of Chinese hamster ovary cells to melphalan (L-PAM) toxicity by prior treatment with misonidazole is associated with increased levels of DNA crosslinks believed to be the critical lesion for bifunctional alkylating agent toxicity. Enhanced L-PAM crosslinking of DNA could occur by a variety of mechanisms in MISO-pretreated cells including: (1) increased transport or binding of L-PAM, (2) decreased repair of L-PAM monoadducts which would allow more time for their conversion to crosslinks, (3) decreased crosslink repair (unhooking of one arm), or (4) chemical modification of the DNA structure, presumably by bound MISO derivatives, such that crosslink formation is facilitated. Previous studies have eliminated mechanisms (1) and (3). Mechanism (4) was investigated by following MISO-pretreatments of whole cells with L-PAM treatments of the isolated DNA from these cells. Treatment of bare DNA with L-PAM modeled very well the crosslinking behavior in whole cells although it was somewhat more efficient. In the presence of double stranded DNA and absence of repair systems during and after the L-PAM exposure, it was determined that MISO-pretreatments did not increase the crosslinking efficiency of L-PAM

  4. Localization of protein aggregation in Escherichia coli is governed by diffusion and nucleoid macromolecular crowding effect.

    Directory of Open Access Journals (Sweden)

    Anne-Sophie Coquel

    2013-04-01

    Full Text Available Aggregates of misfolded proteins are a hallmark of many age-related diseases. Recently, they have been linked to aging of Escherichia coli (E. coli where protein aggregates accumulate at the old pole region of the aging bacterium. Because of the potential of E. coli as a model organism, elucidating aging and protein aggregation in this bacterium may pave the way to significant advances in our global understanding of aging. A first obstacle along this path is to decipher the mechanisms by which protein aggregates are targeted to specific intercellular locations. Here, using an integrated approach based on individual-based modeling, time-lapse fluorescence microscopy and automated image analysis, we show that the movement of aging-related protein aggregates in E. coli is purely diffusive (Brownian. Using single-particle tracking of protein aggregates in live E. coli cells, we estimated the average size and diffusion constant of the aggregates. Our results provide evidence that the aggregates passively diffuse within the cell, with diffusion constants that depend on their size in agreement with the Stokes-Einstein law. However, the aggregate displacements along the cell long axis are confined to a region that roughly corresponds to the nucleoid-free space in the cell pole, thus confirming the importance of increased macromolecular crowding in the nucleoids. We thus used 3D individual-based modeling to show that these three ingredients (diffusion, aggregation and diffusion hindrance in the nucleoids are sufficient and necessary to reproduce the available experimental data on aggregate localization in the cells. Taken together, our results strongly support the hypothesis that the localization of aging-related protein aggregates in the poles of E. coli results from the coupling of passive diffusion-aggregation with spatially non-homogeneous macromolecular crowding. They further support the importance of "soft" intracellular structuring (based on

  5. A Web Resource for Standardized Benchmark Datasets, Metrics, and Rosetta Protocols for Macromolecular Modeling and Design.

    Directory of Open Access Journals (Sweden)

    Shane Ó Conchúir

    Full Text Available The development and validation of computational macromolecular modeling and design methods depend on suitable benchmark datasets and informative metrics for comparing protocols. In addition, if a method is intended to be adopted broadly in diverse biological applications, there needs to be information on appropriate parameters for each protocol, as well as metrics describing the expected accuracy compared to experimental data. In certain disciplines, there exist established benchmarks and public resources where experts in a particular methodology are encouraged to supply their most efficient implementation of each particular benchmark. We aim to provide such a resource for protocols in macromolecular modeling and design. We present a freely accessible web resource (https://kortemmelab.ucsf.edu/benchmarks to guide the development of protocols for protein modeling and design. The site provides benchmark datasets and metrics to compare the performance of a variety of modeling protocols using different computational sampling methods and energy functions, providing a "best practice" set of parameters for each method. Each benchmark has an associated downloadable benchmark capture archive containing the input files, analysis scripts, and tutorials for running the benchmark. The captures may be run with any suitable modeling method; we supply command lines for running the benchmarks using the Rosetta software suite. We have compiled initial benchmarks for the resource spanning three key areas: prediction of energetic effects of mutations, protein design, and protein structure prediction, each with associated state-of-the-art modeling protocols. With the help of the wider macromolecular modeling community, we hope to expand the variety of benchmarks included on the website and continue to evaluate new iterations of current methods as they become available.

  6. [Macromolecular aromatic network characteristics of Chinese power coal analyzed by synchronous fluorescence and X-ray diffraction].

    Science.gov (United States)

    Ye, Cui-Ping; Feng, Jie; Li, Wen-Ying

    2012-07-01

    Coal structure, especially the macromolecular aromatic skeleton structure, has a strong influence on coke reactivity and coal gasification, so it is the key to grasp the macromolecular aromatic skeleton coal structure for getting the reasonable high efficiency utilization of coal. However, it is difficult to acquire their information due to the complex compositions and structure of coal. It has been found that the macromolecular aromatic network coal structure would be most isolated if small molecular of coal was first extracted. Then the macromolecular aromatic skeleton coal structure would be clearly analyzed by instruments, such as X-ray diffraction (XRD), fluorescence spectroscopy with synchronous mode (Syn-F), Gel permeation chromatography (GPC) etc. Based on the previous results, according to the stepwise fractional liquid extraction, two Chinese typical power coals, PS and HDG, were extracted by silica gel as stationary phase and acetonitrile, tetrahydrofuran (THF), pyridine and 1-methyl-2-pyrollidinone (NMP) as a solvent group for sequential elution. GPC, Syn-F and XRD were applied to investigate molecular mass distribution, condensed aromatic structure and crystal characteristics. The results showed that the size of aromatic layers (La) is small (3-3.95 nm) and the stacking heights (Lc) are 0.8-1.2 nm. The molecular mass distribution of the macromolecular aromatic network structure is between 400 and 1 130 amu, with condensed aromatic numbers of 3-7 in the structure units.

  7. Grain sorghum dust increases macromolecular efflux from the in situ nasal mucosa.

    Science.gov (United States)

    Gao, X P

    1998-04-01

    The purpose of this study was to determine whether an aqueous extract of grain sorghum dust increases macromolecular efflux from the nasal mucosa in vivo and, if so, whether this response is mediated, in part, by substance P. Suffusion of grain sorghum dust extract on the in situ nasal mucosa of anesthetized hamsters elicits a significant increase in clearance of fluorescein isothiocyanate-labeled dextran (FITC-dextran; mol mass, 70 kDa; P grain sorghum dust elicits neurogenic plasma exudation from the in situ nasal mucosa.

  8. Evaluation of quantum-chemical methods of radiolysis stability for macromolecular structures

    International Nuclear Information System (INIS)

    Postolache, Cristian; Matei, Lidia

    2005-01-01

    The behavior of macromolecular structures in ionising fields was analyzed by quantum-chemical methods. In this study the primary radiolytic effect was analyzed using a two-step radiolytic mechanism: a) ionisation of molecule and spatial redistribution of atoms in order to reach a minimum value of energy, characteristic to the quantum state; b) neutralisation of the molecule by electron capture and its rapid dissociation into free radicals. Chemical bonds suspected to break are located in the distribution region of LUMO orbital and have minimal homolytic dissociation energies. Representative polymer structures (polyethylene, polypropylene, polystyrene, poly α and β polystyrene, polyisobutylene, polytetrafluoroethylene, poly methylsiloxanes) were analyzed. (authors)

  9. Clustering procedures for the optimal selection of data sets from multiple crystals in macromolecular crystallography

    Science.gov (United States)

    Foadi, James; Aller, Pierre; Alguel, Yilmaz; Cameron, Alex; Axford, Danny; Owen, Robin L.; Armour, Wes; Waterman, David G.; Iwata, So; Evans, Gwyndaf

    2013-01-01

    The availability of intense microbeam macromolecular crystallography beamlines at third-generation synchrotron sources has enabled data collection and structure solution from microcrystals of sets from many crystals of the same protein structure. The associated analysis and merging of multi-crystal data is currently a manual and time-consuming step. Here, a computer program, BLEND, that has been written to assist with and automate many of the steps in this process is described. It is demonstrated how BLEND has successfully been used in the solution of a novel membrane protein. PMID:23897484

  10. Remote Access to the PXRR Macromolecular Crystallography Facilities at the NSLS

    Energy Technology Data Exchange (ETDEWEB)

    A Soares; D Schneider; J Skinner; M Cowan; R Buono; H Robinson; A Heroux; M Carlucci-Dayton; A Saxena; R Sweet

    2011-12-31

    The most recent surge of innovations that have simplified and streamlined the process of determining macromolecular structures by crystallography owes much to the efforts of the structural genomics community. However, this was only the last step in a long evolution that saw the metamorphosis of crystallography from an heroic effort that involved years of dedication and skill into a straightforward measurement that is occasionally almost trivial. Many of the steps in this remarkable odyssey involved reducing the physical labor that is demanded of experimenters in the field. Other steps reduced the technical expertise required for conducting those experiments.

  11. Clustering procedures for the optimal selection of data sets from multiple crystals in macromolecular crystallography.

    Science.gov (United States)

    Foadi, James; Aller, Pierre; Alguel, Yilmaz; Cameron, Alex; Axford, Danny; Owen, Robin L; Armour, Wes; Waterman, David G; Iwata, So; Evans, Gwyndaf

    2013-08-01

    The availability of intense microbeam macromolecular crystallography beamlines at third-generation synchrotron sources has enabled data collection and structure solution from microcrystals of structure. The associated analysis and merging of multi-crystal data is currently a manual and time-consuming step. Here, a computer program, BLEND, that has been written to assist with and automate many of the steps in this process is described. It is demonstrated how BLEND has successfully been used in the solution of a novel membrane protein.

  12. Remote Access to the PXRR Macromolecular Crystallography Facilities at the NSLS

    International Nuclear Information System (INIS)

    Soares, A.; Schneider, D.; Skinner, J.; Cowan, M.; Buono, R.; Robinson, H.; Heroux, A.; Carlucci-Dayton, M.; Saxena, A.; Sweet, R.

    2008-01-01

    The most recent surge of innovations that have simplified and streamlined the process of determining macromolecular structures by crystallography owes much to the efforts of the structural genomics community. However, this was only the last step in a long evolution that saw the metamorphosis of crystallography from an heroic effort that involved years of dedication and skill into a straightforward measurement that is occasionally almost trivial. Many of the steps in this remarkable odyssey involved reducing the physical labor that is demanded of experimenters in the field. Other steps reduced the technical expertise required for conducting those experiments.

  13. Theoretical studies of ionic conductivity of crosslinked chitosan membranes

    Energy Technology Data Exchange (ETDEWEB)

    Chavez, Ernesto Lopez [Programa de Ingenieria Molecular y Nuevos Materiales, Universidad Autonoma de la Ciudad de Mexico, Fray Servando Teresa de Mier 92, 1er. Piso, Col Centro, Mexico D.F. CP 06080 (Mexico); Oviedo-Roa, R.; Contreras-Perez, Gustavo; Martinez-Magadan, Jose Manuel [Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas Norte 152, Col. San Bartolo Atepehuacan, CP 07730 Mexico D.F. (Mexico); Castillo-Alvarado, F.L. [Escuela Superior de Fisica y Matematicas del Instituto Politecnico Nacional, Edificio 9 de la UPALM, Colonia Lindavista, Mexico D.F. CP 07738 (Mexico)

    2010-11-15

    Ionic conductivity of crosslinked chitosan membranes was studied using techniques of molecular modeling and simulation. The COMPASS force field was used. The simulation allows the description of the mechanism of ionic conductivity along the polymer matrix. The theoretical results obtained are compared with experimental results for chitosan membranes. The analysis suggests that the conduction mechanism is portrayed by the overlapping large Polaron tunneling model. In addition, when the chitosan membrane was crosslinked with an appropriate degree of crosslinking its ionic conductivity, at room temperature, was increased by about one order of magnitude. The chitosan membranes can be used as electrolytes in solid state batteries, electric double layer capacitors and fuel cells. (author)

  14. Crosslinking of commercial polyethylenes by 10 MeV electrons

    International Nuclear Information System (INIS)

    Singh, A.; Lopata, V.J.; Kremers, W.; Sze, Yu-keung

    1995-08-01

    Commercial polyethylenes were irradiated with 10 MeV electrons to induce crosslinking. The gel fraction data measured as a function of total dose suggests that crosslinking proceeds on irradiation, as expected. A number of the properties of the irradiated polyethylenes, such as the degree of oxidation, crystallinity and thermal degradation, were studied by Fourier transform infrared/photo acoustic spectroscopy, X-ray diffraction, and a pyrolysis technique coupled with gas chromatography and mass spectrometry. The results of this study suggest that commercial polyethylenes can be crosslinked to a gel fraction of ∼70%, required for wire and cable applications, by 10 MeV electrons. (author). 35 refs., 6 figs

  15. Nitrile crosslinked polyphenyl-quinoxaline/graphite fiber composites

    Science.gov (United States)

    Alston, W. B.

    1976-01-01

    Studies were performed to reduce the 600 F thermoplasticity of polyphenylquinoxaline (PPQ) matrix resins by introducing crosslinking by the reaction of terminal nitrile groups. Seven solvents and solvent mixtures were studied as the crosslinking catalysts and used to fabricate crosslinked PPQ/HMS graphite fiber composites. The room temperature and 600 F composite mechanical properties after short time and prolonged 600 F air exposure and the 600 F composite weight loss were determined and compared to those properties of high molecular weight, linear PPQ/HMS graphite fiber composites.

  16. Current status of accelerated corneal cross-linking

    Directory of Open Access Journals (Sweden)

    Michael Mrochen

    2013-01-01

    Full Text Available Corneal cross-linking with riboflavin is a technique to stabilize or reduce corneal ectasia, in diseases such as keratoconus and post-laser-assisted in situ keratomileusis (LASIK ectasia. There is an interest by patient as well as clinicians to reduce the overall treatment time. Especially, the introduction of corneal cross-linking in combination with corneal laser surgery demands a shorter treatment time to assure a sufficient patient flow. The principles and techniques of accelerated corneal cross-linking is discussed.

  17. Radiation degradation and crosslinking of polytetrafluoroethylene and its application

    International Nuclear Information System (INIS)

    Wu Guozhong; Wang Mouhua; Tang Zhongfeng

    2009-01-01

    Polytetrafluoroethylene (PTFE) is a high-performance engineering plastic and known as a typical material of radiation degradation. PTFE can be degraded by radiation under various conditions and PTFE micro-powder is usually fabricated by a combination of radiation and milling. PTFE can also be crosslinked by irradiation in the melt state (330∼340 degree C). The materials can be applied as a special additive due to its excellent wear resistance. Crosslinked PTFE may also be applied in lithography and fuel cell membrane in the future. In this paper, history and application of PTFE degradation and crosslinking products are reviewed. (authors)

  18. Production of radiation crosslinked polymeric compositions using diacetylenes

    International Nuclear Information System (INIS)

    Patel, G.N.

    1979-01-01

    Crosslinked polymeric compositions, useful as electrical insulators, heat shrinkable packaging, and lightweight foam plastics, are described. The crosslinked polymeric compositions are produced by admixing a diacetylene monomer, oligomer, polymer or mixture thereof, wherein the monomer has the formula, RNHCO-O-CH 2 -C==C-C==C-CH- 2 -O-OCNHR' in which R and R' are the same or different and are alkyl containing 1 to 20 carbon atoms, with a thermoplastic crosslinkable polymer and then subjecting the resulting mixture to actinic radiation

  19. A Molecular Dynamics Study of Crosslinked Phthalonitrile Polymers: The Effect of Crosslink Density on Thermomechanical and Dielectric Properties

    Directory of Open Access Journals (Sweden)

    Janel Chua

    2018-01-01

    Full Text Available In this work, molecular dynamics (MD and molecular mechanics (MM simulations are used to study well-equilibrated models of 4,4′-bis(3,4-dicyanophenoxybiphenyl (BPh–1,3-bis(3-aminophenoxybenzene (m-APB phthalonitrile (PN system with a range of crosslink densities. A cross-linking technique is introduced to build a series of systems with different crosslink densities; several key properties of this material, including thermal expansion, mechanical properties and dielectric properties are studied and compared with experimental results. It is found that the coefficient of linear thermal expansion predicted by the model is in good agreement with experimental results and indicative of the good thermal stability of the PN polymeric system. The simulation also shows that this polymer has excellent mechanical property, whose strength increases with increasing crosslink density. Lastly and most importantly, the calculated dielectric constant—which shows that this polymer is an excellent insulating material—indicates that there is an inverse relation between cross-linking density and dielectric constant. The trend gave rise to an empirical quadratic function which can be used to predict the limits of attainable dielectric constant for highly crosslinked polymer systems. The current computational work provides strong evidence that this polymer is a promising material for aerospace applications and offers guidance for experimental studies of the effect of cross-linking density on the thermal, mechanical and dielectric properties of the material.

  20. Radiation crosslinking of poly(butyl acrylate) during polymerization and grafted copolymerization with Cr(III) crosslinked collagen

    International Nuclear Information System (INIS)

    Pietrucha, K.; Kroh, J.

    1984-01-01

    Enhanced crosslinking of synthetic polymer simultaneous with grafting and homopolymerization processes have been observed in irradiated leather tanned with Cr(III) and embedded with aqueous emulsions of butyl acrylate. Extent of poly(butyl acrylate) crosslinking during copolymerization was found to be approximately one order higher than in the case of radiation polymerization of butyl acrylate in emulsion. New method for isolation of grafted copolymer based on degradation of collagen has been developed. The extent of crosslinking was calculated from the swelling data. (author)

  1. Radiation crosslinking of poly(butyl acrylate) during polymerization and grafted copolymerization with Cr(III) crosslinked collagen

    International Nuclear Information System (INIS)

    Pietrucha, K.; Kroh, J.

    1986-01-01

    Enhanced crosslinking of synthetic polymer simultaneously with grafting and homopolymerization processes has been observed in irradiated leather tanned with Cr(III) and embedded with aqueous emulsions of butyl acrylate. The extent of poly(butyl acrylate) crosslinking during copolymerization was found to be approximately one order higher than in the case of radiation polymerization of butyl acrylate in emulsion. A new method for isolation of grafted copolymer based on degradation of collagen has been developed. The extent of crosslinking was calculated from the swelling data. (author)

  2. Riboflavin for corneal cross-linking.

    Science.gov (United States)

    O'Brart, D P S

    2016-06-01

    Corneal collagen cross-linking (CXL) with riboflavin and ultraviolet A (UVA) radiation is the first therapeutic modality that appears to arrest the progression of keratoconus and other corneal ectasias. Riboflavin is central to the process, acting as a photosensitizer for the production of oxygen singlets and riboflavin triplets. These free radicals drive the CXL process within the proteins of the corneal stroma, altering its biomechanical properties. Riboflavin also absorbs the majority of the UVA radiation, which is potentially cytotoxic and mutagenic, within the anterior stroma, preventing damage to internal ocular structures, such as the corneal endothelium, lens and retina. Clinical studies report cessation of ectatic progression in over 90% of cases and the majority document significant improvements in visual, keratometric and topographic parameters. Clinical follow-up is limited to 5-10 years, but suggests sustained stability and enhancement in corneal shape. Sight-threatening complications are rare. The optimal stromal riboflavin dosage for CXL is as yet undetermined. Copyright 2016 Prous Science, S.A.U. or its licensors. All rights reserved.

  3. Radiation induced crosslinking of cellulose ethers

    International Nuclear Information System (INIS)

    Wach, A.R.; Mitomo, H.; Yoshii, F.; Kume, T.

    2002-01-01

    The effects of high-energy radiation on four ethers of cellulose: carboxymethyl (CMC); hydroxypropyl (HPC), hydroxyethyl (HEC) and methylcellulose (MC) were investigated. Polymers are irradiated in solid state and in aqueous solutions at various concentrations. Degree of substitution (DS) of the derivatives, the concentration of their aqueous solutions and irradiation conditions had a significant impact on the obtained products. Irradiation of polymers in solid state and in diluted aqueous solutions resulted in their degradation. However, it was found that for concentrated solutions gel formation occurred. Paste-like form of the initial material, when water plasticizes the bulk of polymer as well as the high dose rate, what prevents oxygen penetration of the polymer during irradiation, have been found favourable for hydrogel formation. Up to 95% of gel fraction was obtained from solutions of CMC with concentration over 50% irradiated by γ-rays or electron beam. It was pointed out that the ability to the formation of the three-dimensional network is related to the DS of anhydroglucose units and a type of chemical group introduced to main chain of cellulose. Produced hydrogels swelled markedly in water. Despite of the crosslinked structure they underwent degradation by the action of cellulase enzyme or microorganisms from compost, and can be included into the group of biodegradable materials. (author)

  4. Crosslinked polyimide electro-optic materials

    Energy Technology Data Exchange (ETDEWEB)

    Kowalczyk, T.C.; Kosc, T.Z.; Singer, K.D. [Case Western Reserve University, Department of Physics, Cleveland, Ohio 44106-7079 (United States); Beuhler, A.J.; Wargowski, D.A. [Amoco Research Center, Amoco Chemical Co., Naperville, Illinois 60566 (United States); Cahill, P.A.; Seager, C.H.; Meinhardt, M.B. [Sandia National Laboratories, Division 1811, Albuquerque, New Mexico 87185-1407 (United States); Ermer, S. [Lockheed Research and Development Division, Palo Alto, California 94304 (United States)

    1995-11-15

    We report studies of the optical and electro-optic properties of guest--host polymeric nonlinear optical materials based on aromatic, fluorinated, fully imidized, organic soluble, thermally, and photochemically crosslinkable, guest--host polyimides. We have introduced temperature stable nonlinear optical chromophores into these polyimides and studied optical losses, electric field poling, electro-optic properties, and orientational stability. We measured electro-optic coefficients of 5.5 and 12.0 pm/V for ((2,6-Bis(2-(3-(9-(ethyl)carbazolyl))ethenyl)4H-pyran-4-ylidene)propanedinitrile) (4-(Dicyanomethylene)-2-methyl-6-(p -dimethylaminostyryl)-4H-pyran) DCM-doped guest--host systems at 800 nm using a poling field of 1.3 MV/cm. Poling induced nonlinearities in single-layer films were in agreement with the oriented gas model, but were lower in three-layer films due to voltage division across the layers. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  5. Covalently crosslinked diels-alder polymer networks.

    Energy Technology Data Exchange (ETDEWEB)

    Bowman, Christopher (University of Colorado, Boulder, CO); Adzima, Brian J. (University of Colorado, Boulder, CO); Anderson, Benjamin John

    2011-09-01

    This project examines the utility of cycloaddition reactions for the synthesis of polymer networks. Cycloaddition reactions are desirable because they produce no unwanted side reactions or small molecules, allowing for the formation of high molecular weight species and glassy crosslinked networks. Both the Diels-Alder reaction and the copper-catalyzed azide-alkyne cycloaddition (CuAAC) were studied. Accomplishments include externally triggered healing of a thermoreversible covalent network via self-limited hysteresis heating, the creation of Diels-Alder based photoresists, and the successful photochemical catalysis of CuAAC as an alternative to the use of ascorbic acid for the generation of Cu(I) in click reactions. An analysis of the results reveals that these new methods offer the promise of efficiently creating robust, high molecular weight species and delicate three dimensional structures that incorporate chemical functionality in the patterned material. This work was performed under a Strategic Partnerships LDRD during FY10 and FY11 as part of a Sandia National Laboratories/University of Colorado-Boulder Excellence in Science and Engineering Fellowship awarded to Brian J. Adzima, a graduate student at UC-Boulder. Benjamin J. Anderson (Org. 1833) was the Sandia National Laboratories point-of-contact for this fellowship.

  6. 21 CFR 177.1211 - Cross-linked polyacrylate copolymers.

    Science.gov (United States)

    2010-04-01

    ... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1211 Cross-linked polyacrylate... shall be determined using size exclusion chromatography or an equivalent method. When conducting the...

  7. Syntheses of crosslinked latex nanoparticles using differential microemulsion polymerization

    Science.gov (United States)

    Hassmoro, N. F.; Rusop, M.; Abdullah, S.

    2013-06-01

    The differential microemulsion polymerization was used to synthesize latex nanoparticles. In this paper, 1, 3-butylene glycol dimethacrylate (1, 3-BGDMA) was used as a crosslinker respectively 1-5 weight% of monomer total. Butyl acrylate (BA), butyl methacrylate (BMA), and methacrylic acid (MAA) was used as the monomer. The thin film of latex nanoparticles were prepared by using spin coating method and have been dried at 100°C for 5 minutes. The amount of the crosslinker added in the polymerization was optimized and we found that the particle sizes fall in the range of 30-60 nm. The structural morphology of the uncrosslinked latex represented the most homogeneous image compared to the crosslinked latex. The effect of the amount of crosslinker on the particle sizes investigated by the Zeta-sizer Nano series while Atomic Force microscopy (AFM) was used to study the structural properties of latex nanoparticles.

  8. Syntheses of crosslinked latex nanoparticles using differential microemulsion polymerization

    International Nuclear Information System (INIS)

    Hassmoro, N F; Abdullah, S; Rusop, M

    2013-01-01

    The differential microemulsion polymerization was used to synthesize latex nanoparticles. In this paper, 1, 3-butylene glycol dimethacrylate (1, 3-BGDMA) was used as a crosslinker respectively 1–5 weight% of monomer total. Butyl acrylate (BA), butyl methacrylate (BMA), and methacrylic acid (MAA) was used as the monomer. The thin film of latex nanoparticles were prepared by using spin coating method and have been dried at 100°C for 5 minutes. The amount of the crosslinker added in the polymerization was optimized and we found that the particle sizes fall in the range of 30–60 nm. The structural morphology of the uncrosslinked latex represented the most homogeneous image compared to the crosslinked latex. The effect of the amount of crosslinker on the particle sizes investigated by the Zeta-sizer Nano series while Atomic Force microscopy (AFM) was used to study the structural properties of latex nanoparticles.

  9. Photoreactivities and thermal properties of psoralen cross-links

    International Nuclear Information System (INIS)

    Yeung, A.T.; Jones, B.K.; Chu, C.T.

    1988-01-01

    The authors have studied the photoreaction of 8-methoxypsoralen (8-MOP), 4,5',8-trimethylpsoralen (TMP), and 4'-(hydroxymethyl)-4,5',8-trimethylpsoralen (HMT) with a pair of 18-base-long oligonucleotides in which a 14-base region is complementary. Only one 5'TpA site, favored for both monoadduct and cross-link formation with psoralen, is present in this oligonucleotide pair. They have used this model system to demonstrate, for the first time, strand specificity in the photoreaction of psoralen with DNA. They found that the two types of cross-links which form at this site have large differences in thermal stabilities. In addition, the denaturation of each cross-links isomer duplex occurred in at least three stages, which can be visualized as three bands in thermal equilibrium under the conditions of a denaturing polyacrylamide gel. This novel observation suggests that there are several domains differing in thermal stability in a psoralen cross-link

  10. Shaped articles of cross-linked fluorocarbon polymers

    International Nuclear Information System (INIS)

    Gotcher, A.J.; Germeraad, P.B.

    1981-01-01

    A process is described which comprises (1) contacting (a) a shaped article of a polymeric composition wherein the polymer is a fluorocarbon polymer having a melting point of at least 200 0 C, the article having a tensile strength of at least 3,000 psi, with (b) a fluid composition comprising a cross-linking agent, until the article contains at least 2.5% by weight of the cross-linking agent; and (2) irradiating the shaped article with ionising radiation to a dosage not exceeding 50 Mrads under conditions such that the composition is cross-linked sufficiently to impart thereto an M 100 value of at least 300 psi, while maintaining a tensile strength of at least 3000 psi, the shaped article containing a specified proportion of the cross-linking agent. (author)

  11. Covalently cross-linked polyetheretherketone proton exchange membrane for DMFC

    CSIR Research Space (South Africa)

    Luo, H

    2009-05-01

    Full Text Available -7 cm2/s) and good electrochemical stability. The results suggested that cross-linked polyetheretherketone membrane is particularly promising to be used as proton exchange membrane for the direct methanol fuel cell application....

  12. Biocompatibility and tissue regenerating capacity of crosslinked dermal sheep collagen

    NARCIS (Netherlands)

    van Wachem, P.B.; van Luyn, M.J.A.; Olde Damink, L.H.H.; Olde damink, L.H.H.; Dijkstra, Pieter J.; Feijen, Jan; Nieuwenhuis, P.

    1994-01-01

    The biocompatibility and tissue regenerating capacity of four crosslinked dermal sheep collagens (DSC) was studied. In vitro, the four DSC versions were found to be noncytotoxic or very low in cytoxicity. After subcutaneous implantation in rats, hexamethylenediisocyanatecrcrosslinked DSC (HDSC)

  13. Formaldehyde cross-linking and structural proteomics: Bridging the gap.

    Science.gov (United States)

    Srinivasa, Savita; Ding, Xuan; Kast, Juergen

    2015-11-01

    Proteins are dynamic entities constantly moving and altering their structures based on their functions and interactions inside and outside the cell. Formaldehyde cross-linking combined with mass spectrometry can accurately capture interactions of these rapidly changing biomolecules while maintaining their physiological surroundings. Even with its numerous established uses in biology and compatibility with mass spectrometry, formaldehyde has not yet been applied in structural proteomics. However, formaldehyde cross-linking is moving toward analyzing tertiary structure, which conventional cross-linkers have already accomplished. The purpose of this review is to describe the potential of formaldehyde cross-linking in structural proteomics by highlighting its applications, characteristics and current status in the field. Copyright © 2015 Elsevier Inc. All rights reserved.

  14. Multiple molecular forms of pyridinoline crosslinks generated by the ...

    African Journals Online (AJOL)

    molecular forms of pyridinoline crosslinks from insoluble bone type I collagen, and we studied ... resorbed in a dynamic process during ... proteins at 4 C for 24H in 4 mol/L .... fragments was merely due to interactions ... completely elucidated.

  15. The Effect of Polymer Molecular Weight on Citrate Crosslinked ...

    African Journals Online (AJOL)

    Erah

    Purpose: To develop citrate crosslinked chitosan films using chitosan of different molecular weights. (MW) in .... left to stand until trapped air bubbles ... blotted out carefully with filter paper from the .... potential as biodegradable stent coatings. J.

  16. Enzymatic digestibility of peptides cross-linked by ionizing radiation

    International Nuclear Information System (INIS)

    Dizdaroglu, M.; Gajewski, E.; Simic, M.G.

    1984-01-01

    Digestibility by proteolytic enzymes of peptides cross-linked by ionizing radiation was investigated. Small peptides of alanine and phenylalanine were chosen as model compounds and aminopeptidases and carboxypeptidases were used as proteolytic enzymes. Peptides exposed to γ-radiation in aqueous solution were analysed by high-performance liquid chromatography before and after hydrolysis by aminopeptidase M, leucine aminopeptidase carboxypeptidase A and carboxypeptidase Y. The results obtained clearly demonstrate the different actions of these enzymes on cross-linked aliphatic and aromatic peptides. Peptide bonds of cross-linked dipeptides of alanine were completely resistant to enzymatic hydrolysis whereas the enzymes, except for carboxypeptidase Y, cleaved all peptide bonds of cross-linked peptides of phenylalanine. The actions of the enzymes on these particular compounds are discussed in detail. (author)

  17. A brief history of macromolecular crystallography, illustrated by a family tree and its Nobel fruits.

    Science.gov (United States)

    Jaskolski, Mariusz; Dauter, Zbigniew; Wlodawer, Alexander

    2014-09-01

    As a contribution to the celebration of the year 2014, declared by the United Nations to be 'The International Year of Crystallography', the FEBS Journal is dedicating this issue to papers showcasing the intimate union between macromolecular crystallography and structural biology, both in historical perspective and in current research. Instead of a formal editorial piece, by way of introduction, this review discusses the most important, often iconic, achievements of crystallographers that led to major advances in our understanding of the structure and function of biological macromolecules. We identified at least 42 scientists who received Nobel Prizes in Physics, Chemistry or Medicine for their contributions that included the use of X-rays or neutrons and crystallography, including 24 who made seminal discoveries in macromolecular sciences. Our spotlight is mostly, but not only, on the recipients of this most prestigious scientific honor, presented in approximately chronological order. As a summary of the review, we attempt to construct a genealogy tree of the principal lineages of protein crystallography, leading from the founding members to the present generation. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

  18. Long-wavelength macromolecular crystallography - First successful native SAD experiment close to the sulfur edge

    Science.gov (United States)

    Aurelius, O.; Duman, R.; El Omari, K.; Mykhaylyk, V.; Wagner, A.

    2017-11-01

    Phasing of novel macromolecular crystal structures has been challenging since the start of structural biology. Making use of anomalous diffraction of natively present elements, such as sulfur and phosphorus, for phasing has been possible for some systems, but hindered by the necessity to access longer X-ray wavelengths in order to make most use of the anomalous scattering contributions of these elements. Presented here are the results from a first successful experimental phasing study of a macromolecular crystal structure at a wavelength close to the sulfur K edge. This has been made possible by the in-vacuum setup and the long-wavelength optimised experimental setup at the I23 beamline at Diamond Light Source. In these early commissioning experiments only standard data collection and processing procedures have been applied, in particular no dedicated absorption correction has been used. Nevertheless the success of the experiment demonstrates that the capability to extract phase information can be even further improved once data collection protocols and data processing have been optimised.

  19. Organ specific acute toxicity of the carcinogen trans-4-acetylaminostilbene is not correlated with macromolecular binding.

    Science.gov (United States)

    Pfeifer, A; Neumann, H G

    1986-09-01

    trans-4-Acetylaminostilbene (trans-AAS) is acutely toxic in rats and lesions are produced specifically in the glandular stomach. Toxicity is slightly increased by pretreating the animals with phenobarbital (PB) and is completely prevented by pretreatment with methylcholanthrene (MC). The prostaglandin inhibitors, indomethacin and acetyl salicylic acid, do not reduce toxicity. The high efficiency of MC suggested that toxicity is caused by reactive metabolites. trans-[3H]-AAS was administered orally to untreated and to PB- or MC-pretreated female Wistar rats and target doses in different tissues were measured by means of covalent binding to proteins, RNA and DNA. Macromolecular binding in the target tissue of poisoned animals was significantly lower than in liver and kidney and comparable to other non-target tissues. Pretreatment with MC lowered macromolecular binding in all extrahepatic tissues but not in liver. These findings are not in line with tissue specific metabolic activation. The only unique property of the target tissue, glandular stomach, that we observed was a particular affinity for the systemically available parent compound. In the early phase of poisoning, tissue concentrations were exceedingly high and the stomach function was impaired.

  20. Can visco-elastic phase separation, macromolecular crowding and colloidal physics explain nuclear organisation?

    Directory of Open Access Journals (Sweden)

    Iborra Francisco J

    2007-04-01

    Full Text Available Abstract Background The cell nucleus is highly compartmentalized with well-defined domains, it is not well understood how this nuclear order is maintained. Many scientists are fascinated by the different set of structures observed in the nucleus to attribute functions to them. In order to distinguish functional compartments from non-functional aggregates, I believe is important to investigate the biophysical nature of nuclear organisation. Results The various nuclear compartments can be divided broadly as chromatin or protein and/or RNA based, and they have very different dynamic properties. The chromatin compartment displays a slow, constrained diffusional motion. On the other hand, the protein/RNA compartment is very dynamic. Physical systems with dynamical asymmetry go to viscoelastic phase separation. This phase separation phenomenon leads to the formation of a long-lived interaction network of slow components (chromatin scattered within domains rich in fast components (protein/RNA. Moreover, the nucleus is packed with macromolecules in the order of 300 mg/ml. This high concentration of macromolecules produces volume exclusion effects that enhance attractive interactions between macromolecules, known as macromolecular crowding, which favours the formation of compartments. In this paper I hypothesise that nuclear compartmentalization can be explained by viscoelastic phase separation of the dynamically different nuclear components, in combination with macromolecular crowding and the properties of colloidal particles. Conclusion I demonstrate that nuclear structure can satisfy the predictions of this hypothesis. I discuss the functional implications of this phenomenon.

  1. Time-efficient, high-resolution, whole brain three-dimensional macromolecular proton fraction mapping.

    Science.gov (United States)

    Yarnykh, Vasily L

    2016-05-01

    Macromolecular proton fraction (MPF) mapping is a quantitative MRI method that reconstructs parametric maps of a relative amount of macromolecular protons causing the magnetization transfer (MT) effect and provides a biomarker of myelination in neural tissues. This study aimed to develop a high-resolution whole brain MPF mapping technique using a minimal number of source images for scan time reduction. The described technique was based on replacement of an actually acquired reference image without MT saturation by a synthetic one reconstructed from R1 and proton density maps, thus requiring only three source images. This approach enabled whole brain three-dimensional MPF mapping with isotropic 1.25 × 1.25 × 1.25 mm(3) voxel size and a scan time of 20 min. The synthetic reference method was validated against standard MPF mapping with acquired reference images based on data from eight healthy subjects. Mean MPF values in segmented white and gray matter appeared in close agreement with no significant bias and small within-subject coefficients of variation (maps demonstrated sharp white-gray matter contrast and clear visualization of anatomical details, including gray matter structures with high iron content. The proposed synthetic reference method improves resolution of MPF mapping and combines accurate MPF measurements with unique neuroanatomical contrast features. © 2015 Wiley Periodicals, Inc.

  2. ISPyB: an information management system for synchrotron macromolecular crystallography.

    Science.gov (United States)

    Delagenière, Solange; Brenchereau, Patrice; Launer, Ludovic; Ashton, Alun W; Leal, Ricardo; Veyrier, Stéphanie; Gabadinho, José; Gordon, Elspeth J; Jones, Samuel D; Levik, Karl Erik; McSweeney, Seán M; Monaco, Stéphanie; Nanao, Max; Spruce, Darren; Svensson, Olof; Walsh, Martin A; Leonard, Gordon A

    2011-11-15

    Individual research groups now analyze thousands of samples per year at synchrotron macromolecular crystallography (MX) resources. The efficient management of experimental data is thus essential if the best possible experiments are to be performed and the best possible data used in downstream processes in structure determination pipelines. Information System for Protein crystallography Beamlines (ISPyB), a Laboratory Information Management System (LIMS) with an underlying data model allowing for the integration of analyses down-stream of the data collection experiment was developed to facilitate such data management. ISPyB is now a multisite, generic LIMS for synchrotron-based MX experiments. Its initial functionality has been enhanced to include improved sample tracking and reporting of experimental protocols, the direct ranking of the diffraction characteristics of individual samples and the archiving of raw data and results from ancillary experiments and post-experiment data processing protocols. This latter feature paves the way for ISPyB to play a central role in future macromolecular structure solution pipelines and validates the application of the approach used in ISPyB to other experimental techniques, such as biological solution Small Angle X-ray Scattering and spectroscopy, which have similar sample tracking and data handling requirements.

  3. A new paradigm for macromolecular crystallography beamlines derived from high-pressure methodology and results

    Energy Technology Data Exchange (ETDEWEB)

    Fourme, Roger, E-mail: roger.fourme@synchrotron-soleil.fr [Synchrotron SOLEIL, BP 48, Saint Aubin, 91192 Gif-sur-Yvette (France); Girard, Eric [IBS (UMR 5075 CEA-CNRS-UJF-PSB), 41 rue Jules Horowitz, 38027 Grenoble Cedex (France); Dhaussy, Anne-Claire [CRISMAT, ENSICAEN, 6 Boulevard du Maréchal Juin, 14000 Caen (France); Medjoubi, Kadda [Synchrotron SOLEIL, BP 48, Saint Aubin, 91192 Gif-sur-Yvette (France); Prangé, Thierry [LCRB (UMR 8015 CNRS), Université Paris Descartes, Faculté de Pharmacie, 4 avenue de l’Observatoire, 75270 Paris (France); Ascone, Isabella [ENSCP (UMR CNRS 7223), 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); Mezouar, Mohamed [ESRF, BP 220, 38043 Grenoble (France); Kahn, Richard [IBS (UMR 5075 CEA-CNRS-UJF-PSB), 41 rue Jules Horowitz, 38027 Grenoble Cedex (France)

    2011-01-01

    Macromolecular crystallography at high pressure (HPMX) is a mature technique. Shorter X-ray wavelengths increase data collection efficiency on cryocooled crystals. Extending applications and exploiting spin-off of HPMX will require dedicated synchrotron radiation beamlines based on a new paradigm. Biological structures can now be investigated at high resolution by high-pressure X-ray macromolecular crystallography (HPMX). The number of HPMX studies is growing, with applications to polynucleotides, monomeric and multimeric proteins, complex assemblies and even a virus capsid. Investigations of the effects of pressure perturbation have encompassed elastic compression of the native state, study of proteins from extremophiles and trapping of higher-energy conformers that are often of biological interest; measurements of the compressibility of crystals and macromolecules were also performed. HPMX results were an incentive to investigate short and ultra-short wavelengths for standard biocrystallography. On cryocooled lysozyme crystals it was found that the data collection efficiency using 33 keV photons is increased with respect to 18 keV photons. This conclusion was extended from 33 keV down to 6.5 keV by exploiting previously published data. To be fully exploited, the potential of higher-energy photons requires detectors with a good efficiency. Accordingly, a new paradigm for MX beamlines was suggested, using conventional short and ultra-short wavelengths, aiming at the collection of very high accuracy data on crystals under standard conditions or under high pressure. The main elements of such beamlines are outlined.

  4. Polydisulfide Manganese(II) Complexes as Non-Gadolinium Biodegradable Macromolecular MRI Contrast Agents

    Science.gov (United States)

    Ye, Zhen; Jeong, Eun-Kee; Wu, Xueming; Tan, Mingqian; Yin, Shouyu; Lu, Zheng-Rong

    2011-01-01

    Purpose To develop safe and effective manganese(II) based biodegradable macromolecular MRI contrast agents. Materials and Methods In this study, we synthesized and characterized two polydisulfide manganese(II) complexes, Mn-DTPA cystamine copolymers and Mn-EDTA cystamine copolymers, as new biodegradable macromolecular MRI contrast agents. The contrast enhancement of the two manganese based contrast agents were evaluated in mice bearing MDA-MB-231 human breast carcinoma xenografts, in comparison with MnCl2. Results The T1 and T2 relaxivities were 4.74 and 10.38 mM−1s−1 per manganese at 3T for Mn-DTPA cystamine copolymers (Mn=30.50 kDa) and 6.41 and 9.72 mM−1s−1 for Mn-EDTA cystamine copolymers (Mn= 61.80 kDa). Both polydisulfide Mn(II) complexes showed significant liver, myocardium and tumor enhancement. Conclusion The manganese based polydisulfide contrast agents have a potential to be developed as alternative non-gadolinium contrast agents for MR cancer and myocardium imaging. PMID:22031457

  5. Highly efficient perovskite solar cells with crosslinked PCBM interlayers

    KAUST Repository

    Qiu, W.

    2017-01-09

    Commercially available phenyl-C-butyric acid methyl ester (PCBM) is crosslinked with 1,6-diazidohexane (DAZH), resulting in films resistant to common solvents used in perovskite solar cell processing. By using crosslinked PCBM as an interlayer and (HC(NH))(CHNH)PbIBr as the active layer, we achieve small area devices and modules with a maximum steady-state power conversion efficiency of 18.1% and 14.9%, respectively.

  6. Fanconi anemia (cross)linked to DNA repair.

    Science.gov (United States)

    Niedernhofer, Laura J; Lalai, Astrid S; Hoeijmakers, Jan H J

    2005-12-29

    Fanconi anemia is characterized by hypersensitivity to DNA interstrand crosslinks (ICLs) and susceptibility to tumor formation. Despite the identification of numerous Fanconi anemia (FANC) genes, the mechanism by which proteins encoded by these genes protect a cell from DNA interstrand crosslinks remains unclear. The recent discovery of two DNA helicases that, when defective, cause Fanconi anemia tips the balance in favor of the direct involvement of the FANC proteins in DNA repair and the bypass of DNA lesions.

  7. MX1: a bending-magnet crystallography beamline serving both chemical and macromolecular crystallography communities at the Australian Synchrotron

    International Nuclear Information System (INIS)

    Cowieson, Nathan Philip; Aragao, David; Clift, Mark; Ericsson, Daniel J.; Gee, Christine; Harrop, Stephen J.; Mudie, Nathan; Panjikar, Santosh; Price, Jason R.; Riboldi-Tunnicliffe, Alan; Williamson, Rachel; Caradoc-Davies, Tom

    2015-01-01

    The macromolecular crystallography beamline MX1 at the Australian Synchrotron is described. MX1 is a bending-magnet crystallography beamline at the 3 GeV Australian Synchrotron. The beamline delivers hard X-rays in the energy range from 8 to 18 keV to a focal spot at the sample position of 120 µm FWHM. The beamline endstation and ancillary equipment facilitate local and remote access for both chemical and biological macromolecular crystallography. Here, the design of the beamline and endstation are discussed. The beamline has enjoyed a full user program for the last seven years and scientific highlights from the user program are also presented

  8. Radiation crosslinking of polymer materials and its functional properties

    International Nuclear Information System (INIS)

    Yoshii, Fumio

    2006-01-01

    It was found out that radiation crosslinking of biodegradable polymer such as poly (butylene succinate, PBS) and poly(ε-caprolactone, PCL) could be achieved by radiation in the presence of small amount of trimethallyl isocyanurate (TMAIC) or 1% triallyl isocyanurate (TAIC). Such modification is very effective to improve heat resistance for PBS and PCL. Poly (lactic acid, PLA) undergoes crosslinking effectively with 3% TAIC by radiation. Outstanding feature of these polymers is their biodegradability even after crosslinking. Radiation crosslinking of polysaccharide derivatives such as carboxymethyl-cellulose (CMC) is also achieved in aqueous solution at high concentration (paste-like state). The crosslinking behavior was largely affected by the degree of substitution (DS) and polymer concentration. After removal of water the dry CMC gel is used as water absorbent material. This dry gel is the most effective for removal of large amounts of water from organic wastes, resulting in the acceleration of their fermentation. Measurement of swelling ratio of the dry CMC gel in 0.9% NaCl aqueous solution was carried out to expand application fields for this material. Radiation crosslinked poly (vinyl alcohol) hydrogel was successfully commercialized from July 2004 as wound dressing for accelerated healing. Furthermore, this material was also used as gel protector to prevent shore sore and was further commercialized. (author)

  9. The spectra character of photodegraded the pyridinoline cross-links by Hypocrellin B

    International Nuclear Information System (INIS)

    Zhang Jucheng; Chen Rui; Liu Wei; Chen Zhuo; Shu Lidan; Liu Yingji

    2011-01-01

    Pyridinoline cross-links is one of the cross-link formation in collagen which in cell matrix, many research shown that this cross-link cause the fibrosis. Hypocrellin B (HB) is one of the nature photosensitizers, this work investigated the pyridinoline cross-link in collagen was photodegraded by HB. The result shown HB can degrade the pyridinoline cross-link with photo. This is to say, HB may be use as the photodynamic reagent to study the fibrosis.

  10. Novel block, graft and random copolymers for biomedical applications

    DEFF Research Database (Denmark)

    Javakhishvili, Irakli; Jankova Atanasova, Katja; Tanaka, Masaru

    Despite the simple structure, poly(2-methoxyethyl acrylate) (PMEA) shows excellent blood compatibility [1]. Both the freezing-bound water (intermediate water: preventing the biocomponents from directly contacting the polymer surface) and non-freezing water on the polymer surface play important...... copolymers with MMA [4] utilizing ATRP. Here we present other block, graft and random copolymers of MEA intended for biomedical applications. These macromolecular architectures have been constructed by employing controlled radical polymerization methods such as RAFT and ATRP....

  11. Nitric oxide-induced interstrand cross-links in DNA.

    Science.gov (United States)

    Caulfield, Jennifer L; Wishnok, John S; Tannenbaum, Steven R

    2003-05-01

    The DNA damaging effects of nitrous acid have been extensively studied, and the formation of interstrand cross-links have been observed. The potential for this cross-linking to occur through a common nitrosating intermediate derived from nitric oxide is investigated here. Using a HPLC laser-induced fluorescence (LIF) system, the amount of interstrand cross-link formed on nitric oxide treatment of the 5'-fluorescein-labeled oligomer ATATCGATCGATAT was determined. This self-complimentary sequence contains two 5'-CG sequences, which is the preferred site for nitrous acid-induced cross-linking. Nitric oxide was delivered to an 0.5 mM oligomer solution at 15 nmol/mL/min to give a final nitrite concentration of 652 microM. The resulting concentration of the deamination product, xanthine, in this sample was found to be 211 +/- 39 nM, using GC/MS, and the amount of interstrand cross-link was determined to be 13 +/- 2.5 nM. Therefore, upon nitric oxide treatment, the cross-link is found at approximately 6% of the amount of the deamination product. Using this system, detection of the cross-link is also possible for significantly lower doses of nitric oxide, as demonstrated by treatment of the same oligomer with NO at a rate of 18 nmol/mL/min resulting in a final nitrite concentration of 126 microM. The concentration of interstrand cross-link was determined to be 3.6 +/- 0.1 nM in this sample. Therefore, using the same dose rate, when the total nitric oxide concentration delivered drops by a factor of approximately 5, the concentration of cross-link drops by a factor of about 4-indicating a qausi-linear response. It may now be possible to predict the number of cross-links in a small genome based on the number of CpG sequences and the yield of xanthine derived from nitrosative deamination.

  12. In vitro evaluation of crosslinked electrospun fish gelatin scaffolds

    International Nuclear Information System (INIS)

    Gomes, S.R.; Rodrigues, G.; Martins, G.G.; Henriques, C.M.R.; Silva, J.C.

    2013-01-01

    Gelatin from cold water fish skin was electrospun, crosslinked and investigated as a substrate for the adhesion and proliferation of cells. Gelatin was first dissolved in either water or concentrated acetic acid and both solutions were successfully electrospun. Cross-linking was achieved via three different routes: glutaraldehyde vapor, genipin and dehydrothermal treatment. Solution's properties (surface tension, electrical conductivity and viscosity) and scaffold's properties (chemical bonds, weight loss and fiber diameters) were measured. Cellular viability was analyzed culturing 3T3 fibroblasts plated on the scaffolds and grown up to 7 days. The cells were fixed and observed with SEM or stained for DNA and F-actin and observed with confocal microscopy. In all scaffolds, the cells attached and spread with varying degrees. The evaluation of cell viability showed proliferation of cells until confluence in scaffolds crosslinked by glutaraldehyde and genipin; however the rate of growth in genipin crosslinked scaffolds was slow, recovering only by day five. The results using the dehydrothermal treatment were the less satisfactory. Our results show that glutaraldehyde treated fish gelatin is the most suitable substrate, of the three studied, for fibroblast adhesion and proliferation. - Highlights: ► Electrospinning of fish gelatin dissolved in both water or concentrated acetic acid ► Glutaraldehyde, genipin and dehydrothermal treatment effectively crosslink the fish gelatin fibers ► Fibroblasts effectively adhere to and propagate on all scaffolds ► Cell population is highest for glutaraldehyde crosslinked scaffolds ► Cells exhibit more filopodia and stress fibers on glutaraldehyde crosslinked scaffolds

  13. In vitro evaluation of crosslinked electrospun fish gelatin scaffolds

    Energy Technology Data Exchange (ETDEWEB)

    Gomes, S.R. [Centro de Física e Investigação Tecnológica / Departamento de Física, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Rodrigues, G.; Martins, G.G. [Centro de Biologia Ambiental / Departamento de Biologia Animal, Faculdade de Ciências da Universidade de Lisboa, FCUL, 1749-016 Campo Grande, Lisboa (Portugal); Henriques, C.M.R. [Centro de Física e Investigação Tecnológica / Departamento de Física, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Silva, J.C., E-mail: jcs@fct.unl.pt [Centro de Física e Investigação Tecnológica / Departamento de Física, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal)

    2013-04-01

    Gelatin from cold water fish skin was electrospun, crosslinked and investigated as a substrate for the adhesion and proliferation of cells. Gelatin was first dissolved in either water or concentrated acetic acid and both solutions were successfully electrospun. Cross-linking was achieved via three different routes: glutaraldehyde vapor, genipin and dehydrothermal treatment. Solution's properties (surface tension, electrical conductivity and viscosity) and scaffold's properties (chemical bonds, weight loss and fiber diameters) were measured. Cellular viability was analyzed culturing 3T3 fibroblasts plated on the scaffolds and grown up to 7 days. The cells were fixed and observed with SEM or stained for DNA and F-actin and observed with confocal microscopy. In all scaffolds, the cells attached and spread with varying degrees. The evaluation of cell viability showed proliferation of cells until confluence in scaffolds crosslinked by glutaraldehyde and genipin; however the rate of growth in genipin crosslinked scaffolds was slow, recovering only by day five. The results using the dehydrothermal treatment were the less satisfactory. Our results show that glutaraldehyde treated fish gelatin is the most suitable substrate, of the three studied, for fibroblast adhesion and proliferation. - Highlights: ► Electrospinning of fish gelatin dissolved in both water or concentrated acetic acid ► Glutaraldehyde, genipin and dehydrothermal treatment effectively crosslink the fish gelatin fibers ► Fibroblasts effectively adhere to and propagate on all scaffolds ► Cell population is highest for glutaraldehyde crosslinked scaffolds ► Cells exhibit more filopodia and stress fibers on glutaraldehyde crosslinked scaffolds.

  14. Properties of crosslinked ultra-high-molecular-weight polyethylene.

    Science.gov (United States)

    Lewis, G

    2001-02-01

    Substantially reducing the rate of generation of wear particles at the surfaces of ultra-high-molecular-weight polyethylene (UHMWPE) orthopedic implant bearing components, in vivo, is widely regarded as one of the most formidable challenges in modern arthroplasty. In the light of this, much research attention has been paid to the myriad of endogenous and exogenous factors that have been postulated to affect this wear rate, one such factor being the polymer itself. In recent years, there has been a resurgence of interest in crosslinking the polymer as a way of improving its properties that are considered relevant to its use for fabricating bearing components. Such properties include wear resistance, fatigue life, and fatigue crack propagation rate. Although a large volume of literature exists on the topic on the impact of crosslinking on the properties of UHMWPE, no critical appraisal of this literature has been published. This is one of the goals of the present article, which emphasizes three aspects. The first is the trade-off between improvement in wear resistance and depreciation in other mechanical and physical properties. The second aspect is the presentation of a method of estimating the optimal value of a crosslinking process variable (such as dose in radiation-induced crosslinking) that takes into account this trade-off. The third aspect is the description of a collection of under- and unexplored research areas in the field of crosslinked UHMWPE, such as the role of starting resin on the properties of the crosslinked polymer, and the in vitro evaluation of the wear rate of crosslinked tibial inserts and other bearing components that, in vivo, are subjected to nearly unidirectional motion.

  15. Proceedings of a one-week course on exploiting anomalous scattering in macromolecular structure determination (EMBO'07)

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, M.S.; Shepard, W.; Dauter, Z.; Leslie, A.; Diederichs, K.; Evans, G.; Svensson, O.; Schneider, T.; Bricogne, G.; Dauter, Z.; Flensburg, C.; Terwilliger, T.; Lamzin, V.; Leslie, A.; Kabsch, W.; Flensburg, C.; Terwilliger, T.; Lamzin, V.; Read, R.; Panjikar, S.; Pannu, N.S.; Dauter, Z.; Weiss, M.S.; McSweeney, S

    2007-07-01

    This course, which was directed to young scientists, illustrated both theoretical and practical aspects of macromolecular crystal structure solution using synchrotron radiation. Some software dedicated to data collection, processing and analysis were presented. This document gathers only the slides of the presentations.

  16. Macromolecular crowding compacts unfolded apoflavodoxin and causes severe aggregation of the off-pathway intermediate during apoflavodoxin folding

    NARCIS (Netherlands)

    Engel, R.; Westphal, A.H.; Huberts, D.; Nabuurs, S.M.; Lindhoud, S.; Visser, A.J.W.G.; Mierlo, van C.P.M.

    2008-01-01

    To understand how proteins fold in vivo, it is important to investigate the effects of macromolecular crowding on protein folding. Here, the influence of crowding on in vitro apoflavodoxin folding, which involves a relatively stable off-pathway intermediate with molten globule characteristics, is

  17. Proceedings of a one-week course on exploiting anomalous scattering in macromolecular structure determination (EMBO'07)

    International Nuclear Information System (INIS)

    Weiss, M.S.; Shepard, W.; Dauter, Z.; Leslie, A.; Diederichs, K.; Evans, G.; Svensson, O.; Schneider, T.; Bricogne, G.; Dauter, Z.; Flensburg, C.; Terwilliger, T.; Lamzin, V.; Leslie, A.; Kabsch, W.; Flensburg, C.; Terwilliger, T.; Lamzin, V.; Read, R.; Panjikar, S.; Pannu, N.S.; Dauter, Z.; Weiss, M.S.; McSweeney, S.

    2007-01-01

    This course, which was directed to young scientists, illustrated both theoretical and practical aspects of macromolecular crystal structure solution using synchrotron radiation. Some software dedicated to data collection, processing and analysis were presented. This document gathers only the slides of the presentations

  18. Probing the Interplay of Size, Shape, and Solution Environment in Macromolecular Diffusion Using a Simple Refraction Experiment

    Science.gov (United States)

    Mankidy, Bijith D.; Coutinho, Cecil A.; Gupta, Vinay K.

    2010-01-01

    The diffusion coefficient of polymers is a critical parameter in biomedicine, catalysis, chemical separations, nanotechnology, and other industrial applications. Here, measurement of macromolecular diffusion in solutions is described using a visually instructive, undergraduate-level optical refraction experiment based on Weiner's method. To…

  19. Proceedings of a one-week course on exploiting anomalous scattering in macromolecular structure determination (EMBO'07)

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, M S; Shepard, W; Dauter, Z; Leslie, A; Diederichs, K; Evans, G; Svensson, O; Schneider, T; Bricogne, G; Dauter, Z; Flensburg, C; Terwilliger, T; Lamzin, V; Leslie, A; Kabsch, W; Flensburg, C; Terwilliger, T; Lamzin, V; Read, R; Panjikar, S; Pannu, N S; Dauter, Z; Weiss, M S; McSweeney, S

    2007-07-01

    This course, which was directed to young scientists, illustrated both theoretical and practical aspects of macromolecular crystal structure solution using synchrotron radiation. Some software dedicated to data collection, processing and analysis were presented. This document gathers only the slides of the presentations.

  20. A Test of Macromolecular Crystallization in Microgravity: Large, Well-Ordered Insulin Crystals

    Science.gov (United States)

    Borgstahl, Gloria E. O.; Vahedi-Faridi, Ardeschir; Lovelace, Jeff; Bellamy, Henry D.; Snell, Edward H.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Crystals of insulin grown in microgravity on space shuttle mission STS-95 were extremely well-ordered and unusually large (many > 2 mm). The physical characteristics of six microgravity and six earth-grown crystals were examined by X-ray analysis employing superfine f slicing and unfocused synchrotron radiation. This experimental setup allowed hundreds of reflections to be precisely examined for each crystal in a short period of time. The microgravity crystals were on average 34 times larger, had 7 times lower mosaicity, had 54 times higher reflection peak heights and diffracted to significantly higher resolution than their earth grown counterparts. A single mosaic domain model could account for reflections in microgravity crystals whereas reflections from earth crystals required a model with multiple mosaic domains. This statistically significant and unbiased characterization indicates that the microgravity environment was useful for the improvement of crystal growth and resultant diffraction quality in insulin crystals and may be similarly useful for macromolecular crystals in general.

  1. Acoustic methods for high-throughput protein crystal mounting at next-generation macromolecular crystallographic beamlines.

    Science.gov (United States)

    Roessler, Christian G; Kuczewski, Anthony; Stearns, Richard; Ellson, Richard; Olechno, Joseph; Orville, Allen M; Allaire, Marc; Soares, Alexei S; Héroux, Annie

    2013-09-01

    To take full advantage of advanced data collection techniques and high beam flux at next-generation macromolecular crystallography beamlines, rapid and reliable methods will be needed to mount and align many samples per second. One approach is to use an acoustic ejector to eject crystal-containing droplets onto a solid X-ray transparent surface, which can then be positioned and rotated for data collection. Proof-of-concept experiments were conducted at the National Synchrotron Light Source on thermolysin crystals acoustically ejected onto a polyimide `conveyor belt'. Small wedges of data were collected on each crystal, and a complete dataset was assembled from a well diffracting subset of these crystals. Future developments and implementation will focus on achieving ejection and translation of single droplets at a rate of over one hundred per second.

  2. Proteome-wide dataset supporting the study of ancient metazoan macromolecular complexes

    Directory of Open Access Journals (Sweden)

    Sadhna Phanse

    2016-03-01

    Full Text Available Our analysis examines the conservation of multiprotein complexes among metazoa through use of high resolution biochemical fractionation and precision mass spectrometry applied to soluble cell extracts from 5 representative model organisms Caenorhabditis elegans, Drosophila melanogaster, Mus musculus, Strongylocentrotus purpuratus, and Homo sapiens. The interaction network obtained from the data was validated globally in 4 distant species (Xenopus laevis, Nematostella vectensis, Dictyostelium discoideum, Saccharomyces cerevisiae and locally by targeted affinity-purification experiments. Here we provide details of our massive set of supporting biochemical fractionation data available via ProteomeXchange (http://www.ebi.ac.uk/pride/archive/projects/PXD002319-http://www.ebi.ac.uk/pride/archive/projects/PXD002328, PPIs via BioGRID (185267; and interaction network projections via (http://metazoa.med.utoronto.ca made fully accessible to allow further exploration. The datasets here are related to the research article on metazoan macromolecular complexes in Nature [1]. Keywords: Proteomics, Metazoa, Protein complexes, Biochemical, Fractionation

  3. Functionalization of Planet-Satellite Nanostructures Revealed by Nanoscopic Localization of Distinct Macromolecular Species

    KAUST Repository

    Rossner, Christian

    2016-09-26

    The development of a straightforward method is reported to form hybrid polymer/gold planet-satellite nanostructures (PlSNs) with functional polymer. Polyacrylate type polymer with benzyl chloride in its backbone as a macromolecular tracer is synthesized to study its localization within PlSNs by analyzing the elemental distribution of chlorine. The functionalized nanohybrid structures are analyzed by scanning transmission electron microscopy, electron energy loss spectroscopy, and spectrum imaging. The results show that the RAFT (reversible addition-fragmentation chain transfer) polymers\\' sulfur containing end groups are colocalized at the gold cores, both within nanohybrids of simple core-shell morphology and within higher order PlSNs, providing microscopic evidence for the affinity of the RAFT group toward gold surfaces. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA., Weinheim.

  4. Integration and global analysis of isothermal titration calorimetry data for studying macromolecular interactions.

    Science.gov (United States)

    Brautigam, Chad A; Zhao, Huaying; Vargas, Carolyn; Keller, Sandro; Schuck, Peter

    2016-05-01

    Isothermal titration calorimetry (ITC) is a powerful and widely used method to measure the energetics of macromolecular interactions by recording a thermogram of differential heating power during a titration. However, traditional ITC analysis is limited by stochastic thermogram noise and by the limited information content of a single titration experiment. Here we present a protocol for bias-free thermogram integration based on automated shape analysis of the injection peaks, followed by combination of isotherms from different calorimetric titration experiments into a global analysis, statistical analysis of binding parameters and graphical presentation of the results. This is performed using the integrated public-domain software packages NITPIC, SEDPHAT and GUSSI. The recently developed low-noise thermogram integration approach and global analysis allow for more precise parameter estimates and more reliable quantification of multisite and multicomponent cooperative and competitive interactions. Titration experiments typically take 1-2.5 h each, and global analysis usually takes 10-20 min.

  5. Recent Major Improvements to the ALS Sector 5 Macromolecular Crystallography Beamlines

    International Nuclear Information System (INIS)

    Morton, Simon A.; Glossinger, James; Smith-Baumann, Alexis; McKean, John P.; Trame, Christine; Dickert, Jeff; Rozales, Anthony; Dauz, Azer; Taylor, John; Zwart, Petrus; Duarte, Robert; Padmore, Howard; McDermott, Gerry; Adams, Paul

    2007-01-01

    Although the Advanced Light Source (ALS) was initially conceived primarily as a low energy (1.9GeV) 3rd generation source of VUV and soft x-ray radiation it was realized very early in the development of the facility that a multipole wiggler source coupled with high quality, (brightness preserving), optics would result in a beamline whose performance across the optimal energy range (5-15keV) for macromolecular crystallography (MX) would be comparable to, or even exceed, that of many existing crystallography beamlines at higher energy facilities. Hence, starting in 1996, a suite of three beamlines, branching off a single wiggler source, was constructed, which together formed the ALS Macromolecular Crystallography Facility. From the outset this facility was designed to cater equally to the needs of both academic and industrial users with a heavy emphasis placed on the development and introduction of high throughput crystallographic tools, techniques, and facilities--such as large area CCD detectors, robotic sample handling and automounting facilities, a service crystallography program, and a tightly integrated, centralized, and highly automated beamline control environment for users. This facility was immediately successful, with the primary Multiwavelength Anomalous Diffraction beamline (5.0.2) in particular rapidly becoming one of the foremost crystallographic facilities in the US--responsible for structures such as the 70S ribosome. This success in-turn triggered enormous growth of the ALS macromolecular crystallography community and spurred the development of five additional ALS MX beamlines all utilizing the newly developed superconducting bending magnets ('superbends') as sources. However in the years since the original Sector 5.0 beamlines were built the performance demands of macromolecular crystallography users have become ever more exacting; with growing emphasis placed on studying larger complexes, more difficult structures, weakly diffracting or smaller

  6. Mix and Inject: Reaction Initiation by Diffusion for Time-Resolved Macromolecular Crystallography

    Directory of Open Access Journals (Sweden)

    Marius Schmidt

    2013-01-01

    Full Text Available Time-resolved macromolecular crystallography unifies structure determination with chemical kinetics, since the structures of transient states and chemical and kinetic mechanisms can be determined simultaneously from the same data. To start a reaction in an enzyme, typically, an initially inactive substrate present in the crystal is activated. This has particular disadvantages that are circumvented when active substrate is directly provided by diffusion. However, then it is prohibitive to use macroscopic crystals because diffusion times become too long. With small micro- and nanocrystals diffusion times are adequately short for most enzymes and the reaction can be swiftly initiated. We demonstrate here that a time-resolved crystallographic experiment becomes feasible by mixing substrate with enzyme nanocrystals which are subsequently injected into the X-ray beam of a pulsed X-ray source.

  7. OCTOPUS: an innovative multimodal diffractometer for neutron macromolecular crystallography across the length scales

    International Nuclear Information System (INIS)

    Blakeley, M.P.; Andersen, K.; Kreuz, M.; Giroud, B.; McSweeney, S.; Mitchell, E.; Teixeira, S.C.M.; Forsyth, V.T.

    2011-01-01

    We propose to construct a novel protein diffractometer at position H112B. The new instrument will deliver major efficiency gains, as well as offering greatly extended flexibility through the option of several easily interchangeable modes of operation. This proposal builds on the demonstrable need to extend ILL's capacity for high resolution structural studies of protein systems, as well as a need to widen the scope of biological crystallography - in particular for monochromatic studies at both high and low resolution. The development will be carried out in close collaboration with structural biologists at the ESRF, and engineered in such a way that the user interface of the instrument (from sample to software) will be transparently identifiable to a large, dynamic, and driven community of European synchrotron X-ray macromolecular crystallographers. (authors)

  8. C1 Polymerization: a unique tool towards polyethylene-based complex macromolecular architectures

    KAUST Repository

    Wang, De

    2017-05-09

    The recent developments in organoborane initiated C1 polymerization (chain grows by one atom at a time) of ylides opens unique horizons towards well-defined/perfectly linear polymethylenes (equivalent to polyethylenes, PE) and PE-based complex macromolecular architectures. The general mechanism of C1 polymerization (polyhomologation) involves the formation of a Lewis complex between a methylide (monomer) and a borane (initiator), followed by migration/insertion of a methylene into the initiator and after oxidation/hydrolysis to afford OH-terminated polyethylenes. This review summarizes efforts towards conventional and newly discovered borane-initiators and ylides (monomers), as well as a combination of polyhomologation with other polymerization methods. Initial efforts dealing with C3 polymerization and the synthesis of the first C1/C3 copolymers are also given. Finally, some thoughts for the future of these polymerizations are presented.

  9. Control and data acquisition system for the macromolecular crystallography beamline of SSRF

    International Nuclear Information System (INIS)

    Wang Qisheng; Huang Sheng; Sun Bo; Tang Lin; He Jianhua

    2012-01-01

    The macromolecular crystallography beamline BL17U1 of Shanghai Synchrotron Radiation Facility (SSRF) is an important platform for structure biological science. High performance of the beamline would benefit the users greatly in their experiment and data acquisition. To take full advantage of the state-of-the-art mechanical and physical design of the beamline, we have made a series of efforts to develop a robust control and data acquisition system, with user-friendly GUI. These were done by adopting EPICS and Blu-Ice systems on the BL17U1 beamline, with considerations on easy accommodation of new beeline components. In this paper, we report the integration of EPICS and Blu-Ice systems. By using the EPICS gateway interface and several new DHS, Blu-Ice was successfully established for the BL17U1 beamline. As a result, the experiment control and data acquisition system is reliable and functional for users. (authors)

  10. Reliable and efficient solution of genome-scale models of Metabolism and macromolecular Expression

    DEFF Research Database (Denmark)

    Ma, Ding; Yang, Laurence; Fleming, Ronan M. T.

    2017-01-01

    orders of magnitude. Data values also have greatly varying magnitudes. Standard double-precision solvers may return inaccurate solutions or report that no solution exists. Exact simplex solvers based on rational arithmetic require a near-optimal warm start to be practical on large problems (current ME......Constraint-Based Reconstruction and Analysis (COBRA) is currently the only methodology that permits integrated modeling of Metabolism and macromolecular Expression (ME) at genome-scale. Linear optimization computes steady-state flux solutions to ME models, but flux values are spread over many...... models have 70,000 constraints and variables and will grow larger). We have developed a quadrupleprecision version of our linear and nonlinear optimizer MINOS, and a solution procedure (DQQ) involving Double and Quad MINOS that achieves reliability and efficiency for ME models and other challenging...

  11. Site-selective electroless nickel plating on patterned thin films of macromolecular metal complexes.

    Science.gov (United States)

    Kimura, Mutsumi; Yamagiwa, Hiroki; Asakawa, Daisuke; Noguchi, Makoto; Kurashina, Tadashi; Fukawa, Tadashi; Shirai, Hirofusa

    2010-12-01

    We demonstrate a simple route to depositing nickel layer patterns using photocross-linked polymer thin films containing palladium catalysts, which can be used as adhesive interlayers for fabrication of nickel patterns on glass and plastic substrates. Electroless nickel patterns can be obtained in three steps: (i) the pattern formation of partially quaterized poly(vinyl pyridine) by UV irradiation, (ii) the formation of macromolecular metal complex with palladium, and (iii) the nickel metallization using electroless plating bath. Metallization is site-selective and allows for a high resolution. And the resulting nickel layered structure shows good adhesion with glass and plastic substrates. The direct patterning of metallic layers onto insulating substrates indicates a great potential for fabricating micro/nano devices.

  12. Structure, function and folding of phosphoglycerate kinase are strongly perturbed by macromolecular crowding.

    Science.gov (United States)

    Samiotakis, Antonios; Dhar, Apratim; Ebbinghaus, Simon; Nienhaus, Lea; Homouz, Dirar; Gruebele, Martin; Cheung, Margaret

    2010-10-01

    We combine experiment and computer simulation to show how macromolecular crowding dramatically affects the structure, function and folding landscape of phosphoglycerate kinase (PGK). Fluorescence labeling shows that compact states of yeast PGK are populated as the amount of crowding agents (Ficoll 70) increases. Coarse-grained molecular simulations reveal three compact ensembles: C (crystal structure), CC (collapsed crystal) and Sph (spherical compact). With an adjustment for viscosity, crowded wild type PGK and fluorescent PGK are about 15 times or more active in 200 mg/ml Ficoll than in aqueous solution. Our results suggest a new solution to the classic problem of how the ADP and diphosphoglycerate binding sites of PGK come together to make ATP: rather than undergoing a hinge motion, the ADP and substrate sites are already located in proximity under crowded conditions that mimic the in vivo conditions under which the enzyme actually operates.

  13. Macromolecular contrast media. A new approach for characterising breast tumors with MR-mammography

    International Nuclear Information System (INIS)

    Daldrup, H.E.; Gossmann, A.; Koeln Univ.; Wendland, M.; Brasch, R.C.; Rosenau, W.

    1997-01-01

    The value of macromolecular contrast agents (MMCM) for the characterization of benign and malignant breast tumors will be demonstrated in this review. Animal studies suggest a high potential of MMCM to increase the specificity of MR-mammography. The concept of tumor differentiation is based on the pathological hyperpermeability of microvessels in malignant tumors. MMCM show a leak into the interstitium of carcinomas, whereas they are confined to the intravascular space in benign tumors. Capabilities and limitations of the MMCM-prototype. Albumin-Gd-DTPA, for breast tumor characterization will be summarized and compared to the standard low molecular weight contrast agent Gd-DTPA. Initial experience with new MMCM, such as Dendrimers, Gd-DTPA-Polylysine and MS-325 will be outlined. The potential of 'blood-pool'-iron oxides, such as AMI-227 for the evaluation of tumor microvascular permeabilities will be discussed. (orig.) [de

  14. DA+ data acquisition and analysis software at the Swiss Light Source macromolecular crystallography beamlines.

    Science.gov (United States)

    Wojdyla, Justyna Aleksandra; Kaminski, Jakub W; Panepucci, Ezequiel; Ebner, Simon; Wang, Xiaoqiang; Gabadinho, Jose; Wang, Meitian

    2018-01-01

    Data acquisition software is an essential component of modern macromolecular crystallography (MX) beamlines, enabling efficient use of beam time at synchrotron facilities. Developed at the Paul Scherrer Institute, the DA+ data acquisition software is implemented at all three Swiss Light Source (SLS) MX beamlines. DA+ consists of distributed services and components written in Python and Java, which communicate via messaging and streaming technologies. The major components of DA+ are the user interface, acquisition engine, online processing and database. Immediate data quality feedback is achieved with distributed automatic data analysis routines. The software architecture enables exploration of the full potential of the latest instrumentation at the SLS MX beamlines, such as the SmarGon goniometer and the EIGER X 16M detector, and development of new data collection methods.

  15. C1 Polymerization: a unique tool towards polyethylene-based complex macromolecular architectures

    KAUST Repository

    Wang, De; Zhang, Zhen; Hadjichristidis, Nikolaos

    2017-01-01

    The recent developments in organoborane initiated C1 polymerization (chain grows by one atom at a time) of ylides opens unique horizons towards well-defined/perfectly linear polymethylenes (equivalent to polyethylenes, PE) and PE-based complex macromolecular architectures. The general mechanism of C1 polymerization (polyhomologation) involves the formation of a Lewis complex between a methylide (monomer) and a borane (initiator), followed by migration/insertion of a methylene into the initiator and after oxidation/hydrolysis to afford OH-terminated polyethylenes. This review summarizes efforts towards conventional and newly discovered borane-initiators and ylides (monomers), as well as a combination of polyhomologation with other polymerization methods. Initial efforts dealing with C3 polymerization and the synthesis of the first C1/C3 copolymers are also given. Finally, some thoughts for the future of these polymerizations are presented.

  16. Mechano-responsive hydrogels crosslinked by reactive block copolymer micelles

    Science.gov (United States)

    Xiao, Longxi

    Hydrogels are crosslinked polymeric networks that can swell in water without dissolution. Owing to their structural similarity to the native extracelluar matrices, hydrogels have been widely used in biomedical applications. Synthetic hydrogels have been designed to respond to various stimuli, but mechanical signals have not incorporated into hydrogel matrices. Because most tissues in the body are subjected to various types of mechanical forces, and cells within these tissues have sophisticated mechano-transduction machinery, this thesis is focused on developing hydrogel materials with built-in mechano-sensing mechanisms for use as tissue engineering scaffolds or drug release devices. Self-assembled block copolymer micelles (BCMs) with reactive handles were employed as the nanoscopic crosslinkers for the construction of covalently crosslinked networks. BCMs were assembled from amphiphilic diblock copolymers of poly(n-butyl acrylate) and poly(acrylic acid) partially modified with acrylate. Radical polymerization of acrylamide in the presence of micellar crosslinkers gave rise to elastomeric hydrogels whose mechanical properties can be tuned by varying the BCM composition and concentration. TEM imaging revealed that the covalently integrated BCMs underwent strain-dependent reversible deformation. A model hydrophobic drug, pyrene, loaded into the core of BCMs prior to the hydrogel formation, was dynamically released in response to externally applied mechanical forces, through force-induced reversible micelle deformation and the penetration of water molecules into the micelle core. The mechano-responsive hydrogel has been studied for tissue repair and regeneration purposes. Glycidyl methacrylate (GMA)-modified hyaluronic acid (HA) was photochemically crosslinked in the presence of dexamethasone (DEX)-loaded crosslinkable BCMs. The resultant HA gels (HAxBCM) contain covalently integrated micellar compartments with DEX being sequestered in the hydrophobic core. Compared

  17. A 3D Image Filter for Parameter-Free Segmentation of Macromolecular Structures from Electron Tomograms

    Science.gov (United States)

    Ali, Rubbiya A.; Landsberg, Michael J.; Knauth, Emily; Morgan, Garry P.; Marsh, Brad J.; Hankamer, Ben

    2012-01-01

    3D image reconstruction of large cellular volumes by electron tomography (ET) at high (≤5 nm) resolution can now routinely resolve organellar and compartmental membrane structures, protein coats, cytoskeletal filaments, and macromolecules. However, current image analysis methods for identifying in situ macromolecular structures within the crowded 3D ultrastructural landscape of a cell remain labor-intensive, time-consuming, and prone to user-bias and/or error. This paper demonstrates the development and application of a parameter-free, 3D implementation of the bilateral edge-detection (BLE) algorithm for the rapid and accurate segmentation of cellular tomograms. The performance of the 3D BLE filter has been tested on a range of synthetic and real biological data sets and validated against current leading filters—the pseudo 3D recursive and Canny filters. The performance of the 3D BLE filter was found to be comparable to or better than that of both the 3D recursive and Canny filters while offering the significant advantage that it requires no parameter input or optimisation. Edge widths as little as 2 pixels are reproducibly detected with signal intensity and grey scale values as low as 0.72% above the mean of the background noise. The 3D BLE thus provides an efficient method for the automated segmentation of complex cellular structures across multiple scales for further downstream processing, such as cellular annotation and sub-tomogram averaging, and provides a valuable tool for the accurate and high-throughput identification and annotation of 3D structural complexity at the subcellular level, as well as for mapping the spatial and temporal rearrangement of macromolecular assemblies in situ within cellular tomograms. PMID:22479430

  18. Optimization of selective inversion recovery magnetization transfer imaging for macromolecular content mapping in the human brain.

    Science.gov (United States)

    Dortch, Richard D; Bagnato, Francesca; Gochberg, Daniel F; Gore, John C; Smith, Seth A

    2018-03-24

    To optimize a selective inversion recovery (SIR) sequence for macromolecular content mapping in the human brain at 3.0T. SIR is a quantitative method for measuring magnetization transfer (qMT) that uses a low-power, on-resonance inversion pulse. This results in a biexponential recovery of free water signal that can be sampled at various inversion/predelay times (t I/ t D ) to estimate a subset of qMT parameters, including the macromolecular-to-free pool-size-ratio (PSR), the R 1 of free water (R 1f ), and the rate of MT exchange (k mf ). The adoption of SIR has been limited by long acquisition times (≈4 min/slice). Here, we use Cramér-Rao lower bound theory and data reduction strategies to select optimal t I /t D combinations to reduce imaging times. The schemes were experimentally validated in phantoms, and tested in healthy volunteers (N = 4) and a multiple sclerosis patient. Two optimal sampling schemes were determined: (i) a 5-point scheme (k mf estimated) and (ii) a 4-point scheme (k mf assumed). In phantoms, the 5/4-point schemes yielded parameter estimates with similar SNRs as our previous 16-point scheme, but with 4.1/6.1-fold shorter scan times. Pair-wise comparisons between schemes did not detect significant differences for any scheme/parameter. In humans, parameter values were consistent with published values, and similar levels of precision were obtained from all schemes. Furthermore, fixing k mf reduced the sensitivity of PSR to partial-volume averaging, yielding more consistent estimates throughout the brain. qMT parameters can be robustly estimated in ≤1 min/slice (without independent measures of ΔB 0 , B1+, and T 1 ) when optimized t I -t D combinations are selected. © 2018 International Society for Magnetic Resonance in Medicine.

  19. Macromolecular composition of terrestrial and marine organic matter in sediments across the East Siberian Arctic Shelf

    Science.gov (United States)

    Sparkes, Robert B.; Doğrul Selver, Ayça; Gustafsson, Örjan; Semiletov, Igor P.; Haghipour, Negar; Wacker, Lukas; Eglinton, Timothy I.; Talbot, Helen M.; van Dongen, Bart E.

    2016-10-01

    Mobilisation of terrestrial organic carbon (terrOC) from permafrost environments in eastern Siberia has the potential to deliver significant amounts of carbon to the Arctic Ocean, via both fluvial and coastal erosion. Eroded terrOC can be degraded during offshore transport or deposited across the wide East Siberian Arctic Shelf (ESAS). Most studies of terrOC on the ESAS have concentrated on solvent-extractable organic matter, but this represents only a small proportion of the total terrOC load. In this study we have used pyrolysis-gas chromatography-mass spectrometry (py-GCMS) to study all major groups of macromolecular components of the terrOC; this is the first time that this technique has been applied to the ESAS. This has shown that there is a strong offshore trend from terrestrial phenols, aromatics and cyclopentenones to marine pyridines. There is good agreement between proportion phenols measured using py-GCMS and independent quantification of lignin phenol concentrations (r2 = 0.67, p radiocarbon data for bulk OC (14COC) which, when coupled with previous measurements, allows us to produce the most comprehensive 14COC map of the ESAS to date. Combining the 14COC and py-GCMS data suggests that the aromatics group of compounds is likely sourced from old, aged terrOC, in contrast to the phenols group, which is likely sourced from modern woody material. We propose that an index of the relative proportions of phenols and pyridines can be used as a novel terrestrial vs. marine proxy measurement for macromolecular organic matter. Principal component analysis found that various terrestrial vs. marine proxies show different patterns across the ESAS, and it shows that multiple river-ocean transects of surface sediments transition from river-dominated to coastal-erosion-dominated to marine-dominated signatures.

  20. Development of an online UV–visible microspectrophotometer for a macromolecular crystallography beamline

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, Nobutaka, E-mail: nobutaka.shimizu@kek.jp [SPring-8/JASRI, 1-1-1 Koto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Shimizu, Tetsuya [RIKEN SPring-8 Center, 1-1-1 Koto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Baba, Seiki; Hasegawa, Kazuya [SPring-8/JASRI, 1-1-1 Koto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Yamamoto, Masaki [RIKEN SPring-8 Center, 1-1-1 Koto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Kumasaka, Takashi [SPring-8/JASRI, 1-1-1 Koto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan)

    2013-11-01

    An online UV–visible microspectrophotometer has been developed for the macromolecular crystallography beamline at SPring-8. Details of this spectrophotometer are reported. Measurement of the UV–visible absorption spectrum is a convenient technique for detecting chemical changes of proteins, and it is therefore useful to combine spectroscopy and diffraction studies. An online microspectrophotometer for the UV–visible region was developed and installed on the macromolecular crystallography beamline, BL38B1, at SPring-8. This spectrophotometer is equipped with a difference dispersive double monochromator, a mercury–xenon lamp as the light source, and a photomultiplier as the detector. The optical path is mostly constructed using mirrors, in order to obtain high brightness in the UV region, and the confocal optics are assembled using a cross-slit diaphragm like an iris to eliminate stray light. This system can measure optical densities up to a maximum of 4.0. To study the effect of radiation damage, preliminary measurements of glucose isomerase and thaumatin crystals were conducted in the UV region. Spectral changes dependent on X-ray dose were observed at around 280 nm, suggesting that structural changes involving Trp or Tyr residues occurred in the protein crystal. In the case of the thaumatin crystal, a broad peak around 400 nm was also generated after X-ray irradiation, suggesting the cleavage of a disulfide bond. Dose-dependent spectral changes were also observed in cryo-solutions alone, and these changes differed with the composition of the cryo-solution. These responses in the UV region are informative regarding the state of the sample; consequently, this device might be useful for X-ray crystallography.

  1. Development of new cross-linked polyethylene for atomic energy

    International Nuclear Information System (INIS)

    Fujimura, Shun-ichi; Ohya, Shingo; Kubo, Masaji; Tsutsumi, Yukihiro; Seguchi, Tadao.

    1988-01-01

    Cross-linked polyethylene is the material which is used most as the insulating material for electric wires and cables, but for the cables for nuclear power stations and the wiring materials within machinery and equipment, the cross-linked polyethylene which is hard to burn by mixing burning-retarding agent is frequently used as the disaster-preventing countermeasures. As the burning-retarding agent for cross-linked polyethylene, bromine system agent that gives high burning retardation, chlorine system agent that can prevent melting and dripping at the time of burning and so on have been used so as to meet the objective. However by the addition of burning-retarding agents, the electrical and mechanical characteristics of cross-linked polyethylene lower, therefore consideration must be given to the use. In this paper, the results of the examination on the application of condensed acenaphthylene bromide as a new burning-retarding agent to cross-linked polyethylene are reported. White lead was effective for catching HBr. It was confirmed that more than 30 parts of this agent ensured burning retardation. By mixing this agent, the tensile strength increased, but the elongation lowered. It was found that the good radiation resistance was obtained by adding this agent. (K.I.)

  2. Radiation cross-linked polymers: Recent developments and new applications

    International Nuclear Information System (INIS)

    Rouif, Sophie

    2005-01-01

    The purpose of the present paper is to review the innovative and recent applications of radiation cross-linking of polymers that reinforces their dimensional stability in chemically aggressive and high temperature conditions. Radiation cross-linking can be applied to a great number of plastics: thermoplastics, elastomers and thermoplastic elastomers (TPE). Some of them can cross-link on their own, some others need to be formulated with a cross-linking agent (promoter) or to be modified during their polymerization. Some results of chemical and thermomechanical characterizations of radiation cross-linked plastics based on engineering polymers will be described, and their advantages will be emphasized in relation with their applications in various sectors: pipes and cables, packaging, automotive, electrical engineering and electronics, including connectors, surface mounted devices, integrated circuits, 3D-MID technology, etc. The paper will conclude with a short review of the industrial irradiation facilities (EB facilities and gamma plants) adapted to the treatment of such various products

  3. Sorption characteristics of technetium on crosslinked chitosan from aqueous solution

    International Nuclear Information System (INIS)

    Pivarciova, L.; Rosskopfova, O.; Galambos, M.; Rajec, P.

    2014-01-01

    Sorption of technetium on crosslinked chitosan was studied using batch techniques in static arrangement of experiment under aerobic conditions at laboratory temperature. The adsorption of technetium was rapid and the percentage of the technetium sorption was > 98 %. In the pH range of 3-11 adsorption of technetium on crosslinked chitosan was > 98 %. The competition effect of Fe 3+ towards TcO 4 - sorption on crosslinked chitosan was stronger than the competition effect of other observed cations. The selectivity of crosslinked chitosan for these cations in solution with the concentration above 1·10 -3 mol·dm -3 was in the order Fe 3+ > Ca 2+ > Na + > Fe 2+ . The competition effect of (ClO 4 ) - towards TcO 4 - sorption was stronger than the competition effect of (SO 4 ) 2 - ions. From these results it can be expected that crosslinked chitosan could be a suitable sorbent for the immobilization of technetium in the liquid radioactive waste. (authors)

  4. Pulsed Light Accelerated Crosslinking versus Continuous Light Accelerated Crosslinking: One-Year Results

    Directory of Open Access Journals (Sweden)

    Cosimo Mazzotta

    2014-01-01

    Full Text Available Purpose. To compare functional results in two cohorts of patients undergoing epithelium-off pulsed (pl-ACXL and continuous light accelerated corneal collagen crosslinking (cl-ACXL with dextran-free riboflavin solution and high-fluence ultraviolet A irradiation. Design. It is a prospective, comparative, and interventional clinical study. Methods. 20 patients affected by progressive keratoconus were enrolled in the study. 10 eyes of 10 patients underwent an epithelium-off pl-ACXL by the KXL UV-A source (Avedro Inc., Waltham, MS, USA with 8 minutes (1 sec. on/1 sec. off of UV-A exposure at 30 mW/cm2 and energy dose of 7.2 J/cm2; 10 eyes of 10 patients underwent an epithelium-off cl-ACXL at 30 mW/cm2 for 4 minutes. Riboflavin 0.1% dextran-free solution was used for a 10-minutes corneal soaking. Patients underwent clinical examination of uncorrected distance visual acuity and corrected distance visual acuity (UDVA and CDVA, corneal topography and aberrometry (CSO EyeTop, Florence, Italy, corneal OCT optical pachymetry (Cirrus OCT, Zeiss Meditec, Jena, Germany, endothelial cells count (I-Conan Non Co Robot, and in vivo scanning laser confocal microscopy (Heidelberg, Germany at 1, 3, 6, and 12 months of follow-up. Results. Functional results one year after cl-ACXL and pl-ACXL demonstrated keratoconus stability in both groups. Functional outcomes were found to be better in epithelium-off pulsed light accelerated treatment together with showing a deeper stromal penetration. No endothelial damage was recorded during the follow-up in both groups. Conclusions. The study confirmed that oxygen represents the main driver of collagen crosslinking reaction. Pulsed light treatment optimized intraoperative oxygen availability improving postoperative functional outcomes compared with continuous light treatment.

  5. Superhydrophobic hybrid membranes by grafting arc-like macromolecular bridges on graphene sheets: Synthesis, characterization and properties

    Science.gov (United States)

    Mo, Zhao-Hua; Luo, Zheng; Huang, Qiang; Deng, Jian-Ping; Wu, Yi-Xian

    2018-05-01

    Grafting single end-tethered polymer chains on the surface of graphene is a conventional way to modify the surface properties of graphene oxide. However, grafting arc-like macromolecular bridges on graphene surfaces has been barely reported. Herein, a novel arc-like polydimethylsiloxane (PDMS) macromolecular bridges grafted graphene sheets (GO-g-Arc PDMS) was successfully synthesized via a confined interface reaction at 90 °C. Both the hydrophilic α- and ω-amino groups of linear hydrophobic NH2-PDMS-NH2 macromolecular chains rapidly reacted with epoxy and carboxyl groups on the surfaces of graphene oxide in water suspension to form arc-like PDMS macromolecular bridges on graphene sheets. The grafting density of arc-like PDMS bridges on graphene sheets can reach up to 0.80 mmol g-1 or 1.32 arc-like bridges per nm2 by this confined interface reaction. The water contact angle (WCA) of the hybrid membrane could be increased with increasing both the grafting density and content of covalent arc-like bridges architecture. The superhydrophobic hybrid membrane with a WCA of 153.4° was prepared by grinding of the above arc-like PDMS bridges grafted graphene hybrid, dispersing in ethanol and filtrating by organic filter membrane. This superhydrophobic hybrid membrane shows good self-cleaning and complete oil-water separation properties, which provides potential applications in anticontamination coating and oil-water separation. To the best of our knowledge, this is the first report on the synthesis of functional hybrid membranes by grafting arc-like PDMS macromolecular bridges on graphene sheets via a confined interface reaction.

  6. Chemical structure and physical properties of radiation-induced crosslinking of polytetrafluoroethylene

    International Nuclear Information System (INIS)

    Oshima, Akihiro; Ikeda, Shigetoshi; Katoh, Etsuko; Tabata, Yoneho

    2001-01-01

    The chemical structure and physical properties of polytetrafluoroethylene (PTFE) that has been crosslinked by radiation have been studied by various methods. It has been found that a Y-type crosslinking structure and a Y-type structure incorporating a double bond (modified Y-type) is formed in PTFE by radiation-crosslinking in the molten state. In addition, various types of double bond structures, excluding the crosslinking site, have been identified. The crosslinked PTFE has a good light transparency due to the loss of crystallites, whilst it retains the excellent properties of electrical insulation and heat resistance. The coefficient of abrasion and the permanent creep are also greatly improved by crosslinking

  7. Preparation and properties of silk sericin/cellulose cross-linking films

    Directory of Open Access Journals (Sweden)

    Wang Kunyan

    2017-01-01

    Full Text Available Silk sericin/cellulose cross-linked films were successfully prepared using glutaraldehyde as cross-linkinger. FTIR was applied to characterize the chemical structure of films. Cross-linked silk sericin film was found the peak intensity of FTIR for cross-linked film decreased markedly compared to pure silk sericin, which indicating cross-linking reaction has been occurred. The increasing value of swelling ratio also indicated the cross-linking has been happened. The cross-linking reaction increased the thermal decomposition temperature.

  8. Photo-crosslinkable polymers for fabrication of photonic multilayer sensors

    Science.gov (United States)

    Chiappelli, Maria; Hayward, Ryan C.

    2013-03-01

    We have used photo-crosslinkable polymers to fabricate photonic multilayer sensors. Benzophenone is utilized as a covalently incorporated pendent photo-crosslinker, providing a convenient means of fabricating multilayer films by sequential spin-coating and crosslinking processes. Colorimetric temperature sensors were designed from thermally-responsive, low-refractive index poly(N-isopropylacrylamide) (PNIPAM) and high-refractive index poly(para-methyl styrene) (P pMS). Copolymer chemistries and layer thicknesses were selected to provide robust multilayer sensors which show color changes across nearly the full visible spectrum due to changes in temperature of the hydrated film stack. We have characterized the uniformity and interfacial broadening within the multilayers, the kinetics of swelling and de-swelling, and the reversibility over multiple hydration/dehydration cycles. We also describe how the approach can be extended to alternative sensor designs through the ability to tailor each layer independently, as well as to additional stimuli by selecting alternative copolymer chemistries.

  9. Radiation cross-linked collagen/dextran dermal scaffolds: effects of dextran on cross-linking and degradation.

    Science.gov (United States)

    Zhang, Yaqing; Zhang, Xiangmei; Xu, Ling; Wei, Shicheng; Zhai, Maolin

    2015-01-01

    Ionizing radiation effectively cross-links collagen into network with enhanced anti-degradability and biocompatibility, while radiation-cross-linked collagen scaffold lacks flexibility, satisfactory surface appearance, and performs poor in cell penetration and ingrowth. To make the radiation-cross-linked collagen scaffold to serve as an ideal artificial dermis, dextran was incorporated into collagen. Scaffolds with the collagen/dextran (Col/Dex) ratios of 10/0, 7/3, and 5/5 were fabricated via (60)Co γ-irradiation cross-linking, followed by lyophilization. The morphology, microstructure, physicochemical, and biological properties were investigated. Compared with pure collagen, scaffolds with dextran demonstrated more porous appearance, enhanced hydrophilicity while the cross-linking density was lower with the consequence of larger pore size, higher water uptake, as well as reduced stiffness. Accelerated degradation was observed when dextran was incorporated in both the in vitro and in vivo assays, which led to earlier integration with cell and host tissue. The effect of dextran on degradation was ascribed to the decreased cross-linking density, looser microstructure, more porous and hydrophilic surface. Considering the better appearance, softness, moderate degradation rate due to controllable cross-linking degree and good biocompatibility as well, radiation-cross-linked collagen/dextran scaffolds are expected to serve as promising artificial dermal substitutes.

  10. Pathways and mechanisms for product release in the engineered haloalkane dehalogenases explored using classical and random acceleration molecular dynamics simulations

    Czech Academy of Sciences Publication Activity Database

    Klvana, M.; Pavlová, M.; Koudeláková, T.; Chaloupková, R.; Dvořák, P.; Prokop, Z.; Stsiapanava, A.; Kutý, Michal; Kutá-Smatanová, Ivana; Dohnálek, Jan; Kulhánek, P.; Damborský, J.

    2009-01-01

    Roč. 392, č. 5 (2009), s. 1339-1356 ISSN 0022-2836 R&D Projects: GA MŠk(CZ) LC06010 Institutional research plan: CEZ:AV0Z40500505; CEZ:AV0Z60870520 Keywords : haloalkane dehalogenase * product release * random acceleration molecular dynamics Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.871, year: 2009

  11. In vivo oxidation in remelted highly cross-linked retrievals.

    Science.gov (United States)

    Currier, B H; Van Citters, D W; Currier, J H; Collier, J P

    2010-10-20

    Elimination of free radicals to prevent oxidation has played a major role in the development and product differentiation of the latest generation of highly cross-linked ultra-high molecular weight polyethylene bearing materials. In the current study, we (1) examined oxidation in a series of retrieved remelted highly cross-linked ultra-high molecular weight polyethylene bearings from a number of device manufacturers and (2) compared the retrieval results with findings for shelf-stored control specimens. The hypothesis was that radiation-cross-linked remelted ultra-high molecular weight polyethylene would maintain oxidative stability in vivo comparable with the stability during shelf storage and in published laboratory aging tests. Fifty remelted highly cross-linked ultra-high molecular weight polyethylene acetabular liners and nineteen remelted highly cross-linked ultra-high molecular weight polyethylene tibial inserts were received after retrieval from twenty-one surgeons from across the U.S. Thirty-two of the retrievals had been in vivo for two years or more. Each was measured for oxidation with use of Fourier transform infrared spectroscopy. A control series of remelted highly cross-linked ultra-high molecular weight polyethylene acetabular liners from three manufacturers was analyzed with electron paramagnetic resonance spectroscopy to measure free radical content and with Fourier transform infrared spectroscopy to measure oxidation initially and after eight to nine years of shelf storage in air. The never-implanted, shelf-aged controls had no measurable free-radical content initially or after eight to nine years of shelf storage. The never-implanted controls showed no increase in oxidation during shelf storage. Oxidation measurements showed measurable oxidation in 22% of the retrieved remelted highly cross-linked liners and inserts after an average of two years in vivo. Because never-implanted remelted highly cross-linked ultra-high molecular weight

  12. Nanoporous Crosslinked Polyisoprene from Polyisoprene-Polydimethylsiloxane Block Copolymer

    DEFF Research Database (Denmark)

    Hansen, Michael Steffen; Vigild, Martin Etchells; Berg, Rolf Henrik

    2004-01-01

    The polyisoprene block of a polyisoprene-polydimethylsiloxane (PI-PDMS) diblock copolymer with 0.68 volume fraction of PI was tightly crosslinked with dicumylperoxide. The PDMS part of the obtained glassy material was subsequently quantitatively etched with anhydrous hydrogen fluoride or tetrabut......The polyisoprene block of a polyisoprene-polydimethylsiloxane (PI-PDMS) diblock copolymer with 0.68 volume fraction of PI was tightly crosslinked with dicumylperoxide. The PDMS part of the obtained glassy material was subsequently quantitatively etched with anhydrous hydrogen fluoride...

  13. Measurement of DNA-protein crosslinks in mammalian cells without X-irradiation

    International Nuclear Information System (INIS)

    Gantt, R.; Stephens, E.V.; Davis, S.R.

    1985-01-01

    To study the mechanisms of formation and repair of DNA-protein crosslinks in mammalian cells, the best general method to assay these lesions is the Kohn membrane alkaline elution procedure. Use of this sensitive technique requires the introduction of random strand breaks in the DNA by X-irradiation to reduce the very high molecular weight so that it elutes off the filter at an appropriate rate. This report describes an alternative method for fragmenting the DNA in the absence of X-irradiation equipment. Convenient reproducible elution rates of DNA from various mouse and human cells in culture without X-irradiation result from elution through polyvinyl chloride filters with 75 mM sodium hydroxide (0.33 ml/min) instead of the standard 20 mM EDTA-tetrapropylammonium hydroxide, pH 12.2 (0.03 to 0.04 ml/min). Dose-dependent retardation of the DNA elution was observed over the range 0 to 30 microM trans-platinum(II)diamminedichloride, and proteinase K treatment during cell lysis restored the elution rate to that of the untreated control cell DNA. In the absence of X-irradiation, this elution method measures DNA-protein crosslinks with higher sensitivity and equivalent reproducibility as the air-burst procedure

  14. Evaluation of nanohydroxyapaptite (nano-HA) coated epigallocatechin-3-gallate (EGCG) cross-linked collagen membranes.

    Science.gov (United States)

    Chu, Chenyu; Deng, Jia; Man, Yi; Qu, Yili

    2017-09-01

    ) and elastic modulus (EM) measurements. Then in 12 rats, 4 types of membranes were randomly applied to cover the rat calvarial defects. The animals were sacrificed at 8weeks. Histologic analyses were performed using Hematoxylin-eosin (H&E) staining and Masson's Trichrome stains. For statistical analysis, analysis of variance (ANOVA) followed by Tukey's multiple comparison tests was applied. HA nanoparticles were fairly well distributed nanoparticles among the collagen fibers on the nano-HA-modified EGCG-collagen membranes, with smoother surface. Moreover, collagen membranes with modifications all maintained their collagen backbone and the mechanical properties were enhanced by EGCG and nano-HA treatments. In addition, EGCG cross-linked collagen membranes with nano-HA coatings promoted bone regeneration. Nano-HA modified EGCG-collagen membranes can be utilized as a barrier membrane to enhance the bone regeneration in GBR surgeries. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. A review of crosslinked fracturing fluids prepared with produced water

    Directory of Open Access Journals (Sweden)

    Leiming Li

    2016-12-01

    Full Text Available The rapidly increasing implementations of oilfield technologies such as horizontal wells and multistage hydraulic fracturing, particularly in unconventional formations, have expanded the need for fresh water in many oilfield locations. In the meantime, it is costly for services companies and operators to properly dispose large volumes of produced water, generated annually at about 21 billion barrels in the United States alone. The high operating costs in obtaining fresh water and dealing with produced water have motivated scientists and engineers, especially in recent years, to use produced water in place of fresh water to formulate well treatment fluids. The objective of this brief review is to provide a summary of the up-to-date technologies of reusing oilfield produced water in preparations of a series of crosslinked fluids implemented mainly in hydraulic fracturing operations. The crosslinked fluids formulated with produced water include borate- and metal-crosslinked guar and derivatized guar fluids, as well as other types of crosslinked fluid systems such as crosslinked synthetic polymer fluids and crosslinked derivatized cellulose fluids. The borate-crosslinked guar fluids have been successfully formulated with produced water and used in oilfield operations with bottomhole temperatures up to about 250 °F. The produced water sources involved showed total dissolved solids (TDS up to about 115,000 mg/L and hardness up to about 11,000 mg/L. The metal-crosslinked guar fluids prepared with produced water were successfully used in wells at bottomhole temperatures up to about 250 °F, with produced water TDS up to about 300,000 mg/L and hardness up to about 44,000 mg/L. The Zr-crosslinked carboxymethyl hydroxypropyl guar (CMHPG fluids have been successfully made with produced water and implemented in operations with bottomhole temperatures at about 250+ °F, with produced water TDS up to about 280,000 mg/L and hardness up to about 91,000

  16. a study of the kinetic of synthesis and crosslinking of methylol ...

    African Journals Online (AJOL)

    Nurudeen

    The reaction was carried out in ... temperature of reaction medium reduced the time of formation and subsequent crosslinking to the ... The experiment was repeated using 3, 4, 5 and 6 ... increase the rate of the crosslinking in the formation of.

  17. Novel magnetic cross-linked lipase aggregates for improving the resolution of (R, S)-2-octanol.

    Science.gov (United States)

    Liu, Ying; Guo, Chen; Liu, Chun-Zhao

    2015-03-01

    Novel magnetic cross-linked lipase aggregates were fabricated by immobilizing the cross-linked lipase aggregates onto magnetic particles with a high number of -NH2 terminal groups using p-benzoquinone as the cross-linking agent. At the optimal fabrication conditions, 100% of immobilization efficiency and 139% of activity recovery of the magnetic cross-linked lipase aggregates were achieved. The magnetic cross-linked lipase aggregates were able to efficiently resolve (R, S)-2-octanol, and retained 100% activity and 100% enantioselectivity after 10 cycles of reuse, whereas the cross-linked lipase aggregates only retained about 50% activity and 70% enantioselectivity due to insufficient cross-linking. These results provide a great potential for industrial applications of the magnetic cross-linked lipase aggregates. © 2014 Wiley Periodicals, Inc.

  18. Permanent antistatic phthalocyanine/epoxy nanocomposites – Influence of crosslinking agent, solvent and processing temperature

    NARCIS (Netherlands)

    Yuan, M.; Brokken-Zijp, J.C.M.; With, de G.

    2010-01-01

    Cross-linked epoxy matrices containing small amounts of semi-conductive phthalocyanine (Phthalcon) nanoparticles were prepared using different crosslinking agents and processing temperatures. A starting mixture containing an optimum dispersion of these nanoparticles and with an almost equal and

  19. Stable and biocompatible genipin-inducing interlayer-crosslinked micelles for sustained drug release

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Yu; Zhang, Xiaojin, E-mail: zhangxj@cug.edu.cn [China University of Geosciences, Faculty of Materials Science and Chemistry (China)

    2017-05-15

    To develop the sustained drug release system, here we describe genipin-inducing interlayer-crosslinked micelles crosslinked via Schiff bases between the amines of amphiphilic linear-hyperbranched polymer poly(ethylene glycol)-branched polyethylenimine-poly(ε-caprolactone) (PEG-PEI-PCL) and genipin. The generation of Schiff bases was confirmed by the color changes and UV-Vis absorption spectra of polymeric micelles after adding genipin. The particle size, morphology, stability, in vitro cytotoxicity, drug loading capacity, and in vitro drug release behavior of crosslinked micelles as well as non-crosslinked micelles were characterized. The results indicated that genipin-inducing interlayer-crosslinked micelles had better stability and biocompatibility than non-crosslinked micelles and glutaraldehyde-inducing interlayer-crosslinked micelles. In addition, genipin-inducing interlayer-crosslinked micelles were able to improve drug loading capacity, reduce the initial burst release, and achieve sustained drug release.

  20. Effects of Supercritical CO 2 Conditioning on Cross-Linked Polyimide Membranes

    KAUST Repository

    Kratochvil, Adam M.; Koros, William J.

    2010-01-01

    The effects of supercritical CO2 (scCO2) conditioning on high-performance cross-linked polyimide membranes is examined through gas permeation and sorption experiments. Under supercritical conditions, the cross-linked polymers do not exhibit a

  1. AutoDrug: fully automated macromolecular crystallography workflows for fragment-based drug discovery

    International Nuclear Information System (INIS)

    Tsai, Yingssu; McPhillips, Scott E.; González, Ana; McPhillips, Timothy M.; Zinn, Daniel; Cohen, Aina E.; Feese, Michael D.; Bushnell, David; Tiefenbrunn, Theresa; Stout, C. David; Ludaescher, Bertram; Hedman, Britt; Hodgson, Keith O.; Soltis, S. Michael

    2013-01-01

    New software has been developed for automating the experimental and data-processing stages of fragment-based drug discovery at a macromolecular crystallography beamline. A new workflow-automation framework orchestrates beamline-control and data-analysis software while organizing results from multiple samples. AutoDrug is software based upon the scientific workflow paradigm that integrates the Stanford Synchrotron Radiation Lightsource macromolecular crystallography beamlines and third-party processing software to automate the crystallography steps of the fragment-based drug-discovery process. AutoDrug screens a cassette of fragment-soaked crystals, selects crystals for data collection based on screening results and user-specified criteria and determines optimal data-collection strategies. It then collects and processes diffraction data, performs molecular replacement using provided models and detects electron density that is likely to arise from bound fragments. All processes are fully automated, i.e. are performed without user interaction or supervision. Samples can be screened in groups corresponding to particular proteins, crystal forms and/or soaking conditions. A single AutoDrug run is only limited by the capacity of the sample-storage dewar at the beamline: currently 288 samples. AutoDrug was developed in conjunction with RestFlow, a new scientific workflow-automation framework. RestFlow simplifies the design of AutoDrug by managing the flow of data and the organization of results and by orchestrating the execution of computational pipeline steps. It also simplifies the execution and interaction of third-party programs and the beamline-control system. Modeling AutoDrug as a scientific workflow enables multiple variants that meet the requirements of different user groups to be developed and supported. A workflow tailored to mimic the crystallography stages comprising the drug-discovery pipeline of CoCrystal Discovery Inc. has been deployed and successfully

  2. Macromolecular composition of terrestrial and marine organic matter in sediments across the East Siberian Arctic Shelf

    Directory of Open Access Journals (Sweden)

    R. B. Sparkes

    2016-10-01

    Full Text Available Mobilisation of terrestrial organic carbon (terrOC from permafrost environments in eastern Siberia has the potential to deliver significant amounts of carbon to the Arctic Ocean, via both fluvial and coastal erosion. Eroded terrOC can be degraded during offshore transport or deposited across the wide East Siberian Arctic Shelf (ESAS. Most studies of terrOC on the ESAS have concentrated on solvent-extractable organic matter, but this represents only a small proportion of the total terrOC load. In this study we have used pyrolysis–gas chromatography–mass spectrometry (py-GCMS to study all major groups of macromolecular components of the terrOC; this is the first time that this technique has been applied to the ESAS. This has shown that there is a strong offshore trend from terrestrial phenols, aromatics and cyclopentenones to marine pyridines. There is good agreement between proportion phenols measured using py-GCMS and independent quantification of lignin phenol concentrations (r2 = 0.67, p < 0.01, n = 24. Furfurals, thought to represent carbohydrates, show no offshore trend and are likely found in both marine and terrestrial organic matter. We have also collected new radiocarbon data for bulk OC (14COC which, when coupled with previous measurements, allows us to produce the most comprehensive 14COC map of the ESAS to date. Combining the 14COC and py-GCMS data suggests that the aromatics group of compounds is likely sourced from old, aged terrOC, in contrast to the phenols group, which is likely sourced from modern woody material. We propose that an index of the relative proportions of phenols and pyridines can be used as a novel terrestrial vs. marine proxy measurement for macromolecular organic matter. Principal component analysis found that various terrestrial vs. marine proxies show different patterns across the ESAS, and it shows that multiple river–ocean transects of surface sediments transition from river-dominated to

  3. Tunable photonic multilayer sensors from photo-crosslinkable polymers

    Science.gov (United States)

    Chiappelli, Maria; Hayward, Ryan

    2014-03-01

    The fabrication of tunable photonic multilayer sensors from stimuli-responsive, photo-crosslinkable polymers will be described. Benzophenone is covalently incorporated as a pendent photo-crosslinker, allowing for facile preparation of multilayer films by sequential spin-coating and crosslinking processes. Copolymer chemistries and layer thicknesses are selected to provide robust multilayer sensors which can show color changes across nearly the full visible spectrum due to the specific stimulus-responsive nature of the hydrated film stack. We will describe how this approach is extended to alternative sensor designs by tailoring the thickness and chemistry of each layer independently, allowing for the preparation of sensors which depend not only on the shift in wavelength of a reflectance peak, but also on the transition between Bragg mirrors and filters. Device design is optimized by photo-patterning sensor arrays on a single substrate, providing more efficient fabrication time as well as multi-functional sensors. Finally, radiation-sensitive multilayers, designed by choosing polymers which will preferentially degrade or crosslink under ionizing radiation, will also be described.

  4. Porous Cross-Linked Polyimide-Urea Networks

    Science.gov (United States)

    Meador, Mary Ann B. (Inventor); Nguyen, Baochau N. (Inventor)

    2015-01-01

    Porous cross-linked polyimide-urea networks are provided. The networks comprise a subunit comprising two anhydride end-capped polyamic acid oligomers in direct connection via a urea linkage. The oligomers (a) each comprise a repeating unit of a dianhydride and a diamine and a terminal anhydride group and (b) are formulated with 2 to 15 of the repeating units. The subunit was formed by reaction of the diamine and a diisocyanate to form a diamine-urea linkage-diamine group, followed by reaction of the diamine-urea linkage-diamine group with the dianhydride and the diamine to form the subunit. The subunit has been cross-linked via a cross-linking agent, comprising three or more amine groups, at a balanced stoichiometry of the amine groups to the terminal anhydride groups. The subunit has been chemically imidized to yield the porous cross-linked polyimide-urea network. Also provided are wet gels, aerogels, and thin films comprising the networks, and methods of making the networks.

  5. Scleral lens tolerance after corneal cross-linking for keratoconus

    NARCIS (Netherlands)

    Visser, Esther Simone; Soeters, Nienke; Tahzib, Nayyirih G.

    2015-01-01

    Purpose. Subjective and objective evaluation of scleral lens tolerance and fitting before and after corneal cross-linking (CXL) for progressive keratoconus. Methods. In this prospective cohort, evaluations were made of 18 unilateral eyes in patients who underwent CXL and had been wearing scleral

  6. Effects of genipin corneal crosslinking in rabbit corneas.

    Science.gov (United States)

    Avila, Marcel Y; Narvaez, Mauricio; Castañeda, Juan P

    2016-07-01

    To evaluate the effect of genipin, a natural crosslinking agent, in rabbit eyes. Department of Ophthalmology, Universidad Nacional de Colombia Centro de Tecnologia Oftalmica, Bogotá, Colombia. Experimental study. Ex vivo rabbit eyes (16; 8 rabbits) were treated with genipin 1.00%, 0.50%, and 0.25% for 5 minutes with a vacuum device to increase corneal permeability. Penetration was evaluated using Scheimpflug pachymetry (Pentacam). In the in vivo model (20 rabbits; 1 eye treated, 1 eye with vehicle), corneas were crosslinked with genipin as described. Corneal curvature, corneal pachymetry, and intraocular pressure (IOP) assessments as well as slitlamp examinations were performed 0, 7, 30, and 60 days after treatment. In the ex vivo model, Scheimpflug pachymetry showed deep penetration in the rabbit corneas with an increase in corneal density and a dose-dependent relationship. Corneal flattening was observed in treated eyes (mean 4.4 diopters ± 0.5 [SD]) compared with the control eyes. Pachymetry and IOP were stable in all evaluations. No eye showed toxicity in the anterior chamber or in the lens. Corneal crosslinking induced by genipin produced significant flattening of the cornea with no toxicity in rabbit eyes. This crosslinking could be useful in the treatment of corneal ectasia and in the modification of corneal curvature. None of the authors has a financial or proprietary interest in any material or method mentioned. Copyright © 2016 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  7. Fabrication of chemically cross-linked porous gelatin matrices.

    Science.gov (United States)

    Bozzini, Sabrina; Petrini, Paola; Altomare, Lina; Tanzi, Maria Cristina

    2009-01-01

    The aim of this study was to chemically cross-link gelatin, by reacting its free amino groups with an aliphatic diisocyanate. To produce hydrogels with controllable properties, the number of reacting amino groups was carefully determined. Porosity was introduced into the gelatin-based hydrogels through the lyophilization process. Porous and non-porous matrices were characterized with respect to their chemical structure, morphology, water uptake and mechanical properties. The physical, chemical and mechanical properties of the porous matrices are related to the extent of their cross-linking, showing that they can be controlled by varying the reaction parameters. Water uptake values (24 hours) vary between 160% and 200% as the degree of cross-linking increases. The flexibility of the samples also decreases by changing the extent of cross-linking. Young's modulus shows values between 0.188 KPa, for the highest degree, and 0.142 KPa for the lowest degree. The matrices are potential candidates for use as tissue-engineering scaffolds by modulating their physical chemical properties according to the specific application.

  8. Chitosan Cross-linked Reconstituted Amniotic Collagen Membrane ...

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. Chitosan Cross-linked Reconstituted Amniotic Collagen Membrane – An Excellent Cell Substratum. The KERATINOCYTE proliferation and Differentiation into multiple layers is due to the presence of type - IV collagen in the amnion. Cultured FIBROBLASTS had good ...

  9. Epoxy-crosslinked sulfonated poly (phenylene) copolymer proton exchange membranes

    Science.gov (United States)

    Hibbs, Michael; Fujimoto, Cy H.; Norman, Kirsten; Hickner, Michael A.

    2010-10-19

    An epoxy-crosslinked sulfonated poly(phenylene) copolymer composition used as proton exchange membranes, methods of making the same, and their use as proton exchange membranes (PEM) in hydrogen fuel cells, direct methanol fuel cell, in electrode casting solutions and electrodes, and in sulfur dioxide electrolyzers. These improved membranes are tougher, have higher temperature capability, and lower SO.sub.2 crossover rates.

  10. Molecular Model for HNBR with Tunable Cross-Link Density.

    Science.gov (United States)

    Molinari, N; Khawaja, M; Sutton, A P; Mostofi, A A

    2016-12-15

    We introduce a chemically inspired, all-atom model of hydrogenated nitrile butadiene rubber (HNBR) and assess its performance by computing the mass density and glass-transition temperature as a function of cross-link density in the structure. Our HNBR structures are created by a procedure that mimics the real process used to produce HNBR, that is, saturation of the carbon-carbon double bonds in NBR, either by hydrogenation or by cross-linking. The atomic interactions are described by the all-atom "Optimized Potentials for Liquid Simulations" (OPLS-AA). In this paper, first, we assess the use of OPLS-AA in our models, especially using NBR bulk properties, and second, we evaluate the validity of the proposed model for HNBR by investigating mass density and glass transition as a function of the tunable cross-link density. Experimental densities are reproduced within 3% for both elastomers, and qualitatively correct trends in the glass-transition temperature as a function of monomer composition and cross-link density are obtained.

  11. Lactoferrin binding to transglutaminase cross-linked casein micelles

    NARCIS (Netherlands)

    Anema, S.G.; de Kruif, C.G.|info:eu-repo/dai/nl/073609609

    2012-01-01

    Casein micelles in skim milk were either untreated (untreated milk) or were cross-linked using transglutaminase (TGA-milk). Added lactoferrin (LF) bound to the casein micelles and followed Langmuir adsorption isotherms. The adsorption level was the same in both milks and decreased the micellar zeta

  12. Cholesterol Removal from Whole Egg by Crosslinked β-Cyclodextrin

    Directory of Open Access Journals (Sweden)

    H. J. Jeong

    2014-04-01

    Full Text Available This study was carried out to optimize cholesterol removal in whole egg using crosslinked β-cyclodextrin (β-CD and to recycle the β-CD. Various factors for optimizing conditions were concentration of the β-CD, mixing temperature, mixing time, mixing speed and centrifugal speed. In the result of this study, the optimum conditions of cholesterol removal were 25% crosslinked β-CD, 40°C mixing temperature, 30 min mixing time, 1,200 rpm mixing speed and 2,810×g centrifugal speed. The recycling was repeated five times. The cholesterol removal was 92.76% when treated with the optimum conditions. After determining the optimum conditions, the recyclable yields of the crosslinked β-CD ranged from 86.66% to 87.60% in the recycling and the percentage of cholesterol removal was over 80% until third recycling. However, the cholesterol removal efficiency was decreased when the number of repeated recycling was increased. Based on the result of this study, it was concluded that the crosslinked β-CD was efficient for cholesterol removal in whole egg, and recycling is possible for only limited repeating times due to the interaction of the β-CD and egg protein.

  13. Crosslink Radio Occultation for the Remote Sensing of Planetary Atmospheres

    Science.gov (United States)

    Mannucci, A. J.; Ao, C. O.; Asmar, S.; Edwards, C. D.; Kahan, D. S.; Paik, M.; Pi, X.; Williamson, W.

    2015-12-01

    Radio occultation utilizing deep space telecommunication signals has been used with great success in the profiling of planetary atmospheres and ionospheres since the 1960s. A shortcoming of this technique, however, is the limited temporal and spatial sampling that it provides. We consider a different approach where radio occultation measurements are taken between two spacecraft orbiting an extra-terrestrial body. Such "crosslink" radio occultations between the Global Positioning System satellites and low-earth orbiting spacecraft have been routinely acquired to provide global observations of the Earth's atmosphere and ionosphere that are used for weather forecast, climate analysis, and space weather applications. The feasibility of applying this concept to other planets has recently been demonstrated for the first time, where crosslink occultation measurements have been acquired between the Mars Odyssey and Mars Reconnaissance Orbiter spacecraft. These measurements leverage the proximity link telecommunication payloads on each orbiter, which are nominally used to provide relay communication and navigation services to Mars landers and rovers. In this presentation, we will describe the Mars crosslink experiments and the corresponding data analysis in detail. In addition, we will discuss how the crosslink occultation concepts can be effectively applied in future space exploration missions.

  14. In vitro evaluation of crosslinked electrospun fish gelatin scaffolds.

    Science.gov (United States)

    Gomes, S R; Rodrigues, G; Martins, G G; Henriques, C M R; Silva, J C

    2013-04-01

    Gelatin from cold water fish skin was electrospun, crosslinked and investigated as a substrate for the adhesion and proliferation of cells. Gelatin was first dissolved in either water or concentrated acetic acid and both solutions were successfully electrospun. Cross-linking was achieved via three different routes: glutaraldehyde vapor, genipin and dehydrothermal treatment. Solution's properties (surface tension, electrical conductivity and viscosity) and scaffold's properties (chemical bonds, weight loss and fiber diameters) were measured. Cellular viability was analyzed culturing 3T3 fibroblasts plated on the scaffolds and grown up to 7 days. The cells were fixed and observed with SEM or stained for DNA and F-actin and observed with confocal microscopy. In all scaffolds, the cells attached and spread with varying degrees. The evaluation of cell viability showed proliferation of cells until confluence in scaffolds crosslinked by glutaraldehyde and genipin; however the rate of growth in genipin crosslinked scaffolds was slow, recovering only by day five. The results using the dehydrothermal treatment were the less satisfactory. Our results show that glutaraldehyde treated fish gelatin is the most suitable substrate, of the three studied, for fibroblast adhesion and proliferation. Copyright © 2012 Elsevier B.V. All rights reserved.

  15. Jack of all trades: Versatile catechol crosslinking mechanisms

    NARCIS (Netherlands)

    Yang, J.; Cohen Stuart, M.A.; Kamperman, M.M.G.

    2014-01-01

    Catechols play an important role in many natural systems. They are known to readily interact with both organic (e.g., amino acids) and inorganic (e.g., metal ions, metal oxides) compounds, thereby providing a powerful system for protein curing. Catechol crosslinked protein networks, such as

  16. Mitosis, diffusible crosslinkers, and the ideal gas law.

    Science.gov (United States)

    Odde, David J

    2015-03-12

    During mitosis, molecular motors hydrolyze ATP to generate sliding forces between adjacent microtubules and form the bipolar mitotic spindle. Lansky et al. now show that the diffusible microtubule crosslinker Ase1p can generate sliding forces between adjacent microtubules, and it does so without ATP hydrolysis. Copyright © 2015 Elsevier Inc. All rights reserved.

  17. Mechanocatalytic polymerization and cross-linking in a polymeric matrix

    NARCIS (Netherlands)

    Jakobs, R.T.M.; Ma, Shuang; Sijbesma, R.P.

    2013-01-01

    A latent olefin metathesis catalyst, bearing two polymeric NHC ligands, was embedded in a semicrystalline polymer matrix containing cyclic olefins. The catalyst was activated by straining the solid material under compression, resulting in polymerization and cross-linking reactions of the monomers in

  18. The Effect of Polymer Molecular Weight on Citrate Crosslinked ...

    African Journals Online (AJOL)

    SEM), dissolution studies and differential scanning calorimetry (DSC) for surface ... Conclusion: The citrate-crosslinked chitosan films can be modulated to vary swelling and drug release at pH 3.5 and 6.2; this feature makes them useful tools for ...

  19. Practical application of thermoreversibly Cross-linked rubber products

    Science.gov (United States)

    Polgar, L. M.; Picchioni, F.; de Ruiter, E.; van Duin, M.

    2017-07-01

    Currently, rubber products cannot simply be reprocessed after their product life, due to the irreversible cross-linking methods traditionally applied. The purpose of this work is to investigate how thermoreversible cross-linking of rubbers via Diels Alder chemistry can be used for the development of recyclable rubber products. Unfortunately, the applicability of the thermoreversible EPM-g-furan/BM system appears to be limited to room temperature applications, because of the rapid deterioration of the compression set at elevated temperatures compared to irreversibly cross-linked EPM. However, the use of EPM rubber modified with thiophene or cyclopentadiene moieties may extend the temperature application range and results in rubber products with acceptable properties. Finally, rubber products generally comprise fillers such as silica, carbon black or fibers. In this context, the reinforcing effect of short cut aramid fibers on the material properties of the newly developed thermoreversibly cross-linked EPM rubbers was also studied. The material properties of the resulting products were found to be comparable to those of a fiber reinforced, peroxide cured reference sample.

  20. Radiation cross-linked PVC and its applications

    International Nuclear Information System (INIS)

    Lan Junming; Chen Ruyan; Jia Chaoxing; Li Min; Li Chengxin

    1990-04-01

    The radiation cross-linking technique is adopted for improving the polyvinyl chloride (PVC) heat-resistance and reducing its thermocontractibility. For examining its properties a small insulation sheath made from modified PVC material has been tested at 260 0 5 seconds. The results obtained were satisfactory

  1. Synthesis of crosslinked poly (styrene-co-divinylbenzene-co ...

    Indian Academy of Sciences (India)

    Synthesis of crosslinked poly(styrene--divinylbenzene--sulfopropyl methacrylate) nanoparticles by emulsion polymerization: Tuning the particle size and surface charge density. Dhamodaran Arunbabu Mousumi Hazarika Somsankar Naik Tushar Jana. Polymers Volume 32 Issue 6 December 2009 pp 633-641 ...

  2. Radiation crosslinked block copolymer blends with improved impact resistance

    International Nuclear Information System (INIS)

    Saunders, F.L.; Pelletier, R.R.

    1976-01-01

    Polymer blends having high impact resistance after mechanical working are produced by blending together a non-elastomeric monovinylidene aromatic polymer such as polystyrene with an elastomeric copolymer, such as a block copolymer of styrene and butadiene, in the form of crosslinked, colloidal size particles

  3. UV laser-induced cross-linking in peptides

    Science.gov (United States)

    Leo, Gabriella; Altucci, Carlo; Bourgoin-Voillard, Sandrine; Gravagnuolo, Alfredo M.; Esposito, Rosario; Marino, Gennaro; Costello, Catherine E.; Velotta, Raffaele; Birolo, Leila

    2013-01-01

    RATIONALE The aim of this study was to demonstrate, and to characterize by high resolution mass spectrometry, that it is possible to preferentially induce covalent cross-links in peptides by using high energy femtosecond UV laser pulses. The cross-link is readily formed only when aromatic amino acids are present in the peptide sequence. METHODS Three peptides, xenopsin, angiotensin I, interleukin, individually or in combination, were exposed to high energy femtosecond UV laser pulses, either alone or in the presence of spin trapping molecules, the reaction products being characterized by high resolution mass spectrometry. RESULTS High resolution mass spectrometry and spin trapping strategies showed that cross-linking occurs readily, proceeds via a radical mechanism, and is the highly dominant reaction, proceeding without causing significant photo-damage in the investigated range of experimental parameters. CONCLUSIONS High energy femtosecond UV laser pulses can be used to induce covalent cross-links between aromatic amino acids in peptides, overcoming photo-oxidation processes, that predominate as the mean laser pulse intensity approaches illumination conditions achievable with conventional UV light sources. PMID:23754800

  4. Functionalisation of cross-linked polyethylenimine for the removal of ...

    African Journals Online (AJOL)

    ... and describe the experimental data. The thermodynamic study of the adsorption process indicated high activation energies (55.91 kJ mol-1) which confirms chemisorption as a mechanism of interaction between As and PCPEI. Keywords: Adsorption; arsenic; phosphonated cross-linked polyethylenimine, functionalisation ...

  5. Vision Restoration with a Collagen Crosslinked Boston Keratoprosthesis Unit

    Science.gov (United States)

    2016-09-01

    ex vivo using vitamin B2 (riboflavin) and ultraviolet light. The overall objective of this study is to prevent sight-threatening keratoprosthesis...keratoprosthesis carrier cornea using tissue that has been cross-linked using vitamin B2 (riboflavin) and ultraviolet light prior to prosthesis

  6. Effects of the nature of the antioxidant on the radiation crosslinking of polyethylene

    Energy Technology Data Exchange (ETDEWEB)

    Gal, O S; Markovic, V M; Novakovic, L R; Stannett, V T

    1985-01-01

    The effects of three antioxidants, a hindered phenolic, a secondary amine and a thioester on the radiation crosslinking efficiency of low-density polyethylene were studied. Both gel content and thermomechanical analysis were used to follow the crosslinking. All three antioxidants decreased the amount of crosslinking at a given dose, the thioester being the most effective. The ratios of G (scission) to G (X linking) increased with all three antioxidants. This is attributed to the antioxidants only interfering with the crosslinking reaction. (author).

  7. The effects of the nature of the antioxidant on the radiation crosslinking of polyethylene

    International Nuclear Information System (INIS)

    Gal, O.S.; Markovic, V.M.; Novakovic, L.R.; Stannett, V.T.

    1985-01-01

    The effects of three antioxidants, a hindered phenolic, a secondary amine and a thioester on the radiation crosslinking efficiency of low-density polyethylene were studied. Both gel content and thermomechanical analysis were used to follow the crosslinking. All three antioxidants decreased the amount of crosslinking at a given dose, the thioester being the most effective. The ratios of G (scission) to G (X linking) increased with all three antioxidants. This is attributed to the antioxidants only interfering with the crosslinking reaction. (author)

  8. Nuclear magnetic relaxation induced by exchange-mediated orientational randomization: longitudinal relaxation dispersion for a dipole-coupled spin-1/2 pair.

    Science.gov (United States)

    Chang, Zhiwei; Halle, Bertil

    2013-10-14

    In complex biological or colloidal samples, magnetic relaxation dispersion (MRD) experiments using the field-cycling technique can characterize molecular motions on time scales ranging from nanoseconds to microseconds, provided that a rigorous theory of nuclear spin relaxation is available. In gels, cross-linked proteins, and biological tissues, where an immobilized macromolecular component coexists with a mobile solvent phase, nuclear spins residing in solvent (or cosolvent) species relax predominantly via exchange-mediated orientational randomization (EMOR) of anisotropic nuclear (electric quadrupole or magnetic dipole) couplings. The physical or chemical exchange processes that dominate the MRD typically occur on a time scale of microseconds or longer, where the conventional perturbation theory of spin relaxation breaks down. There is thus a need for a more general relaxation theory. Such a theory, based on the stochastic Liouville equation (SLE) for the EMOR mechanism, is available for a single quadrupolar spin I = 1. Here, we present the corresponding theory for a dipole-coupled spin-1/2 pair. To our knowledge, this is the first treatment of dipolar MRD outside the motional-narrowing regime. Based on an analytical solution of the spatial part of the SLE, we show how the integral longitudinal relaxation rate can be computed efficiently. Both like and unlike spins, with selective or non-selective excitation, are treated. For the experimentally important dilute regime, where only a small fraction of the spin pairs are immobilized, we obtain simple analytical expressions for the auto-relaxation and cross-relaxation rates which generalize the well-known Solomon equations. These generalized results will be useful in biophysical studies, e.g., of intermittent protein dynamics. In addition, they represent a first step towards a rigorous theory of water (1)H relaxation in biological tissues, which is a prerequisite for unravelling the molecular basis of soft

  9. Synthesis of branched polymers under continuous-flow microprocess: an improvement of the control of macromolecular architectures.

    Science.gov (United States)

    Bally, Florence; Serra, Christophe A; Brochon, Cyril; Hadziioannou, Georges

    2011-11-15

    Polymerization reactions can benefit from continuous-flow microprocess in terms of kinetics control, reactants mixing or simply efficiency when high-throughput screening experiments are carried out. In this work, we perform for the first time the synthesis of branched macromolecular architecture through a controlled/'living' polymerization technique, in tubular microreactor. Just by tuning process parameters, such as flow rates of the reactants, we manage to generate a library of polymers with various macromolecular characteristics. Compared to conventional batch process, polymerization kinetics shows a faster initiation step and more interestingly an improved branching efficiency. Due to reduced diffusion pathway, a characteristic of microsystems, it is thus possible to reach branched polymers exhibiting a denser architecture, and potentially a higher functionality for later applications. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Effects of far-ultraviolet radiation and oxygen on macromolecular synthesis and protein induction in Bacteroides fragilis BF-2

    International Nuclear Information System (INIS)

    Schumann, J.P.

    1983-11-01

    The study deals with the effects of far-UV radiation, oxygen and hydrogen peroxide on macromolecular synthesis and viability in the obligate anaerobe, Bacteroides fragilis, as well as the specific proteins induced in this organism by these different DNA damaging agents. Irradiation of Bacteroides fragilis cells with far-UV light (254 nm) under anaerobic conditions resulted in the immediate, rapid and extensive degradation of DNA which continued for 40 to 60 min after irradiation. DNA degradation after irradiation was inhibited by chloramphenicol and caffeine. RNA and protein synthesis were decreased by UV irradiation and the degree of inhibition was proportional to the UV dose. Colony formation was not affected immediately by UV irradiation and continued for a dose-dependent period prior to inhibition. The relationship between the DNA damage-induced proteins, macromolecular synthesis in damaged B. fragilis cells and the observed physiological responses and inducible repair phenomena after the different DNA damaging treatments in this anaerobe are discussed

  11. The 2D Structure of the T. brucei Preedited RPS12 mRNA Is Not Affected by Macromolecular Crowding

    Directory of Open Access Journals (Sweden)

    W.-Matthias Leeder

    2017-01-01

    Full Text Available Mitochondrial transcript maturation in African trypanosomes requires RNA editing to convert sequence-deficient pre-mRNAs into translatable mRNAs. The different pre-mRNAs have been shown to adopt highly stable 2D folds; however, it is not known whether these structures resemble the in vivo folds given the extreme “crowding” conditions within the mitochondrion. Here, we analyze the effects of macromolecular crowding on the structure of the mitochondrial RPS12 pre-mRNA. We use high molecular mass polyethylene glycol as a macromolecular cosolute and monitor the structure of the RNA globally and with nucleotide resolution. We demonstrate that crowding has no impact on the 2D fold and we conclude that the MFE structure in dilute solvent conditions represents a good proxy for the folding of the pre-mRNA in its mitochondrial solvent context.

  12. Distribution and enzymatic activity of heterotrophic bacteria decomposing selected macromolecular compounds in a Baltic Sea sandy beach

    Science.gov (United States)

    Podgórska, B.; Mudryk, Z. J.

    2003-03-01

    The potential capability to decompose macromolecular compounds, and the level of extracellular enzyme activities were determined in heterotrophic bacteria isolated from a sandy beach in Sopot on the Southern Baltic Sea coast. Individual isolates were capable of hydrolysing a wide spectrum of organic macromolecular compounds. Lipids, gelatine, and DNA were hydrolyzed most efficiently. Only a very small percentage of strains were able to decompose cellulose, and no pectinolytic bacteria were found. Except for starch-hydrolysis, no significant differences in the intensity of organic compound decomposition were recorded between horizontal and vertical profiles of the studied beach. Of all the studied extracellular enzymes, alkaline phosphatase, esterase lipase, and leucine acrylaminidase were most active; in contrast, the activity α-fucosidase, α-galactosidase and β-glucouronidase was the weakest. The level of extracellular enzyme activity was similar in both sand layers.

  13. Crosslinking of oriented polyethylene by electron beam radiation. Influence of morphology induced by drawing

    International Nuclear Information System (INIS)

    Aerle, N.A.J.M. van; Crevecoeur, G.; Lemstra, P.J.

    1988-01-01

    The influence of drawing on the crosslinking efficiency for electron beam radiation is reported for solution-crystallized ultra-high molecular weight polyethylene. A maximum in crosslinking efficiency is found at a draw ratio of approximately five, indicating an optimum morphology for inducing crosslinks during the hot-drawing process. (author)

  14. Cross-linking of dermal sheep collagen using a water-soluble carbodiimide

    NARCIS (Netherlands)

    Damink, LHHO; Dijkstra, PJ; vanLuyn, MJA; vanWachem, PB; Nieuwenhuis, P; Feijen, J

    A cross-linking method for collagen-based biomaterials was developed using the water-soluble carbodiimide 1-ethyl-3-(3-dimethyl aminopropyl)carbodiimide hydrochloride (EDC). Cross-linking using EDC involves the activation of carboxylic acid groups to give O-acylisourea groups, which form cross-links

  15. Cross-linking of dermal sheep collagen using a water-soluble carbodiimide

    NARCIS (Netherlands)

    Olde damink, L.H.H.; Olde Damink, L.H.H.; Dijkstra, Pieter J.; van Luyn, M.J.A.; van Wachem, P.B.; Nieuwenhuis, P.; Feijen, Jan

    1996-01-01

    A cross-linking method for collagen-based biomaterials was developed using the water-soluble carbodiimide 1-ethyl-3-(3-dimethyl aminopropyl)carbodiimide hydrochloride (EDC). Cross-linking using EDC involves the activation of carboxylic acid groups to give O-acylisourea groups, which form cross-links

  16. Permanent Set of Cross-Linking Networks: Comparison of Theory with Molecular Dynamics Simulations

    DEFF Research Database (Denmark)

    Rottach, Dana R.; Curro, John G.; Budzien, Joanne

    2006-01-01

    The permanent set of cross-linking networks is studied by molecular dynamics. The uniaxial stress for a bead-spring polymer network is investigated as a function of strain and cross-link density history, where cross-links are introduced in unstrained and strained networks. The permanent set...

  17. Small Strain Topological Effects of Biopolymer Networks with Rigid Cross-Links

    NARCIS (Netherlands)

    Zagar, G.; Onck, P. R.; Van der Giessen, E.; Garikipati, K; Arruda, EM

    2010-01-01

    Networks of cross-linked filamentous biopolymers form topological structures characterized by L, T and X cross-link types of connectivity 2, 3 and 4, respectively. The distribution of cross-links over these three types proofs to be very important for the initial elastic shear stiffness of isotropic

  18. Cross-linking of wheat gluten using a water-soluble carbodiimide

    NARCIS (Netherlands)

    Tropini, V.; Lens, J.P.; Mulder, W.J.; Silvestre, F.

    2000-01-01

    Wheat gluten was cross-linked using water-soluble 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide HCl (EDC). To enhance cross-linking, N-hydroxysuccinimide (NHS) was added to the reaction mixture. The cross-linking efficiency was evaluated by the decrease in the amount of amino groups, the solubility

  19. Thermoreversible cross-linking of maleated ethylene/propylene copolymers with diamines and amino-alcohols

    NARCIS (Netherlands)

    Mee, van der M.A.J.; Goossens, J.G.P.; Duin, van M.

    2008-01-01

    Maleated ethylene/propylene copolymers (MAn-g-EPM) were thermoreversibly cross-linked using diamines and amino-alcohols. Covalent cross-links are formed via the equilibrium reaction of the grafted anhydride groups with di-functional cross-linkers containing combinations of primary (1°) and secondary

  20. Newly identified interfibrillar collagen crosslinking suppresses cell proliferation and remodelling.

    Science.gov (United States)

    Marelli, Benedetto; Le Nihouannen, Damien; Hacking, S Adam; Tran, Simon; Li, Jingjing; Murshed, Monzur; Doillon, Charles J; Ghezzi, Chiara E; Zhang, Yu Ling; Nazhat, Showan N; Barralet, Jake E

    2015-06-01

    Copper is becoming recognised as a key cation in a variety of biological processes. Copper chelation has been studied as a potential anti-angiogenic strategy for arresting tumour growth. Conversely the delivery of copper ions and complexes in vivo can elicit a pro-angiogenic effect. Previously we unexpectedly found that copper-stimulated intraperitoneal angiogenesis was accompanied by collagen deposition. Here, in hard tissue, not only was healing accelerated by copper, but again enhanced deposition of collagen was detected at 2 weeks. Experiments with reconstituted collagen showed that addition of copper ions post-fibrillogenesis rendered plastically-compressed gels resistant to collagenases, enhanced their mechanical properties and increased the denaturation temperature of the protein. Unexpectedly, this apparently interfibrillar crosslinking was not affected by addition of glucose or ascorbic acid, which are required for crosslinking by advanced glycation end products (AGEs). Fibroblasts cultured on copper-crosslinked gels did not proliferate, whereas those cultured with an equivalent quantity of copper on either tissue culture plastic or collagen showed no effect compared with controls. Although non-proliferative, fibroblasts grown on copper-cross-linked collagen could migrate, remained metabolically active for at least 14 days and displayed a 6-fold increase in Mmps 1 and 3 mRNA expression compared with copper-free controls. The ability of copper ions to crosslink collagen fibrils during densification and independently of AGEs or Fenton type reactions is previously unreported. The effect on MMP susceptibility of collagen and the dramatic change in cell behaviour on this crosslinked ECM may contribute to shedding some light on unexplained phenomena as the apparent benefit of copper complexation in fibrotic disorders or the enhanced collagen deposition in response to localised copper delivery. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. Proton conducting sulphonated fluorinated poly(styrene) crosslinked electrolyte membranes

    Energy Technology Data Exchange (ETDEWEB)

    Soules, A.; Ameduri, B.; Boutevin, B.; David, G. [Institut Charles Gerhardt UMR CNRS 5253 Equipe, Ingenierie et Architectures Macromoleculaires,' ' Ecole Nationale Superieure de Chimie de Montpellier, 8 rue de l' Ecole Normale, 34296 Montpellier, Cedex 05 (France); Perrin, R. [CEA Le Ripault Departement des Materiaux, DMAT/SCMF/LSTP, BP16 - 37260 Monts (France); Gebel, G. [Structure et Proprietes des Architectures Moleculaires UMR 5819 (CEA-CNRS-UJF), INAC, SPrAM, CEA Grenoble, 17 Rue des Martyrs, 38054 Grenoble, Cedex 9 (France)

    2011-10-15

    Potential membranes for polymer electrolyte membrane fuel cell based on crosslinked sulphonated fluorinated polystyrenes (PS) were synthesised in two steps. First, azide-telechelic polystyrene was obtained by iodine transfer polymerisation of styrene in the presence of 1,6-diiodoperfluorohexane followed by azido chain-end functionalisation. Then azide-telechelic polystyrene was efficiently crosslinked with 1,10-diazido-1H,1H,2H,2H,9H,9H,10H,10H-perfluorodecane under UV irradiation. After 45 min only, almost completion of azide crosslinking could be achieved, resulting in crosslinked membranes with insoluble fractions higher than 95%. The sulphonation of the crosslinked membranes afforded ionic exchange capacities (IECs) ranging from 2.2 to 3.2 meq g{sup -1}. The hydration number was shown to be very high (from 30 to 75), depending on both the content of perfluorodecane and of sulphonic acid groups. The morphology of the membranes, assessed by small-angle X-ray scattering, was found to be a lamellar-type structure with two types of ionic domains. For the membrane that exhibited an IEC value of 2.2 meq.g{sup -1}, proton conductivity was in the same range as that of Nafion {sup registered} (120-135 mS.cm{sup -1}), whereas the membrane IEC value of 3.2 meq.g{sup -1} showed a proton conductivity higher than that of Nafion {sup registered} in liquid water from 25 to 80 C, though a high water uptake. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. DNA-to-protein crosslinks and backbone breaks caused by far- and near-ultraviolet, and visible light radiations in mammalian cells

    International Nuclear Information System (INIS)

    Peak, M.J.; Peak, J.G.

    1986-01-01

    Spectral responses for DNA damages caused by far-uv, near-uv, and visible light radiations have been studied. The near congruence of the spectra for far-uv damages and the spectrum of DNA is good evidence that the mechanism is the same for the induction of breaks, crosslinks, and pyrimidine dimers. For near-uv, the different spectra imply that at least several nonDNA sensitizer molecules act as primary chromophores, but that DNA damage eventually results. With the understanding that near-uv and visible radiations produce a variety of chemically potent reactive oxygen species within the cell, we recognize the possibility for many types of DNA damage. If we assume that SSBs and DNA-to-protein crosslinks are random single events along the genome, it is possible to compute the number of events per cell genome per lethal event caused by the different energies used. In the near-uv and visible region, many more breaks and crosslinks are formed per lethal event than by far-uv. About 20 times more SSBs per lethal event are caused by 365-nm radiation than by x-rays, strong evidence that these breaks are effectively repaired. It is therefore likely that SSBs are not a serious event with regard to cellular lethality. The role of crosslinks and their repair in lethal events is less clear. The lack of any correlation at all between the action spectra for SSBs, or crosslinks, and lethality and mutagenesis in the same cells is evidence that another lesion or lesions are involved in these events. The multitude of chemical events that can be caused in cellular metabolites by the reactive species generated by these long wavelengths of radiation means that death is attributable to the total spectrum of changed chemicals delivered by a lethal dose, only some of which are DNA changes leading to SSBs and crosslinks. 43 refs., 3 figs., 2 tabs

  3. A facile metal-free "grafting-from" route from acrylamide-based substrate toward complex macromolecular combs

    KAUST Repository

    Zhao, Junpeng

    2013-01-01

    High-molecular-weight poly(N,N-dimethylacrylamide-co-acrylamide) was used as a model functional substrate to investigate phosphazene base (t-BuP 4)-promoted metal-free anionic graft polymerization utilizing primary amide moieties as initiating sites. The (co)polymerization of epoxides was proven to be effective, leading to macromolecular combs with side chains being single- or double-graft homopolymer, block copolymer and statistical copolymer. © 2013 The Royal Society of Chemistry.

  4. Macromolecular pHPMA-based nanoparticles with cholesterol for solid tumor targeting: behavior in HSA protein environment

    Czech Academy of Sciences Publication Activity Database

    Zhang, X.; Niebuur, B.-J.; Chytil, Petr; Etrych, Tomáš; Filippov, Sergey K.; Kikhney, A.; Wieland, D. C. F.; Svergun, D. I.; Papadakis, C. M.

    2018-01-01

    Roč. 19, č. 2 (2018), s. 470-480 ISSN 1525-7797 R&D Projects: GA ČR(CZ) GC15-10527J; GA MZd(CZ) NV16-28594A; GA MŠk(CZ) LO1507 Institutional support: RVO:61389013 Keywords : polymer carriers * N-(2-hydroxypropyl)methacrylamide * tumor targeting Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 5.246, year: 2016

  5. C,N-2-[(Dimethylamino)methyl]phenylplatinum Complexes Functionalized with C60 as Macromolecular Building Blocks

    NARCIS (Netherlands)

    Koten, G. van; Meijer, M.D.; Wolf, E. de; Lutz, M.H.; Spek, A.L.; Klink, G.P.M. van

    2001-01-01

    The application of platinum(II) complexes based on the N,N-dimethylbenzylamine ligand (abbreviated as H-C,N) in macromolecular synthesis was demonstrated. Two cationic C,N-platinum moieties were linked with a 4,4'-bipyridine bridge, giving [{C6H4(CH2NMe2)-2-Pt(PPh3)}2(4,4'-bpy)](BF4)2 (2), the

  6. UQlust: combining profile hashing with linear-time ranking for efficient clustering and analysis of big macromolecular data.

    Science.gov (United States)

    Adamczak, Rafal; Meller, Jarek

    2016-12-28

    Advances in computing have enabled current protein and RNA structure prediction and molecular simulation methods to dramatically increase their sampling of conformational spaces. The quickly growing number of experimentally resolved structures, and databases such as the Protein Data Bank, also implies large scale structural similarity analyses to retrieve and classify macromolecular data. Consequently, the computational cost of structure comparison and clustering for large sets of macromolecular structures has become a bottleneck that necessitates further algorithmic improvements and development of efficient software solutions. uQlust is a versatile and easy-to-use tool for ultrafast ranking and clustering of macromolecular structures. uQlust makes use of structural profiles of proteins and nucleic acids, while combining a linear-time algorithm for implicit comparison of all pairs of models with profile hashing to enable efficient clustering of large data sets with a low memory footprint. In addition to ranking and clustering of large sets of models of the same protein or RNA molecule, uQlust can also be used in conjunction with fragment-based profiles in order to cluster structures of arbitrary length. For example, hierarchical clustering of the entire PDB using profile hashing can be performed on a typical laptop, thus opening an avenue for structural explorations previously limited to dedicated resources. The uQlust package is freely available under the GNU General Public License at https://github.com/uQlust . uQlust represents a drastic reduction in the computational complexity and memory requirements with respect to existing clustering and model quality assessment methods for macromolecular structure analysis, while yielding results on par with traditional approaches for both proteins and RNAs.

  7. Interrogating the architecture of protein assemblies and protein interaction networks by cross-linking mass spectrometry

    NARCIS (Netherlands)

    Liu, Fan; Heck, Albert J R

    2015-01-01

    Proteins are involved in almost all processes of the living cell. They are organized through extensive networks of interaction, by tightly bound macromolecular assemblies or more transiently via signaling nodes. Therefore, revealing the architecture of protein complexes and protein interaction

  8. Combination of supramolecular cross-linking with covalent cross-linking through epoxide ring-opening including gel studies

    NARCIS (Netherlands)

    Hofmeier, H.; El-Ghayoury, A.; Schubert, U.S.

    2003-01-01

    Terpolymers based on poly(methyl methacrylate), containing terpyridine-moieties as well as epoxide groups, were synthesized via free-radical polymeri-zation. The products were cross-linked non-covalently with iron(II) ions and cova-lently by treatment with AlCl3. Both steps could be combined in

  9. Combination of supramolecular cross-linking with covalent cross-linking through epoxide ring-opening including gel studies

    NARCIS (Netherlands)

    Hofmeier, H.; El-Ghayoury, A.; Schubert, U.S.

    2003-01-01

    Terpolymers based on poly(methyl methacrylate), containing terpyridinemoieties as well as epoxide groups, were synthesized via free-radical polymerization. The products were cross-linked non-covalently with iron(II) ions and covalently by treatment with AlCl3. Both steps could be combined in

  10. Macromolecular basis for homocystein-induced changes in proteoglycan structure in growth and arteriosclerosis.

    Science.gov (United States)

    McCully, K S

    1972-01-01

    Cell culture monolayers deficient in cystathionine synthetase bound more inorganic sulfate than normal cell monolayers during growth to confluence; this was correlated with the production of granular proteoglycan by the abnormal cells and fibrillar proteoglycan by normal cells. Homocysteine was demonstrated to be an active precursor of esterified sulfate, confirming our previous finding of this sulfation pathway in liver. The cell cultures deficient in cystathionine synthetase were found to assume an abnormal cellular distribution on the surface of the culture dish, resembling the distribution assumed by neoplastic cells with loss of contact inhibition; the degree of abnormality of the cellular distribution was correlated with the amount of granular proteoglycan produced by the cells and the amount of inorganic sulfate binding by the cell monolayers. Pyridoxine was found to increase the growth rate of cell cultures from a patient with pyridoxineresponsive homocystinuria and to increase the production of fibrillar proteoglycan by the cells; no effect of pyridoxine was observed in the cell cultures from a patient who failed to respond to pyridoxine therapy. The findings suggest that the change in macromolecular conformation of cellular proteoglycans from fibrillar to granular is due to increased sulfation of the carbohydrate envelope of the molecule. The significance of the findings is related to the pathogenesis of homocystinuria, the phenomenon of contact inhibition, the action of growth hormone and initiation of arteriosclerotic plaques.

  11. Lactoferricin B inhibits bacterial macromolecular synthesis in Escherichia coli and Bacillus subtilis.

    Science.gov (United States)

    Ulvatne, Hilde; Samuelsen, Ørjan; Haukland, Hanne H; Krämer, Manuela; Vorland, Lars H

    2004-08-15

    Most antimicrobial peptides have an amphipathic, cationic structure, and an effect on the cytoplasmic membrane of susceptible bacteria has been postulated as the main mode of action. Other mechanisms have been reported, including inhibition of cellular functions by binding to DNA, RNA and proteins, and the inhibition of DNA and/or protein synthesis. Lactoferricin B (Lfcin B), a cationic peptide derived from bovine lactoferrin, exerts slow inhibitory and bactericidal activity and does not lyse susceptible bacteria, indicating a possible intracellular target. In the present study incorporation of radioactive precursors into DNA, RNA and proteins was used to demonstrate effects of Lfcin B on macromolecular synthesis in bacteria. In Escherichia coli UC 6782, Lfcin B induces an initial increase in protein and RNA synthesis and a decrease in DNA synthesis. After 10 min, the DNA-synthesis increases while protein and RNA-synthesis decreases significantly. In Bacillus subtilis, however, all synthesis of macromolecules is inhibited for at least 20 min. After 20 min RNA-synthesis increases. The results presented here show that Lfcin B at concentrations not sufficient to kill bacterial cells inhibits incorporation of radioactive precursors into macromolecules in both Gram-positive and Gram-negative bacteria.

  12. About Small Streams and Shiny Rocks: Macromolecular Crystal Growth in Microfluidics

    Science.gov (United States)

    vanderWoerd, Mark; Ferree, Darren; Spearing, Scott; Monaco, Lisa; Molho, Josh; Spaid, Michael; Brasseur, Mike; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    We are developing a novel technique with which we have grown diffraction quality protein crystals in very small volumes, utilizing chip-based, microfluidic ("LabChip") technology. With this technology volumes smaller than achievable with any laboratory pipette can be dispensed with high accuracy. We have performed a feasibility study in which we crystallized several proteins with the aid of a LabChip device. The protein crystals are of excellent quality as shown by X-ray diffraction. The advantages of this new technology include improved accuracy of dispensing for small volumes, complete mixing of solution constituents without bubble formation, highly repeatable recipe and growth condition replication, and easy automation of the method. We have designed a first LabChip device specifically for protein crystallization in batch mode and can reliably dispense and mix from a range of solution constituents. We are currently testing this design. Upon completion additional crystallization techniques, such as vapor diffusion and liquid-liquid diffusion will be accommodated. Macromolecular crystallization using microfluidic technology is envisioned as a fully automated system, which will use the 'tele-science' concept of remote operation and will be developed into a research facility aboard the International Space Station.

  13. Improved reproducibility of unit-cell parameters in macromolecular cryocrystallography by limiting dehydration during crystal mounting.

    Science.gov (United States)

    Farley, Christopher; Burks, Geoffry; Siegert, Thomas; Juers, Douglas H

    2014-08-01

    In macromolecular cryocrystallography unit-cell parameters can have low reproducibility, limiting the effectiveness of combining data sets from multiple crystals and inhibiting the development of defined repeatable cooling protocols. Here, potential sources of unit-cell variation are investigated and crystal dehydration during loop-mounting is found to be an important factor. The amount of water lost by the unit cell depends on the crystal size, the loop size, the ambient relative humidity and the transfer distance to the cooling medium. To limit water loss during crystal mounting, a threefold strategy has been implemented. Firstly, crystal manipulations are performed in a humid environment similar to the humidity of the crystal-growth or soaking solution. Secondly, the looped crystal is transferred to a vial containing a small amount of the crystal soaking solution. Upon loop transfer, the vial is sealed, which allows transport of the crystal at its equilibrated humidity. Thirdly, the crystal loop is directly mounted from the vial into the cold gas stream. This strategy minimizes the exposure of the crystal to relatively low humidity ambient air, improves the reproducibility of low-temperature unit-cell parameters and offers some new approaches to crystal handling and cryoprotection.

  14. A vibrating membrane bioreactor (VMBR): Macromolecular transmission-influence of extracellular polymeric substances

    DEFF Research Database (Denmark)

    Beier, Søren; Jonsson, Gunnar Eigil

    2009-01-01

    The vibrating membrane bioreactor (VMBR) system facilitates the possibility of conducting a separation of macromolecules (BSA) from larger biological components (yeast cells) with a relatively high and stable macromolecular transmission at sub-critical flux. This is not possible to achieve...... for a static non-vibrating membrane module. A BSA transmission of 74% has been measured in the separation of 4g/L BSA from 8 g/L dry weight yeast cells in suspension at sub-critical flux (20L/(m(2) h)). However, this transmission is lower than the 85% BSA transmission measured for at pure 4g/L BSA solution....... This can be ascribed to the presence of extracellular polymeric substances (EPS) from the yeast cells. The initial fouling rate for constant sub-critical flux filtration of unwashed yeast cells is 3-4 times larger than for washed yeast cells (18(mbar/h)/5(mbar/h)). At sub-critical flux, an EPS transmission...

  15. Synthesis and Self-Assembly of Amphiphilic Triblock Terpolymers with Complex Macromolecular Architecture

    KAUST Repository

    Polymeropoulos, George; Zapsas, George; Hadjichristidis, Nikolaos; Avgeropoulos, Apostolos

    2015-01-01

    Two star triblock terpolymers (PS-b-P2VP-b-PEO)3 and one dendritic-like terpolymer [PS-b-P2VP-b-(PEO)2]3 of PS (polystyrene), P2VP (poly(2-vinylpyridine)), and PEO (poly(ethylene oxide)), never reported before, were synthesized by combining atom transfer radical and anionic polymerizations. The synthesis involves the transformation of the -Br groups of the previously reported Br-terminated 3-arm star diblock copolymers to one or two -OH groups, followed by anionic polymerization of ethylene oxide to afford the star or dendritic structure, respectively. The well-defined structure of the terpolymers was confirmed by static light scattering, size exclusion chromatography, and NMR spectroscopy. The self-assembly in solution and the morphology in bulk of the terpolymers, studied by dynamic light scattering and transmission electron microscopy, respectively, reveal new insights in the phase separation of these materials with complex macromolecular architecture. © 2015 American Chemical Society.

  16. Using support vector machines to improve elemental ion identification in macromolecular crystal structures

    Energy Technology Data Exchange (ETDEWEB)

    Morshed, Nader [University of California, Berkeley, CA 94720 (United States); Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Echols, Nathaniel, E-mail: nechols@lbl.gov [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Adams, Paul D., E-mail: nechols@lbl.gov [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); University of California, Berkeley, CA 94720 (United States)

    2015-05-01

    A method to automatically identify possible elemental ions in X-ray crystal structures has been extended to use support vector machine (SVM) classifiers trained on selected structures in the PDB, with significantly improved sensitivity over manually encoded heuristics. In the process of macromolecular model building, crystallographers must examine electron density for isolated atoms and differentiate sites containing structured solvent molecules from those containing elemental ions. This task requires specific knowledge of metal-binding chemistry and scattering properties and is prone to error. A method has previously been described to identify ions based on manually chosen criteria for a number of elements. Here, the use of support vector machines (SVMs) to automatically classify isolated atoms as either solvent or one of various ions is described. Two data sets of protein crystal structures, one containing manually curated structures deposited with anomalous diffraction data and another with automatically filtered, high-resolution structures, were constructed. On the manually curated data set, an SVM classifier was able to distinguish calcium from manganese, zinc, iron and nickel, as well as all five of these ions from water molecules, with a high degree of accuracy. Additionally, SVMs trained on the automatically curated set of high-resolution structures were able to successfully classify most common elemental ions in an independent validation test set. This method is readily extensible to other elemental ions and can also be used in conjunction with previous methods based on a priori expectations of the chemical environment and X-ray scattering.

  17. A technique for determining the deuterium/hydrogen contrast map in neutron macromolecular crystallography.

    Science.gov (United States)

    Chatake, Toshiyuki; Fujiwara, Satoru

    2016-01-01

    A difference in the neutron scattering length between hydrogen and deuterium leads to a high density contrast in neutron Fourier maps. In this study, a technique for determining the deuterium/hydrogen (D/H) contrast map in neutron macromolecular crystallography is developed and evaluated using ribonuclease A. The contrast map between the D2O-solvent and H2O-solvent crystals is calculated in real space, rather than in reciprocal space as performed in previous neutron D/H contrast crystallography. The present technique can thus utilize all of the amplitudes of the neutron structure factors for both D2O-solvent and H2O-solvent crystals. The neutron D/H contrast maps clearly demonstrate the powerful detectability of H/D exchange in proteins. In fact, alternative protonation states and alternative conformations of hydroxyl groups are observed at medium resolution (1.8 Å). Moreover, water molecules can be categorized into three types according to their tendency towards rotational disorder. These results directly indicate improvement in the neutron crystal structure analysis. This technique is suitable for incorporation into the standard structure-determination process used in neutron protein crystallography; consequently, more precise and efficient determination of the D-atom positions is possible using a combination of this D/H contrast technique and standard neutron structure-determination protocols.

  18. In Vitro and In Vivo Biocompatibility Evaluation of Polyallylamine and Macromolecular Heparin Conjugates Modified Alginate Microbeads.

    Science.gov (United States)

    Vaithilingam, Vijayaganapathy; Steinkjer, Bjørg; Ryan, Liv; Larsson, Rolf; Tuch, Bernard Edward; Oberholzer, Jose; Rokstad, Anne Mari

    2017-09-15

    Host reactivity to biocompatible immunoisolation devices is a major challenge for cellular therapies, and a human screening model would be of great value. We designed new types of surface modified barium alginate microspheres, and evaluated their inflammatory properties using human whole blood, and the intraperitoneal response after three weeks in Wistar rats. Microspheres were modified using proprietary polyallylamine (PAV) and coupled with macromolecular heparin conjugates (Corline Heparin Conjugate, CHC). The PAV-CHC strategy resulted in uniform and stable coatings with increased anti-clot activity and low cytotoxicity. In human whole blood, PAV coating at high dose (100 µg/ml) induced elevated complement, leukocyte CD11b and inflammatory mediators, and in Wistar rats increased fibrotic overgrowth. Coating of high dose PAV with CHC significantly reduced these responses. Low dose PAV (10 µg/ml) ± CHC and unmodified alginate microbeads showed low responses. That the human whole blood inflammatory reactions paralleled the host response shows a link between inflammatory potential and initial fibrotic response. CHC possessed anti-inflammatory activity, but failed to improve overall biocompatibility. We conclude that the human whole blood assay is an efficient first-phase screening model for inflammation, and a guiding tool in development of new generation microspheres for cell encapsulation therapy.

  19. Photochemical internalisation of a macromolecular protein toxin using a cell penetrating peptide-photosensitiser conjugate.

    Science.gov (United States)

    Wang, Julie T-W; Giuntini, Francesca; Eggleston, Ian M; Bown, Stephen G; MacRobert, Alexander J

    2012-01-30

    Photochemical internalisation (PCI) is a site-specific technique for improving cellular delivery of macromolecular drugs. In this study, a cell penetrating peptide, containing the core HIV-1 Tat 48-57 sequence, conjugated with a porphyrin photosensitiser has been shown to be effective for PCI. Herein we report an investigation of the photophysical and photobiological properties of a water soluble bioconjugate of the cationic Tat peptide with a hydrophobic tetraphenylporphyrin derivative. The cellular uptake and localisation of the amphiphilic bioconjugate was examined in the HN5 human head and neck squamous cell carcinoma cell line. Efficient cellular uptake and localisation in endo/lysosomal vesicles was found using fluorescence detection, and light-induced, rupture of the vesicles resulting in a more diffuse intracellular fluorescence distribution was observed. Conjugation of the Tat sequence with a hydrophobic porphyrin thus enables cellular delivery of an amphiphilic photosensitiser which can then localise in endo/lysosomal membranes, as required for effective PCI treatment. PCI efficacy was tested in combination with a protein toxin, saporin, and a significant reduction in cell viability was measured versus saporin or photosensitiser treatment alone. This study demonstrates that the cell penetrating peptide-photosensitiser bioconjugation strategy is a promising and versatile approach for enhancing the therapeutic potential of bioactive agents through photochemical internalisation. Copyright © 2011 Elsevier B.V. All rights reserved.

  20. The Effect of Attractive Interactions and Macromolecular Crowding on Crystallins Association.

    Directory of Open Access Journals (Sweden)

    Jiachen Wei

    Full Text Available In living systems proteins are typically found in crowded environments where their effective interactions strongly depend on the surrounding medium. Yet, their association and dissociation needs to be robustly controlled in order to enable biological function. Uncontrolled protein aggregation often causes disease. For instance, cataract is caused by the clustering of lens proteins, i.e., crystallins, resulting in enhanced light scattering and impaired vision or blindness. To investigate the molecular origins of cataract formation and to design efficient treatments, a better understanding of crystallin association in macromolecular crowded environment is needed. Here we present a theoretical study of simple coarse grained colloidal models to characterize the general features of how the association equilibrium of proteins depends on the magnitude of intermolecular attraction. By comparing the analytic results to the available experimental data on the osmotic pressure in crystallin solutions, we identify the effective parameters regimes applicable to crystallins. Moreover, the combination of two models allows us to predict that the number of binding sites on crystallin is small, i.e. one to three per protein, which is different from previous estimates. We further observe that the crowding factor is sensitive to the size asymmetry between the reactants and crowding agents, the shape of the protein clusters, and to small variations of intermolecular attraction. Our work may provide general guidelines on how to steer the protein interactions in order to control their association.

  1. Endocytic Uptake, Transport and Macromolecular Interactions of Anionic PAMAM Dendrimers within Lung Tissue.

    Science.gov (United States)

    Morris, Christopher J; Aljayyoussi, Ghaith; Mansour, Omar; Griffiths, Peter; Gumbleton, Mark

    2017-12-01

    Polyamidoamine (PAMAM) dendrimers are a promising class of nanocarrier with applications in both small and large molecule drug delivery. Here we report a comprehensive evaluation of the uptake and transport pathways that contribute to the lung disposition of dendrimers. Anionic PAMAM dendrimers and control dextran probes were applied to an isolated perfused rat lung (IPRL) model and lung epithelial monolayers. Endocytosis pathways were examined in primary alveolar epithelial cultures by confocal microscopy. Molecular interactions of dendrimers with protein and lipid lung fluid components were studied using small angle neutron scattering (SANS). Dendrimers were absorbed across the intact lung via a passive, size-dependent transport pathway at rates slower than dextrans of similar molecular sizes. SANS investigations of concentration-dependent PAMAM transport in the IPRL confirmed no aggregation of PAMAMs with either albumin or dipalmitoylphosphatidylcholine lung lining fluid components. Distinct endocytic compartments were identified within primary alveolar epithelial cells and their functionality in the rapid uptake of fluorescent dendrimers and model macromolecular probes was confirmed by co-localisation studies. PAMAM dendrimers display favourable lung biocompatibility but modest lung to blood absorption kinetics. These data support the investigation of dendrimer-based carriers for controlled-release drug delivery to the deep lung.

  2. FitEM2EM--tools for low resolution study of macromolecular assembly and dynamics.

    Directory of Open Access Journals (Sweden)

    Ziv Frankenstein

    Full Text Available Studies of the structure and dynamics of macromolecular assemblies often involve comparison of low resolution models obtained using different techniques such as electron microscopy or atomic force microscopy. We present new computational tools for comparing (matching and docking of low resolution structures, based on shape complementarity. The matched or docked objects are represented by three dimensional grids where the value of each grid point depends on its position with regard to the interior, surface or exterior of the object. The grids are correlated using fast Fourier transformations producing either matches of related objects or docking models depending on the details of the grid representations. The procedures incorporate thickening and smoothing of the surfaces of the objects which effectively compensates for differences in the resolution of the matched/docked objects, circumventing the need for resolution modification. The presented matching tool FitEM2EMin successfully fitted electron microscopy structures obtained at different resolutions, different conformers of the same structure and partial structures, ranking correct matches at the top in every case. The differences between the grid representations of the matched objects can be used to study conformation differences or to characterize the size and shape of substructures. The presented low-to-low docking tool FitEM2EMout ranked the expected models at the top.

  3. Olfactory nerve transport of macromolecular drugs to the brain. A problem in olfactory impaired patients

    International Nuclear Information System (INIS)

    Shiga, Hideaki; Yamamoto, Junpei; Miwa, Takaki

    2012-01-01

    Nasal administration of macromolecular drugs (including peptides and nanoparticles) has the potential to enable drug delivery system beyond the blood brain barrier (BBB) via olfactory nerve transport. Basic research on drug deliver systems to the brain via nasal administration has been well reported. Insulin-like growth factor-I (IGF-I) is associated with the development and growth of the central nervous system. Clinical application of IGF-I with nasal administration is intended to enable drug delivery to brain through the BBB. Uptake of IGF-I in the olfactory bulb and central nervous system increased according to the dosage of nasally administered IGF-I in normal ICR mice, however IGF-I uptake in the trigeminal nerve remained unchanged. Olfactory nerve transport is important for the delivery of nasally administered IGF-I to the brain in vivo. Because a safe olfactory nerve tracer has not been clinically available, olfactory nerve transport has not been well studied in humans. Nasal thallium-201 ( 201 Tl) administration has been safely used to assess the direct pathway to the brain via the nose in healthy volunteers with a normal olfactory threshold. 201 Tl olfactory nerve transport has recently been shown to decrease in patients with hyposmia. The olfactory nerve transport function in patients with olfactory disorders will be determined using 201 Tl olfacto-scintigraphy for the exclusion of candidates in a clinical trial to assess the usefulness of nasal administration of IGF-I. (author)

  4. Quickly Getting the Best Data from Your Macromolecular Crystals with a New Generation of Beamline Instruments

    International Nuclear Information System (INIS)

    Cipriani, Florent; Felisaz, Franck; Lavault, Bernard; Brockhauser, Sandor; Ravelli, Raimond; Launer, Ludovic; Leonard, Gordon; Renier, Michel

    2007-01-01

    While routine Macromolecular x-ray (MX) crystallography has relied on well established techniques for some years all the synchrotrons around the world are improving the throughput of their MX beamlines. Third generation synchrotrons provide small intense beams that make data collection of 5-10 microns sized crystals possible. The EMBL/ESRF MX Group in Grenoble has developed a new generation of instruments to easily collect data on 10 μm size crystals in an automated environment. This work is part of the Grenoble automation program that enables FedEx like crystallography using fully automated data collection and web monitored experiments. Seven ESRF beamlines and the MRC BM14 ESRF/CRG beamline are currently equipped with these latest instruments. We describe here the main features of the MD2x diffractometer family and the SC3 sample changer robot. Although the SC3 was primarily designed to increase the throughput of MX beamlines, it has also been shown to be efficient in improving the quality of the data collected. Strategies in screening a large number of crystals, selecting the best, and collecting a full data set from several re-oriented micro-crystals can now be run with minimum time and effort. The MD2x and SC3 instruments are now commercialised by the company ACCEL GmbH

  5. Macromolecular scaffolding: the relationship between nanoscale architecture and function in multichromophoric arrays for organic electronics.

    Science.gov (United States)

    Palermo, Vincenzo; Schwartz, Erik; Finlayson, Chris E; Liscio, Andrea; Otten, Matthijs B J; Trapani, Sara; Müllen, Klaus; Beljonne, David; Friend, Richard H; Nolte, Roeland J M; Rowan, Alan E; Samorì, Paolo

    2010-02-23

    The optimization of the electronic properties of molecular materials based on optically or electrically active organic building blocks requires a fine-tuning of their self-assembly properties at surfaces. Such a fine-tuning can be obtained on a scale up to 10 nm by mastering principles of supramolecular chemistry, i.e., by using suitably designed molecules interacting via pre-programmed noncovalent forces. The control and fine-tuning on a greater length scale is more difficult and challenging. This Research News highlights recent results we obtained on a new class of macromolecules that possess a very rigid backbone and side chains that point away from this backbone. Each side chain contains an organic semiconducting moiety, whose position and electronic interaction with neighboring moieties are dictated by the central macromolecular scaffold. A combined experimental and theoretical approach has made it possible to unravel the physical and chemical properties of this system across multiple length scales. The (opto)electronic properties of the new functional architectures have been explored by constructing prototypes of field-effect transistors and solar cells, thereby providing direct insight into the relationship between architecture and function.

  6. The structural biology center at the APS: an integrated user facility for macromolecular crystallography

    International Nuclear Information System (INIS)

    Rosenbaum, G.; Westbrook, E.M.

    1997-01-01

    The Structural Biology Center (SBC) has developed and operates a sector (undulator and bending magnet) of the APS as a user facility for macromolecular crystallography. Crystallographically determined structures of proteins, nucleic acids and their complexes with proteins, viruses, and complexes between macromolecules and small ligands have become of central importance in molecular and cellular biology. Major design goals were to make the extremely high brilliance of the APS available for brilliance limited studies, and to achieve a high throughput of less demanding studies, as well as optimization for MAS-phasing. Crystal samples will include extremely small crystals, crystals with large unit cells (viruses, ribosomes, etc.) and ensembles of closely similar crystal structures for drug design, protein engineering, etc. Data are recorded on a 3000x3000 pixel CCD-area detector (optionally on image plates). The x-ray optics of both beamlines has been designed to produce a highly demagnified image of the source in order to match the focal size with the sizes of the sample and the resolution element of the detector. Vertical focusing is achieved by a flat, cylindrically bent mirror. Horizontal focusing is achieved by sagitally bending the second crystal of the double crystal monochromator. Monochromatic fluxes of 1.3 * 10 13 ph/s into focal sizes of 0.08 mm (horizontal)x0.04 mm (vertical) FWHM (flux density 3.5 * 10 15 ph/s/mm 2 ) have been recorded.copyright 1997 American Institute of Physics

  7. Rapid automated superposition of shapes and macromolecular models using spherical harmonics.

    Science.gov (United States)

    Konarev, Petr V; Petoukhov, Maxim V; Svergun, Dmitri I

    2016-06-01

    A rapid algorithm to superimpose macromolecular models in Fourier space is proposed and implemented ( SUPALM ). The method uses a normalized integrated cross-term of the scattering amplitudes as a proximity measure between two three-dimensional objects. The reciprocal-space algorithm allows for direct matching of heterogeneous objects including high- and low-resolution models represented by atomic coordinates, beads or dummy residue chains as well as electron microscopy density maps and inhomogeneous multi-phase models ( e.g. of protein-nucleic acid complexes). Using spherical harmonics for the computation of the amplitudes, the method is up to an order of magnitude faster than the real-space algorithm implemented in SUPCOMB by Kozin & Svergun [ J. Appl. Cryst. (2001 ▸), 34 , 33-41]. The utility of the new method is demonstrated in a number of test cases and compared with the results of SUPCOMB . The spherical harmonics algorithm is best suited for low-resolution shape models, e.g . those provided by solution scattering experiments, but also facilitates a rapid cross-validation against structural models obtained by other methods.

  8. Synthesis and Self-Assembly of Amphiphilic Triblock Terpolymers with Complex Macromolecular Architecture

    KAUST Repository

    Polymeropoulos, George

    2015-11-25

    Two star triblock terpolymers (PS-b-P2VP-b-PEO)3 and one dendritic-like terpolymer [PS-b-P2VP-b-(PEO)2]3 of PS (polystyrene), P2VP (poly(2-vinylpyridine)), and PEO (poly(ethylene oxide)), never reported before, were synthesized by combining atom transfer radical and anionic polymerizations. The synthesis involves the transformation of the -Br groups of the previously reported Br-terminated 3-arm star diblock copolymers to one or two -OH groups, followed by anionic polymerization of ethylene oxide to afford the star or dendritic structure, respectively. The well-defined structure of the terpolymers was confirmed by static light scattering, size exclusion chromatography, and NMR spectroscopy. The self-assembly in solution and the morphology in bulk of the terpolymers, studied by dynamic light scattering and transmission electron microscopy, respectively, reveal new insights in the phase separation of these materials with complex macromolecular architecture. © 2015 American Chemical Society.

  9. A decade of user operation on the macromolecular crystallography MAD beamline ID14-4 at the ESRF

    International Nuclear Information System (INIS)

    McCarthy, Andrew A.; Brockhauser, Sandor; Nurizzo, Didier; Theveneau, Pascal; Mairs, Trevor; Spruce, Darren; Guijarro, Matias; Lesourd, Marc; Ravelli, Raimond B. G.; McSweeney, Sean

    2009-01-01

    The improvement of the X-ray beam quality achieved on ID14-4 by the installation of new X-ray optical elements is described. ID14-4 at the ESRF is the first tunable undulator-based macromolecular crystallography beamline that can celebrate a decade of user service. During this time ID14-4 has not only been instrumental in the determination of the structures of biologically important molecules but has also contributed significantly to the development of various instruments, novel data collection schemes and pioneering radiation damage studies on biological samples. Here, the evolution of ID14-4 over the last decade is presented, and some of the major improvements that were carried out in order to maintain its status as one of the most productive macromolecular crystallography beamlines are highlighted. The experimental hutch has been upgraded to accommodate a high-precision diffractometer, a sample changer and a large CCD detector. More recently, the optical hutch has been refurbished in order to improve the X-ray beam quality on ID14-4 and to incorporate the most modern and robust optical elements used at other ESRF beamlines. These new optical elements will be described and their effect on beam stability discussed. These studies may be useful in the design, construction and maintenance of future X-ray beamlines for macromolecular crystallography and indeed other applications, such as those planned for the ESRF upgrade

  10. Design, Synthesis and Characterization of Polyethylene-Based Macromolecular Architectures by Combining Polyhomologation with Powerful Linking Chemistry

    KAUST Repository

    Alkayal, Nazeeha

    2016-09-05

    Polyhomologation is a powerful method to prepare polyethylene-based materials with controlled molecular weight, topology and composition. This dissertation focuses on the discovery of new synthetic routes to prepare polyethylene-based macromolecular architectures by combining polyhomologation with highly orthogonal and efficient linking reactions such as Diels Alder, copper-catalyzed azide-alkyne cycloaddition (CuAAC), and Glaser. Taking advantage of functionalized polyhomologation initiators, as well as of the efficient coupling chemistry, we were able to synthesize various types of polymethylene (polyethylene)-based materials with complex architectures including linear co/terpolymers, graft terpolymers, and tadpole copolymers. In the first project, a facile synthetic route towards well-defined polymethylene-based co/terpolymers, by combining the anthracene/maleimide Diels–Alder reaction with polyhomologation, is presented. For the synthesis of diblock copolymers the following approach was applied: (a) synthesis of α-anthracene-ω-hydroxy-polymethylene by polyhomologation using tri (9 anthracene-methyl propyl ether) borane as the initiator, (b) synthesis of furan-protected-maleimide-terminated poly(ε-caprolactone) or polyethylene glycol and (c) Diels–Alder reaction between anthracene and maleimide-terminated polymers. In the case of triblock terpolymers, the α-anthracene-ω-hydroxy polymethylene was used as a macroinitiator for the ring-opening polymerization of D, L-lactide to afford an anthracene-terminated PM-b-PLA copolymer, followed by the Diels–Alder reaction with furan-protected maleimide-terminated poly (ε-caprolactone) or polyethylene glycol to give the triblock terpolymers. The synthetic methodology is general and potentially applicable to a range of polymers. The coupling reaction applied in the second project of this dissertation was copper-catalyzed “click” cycloaddition of azides and alkynes (CuAAC). Novel well-defined polyethylene

  11. Effect of Structure Change on Radiation Crosslinking of Unsaturated Polyesters

    International Nuclear Information System (INIS)

    Ranogajec, F.

    2006-01-01

    During the course of crosslinking of unsaturated polyesters reacting system, that was liquid prior to reaction, gels, and becomes solid. Crosslinking reaction begins to be controlled by the change of the physical state of the system at an early stage of reaction. The kinetics can not be studied by the usual kinetical methods. In-source 60 C o gamma rays induced crosslinking of unsaturated polyester with styrene was followed directly and continuously by measuring electrical conductivity change. The results of extraction analysis proved good correlation between the change of electrical conductivity and the extent of curing. The gel content was inversely proportional to conductivity and free styrene content directly proportional to conductivity. DC-electrical conductivity has shown high sensitivity toward structural changes and enabled us to detect liquid-liquid transitions in unsaturated polyester. The upper liquid-liquid transition (T l ρ) is less known transition caused by a stepwise decrease of intramolecular short-range local order that remains above the glass and lower liquid-liquid transitions. The local order is based on secondary valent interactions and is enhanced by hydrogen bonding. The linear temperature dependence of the viscosity and dc electrical conductivity of unsaturated polyesters showed a change of slope caused by the (T l ρ). Those changes were the result of the diminishing of the local order (which includes several bond lengths) caused by breaking of the intramolecular interactions. The intramolecular nature of the (T l ρ) in the polyesters under consideration was proved by its insensitivity to crosslinking and dilution with solvents. In the corresponding temperature range, DSC thermograms shoved expected endothermic changes. The structure changes related to the (T l ρ) in the investigated polyesters were determined by 1 H NMR and NIR spectroscopy. The proton NMR indicated that the stepwise change in hydrogen bonding occurred in the

  12. Link establishment criterion and topology optimization for hybrid GPS satellite communications with laser crosslinks

    Science.gov (United States)

    Li, Lun; Wei, Sixiao; Tian, Xin; Hsieh, Li-Tse; Chen, Zhijiang; Pham, Khanh; Lyke, James; Chen, Genshe

    2018-05-01

    In the current global positioning system (GPS), the reliability of information transmissions can be enhanced with the aid of inter-satellite links (ISLs) or crosslinks between satellites. Instead of only using conventional radio frequency (RF) crosslinks, the laser crosslinks provide an option to significantly increase the data throughput. The connectivity and robustness of ISL are needed for analysis, especially for GPS constellations with laser crosslinks. In this paper, we first propose a hybrid GPS communication architecture in which uplinks and downlinks are established via RF signals and crosslinks are established via laser links. Then, we design an optical crosslink assignment criteria considering the practical optical communication factors such as optical line- of-sight (LOS) range, link distance, and angular velocity, etc. After that, to further improve the rationality of establishing crosslinks, a topology control algorithm is formulated to optimize GPS crosslink networks at both physical and network layers. The RF transmission features for uplink and downlink and optical transmission features for crosslinks are taken into account as constraints for the optimization problem. Finally, the proposed link establishment criteria are implemented for GPS communication with optical crosslinks. The designs of this paper provide a potential crosslink establishment and topology control algorithm for the next generation GPS.

  13. Structure of E. coli 16S RNA elucidated by psoralen crosslinking

    International Nuclear Information System (INIS)

    Thompson, J.F.; Hearst, J.E.

    1983-01-01

    E. coli 16S RNA in solution was photoreacted with hydroxymethyltrimethylpsoralen and long wave ultraviolet light. Positions of crosslinks were determined to high resolution by partially digesting the RNA with T 1 RNase, separating the crosslinked fragments by two-dimensional gel electrophoresis, reversing the crosslink, and sequencing the separated fragments. This method yielded the locations of crosslinks to +/-15 nucleotides. Even finer placement has been made on the basis of our knowledge of psoralen reactivity. Thirteen unique crosslinks were mapped. Seven crosslinks confirmed regions of secondary structure which had been predicted in published phylogenetic models, three crosslinks discriminated between phylogenetic models, and three proved the existence of new structures. The new structures were all long-range interactions which appear to be in dynamic equilibrium with local secondary structure. Because this technique yields direct information about the secondary structure of large RNAs, it should prove invaluable in studying the structure of other RNAs of all sizes

  14. Yield and Failure Behavior Investigated for Cross-Linked Phenolic Resins Using Molecular Dynamics

    Science.gov (United States)

    Monk, Joshua D.; Lawson, John W.

    2016-01-01

    Molecular dynamics simulations were conducted to fundamentally evaluate the yield and failure behavior of cross-linked phenolic resins at temperatures below the glass transition. Yield stress was investigated at various temperatures, strain rates, and degrees of cross-linking. The onset of non-linear behavior in the cross-linked phenolic structures was caused by localized irreversible molecular rearrangements through the rotation of methylene linkers followed by the formation or annihilation of neighboring hydrogen bonds. The yield stress results, with respect to temperature and strain rate, could be fit by existing models used to describe yield behavior of amorphous glasses. The degree of cross-linking only indirectly influences the maximum yield stress through its influence on glass transition temperature (Tg), however there is a strong relationship between the degree of cross-linking and the failure mechanism. Low cross-linked samples were able to separate through void formation, whereas the highly cross-linked structures exhibited bond scission.

  15. Application of a fast sorting algorithm to the assignment of mass spectrometric cross-linking data.

    Science.gov (United States)

    Petrotchenko, Evgeniy V; Borchers, Christoph H

    2014-09-01

    Cross-linking combined with MS involves enzymatic digestion of cross-linked proteins and identifying cross-linked peptides. Assignment of cross-linked peptide masses requires a search of all possible binary combinations of peptides from the cross-linked proteins' sequences, which becomes impractical with increasing complexity of the protein system and/or if digestion enzyme specificity is relaxed. Here, we describe the application of a fast sorting algorithm to search large sequence databases for cross-linked peptide assignments based on mass. This same algorithm has been used previously for assigning disulfide-bridged peptides (Choi et al., ), but has not previously been applied to cross-linking studies. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Shape memory behaviour of radiation-crosslinked PCL/PMVS blends

    International Nuclear Information System (INIS)

    Zhu Guangming; Xu Shuogui; Wang Jinhua; Zhang Longbin

    2006-01-01

    The performance and radiation crosslinking of polycaprolactone (PCL) and polymethylvinylsiloxane (PMVS) blends has been investigated. Radiation crosslinking of PCL/PMVS blends followed the Charlesby-Pinner equation, and PMVS promoted the radiation crosslinking of the blends. As the concentration of PMVS increased, the gelation dose and the ratio of degradation to crosslinking (p 0 /q 0 ) decreased and the efficiency of radiation crosslinking increased. The elastic modulus below the melting point of PCL of radiation-crosslinked PCL/PMVS blends decreased with the increase of PMVS, and increased above the melting point. The crosslinked PCL/PMVS blends exhibited excellent shape memory effects, and the ratios of deformation to recovery were more than 95%

  17. Randomization tests

    CERN Document Server

    Edgington, Eugene

    2007-01-01

    Statistical Tests That Do Not Require Random Sampling Randomization Tests Numerical Examples Randomization Tests and Nonrandom Samples The Prevalence of Nonrandom Samples in Experiments The Irrelevance of Random Samples for the Typical Experiment Generalizing from Nonrandom Samples Intelligibility Respect for the Validity of Randomization Tests Versatility Practicality Precursors of Randomization Tests Other Applications of Permutation Tests Questions and Exercises Notes References Randomized Experiments Unique Benefits of Experiments Experimentation without Mani

  18. Crosslinking in the diglycidyl ether oligoepichlorhydrin-piperazine

    Directory of Open Access Journals (Sweden)

    Konstantyn E. Varlan

    2014-03-01

    Full Text Available The possibility of acquiring film material from a mixture of oligoepichlorhydrin diglycidylether and piperazyne discussed. The process involves elongation of the chain by means of reaction of the oligomer terminal oxyran cycles with piperazine aminogrups, and the subsequent formation of crosslinked by tertiary amine alongthe chainsalkylation whis chlorometyl dand groups of macromolecules. With this purpose, the model system investigated: epichlorohydrin−piperidine, epichlorohydrin−piperazine, oligoetylenglikol glicidyl ether−piperazine. The possibility of regulating the contributions of reactions of epoxy group and alkylation on crosslinking primary stage is disclosed, as well as material properties. Taking into account the found regularities receive elastic film structured materials with quaternary nitrogen atoms in the nodes. The ratio of tertiary and quaternary structure of nitrogen depends on the process conditions. Films swell in polar solvents and has ion-exchange properties.

  19. Natural polyphenols enhance stability of crosslinked UHMWPE for joint implants.

    Science.gov (United States)

    Shen, Jie; Gao, Guorong; Liu, Xincai; Fu, Jun

    2015-03-01

    Radiation-crosslinked UHMWPE has been used for joint implants since the 1990s. Postirradiation remelting enhances oxidative stability, but with some loss in strength and toughness. Vitamin E-stabilized crosslinked UHMWPE has shown improved strength and stability as compared with irradiated and remelted UHMWPE. With more active phenolic hydroxyl groups, natural polyphenols are widely used in the food and pharmaceutical industries as potent stabilizers and could be useful for oxidative stability in crosslinked UHMWPE. We asked whether UHMWPE blended with polyphenols would (1) show higher oxidation resistance after radiation crosslinking; (2) preserve the mechanical properties of UHMWPE after accelerated aging; and (3) alter the wear resistance of radiation-crosslinked UHMWPE. The polyphenols, gallic acid and dodecyl gallate, were blended with medical-grade UHMWPE followed by consolidation and electron beam irradiation at 100 kGy. Radiation-crosslinked virgin and vitamin E-blended UHMWPEs were used as reference materials. The UHMWPEs were aged at 120 °C in air with oxidation levels analyzed by infrared spectroscopy. Tensile (n = 5 per group) and impact (n = 3 per group) properties before and after aging as per ASTM F2003 were evaluated. The wear rates were examined by pin-on-disc testing (n = 3 per group). The data were reported as mean ± SDs. Statistical analysis was performed by using Student's t-test for a two-tailed distribution with unequal variance for tensile and impact data obtained with n ≥ 3. A significant difference is defined with p Accelerated aging of these polyphenol-blended UHMWPEs resulted in ultimate tensile strength of 50.4 ± 1.4 MPa and impact strength of 53 ± 5 kJ/m(2) for 100 kGy-irradiated UHMWPE with 0.05 wt% dodecyl gallate, for example, in comparison to 51.2 ± 0.7 MPa (p = 0.75) and 58 ± 5 kJ/m(2) (p = 0.29) before aging. The pin-on-disc wear rates of 100 kGy-irradiated UHMWPE with 0.05 wt% dodecyl gallate and 0.05 wt% gallic acid

  20. Preparation of micro-pored silicone elastomer through radiation crosslinking

    International Nuclear Information System (INIS)

    Gao Xiaoling; Gu Mei; Xie Xubing; Huang Wei

    2013-01-01

    The radiation crosslinking was adopted to prepare the micro-pored silicone elastomer, which was performed by vulcanization and foaming respectively. Radiation crosslinking is a new method to prepare micro-pored material with high performance by use of radiation technology. Silicon dioxide was used as filler, and silicone elastomer was vulcanized by electron beams, then the micro-pored material was made by heating method at a high temperature. The effects of absorbed dose and filler content on the performance and morphology were investigated. The structure and distribution of pores were observed by SEM. The results show that the micro-pored silicon elastomer can be prepared successfully by controlling the absorbed dose and filler content. It has a smooth surface similar to a rubber meanwhile the pores are round and unconnected to each other with the minimum size of 14 μm. And the good mechanical performance can be suitable for further uses. (authors)

  1. Absorbed energy for radiation crosslinking in stabilized PE systems

    International Nuclear Information System (INIS)

    Novakovic, Lj.; Gal, O.; Charlesby, A.

    1990-01-01

    A quantitative consideration on the absorbed energy consumption in various γ-irradiated polyethylene systems is given. On the base of the increased gel dose values for the PE systems containing antioxidant, relative to the gel doses for the pure polymers, the surplus of the absorbed energy due to the presence of the particular antioxidant is calculated. The increasing of the energy consumption in the stabilized systems depends on both the type and the content of the basic polymer. The surplus in the absorbed energy decreases with the radiation dose increasing, reflecting both the diminishing of the antioxidant concentration in the irradiating PE systems and the crosslinking level. The findings can be of interest in the estimation of the absorbed doses for the specific radiation crosslinking processes. (author)

  2. Absorbed energy for radiation crosslinking in stabilized PE systems

    Energy Technology Data Exchange (ETDEWEB)

    Novakovic, Lj; Gal, O [Institut za Nuklearne Nauke Boris Kidric, Belgrade (Yugoslavia); Charlesby, A

    1990-01-01

    A quantitative consideration on the absorbed energy consumption in various {gamma}-irradiated polyethylene systems is given. On the base of the increased gel dose values for the PE systems containing antioxidant, relative to the gel doses for the pure polymers, the surplus of the absorbed energy due to the presence of the particular antioxidant is calculated. The increasing of the energy consumption in the stabilized systems depends on both the type and the content of the basic polymer. The surplus in the absorbed energy decreases with the radiation dose increasing, reflecting both the diminishing of the antioxidant concentration in the irradiating PE systems and the crosslinking level. The findings can be of interest in the estimation of the absorbed doses for the specific radiation crosslinking processes. (author).

  3. Comparison of glutaraldehyde and carbodiimides to crosslink tissue engineering scaffolds fabricated by decellularized porcine menisci

    International Nuclear Information System (INIS)

    Gao, Shuang; Yuan, Zhiguo; Guo, Weimin; Chen, Mingxue; Liu, Shuyun; Xi, Tingfei; Guo, Quanyi

    2017-01-01

    The objectives of this study were to fabricate porous scaffolds using decellularized meniscus, and to explore a preferable crosslinking condition to enhance mechanical properties of scaffolds. Moreover, the microstructure, porosity, biodegradation and cytotoxicity were also evaluated. EDAC or GTA in different concentration was used to crosslink scaffolds. FTIR demonstrated functional groups change in crosslinking process. SEM photography showed that crosslinked scaffolds had blurry edges, which resulted scaffolds crosslinked by 1.2 mol/l EDAC had smaller porosity than other groups. The structure change enhanced antidegradation property. After immersing in enzyme solution for 96 h, scaffolds crosslinked by GTA and EDAC could maintain their mass > 70% and 80%. Most importantly, mechanical properties of crosslinked scaffolds were also improved. Uncrosslinked Scaffolds had only 0.49 kPa in compression modulus and 12.81 kPa in tensile modulus. The compression and tensile modulus of scaffolds crosslinked by 1.0% GTA were 1.42 and 567.44 kPa respectively. The same value of scaffolds crosslinked by 1.2 mol/l EDAC were 1.49 and 532.50 kPa. Scaffolds crosslinked by 1.0% and 2.5% GTA were toxic to cells, while EDAC groups showed no cytotoxicity. Chondrocytes could proliferate and infiltrate within scaffolds after seeding. Overall, 1.2 mol/l EDAC was a preferable crosslinking condition. - Highlights: • Porous meniscus scaffolds were fabricated using decellularized meniscus tissue. • Mechanical properties of meniscus scaffolds were enhanced by chemical crosslinking. • The crosslinked scaffold showed enhanced anti-degradation properties. • Chondrocytes could infiltrate and proliferate within crosslinked scaffolds.

  4. Comparison of glutaraldehyde and carbodiimides to crosslink tissue engineering scaffolds fabricated by decellularized porcine menisci

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Shuang [Center for Biomedical Material and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China); Yuan, Zhiguo; Guo, Weimin; Chen, Mingxue; Liu, Shuyun [Beijing Key Lab of Regenerative Medicine in Orthopaedics, Institute of Orthopaedics, Chinese PLA General Hospital, Beijing 100853 (China); Key Laboratory of Musculoskeletal Trauma & War Injuries, Institute of Orthopaedics, Chinese PLA General Hospital, Beijing 100853 (China); Xi, Tingfei, E-mail: tingfeixi@163.com [Center for Biomedical Material and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China); Shenzhen Institute, Peking University, Shenzhen 518057 (China); Guo, Quanyi, E-mail: doctorguo_301@163.com [Beijing Key Lab of Regenerative Medicine in Orthopaedics, Institute of Orthopaedics, Chinese PLA General Hospital, Beijing 100853 (China); Key Laboratory of Musculoskeletal Trauma & War Injuries, Institute of Orthopaedics, Chinese PLA General Hospital, Beijing 100853 (China)

    2017-02-01

    The objectives of this study were to fabricate porous scaffolds using decellularized meniscus, and to explore a preferable crosslinking condition to enhance mechanical properties of scaffolds. Moreover, the microstructure, porosity, biodegradation and cytotoxicity were also evaluated. EDAC or GTA in different concentration was used to crosslink scaffolds. FTIR demonstrated functional groups change in crosslinking process. SEM photography showed that crosslinked scaffolds had blurry edges, which resulted scaffolds crosslinked by 1.2 mol/l EDAC had smaller porosity than other groups. The structure change enhanced antidegradation property. After immersing in enzyme solution for 96 h, scaffolds crosslinked by GTA and EDAC could maintain their mass > 70% and 80%. Most importantly, mechanical properties of crosslinked scaffolds were also improved. Uncrosslinked Scaffolds had only 0.49 kPa in compression modulus and 12.81 kPa in tensile modulus. The compression and tensile modulus of scaffolds crosslinked by 1.0% GTA were 1.42 and 567.44 kPa respectively. The same value of scaffolds crosslinked by 1.2 mol/l EDAC were 1.49 and 532.50 kPa. Scaffolds crosslinked by 1.0% and 2.5% GTA were toxic to cells, while EDAC groups showed no cytotoxicity. Chondrocytes could proliferate and infiltrate within scaffolds after seeding. Overall, 1.2 mol/l EDAC was a preferable crosslinking condition. - Highlights: • Porous meniscus scaffolds were fabricated using decellularized meniscus tissue. • Mechanical properties of meniscus scaffolds were enhanced by chemical crosslinking. • The crosslinked scaffold showed enhanced anti-degradation properties. • Chondrocytes could infiltrate and proliferate within crosslinked scaffolds.

  5. Heterobifunctional crosslinkers for tethering single ligand molecules to scanning probes

    International Nuclear Information System (INIS)

    Riener, Christian K.; Kienberger, Ferry; Hahn, Christoph D.; Buchinger, Gerhard M.; Egwim, Innocent O.C.; Haselgruebler, Thomas; Ebner, Andreas; Romanin, Christoph; Klampfl, Christian; Lackner, Bernd; Prinz, Heino; Blaas, Dieter; Hinterdorfer, Peter; Gruber, Hermann J.

    2003-01-01

    Single molecule recognition force microscopy (SMRFM) is a versatile atomic force microscopy (AFM) method to probe specific interactions of cognitive molecules on the single molecule level. It allows insights to be gained into interaction potentials and kinetic barriers and is capable of mapping interaction sites with nm positional accuracy. These applications require a ligand to be attached to the AFM tip, preferably by a distensible poly(ethylene glycol) (PEG) chain between the measuring tip and the ligand molecule. The PEG chain greatly facilitates specific binding of the ligand to immobile receptor sites on the sample surface. The present study contributes to tip-PEG-ligand tethering in three ways: (i) a convenient synthetic route was found to prepare NH 2 -PEG-COOH which is the key intermediate for long heterobifunctional crosslinkers; (ii) a variety of heterobifunctional PEG derivatives for tip-PEG-ligand linking were prepared from NH 2 -PEG-COOH; (iii) in particular, a new PEG crosslinker with one thiol-reactive end and one terminal nitrilotriacetic acid (NTA) group was synthesized and successfully used to tether His 6 -tagged protein molecules to AFM tips via noncovalent NTA-Ni 2+ -His 6 bridges. The new crosslinker was applied to link a recombinant His 6 -tagged fragment of the very-low density lipoprotein receptor to the AFM tip whereupon specific docking to the capsid of human rhinovirus particles was observed by force microscopy. In a parallel study, the specific interaction of the small GTPase Ran with the nuclear import receptor importin β1 was studied in detail by SMRFM, using the new crosslinker to link His 6 -tagged Ran to the measuring tip [Nat. Struct. Biol. (2003), 10, 553-557

  6. Studies on flame retardancy of radiation crosslinked PE foam

    International Nuclear Information System (INIS)

    Yang Huili; Yao Zhanhai; Xu Jun

    1996-01-01

    CPE, DBDPO and Sb 2 O 3 were used as flame-retardant of PE foam. Effect of CPE on PE foam under radiation and it's flame-retardancy were studied. The result showed that CPE can enhance radiation cross-linking of PE, and trinary of addition being made of CPE, DBDPO and Sb 2 O 3 made oxygen index of PE foam achieve over 30, and self-extinguish, it did not influence manufacture and mechanical properties of PE foam

  7. The effects of trioctyl trimellitate concentration on crosslinking

    International Nuclear Information System (INIS)

    Jamaliah Sharif; Rozana Abu Bakar

    1997-01-01

    The effects of trimellitate type plasticizer concentration on PVC formulation were investigated. The results show that the degree of crosslinking is higher in the PVC compounds containing lower concentration of plasticizer compared to others. The tensile properties were decreased with the increase of plasticizer. However, the ageing properties of the lower concentration samples were very poor. The electrical properties of the compounds were acceptable with the volume resistivity value above 1014 . The heat deformation properties of the samples also improved after irradiation

  8. The Evaluation of Corneal Fragility After UVA/Riboflavin Crosslinking.

    Science.gov (United States)

    Li, Zhiwei; Wang, Yumeng; Xu, Yanyun; Jhanji, Vishal; Zhang, Chunxiao; Mu, Guoying

    2017-03-01

    To evaluate the fragility of cornea after UVA/riboflavin crosslinking (CXL). Sixty New Zealand rabbits received UVA/riboflavin crosslinking treatment (wavelength 365 nm, irradiance 3.0 mW/cm, and total dose 5.4 J/cm) on right eyes. Animals were sacrificed before and immediately after treatment (day 0), day 1, 3, 7, and 28 after treatment. A 4×10 mm corneal strip for biomechanical evaluation was harvested after sacrifice. The corneal fragility was evaluated by measurement of elongation rate, whereby the elongation rate equals elongation length/baseline length. The Youngs modulus and maximal stress were 1.41±0.51 MPa and 5.56±1.84 MPa before CXL, and increased to 2.31±0.68 MPa (P=0.008) and 9.25±2.74 MPa (P=0.04), respectively, on day 0, then maintained a stable level within a 28 days follow-up. The elongation rate was 62.04±9.34% before CXL and decreased to 48.95%±8.24% (P=0.02) on day 0, then maintained a stable level within a 28 days follow-up. This study showed an increase in the corneal fragility after UVA/riboflavin crosslinking along with an increase in the corneal stiffness. A long-term follow-up should be taken to evaluate the potential deleterious effect of the increasing corneal fragility after UVA/riboflavin crosslinking.

  9. Recycling tires? Reversible crosslinking of poly(butadiene).

    Science.gov (United States)

    Trovatti, Eliane; Lacerda, Talita M; Carvalho, Antonio J F; Gandini, Alessandro

    2015-04-01

    Furan-modified poly(butadiene) prepared by the thiol-ene click reaction is crosslinked with bismaleimides through the Diels-Alder reaction, giving rise to a novel recyclable elastomer. This is possible because of the thermal reversibility of the adducts responsible for the formation of the network. The use of this strategy provides the possibility to produce recyclable tires. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Macromolecular crystallographic results obtained using a 2048x2048 CCD detector at CHESS

    International Nuclear Information System (INIS)

    Thiel, D.J.; Ealick, S.E.; Tate, M.W.; Gruner, S.M.; Eikenberry, E.F.

    1996-01-01

    We present results of macromolecular crystallographic experiments performed at the Cornell High Energy Synchrotron Source (CHESS) with a new CCD-based detector. This detector, installed in January 1995, complements a 1024x1024 CCD detector that has been in continuous operation at CHESS since December 1993. The new detector is based on a 4-port, 2048x2048 pixel CCD that is directly coupled to a Gd 2 O 2 S:Tb phosphor by a 3:1 tapered fiber optic. The active area of the phosphor is a square 82 mm on an edge. The readout time is 7 seconds. In the standard mode of operation, the pixel size at the active area is 41 μm on the edge leading to the capability of resolving approximately 200 orders of diffraction across the detector face. The detector also operates in a 1024x1024 mode in which the pixel size is electronically increased by a factor of 4 in area resulting in smaller data files and faster detector readout but at the expense of spatial resolution. Most of the data that has been collected by this detector has been collected in this mode. Dozens of data sets have been collected by many experimenters using this detector at CHESS during the four month period from its installation until the start of the six-month down period of the storage ring. The capabilities of the detector will be illustrated with results from various crystallographic measurements including experiments in which the recorded diffraction patterns extend in resolution as far as 1 A. The results demonstrate that this detector is capable of collecting data of quality at least equal to that of imaging plates but, in many circumstances, with much greater beamline efficiency. copyright 1996 American Institute of Physics

  11. a Study of the Concentration Dependence of Macromolecular Diffusion Using Photon Correlation Spectroscopy.

    Science.gov (United States)

    Marlowe, Robert Lloyd

    The dynamic light scattering technique of photon correlation spectroscopy has been used to investigate the dependence of the mutual diffusion coefficient of a macromolecular system upon concentration. The first part of the research was devoted to the design and construction of a single-clipping autocorrelator based on newly-developed integrated circuits. The resulting 128 channel instrument can perform real time autocorrelation for sample time intervals >(, )10 (mu)s, and batch processed autocorrelation for intervals down to 3 (mu)s. An improved design for a newer, all-digital autocorrelator is given. Homodyne light scattering experiments were then undertaken on monodisperse solutions of polystyrene spheres. The single-mode TEM(,oo) beam of an argon-ion laser ((lamda) = 5145 (ANGSTROM)) was used as the light source; all solutions were studied at room temperature. The scattering angle was varied from 30(DEGREES) to 110(DEGREES). Excellent agreement with the manufacturer's specification for the particle size was obtained from the photon correlation studies. Finally, aqueous solutions of the globular protein ovalbumin, ranging in concentration from 18.9 to 244.3 mg/ml, were illuminated under the same conditions of temperature and wavelength as before; the homodyne scattered light was detected at a fixed scattering angle of 30(DEGREES). The single-clipped photocount autocorrelation function was analyzed using the homodyne exponential integral method of Meneely et al. The resulting diffusion coefficients showed a general linear dependence upon concentration, as predicted by the generalized Stokes-Einstein equation. However, a clear peak in the data was evident at c (TURNEQ) 100 mg/ml, which could not be explained on the basis of a non -interacting particle theory. A semi-quantitative approach based on the Debye-Huckel theory of electrostatic interactions is suggested as the probable cause for the peak's rise, and an excluded volume effect for its decline.

  12. Novel use for polyvinylpyrrolidone as a macromolecular crowder for enhanced extracellular matrix deposition and cell proliferation.

    Science.gov (United States)

    Rashid, Rafi; Lim, Natalie Sheng Jie; Chee, Stella Min Ling; Png, Si Ning; Wohland, Thorsten; Raghunath, Michael

    2014-12-01

    Macromolecular crowding (MMC) is a biophysical effect that governs biochemical processes inside and outside of cells. Since standard cell culture media lack this effect, the physiological performance of differentiated and progenitor cells, including extracellular matrix (ECM) deposition, is impaired in vitro. To bring back physiological crowdedness to in vitro systems, we have previously introduced carbohydrate-based macromolecules to culture media and have achieved marked improvements with mixed MMC in terms of ECM deposition and differentiation of mesenchymal stem cells (MSCs). We show here that although this system is successful, it is limited, due to viscosity, to only 33% of the fractional volume occupancy (FVO) of full serum, which we calculated to have an FVO of approximately 54% v/v. We show here that full-serum FVO can be achieved using polyvinylpyrrolidone (PVP) 360 kDa. Under these conditions, ECM deposition in human fibroblasts and MSCs is on par, if not stronger than, with original MMC protocols using carbohydrates, but with a viscosity that is not significantly changed. In addition, we have found that the proliferation rate for bone marrow-derived MSCs and fibroblasts increases slightly in the presence of PVP360, similar to that observed with carbohydrate-based crowders. A palette of MMC compounds is now emerging that enables us to tune the crowdedness of culture media seamlessly from interstitial fluid (9% FVO), in which the majority of tissue cells might be based, to serum environments mimicking intravascular conditions. Despite identical FVO's, individual crowder size effects play a role and different cell types appear to have preferences in terms of FVO and the crowder that this is achieved with. However, in the quest of crowders that we have predicted to have a smoother regulatory approval path, PVP is a highly interesting compound, as it has been widely used in the medical and food industries and shows a novel promising use in cell culture and

  13. Improving 2D and 3D Skin In Vitro Models Using Macromolecular Crowding.

    Science.gov (United States)

    Benny, Paula; Badowski, Cedric; Lane, E Birgitte; Raghunath, Michael

    2016-08-22

    The glycoprotein family of collagens represents the main structural proteins in the human body, and are key components of biomaterials used in modern tissue engineering. A technical bottleneck is the deposition of collagen in vitro, as it is notoriously slow, resulting in sub-optimal formation of connective tissue and subsequent tissue cohesion, particularly in skin models. Here, we describe a method which involves the addition of differentially-sized sucrose co-polymers to skin cultures to generate macromolecular crowding (MMC), which results in a dramatic enhancement of collagen deposition. Particularly, dermal fibroblasts deposited a significant amount of collagen I/IV/VII and fibronectin under MMC in comparison to controls. The protocol also describes a method to decellularize crowded cell layers, exposing significant amounts of extracellular matrix (ECM) which were retained on the culture surface as evidenced by immunocytochemistry. Total matrix mass and distribution pattern was studied using interference reflection microscopy. Interestingly, fibroblasts, keratinocytes and co-cultures produced cell-derived matrices (CDM) of varying composition and morphology. CDM could be used as "bio-scaffolds" for secondary cell seeding, where the current use of coatings or scaffolds, typically from xenogenic animal sources, can be avoided, thus moving towards more clinically relevant applications. In addition, this protocol describes the application of MMC during the submerged phase of a 3D-organotypic skin co-culture model which was sufficient to enhance ECM deposition in the dermo-epidermal junction (DEJ), in particular, collagen VII, the major component of anchoring fibrils. Electron microscopy confirmed the presence of anchoring fibrils in cultures developed with MMC, as compared to controls. This is significant as anchoring fibrils tether the dermis to the epidermis, hence, having a pre-formed mature DEJ may benefit skin graft recipients in terms of graft stability and

  14. Development of an online UV-visible microspectrophotometer for a macromolecular crystallography beamline.

    Science.gov (United States)

    Shimizu, Nobutaka; Shimizu, Tetsuya; Baba, Seiki; Hasegawa, Kazuya; Yamamoto, Masaki; Kumasaka, Takashi

    2013-11-01

    Measurement of the UV-visible absorption spectrum is a convenient technique for detecting chemical changes of proteins, and it is therefore useful to combine spectroscopy and diffraction studies. An online microspectrophotometer for the UV-visible region was developed and installed on the macromolecular crystallography beamline, BL38B1, at SPring-8. This spectrophotometer is equipped with a difference dispersive double monochromator, a mercury-xenon lamp as the light source, and a photomultiplier as the detector. The optical path is mostly constructed using mirrors, in order to obtain high brightness in the UV region, and the confocal optics are assembled using a cross-slit diaphragm like an iris to eliminate stray light. This system can measure optical densities up to a maximum of 4.0. To study the effect of radiation damage, preliminary measurements of glucose isomerase and thaumatin crystals were conducted in the UV region. Spectral changes dependent on X-ray dose were observed at around 280 nm, suggesting that structural changes involving Trp or Tyr residues occurred in the protein crystal. In the case of the thaumatin crystal, a broad peak around 400 nm was also generated after X-ray irradiation, suggesting the cleavage of a disulfide bond. Dose-dependent spectral changes were also observed in cryo-solutions alone, and these changes differed with the composition of the cryo-solution. These responses in the UV region are informative regarding the state of the sample; consequently, this device might be useful for X-ray crystallography.

  15. Phase behaviour of macromolecular liquid crystalline materials. Computational studies at the molecular level

    International Nuclear Information System (INIS)

    Stimson, Lorna M.

    2003-01-01

    Molecular simulations provide an increasingly useful insight into the static and dynamic characteristics of materials. In this thesis molecular simulations of macro-molecular liquid crystalline materials are reported. The first liquid crystalline material that has been investigated is a side chain liquid crystal polymer (SCLCP). In this study semi-atomistic molecular dynamics simulations have been conducted at a range of temperatures and an aligning potential has been applied to mimic the effect of a magnetic field. In cooling the SCLCP from an isotropic melt, microphase separation was observed yielding a domain structure. The application of a magnetic field to this structure aligns the domains producing a stable smectic mesophase. This is the first study in which mesophases have been observed using an off-lattice model of a SCLCP. The second material that has been investigated is a dendrimer with terminal mesogenic functionalization. Here, a multi-scale approach has been taken with Monte Carlo studies of a single dendrimer molecule in the gas phase at the atomistic level, semi-atomistic molecular dynamics of a single molecule in liquid crystalline solvents and a coarse-grained molecular dynamics study of the dendrimer in the bulk. The coarse-grained model has been developed and parameterized using the results of the atomistic and semi-atomistic work. The single molecule studies showed that the liquid crystalline dendrimer was able to change its structure by conformational changes in the flexible chains that link the mesogenic groups to the core. Structural change was seen under the application of a mean field ordering potential in the gas phase, and in the presence of liquid crystalline solvents. No liquid crystalline phases were observed for the bulk phase studies of the coarse-grained model. However, when the length of the mesogenic units was increased there was some evidence for microphase separation in these systems. (author)

  16. Assessing Exhaustiveness of Stochastic Sampling for Integrative Modeling of Macromolecular Structures.

    Science.gov (United States)

    Viswanath, Shruthi; Chemmama, Ilan E; Cimermancic, Peter; Sali, Andrej

    2017-12-05

    Modeling of macromolecular structures involves structural sampling guided by a scoring function, resulting in an ensemble of good-scoring models. By necessity, the sampling is often stochastic, and must be exhaustive at a precision sufficient for accurate modeling and assessment of model uncertainty. Therefore, the very first step in analyzing the ensemble is an estimation of the highest precision at which the sampling is exhaustive. Here, we present an objective and automated method for this task. As a proxy for sampling exhaustiveness, we evaluate whether two independently and stochastically generated sets of models are sufficiently similar. The protocol includes testing 1) convergence of the model score, 2) whether model scores for the two samples were drawn from the same parent distribution, 3) whether each structural cluster includes models from each sample proportionally to its size, and 4) whether there is sufficient structural similarity between the two model samples in each cluster. The evaluation also provides the sampling precision, defined as the smallest clustering threshold that satisfies the third, most stringent test. We validate the protocol with the aid of enumerated good-scoring models for five illustrative cases of binary protein complexes. Passing the proposed four tests is necessary, but not sufficient for thorough sampling. The protocol is general in nature and can be applied to the stochastic sampling of any set of models, not just structural models. In addition, the tests can be used to stop stochastic sampling as soon as exhaustiveness at desired precision is reached, thereby improving sampling efficiency; they may also help in selecting a model representation that is sufficiently detailed to be informative, yet also sufficiently coarse for sampling to be exhaustive. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  17. Methyl-β-cyclodextrin quaternary ammonium chitosan conjugate: nanoparticles vs macromolecular soluble complex

    Science.gov (United States)

    Piras, Anna Maria; Fabiano, Angela; Chiellini, Federica; Zambito, Ylenia

    2018-01-01

    Purpose The present study aimed to compare a novel cyclodextrin–polymer–drug complex in solution with a dispersed supramolecular nanosize system, made of the same complex, for ability to carry dexamethasone (DEX) across excised rat intestine. Results Methyl-β-cyclodextrin-quaternary ammonium chitosan conjugate (QA-Ch-MCD) was obtained by covalent grafting through a 10-atom spacer. The conjugate was characterized by 1H-NMR, resulting in 24.4% w/w of MCD content. Phase solubility profile analysis of the QA-Ch-MCD/DEX complex yielded an association constant of 14037 M−1, vs 4428 M−1 for the plain MCD/DEX complex. Nanoparticle (NP) dispersions resulted from ionotropic gelation of the QA-Ch-MCD/DEX complex by sodium tripolyphosphate, leading to 9.9%±1.4% drug loading efficiency. The mean diameter and zeta potential for NP were 299±32 nm (polydispersity index [PI] 0.049) and 11.5±1.1 mV, respectively. Those for QA-Ch-MCD/DEX were 2.7±0.4 nm (PI 0.048) and 6.7±0.6 mV. QA-Ch-MCD/DEX solutions and corresponding NP dispersions were compared in vitro for water-assisted transport through mucus, DEX permeation through excised rat intestine, and ex vivo mucoadhesivity. The complex showed higher mucoadhesion and lower transport rate through mucus; also, it provided faster drug permeation across excised rat intestine. Conclusion Carrier adhesion to mucus surface has played a most important role in favoring transepithelial permeation. Then, within the concerns of the present study, the use of NP seems not to provide any determinant advantage over using the simpler macromolecular complex. PMID:29731628

  18. The use of workflows in the design and implementation of complex experiments in macromolecular crystallography

    International Nuclear Information System (INIS)

    Brockhauser, Sandor; Svensson, Olof; Bowler, Matthew W.; Nanao, Max; Gordon, Elspeth; Leal, Ricardo M. F.; Popov, Alexander; Gerring, Matthew; McCarthy, Andrew A.; Gotz, Andy

    2012-01-01

    A powerful and easy-to-use workflow environment has been developed at the ESRF for combining experiment control with online data analysis on synchrotron beamlines. This tool provides the possibility of automating complex experiments without the need for expertise in instrumentation control and programming, but rather by accessing defined beamline services. The automation of beam delivery, sample handling and data analysis, together with increasing photon flux, diminishing focal spot size and the appearance of fast-readout detectors on synchrotron beamlines, have changed the way that many macromolecular crystallography experiments are planned and executed. Screening for the best diffracting crystal, or even the best diffracting part of a selected crystal, has been enabled by the development of microfocus beams, precise goniometers and fast-readout detectors that all require rapid feedback from the initial processing of images in order to be effective. All of these advances require the coupling of data feedback to the experimental control system and depend on immediate online data-analysis results during the experiment. To facilitate this, a Data Analysis WorkBench (DAWB) for the flexible creation of complex automated protocols has been developed. Here, example workflows designed and implemented using DAWB are presented for enhanced multi-step crystal characterizations, experiments involving crystal reorientation with kappa goniometers, crystal-burning experiments for empirically determining the radiation sensitivity of a crystal system and the application of mesh scans to find the best location of a crystal to obtain the highest diffraction quality. Beamline users interact with the prepared workflows through a specific brick within the beamline-control GUI MXCuBE

  19. MolProbity: all-atom structure validation for macromolecular crystallography

    International Nuclear Information System (INIS)

    Chen, Vincent B.; Arendall, W. Bryan III; Headd, Jeffrey J.; Keedy, Daniel A.; Immormino, Robert M.; Kapral, Gary J.; Murray, Laura W.; Richardson, Jane S.; Richardson, David C.

    2010-01-01

    MolProbity structure validation will diagnose most local errors in macromolecular crystal structures and help to guide their correction. MolProbity is a structure-validation web service that provides broad-spectrum solidly based evaluation of model quality at both the global and local levels for both proteins and nucleic acids. It relies heavily on the power and sensitivity provided by optimized hydrogen placement and all-atom contact analysis, complemented by updated versions of covalent-geometry and torsion-angle criteria. Some of the local corrections can be performed automatically in MolProbity and all of the diagnostics are presented in chart and graphical forms that help guide manual rebuilding. X-ray crystallography provides a wealth of biologically important molecular data in the form of atomic three-dimensional structures of proteins, nucleic acids and increasingly large complexes in multiple forms and states. Advances in automation, in everything from crystallization to data collection to phasing to model building to refinement, have made solving a structure using crystallography easier than ever. However, despite these improvements, local errors that can affect biological interpretation are widespread at low resolution and even high-resolution structures nearly all contain at least a few local errors such as Ramachandran outliers, flipped branched protein side chains and incorrect sugar puckers. It is critical both for the crystallographer and for the end user that there are easy and reliable methods to diagnose and correct these sorts of errors in structures. MolProbity is the authors’ contribution to helping solve this problem and this article reviews its general capabilities, reports on recent enhancements and usage, and presents evidence that the resulting improvements are now beneficially affecting the global database

  20. Prospects for simulating macromolecular surfactant chemistry at the ocean–atmosphere boundary

    International Nuclear Information System (INIS)

    Elliott, S; Burrows, S M; Liu, X; Deal, C; Long, M; Ogunro, O; Wingenter, O; Russell, L M

    2014-01-01

    Biogenic lipids and polymers are surveyed for their ability to adsorb at the water–air interfaces associated with bubbles, marine microlayers and particles in the overlying boundary layer. Representative ocean biogeochemical regimes are defined in order to estimate local concentrations for the major macromolecular classes. Surfactant equilibria and maximum excess are then derived based on a network of model compounds. Relative local coverage and upward mass transport follow directly, and specific chemical structures can be placed into regional rank order. Lipids and denatured protein-like polymers dominate at the selected locations. The assigned monolayer phase states are variable, whether assessed along bubbles or at the atmospheric spray droplet perimeter. Since oceanic film compositions prove to be irregular, effects on gas and organic transfer are expected to exhibit geographic dependence as well. Moreover, the core arguments extend across the sea–air interface into aerosol–cloud systems. Fundamental nascent chemical properties including mass to carbon ratio and density depend strongly on the geochemical state of source waters. High surface pressures may suppress the Kelvin effect, and marine organic hygroscopicities are almost entirely unconstrained. While bubble adsorption provides a well-known means for transporting lipidic or proteinaceous material into sea spray, the same cannot be said of polysaccharides. Carbohydrates tend to be strongly hydrophilic so that their excess carbon mass is low despite stacked polymeric geometries. Since sugars are abundant in the marine aerosol, gel-based mechanisms may be required to achieve uplift. Uncertainties distill to a global scale dearth of information regarding two dimensional kinetics and equilibria. Nonetheless simulations are recommended, to initiate the process of systems level quantification. (papers)

  1. Design of cellulose ether-based macromolecular prodrugs of ciprofloxacin for extended release and enhanced bioavailability.

    Science.gov (United States)

    Amin, Muhammad; Abbas, Nazia Shahana; Hussain, Muhammad Ajaz; Sher, Muhammad; Edgar, Kevin J

    2018-07-01

    The present study reveals the syntheses of hydroxypropylcellulose‑(HPC) and hydroxyethylcellulose‑(HEC) based macromolecular prodrugs (MPDs) of ciprofloxacin (CIP) using homogeneous reaction methodology. Covalently loaded drug content (DC) of each prodrug was quantified using UV-Vis spectrophotometry to determine degree of substitution (DS). HPC-ciprofloxacin (HPC-CIP) conjugates showed DS of CIP in the range 0.87-1.15 whereas HEC-ciprofloxacin (HEC-CIP) conjugates showed DS range 0.51-0.75. Transmission electron microscopy revealed that HPC-CIP conjugate 2 and HEC-CIP conjugate 6 self-assembled into nanoparticles of 150-300 and 180-250nm, respectively. Size exclusion chromatography revealed HPC-CIP conjugate 2 and HEC-CIP conjugate 6 as monodisperse systems. In vitro drug release studies indicated 15 and 43% CIP release from HPC-CIP conjugate 2 after 6h in simulated gastric and simulated intestinal fluids (SGF and SIF), respectively. HEC-CIP conjugate 6 showed 16% and 46% release after 6h in SGF and SIF, respectively. HPC-CIP conjugate 2 and HEC-CIP conjugate 6 exhibited half-lives of 10.87 and 11.71h, respectively with area under the curve values of 164 and 175hμgmL -1 , respectively, indicating enhanced bioavailability and improved pharmacokinetic profiles in animal model. Equal antibacterial activities to that of unmodified CIP confirmed their competitive efficacies. Cytotoxicity studies supported their non-toxic nature and biocompatibility. Copyright © 2018 Elsevier B.V. All rights reserved.

  2. Phase-Separated Liposomes Enhance the Efficiency of Macromolecular Delivery to the Cellular Cytoplasm.

    Science.gov (United States)

    Imam, Zachary I; Kenyon, Laura E; Ashby, Grant; Nagib, Fatema; Mendicino, Morgan; Zhao, Chi; Gadok, Avinash K; Stachowiak, Jeanne C

    2017-10-01

    From viruses to organelles, fusion of biological membranes is used by diverse biological systems to deliver macromolecules across membrane barriers. Membrane fusion is also a potentially efficient mechanism for the delivery of macromolecular therapeutics to the cellular cytoplasm. However, a key shortcoming of existing fusogenic liposomal systems is that they are inefficient, requiring a high concentration of fusion-promoting lipids in order to cross cellular membrane barriers. Toward addressing this limitation, our experiments explore the extent to which membrane fusion can be amplified by using the process of lipid membrane phase separation to concentrate fusion-promoting lipids within distinct regions of the membrane surface. We used confocal fluorescence microscopy to investigate the integration of fusion-promoting lipids into a ternary lipid membrane system that separated into liquid-ordered and liquid-disordered membrane phases. Additionally, we quantified the impact of membrane phase separation on the efficiency with which liposomes transferred lipids and encapsulated macromolecules to cells, using a combination of confocal fluorescence imaging and flow cytometry. Here we report that concentrating fusion-promoting lipids within phase-separated lipid domains on the surfaces of liposomes significantly increases the efficiency of liposome fusion with model membranes and cells. In particular, membrane phase separation enhanced the delivery of lipids and model macromolecules to the cytoplasm of tumor cells by at least 4-fold in comparison to homogenous liposomes. Our findings demonstrate that phase separation can enhance membrane fusion by locally concentrating fusion-promoting lipids on the surface of liposomes. This work represents the first application of lipid membrane phase separation in the design of biomaterials-based delivery systems. Additionally, these results lay the ground work for developing fusogenic liposomes that are triggered by physical and

  3. Enhanced conjugation stability and blood circulation time of macromolecular gadolinium-DTPA contrast agent.

    Science.gov (United States)

    Jenjob, Ratchapol; Kun, Na; Ghee, Jung Yeon; Shen, Zheyu; Wu, Xiaoxia; Cho, Steve K; Lee, Don Haeng; Yang, Su-Geun

    2016-04-01

    In this study, we prepared macromolecular MR T1 contrast agent: pullulan-conjugated Gd diethylene triamine pentaacetate (Gd-DTPA-Pullulan) and estimated residual free Gd(3+), chelation stability in competition with metal ions, plasma and tissue pharmacokinetics, and abdominal MR contrast on rats. Residual free Gd(3+) in Gd-DTPA-Pullulan was measured using colorimetric spectroscopy. The transmetalation of Gd(3+) incubated with Ca(2+) was performed by using a dialysis membrane (MWCO 100-500 Da) and investigated by ICP-OES. The plasma concentration profiles of Gd-DTPA-Pullulan were estimated after intravenous injection at a dose 0.1 mmol/kg of Gd. The coronal-plane abdominal images of normal rats were observed by MR imaging. The content of free Gd(3+), the toxic residual form, was less than 0.01%. Chelation stability of Gd-DTPA-Pullulan was estimated, and only 0.2% and 0.00045% of Gd(3+) were released from Gd-DTPA-Pullulan after 2h incubation with Ca(2+) and Fe(2+), respectively. Gd-DTPA-Pullulan displayed the extended plasma half-life (t1/2,α=0.43 h, t1/2,β=2.32 h), much longer than 0.11h and 0.79 h of Gd-EOB-DTPA. Abdominal MR imaging showed Gd-DTPA-Pullulan maintained initial MR contrast for 30 min. The extended plasma half-life of Gd-DTPA-Pullulan probably allows the prolonged MR acquisition time in clinic with enhanced MR contrast. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Optical and structural behaviors of crosslinked polyvinyl alcohol thin films

    Science.gov (United States)

    Pandit, Subhankar; Kundu, Sarathi

    2018-04-01

    Polyvinyl Alcohol (PVA) has excellent properties like uniaxial tensile stress, chemical resistance, biocompatibility, etc. The properties of PVA further can be tuned by crosslinking process. In this work, a simple heat treatment method is used to find out the optimum crosslinking of PVA and the corresponding structural and optical responses are explored. The PVA crosslinking is done by exposing the films at different temperatures and time intervals. The optical property of pure and heat treated PVA films are investigated by UV-Vis absorption and photoluminescence emission spectroscopy and structural modifications are studied by Fourier Transform Infrared Spectroscopy (FTIR). The absorption peaks of pure PVA are observed at ≈ 280 and 335 nm and the corresponding emission is observed at ≈ 424 nm. The pure PVA showed modified optical behaviors after the heat treatment. In addition, dipping the PVA films in hot water (85°C) for nearly 20 minutes also show impact on both structural and optical properties. From FTIR spectroscopy, the changes in vibrational band positions confirm the structural modifications of PVA films.

  5. Cross-linked polymeric membranes for carbon dioxide separation

    Science.gov (United States)

    Hong, Tao; Chatterjee, Sabornie; Mahurin, Shannon Mark; Long, Brian Keith; Jiang, De-en; Mays, Jimmy Wayne; Sokolov, Alexei P.; Saito, Tomonori

    2018-01-23

    A membrane useful in gas separation, the membrane comprising a cross-linked polysiloxane structure having a cross-link density of about 0.1.times.10.sup.-5 mol/cm.sup.3 to about 6.times.10.sup.-5 mol/cm.sup.3, where, in particular embodiments, the cross-linked polysiloxane structure has the following general structure: ##STR00001## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, and R.sup.6 are independently selected from hydrocarbon groups having at least 1 and up to 6 carbon atoms; A.sup.1 and A.sup.2 are independently selected from cyclic hydrocarbon groups; L.sup.1 and L.sup.2 are linking groups or covalent bonds; n is an integer of at least 1; r and s are independently selected from integers of at least 1; and p is an integer of at least 10. The invention also includes methods for making and using the above-described membranes for gas separation.

  6. Radiation crosslinking of methylcellulose and hydroxyethylcellulose in concentrated aqueous solutions

    International Nuclear Information System (INIS)

    Wach, Radoslaw A.; Mitomo, Hiroshi; Nagasawa, Naotsugu; Yoshii, Fumio

    2003-01-01

    The effects of ionizing radiation on aqueous solutions of cellulose ethers, methylcellulose (MC) and hydroxyethylcellulose (HEC) were investigated. The well-established knowledge states that cellulose and its derivatives belong to degrading type of polymers. However, in our study intermolecular crosslinking initiated by gamma rays or electron beam leaded to the formation of insoluble gel. This is an opposite effect of irradiation to the degradation. Paste-like form of the initial specimen, i.e. concentration 20-30%, when water plasticizes the bulk of polymer; and a high dose rate were favorable for hydrogel formation. Gel fraction up to 60% and 70% was obtained from solutions of HEC and MC, respectively. Produced hydrogels swell markedly in aqueous media by imbibing and holding the solvent. Radiation parameters of irradiation, such as yields of degradation and crosslinking and the gelation dose, were evaluated by sol-gel analysis on the basis of Charlesby-Rosiak equation. Despite of the crosslinked structure, obtained hydrogels can be included into the group of biodegradable materials. They undergo decomposition by the action of cellulase enzyme or microorganisms from compost

  7. Crosslinked ionic polysaccharides for stimuli-sensitive drug delivery.

    Science.gov (United States)

    Alvarez-Lorenzo, Carmen; Blanco-Fernandez, Barbara; Puga, Ana M; Concheiro, Angel

    2013-08-01

    Polysaccharides are gaining increasing attention as components of stimuli-responsive drug delivery systems, particularly since they can be obtained in a well characterized and reproducible way from the natural sources. Ionic polysaccharides can be readily crosslinked to render hydrogel networks sensitive to a variety of internal and external variables, and thus suitable for switching drug release on-off through diverse mechanisms. Hybrids, composites and grafted polymers can reinforce the responsiveness and widen the range of stimuli to which polysaccharide-based systems can respond. This review analyzes the state of the art of crosslinked ionic polysaccharides as components of delivery systems that can regulate drug release as a function of changes in pH, ion nature and concentration, electric and magnetic field intensity, light wavelength, temperature, redox potential, and certain molecules (enzymes, illness markers, and so on). Examples of specific applications are provided. The information compiled demonstrates that crosslinked networks of ionic polysaccharides are suitable building blocks for developing advanced externally activated and feed-back modulated drug delivery systems. Copyright © 2013 Elsevier B.V. All rights reserved.

  8. Structures of DNA containing psoralen crosslink and thymine dimer

    International Nuclear Information System (INIS)

    Kim, S.H.; Pearlman, D.A.; Holbrook, S.R.; Pirkle, D.

    1985-01-01

    UV irradiation by itself or in conjunction with other chemicals can cause covalent damages to DNA in living cells. To overcome the detrimental effect of DNA damage, cells developed a repair mechanism by which damaged DNA is repaired. In the absence of such repair, cell malfunction or cell death can occur. Two most studied radiation-induced DNA damage are thymine dimer formation by UV irradiation and psoralen crosslink by combination of psoralens and UV: In the former, two adjacent thymine bases on a strand of DNA are fused by forming cyclobutane ring, and in the latter, one pyrimidine on one DNA strand is crosslinked to another pyrimidine on the other strand via a psoralen. The authors' objective is to deduce the structure of DNA segment which contains a psoralen crosslink or a thymine dimer using the combination of results of X-ray crystallographic studies, molecular model building, and energy minimization. These structural features may be important for understanding the biological effects of such damages and for the recognition by the repair enzymes

  9. Crosslinking and corneal cryotherapy in acanthamoeba keratitis -- a histological study.

    Science.gov (United States)

    Hager, Tobias; Hasenfus, A; Stachon, T; Seitz, B; Szentmáry, N

    2016-01-01

    Acanthamoeba keratitis is rare, but difficult to treat. Penetrating keratoplasty is performed in therapy-resistant cases. Nevertheless, subsequent recurrences occur in 40 % of the cases. In addition to triple-topical therapy (polyhexamid, propamidinisoethionat, neomycin), treatment alternatives are corneal cryotherapy and/or crosslinking (CXL). The aim of our present histological study was to analyze the persistence of acanthamoebatrophozoites and cysts, the persistence of bacteria, and activation of keratocytes in corneas of acanthamoeba keratitis patients following corneal cryotherapy and/or CXL. We analyzed histologically corneal buttons (from penetrating keratoplasties) of nine patients with acanthamoeba keratitis, following corneal cryotherapy (two patients) or a combination of crosslinking and corneal cryotherapy (seven patients), using haematoxilin–eosin, periodic acid Schiff (PAS), Gram and alpha-smooth muscle actin (alpha-SMA) stainings. Acanthamoeba trophozoites persisted in three corneas after cryotherapy and CXL. Cysts persisted in one of two corneas following corneal cryotherapy and in six of seven corneas after a combination of CXL and cryotherapy. One cornea showed positive Gram staining, but there were no alpha-SMA positive keratocytes in any of the corneas. Crosslinking and corneal cryotherapy have only limited impact on killing of acanthamoeba trophozoites, cysts, or bacteria. Corneal cryotherapy and CXL did not stimulate myofibroblastic transformation of keratocytes.

  10. Radiation-induced crosslinking of syndiotactic 1,2-polybutadiene

    International Nuclear Information System (INIS)

    Iwai, Tadashi; Hoshino, Sadao; Yamamoto, Rokuro; Okamoto, Hidemasa; Obana, Kazuyoshi.

    1978-01-01

    Crystalline syndiotactic 1, 2-polybutadiene (hereafter abbreviated as 1, 2-PB) developed in Ube Industries, Ltd. by its own technology is a new thermoplastic resin belonging to the intermediate region between rubber and plastics in its flexibility. By selecting appropriate catalyst composition, 1, 2-PB having the melting point of 90 to 200 deg. C and crystallization of 10 to 65% can be obtained. These 1, 2-PBs can be worked to formed products by general thermoplastic forming methods such as injection molding, extrusion forming and blow forming. Radiation-crosslinked 1, 2-PB changed to very hard polymers through heat treatment. This change has been found to be radical chain reaction of cyclic polymerization. The relation of radiation-induced crosslinking and thermal expansion behavior, and the changes of appearance and structural and physical properties with heat treatment of these polymers are described. That is, specific gravity has increased, tensile strength has been enhanced, and elongation has decreased. While dielectric strength and arc resistivity have been upgraded. Therefore, these polymers can be used for the following applications: food wrapping film, molded notions, molded low foaming material for the soles of footwears, highly foaming moldings such as sponges, electric insulation material such as cable coating and adhesives for many materials. It is considered that crosslinking contributes to the application to electric insulation materials and heat curing to heat-resistant materials and parts. (Wakatsuki, Y.)

  11. Superficial corneal crosslinking during laser in situ keratomileusis.

    Science.gov (United States)

    Seiler, Theo G; Fischinger, Isaak; Koller, Tobias; Derhartunian, Viktor; Seiler, Theo

    2015-10-01

    To determine the safety of superficial corneal crosslinking after laser in situ keratomileusis (LASIK). Institut für Refraktive und Ophthalmo-Chirurgie, Zurich, Switzerland. Prospective study. Eyes with an ectasia risk score of 2 or higher were treated with standard LASIK (90 μm flap) for myopia correction, after which a rapid corneal crosslinking was performed in the interface (riboflavin 0.5% for 2 minutes, 9 mW/cm(2) for 5 minutes) (Group 1). The follow-up was up to 1 year. The prevalence of complications was statistically compared with that in a group of eyes matched regarding age, sex, and attempted refractive correction that were treated with standard LASIK only (Group 2). One month postoperatively, 5 eyes in Group 1 lost 1 line of corrected distance visual acuity (CDVA) compared with 1 eye in Group 2 (P rate of less than 5%. The refractive success was identical in both groups. Early postoperative complications such as erosions (16%), diffuse lamellar keratitis (DLK) stage 1 (38%), and DLK stage 2 (5%) were statistically significantly more frequent after superficial corneal crosslinking, leading to a statistically significantly reduced uncorrected distance visual acuity at 1 month (P interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  12. Lithium polymer cell assembled by in situ chemical cross-linking of ionic liquid electrolyte with phosphazene-based cross-linking agent

    International Nuclear Information System (INIS)

    Choi, Ji-Ae; Kang, Yongku; Kim, Dong-Won

    2013-01-01

    Highlights: ► Ionic liquid-based cross-linked gel polymer electrolytes were synthesized and their electrochemical properties were investigated. ► Lithium polymer cells with in situ cross-linked gel polymer electrolytes exhibited reversible cycling behavior with good capacity retention. ► The use of ionic liquid-based cross-linked gel polymer electrolytes significantly improved the thermal stability of the cells. -- Abstract: Ionic liquid-based cross-linked gel polymer electrolytes were prepared with a phosphazene-based cross-linking agent, and their electrochemical properties were investigated. Lithium polymer cells composed of lithium anode and LiCoO 2 cathode were assembled with ionic liquid-based cross-linked gel polymer electrolyte and their cycling performance was evaluated. The interfacial adhesion between the electrodes and the electrolyte by in situ chemical cross-linking resulted in stable capacity retention of the cell. A reduction in the ionic mobility in both the electrolyte and the electrode adversely affected discharge capacity and high rate performance of the cell. DSC studies demonstrated that the use of ionic liquid-based cross-linked gel polymer electrolytes provided a significant improvement in the thermal stability of the cell

  13. Oxidation resistant peroxide cross-linked UHMWPE produced by blending and surface diffusion

    International Nuclear Information System (INIS)

    Gul, Rizwan M; Oral, Ebru; Muratoglu, Orhun K

    2014-01-01

    Ultra-high molecular weight polyethylene (UHMWPE) has been widely used as acetabular cup in total hip replacement (THR) and tibial component in total knee replacement (TKR). Crosslinking of UHMWPE has been successful used to improve its wear performance leading to longer life of orthopedic implants. Crosslinking can be performed by radiation or organic peroxides. Peroxide crosslinking is a convenient process as it does not require specialized equipment and the level of crosslinking can be manipulated by changing the amount of peroxide added. However, there is concern about the long-term stability of these materials due to possible presence of by-products. Vitamin E has been successfully used to promote long-term oxidative stability of UHMWPE. In this study, UHMWPE has been crosslinked using organic peroxide in the presence of Vitamin E to produce an oxidation resistant peroxide crosslinked material. Crosslinking was performed both in bulk by mixing peroxide and resin, and only on the surface using diffusion of peroxides.The results show that UHMWPE can be crosslinked using organic peroxides in the presence of vitamin E by both methods. However, the level of crosslinking decreases with the increase in vitamin E content. The wear resistance increases with the increase in crosslink density, and oxidation resistance significantly increases due to the presence of vitamin E

  14. Oxidation resistant peroxide cross-linked UHMWPE produced by blending and surface diffusion

    International Nuclear Information System (INIS)

    Gul, R. M.; Oral, E.; Muratoglu, O. K.

    2013-01-01

    Ultra-high molecular weight polyethylene (UHMWPE) has been widely used as acetabular cup in total hip replacement (THR) and tibial component in total knee replacement (TKR). Crosslinking of UHMWPE has been successful used to improve its wear performance leading to longer life of orthopedic implants. Crosslinking can be performed by radiation or organic peroxides. Peroxide crosslinking is a convenient process as it does not require specialized equipment and the level of crosslinking can be manipulated by changing the amount of peroxide added. However, there is concern about the long-term stability of these materials due to possible presence of by-products. Vitamin E has been successfully used to promote long-term oxidative stability of UHMWPE. In this study, UHMWPE has been crosslinked using organic peroxide in the presence of Vitamin E to produce an oxidation resistant peroxide crosslinked material. Crosslinking was performed both in bulk by mixing peroxide and resin, and only on the surface using diffusion of peroxides.The results show that UHMWPE can be crosslinked using organic peroxides in the presence of vitamin E by both methods. However, the level of crosslinking decreases with the increase in vitamin E content. The wear resistance increases with the increase in crosslink density, and oxidation resistance significantly increases due to the presence of vitamin E. (author)

  15. Reactive electrospinning and biodegradation of cross-linked methacrylated polycarbonate nanofibers

    Energy Technology Data Exchange (ETDEWEB)

    Wu Ruizhi; Zhang Jianfeng; Fan Yuwei; Xu Xiaoming [Department of Comprehensive Dentistry and Biomaterials, Louisiana State University Health Sciences Center, 1100 Florida Avenue, Box 137, New Orleans, LA 70119 (United States); Stoute, Diana; Lallier, Thomas, E-mail: xxu@lsuhsc.edu [Department of Cell Biology and Anatomy, Louisiana State University Health Science Center, 1100 Florida Avenue, Box 137, New Orleans, LA 70119 (United States)

    2011-06-15

    The objectives of this study were to fabricate cross-linked biodegradable polycarbonate nanofibers and to investigate their biodegradability by different enzymes. Poly(2,3-dihydroxycarbonate) was synthesized from naturally occurring l-tartaric acid. The hydroxyl groups on the functional polycarbonate were converted to methacrylate groups to enable the polymer to cross-link under UV irradiation. Smooth cross-linked methacrylated polycarbonate nanofibers (300-1800 nm) were fabricated by a reactive electrospinning process with in situ UV radiation from a mixed solution of linear methacrylated polycarbonate (MPC) and poly(ethylene oxide) (PEO) (MPC:PEO = 9:1) in methanol/chloroform (50/50). These cross-linked nanofibers have shown excellent solvent resistance and their solubility decreases with increasing degree of cross-linking. The thermal properties of linear and cross-linked polycarbonate nanofibers were investigated by differential scanning calorimetry and thermogravimetric analysis. The cross-linked polycarbonate nanofibers show no melting point below 200 {sup 0}C and their decomposition temperature increases with increasing cross-linking degree. Their biodegradation products by five different enzymes were analyzed using liquid chromatography-mass spectrometry (LC-MS). The biodegradability of the polycarbonate nanofibers decreases with increasing cross-linking degree. These nanofibers were found to support human fibroblast survival and to promote cell attachment. This study demonstrates that cross-linked biodegradable polycarbonate nanofibers with different chemical properties and biodegradability can be fabricated using the novel reactive electrospinning technology to meet the needs of different biomedical applications.

  16. Carboxymethyl starch cross-linked by electron beam radiation in presence of acrylic acid sensitizer

    International Nuclear Information System (INIS)

    Doan Binh; Nguyen Thanh Duoc; Pham Thi Thu Hong

    2013-01-01

    Carboxymethyl starch (CMS) can be cross-linked by electron beam radiation to form a biocompatible and environment-friendly hydrogel at a high absorbed dose and a condensed CMS concentration. Acrylic acid (AAc) can be used as a sensitizer in order to reduce the absorbed doses to an acceptable certain level. At an absorbed dose of 3-4 kGy, the gel content of crosslinked CMS can be obtained about 50% with 5% (w/w) AAc concentration used. The compressive strength of CMS samples increased with increasing their cross-linked densities due to raising absorbed doses. The swelling ratio of cross-linked CMS was also attainable at a maximum of 50 times in the distilled water. The enzymatic degradation of cross-linked CMS was carried out in acetate buffer pH 4.6 with 0.1% α-amylase enzymatic solution incubated at 40℃ for 6 h. The crosslinked CMS samples were degraded slower than uncrosslinked CMS ones. The results indicated that the highly cross-linked CMS was almost fully degradable when the enzymatic hydrolysis was performed during 6 h. The FT IR spectra of cross-linked CMS in the presence of AAc were examined to observe the carboxyl group of AAc in the structure of cross-linked CMS. The hydrophilic of cross-linked CMS surface was determined by a contact-angle analysis. (authors)

  17. DNA cross-linking by dehydromonocrotaline lacks apparent base sequence preference.

    Science.gov (United States)

    Rieben, W Kurt; Coulombe, Roger A

    2004-12-01

    Pyrrolizidine alkaloids (PAs) are ubiquitous plant toxins, many of which, upon oxidation by hepatic mixed-function oxidases, become reactive bifunctional pyrrolic electrophiles that form DNA-DNA and DNA-protein cross-links. The anti-mitotic, toxic, and carcinogenic action of PAs is thought to be caused, at least in part, by these cross-links. We wished to determine whether the activated PA pyrrole dehydromonocrotaline (DHMO) exhibits base sequence preferences when cross-linked to a set of model duplex poly A-T 14-mer oligonucleotides with varying internal and/or end 5'-d(CG), 5'-d(GC), 5'-d(TA), 5'-d(CGCG), or 5'-d(GCGC) sequences. DHMO-DNA cross-links were assessed by electrophoretic mobility shift assay (EMSA) of 32P endlabeled oligonucleotides and by HPLC analysis of cross-linked DNAs enzymatically digested to their constituent deoxynucleosides. The degree of DNA cross-links depended upon the concentration of the pyrrole, but not on the base sequence of the oligonucleotide target. Likewise, HPLC chromatograms of cross-linked and digested DNAs showed no discernible sequence preference for any nucleotide. Added glutathione, tyrosine, cysteine, and aspartic acid, but not phenylalanine, threonine, serine, lysine, or methionine competed with DNA as alternate nucleophiles for cross-linking by DHMO. From these data it appears that DHMO exhibits no strong base preference when forming cross-links with DNA, and that some cellular nucleophiles can inhibit DNA cross-link formation.

  18. Permeability to macromolecular contrast media quantified by dynamic MRI correlates with tumor tissue assays of vascular endothelial growth factor (VEGF)

    International Nuclear Information System (INIS)

    Cyran, Clemens C.; Sennino, Barbara; Fu, Yanjun; Rogut, Victor; Shames, David M.; Chaopathomkul, Bundit; Wendland, Michael F.; McDonald, Donald M.; Brasch, Robert C.; Raatschen, Hans-Juergen

    2012-01-01

    Purpose: To correlate dynamic MRI assays of macromolecular endothelial permeability with microscopic area–density measurements of vascular endothelial growth factor (VEGF) in tumors. Methods and material: This study compared tumor xenografts from two different human cancer cell lines, MDA-MB-231 tumors (n = 5), and MDA-MB-435 (n = 8), reported to express respectively higher and lower levels of VEGF. Dynamic MRI was enhanced by a prototype macromolecular contrast medium (MMCM), albumin-(Gd-DTPA)35. Quantitative estimates of tumor microvascular permeability (K PS ; μl/min × 100 cm 3 ), obtained using a two-compartment kinetic model, were correlated with immunohistochemical measurements of VEGF in each tumor. Results: Mean K PS was 2.4 times greater in MDA-MB-231 tumors (K PS = 58 ± 30.9 μl/min × 100 cm 3 ) than in MDA-MB-435 tumors (K PS = 24 ± 8.4 μl/min × 100 cm 3 ) (p < 0.05). Correspondingly, the area–density of VEGF in MDA-MB-231 tumors was 2.6 times greater (27.3 ± 2.2%, p < 0.05) than in MDA-MB-435 cancers (10.5 ± 0.5%, p < 0.05). Considering all tumors without regard to cell type, a significant positive correlation (r = 0.67, p < 0.05) was observed between MRI-estimated endothelial permeability and VEGF immunoreactivity. Conclusion: Correlation of MRI assays of endothelial permeability to a MMCM and VEGF immunoreactivity of tumors support the hypothesis that VEGF is a major contributor to increased macromolecular permeability in cancers. When applied clinically, the MMCM-enhanced MRI approach could help to optimize the appropriate application of VEGF-inhibiting therapy on an individual patient basis.

  19. Nitrogen limitation in natural populations of cyanobacteria (Spirulina and Oscillatoria spp.) and its effect on macromolecular synthesis

    International Nuclear Information System (INIS)

    van Rijn, J.; Shilo, M.

    1986-01-01

    Natural populations of the cyanobacteria Spirulina species and Oscillatoria species obtained from Israeli fish ponds were limited in growth by nitrogen availability in summer. Physiological indicators for nitrogen limitation, such as phycocyanin, chlorophyll a, and carbohydrate content, did not show clear evidence for nitrogen limited growth, since these organisms are capable of vertical migration from and to the nitrogen-rich bottom. By means of 14 C labeling of the cells under simulated pond conditions followed by cell fractionation into macromolecular compounds, it was found that carbohydrates synthesized at the lighted surface were partially utilized for dark protein synthesis at the bottom of these ponds

  20. Comparison of two self-assembled macromolecular prodrug micelles with different conjugate positions of SN38 for enhancing antitumor activity

    Directory of Open Access Journals (Sweden)

    Liu Y

    2015-03-01

    Full Text Available Yi Liu,1 Hongyu Piao,1 Ying Gao,1 Caihong Xu,2 Ye Tian,1 Lihong Wang,1 Jinwen Liu,1 Bo Tang,1 Meijuan Zou,1 Gang Cheng1 1Department of Pharmaceutics, Shenyang Pharmaceutical University, Shenyang, Liaoning Province, People’s Republic of China; 2Department of Food Science, Shenyang Normal University, Shenyang, Liaoning Province, People’s Republic of China Abstract: 7-Ethyl-10-hydroxycamptothecin (SN38, an active metabolite of irinotecan (CPT-11, is a remarkably potent antitumor agent. The clinical application of SN38 has been extremely restricted by its insolubility in water. In this study, we successfully synthesized two macromolecular prodrugs of SN38 with different conjugate positions (chitosan-(C10-OHSN38 and chitosan-(C20-OHSN38 to improve the water solubility and antitumor activity of SN38. These prodrugs can self-assemble into micelles in aqueous medium. The particle size, morphology, zeta potential, and in vitro drug release of SN38 and its derivatives, as well as their cytotoxicity, pharmacokinetics, and in vivo antitumor activity in a xenograft BALB/c mouse model were studied. In vitro, chitosan-(C10-OHSN38 (CS-(10sSN38 and chitosan-(C20-OHSN38 (CS-(20sSN38 were 13.3- and 25.9-fold more potent than CPT-11 in the murine colon adenocarcinoma cell line CT26, respectively. The area under the curve (AUC0–24 of SN38 after intravenously administering CS-(10sSN38 and CS-(20sSN38 to Sprague Dawley rats was greatly improved when compared with CPT-11 (both P<0.01. A larger AUC0–24 of CS-(20sSN38 was observed when compared to CS-(10sSN38 (P<0.05. Both of the novel self-assembled chitosan-SN38 prodrugs demonstrated superior anticancer activity to CPT-11 in the CT26 xenograft BALB/c mouse model. We have also investigated the differences between these macromolecular prodrug micelles with regards to enhancing the antitumor activity of SN38. CS-(20sSN38 exhibited better in vivo antitumor activity than CS-(10sSN38 at a dose of 2.5 mg/kg (P<0

  1. Glycogen-graft-poly(2-alkyl-2-oxazolines) - the new versatile biopolymer-based thermoresponsive macromolecular toolbox

    Czech Academy of Sciences Publication Activity Database

    Pospíšilová, Aneta; Filippov, Sergey K.; Bogomolova, Anna; Turner, S.; Sedláček, Ondřej; Matushkin, Nikolai; Černochová, Zulfiya; Štěpánek, Petr; Hrubý, Martin

    2014-01-01

    Roč. 4, č. 106 (2014), s. 61580-61588 ISSN 2046-2069 R&D Projects: GA ČR GA13-08336S; GA MŠk(CZ) LH14079 Grant - others:AV ČR(CZ) M200501201; AV ČR(CZ) ASCR/CONICET 2012CZ006 Program:M Institutional support: RVO:61389013 Keywords : glycogen * poly(2-alkyl-2-oxazoline) * hybrid copolymer Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.840, year: 2014

  2. Structure analysis of molecular systems in the Institute of Macromolecular Chemistry of the Czech Academy of Sciences

    Czech Academy of Sciences Publication Activity Database

    Hašek, Jindřich

    2010-01-01

    Roč. 17, 2a (2010), k32-k34 ISSN 1211-5894. [Struktura 2010. Soláň, 14.06.2010-17.06.2010] R&D Projects: GA AV ČR IAA500500701; GA ČR GA305/07/1073 Institutional research plan: CEZ:AV0Z40500505 Keywords : Academy of Sciences of the Czech Republic * X-ray structure analysis * crystallography Subject RIV: CD - Macromolecular Chemistry http:// xray .cz/ms/bul2010-2a/hasek.pdf

  3. Hyaluronan microgel as a potential carrier for protein sustained delivery by tailoring the crosslink network

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Chunhong [Department of Materials Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Zhao, Jianhao, E-mail: jhzhao@jnu.edu.cn [Department of Materials Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Engineering Research Center of Artificial Organs and Materials, Ministry of Education, Guangzhou 510632 (China); Tu, Mei; Zeng, Rong; Rong, Jianhua [Department of Materials Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Engineering Research Center of Artificial Organs and Materials, Ministry of Education, Guangzhou 510632 (China)

    2014-03-01

    Hyaluronan (HA) microgels with different crosslink network, i.e. HGPs-1, HGPs-1.5, HGPs-3, HGPs-6 and HGPs-15, were synthesized using divinyl sulfone (DVS) as the crosslinker in an inverse microemulsion system for controlling the sustained delivery of bovine serum albumin (BSA). With increasing the crosslinker content, the average particle size slightly increased from 1.9 ± 0.3 μm to 3.6 ± 0.5 μm by dynamic laser scattering analysis. However, the crosslinker content had no significant effect on the morphology of HA microgels by scanning and transmission electron microscopes. Fourier transform infrared spectroscopy and elemental analysis proved more sulfur participated in the crosslink reaction when raising the crosslinker amount. The water swelling test confirmed the increasing crosslink density with the crosslinker content by calculating the average molecular weight between two crosslink points to be 8.25 ± 2.51 × 10{sup 5}, 1.26 ± 0.43 × 10{sup 5}, 0.96 ± 0.09 × 10{sup 5}, 0.64 ± 0.03 × 10{sup 5}, and 0.11 ± 0.01 × 10{sup 5} respectively. The degradation of HA microgels by hyaluronidase slowed down by enhancing the crosslink density, only about 5% of HGPs-15 was degraded as opposed to over 90% for HGPs-1. BSA loading had no obvious influence on the surface morphology of HA microgels but seemed to induce their aggregation. The increase of crosslink density decreased the BSA loading capacity but facilitated its long-term sustained delivery. When the molar ratio of DVS to repeating unit of HA reached 3 or higher, similar delivery profiles were obtained. Among all these HA microgels, HGPs-3 was the optimal carrier for BSA sustained delivery in this system because it possessed both high BSA loading capacity and long-term delivery profile simultaneously. - Highlights: • HA microgels with different crosslink densities were prepared. • The crosslinker content had little effect on the morphology and size of HA microgels. • The crosslink density

  4. Macromolecular crowding gives rise to microviscosity, anomalous diffusion and accelerated actin polymerization.

    Science.gov (United States)

    Rashid, Rafi; Chee, Stella Min Ling; Raghunath, Michael; Wohland, Thorsten

    2015-04-30

    Macromolecular crowding (MMC) has been used in various in vitro experimental systems to mimic in vivo physiology. This is because the crowded cytoplasm of cells contains many different types of solutes dissolved in an aqueous medium. MMC in the extracellular microenvironment is involved in maintaining stem cells in their undifferentiated state (niche) as well as in aiding their differentiation after they have travelled to new locations outside the niche. MMC at physiologically relevant fractional volume occupancies (FVOs) significantly enhances the adipogenic differentiation of human bone marrow-derived mesenchymal stem cells during chemically induced adipogenesis. The mechanism by which MMC produces this enhancement is not entirely known. In the context of extracellular collagen deposition, we have recently reported the importance of optimizing the FVO while minimizing the bulk viscosity. Two opposing properties will determine the net rate of a biochemical reaction: the negative effect of bulk viscosity and the positive effect of the excluded volume, the latter being expressed by the FVO. In this study we have looked more closely at the effect of viscosity on reaction rates. We have used fluorimetry to measure the rate of actin polymerization and fluorescence correlation spectroscopy (FCS) to measure diffusion of various probes in solutions containing the crowder Ficoll at physiological concentrations. Similar to its effect on collagen, Ficoll enhanced the actin polymerization rate despite increasing the bulk viscosity. Our FCS measurements reveal a relatively minor component of anomalous diffusion. In addition, our measurements do suggest that microviscosity becomes relevant in a crowded environment. We ruled out bulk viscosity as a cause of the rate enhancement by performing the actin polymerization assay in glycerol. These opposite effects of Ficoll and glycerol led us to conclude that microviscosity becomes relevant at the length scale of the reacting

  5. Macromolecular crowding gives rise to microviscosity, anomalous diffusion and accelerated actin polymerization

    Science.gov (United States)

    Rashid, Rafi; Chee, Stella Min Ling; Raghunath, Michael; Wohland, Thorsten

    2015-05-01

    Macromolecular crowding (MMC) has been used in various in vitro experimental systems to mimic in vivo physiology. This is because the crowded cytoplasm of cells contains many different types of solutes dissolved in an aqueous medium. MMC in the extracellular microenvironment is involved in maintaining stem cells in their undifferentiated state (niche) as well as in aiding their differentiation after they have travelled to new locations outside the niche. MMC at physiologically relevant fractional volume occupancies (FVOs) significantly enhances the adipogenic differentiation of human bone marrow-derived mesenchymal stem cells during chemically induced adipogenesis. The mechanism by which MMC produces this enhancement is not entirely known. In the context of extracellular collagen deposition, we have recently reported the importance of optimizing the FVO while minimizing the bulk viscosity. Two opposing properties will determine the net rate of a biochemical reaction: the negative effect of bulk viscosity and the positive effect of the excluded volume, the latter being expressed by the FVO. In this study we have looked more closely at the effect of viscosity on reaction rates. We have used fluorimetry to measure the rate of actin polymerization and fluorescence correlation spectroscopy (FCS) to measure diffusion of various probes in solutions containing the crowder Ficoll at physiological concentrations. Similar to its effect on collagen, Ficoll enhanced the actin polymerization rate despite increasing the bulk viscosity. Our FCS measurements reveal a relatively minor component of anomalous diffusion. In addition, our measurements do suggest that microviscosity becomes relevant in a crowded environment. We ruled out bulk viscosity as a cause of the rate enhancement by performing the actin polymerization assay in glycerol. These opposite effects of Ficoll and glycerol led us to conclude that microviscosity becomes relevant at the length scale of the reacting

  6. Leaching of organic acids from macromolecular organic matter by non-supercritical CO2

    Science.gov (United States)

    Sauer, P.; Glombitza, C.; Kallmeyer, J.

    2012-04-01

    The storage of CO2 in underground reservoirs is discussed controversly in the scientific literature. The worldwide search for suitable storage formations also considers coal-bearing strata. CO2 is already injected into seams for enhanced recovery of coal bed methane. However, the effects of increased CO2 concentration, especially on organic matter rich formations, are rarely investigated. The injected CO2 will dissolve in the pore water, causing a decrease in pH and resulting in acidic formation waters. Huge amounts of low molecular weight organic acids (LMWOAs) are chemically bound to the macromolecular matrix of sedimentary organic matter and may be liberated by hydrolysis, which is enhanced by the acidic porewater. Recent investigations outlined the importance of LMWOAs as a feedstock for microbial life in the subsurface [1]. Therefore, injection of CO2 into coal formations may result in enhanced nutrient supply for subsurface microbes. To investigate the effect of high concentrations of dissolved CO2 on the release of LMWOAs from coal we developed an inexpensive high-pressure high temperature system that allows manipulating the partial pressure of dissolved gases at pressures and temperatures up to 60 MPa and 120° C, respectively. In a reservoir vessel, gases are added to saturate the extraction medium to the desired level. Inside the extraction vessel hangs a flexible and inert PVDF sleeve (polyvinylidene fluoride, almost impermeable for gases), holding the sample and separating it from the pressure fluid. The flexibility of the sleeve allows for subsampling without loss of pressure. Coal samples from the DEBITS-1 well, Waikato Basin, NZ (R0 = 0.29, TOC = 30%). were extracted at 90° C and 5 MPa, either with pure or CO2-saturated water. Subsamples were taken at different time points during the extraction. The extracted LMWOAs such as formate, acetate and oxalate were analysed by ion chromatography. Yields of LMWOAs were higher with pure water than with CO2

  7. Photon-counting single-molecule spectroscopy for studying conformational dynamics and macromolecular interactions

    Energy Technology Data Exchange (ETDEWEB)

    Laurence, Ted Alfred [Univ. of California, Berkeley, CA (United States)

    2002-01-01

    Single-molecule methods have the potential to provide information about conformational dynamics and molecular interactions that cannot be obtained by other methods. Removal of ensemble averaging provides several benefits, including the ability to detect heterogeneous populations and the ability to observe asynchronous reactions. Single-molecule diffusion methodologies using fluorescence resonance energy transfer (FRET) are developed to monitor conformational dynamics while minimizing perturbations introduced by interactions between molecules and surfaces. These methods are used to perform studies of the folding of Chymotrypsin Inhibitor 2, a small, single-domain protein, and of single-stranded DNA (ssDNA) homopolymers. Confocal microscopy is used in combination with sensitive detectors to detect bursts of photons from fluorescently labeled biomolecules as they diffuse through the focal volume. These bursts are analyzed to extract fluorescence resonance energy transfer (FRET) efficiency. Advances in data acquisition and analysis techniques that are providing a more complete picture of the accessible molecular information are discussed. Photon Arrival-time Interval Distribution (PAID) analysis is a new method for monitoring macromolecular interactions by fluorescence detection with simultaneous determination of coincidence, brightness, diffusion time, and occupancy (proportional to concentration) of fluorescently-labeled molecules undergoing diffusion in a confocal detection volume. This method is based on recording the time of arrival of all detected photons, and then plotting the two-dimensional histogram of photon pairs, where one axis is the time interval between each pair of photons 1 and 2, and the second axis is the number of other photons detected in the time interval between photons 1 and 2. PAID is related to Fluorescence Correlation Spectroscopy (FCS) by a collapse of this histogram onto the time interval axis. PAID extends auto- and cross-correlation FCS

  8. Enhanced conjugation stability and blood circulation time of macromolecular gadolinium-DTPA contrast agent

    Energy Technology Data Exchange (ETDEWEB)

    Jenjob, Ratchapol [Department of New Drug Development, School of Medicine, Inha University, 2F A-dong, Jeongseok Bldg., Sinheung-dong 3-ga, Jung-gu, Incheon 400-712 (Korea, Republic of); Kun, Na [Department of Biotechnology, The Catholic University of Korea, 43 Jibong-ro, Wonmi-gu, Bucheon-si, Gyeonggi-do 420-743 (Korea, Republic of); Ghee, Jung Yeon [Utah-Inha DDS and Advanced Therapeutics, B-403 Meet-You-All Tower, SongdoTechnopark, 7–50, Songdo-dong, Yeonsu-gu, Incheon 406-840 (Korea, Republic of); Shen, Zheyu; Wu, Xiaoxia [Division of Functional Materials and Nano-Devices, Ningbo Institute of Materials Technology & Engineering (NIMTE), Chinese Academy of Sciences, 519 Zhuangshi Street, Zhenhai District, Ningbo, Zhejiang 315201 (China); Cho, Steve K., E-mail: scho@gist.ac.kr [Division of Liberal Arts and Science, GIST College, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Lee, Don Haeng [Utah-Inha DDS and Advanced Therapeutics, B-403 Meet-You-All Tower, SongdoTechnopark, 7–50, Songdo-dong, Yeonsu-gu, Incheon 406-840 (Korea, Republic of); Department of Internal Medicine, School of Medicine, Inha University Hospital, Incheon 420-751 (Korea, Republic of); Yang, Su-Geun, E-mail: Sugeun.Yang@Inha.ac.kr [Department of New Drug Development, School of Medicine, Inha University, 2F A-dong, Jeongseok Bldg., Sinheung-dong 3-ga, Jung-gu, Incheon 400-712 (Korea, Republic of)

    2016-04-01

    In this study, we prepared macromolecular MR T1 contrast agent: pullulan-conjugated Gd diethylene triamine pentaacetate (Gd-DTPA-Pullulan) and estimated residual free Gd{sup 3+}, chelation stability in competition with metal ions, plasma and tissue pharmacokinetics, and abdominal MR contrast on rats. Residual free Gd{sup 3+} in Gd-DTPA-Pullulan was measured using colorimetric spectroscopy. The transmetalation of Gd{sup 3+} incubated with Ca{sup 2+} was performed by using a dialysis membrane (MWCO 100–500 Da) and investigated by ICP-OES. The plasma concentration profiles of Gd-DTPA-Pullulan were estimated after intravenous injection at a dose 0.1 mmol/kg of Gd. The coronal-plane abdominal images of normal rats were observed by MR imaging. The content of free Gd{sup 3+}, the toxic residual form, was less than 0.01%. Chelation stability of Gd-DTPA-Pullulan was estimated, and only 0.2% and 0.00045% of Gd{sup 3+} were released from Gd-DTPA-Pullulan after 2 h incubation with Ca{sup 2+} and Fe{sup 2+}, respectively. Gd-DTPA-Pullulan displayed the extended plasma half-life (t{sub 1/2,α} = 0.43 h, t{sub 1/2,β} = 2.32 h), much longer than 0.11 h and 0.79 h of Gd-EOB-DTPA. Abdominal MR imaging showed Gd-DTPA-Pullulan maintained initial MR contrast for 30 min. The extended plasma half-life of Gd-DTPA-Pullulan probably allows the prolonged MR acquisition time in clinic with enhanced MR contrast. - Highlights: • Macromolecule (pullulan) conjugated Gd contrast agent (Gd-DTPA-Pullulan) showed the extended plasma half-life (t{sub 1/2,α} = 0.43 h, t{sub 1/2,β} = 2.32 h) in comparison with Gd-EOB-DTPA • Gd-DTPA-pullulan T1 contrast agent exhibited strong chelation stability against Gd. • The extended blood circulation attributed the enhanced and prolonged MR contrast on abdominal region of rats. • The extended blood circulation may provide prolonged MR acquisition time window in clinics.

  9. Photon-counting single-molecule spectroscopy for studying conformational dynamics and macromolecular interactions

    International Nuclear Information System (INIS)

    Laurence, Ted Alfred

    2002-01-01

    Single-molecule methods have the potential to provide information about conformational dynamics and molecular interactions that cannot be obtained by other methods. Removal of ensemble averaging provides several benefits, including the ability to detect heterogeneous populations and the ability to observe asynchronous reactions. Single-molecule diffusion methodologies using fluorescence resonance energy transfer (FRET) are developed to monitor conformational dynamics while minimizing perturbations introduced by interactions between molecules and surfaces. These methods are used to perform studies of the folding of Chymotrypsin Inhibitor 2, a small, single-domain protein, and of single-stranded DNA (ssDNA) homopolymers. Confocal microscopy is used in combination with sensitive detectors to detect bursts of photons from fluorescently labeled biomolecules as they diffuse through the focal volume. These bursts are analyzed to extract fluorescence resonance energy transfer (FRET) efficiency. Advances in data acquisition and analysis techniques that are providing a more complete picture of the accessible molecular information are discussed. Photon Arrival-time Interval Distribution (PAID) analysis is a new method for monitoring macromolecular interactions by fluorescence detection with simultaneous determination of coincidence, brightness, diffusion time, and occupancy (proportional to concentration) of fluorescently-labeled molecules undergoing diffusion in a confocal detection volume. This method is based on recording the time of arrival of all detected photons, and then plotting the two-dimensional histogram of photon pairs, where one axis is the time interval between each pair of photons 1 and 2, and the second axis is the number of other photons detected in the time interval between photons 1 and 2. PAID is related to Fluorescence Correlation Spectroscopy (FCS) by a collapse of this histogram onto the time interval axis. PAID extends auto- and cross-correlation FCS

  10. Mineral Grains, Dimples, and Hot Volcanic Organic Streams: Dynamic Geological Backstage of Macromolecular Evolution.

    Science.gov (United States)

    Skoblikow, Nikolai E; Zimin, Andrei A

    2018-04-01

    , polycondensation, and formation of proto-cellular structures) are combined within a common dynamic geological process. We suppose macromolecular evolution had an extremely fast, "flash" start: the period from volcanic eruption to formation of lithocyte "populations" took not million years but just several tens of minutes. The scenario proposed can be verified experimentally with a three-module setup working with principles of dynamic (flow) chemistry in its core element.

  11. Improvement of radiation resistance for polytetrafluoroethylene(PTFE) by radiation cross-linking

    International Nuclear Information System (INIS)

    Oshima, Akihiro; Tabata, Yoneho; Ikeda, Shigetoshi; Seguchi, Tadao.

    1996-01-01

    The crosslinked polytetrafluoroethylene(PTFE) was prepared by electron beams irradiation technique in the molten state at 340degC ± 3degC in inert gas atmosphere. The crosslinking density was changed by the irradiation dose. The radiation resistance of crosslinked PTFE was investigated on the mechanical properties after irradiation by γ-rays at room temperature under vacuum and in air. The dose at half value of elongation at break was about 1MGy for 500kGy-crosslinked PTFE, while the dose for non-crosslinked PTFE was only 3.5kGy. It was found that the radiation resistance of PTFE was extremely improved by crosslinking. (author)

  12. Physical Characterization Of High Amylose/Pectin Mixtures Cross-Linked With Sodium Trimetaphosphate

    International Nuclear Information System (INIS)

    Carbinatto, F.M.; Cury, B.S.F.; Evangelista, R.C.

    2010-01-01

    Some researches have reported that pectin and high amylose mixtures presented superior mechanical properties in relation to those of the isolated polymers. In this work, mixtures at different ratios (1:4; 1:1) of pectin and high amylose were crosslinked with sodium trimetaphosphate at different degrees by varying reaction conditions. All samples were characterized by rheological and X-ray diffraction analyses. Samples without cross-linker were prepared as control. The oscillatory dynamic tests showed that all samples exhibited predominant elastic behavior, although cross-linked samples presented higher G' values, suggesting that crosslinking by phosphorylation resulted in more strength structures. The diffractograms showed that cross-linked samples underwent structural modifications that resulted in increase of crystallinity due to cross-linking process. (author)

  13. Biocatalytic cross-linking of pectic polysaccharides for designed food functionality

    DEFF Research Database (Denmark)

    Zaidel, Dayang Norulfairuz Abang; Meyer, Anne S.

    2012-01-01

    the mechanisms of formation of functional pectic polysaccharide cross-links, including covalent cross-links (notably phenolic esters and uronyl ester linkages) and non-covalent, ionic cross-links (which involve calcium and borate ester links). The treatise examines how such cross-links can be designed via......Recent research has demonstrated how cross-linking of pectic polysaccharides to obtain gel formation can be promoted by enzymatic catalysis reactions, and provide opportunities for functional upgrading of pectic polysaccharides present in agro-industrial sidestreams. This review highlights...... specific enzymatic reactions, and highlights the most recent data concerning enzyme catalyzed engineering of cross-links for in situ structural design of functional properties of foods....

  14. Interstrand DNA crosslinking by 4,5',8-trimethylpsoralen plus monochromatic ultraviolet light

    International Nuclear Information System (INIS)

    Cohen, L.F.; Ewig, R.A.G.; Kohn, K.W.; Glaubiger, D.

    1980-01-01

    DNA crosslinking by 4,5',8-trimethylpsoralen plus monochromatic ultraviolet light of wavelength 365 nm was studied in mouse L1210 leukemia cells. DNA breaks and crosslinking were evaluated by alkaline elution of DNA from poly(vinyl chloride) filters. Trimethylpsoralen plus 365 nm light produced DNA crosslinks but not breaks. The kinetics of crosslinging were linear with respect to concentration and second-order with respect to light exposure time. The latter finding supports the proposed two photon mechanism for the formation of diadducts. In contrast to DNA crosslinking agents such as nitrogen mustard, nitrosoureas and platinums, trimethylpsoralen crosslinks were resistant to proteolytic digestion. Thus, trimethylpsoralen plus 365 nm light produced interstrand crosslinks, as proposed for a bifunctional agent binding to bases on opposite DNA strands. (Auth.)

  15. The effect of chain flexibility and chain mobility on radiation crosslinking reactions of polymers

    International Nuclear Information System (INIS)

    Sun Jiazhen

    2003-01-01

    Flexibility of polymer chains is an important factor to effects of radiation crosslinking of the polymer. Polymers with flexible chains are easier to be crosslinked, with lower dose of gelation, than polymers with more rigid chains. And it is known that most polymers with abnormal rigidity can be radiation-crosslinked only at high temperatures when the molecular chains get enough mobility. The flexibility of polymer chains also influences the relationship between degree of degradation and radiation dose. A chain flexibility factor β has been introduced to modify the Charlesby-Pinner equation of sol-fraction and radiation dose. The new relationship equation applies to a wider range of polymers in radiation crosslinking. Studies also show that for flexible polymers with lower T g and molecular internal rotating factor, mechanism of radiation crosslinking is mainly in H type, whereas for rigid polymers with higher T g and molecular internal rotating factor, mechanism of radiation crosslinking is mainly in T type

  16. The Effect of Filler-Polymer Interactions on Cold-Crystallization Kinetics in Crosslinked, Silica Filled PDMS/PDPS Copolymer Melts

    International Nuclear Information System (INIS)

    Chien, A; DeTeresa, S; Thompson, L; Cohenour, R; Balazs, B; Maxwell, R S

    2006-01-01

    Crystallization in a series of variable crosslink density poly(dimethyl-diphenyl) siloxanes random block copolymers reinforced through a mixture of precipitated and fumed silica fillers has been studied by Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), and X-ray Diffraction (XRD). The silicone composite studied was composed of 94.6 mol% Dimethoylsiloxane, 5.1 mol% diphenylsiloxane, and 0.3 mol% methyl-vinyl siloxane (which formed crosslinking after a peroxide cure). The polymer was filled with a mixture of 21.6 wt. % fumed silica and 4.0 wt. % precipitated silica previously treated with 6.8 wt. % ethoxy-endblocked siloxane processing aid. The base composite was characterized by a molecular weight between crosslinks in the polymer network of ∼24 kDa and an overall molecular weight (including the influence of the silica fillers) between crosslinks of ∼11 kDa. Molecular weight between crosslinks and filler-polymer interaction strength were then modified by exposure to γ-irradiation in either air or vacuum. The unirradiated material exhibited crystallization at -80 C as measured by DSC with a 16% crystallization as measured by XRD. Isothermal DMA experiments illustrated that crystallization at -85 C occurred over a 1.8 hour period in silica-filled systems and 2.2-2.6 hours in unfilled systems. The onset of crystallization typically occurred after a 30-minute incubation/nucleation period. The crystallization kinetics were dependent on crosslink density. Changes in molecular weight of a factor of two did not, however, change the amount of crystallization. Irradiation in vacuum resulted in faster overall crystallization rates compared to air irradiation for the same crosslink density, likely due to a reduction in the interaction between the polymer chains and the silica filler surface. Modulated differential scanning calorimetry contrasted the crystallization and melting behavior of pure PDMS versus the PDMS/PDPS base copolymer and helped

  17. Effect of crosslinking agents on chitosan microspheres in controlled release of diclofenac sodium

    OpenAIRE

    Gonçalves,Vanessa L.; Laranjeira,Mauro C. M.; Fávere,Valfredo T.; Pedrosa,Rozângela C.

    2005-01-01

    In this work chitosan microspheres were prepared by the simple coacervation method and crosslinked using epichlorhydrin or glutaraldehyde for the controlled release of diclofenac sodium. The effects of the crosslinking agents on chitosan microspheres over a 12-hour period were assessed with regard to swelling, hydrolysis, porosity, crosslinking, impregnation of diclofenac sodium (DS), and consequently to the release of DS in buffer solutions, simulating the gastrointestinal tract. The degree ...

  18. Polymeric Micelles with Ionic Cores Containing Biodegradable Crosslinks for Delivery of Chemotherapeutic Agents

    OpenAIRE

    Kim, Jong Oh; Sahay, Gaurav; Kabanov, Alexander V.; Bronich, Tatiana K.

    2010-01-01

    Novel functional polymeric nanocarriers with ionic cores containing biodegradable cross-links were developed for delivery of chemotherapeutic agents. Block ionomer complexes (BIC) of poly(ethylene oxide)-b-poly(methacylic acid) (PEO-b-PMA) and divalent metal cations (Ca2+) were utilized as templates. Disulfide bonds were introduced into the ionic cores by using cystamine as a biodegradable cross-linker. The resulting cross-linked micelles with disulfide bonds represented soft, hydrogel-like n...

  19. Covalent Crosslinking of Porous Poly(Ionic Liquid) Membrane via a Triazine Network

    OpenAIRE

    Täuber, Karoline; Dani, Alessandro; Yuan, Jiayin

    2017-01-01

    Porous poly(ionic liquid) membranes that were prepared via electrostatic cross-linking were subsequently covalently cross-linked via formation of a 1,3,5-triazine network. The additional covalent cross-links do not affect the pore size and pore size distribution of the membranes and stabilize them towards salt solutions of high ionic strength, enabling the membranes to work in a broader environmental window.

  20. Molecular and macro-scale analysis of enzyme-crosslinked silk hydrogels for rational biomaterial design.

    Science.gov (United States)

    McGill, Meghan; Coburn, Jeannine M; Partlow, Benjamin P; Mu, Xuan; Kaplan, David L

    2017-11-01

    Silk fibroin-based hydrogels have exciting applications in tissue engineering and therapeutic molecule delivery; however, their utility is dependent on their diffusive properties. The present study describes a molecular and macro-scale investigation of enzymatically-crosslinked silk fibroin hydrogels, and demonstrates that these systems have tunable crosslink density and diffusivity. We developed a liquid chromatography tandem mass spectroscopy (LC-MS/MS) method to assess the quantity and order of covalent tyrosine crosslinks in the hydrogels. This analysis revealed between 28 and 56% conversion of tyrosine to dityrosine, which was dependent on the silk concentration and reactant concentration. The crosslink density was then correlated with storage modulus, revealing that both crosslinking and protein concentration influenced the mechanical properties of the hydrogels. The diffusive properties of the bulk material were studied by fluorescence recovery after photobleaching (FRAP), which revealed a non-linear relationship between silk concentration and diffusivity. As a result of this work, a model for synthesizing hydrogels with known crosslink densities and diffusive properties has been established, enabling the rational design of silk hydrogels for biomedical applications. Hydrogels from naturally-derived silk polymers offer versitile opportunities in the biomedical field, however, their design has largely been an empirical process. We present a fundamental study of the crosslink density, storage modulus, and diffusion behavior of enzymatically-crosslinked silk hydrogels to better inform scaffold design. These studies revealed unexpected non-linear trends in the crosslink density and diffusivity of silk hydrogels with respect to protein concentration and crosslink reagent concentration. This work demonstrates the tunable diffusivity and crosslinking in silk fibroin hydrogels, and enables the rational design of biomaterials. Further, the characterization methods