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  • 1
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 23 (1995), S. 73-82 
    ISSN: 0887-3585
    Schlagwort(e): protein folding ; protein structure ; genetic algorithms ; Monte Carlo simulations ; ring closure ; dihedral angles ; structure prediction ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: We have enhanced genetic algorithms and Monte Carlo methods for simulation of protein folding by introducing “local moves” in dihedral space. A local move consists of changes in backbone dihedral angles in a sequential window while the positions of all atoms outside the window remain unchanged. We find three advantages of local moves: (1) For some energy functions, protein conformations of lower energy are found; (2) these low energy conformations are found in fewer steps; and (3) the simulations are less sensitive to the details of the annealing protocol. To distinguish the effectiveness of local move algorithm from the complexity of the energy function, we have used several different energy functions. These energy functions include the Profile score (Bowie et al., Science 253:164-170, 1991), the knowledge-based energy function used by Bowie and Eisenberg 1994 (Proc. Natl. Acad. Sci. U.S.A. 91:4434-4440, 1994), two energy terms developed as suggested by Sippl and coworkers (Hendlich et al., J. Mol. Biol. 216:167180, 1990), and AMBER (Weiner and Kollman, J. Comp. Chem. 2:287-303, 1981). Besides these energy functions we have used three energy functions that include knowledge of the native structures: the RMSD from the native structure, the distance matrix error, and an energy term based on the distance between different residue types called DBIN. In some of these simulations the main advantage of local moves is the reduced dependence on the details of the annealing schedule. In other simulations, local moves are superior to other algorithms as structures with lower energy are found. © 1995 Wiley-Liss, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 133-139 
    ISSN: 0006-3592
    Schlagwort(e): hybridoma ; kinetics ; curve fitting ; fermentation ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The use of partial cubic spline data interpolation for the calculation of volumetric metabolite exchange rates suggested the existence of three distinct metabolic phases during bioreactor culture of a hybridoma cell line. During phase 1, a rapid amino acid uptake rate and ammonia release rate were observed. The growth rate was low and glutamine synthetase activity fell. In phase 2, maximum growth rate and minimum glutamine assimilation and ammonium production rates were observed. Attempts to corroborate the apparent ammonia assimilation in this phase using 15NH4Cl resulted in low incorporation rates into alanine and glutamine. Maximum glutamine synthetase activity took place during this period. Maximum antibody production rate was observed during phase 3 during which peaks in glutamine assimilation, ammonia release, and glutamine synthetase activity were observed. The apparent existence of the three phases prompted us to carry out Northern blot analysis of glutamine synthetase RNA at appropriate times during the process. This revealed a pattern of appearance and dis-appearance of mRNA consistent with the three phases indicated by the fermentation parameters. © 1993 John Wiley & Sons, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 1099-1106 
    ISSN: 0006-3592
    Schlagwort(e): hybridoma ; fed batch ; materials balancing ; fermentation ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Hybridoma batch cultures were extended using feed formulations based on nutrient consumption measured during different batch culture phases when (a) growth but negligible antibody production was taking place; (b) maximum antibody production rate and declining viable cell growth rate were observed. Strategy (a) was the more successful (2.8-fold compared with 1.8-fold antibody titer increase) and maintained cell viability for longer. Analysis of the effects of omitting individual amino acids yielded results which were consistent with those from the feeding experiment © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1076-5174
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: High-performance liquid chromatography megaflow electrospray tandem mass spectrometry (HPLC/ES-MS/MS) with an on-line radioisotope detector was used to identify [2,4,6-14C] atrazine degradation products generated by treatment with Fenton's reagent (Fe2+ and H2O2). Fenton's reagent produced dealkylated and/or partially oxidized [2,4,6-14C] atrazine products in preference to dechlorinated products. Seven major products were identified by collision-induced dissociation spectra: 4-acetamido-2-chloro-6-(isopropylamino)-s-triazine, 4-amino-2-chloro-6-(isopropylamino)-s-triazine, 4-acetamido-2-chloro-6-(ethylamino)-s-triazine, 6-amino-2-chloro-4-(ethylamino)-s-triazine, 4-acetamido-6-amino-2-chloro-s-triazine, 2-chloro-4,6-diamino-s-triazine and the first report of 4-acetamido-2-hydroxy-6-(isopropylamino)-s-triazine. HPLC/ES-MS/MS provided a rapid method for identifying a wide range of atrazine transformation products in aqueous samples and obviated the need for fraction collection, extraction, and chemical derivatization of the more polar atrazine products. Furthermore, because analyte retention times in HPLC/UV and HPLC/ES-MS/MS were similar, compound identities determined using the latter could be directly assigned to peaks in UV chromatograms.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 5
    ISSN: 0006-3592
    Schlagwort(e): drug delivery ; tissue engineering ; surface modification ; polymer ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: We describe the development of a novel biodegradable polymer designed to present bioactive motifs at the surfaces of materials of any architecture. The polymer is a block copolymer of biotinylated poly(ethylene glycol) (PEG) with poly(lactic acid) (PLA); it utilizes the high-affinity coupling of the biotin-avidin system to undergo postfabrication surface engineering. We show, using surface plasmon resonance analysis (SPR) and confocal microscopy that surface engineering can be achieved under aqueous conditions in short time periods. These surfaces interact with cell surface molecules and generate beneficial responses as demonstrated by the model study of integrin-mediated spreading of endothelial cells on polymer surfaces presenting RGD peptide adhesion sequences. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58: 529-535, 1998.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 27 (1982), S. 3597-3620 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Open-bath, organic liquid treatments may be used to produce high surface area PET fibers through the action of liquid solvent-induced crystallization (SINC). It has been found that as the treatment bath temperature is increased, surface modification suddenly disappears. For a particular treatment method this occurs at a reproducible temperature, well below the liquid boiling point. A qualitative understanding of the mechanism of surface cavitation during liquid SINC is developed based on current descriptions of the component processes involved. These processes are: the glass-rubber transition, diffusion through rubbery and glassy polymer, and polymer-diluent crystallization. Although calculations of the threshold concentration for swelling support this conceptual framework, the absence of surface cavitation at higher treatment bath temperatures is not explained by it and is therefore attributed to an intervening phenomenon. Analysis of penetration depth data together with surface microscopy suggest the formation of a smooth surface layer interfering with normally observed cavitation at elevated temperatures. Manipulation of the extent of vapor precontact shows that vapor SINC prior to liquid exposure is most likely responsible for the smooth layer.
    Zusätzliches Material: 21 Ill.
    Materialart: Digitale Medien
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  • 7
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The design of biomaterials containing specific ligands on the surface offers the possibility of creating materials that can interact with and potentially control mammalian cell behavior. Biodegradable materials further provide the significant advantage that the polymer will disappear in vivo, obviating long-term negative tissue responses as well as the need for retrieval. In earlier studies we synthesized and characterized arginine - glycine - aspartic acid (RGD) peptide-modified poly(lactic acid-co-lysine) (PLAL). In this study, both bulk properties and surface features have been characterized, with a focus on surface analysis as a means of interpreting observed changes in cell behavior. Bulk peptide attachments were performed using 1,1′-carbonyldiimidazole (CDI). Amino groups were measured using colorimetric assays and X-ray photoelectron spectroscopy (XPS). Peptides were measured by incorporating iodine into the peptide as a distinct elemental marker for use with XPS. Typical samples contained 13 ± 4 pmol/cm2 of amino groups and 4 ± 0.2 pmol/cm2 of peptides, as calculated from XPS measurements of nitrogen and iodine. The wettability and crystallinity of the samples were determined by contact angles and differential scanning calorimetry, respectively. Wettability and crystallinity were not altered by the incorporation of lysine or peptides. After incubating bovine aortic endothelial (BAE) cells for 4 h on surfaces with RGD-containing peptides, the mean spread cell area increased from 77 ± 2 μm2 to 405 ± 29 μm2 compared to 116 ± 11 μm2 on poly(lactic acid), 87 ± 4 μm2 on PLAL, and 105 ± 4 μm2 on surfaces with RDG-containing (control) peptides. The significance of this work is that the first synthetic interactive, resorbable biomaterial has been developed, and use of this material to control cell behavior has been demonstrated. © 1997 John Wiley & Sons, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 8
    ISSN: 0044-8249
    Schlagwort(e): Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 9
    ISSN: 0570-0833
    Schlagwort(e): Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 16 (1985), S. 193-201 
    ISSN: 0377-0486
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Surface-enhanced Raman scattering spectra of aqueous silver horohydride sols of pyridine, pyridine-4-d, pyridine-2,6-d2 and pyridine-3,5-d2 are reported. Depolarization ratios are given as a function of pyridine concentration for a number of pyridine bands over a substantial range of concentrations. Evidence is presented of multiple site adsorption and a new interpretation of these Raman spectra is proposed. The evidence indicates that the surface enhancement derives essentially from the presence of long linear segments of chains of silver spheres in the aggregating sols. The concentration dependence of the depolarization ratios and of the average silver sol particle size show that the depolarization ratio characterizes the extent of dendritic growth of sol aggregates and is thus the same for every Raman band in a given preparation at the same time in the history of its evolution, independent of the rotational characteristics of the sol particles or of the adsorbed pyridine molecules.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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