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  • 1
    Electronic Resource
    Electronic Resource
    Reaction path and free energy calculations of the transition between alternate conformations of HIV-1 proteaseThe content of this publication does not necessarily reflect the views or policies of the Department of Health and Human Services, nor does mention of trade names, commercial products, or organization imply endorsement by the U.S. Government. (1998)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 32 (1998), S. 7-16 
    Details
    ISSN: 0887-3585
    Keywords: conformational change ; free energy calculations ; HIV protease ; molecular dynamics simulations ; protein structure ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Two different structures of ligand-free HIV protease have been determined by X-ray crystallography. These structures differ in the position of two 12 residue, β-hairpin regions (or “flaps”) which cap the active site. The movements of the flaps must be involved in the binding of substrates since, in either conformation, the flaps block the binding site. One of these structures is similar to structures of the ligand-bound enzyme; however, the importance of both structures to enzyme function is unclear. This transformation takes place on a time scale too long for conventional molecular dynamics simulations, so the process was studied by first identifying a reaction path between the two structures and then calculating the free energy along this path using umbrella sampling. For the ligand-free enzyme, it is found that the two structures are nearly equally stable, with the ligand-bound-type structure being less stable, consistent with X-ray crystallography data. The more stable open structure does not have a lower potential energy, but is stabilized by entropy. The transition occurs through a collapse and reformation of the β-sheet structure of the conformationally flexible, glycine-rich flap ends. Additionally, some problems in studying conformational changes in proteins through the use of a single reaction path are addressed. Proteins 32:7-16, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Substitution of poly(chlorotrifluoroethylene) with sulfur dioxide under reductive conditionsDedicated to Prof. William E. McEwen on the occasion of his seventy-fifth birthday. (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Heteroatom Chemistry 9 (1998), S. 265-269 
    Details
    ISSN: 1042-7163
    Keywords: Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of Poly(chlorotrifluoroethylene) (in the forms of Kel-F 6061 and Neoflon M400H) with Zn/SO2 in DMF results in substitution of the chloride ligand with the sulfinic acid moiety. Subsequent oxidation affords the sulfonic acid. The materials are characterized by elemental analysis, titration, scanning electron microscopy, and FT-IR. ATR-IR studies indicate that functionalization is probably not a surface-selective phenomenon. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:265-269, 1998
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Patents in combi-space: Patent challenges in combinatorial chemistry (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 61 (1998), S. 69-75 
    Details
    ISSN: 0006-3592
    Keywords: combinatorial chemistry ; library ; array ; patent ; utility ; description requirement ; piracy ; algorithm ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Patent protection of inventions relating to combinatorial chemistry is attended by special challenges. The “breakthrough” nature of the field together with the always complex and often arcane chemical manipulations, apparatus, and strategies which suffuse this field make it difficult to describe the inventions adequately. It can be a challenge to communicate effectively with official authorities charged with patent examination. Extraordinary effort is called for in clarifying such inventions such that their patentability can be appreciated. The utility of some types of inventions in this field may be open to question; clear statements of at least one acceptable utility - even if only a minor utility - is beneficial. Because a principal product of many aspects of combinatorial chemistry is information, e.g., the identification of a lead compound, offshore “piracy” is a risk. Domestic claim tie-ins may improve the ability to abate such piracy. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng (Comb Chem) 61:69-75, 1998.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of fibrin micromorphology on neurite growth from dorsal root ganglia cultured in three-dimensional fibrin gels (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 551-559 
    Details
    ISSN: 0021-9304
    Keywords: nerve regeneration ; fibrin tissue adhesive ; fibrinogen ; coagulation ; electron microscopy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The effect of fibrin matrix micromorphology on neurite growth was investigated by measuring the length of neurites growing in three-dimensional fibrin gels with well characterized micromorphologies. Dorsal root ganglia (DRGs) from 7-day chick embryos were entrapped and cultured in gels made from varying concentrations of fibrinogen (5-15 mg/mL) or calcium (2-10 mM). The length of growing neurites was measured with light videomicroscopy, and the number and diameter of fibrin fiber bundles were measured from scanning electron micrographs. An increase in fibrinogen concentration caused a decrease in the average fiber bundle thickness, an increase in the number of fiber bundles, and a marked decrease in neurite length. Gels made with different calcium concentrations had a similar range of variation in fibrin fiber bundle number or diameter, but these variations had little effect on neurite and associated nonneuronal cell outgrowth. These results provide insights into the process of neurite advance within fibrin and may be useful in the design of fibrin-based materials used for peripheral nerve regeneration. Furthermore, this study provides the first detailed experimental data on the micromorphology of fibrin matrices made from more than 5 mg/mL of fibrinogen and indicates that existing kinetic models of fibrin polymerization do not accurately predict fibrin structure at these higher concentrations. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 551-559, 1998.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Microbial removal of alkanes from dilute gaseous waste streams: Mathematical modeling of advanced bioreactor systems (1998)
    Chichester : Wiley-Blackwell
    Journal of Chemical Technology AND Biotechnology 72 (1998), S. 93-98 
    Details
    ISSN: 0268-2575
    Keywords: VOC ; biodegradation ; alkanes ; trickle-bed ; mass transfer ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Many industries generate volatile organic compounds (VOCs) in dilute streams which must be removed before being released into the environment. Mathematical models for biological filters which can remediate waste streams are useful both as predictive tools and as a means to better understand the fundamental processes involved. Optimization of the system also necessitates a better understanding of the mechanisms by which biofilters work and can be approached through modeling and maximizing appropriate conditions for removal. In a trickle-bed bioreactor, VOCs (n-pentane and isobutane) were passed over a biofilm-coated packing which degraded the VOCs. Bacterial growth was controlled via liquid nutrient-limited media trickled through the reactor. Results from this trickle-bed system were analyzed by applying a simple mathematical model to accurately describe the processes which are believed to play important roles. The model was based on a two-step process: mass transfer in which the VOCs diffuse into the liquid biofilm, and kinetics by which VOCs are degraded by the biofilm. Modeling results revealed that both kinetic and mass transfer resistances were significant under typical operating conditions.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Development of separation systems for polynuclear aromatic hydrocarbon environmental contaminants using micellar electrokinetic chromatography with molecular micelles and free zone electrophoresis (1998)
    Weinheim : Wiley-Blackwell
    Electrophoresis 19 (1998), S. 2090-2094 
    Details
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; Polynuclear aromatic hydrocarbons ; Laser-induced fluorescence ; Molecular micelles ; Environmental analysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Of four systems available from the literature, based on cyclodextrins, dioctyl-sulfosuccinate, bile salts, and molecular micelles consisting of oligomers of undecylenic acid, the most successful separation system in our hands is based on the molecular micelles, oligomers of sodium undecylenic acid (OSUA). We have employed organic additives of acetonitrile, acetone, and tetrahydrofuran in achieving separations of polyaromatic hydrocarbons (PNAs) using molecular micelles. Generally, successful separations are achieved with 20-40% composition as the organic additive in an 8 mM borate buffer. We separated 16 PNAs with 20% tetrahydrofuran in a system of 8 mM borate and 0.125 g/ 10 mL (ca. 6.25 mM) of OSUA. Typical extracts of environmental samples contain additional analytes besides the typical 16 target compounds. Among these are the nitrogen-containing aromatics that can act as cations under conditions of low pH and additional compounds that can act as anions under basic conditions in free-zone electrophoresis. These additional classes of analytes are separated by capillary zone electrophoresis/laser-induced fluorescence detection using a frequency-doubled laser operated at 257 nm.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150191208
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  • 7
    Electronic Resource
    Electronic Resource
    Capillary electrophoresis/laser-induced fluorescence detection of fluorescein as a groundwater migration tracer (1998)
    Weinheim : Wiley-Blackwell
    Electrophoresis 19 (1998), S. 2252-2256 
    Details
    ISSN: 0173-0835
    Keywords: Capillary zone electrophoresis ; Fluorescent dyes ; Ground-water tracers ; Laser-induced fluorescence ; Solid-phase extraction ; Fluorescein ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Capillary electrophoresis (CE) has been applied to the determination of the groundwater migration tracer dye fluorescein based on laser-induced fluorescence (LIF) detection and compared to determinations obtained with traditional spectrofluorimetry. Detection limits of injected dye in the low parts per trillion (ppt) ranges have been accomplished with both CE/LIF based on the Ar ion laser and with a spectrofluorimeter. This approach was used for a real-world problem in determining groundwater migration between adjacent Resource Conservation and Recovery Act (RCRA) and Superfund sites by the Environmental Sciences Division in response to regional needs and as application of new analytical tools under development. Fluorescent dye was injected into source wells and then was determined in monitoring wells by extracting pads that adsorbed the dye or by directly determining the dye in the water using solid-phase extraction (SPE), a preconcentration technique. The approaches based on CE/LIF exhibits increased specificity over existing approaches due to the separation and unique migration time of the dye. Additional studies were aimed at achieving sub-ppt levels in the water using solid-phase extraction and field-amplified injection techniques.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150191234
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