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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 16 (1993), S. 246-267 
    ISSN: 0887-3585
    Keywords: generic binding cavity ; ligand design ; site-filling peptides ; effects of pH on binding D- and L-enantiomers ; immunoglobulin light chain dimer ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An immunoglobulin light chain dimer with a large generic binding cavity was used as a host molecule for designing a series of peptide guest ligands. In a screening procedure peptides coupled to solid supports were systematically tested for binding activity by enzyme linked immunosorbent assays (ELISA). Key members of the binding series were synthesized in milligram quantities and diffused into crystals of the host molecule for X-ray analyses. These peptides were incrementally increased in size and affinity until they nearly filled the cavity. Progressive changes in binding patterns were mapped by comparisons of crystallo-graphically refined structures of 14 peptide-protein complexes at 2.7 Å resolution. These comparisons led to guidelines for ligand design and also suggested ways to modify previously established binding patterns. By manipulating equilibria involving histidine, for example, it was possible to abolish one important intramolecular interaction of the bound ligand and substitute another. These events triggered a change inconformation of the ligand from a compact to an extended form and a comprehensive change in the mode of binding to the protein. In dipeptides of histidine and proline, protonation of both imidazolium nitrogen atoms was used to program anend-to-end reversal of the direction in which the ligand was inserted into the binding cavity. Peptides cocrystallized with proteins produced complexes somewhat different in structure from those in which ligandswere diffused into preexisting crystals. In sucha large and malleable cavity, space utilization was thus different when a ligand was introduced before the imposition of crystal packing restraints. © 1993 Wiley-Liss, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 502-506 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: This study addresses a problem inherent in the use of microchannel plates as detectors for matrix-assisted laser desorption/ionization. We have developed a unique new method of ion transport using fast bipolar pulsing of an electrostatic particle guide to provide ion deflection and enhanced ion transmission. This mode of operation effectively eliminates the intense low-mass component of the spectrum which normally saturates microchannel -plate detectors, while at the same time transporting the higher-mass component with high efficiency. Enhancement of the resulting signal-to-noise ratio has been achieved.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1042-7147
    Keywords: X-ray and deep UV lithography ; Photoacid generators ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The X-ray (1.4 nm) and deep UV (248 nm) radiation responses of chemically amplified photoresists incorporating arylmethyl sulfone photoacid generators were evaluated. The arylmethyl sulfones were primarily derivatives of benzyl phenyl sulfone, selected to reveal the importance of desulfonylation and internal abstraction with regard to the photochemical efficiency of acid generation. At 1.4 nm, benzyl phenyl sulfone gave a much more sensitive resist than dibenzyl sulfone, while the methyl derivatives of benzyl phenyl sulfone did not give much improvement over the parent compound. This suggests that desulfonylation is more important than internal abstraction for increased photochemical efficiency. At 248 nm, similar trends were observed, but with some modifications arising from the variation in extinction coefficient among the sulfones. Sensitivities at or below 20 mJ/cm2 were obtained for both wavelength ranges.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 9 (1969), S. 405-414 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The changes occurring when polythene melts are subjected to shear, have been investigated using a rotating bob fitted into a ram extruder. In addition to chain scission, low density polythene exhibits reversible changes in mechanical and viscoelastic properties. The magnitude of the changes is controlled by total shear strain, and is related to molecular weight and long chain branching. The mechanism appears to be one of reversible disentanglement operating mainly on the large highly branched molecules. The work is relevant to various extrusion processes and to other long-branched polymers.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 619-647 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The specific sorption capacities of poly(styrene-co-divinylbenzene) [i.e., (Sty)1-x (DVB)x samples for binary solutions of toluene (α = 1.98)] and a second solvent [i.e., heptane (α = 〈0.01), methanol (α = 〈0.06), acetone (α = 0.92) or chloroform (α = 3.00)] were correlated with the corresponding DVB mole fraction (x) in the sorbent polymer samples (0.01 〈 x 〈 0.11), with the volume fraction (z) of toluene in the sorbed binary liquid (which was cycled at least twice from z = 0 to z = 1 and back to z = 0 in increments of 0.1) and with the adsorption parameter (α) of the sorbed liquid. These correlations demonstrated that the sorption capacity during the initial transit from z = 0 to 1 reflects the molecular architecture in the original dry state. Once the samples have been swelled to saturation in toluene (z = 1), however, the “memory” of the former dry state is erased; thereafter the sorption capacity reflects only the architecture established in the fully swollen state, and the composition of the sorbed solution. The molecular nature of the solvent exchange processes is discussed in the text. © 1994 John Wiley & Sons, Inc.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1476-1480 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The X-ray and deep UV radiation response is described for resist systems consisting of poly(4-tert-butoxycarbonyloxystyrene-co-sulfur dioxide) PTBSS combined with an arylmethyl sulfone. A 2:1 4-tert-butoxycarbonyloxystyrene (TBS): sulfur dioxide (SO2) resist has been found to function as a highly sensitive, 1.4 nm X-ray, single-component, chemically amplified resist. The same resist, however, exhibits reduced sensitivity to 0.8 nm X-rays and deep UV (248 nm) radiation. Improvement in 0.8 nm X-ray sensitivity is achieved by the addition of 12 mol% bis(3,4-dichlorobenzyl) sulfone (DCBS) to the 2:1 TBS:SO2 resist. For this two-component resist formulation, the 0.8 nm X-ray sensitive improved from 〉375 to 125 mJ/cm2. Similarly, the sensitivity of the 3:1 TBS:SO2 copolymer to deep UV radiation improves to 40 mJ/cm2 with addition of 10 mol% DCBS. Sulfones, such as DCBS, provide two-component resist formulations capable of 〈0.5 μm resolution.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1565-1570 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The lithographic performance of chemically amplified positive resists depends on controlling the delay time between the exposure and post-exposure bake (PEB) process steps. The effect of post-exposure delay (PED) was investigated in poly(t-butoxycarbonyloxystyrene-sulfone) formulated with photoacid generators (PAG) by a variety of analytical techniques including Rutherford backscattering, infrared, X-ray photoelectron and laser ablation microprobe mass spectrometry. The results indicate that the base-insoluble residue formed during PED is primarily a surface phenomenon and is a result of incomplete deprotection at the resist surface. It was determined that ppb levels of basic vapors present in the resist processing environment affect process performance profoundly by reacting with the photogenerated acids during PED. Isolation of resist surface from the immediate environment by means of a thin, acidic, and base-soluble overcoat (covercoat) material dramatically alleviates the environmental effects by quenching basic airborne contaminants and improves PED latitude.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 17 (1975), S. 1591-1598 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The batch growth curves of Laclobacillus delbreuckii exhibit several exponential phases. From the results of a series of shaker flask experiments, the position of the slope changes in the growth curve and the overall bacterial yield is affected by the initial amount of yeast extract in the medium. It is postulated that this behavior is due to several growth enhancing substances that are initially in the yeast extract and are consumed by the bacteria during the course of the fermentation. Using a Monod-type expression to represent the effect of growth enhancing components in a proposed growth rate expression, a mathematical model of the system is set up and solved on the analog computer.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 16 (1974), S. 1507-1516 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Ribulose-1,5-diphosphate carboxylase from spinach has been bound to arylamine porous glass with a diazo linkage and to alklamine porous glass with glutaraldehyde. Stability at elevated temperatures and responses to changes of pH and ribulose-1,5-diphosphate, Mg2+, and dithiothreitol concentrations were not significantly different from the soluble enzyme, though stability at 4°C was somewhat improved.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The fermentation kinetics of the homofermentative organism Lactobacillus delbrueckii in a glucose-yeast extract medium is studied in both batch and continuous culture under conditions of controlled pH. From a graphical analysis of the batch data, a mathematical model of the process is derived which relates bacterial growth, glucose utilization, and lactic acid formation. The parameters in the model represent the activity of the organism and are a function of pH, having a maximum value at about 5.90. In a continuous stirred tank fermentor (CSTF), the effect of pH, feed concentration, and residence time is observed. The feed medium is a constant ratio of two parts glucose to one part yeast extract plus added mineral salts. An approximate prediction of the steady-state behavior of the CSTF can be made using a method based on the kinetic model derived for the batch case. In making step changes from one steady state to another, the transient response is observed. Using the kinetic model to simulate the transient period, the calculated behavior qualitatively predicts the observed response.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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