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  • Wiley-Blackwell  (12)
  • Oxford University Press  (4)
  • American Chemical Society (ACS)
  • 1990-1994  (16)
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  • 1991  (16)
  • 1
    Electronic Resource
    Electronic Resource
    Conformations and time-resolved fluorescence of oligomers of (-)-epicatechin with 4β → 8 interflavan bonds (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 537-545 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oligomers of (-)-epicatechin with 4β → 8 interflavan bonds, and as many as five monomer units, have been studied by conformational analysis and time-resolved fluorescence. The conformational analysis yields 2x-1 conformations for each oligomer with x monomer units. There are two conformations accessible at each interflavan bond. These conformations are denoted by + and -. The dominant conformations for the trimer and higher oligomers have an interaction between the phenolic hydroxyl groups on monomers i and i+2. This interaction involves the hydroxyl group at C(5) on monomer i, and either C(13) or C(8) of monomer i+2, depending on whether the conformation of the two intervening interflavan bonds is + + or + -, respectively. Minor contributions to the ensemble for the tetramer and pentamer are made by conformations that contain the sequence of successive interflavan bonds denoted by -+ or --. In -+ the interaction between monomer units i and i + 2 involves an aliphatic hydroxyl with a phenolic hydroxyl, and there are no hydroxyl-hydroxyl interactions between units iand i + 2 in --. The onset of a different decay law for the fluorescence when x increases from 3 to 4 may be associated with the appearance of the -+ and -- conformations as minor constituents in the ensemble.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360310509
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  • 2
    Electronic Resource
    Electronic Resource
    Spray-to-bubbly transition for distillation systems containing two liquid phases (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 597-606 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The tray hydrodynamics were determined for a system containing water and kerosene as immiscible liquids. Plates with hole diameters ranging from 3.18 to 12.70 mm were used in a 44.5-cm2 perspex air-water-kerosene simulator. Experiments were also carried out in a 50-mm-ID column using different depths of oil and water mixtures to study the drop and bubble mechanisms. A spray-to-bubble transition occurred for the two liquid-phase system experiments. The liquid holdup at the transition increased directly with gas velocity and hole diameter, and decreased with increasing free area. At the same hole velocity, the presence of two liquid phases caused the transition to occur at different liquid holdups than for the single pure liquid. Two different modes of coalescence were observed in the small column work. New correlations have been proposed for the liquid holdup at the transition which allow for the presence of two liquid phases.
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690370413
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  • 3
    Electronic Resource
    Electronic Resource
    Ion exchange and affinity chromatography in the scaleup of the purification of α-galactosidase from soybean seeds (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 356-363 
    Details
    ISSN: 0006-3592
    Keywords: α-galactosidase ; soybeans ; lectin ; scaleup ; chromatography ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Soybeans (Glycine max) contain an α-galactosidase that makes up a small fraction of the total protein of the seed. The properties of this enzyme are of interest because of its potential to convert the galactooligosaccharides, stachyose and raffinose, in soybean meal to sugars digestible in the human gastro intestinal tract and thereby increase potential uses of this vegetable protein source in human and animal foods. Study of this enzyme required the isolation of milligram quantities of electrophoretically pure protein from ground soybeans and therefore, scaleup of laboratory procedures by a factor of 300 times. Large scale acid precipitation, ammonium sulfate precipitation, and centrifugal recovery of the precipitated protein allowed α-galactosidase to be isolated from 45.5 kg soybean meal containing 17.1 kg protein, to obtain an enzyme extract with a specific activity of 90 to 100. A novel combination of strong anion exchange and cation exchange chromatography followed by Concanavalin-A affinity chromatography with a methyl α-D mannoside gradient gave α-galactosidase with an average specific activity of 56,000. Ion exchange chromatography preceding Concanavalin-A affinity chromatography allowed elimination of a relatively costly melibiose affinity chromatography step (which followed the Concanavalin-A column In the laboratory procedure) thereby making scaleup practical.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370409
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  • 4
    Electronic Resource
    Electronic Resource
    Investigation of products arising from enzymatic digestion of advanced glycated albumin by high-performance liquid chromatography/mass spectrometry (1991)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 5 (1991), S. 624-628 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The structural investigation of the products arising from 28 days incubation of albumin with high glucose concentration and further enzymatic hydrolysis has been carried out by means of high-performance liquid chromatography/mass spectrometry (HPLC/MS) under plasmaspray conditions. By this approach many different compounds have been detected, and for most of them, possible structures have been proposed on the basis of literature data and molecular weight assignments.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290051212
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  • 5
    Electronic Resource
    Electronic Resource
    A raman LAM study of lamellar thickness of virgin polyethylene powder (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 29 (1991), S. 1189-1192 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The lamellar thickness of polyethylene virgin reactor powder has been successfully measured using the Raman longitudinal acoustic mode (LAM). Relatively high lamellar thicknesses have been found. These values change with polymerization temperature in an unusual way, with lamellar thickness being larger for lower polymerization temperature, i.e., at higher undercooling for crystallization. Agreement within an experimental error of 10% has been obtained between values from LAM and those calculated by the Thompson - Gibbs equation from the melting point measured by differential scanning calorimetry.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1991.090291003
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  • 6
    Electronic Resource
    Electronic Resource
    A calorimetric investigation on high molecular weight polyethylene reactor powders (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 29 (1991), S. 1179-1188 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Reactor powders of high- and ultrahigh-molecular weight polyethylene have been investigated. Two different Ziegler-Natta synthesis processes were used: polymerization in a slurry and in the gas phase. Synthesis temperature range was 30-85°C. Monoclinic crystals were identified in samples synthesized at 30°C. Investigations of thermal parameters were carried out by differential scanning calorimetry. A range of heating rates (0.4-10.0°C/min) was used to obtain information on sample reorganization on heating. The corresponding melt-crystallized samples were scanned and their thermal parameters were compared with those obtained from the original nascent powders. Percent crystallinity and average lamellar thickness, computed by the Thompson-Gibbs equation, were found to be controlled by conditions of synthesis. For reactor powders, the fraction of crystallinity is found to be insensitive to synthesis temperature. Crystallinity is controlled mainly by the synthesis process type: slurry or gas phase. Lamellar thickness was found to decrease as synthesis temperature was increased. This trend is the opposite of what is obtained on melt crystallization and can be interpreted on the basis of Lauritzen and Hoffman's theory of crystal growth. Nascent reactor powders give experimental support for the dependence of lamellar thickness on crystallization temperature that follows the pattern described in the theory at high undercooling. The influence of molecular weight on crystallinity and lamellar thickness of both nascent powders and melt-crystallized samples was also studied. Catalyst and synthesis conditions were found to control crystallinity and crystallite dimensions of the reactor powders. Thus, polyethylenes suitable for a specific purpose can be obtained directly on synthesis.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1991.090291002
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  • 7
    Electronic Resource
    Electronic Resource
    Combined processing of polypropylene film by coextrusion and zone-annealing (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 43 (1991), S. 429-435 
    Details
    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: In order to improve the mechanical properties of polypropylene film, a new processing combining extrusion and zone-annealing has been applied. It was found that there are suitable conditions for each step in the combined processing. When the coextrusion draw ratio was low, the total draw ratio and modulus could be increased by the zone-annealing subsequently done. The highest modulus was obtained when the film was coextruded at extrusion draw ratio 4 and then zone-annealed at 120°C under 7 kg/mm2. The value was 12 GPa in Young's modulus or 17 GPa in dynamic modulus. The peak temperature of αc dynamic dispersion for the combinedly processed film was 109°C, which is higher by 10°C than that for the as-coextruded film. Four drawing methods were compared in dynamic viscoelasticity. These methods are the coextrusion, zone-drawing/zone-annealing, two-step coextrusion, and the combined processing by coextrusion and zone-annealing. The highest dynamic modulus for each method was arranged in the above order. The combined processing indicated the most effective improvement in mechanical properties, because it is believed that lamellae in the original film were broken by cooperating interaction of shear stress, compression, and tension on coextrusion and then the superstructure with a high crystallinity and a high molecular orientation was formed on zone-annealing.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070430303
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  • 8
    Electronic Resource
    Electronic Resource
    Rolling and roll-drawing of ultrahigh molecular weight polyethylene reactor powders (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 43 (1991), S. 1559-1564 
    Details
    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: Ultrahigh molecular weight polyethylene (UHMWPE) reactor powders have been found to be processable in the solid state by the techniques of rolling and roll-drawing. Plates of compacted UHMWPE reactor powder were prepared below their melting points. These plates were then rolled at 124°C. The maximum uniaxial draw ratio (DR) obtained by multiple rolling was about 10. In additional experiments, rolled plates of a DR of 6 were further drawn by tensile stretching at a temperature of 135°C. The specimens prepared by rolling and by the two-stage draw were characterized by tensile measurements, differential scanning calorimetry (DSC), and X-ray diffraction. Results show that, on rolling alone, the tensile modulus and tensile strength achieved were 3 GPa and 42 MPa, respectively, at a DR of 9.6. The rolled plates were effectively drawn further to a total DR of 86. Such highly drawn films exhibited tensile moduli and tensile strength up to 81 and 1.3 GPa, respectively. A high crystallinity and high crystal orientation were also obtained by the two-stage draw.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070430819
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  • 9
    Electronic Resource
    Electronic Resource
    Elimination of carbon monoxide by electron impact on quinoline N-oxide, carbostyril and 8-hydroxyquinolineDedicated to Professor J. D. Morrison on the occasion of his retirement from the Chair of Physical Chemistry, La Trobe University, Bundoora, Victoria, Australia. (1991)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 26 (1991), S. 247-249 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Under electron impact, the molecular ions of quinoline N-oxide, carbostyril and 8-hydroxyquinoline lose carbon monoxide giving a fragment ion C8H7N (m/z 117), which was shown by collision-activated dissociation in each case to have the structure of the molecular ion of indole. Its formation from 8-hydroxyquinoline requires an unusual rearrangement. Isoquinoline N-oxide loses HCN rather than CO and gives a fragment which has the structure of the molecular ion of benzofuran. When the first three compounds were subjected to flash vacuum pyrolysis, quinoline N-oxide at 500-700°C gave carbostyril and indole was detected by gas chromatography/mass Spectrometry. At 900°C carbostyril and 8-hydroxyquinoline both gave indole in small amounts, detected by gas chromatography/mass Spectrometry.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210260412
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  • 10
    Electronic Resource
    Electronic Resource
    Intracellular expression of Kluyveromyces lactis toxin γ subunit mimics treatment with exogenous toxin and distinguishes two classes of toxin-resistant mutant (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 7 (1991), S. 617-625 
    Details
    ISSN: 0749-503X
    Keywords: Cell cycle ; toxin ; K. lactis ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The Kluyveromyces lactis toxin is a heterotrimeric protein which irreversible arrests proliferation of sensitive Saccharomyces cerevisiae cells in the G1 phase of the cell cycle. By expressing the γ subunit of the toxin in sensitive yeast cells from a conditional promoter, it was previously demonstrated that it alone is required for inhibition (Tokunaga et al. (1989). Nucleic Acids Res. 17, 3435-3446). Here we show that, like native exogenous toxin, intracellular γ subunit expression promoters a striking arrest of sensitive cells in G1. However, unlike the G1 arrest caused by native toxin, that induced by the γ subunit alone does not result in reduced cellular viability and is fully and rapidly reversible, suggesting that the G1 arrest and the irreversibility of action may reflect different aspects of the toxin's interaction with sensitive cells. We have selected a large number of S. cerevisiae mutants which are highly resistant to the toxin in order to study its mode of action in more detail. Complementation analysis demonstrated that all but one of the mutants were recessive and these defined four separate genes. Members of two complementation groups concurrently acquired resistance to intracellular γ subunit expression, suggesting that they contain a modified toxin target site. The other two genes appear to be required for entry of the γ subunit into the sensitive cell since these mutants, while refractory to exogenous toxin, were fully sensitive to intracellular γ subunit expression.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/yea.320070610
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