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  • 1
    Electronic Resource
    Electronic Resource
    Kinetics of enzymatic lysis and disruption of yeast cells: II. A simple model of lysis kinetics (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 30 (1987), S. 481-490 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A simple two-step model is proposed to describe the kinetics of the two lytic systems examined in the preceding article. The model predicts concentrations of yeast solids, soluble proteins, peptides, and carbohyrates. In the first reaction step, yeast cell mass is solubilized; in the second, the released protein can be hydrolyzed to peptides. Kinetics for both yeast lysis and the subsequent protein breakdown are based on Michaelis-Menten expressions. Terms have been included for competitive inhibition of yeast lysis by substances in the Cytophaga enzyme preparation, and for incomplete hydrolysis of cells by the Oerskovia enzyme system. Parameters have been independently determined for all reactions except Oerskovia proteolysis, where they were fit by a leastsquares method to data from model test runs. The model has been verified for yeast concentrations between 0.7 and 70 g/L yeast (dry basis) and 4-40% crude enzyme solution.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260300404
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  • 2
    Electronic Resource
    Electronic Resource
    Kinetics of enzymatic lysis and disruption of yeast cells: I. Evaluation of two lytic systems with different properties (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 30 (1987), S. 471-480 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Many microorganisms produce enzymes which lyse the walls of yeasts, fungi, and bacteria. The proportions of different enzyme activities present in the lytic system, their action patterns, synergism, and dependence on inhibitors, constitute the activity profile of the lytic system. Taken together, the activity profile and process conditions for lysis determine the reaction rate and the distribution of products from lysis of any given type of cells. Kinetics of glucan hydrolysis, proteolysis, and lysis of brewer's yeast were compared for two extracellular yeast-lytic enzyme systems with different properties. The enzyme sources used were filtered culture broths from Cytophaga sp. NCIB 9497 grown in batch culture and from Oerskovia xanthineolytica LL-G109, grown under carbon limitation in continuous culture. Rate and extent of cell hydrolysis, and the accumulation of soluble proteins, peptides, and carbohydrates from the lysed yeast cells, are discussed in terms of the activity profiles and potential applications of the two enzyme systems.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260300403
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  • 3
    Electronic Resource
    Electronic Resource
    Vitrification of mouse oocytes using short cryoprotectant exposure: Effects of varying exposure times on survival (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 33 (1992), S. 210-214 
    Details
    ISSN: 1040-452X
    Keywords: Oocytes cryopreservation ; Vitrification ; Mouse ; Minimal cryoprotectant exposure ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The effects on oocyte viability of varying the duration of exposure to cryoprotectants before rapid cooling to - 196°C were examined, using the vitrification protocol of Nakagata. A very short exposure (15 sec) was found to be optimal, resulting in an overall rate of development from vitrified oocytes to hatching blastocysts of 31.8%. Very high rates of survival (77-89%) of oocytes exposed to the cryoprotectant media, but without the vitrification, together with extreme variability in results between straws in the vitrified groups, suggest that losses in viability during vitrification may result from ice damage during devitrification of the medium. (c) 1992 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080330214
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  • 4
    Electronic Resource
    Electronic Resource
    Morphology of polyethylene crystallized by solution stirring (1971)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 9 (1971), S. 531-541 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dilatometric and calorimetric studies have been made of the fusion process of linear polyethylene crystallized by stirring xylene solutions at elevated temperatures. It is shown that the melting point of the crystals increases rapidly from 139.5°C to 145°C in the crystallization temperature range of 100-103°C and levels off to 146 ± 0.5°C, provided that very slow heating rates are employed. Stirrer-crystallized samples treated with fuming nitric acid show higher crystalline contents. Comparison of their enthalpies of fusion and melting points indicate that higher molecular order along the fiber axis is associated with higher crystallization temperatures. This is in general agreement with corresponding results of other modes of crystallization. The attack of fuming nitric acid on stirrer crystals is characterized by weight-loss curves similar to those of dilutesolution crystals and bulk polyethylene. The linear molecular weight dependence on time of exposure to nitric acid suggests that the oxidation proceeds mainly from the chain ends at a constant rate for samples stirred in the lower crystallization range, but an increased rate is observed for a sample stirred from xylene at 105°C. It is suggested that the lamellar overgrowths, most evident at low crystallization temperatures, are epitaxially attached to the fiber axis, whereas the smaller crossbandings observed at higher crystallization temperatures are possibly made up of elements of chains that are only partly incorporated in the highly ordered fibrous core.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1971.160090311
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  • 5
    Electronic Resource
    Electronic Resource
    Quaternary structure of elastin: Characterization of multichain peptide fragments obtained by elastase digestion (1985)
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1515-1526 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enzyme-purified elastin from bovine ligamentum nuchae was digested with elastase in the presence of sodium dodecyl sulfate. Chromatographic fractionation of the digest, after removal of the detergent, resulted in the high-yield isolation of two peptide fractions (F2 and F3) that differed in size and composition. The larger, F2, which accounted for about 55% of the starting material, was subjected to sedimentation-equilibrium analysis in three chaotropic solvents. Comparison of the distribution of point-average molecular weights (Mw and Mz) with protein concentration in the three systems lead to the conclusion that significant self-association of peptides occurred in the absence of 6M guanidinium hydrochloride. In this solvent, the molecular-weight distribution was between 25,000 and 34,000, a range of values in agreement with an intrinisic viscosity of 13.1 cc g-1 determined in the same solvent. Assessment of chain weight by N- and C-terminal analysis was consistent with F2 being a multichain molecule comprising four polypeptide chains linked by three polyfunctional amino acids. Results are interpreted in terms of an anisotropic ultrastructural model of the protein, in which four polypeptide chains constitute the primary filament visualized by electron microscopy in the intact fiber.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360240808
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  • 6
    Electronic Resource
    Electronic Resource
    Plasma membrane water permeabilities of human oocytes: The temperature dependence of water movement in individual cells (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 150 (1992), S. 175-179 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Membrane water permeability values were measured in individual fresh human pre-ovulatory oocytes using real time microscopy in a microscope diffusion chamber. The cells were exposed to anisosmotic conditions, their volume responses measured, and from these data the Lp values were computed employing the Kedem-Katchalsky analyses of irreversible thermodynamics. Lp values were measured at four temperatures for each oocyte between 37°C and 10°C, and the temperature-related Arrhenius activation energy (Ea) calculated. It was apparent that individual oocytes exhibited a wide range of Lp values; at 37°C Lp values ranged between 0.33 and 1.80 μm/atm/min. However, each oocyte exhibited the expected inverse linear correlation between Lp and temperature, with high linear correlations (R2 values between 0.73 and 0.96). A mean value for Ea of 8.61 ± 5.11 Kcal/mol was computed. It is apparent that pre-ovulatory human oocytes express a range of biological diversity in terms of membrane water transport, and this fact needs to be considered when attempting to formulate cryopreservation protocols for storage of these oocytes.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041500123
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  • 7
    Electronic Resource
    Electronic Resource
    A population balance model of enzymatic lysis of microbial cells (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 31-42 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A model is proposed for enzymatic lysis of microbial cells based on number balances over the distribution of cell-wall mass in a population of cells. Analytical solutions to the population balance equations were obtained by the method of characteristics for simple reaction kinetics. The model has been used to analyze the following cases of lysis in a nonhomogeneous cell population: wall hydrolysis with cell rupture and product release, the effect of a distribution of lysis rates, and lysis of two-layer cell walls. Rate expressions for the reactions of lysis can be derived from bulk-phase experiments; the distributions of cell size and product content can be measured independently by flow cytometric techniques. The population model also provides an explanation for the initial lag seen in lysis kinetics for virtually any initial distribution. The model demonstrates patterns of lysis and product recovery for heterogeneous populations of cells and also applies to the more general problem of soluble-enzyme reactions with heterogeneous solid substrates.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350106
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  • 8
    Electronic Resource
    Electronic Resource
    A structured mechanistic model of the kinetics of enzymatic lysis and disruption of yeast cells (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 31 (1988), S. 929-943 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A structured, mechanistic model has been built for the kinetics of yeast cell lysis by microbial cell lytic enzymes, based on an understanding of the two-layer yeast cell wall structure and the properties of yeast-lytic enzyme systems. The model predicts the release of protein, peptides and carbohydrates from four cell structures: the outer and inner wall layers, the cytosol and organelles or proteins present in particles; it also predicts organelle or particle lysis or solubilization and the breakdown of released proteins to peptides. Applications of the model to design and optimization of selective product release are discussed.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260310906
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