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  • Biochemistry and Biotechnology  (2)
  • Polymer and Materials Science  (1)
  • 1
    ISSN: 0006-3592
    Keywords: α-chymotrypsin ; covalent modification ; enzyme-polyelectrolyte complexes ; enzymatic activity ; denaturation ; water-cosolvent mixtures ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Formation of noncovalent complexes between α-chymotrypsin (CT) and a polyelectrolyte, polybrene (PB), has been shown to produce two major effects on enzymatic reactions in binary mixtures of polar organic cosolvents with water. (i) At moderate concentrations of organic cosolvents (10% to 30% v/v), enzymatic activity of CT is higher than in aqueous solutions, and this activation effect is more significant for CT in complex with PB (5- to 7-fold) than for free enzyme (1.5- to 2.5-fold). (ii) The range of cosolvent concentrations that the enzyme tolerates without complete loss of catalytic activity is much broader. For enhancement of enzyme stability in the complex with the polycation, the number of negatively charged groups in the protein has been artificially increased by using chemical modification with pyromellitic and succinic anhydrides. Additional activation effect at moderate concentrations of ethanol and enhanced resistance of the enzyme toward inactivation at high concentrations of the organic solvent have been observed for the modified preparations of CT in the complex with PB as compared with an analogous complex of the native enzyme. Structural changes behind alterations in enzyme activity in water-ethanol mixtures have been studied by the method of circular dichroism (CD). Protein conformation of all CT preparations has not changed significantly up to 30% v/v of ethanol where activation effects in enzymatic catalysis were most pronounced. At higher concentrations of ethanol, structural changes in the protein have been observed for different forms of CT that were well correlated with a decrease in enzymatic activity. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 267-277, 1997.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 552-556 
    ISSN: 0006-3592
    Keywords: baroenzymology ; reversed micelles ; α-chymotrypsin ; catalytic activity and stability ; effect of pressure, temperature, and glycerol ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Thermostability of α-chymotrypsin at normal pressure in reversed micelles depends on both an effective surfactant solvation degree and glycerol content in the system. The difference in α-chymotrypsin stability in reversed micelles at various glycerol concentrations [up to 60% (v/v)] was more pronounced at high surfactant degrees of solvation, R ≥ 16. After a 1-h incubation at 40°C in “aqueous” reversed micelles (in the absence of glycerol), α-chymotrypsin retained only 1% of initial catalytic activity and 10, 22, 59, and 48% residual activity in glycerol-solvated micelles with 20, 30, 50, and 60% (v/v) glycerol, respectively. The explanation of the observed effects is given in the frames of micellar matrix structural order increasing in the presence of glycerol as a water-miscible cosolvent that leads to the decreasing mobility of the α-chymotrypsin molecule and, thus the increase of its stability. It was found that glycerol or hydrostatic pressure could be used to stabilize α-chymotrypsin in reversed micelles; a lower pressure is necessary to reach a given level of enzyme stability in the presence of glycerol. ©1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 552-556, 1998.
    Additional Material: 4 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 2801-2814 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Being solubilized in systems of reversed micelles of a surfactant, the macromolecules incorporate into the inner cavities of the micelles, whose size can be changed by varying the degree of hydration, w0 = [H2O]/[surfactant]. The conjugates of proteins (α-chymotrypsin, bovine serum albumin (BSA), monoclonal antibodies to insulin) with linear polyelectrolytes (poly(methacrylic acid), quaternized poly(4-vinylpyridine)) are synthesized in reversed micelles of Aerosol OT (sodium bis(2-ethylhexyl)sulfosuccinate) in the octane with 100% yield. The yield critically depends on the degree of hydration: the reaction does not proceed at low w0, but if w0 exceeds a threshold value (which differs for various macromolecules) the yield increases sharply and reaches 100%. Using the ultracentrifugation it was demonstrated that at low w0 the polyelectrolyte represents a compact globule compressed by the micellar matrix in the inner cavity of a micelle. Under these conditions, there is no space for the protein in a micelle which contains polyelectrolyte, and therefore reaction does not proceed. If w0 exceeds a threshold value the micelles become large enough to entrap the conjugated macromolecules simultaneously. The possibility of regulation of the conjugate composition by variation of w0 (via the size of the micellar matrix) was demonstrated by a conjugate of BSA with quaternized poly(4-vinylpyridine).
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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