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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Catalysis letters 35 (1995), S. 395-405 
    ISSN: 1572-879X
    Keywords: glucose oxidase ; catalytic activity ; protein unfolding ; water-miscible solvents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An experimental investigation was carried out on the kinetic and stability behaviour ofAspergillus niger glucose oxidase in water-polyol mixtures. Kinetic runs performed in systems containing up to 8 M polyhydric cosolvents (ethylene glycol, propylene glycol and glycerol) showed a strong dependence of the catalytic properties of the enzyme on the nature and composition of the reaction medium. Higher residual activities were measured in the presence of additives of lower polarity, according to the following order: propylene glycol 〉 ethylene glycol 〉 glycerol. Dilution and thermal unfolding experiments provided evidence that the activity reductions were not ascribable to solvent-induced structural modifications of the enzyme molecule but, rather, to the inhibitory action exerted by the polyols.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Biotechnology techniques 12 (1998), S. 855-858 
    ISSN: 1573-6784
    Keywords: Immunoglobulins ; sorbitol ; protein denaturation ; stabilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Sorbitol at 30% (w/w) stabilized human IgG to thermal denaturation from 60 to 85°C, increasing the protein's half life from 25 to 266 min at 70°C. A kinetic model based on the Lumry-Eyring inactivation scheme was developed and used to estimate the apparent rate constant and activation energy. © Rapid Science. 1998
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 525-534 
    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 molecular thermodynamic model studied is based on the two-state mechanism of inactivation, in which only native folded and polymorphous unfolded protein forms are present at equilibrium. The influence of solvent on protein stability is described in terms of perturbation of the protein distribution between the two conformational states. An expression derived for the chemical potential of the protein accounts for conformational changes, ideal mixing effects, and interaction of the protein with the surrounding medium.Thermal unfolding of lysozyme was then studied in the absence or presence of hydroxylic compounds. Ultraviolet difference spectroscopy was used to monitor the conformational changes induced by heating and to determine the melting temperature of the protein. The additives investigated are ethanol, glycols, and natural osmolytes. Media containing ethanol and glycols destabilized lysozyme, whereas sugars increased the conformational stability of the protein. For all of the systems examined the melting temperature was linearly related to the surface tension of the mixed solvent, supporting the ability of the model to describe the influence of the solvent and composition on lysozyme unfolding. Model predictions agreed fairly well with published differential scanning calorimetric data. The influence of hydroxylic additives on protein's conformational stability does not extend to any special property of these components, but to their ability to perturb the surface tension of water. This model can be used to interpret and correlate thermal unfolding data and to solve the problem of protein stabilization.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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