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  • 1
    ISSN: 0006-3592
    Keywords: reverse micelle ; solubilization ; light scattering ; chymotrypsin ; LADH ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Solubilization properties of α-chymotrypsin and alcohol dehydrogenase (LADH) in reverse micelles are reported for three different solubilization techniques. The solubilization properties for these two proteins depend on the method used for protein addition. The addition of a dry protein powder to a reverse-micelle-containing organic phase does not appreciably solubilize the protein until the diameter of the reverse micelle is similar to that of the protein. However, when an aqueous protein solution is injected an organic phase, protein solubilization is not strongly dependent on micelle size. For chymotrypsin, multiple protein occupancy occurs at large micelle size, with as many as 11 chymotrypsin molecules solubilized in one reverse micelle. The solubilization of chymotrypsin using a phase-transter technique with a positively charged surfactant follows the expected traned based on protein-surfactant electrostatic interactions. When a negatively charged sufactants is used for phase transfer, at low pH the solubilization data do not fit this electrostatic interaction mechanism. In this case, proteinsurfactant aggregation may be occurring at the aqueousorganic interface.
    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 53 (1997), S. 567-574 
    ISSN: 0006-3592
    Keywords: salting out ; precipitation ; protein separation ; protein association ; lysozyme ; α-chymotrypsin ; ovalbumin ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The phase behavior of two aqueous binary protein mixtures, lysozyme-chymotrypsin and lysozyme-ovalbumin, was determined in ammonium sulfate solutions. Protein concentrations were determined in both phases as a function of pH and ionic strength. For lysozyme-chymotrypsin mixtures, the observed phase behavior was similar to that for each individual protein; the presence of the second protein had little influence. The phase behavior of lysozyme-ovalbumin mixtures, however, was different from that of the respective single-protein systems. Lysozyme and ovalbumin are found together in egg whites; their association is both pH and ionic-strength dependent. The association of proteins is a key determinant of protein solubility in salt solutions. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 53: 567-574, 1997.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 1155-1164 
    ISSN: 0006-3592
    Keywords: protein solubility ; precipitation ; salting-out ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The solubilities of lysozyme, α-chymotrypsin and bovine serum albumin (BSA) were studied in aqueous electrolyte solution as a function of ionic strength, pH, the chemical nature of salt, and initial protein concentration. Compositions were measured for both the supernatant phase and the precipitate phase at 25°C. Salts studied were sodium chloride, sodium sulfate, and sodium phosphate. For lysozyme, protein concentrations in supernatant and precipitate phases are independent of the initial protein concentration; solubility can be represented by the Cohn salting-out equation. Lysozyme has a minimum solubility around pH 10, close to its isoelectric point (pH 10.5). The effectiveness of the three salts studied for precipitation were in the sequence sulfate 〉 phosphate 〉 chloride, consistent with the Hofmeister series. However, for α-chymotrypsin and BSA, initial protein concentration affects the apparent equillibrium solubility. For these proteins, experimental results show that the compositions of the precipitate phase are also affected by the initial protein concentration. We define a distribution coefficient κe to represent the equilibrium ratio of the protein concentration in the supernatant phase to that in the precipitate phase. When the salt concentration is constant, the results show that, for lysozyme, the protein concentrations in both phases are independent of the initial protein concentrations, and thus κe is a constant. For α-chymotrypsin and BSA, their concentrations in both phases are nearly proportional to the initial protein concentrations, and therefore, for each protein, at constant salt concentration, the distribution coefficient κe is independent of the initial protein concentration. However, for both lysozyme and α-chymotrypsin, the distribution coefficient falls with increasing salt concentration. These results indicate that care must be used in the definition of solubility. Solubility is appropriate when the precipitate phase is pure, but when it is not, the distribution coefficient better describes the phase behavior. © 1992 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
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  • 4
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: No abstract.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0006-3592
    Keywords: proteins ; salts ; intermolecular interactions ; potentials of mean force ; precipitation ; crystallization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Protein-protein and protein-salt interactions have been obtained for ovalbumin in solutions of ammonium sulfate and for lysozyme in solutions of ammonium sulfate, sodium chloride, potassium isothiocyanate, and potassium chloride. The two-body interactions between ovalbumin molecules in concentrated ammonium-sulfate solutions can be described by the DLVO potentials plus a potential that accounts for the decrease in free volume available to the protein due to the presence of the salt ions. The interaction between ovalbumin and ammonium sulfate is unfavorable, reflecting the kosmotropic nature of sulfate anions. Lysozyme-lysozyme interactions cannot be described by the above potentials because anion binding to lysozyme alters these interactions. Lysozyme-isothiocyanate complexes are strongly attractive due to electrostatic interactions resulting from bridging by the isothiocyanate ion. Lysozyme-lysozyme interactions in sulfate solutions are more repulsive than expected, possibly resulting from a larger excluded volume of a lysozyme-sulfate bound complex or perhaps, hydration forces between the lysozyme-sulfate complexes. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 11-21, 1998.
    Additional Material: 11 Ill.
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  • 6
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; DNA restriction fragments ; Hydroxyethylcellulose ; Polyvinylpyrrolidone ; Star polyethylene oxide ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The mechanism of DNA separation by dilute polymer solutions in capillary electrophoresis is not well understood. To provide information on the effect of polymer properties on DNA separations, four polymers that differ in size, shape and stiffness were examined. Hydroxyethylcellulose of high molecular weight provides excellent separation of large DNA fragments (2027 bp - 23 130 bp). Polyvinylpyrrolidone separates DNA from 72 bp to 23 kbp; star-(polyethylene oxide) and linear poly(ethylene oxide) provide separation of fragments to 1353 bp.
    Additional Material: 5 Ill.
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  • 7
    ISSN: 0173-0835
    Keywords: DNA electrophoresis ; Cyclic migration ; Hernias ; Polyacrylamide ; Agarose ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Toward improving DNA separations, this work reports the effects of high-frequency square-wave AC fields superimposed perpendicular to the direct current (DC) separation field on DNA migration in both polyacrylamide-based interpenetrating networks (IPNs) and in agarose networks. Compared to standard polyacrylamide gels, IPNs allow the separation of larger DNA (9000 bp vs. 5000 bp at 5 V/cm). In novel polyacrylamide-based IPNs, an alternating current (AC) field of 5 Hz increased the maximum DNA size separable. This effect was extended to larger DNA sizes with increasing electric-field strength up to and apparently beyond the power supply-limited maximum electric-field strength of 48 V/cm. The orthogonal AC field also increased mobility. These two results combine to yield a reduction in separation time of up to a factor of 20 in novel polyacrylamide-based IPNs. When negatively charged acrylic-acid groups were incorporated into the IPNs, the use of the AC field changed the DNA-network interaction, which altered the size dependence of DNA mobility. In agarose gels, an AC field of 50 Hz increased the size range separable; however, there was no increase in DNA mobility. There was no change in size dependence of mobility in an AC field when the number of charged groups in the agarose network was increased. Based on results in the literature, possible mechanisms were examined for the effects of the AC field on DNA separation.
    Additional Material: 9 Ill.
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  • 8
    ISSN: 0006-3592
    Keywords: bioconversions ; hydrolysis ; casein proteins ; catalysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Partition coefficients in poly(ethylene glycol)/dextran aqueous two-phase systems are reported for mixed-casein and its components, α, β and κ casein. Rates of casein proteolysis by α-chymotrypsin and by trypsin are reported in single-phase and aqueous two-phase reactor systems. The advantages resulting from selective partitioning of substrates, enzymes, and products are examined in terms of relative volumetric reaction rates.
    Additional Material: 12 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 156-161 
    ISSN: 0006-3592
    Keywords: LADH ; surfactants ; ERP ; CD ; fluorescence ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Alcohol dehydrogenase (LADH) was studied in aqueous solutions of surfactants to determine its structural and catalytic characteristics. Fluorescence, circular dichroism (CD), and electron paramagnetic resonance (ERP) techniques were used to study structural changes to the enzyme. The activity of LADH in catalyzing the oxidation of ethanol was investigated. Short-chain alkyl sulfonates and sulfates did not deactivate LADH or alter its structure. Longer and branched alkyl sulfates and sulfonates, as well as a cationic surfactant (CTAB), affected both LADH activity and conformation. © 1993 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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