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  • 1
    Electronic Resource
    Electronic Resource
    Protein-protein and protein-salt interactions in aqueous protein solutions containing concentrated electrolytes (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 11-21 
    Details
    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.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Experimental measurements and monte-carlo simulation of water diffusion into epoxy matrices (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 29 (1984), S. 2453-2466 
    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: Sorption and desorption data are reported for water in epoxy at 25°C and 70°C. A Monte Carlo model based on the dual-sorption theory is formulated to explain observed diffusion behavior. Random walk of particles is followed through a regular lattice with randomly distributed adsorption sites. Comparison of predicted results with experiment shows that the model predicts sorption data well. A modification to the model is proposed to improve prediction of desorption data.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1984.070290803
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  • 3
    Electronic Resource
    Electronic Resource
    Protein salting-out: Phase equilibria in two-protein systems (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 53 (1997), S. 567-574 
    Details
    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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  • 4
    Electronic Resource
    Electronic Resource
    Representation of vapor-liquid and liquid-liquid equilibria for binary systems containing polymers: Applicability of an extended flory-huggins equation (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 47 (1993), S. 1193-1206 
    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: For some binary systems, an extended Flory-Huggins equation is applicable to both vaporliquid equilibria (VLE) and liquid-liquid equilibria (LLE) using the same adjustable parameters. New LLE and VLE data are reported for polystyrene (PS) (MW = 100,000)/cyclohexane and for poly(ethylene glycol) (PEG) (MW = 8,000)/water. Experimental results for the PS/cyclohexane system agree well with the semiempirical model, whereas those for PEG/water do not, probably because, for PEG/water, the temperature range of the VLE data is about 55°C lower than that of the LLE data. Excellent fits were obtained for our previously published experimental results for PS/cyclohexane (upper critical solution temperature, UCST), PS/ethyl acetate (lower critical solution temperature, LCST), PS/tert-butyl acetate and PS/methyl acetate (both UCST and LCST), and PEG/water (closed-loop). The semiempirical model also fits well with new data obtained for the polymer blend PS/poly(vinyl methyl ether). © 1993 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070470707
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  • 5
    Electronic Resource
    Electronic Resource
    Thermodynamics of phase equilibria in aqueous-organic systems with salt (1994)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 40 (1994), S. 676-691 
    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: A semiempirical thermodynamic method is developed to establish a framework for calculating vapor-liquid and liquid-liquid equilibria in ternary systems containing water, an organic solvent, and a salt. Careful attention is given to precise definition of standard states. Short-range ion-solvent forces are taken into account primarily by a chemical-equilibrium method based on stepwise ion solvation; however, physical contributions also contribute. Water-cosolvent nonideality is described by an extended equation of the van Laar form. Long-range electrostatic forces between ions are taken into account by an extended Debye-Hückel equation with corrections for transferring from a McMillan-Mayer to a Lewis-Randall framework.The new method is illustrated with results for several systems including saturated aqueous mixtures of LiBr or LiCl with methanol where the salt concentration exceeds 20 molal. The method developed here is of particular interest for process calculations in extractive crystallization, a low-energy operation for producing salt from aqueous solution.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690400411
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  • 6
    Electronic Resource
    Electronic Resource
    Electrostatic potentials and protein partitioning in aqueous two-phase systems (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 1401-1409 
    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: A thermodynamic analysis unambiguously relates interfacial-electrostatic-potential differences measured with Ag/AgCl capillary electrodes to the equilibrium properties of an aqueous two-phase system. Interfacial electrostatic potentials were measured as a function of total α-cyclodextrin concentration in an aqueous two-phase system containing 9.1 wt. % poly (ethylene glycol), 6.1 wt. % Dextran T-70, and 1-mM potassium iodide. An order-of-magnitude increase in the interfacial electrostatic potential was observed as the total concentration of α-cyclodextrin increased from 0 to 1 mM. Measured partition coefficients for α-chymotrypsin, lysozyme, and bovine serum albumin depend strongly on α-cyclodextrin concentration. For example, as the concentration of α-cyclodextrin rises from 0 to 1 mM, the partition coefficient of lysozyme decreases from 1.7 to 0.55. These measurements are in good agreement with theoretical expectations.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690370912
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular thermodynamics for salt-induce protein precipitation (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2150-2159 
    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: A molecular-thermodynamic model is developed for salt-induced protein precipitation, which considers an aqueous solution of globular protein molecules as a pseudo-one-component system containing macroions that interact through Coulombic repulsion, dispersion attraction and hydrophobic interactions, and forces arising from ion-excluded volume. Forces from ion-excluded volume take into account formation of ion pairs and ionic clusters at high salt concentrations; they are calculated in the context of the Percus-Yevick integral-equation theory. Hydrophobic interactions between exposed nonpolar amino-acid residues on the surfaces of the protein molecules are modeled as short-range, attractive interactions between “spherical caps” on the surfaces of the protein polyions. An equation of state is derived using perturbation theory. From this equation of state we calculate liquid - liquid equilibria: equilibrium between an aqueous phase dilute in protein and another aqueous phase rich in protein, which represents “precipitated” protein. In the equation of state, center-to-center, spherically symmetric macroion-macroion interactions are described by the random-phase approximation, while the orientation-dependent short-range hydrophobic interaction is incorporated through the perturbation theory of associating fluids. The results suggest that either ion-excluded-volume or hydrophobic-bonding effects can precipitate proteins in aqueous solutions with high salt concentrations.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410914
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  • 8
    Electronic Resource
    Electronic Resource
    Application of integral-equation theory to aqueous two-phase partitioning systems (1993)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 39 (1993), S. 1539-1557 
    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: A molecular-thermodynamic model is developed for representing thermodynamic properties of aqueous two-phase systems containing polymers, electrolytes, and proteins. The model is based on McMillan-Mayer solution theory and the generalized mean-spherical approximation to account for electrostatic forces between unlike ions. The Boublik-Mansoori equation of state for hard-sphere mixtures is coupled with the osmotic virial expansion truncated after the second-virial terms to account for short-range forces between molecules.Osmotic second virial coefficients are reported from low-angle laser-light scattering (LALLS) data for binary and ternary aqueous solutions containing polymers and proteins. Ion-polymer specific-interaction coefficients are determined from osmoticpressure data for aqueous solutions containing a water-soluble polymer and an alkali chloride, phosphate or sulfate salt.When coupled with LALLS and osmotic-pressure data reported here, the model is used to predict liquid-liquid equilibria, protein partition coefficients, and electrostatic potentials between phases for both polymer-polymer and polymer-salt aqueous two-phase systems. For bovine serum albumin, lysozyme, and α-chymotrypsin, predicted partition coefficients are in excellent agreement with experiment.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690390913
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  • 9
    Electronic Resource
    Electronic Resource
    Salting out of aqueous proteins: Phase equilibria and intermolecular potentials (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 996-1004 
    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: Salting-out phase equilibria are reported for lysozyme and α-chymotrypsin from concentrated ammonium-sulfate solutions. Supernatant and dense-phase protein concentrations and the resulting protein partition coefficients are given as a function of solution pH and ionic strength. Phase equilibria with a trivalent salt (sodium citrate) confirm that ionic strength, rather than salt concentration, is the appropriate variable describing phase equilibria. The salting-out behavior of a mixture of an aqueous lysozyme and α-chymotrypsin is independent of the presence of the other protein.Parameters for a molecular-thermodynamic description of salting-out behavior are obtained from low-angle laser-light scattering (LALLS). Osmotic second virial coefficients from LALLS are reported over a range of pH for dilute chymotrypsin concentrations in aqueous electrolyte solutions at 0.01 and 1.0 M ionic strengths. Effective Hamaker constants, regressed from experimental osmotic second virial coefficients, are determined for models of the protein - protein potential of mean force. In addition to excluded volume, dispersion, and shielded charge - charge potentials, the description of protein - protein interactions includes attractive charge - dipole and dipole - dipole potentials as well as an osmotic-attraction potential that becomes important at high salt concentrations. Protein dipole - dipole potentials are required to account for the observed pH dependence of osmotic second virial coefficients, especially at low ionic strength.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410430
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  • 10
    Electronic Resource
    Electronic Resource
    Letters to the editor (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1372-1374 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430529
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