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  • Chemistry  (16)
  • chymotrypsin  (1)
  • 1990-1994  (16)
  • 1
    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 incompressible lattice-gas model by ten Brinke and Karasz is adopted to introduce the effect of specific interactions into a recently-presented Monte-Carlobased lattice expression for the Helmholtz energy of nonrandom mixing. While the lattice remains incompressible, intermolecular forces consist of two types: London dispersion forces and specific (chemical) forces. The specific interactions between similar components, as well as those between dissimilar components, are incorporated in a systematic manner. Closed-loop temperature-composition phase diagrams are obtained. The theory is compared with experimental data for several binary systems, including polymer solutions, which exhibit closed-loop coexistence curves. Theoretical and experimental results are in good agreement.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 2
    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
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  • 3
    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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  • 4
    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: Continuous thermodynamics is used to calculate liquid-liquid equilibria in a ternary system containing polydisperse polymer, one good solvent and one poor solvent (antisolvent). The polymer has a semiinfinite molecular-weight distribution which can be described by a gamma distribution. From Flory-Huggins theory, the logarithm of the distribution ratio of the polymer is a linear function of the molecular weight. Because the distribution of polymer between the two liquid phases is very sensitive to the choice of binary Flory parameters. The Flory parameters must be fitted to the ternary data. Results are given for the system benzene, ethanol, and polydisperse polystyrene.
    Additional Material: 2 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 1401-1409 
    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
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 39 (1993), S. 215-223 
    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 simple statistical-mechanical theory, known as the random-phase approximation, is applied to study liquid-liquid phase separations in solutions of globular proteins. Phase separation may be induced by addition of nonionic polymer or/and ordinary electrolytes. In this analysis, the osmotic-attraction mechanism, whereby the depletion of “solvent” particles between two proteins causes an attractive force, is primarily responsible for phase separation. For one-component models of protein solutions, the theory yields simple algebraic expressions for the equation of state and for the chemical potential of the protein. This analytical theory describes the observed solubility behavior of proteins, including the effect of protein and polymer size, protein charge and concentration, and concentration of simple electrolytes.
    Additional Material: 7 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 40 (1994), S. 676-691 
    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.
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  • 8
    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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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 102 (1990), S. 1286-1295 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Das Wissen über thermodynamische Eigenschaften ist für die Planung quantitativer Prozesse zur Herstellung chemischer Produkte wesentlich. Kalorische Größen, die für Wärmebilanzen benötigt werden, sind gewöhnlich bekannt oder leicht abzuschätzen. Wichtiger - und oft viel schwerer zu schätzen - sind die chemischen Potentiale von Komponenten in Mischungen. Sie bestimmen die Phasengleichgewichte, die für Trennungen wesentlich sind, und die chemischen Gleichgewichte, deren Kenntnis für die Entwicklung von chemischen Reaktoren und von Trennungen, die auf chemischen Reaktionen beruhen, notwendig ist. Die Molekulare Thermodynamik ist eine technisch ausgerichtete Wissenschaft zur Berechnung der gewünschten chemischen Potentiale aus einem Minimum an experimentellen Daten. Sie beruht auf der klassischen und der statistischen Thermodynamik und ermittelt chemische Potentiale mit Modellen, die auf der Molekülphysik und der Physikalischen Chemie basieren. Dieser Beitrag stellt einige ausgewählte Anwendungen der Molekularen Thermodynamik vor: die Bestimmung chemischer Potentiale in stark nicht idealen Mischungen, wie sie für die Planung von Destillationskolonnen und die Prozeßsicherheit erforderlich sind; die Ermittlung der Bedingungen, unter denen Kristalle einheitlicher Größe aus überkritischen Gasen gefällt werden können, aus Zustandsgleichungen; Molekülorbitalberechnungen als Wegweiser bei der Entwicklung von Alternativen zu umweltgefährdenden Chlorfluorkohlenwasserstoffen; Moleküldynamik-Simulationsrechnungen für die Trennung von Gasgemischen mit porösen Adsorbentien; die Berechnung von Gleichgewichten in zweiphasigen wäßrigen Systemen für die Trennung von Proteinmischungen; die Erweiterung zur Polymerlösungsthermodynamik als Wegweiser bei der Synthese von Hydrogelen, die für die Proteingewinnung aus Sojabohnen und zur kontrollierten Arzneimittelfreisetzung geeignet sind.
    Additional Material: 18 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0570-0833
    Keywords: Thermodynamics ; Thermodynamics ; Industrial chemistry ; Chemical process design ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermodynamic properties are essential for quantitative process design to produce chemical products. Caloric properties are required for heat balances, but these properties are usually available or estimated easily. More important - and often much more difficult to estimate - are the chemical potentials of components in mixtures; it is these potentials which determine phase equilibria, as required for separation operations, and chemical equilibria, as required for chemical reactors and for separation operations based on chemical reactions. Molecular thermodynamics is an engineering-oriented science for calculating the desired chemical potentials from a minimum of experimental data. This applied science, based on classical and statistical thermodynamics, yields chemical potentials through models that are based on molecular physics and physical chemistry. Selected examples are cited to illustrate the applicability of molecular thermodynamics: group-contribution methods for obtaining chemical potentials in highly nonideal mixtures as required for distillation-column and process-safety design; equation of state for precipitation of uniform-sized crystals from supercritical fluids; molecular-orbital calculations to guide process development for alternatives to environmentally dangerous chlorofluorohydrocarbons; molecular-simulation calculations for separation of gas mixtures with porous adsorbents; equilibria in two-phase aqueous systems for separation of protein mixtures; and, finally, extended polymer-solution thermodynamics to guide synthesis of hydrogels suitable for protein recovery from soybeans and for novel drug-delivery devices.
    Additional Material: 18 Ill.
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