An approach to the study of phase separation in ternary aqueous systems

Edmond, Elizabeth; Ogston, A. G.

doi:10.1042/bj1090569

Cited by 354 publications

(181 citation statements)

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“…Gel chromatographic evaluation of second virial coefficients for protein/dextran systems has led to elimination of the sphere/sphere model as a valid thermodynamic description of the space-filling effects in protein/polymer mixtures, since it does not predict the observed independence of covolume, expressed per unit mass of polymer, upon size of the polymer. This requirement is met by the sphere/ rod model [Edmond, E. & Ogston, A. G. (1968) Biochem. J.…”

mentioning

confidence: 99%

Thermodynamic nonideality in macromolecular solutions

Shearwin

Winzor

1990

European Journal of Biochemistry

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Second virial coefficients and hence covolumes for self-interaction of five proteins, viz. ribonuclease, ovalbumin, bovine serum albumin, catalase and a-crystallin, have been determined by analyzing the concentration dependence of the partition coefficient obtained from frontal chromatographic studies on either Fractogel TSK HW55 or porous glass beads. The resulting estimates of the effective radii essentially duplicate their Stokes counterparts and thereby provide further justification for assuming the approximate identity of the thermodynamic and hydrodynamic radii of hydrated globular proteins. Gel chromatographic evaluation of second virial coefficients for protein/dextran systems has led to elimination of the sphere/sphere model as a valid thermodynamic description of the space-filling effects in protein/polymer mixtures, since it does not predict the observed independence of covolume, expressed per unit mass of polymer, upon size of the polymer. This requirement is met by the sphere/ rod model [Edmond, E. & Ogston, A. G. (1968) Biochem. J. 109, 569-5761 and also by the sphere/flexiblesegment model [Hermans, J. (1982) J . Chenz. Phys. 77, 2193. Furthermore, similar studies of the effect of solute radius on covolume for interaction with dextran T70 attest to the adequacy of either model for predicting the thermodynamic nonideality arising from the inclusion of dextrans in protein solutions, and also provide the relevant calibration of the model.Studies of the effects of inert solutes on macromolecular interactions have led to the prediction and demonstration that self-association is enhanced by high concentrations of such solutes [l -61. In addition, advantage may be taken of the space-filling effects of inert solutes to detect enzyme isomerization [7], be it a substrate-induced [8-111 or a pre-existing [12 -141 phenomenon. Such thermodynamic nonideality of proteins/enzymes may be expressed quantitatively in terms of composition-dependent activity coefficients based on statistical-mechanical application of the excluded volume concept [15 -181. A quantity central to the prediction of thermodynamic nonideality is the covolume, i.e. the minimal volume in which two molecules can be located. In calculations of covolume, globular proteins have been regarded either as spheres or as ellipsoids of revolution [19, 201, whereas solutes such as poly(ethy1ene glycol) and dextran have been modelled as long rods [15] or as flexible segmented chains [17, 181. The major problem encountered in experimental studies of thermodynamic nonideality is thus not a lack of theoretical expressions for application but rather a lack of information on the magnitudes of parameters for substitution therein.In most studies of thermodynamic nonideality in protein solutions the stance has been taken that the Stokes radius of a globular protein should provide a reasonable estimate of its effective hydrated radius for use in covolume calculations [6 -12, 21, 221; however, this approximation is open to criticism on the grounds that a thermodynam...

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confidence: 99%

Thermodynamic nonideality in macromolecular solutions

Shearwin

Winzor

1990

European Journal of Biochemistry

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“…The osmotic virial expansion, first introduced by Edmond and Ogston [81], provided a simple theoretical framework for ATPSs. This methodology was adopted by King et al [82] and Haynes et al [76] to predict some protein partitioning in polymer-polymer mixtures in the presence or absence of salts.…”

Section: Modelingmentioning

confidence: 99%

Solubility of Amino Acids, Sugars, and Proteins

Macedo

2005

ChemInform

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Abstract:The importance of biomolecules is well recognized nowadays, owing to their application in many industrial processes, particularly in the food, pharmaceutical, and cosmetic industries.Amino acids, carbohydrates, and proteins are the three types of biomolecules considered in this review. Solubilities of several amino acids and sugars have been measured in water and, more recently, in mixed solvents, both with or without salts. Experimental data on partition of proteins in aqueous two-phase systems (ATPSs), with polymers or salts, have also been reported in the literature. The experimental techniques used are briefly discussed. Regarding modeling, the complexity of these solutions is very high. Sugars form strong hydrogen bonds with one another and with water or other solvents like alcohols. Liquid solutions with amino acids or proteins present not only short-range interaction forces, but also long-range forces, owing to the appearance of charged species. The capabilities of different molecular models and group-contribution-based methods are shown.

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“…Most of the research conducted with aqueous two-phase systems has been experimental and empirical; few studies of the fundamental thermodynamic mechanisms of phase separation and partitioning have been conducted (5,23,24). Furthermore, the systems which have been described use highly purified, expensive polymers, for model laboratoryscale applications.…”

Section: Modeling and Applications Of Downstream Processingmentioning

confidence: 99%

Modeling and Applications of Downstream Processing

Hamel

Hunter

1990

ACS Symposium Series

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Downstream processing is playing an increasingly important role in the biochemical industry, especially since the advent of recombinant DNA technology. The use of recombinant DNA technology not only enables improvements in the production efficiency of therapeutic and industrial proteins, but it also permits the modification and improvement of protein structure and thus function.However, the commercial application of such technology was initially accompanied by concerns over product safety.Quality criteria have been made especially stringent for products derived from genetically-modified microorganisms. The establishment of strict quality guidelines was the result of early concern about the oncogenic potential related to products contaminated by DNA sequences of the host mammalian cells (1). The quest for high quality has created a growing need for high-resolution techniques at the process scale as well as for novel strategies for the isolation and purification of bioproducts. Since the typical environment for producing biologicals is a complex one and quality criteria need to be strict, primary recovery techniques are typically implemented in a purification scheme prior to (or in conjunction with) high-resolution techniques. The most sophisticated and useful schemes take advantage of both the different physical and chemical properties of the components in complex mixtures and of the interactive nature of the downstream processing techniques (see Figure 1).

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An approach to the study of phase separation in ternary aqueous systems

Cited by 354 publications

References 19 publications

Thermodynamic nonideality in macromolecular solutions

Thermodynamic nonideality in macromolecular solutions

Solubility of Amino Acids, Sugars, and Proteins

Modeling and Applications of Downstream Processing

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