Mechanism of protein salting in and salting out by divalent cation salts: balance between hydration and salt binding

Arakawa, Tsutomu; Timasheff, Serge N.

doi:10.1021/bi00320a004

Cited by 625 publications

(436 citation statements)

References 33 publications

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“…This is done by multiplying the calculated value of (apz/am3);,,,, by the ratio, R , of the experimental to the calculated value determined for systems that show no evidence of binding. In previous studies, it has been shown that R has values between 0.5 and 0.7 (Arakawa & Timasheff, 1982a, 1983, 1984b, which are similar to those calculated by Honig and co-workers from geometric considerations Sharp et al, 1991). Therefore, for consistency, all the preferential interaction parameters calculated with the Gibbs adsorption isotherm were corrected by this factor.…”

Section: Separation Of the Measured Preferential Exclusion Into Contrsupporting

confidence: 58%

“…All of these co-solvents raise the surface tension of water. The good correlation between the measured negative preferential interactions and the positive surface tension increment in their presence (Arakawa & Timasheff, 1982a, 1982b, 1983, 1984bKita et al, 1994) led to the proposal that this is the principal source of the unfavorable free energy of the interactions of these co-solvents with proteins. These observations have suggested that the stabilization of proteins by these co-solvents is due to the increase of the surface tension in their presence.…”

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confidence: 99%

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On the role of surface tension in the stabilization of globular proteins

1996

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The stabilization of proteins by a variety of co-solvents can be related to their property of increasing the surface tension of water. It is demonstrated that, during the thermal unfolding of proteins, this increase of the surface tension can be overcome by the increase in the temperature of the solution at the midpoint of the transition, T,, and the weak binding of co-solvent molecules. Three such co-solvents were studied: trehalose, lysine hydrochloride (LysHCl), and arginine hydrochloride (ArgHC1). Trehalose and LysHCl increase the midpoint of T,. The increase of the surface tension by addition of trehalose is completely compensated by its decrease due to the increase in T,. However, for LysHC1, the increase of the surface tension by the co-solvent is partly reduced by its binding to the protein. Later studies on the preferential interaction2 of proteins with a variety of co-solvents have identified the surface tension ef-'The term preferential interaction refers to the net interaction between the protein and the solvent components, water and the co-solvent, as measured by an equilibrium thermodynamic approach, such as dialysis equilibrium. When the interactions are weak, as is the case with co-solvents, such as sugars, glycerol, amino acids, or urea, the measured quantity is the net balance between the weak interactions (binding) of water and co-solvent molecules to the protein over its entire surface. If, on average, the affinity of protein surface loci for the co-solvent is greater than that for water, the dialysis equilibrium experiment will result in an excess of co-solvent at the protein surface over its concentration in the bulk solvent, and the measured binding stoichiometry will be positive, which means that co-solvent is preferentially bound relative to water. In that case, the "preferential binding" will be positive. In the converse case, in which, on average, the affinity of the protein surface loci is greater for water than for co-solvent molecules, there will be an excess of water at the protein surface over its concentration in the 372

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Section: Separation Of the Measured Preferential Exclusion Into Contrsupporting

confidence: 58%

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confidence: 99%

On the role of surface tension in the stabilization of globular proteins

1996

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“…This behavior is observed with other molecules such as ionic liquids 79 and proteins. 43,57 However, the solubility effects observed with the amino acids studied here are the opposite. The Mg 2+ cation seems to be a strong salting-in agent, in good agreement with its "chaotropic" character described for other biomolecules such as polymers, 80 charged polypeptides 45 and some amino acids.…”

Section: Methodsmentioning

confidence: 72%

Salting-in with a Salting-out Agent: Explaining the Cation Specific Effects on the Aqueous Solubility of Amino Acids

et al. 2013

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Although the understanding of ion specific effects on the aqueous solubilities of biomolecules is crucial for the development of many areas of biochemistry and life sciences, a consensual and well-supported molecular picture of the phenomena has not yet been established. Mostly, the influence of cations and the nature of the molecular interactions responsible for the reversal of the Hofmeister trend in aqueous solutions of amino acids and proteins are still defectively understood. Aiming at contributing to the understanding of the molecular-level mechanisms governing the cation specific effects on the aqueous solubilities of biocompounds, experimental solubility measurements and classical molecular dynamics simulations were performed for aqueous solutions of three amino acids (alanine, valine, and isoleucine), in the presence of a series of inorganic salts. The evidence gathered suggests that the mechanism by which salting-in inducing cations operate in aqueous solutions of amino acids is different from that of anions, and allows for a novel and consistent molecular description of the effect of the cation on the solubility based on specific interactions of the cations with the negatively charged moieties of the biomolecules.

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“…On the other hand, the D fraction in Timasheff, 1984;Timasheff, 1992Timasheff, , 1993. In the lower concentration range of (NH4)?SO, (typically < O S M), the salting-in effect is superior to the preferential hydration effect, often resulting in destabilization of the folded state of proteins.…”

Section: Some Results In Water and Co-solvent Solutionsmentioning

confidence: 99%

Conformational diversity of acid‐denatured cytochrome c studied by a matrix analysis of far‐UV CD spectra

Konno

1998

Protein Science

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The singular value decomposition (SVD) analysis was applied to a large set of far-ultraviolet circular dichroism (far-UV CD) spectra (100-400 spectra) of horse heart cytochrome c (cyt c). The spectra were collected at pH 1.7-5.0 in (NH4)2S04r sorbitol and 2,2,2-trifluoroethanol (TFE) solutions. The present purpose is to develop a rigorous matrix method applied to far-UV CD spectra to resolve in details conformational properties of proteins in the non-native (or denatured) regions. The analysis established that three basis spectral components are contained in a data set of difference spectra (referred to the spectrum of the native state) used here. By a further matrix transformation, any observed spectrum could be decomposed into fractions of the native (N), the molten-globule (MG), the highly denatured (D), and the alcohol-induced helical (H) spectral forms. This method could determine fractional transition curves of each conformer as a function of solution conditions, which gave the results consistent with denaturation curves of cyt c monitored by other spectroscopic methods. The results in sorbitol solutions, for example, suggested that the preferential hydration effect of the co-solvent stabilizes the MG conformer of cyt c. This report has found that the systematic SVD analysis of the far-UV CD spectra is a powerful tool for the conformational analysis of the non-native species of a protein when it is suitably supplemented with other experimental methods.

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Mechanism of protein salting in and salting out by divalent cation salts: balance between hydration and salt binding

Cited by 625 publications

References 33 publications

On the role of surface tension in the stabilization of globular proteins

On the role of surface tension in the stabilization of globular proteins

Salting-in with a Salting-out Agent: Explaining the Cation Specific Effects on the Aqueous Solubility of Amino Acids

Conformational diversity of acid‐denatured cytochrome c studied by a matrix analysis of far‐UV CD spectra

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