Model studies on the effects of neutral salts on the conformational stability of biological macromolecules. I. Ion binding to polyacrylamide and polystyrene columns

Hippel, Peter H. von; Peticolas, Virginia; Schack, Lise; Karlson, Lynne

doi:10.1021/bi00731a003

Cited by 139 publications

(80 citation statements)

References 21 publications

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“…3 (18,(32)(33)(34)(35), although the effects are much larger than with the peptides. A similar ranking (Br-> Cl-> F-) was observed for the interaction of these anions with polyacrylamide, which was used as a model for the peptide backbone (36). All of the above studies suggest that acetate, glutamate, or fluoride salts should minimize preferential anion binding in protein-nucleic acid interactions.…”

Section: Methodssupporting

confidence: 52%

Thermodynamic extent of counterion release upon binding oligolysines to single-stranded nucleic acids.

Mascotti

Lohman

1990

Proc. Natl. Acad. Sci. U.S.A.

187

232

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A major contribution to the binding free energy associated with most protein-nucleic acid complexes is the increase in entropy due to counterion release from the nucleic acid that results from electrostatic interactions. To examine this quantitatively, we have measured the thermodynamic extent of counterion release that results from the interaction between single-stranded homopolynucleotides and a series of oligolysines, possessing net charges z = 2-6, 8, and 10. This was accomplished by measuring the salt dependence of the intrinsic equilibrium binding constants-i.e., (olog Kw/ 8log [KJ])-over the range from 6 mM to 0.5 M potassium acetate. These data provide a rigorous test of linear polyelectrolyte theories that have been used to interpret the effects of changes in bulk salt concentration on protein-DNA binding equilibria, since single-stranded nucleic acids have a lower axial charge density than duplex DNA. Upon binding to poly(U), the thermodynamic extent of counterion release per oligolysine charge, z, is 0.71 ± 0.03, which is signfilcandy less than unity and less than that measured upon binding duplex DNA. These results are most simply interpreted using the limiting law predictions of counterion condensation and cylindrical Poisson-Boltzmann theories, even at the high salt concentrations used in our experiments. Accurate estimates of the thermodynamic extent of counterion binding and release for model systems such as these facilitate our understanding of the energetics of protein-nucleic acid interactions. These data indicate that for simple oligovalent cations, the number of ionic interactions formed in a complex with a linear nucleic acid can be accurately estimated from a measure of the salt dependence of the equilibrium binding constant, if the thermodynamic extent of ion release is known.The interactions of proteins with nucleic acids are central to the control of gene expression and nucleic acid metabolism. A detailed understanding of how these processes are regulated requires information about the equilibrium affinity and pathways of association and dissociation of the proteinnucleic acid complexes involved. Structural data can provide information concerning the contacts made within proteinnucleic acid complexes; however, thermodynamic information is necessary to understand the stability of these complexes. One A number of theoretical studies have sought to obtain a quantitative molecular interpretation of these dramatic salt effects (1,(3)(4)(5)(6)(7). Two of these were based on counterion condensation (CC) models that describe the electrostatic interaction of counterions with linear nucleic acids (1,5). The CC models (5,8) treat the nucleic acid as a uniform line charge and predict that a constant fraction of the phosphate charges is neutralized by the delocalized binding (condensation) of counterions. The extent of counterion condensation per phosphate, which is predicted by CC theory, is a function only of the linear charge density of the nucleic acid, the counterion charge, and the d...

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Section: Methodssupporting

confidence: 52%

Thermodynamic extent of counterion release upon binding oligolysines to single-stranded nucleic acids.

Mascotti

Lohman

1990

Proc. Natl. Acad. Sci. U.S.A.

187

232

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“…The constituent ions of these salts can be arranged into Hofmeister series, which comprise ranked lists of the effectiveness of these ions in increasing or decreasing the goodness of the solvent (86). Chaotropic ions, such as iodides, thiocyanates, and perchlorates, destabilize structures and complexes by favoring residue exposure on surfaces, whereas stabilizingions, such as sulfates and phosphates, favor the burial of residues and thus promote oligomerization and aggregation (82). It is this latter property that makes concentrated ammonium sulfate solutions effective in protein fractionation.…”

Section: Thermodynamic Principles and Macromolecular Structurementioning

confidence: 99%

From “Simple” DNA-Protein Interactions to the Macromolecular Machines of Gene Expression

Hippel

2007

Annu. Rev. Biophys. Biomol. Struct.

Self Cite

180

140

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The physicochemical concepts that underlie our present ideas on the structure and assembly of the "macromolecular machines of gene expression" are developed, starting with the structure and folding of the individual protein and DNA components, the thermodynamics and kinetics of their conformational rearrangements during complex assembly, and the molecular basis of the sequence specificity and recognition interactions of the final assemblies that include the DNA genome. The role of diffusion in reduced dimensions in the kinetics of the assembly of macromolecular machines from their components is also considered, and diffusion-driven reactions are compared with those fueled by ATP binding and hydrolysis, as well as by the specific covalent chemical modifications involved in rearranging chromatin and modifying signal transduction networks in higher organisms.

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“…The tendency for a salt to cause denaturation of a protein is inversely related to its position in Hofmeister series (1 0). Von Hippel (39) suggested that the Hofmeister series is related to the interaction between ions and the hydrophobic groups of the protein. It is the hydrophobic part of a protein that governs the salting-out of protein in salt solution.…”

Section: The Theoretical Basis Of This Equation Is Not Clearmentioning

confidence: 99%

Some characteristics of protein precipitation by salts

Shih

Prausnitz

Blanch

1992

Biotech & Bioengineering

150

114

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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.

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Model studies on the effects of neutral salts on the conformational stability of biological macromolecules. I. Ion binding to polyacrylamide and polystyrene columns

Cited by 139 publications

References 21 publications

Thermodynamic extent of counterion release upon binding oligolysines to single-stranded nucleic acids.

Thermodynamic extent of counterion release upon binding oligolysines to single-stranded nucleic acids.

From “Simple” DNA-Protein Interactions to the Macromolecular Machines of Gene Expression

Some characteristics of protein precipitation by salts

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