A Consistent Experimental and Modeling Approach to Light-Scattering Studies of Protein-Protein Interactions in Solution

Abstract

The osmotic second virial coefficient, B(2), obtained by light scattering from protein solutions has two principal components: the Donnan contribution and a contribution due to protein-protein interactions in the limit of infinite dilution. The Donnan contribution accounts for electroneutrality in a multicomponent solution of (poly)electrolytes. The importance of distinguishing this ideal contribution to B(2) is emphasized, thereby allowing us to model the interaction part of B(2) by molecular computations. The model for protein-protein interactions that we use here extends earlier work (Neal et al., 1998) by accounting for long-range electrostatic interactions and the specific hydration of the protein by strongly associated water molecules. Our model predictions are compared with measurements of B(2) for lysozyme at 25 degrees C over pH from 5.0 to 9.0, and 7-60 mM ionic strength. We find that B(2) is positive at all solution conditions and decreases with increasing ionic strength, as expected, whereas the interaction part of B(2) is negative at all conditions and becomes progressively less negative with increasing ionic strength. Although long-range electrostatic interactions dominate this contribution, particularly at low ionic strength, short-range electrostatic/dispersion interactions with specific hydration are essential for an accurate description of B(2) derived from experiment.

Lysozyme‐lysozyme self‐interactions as assessed by the osmotic second virial coefficient: Impact for physical protein stabilization

“…They have also shown a quantitative agreement between virial coefficients measured by SIC and by static light scattering. This is also evident from other studies [53,[81][82]. These examples show that the SIC method is a reliable technique for measuring virial coefficients.…”

Reexamining protein–protein and protein–solvent interactions from Kirkwood-Buff analysis of light scattering in multi-component solutions

“…[38][39][40][41] The approach proposed by Stockmayer has been the most widely used and accepted. [42][43][44][45][46] For thermodynamic convenience and mathematical simplicity, Stockmayer's treatment and those of others make the simplifying assumption that fluctuations in pressure ( p) and solvent (water) concentration are negligible within the scattering volume. That is, the scattering (sub)volume is treated as though it contains a constant number of water molecules, and it is implicitly assumed that one can neglect the differences between constant pressure and constant volume for the scattering region of the fluid.…”

“…That is, the scattering (sub)volume is treated as though it contains a constant number of water molecules, and it is implicitly assumed that one can neglect the differences between constant pressure and constant volume for the scattering region of the fluid. Corrections have also been applied to account for requirements of electroneutrality and resulting Donnan effects on A 2 , 44 particularly for the case of protein solutions. As noted above, recent derivations 32,33 have been proposed that argue A 2 from LS contains contributions from other osmotic virial coefficients, or from Donnan contributions via constraints of electroneutrality.…”

“…As noted above, recent derivations 32,33 have been proposed that argue A 2 from LS contains contributions from other osmotic virial coefficients, or from Donnan contributions via constraints of electroneutrality. 44 Alternatively, Casassa and Eisenberg 47, 48 corrected Stockmayer's treatment by imposing electroneutrality through the equilibration of protein with cosolutes within the scattering volume (a correction which was implicitly obtained herein). Nevertheless, in all of the above cases, fluctuations in pressure and solvent concentration are neglected, and fluctuations in the remaining species are related to LS intensity via thermodynamic transformations that express non-idealities in terms of activity coefficients, 38,39,42,44,[49][50][51] implying, as it is shown below, that information about interactions between solvent and all the other components is not recovered explicitly, but rather it is convoluted within A 2 and the apparent molecular weight.…”

Specificity of molecular recognition in oligomerization of bacterial L-asparaginases

“…На сегодняшний день существует множество экспериментальных методов, с помощью которых можно исследовать белок-белковые взаимодействия при олигомеризации и сборке мультисубъединичных белков [9][10][11][12]. Существуют также биоинформационные подходы, позволяющие предсказывать белок-белковые взаимодействия, оценивать возможную устойчивость белковых комплексов, предсказывать возможные контактные участки в структурах белков и так далее.…”