Osmotic virial coefficients for model protein and colloidal solutions: Importance of ensemble constraints

Published

May 2, 2012

Author(s)

Daniel Siderius, William P. Krekelberg, Christopher J. Roberts, Vincent K. Shen

Abstract

Rayleigh light scattering is often used to quantify protein-protein interactions in solution via experimental measurement of the osmotic second virial coefficient (OSVC), but analysis of measurements from such experiments requires identification of a scattering volume and the thermodynamic constraints imposed on that volume, i.e., the statistical mechanical ensemble in which light scattering occurs. Depending on the set of constraints imposed on the scattering volume, one can obtain either an apparent OSVC, A_2,app, or the true thermodynamic OSVC, B^osm₂₂, that is rigorously defined in solution theory [Blanco et al., J. Chem. Phys. 134, 225103 (2011)]. However, it is unclear to what extent A_2,app and B^osm₂₂ differ, which may have implications on the physical interpretation of OSVC measurements from light scattering experiments. In this paper we use the multicomponent hard-sphere model and a well-known equation of state to directly compute and compare A_2,app and B^osm₂₂. Our results for the hard-sphere fluid indicate that A_2,app underestimates B^osm₂₂, but in a systematic manner that may be explained using fundamental thermodynamic expressions for the two OSVCs. The difference between A_2,app and B^osm₂₂ may be quantitatively significant, but may also be obscured in experimental application by statistical uncertainty or non-steric interactions. Consequently, the two OSVCs that arise in the analysis of light scattering measurements do formally differ, but in a manner that may not be detectable in actual application.

Citation

Journal of Chemical Physics

Volume

136

Pub Type

Journals

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DOI Link

Keywords

light scattering, osmotic virial coefficient, hard-sphere fluid, protein interaction

Citation

Siderius, D. , Krekelberg, W. , Roberts, C. and Shen, V. (2012), Osmotic virial coefficients for model protein and colloidal solutions: Importance of ensemble constraints, Journal of Chemical Physics, [online], https://doi.org/10.1063/1.4709613 (Accessed April 25, 2024)