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Non-monotonic variation with salt concentration of the second virial coefficient in protein solutions

E. Allahyarov·H. Löwen·J. P. Hansen·A. A. Louis
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Abstract

The osmotic virial coefficient $B_2$ of globular protein solutions is calculated as a function of added salt concentration at fixed pH by computer simulations of the ``primitive model''. The salt and counter-ions as well as a discrete charge pattern on the protein surface are explicitly incorporated. For parameters roughly corresponding to lysozyme, we find that $B_2$ first decreases with added salt concentration up to a threshold concentration, then increases to a maximum, and then decreases again upon further raising the ionic strength. Our studies demonstrate that the existence of a discrete charge pattern on the protein surface profoundly influences the effective interactions and that non-linear Poisson Boltzmann and Derjaguin-Landau-Verwey-Overbeek (DLVO) theory fail for large ionic strength. The observed non-monotonicity of $B_2$ is compared to experiments. Implications for protein crystallization are discussed.

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E. Allahyarov, H. Löwen, J. P. Hansen, A. A. Louis. 2002-05-27. Non-monotonic variation with salt concentration of the second virial coefficient in protein solutions. https://doi.org/10.1103/physreve.67.051404

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