Discrete charge patterns, Coulomb correlations and interactions in protein solutions

Abstract

The effective Coulomb interaction between globular proteins is calculated as a function of monovalent salt concentration cs, by explicit Molecular Dynamics simulations of pairs of model proteins in the presence of microscopic co and counterions. For discrete charge patterns of monovalent sites on the surface, the resulting osmotic virial coefficient B2 is found to be a strikingly non-monotonic function of cs. The non-monotonicity follows from a subtle Coulomb correlation effect which is completely missed by conventional non-linear Poisson-Boltzmann theory and explains various experimental findings.