Interactions between proteins are studied by calculating the potential of mean force based on the Poisson-Boltzmann equation. We define a parameter that allows a comparison between the osmotic second virial coefficients obtained from different experimental analytical techniques and provides information about both protein-protein or protein-surface interactions. It can be related to the protein solubility and be used to determine favorable conditions for protein adsorption on a specific surface or protein aggregation. The calculations show reasonable agreement with the experimental second virial coefficient. They also reveal that it is possible to predict different Hofmeister effects observed experimentally in protein solutions. We demonstrate that the effect of including many-body ion-protein dispersion potentials originating from polarizabilities of ions and proteins may offer an explanation for the Hofmeister series. In particular, we give evidence for the inversion of Hofmeister series as function of pH for a given protein.
van der Waals interactions; Hofmeister series; protein adsorption; osmotic second virial coefficient
