On the driving forces for protein-protein association.

We analyze all the contributions to the standard free energy of association between two proteins. We find that the solvent-induced interactions between two (or more) hydrophilic groups can turn a highly unfavorable process of association into a highly favorable one. We therefore argue that in contrast to the generally accepted view, it is the hydrophilic rather than the hydrophobic effect that is dominant in biochemical processes such as protein-protein association, protein folding, and protein binding to DNA.