COOPERATIVITY OF WATER-SOLUTE INTERACTIONS AT A HYDROPHILIC SURFACE

We have measured the reversible work required to assemble different se ts of weak model charges at a water/wall interface using molecular dyn amics methods and free energy perturbation techniques. It is found tha t water is a strong mediator of like-charge repulsive forces due to th e ability of water molecules to adopt low free energy configurations t hat maximize the water-ion interaction while minimizing the penalty of the concomitant water rearrangement. The cooperativity of this mechan ism is enhanced at smaller charge separations, but is not associated w ith any strong preferential hydration structure. The presence of solve nt-stabilized, like-charge-charge pairs embedded on a surfaces implies an additional mechanism by which water can stabilize biomolecular ass emblies.