Company. INTERACTION MODELS FOR WATER IN RELATION TO PROTEIN HYDRATION

For molecular dynamics simulations of hydrated proteins a simple yet reliable model for the intermolecular potential for water is required. Such a model must be an effective pair potential valid for liquid densities that takes average many—body interactions into account. We have developed a three—point charge model (on hydrogen and oxygen positions) with a Lennard— Jones 6—12 potential on the oxygen positions only. Parameters for the model were determined from 12 molecular dynamics runs covering the two—dimensional parameter space of charge and oxygen repulsion. Both potential energy and pressure were required to coincide with experimental values. The model has very satisfactory properties, is easily incorporated into protein—water potentials, and requires only 0.25 sec computertime per dynamics step (for 216 molecules) on a CRAY—1 computer. 1