A Polarizable Force Field and Continuum Solvation Methodology for Modeling of Protein-Ligand Interactions.

A polarizable force field, and associated continuum solvation model, have been developed for the explicit purpose of computing and studying the energetics and structural features of protein binding to the wide range of ligands with potential for medicinal applications. Parameters for the polarizable force field (PFF) are derived from gas-phase ab initio calculations and then utilized for applications in which the protein binding to ligands occurs in aqueous solvents, wherein the charge distributions of proteins and ligands can be dramatically altered. The continuum solvation model is based on a self-consistent reaction field description of solvation, incorporating an analytical gradient, that allows energy minimizations (and, potentially, molecular dynamics simulations) of protein/ligand systems in continuum solvent. This technology includes a nonpolar model describing the cost of cavity formation, and van der Waals interactions, between the continuum solvent and protein/ligand solutes. Tests of the structural accuracy and computational stability of the methodology, and timings for energy minimizations of proteins and protein/ligand systems in the condensed phase, are reported. In addition, the derivation of polarizability, electrostatic, exchange repulsion, and torsion parameters from ab initio data is described, along with the use of experimental solvation energies for determining parameters for the solvation model.