Electrostatic Protein-Protein Interactions: Comparison of Point-Dipole and Finite-Length Dipole Potentials of Mean Force.

Based on summation of Coulombic interactions, a model is developed for finite-length dipole potentials of mean force in a salt-free dielectric continuum. Point-dipole and finite-length dipole potentials of mean force are compared for protein-protein interactions using parameters for bovine alpha-chymotrypsin. The two approximations made in the commonly used analytical point-dipole potentials of mean force are not valid at distances near contact. Relative to the finite-length dipole model, the high-temperature approximation overpredicts, and the point-dipole approximation underpredicts charge-dipole and dipole-dipole attractions.