FINITE-DIFFERENCE POISSON-BOLTZMANN ELECTROSTATIC CALCULATIONS - INCREASED ACCURACY ACHIEVED BY HARMONIC DIELECTRIC SMOOTHING AND CHARGE ANTIALIASING

A common problem in the calculation of electrostatic potentials with t he Poisson-Boltzmann equation using finite difference methods is the e ffect of molecular position relative to the grid. Preciously a uniform charging method was shown to reduce the grid dependence substantially over the point charge model used in commercially available codes. In this article we demonstrate that smoothing the charge and dielectric v alues on the grid can improve the grid independence, as measured by th e spread of calculated values, by another order of magnitude. Calculat ions of Born ion salvation energies, small molecule solvation energies , the electrostatic field of superoxide dismutase, and protein-protein binding energies are used to demonstrate that this method yields the same results as the paint charge model while reducing the positional e rrors by several orders of magnitude. (C) 1997 by John Wiley & Sons, I nc.