Modified Poisson equation for the electric field and electric field gradient

Abstract

The dielectric polarization (P) is the key factor in calculating the solvation free energy to explore the stability of protein conformations, binding affinity of protein–protein/ligand interactions, and nonthermal effect of an external electric field on biomolecules. P can be decomposed into the product of the electric dipole per solvent (p), and the solvent molecular density (Nbulkg). p can be calculated from the electric field (E) and g can be calculated from the mean force (F) with the electric component of F calculated from ∇E. Here, the Poisson equation was modified for E and ∇E using a point dipole at the center of a hard sphere as the solvent model. Strategies to estimate the boundary conditions of E and ∇E were proposed. The dependence of p and g on Δh, and of the van der Waals component of F on Rcut were studied. The P and g values calculated from this strategy were similar to those derived from molecular dynamics simulations.