INCORPORATING THE PROTEIN-DIPOLE LANGEVIN-DIPOLE MODEL INTO TANFORD-KIRKWOOD THEORY

A new technique incorporating the protein-dipole Langevin-dipole (PDLD ) model into the Tanford-Kirkwood (TK) formula has been proposed which provides a rather detailed description of solvent and ionic strength effects on the electrostatic energies. Applications of this method to realistic problems have been performed and concern the solvation energ ies of four residues of bovine pancreatic trypsin inhibitor (BPTI) and the pK shift of His-64 of mutant subtilisin BPN'. We focus our calcul ation on the back-field effects of bulk solvent.dagger Our calculation s indicate that the back-field effects of bulk solvent on protein dipo les can simply be ignored, introducing a relative error less than 3%; whereas such back field-effects on protein net charges are relatively important and cannot simply be ignored, especially when considering a system of highly charged species. (C) 1995 by John Wiley & Sons, Inc.