Dielectric properties of proteins from simulation: The effects of solvent,ligands, pH, and temperature

We have used a standard Frohlich-Kirkwood dipole moment fluctuation model t o calculate the static dielectric permittivity, epsilon (0), for four diffe rent proteins, each of which was simulated under at least two different con ditions of pH, temperature, solvation, or ligand binding. For the range of proteins and conditions studied, we calculate values for epsilon (0) betwee n 15 and 40. Our results show, in agreement with prior work, that the behav ior of charged residues is the primary determinant of the effective permitt ivity. Furthermore, only environmental changes that alter the properties of charged residues exert a significant effect on epsilon. In contrast, burie d water molecules or ligands have little or no effect on protein dielectric properties.