Cubic equation governing the outer-region dielectric constant of globular proteins

Abstract

Based on the Fröhlich-Kirkwood theory of dielectrics and homogenization theory, a cubic equation is proposed for the outer-region dielectric constant of a globular protein in aqueous solution. The results for simple test cases confirm that a soluble globular protein may be considered to consist of a hydrophobic core surrounded by a hydrophilic external surface. Considering the widespread debate and ambiguity about the dielectric constant of proteins, the equation is expected to provide a straightforward way to determine the critical parameter for characterizing the relaxation of a protein in response to a charged perturbation.