A demonstration of the inhomogeneity of the local dielectric response of proteins by molecular dynamics simulations.

The dielectric properties of proteins are important in determining responses to changes in pH, responses to external electric fields, and the energy associated with charge injection or charge transfer. Although the importance of electrostatic interactions in proteins is well established and they are routinely included in simulations, the dielectric properties of proteins are less frequently discussed. We use a combination of atomistic molecular dynamics simulation and continuum electrostatics models to calculate the local dielectric constant within regions of the model protein hen egg white lysozyme. The local dielectric response of the protein was found to be highly inhomogeneous and strongly dependent on the local chemical environment. In light of these findings, we discuss the use of models using a single effective dielectric constant for the whole protein and the relationship between variations in local protein dielectric response and the activity of protein sites.