A simple approach to the solvent reorganization Gibbs free energy in electron transfer reactions of redox metalloproteins

We discuss a simple model for the environmental reorganisation Gibbs free energy, Er, in electron transfer between a metalloprotein and a small reaction partner. The protein is represented as a dielectric globule with low dielectric constant, the metal centres as conducting spheres, all embedded in a continuous solvent with high dielectric constant. This model has previously reproduced thermodynamic metalloprotein properties. Er takes an analytic form expressed by a continuous image charge distribution, and depends weakly on the globular radius, indicating that repolarisation at the globule/solvent interface contributes less to these effects than to the work terms and driving force.