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 e nergy, E-r, in electron transfer between a metalloprotein and a small react ion partner. The protein is represented as a dielectric globule with low di electric constant, the metal centres as conducting spheres, all embedded in a continuous solvent with high dielectric constant. This model has previou sly reproduced thermodynamic metalloprotein properties. E-r takes an analyt ic form expressed by a continuous image charge distribution, and depends we akly 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. (C) 1999 Elsevier Science B.V. All rights reserved.