Converting structural changes upon oxidation of cytochrome c to electrostatic reorganization energy.

The observed X-ray structural differences between reduced and oxidized cytochrome c are converted to electrostatic energy. This conversion is used to estimate the protein reorganization energy which determines the protein contribution to the activation barrier for the electron transfer reaction. It is shown that the reorganization energy of cytochrome c is much smaller than the corresponding energy for electron transfer in water and that this is consistent with the role for cytochromes as electron transfer catalysts.