Estimating the effect of protein dynamics on electron transfer to the special pair in the photosynthetic reaction center

The importance of dynamical fluctuations on the tunneling matrix element of electron transfer has been probed using the Pathway model. The effect of fluctuations of atoms was estimated by optimizing their though-space coupling, thus mimicking the effect of real dynamics. Application of this simple model to the electron transfer between cytochrome c2 and photosynthetic reaction center shows that atomic motion could increase the overall intermolecular electronic coupling by over one order of magnitude. These results indicate that, for this system, thermal fluctuations are necessary to obtain the fast inter-protein unimolecular electron transfer rate (around 1 μs.)