Simulation of the effect of reorientation of hydrogen bonds in proteins on long-range electron transfer.

We present Monte Carlo simulations illustrating the influence of reorientation of hydrogen bonds in proteins on long-range interprotein electron transfer. The lattice protein model employed mimics the electron donor (or acceptor) interacting with an antiparallel β sheet. In addition, we take into account harmonic vibrations of the medium and also the dependence of the coupling matrix element on orientation of hydrogen bonds near the donor and/or acceptor. The results obtained show that the interaction between the tunneling electron and amino-acid residues, which are responsible for the formation of hydrogen bonds, may result in broadening the parabolic dependence of the electron-transfer rate constant on the reaction exothermicity and also in deviations from this dependence especially in the cases when the β sheet is linked with the electron donor.