Protein electron transfer: a numerical study of tunneling through fluctuating bridges

A central challenge of protein electron-transfer theory is to understand how the protein dynamics influences the electron tunneling from donor to acceptor. It is shown that tunneling (as a function of time) through a fluctuating protein bridge is drastically different from tunneling through a chemically identical static bridge. The static two-state approximation that leads to the donor–acceptor matrix element TDA, is therefore inadequate. A time-dependent two-state approximation is found that describes the tunneling dynamics through a fluctuating bridge. The fluctuating system electronic Hamiltonians are constructed from molecular dynamics trajectories at the CNDO-SCF level.