J. Phys. Chem. 1986, 90, 3800-3804
3800
bution to the Franck-Condon factor F, which determines the E T rate, eq 11.1, originates from the protein modes. These polar medium modes essentially involve dislocation and rotation of polar groups of the protein. These modes differ from the optical modes of a polar liquid, which are prominent in the Marcus theory of ET1-Sand which involve rotations of solvent molecules. Our admittedly simplified treatment of ET, which rests on a single mode approximation, eq 111.1, provides only an average, coarsegrained description of the nature of the nuclear modes relevant for the ET dynamics. The magnitude of the average nuclear frequency ho = 100 cm-I emerging from our analysis of three ET processes implies that the dominating contribution to electron-phonon coupling originates from the medium modes, Le., E J E ,
