ELECTRON-TRANSFER IN PROTEINS - A MULTIPLE-SCATTERING APPROACH TO ELECTRONIC COUPLING

An expression for the electronic coupling in electron transfer reactio ns between a donor and an acceptor separated by a bridge is obtained u sing an approach based upon the multiple scattering of an electron in a disordered medium. For homogeneous systems the coupling depends expo nentially upon the distance separating the donor and the acceptor. In the weak scattering limit k(o)l > 1 (where k(o) = 2 pi/lambda(e) with lambda(e) the wavelength of the tunneling electron and l the transpo rt mean free path), the exponent beta, which determines the range of t he electronic coupling, is found to be a function of the energy of the tunneling electron and of the density of each kind of atom in the pro tein. The results for beta from the application of this approach to pr oteins are compared with those that are found in the literature.