TUNNELING CURRENTS IN ELECTRON-TRANSFER REACTIONS IN PROTEINS

A new theoretical method for the analysis of the superexchange couplin g and localization of electron tunneling pathways in long distance ele ctron transfer reactions is introduced. The new method allows one to e xamine spatial distribution of microscopic quantum mechanical tunnelin g currents flowing through individual atoms, or to evaluate the relati ve probability that the tunneling electron will pass through an indivi dual atom, in the intervening medium between donor and acceptor in the course of an electron transfer reaction. It is shown how the interato mic tunneling currents introduced in this paper can be calculated usin g methods of quantum chemistry. The method provides a rigorous theoret ical framework for the description of the tunneling process in long-ra nge electron transfer reactions in proteins. The relation of the prese nt theory of tunneling currents to the theory of pathways of Beratan a nd Onuchic is discussed. (C) 1996 American Institute of Physics.