Tunneling currents in proteins: Nonorthogonal atomic basis sets and Mulliken population analysis

A rigorous kinetic justification is given of the expression for interatomic tunneling currents introduced in our earlier work [Stuchebrukhov, J. Chem. Phys. 105, 10819 (1996)] for the analysis of long-distance electron transfer reactions when a nonorthogonal atomic basis set is used for the description of the medium intervening between donor and acceptor. The analysis is based on the kinetic equations describing the evolution of the Mulliken populations of the atomic states in the medium during the tunneling transition of a long-distance electron transfer reaction.