Electron-transfer reactions in proteins: electronic coupling in myoglobin

Recent measurements of electron-transfer (ET) rates in Ru(NH_3)_5 His myoglobin derivatives have shown the need for improved theories for treating the "path" of long-range ET. We have investigated these systems theoretically using a combined artificial intelligence (AI)-superexchange method. As in our previous articles, this model first employs an AI search technique that yields the important amino acid residues for the mediation of electrons between the donor and the acceptor. A quantum mechanical method is then used to diagonalize the orbitals of the selected protein subset and to calculate the electronic coupling. Encouraging agreement with experimental data is found, no adjustable parameters having been introduced. The results yield the relevant amino acid paths