Resonance effects in strongly exothermic long-range electron transfer and their possible implications for the behaviour of site-directed mutant proteins

Long-range electron transfer investigations of hemoproteins, blue copper and iron-sulphur proteins frequently rest on electronically excited metal centres. When the excitation energy approaches the oxidation of reduction potentials of intermediate residues the super-exchange view normally used, however, fails and a variety of new dynamic features arise. These all involve population of intermediate cation or anion residue states which can be partially or wholly vibrationally relaxed. Suitable views and a new theoretical formalism for these phenomena are discussed. The authors also note some important implications for site-directed mutagenesis in long-range, strongly exothermic electron transfer processes. (author). 36 refs.; 4 figs