title: Long-range electron transfer in myoglobin.
abstract: The distance and driving-force dependences of electron transfer (ET) in a set of four surface-ruthenated myoglobins, in which the heme prosthetic group has been systematically replaced by a series of metalloporphyrins of differing excited-state redox potentials, have provided information on the magnitude [Hab(12.7 A) approximately 6.3 x 10(-3) cm-1] and decay [beta approximately 0.8 A-1, where kET alpha exp [-beta(d - do)]] of protein-mediated donor-acceptor electronic coupling. A reorganization energy lambda approximately 1.3 eV, due to coordination and solvation changes both at and between the ET sites, has been estimated using a rate expression that allows electron-vibration coupling to classical and quantum mechanical modes. The contribution to lambda from the porphyrin and peptide matrix is approximately 0.7 eV. Specific electron-tunneling pathways in the protein have been evaluated.
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena 91125.
authors.forename: J A
authors.initials: JA
authors.lastname: Cowan
authors.forename: R K
authors.initials: RK
authors.lastname: Upmacis
authors.forename: D N
authors.initials: DN
authors.lastname: Beratan
authors.forename: J N
authors.initials: JN
authors.lastname: Onuchic
authors.forename: H B
authors.initials: HB
authors.lastname: Gray
mesh_terms: D004579:Electron Transport; D007700:Kinetics; D008958:Models, Molecular; D008962:Models, Theoretical; D009211:Myoglobin / Q000378:metabolism*; D011487:Protein Conformation; D013816:Thermodynamics
chemical_list: D009211:Myoglobin