title: Electron transfer in ruthenium-modified proteins.
abstract: Photochemical techniques have been used to measure the kinetics of intramolecular electron transfer in Ru(bpy)2(im)(His)2(+)-modified (bpy = 2,2'-bipyridine; im = imidazole) cytochrome c and azurin. A driving-force study with the His33 derivatives of cytochrome c indicates that the reorganization energy (lambda) for Fe2+-->Ru3+ ET reactions is 0.8 eV. Reductions of the ferriheme by either an excited complex, *Ru2+, or a reduced complex, Ru+, are anomalously fast and may involve formation of an electronically excited ferroheme. The distance dependence of Fe2+-->Ru3+ and Cu+-->Ru3+ electron transfer in 12 different Ru-modified cytochromes and azurins has been analyzed using a tunneling-pathway model. The ET rates in 10 of the 12 systems exhibit an exponential dependence on metal-metal separation (decay constant of 1.06 A-1) that is consistent with prediction of the pathway model.
authors.affiliation: California Institute of Technology, Pasadena 91125, USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Bjerrum
authors.forename: D R
authors.initials: DR
authors.lastname: Casimiro
authors.forename: I J
authors.initials: IJ
authors.lastname: Chang
authors.forename: A J
authors.initials: AJ
authors.lastname: Di Bilio
authors.forename: H B
authors.initials: HB
authors.lastname: Gray
authors.forename: M G
authors.initials: MG
authors.lastname: Hill
authors.forename: R
authors.initials: R
authors.lastname: Langen
authors.forename: G A
authors.initials: GA
authors.lastname: Mines
authors.forename: L K
authors.initials: LK
authors.lastname: Skov
authors.forename: J R
authors.initials: JR
authors.lastname: Winkler
mesh_terms: D001400:Azurin / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism*; D003574:Cytochrome c Group / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism*; D004579:Electron Transport; D006639:Histidine; D007700:Kinetics; D008962:Models, Theoretical; D010777:Photochemistry / Q000379:methods; D017433:Protein Structure, Secondary; D012428:Ruthenium / Q000494:pharmacology*; D013816:Thermodynamics
chemical_list: D003574:Cytochrome c Group; D001400:Azurin; D006639:Histidine; D012428:Ruthenium