Electron transfer in ruthenium-modified proteins.
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.
Bjerrum
M J
MJ
California Institute of Technology, Pasadena 91125, USA.
Casimiro
D R
DR
Chang
I J
IJ
Di Bilio
A J
AJ
Gray
H B
HB
Hill
M G
MG
Langen
R
R
Mines
G A
GA
Skov
L K
LK
Winkler
J R
JR
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
D003574:Cytochrome c Group; D001400:Azurin; D006639:Histidine; D012428:Ruthenium