Photoinduced electron-transfer kinetics of singly labeled ruthenium bis(bipyridine) dicarboxybipyridine cytochrome c derivatives.
Cytochrome c derivatives labeled at specific lysine amino groups with ruthenium bis(bipyridine) dicarboxybipyridine [RuII(bpy)2(dcbpy)] were prepared by using the procedure described previously [Pan, L. P., Durham, B., Wolinska, J., & Millett, F. (1988) Biochemistry 27, 7180-7184]. Four additional singly labeled derivatives were purified, bringing the total number to 10. These derivatives have a strong luminescence emission centered at 662 nm arising from the excited state, RuII*. Transient absorption spectroscopy was used to directly measure the rate constants for the photoinduced electron-transfer reaction from RuII* to the ferric heme group (k1) and for the thermal back-reaction from the ferrous heme group to RuIII (k2). The rate constants were found to be k1 = 14 X 10(6) s-1 and k2 = 24 X 10(6) s-1 for the derivative modified at lysine 72, which has a distance of 8-16 A between the ruthenium and heme groups. Similar rate constants were found for the derivatives modified at lysines 13 and 27, which have distances of 6-12 A separating the ruthenium and heme groups. The rate constants were significantly slower for the derivatives modified at lysine 25 (k1 = 1 X 10(6) s-1, k2 = 1.5 X 10(6) s-1) and lysine 7 (k1 = 0.3 X 10(6) s-1, k2 = 0.5 X 10(6) s-1), which have distances of 9-16 A. Transients due to photoinduced electron transfer could not be detected for the remaining derivatives, which have larger distances between the ruthenium and heme groups.(ABSTRACT TRUNCATED AT 250 WORDS)
Durham
B
B
Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville 72701.
Pan
L P
LP
Long
J E
JE
Millett
F
F
D015082:2,2'-Dipyridyl / Q000031:analogs & derivatives / Q000378:metabolism*; D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D002845:Chromatography; D003574:Cytochrome c Group / Q000378:metabolism*; D004579:Electron Transport; D006736:Horses; D007700:Kinetics; D008027:Light; D009942:Organometallic Compounds; D011725:Pyridines / Q000378:metabolism*; D012428:Ruthenium; D013057:Spectrum Analysis
D003574:Cytochrome c Group; D009942:Organometallic Compounds; D011725:Pyridines; D015082:2,2'-Dipyridyl; C058014:ruthenium bis(bipyridine)dicarboxybipyridine; D012428:Ruthenium