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Dependence of Intramolecular Electron-Transfer Rates on Driving Force, pH, and Temperature in Ammineruthenium-Modified Ferrocytochromes c
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Section:Abstract
Several ruthenium ammine complexes were used to modify horse-heart cytochrome c at histidine-33, creating a series of (NH3)4(L)Ru−Cyt c derivatives (L = H2O/OH-, ammonia, 4-ethylpyridine, 3,5-lutidine, pyridine, isonicotinamide, N-methylpyrazinium) with a wide range of driving forces for Fe-to-Ru electron transfer (−ΔG° = −0.125 to +0.46 eV). Electron-transfer rates and activation parameters were measured by pulse radiolysis using azide or carbonate radicals. The driving-force dependence of electron-transfer rates between redox centers of the same charge types obeys Marcus−Hush theory. The activationless rate limit for all of the ruthenium derivatives except the N-methylpyrazinium complex is 3.9 × 105 s-1. Thermodynamic parameters obtained from nonisothermal differential pulse voltammetry show that the electron-transfer reactions are entropy-driven. The thermodynamic and kinetic effects of phosphate ion binding to the ruthenium center are examined. The rate of intramolecular electron transfer in (NH3)4(isn)RuIII−Cyt cII decreases at high pH, with a midpoint at pH 9.1.
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This article has been cited by 9 ACS Journal articles (5 most recent appear below).
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Ruthenium Bisbipyridine Complexes of Horse Heart Cytochrome c: Characterization and Comparative Intramolecular Electron-Transfer Rates Determined by Pulse Radiolysis and Flash Photolysis
Jian Luo, K. Bal Reddy, Abdu S. Salameh, James F. Wishart, and Stephan S. IsiedInorganic Chemistry2000 39 (11), 2321-2329Ruthenium Bisbipyridine Complexes of Horse Heart Cytochrome c: Characterization and Comparative Intramolecular Electron-Transfer Rates Determined by Pulse Radiolysis and Flash Photolysis
Jian Luo, K. Bal Reddy, Abdu S. Salameh, James F. Wishart, and Stephan S. IsiedInorganic Chemistry2000 39 (11), 2321-2329The reaction of [Ru(bpy)2L(H2O)]2+ (bpy = 2,2‘-bipyridine, L = imidazole, water) with reduced horse heart cytochrome c results in coordination of [RuII(bpy)2L] at the His 33 and His 26 sites. Coordination at the His 33 site gave a diastereomeric [RuII(bpy)...
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History
- Published In Issue January 23, 1997
- Received August 13, 1996
Revised November 18, 1996
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