Outer-sphere electron-transfer between horse heart cytochrome c and anionic Cu(II/I) complexes: Evidence for precursor formation and coordination sphere reorganization for electron transfer

Körner, Manuela, Tregloan, Peter A. and van Eldik, Rudi (2003) Outer-sphere electron-transfer between horse heart cytochrome c and anionic Cu(II/I) complexes: Evidence for precursor formation and coordination sphere reorganization for electron transfer. Dalton Transactions, 13: 2710-2717. doi:10.1039/b301693e

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Author Körner, Manuela
Tregloan, Peter A.
van Eldik, Rudi
Title Outer-sphere electron-transfer between horse heart cytochrome c and anionic Cu(II/I) complexes: Evidence for precursor formation and coordination sphere reorganization for electron transfer
Journal name Dalton Transactions   Check publisher's open access policy
ISSN 1477-9226
Publication date 2003
Sub-type Article (original research)
DOI 10.1039/b301693e
Open Access Status File (Publisher version)
Issue 13
Start page 2710
End page 2717
Total pages 8
Place of publication London, U.K.
Publisher Royal Society of Chemistry
Language eng
Subject 03 Chemical Sciences
0302 Inorganic Chemistry
Abstract The outer-sphere electron-transfer reaction between anionic bis(5,6-bis(4-sulfonatophenyl)-3- (2-pyridyl)-1,2,4-triazine)Cu(II) and cytochrome cII was investigated as a function of pH, ionic strength, concentration, temperature and pressure. The plot of the observed pseudo-first-order rate constant as a function of the Cu(II) complex concentration showed saturation at higher Cu(II) concentrations, from which the precursor formation constant and the electron transfer rate constant could be separated (K = (7.7 ′ 0.5) × 103 M 1 and kET= 6.2 ′ 0.4 s -1 at I = 0.2 M, pH 7.4 and 288 K). The pseudo-first-order electron-transfer rate constant was measured as a function of temperature and pressure at (low and) high Cu(II) concentrations (ΔH= (85 ′ 4) 89 ′ 4 kJ mol -1; ΔS= (-61 ′ 13) -79 ′ 15 J K-1 mol-1; ΔG (288 K) = (67.6) 66.1 kJ mol-1; ΔV= (+8.8 ′ 0.6)+8.0 ′ 0.7 cm3 mol-1). Within the volume change for the overall reaction, the volume profile for the electron transfer step is almost symmetrical. The redox process and the change in coordination of the copper centre are proposed to be clearly separated. The back reaction between the Cu(I) complex and cytochrome cIII was investigated as a function of Cu(I) concentration at pH 7.4 at l bar. The observed pseudo-first-order rate constant reaches a saturation at high Cu(I) concentrations from which the precursor formation constant and the electron-transfer rate constant were estimated (K' = (2.0 ′ 0.2) × 103 M-1 and k'ET = 0.014 ′ 0.001 s-1 at I = 0.2 M, pH 7.4 and 288 K). Simulations of the measured cyclovoltammogramms applying an EC mechanism with two redox systems and two homogeneous chemical reactions were performed. The results are discussed with reference to earlier studies involving Co, Ru and Cr complexes as redox partners for cytochrome c.
Keyword Electron-transfer dynamics
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
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