Browse by author
Lookup NU author(s): Emeritus Prof Alfred Sykes
Full text for this publication is not currently held within this repository. Alternative links are provided below where available.
Rate constants k12/M-1 s-1 (22°C) for the reduction of the oxidised form of horse-heart cytochrome c by eight organic radicals (OR), e.g., methyl viologen MV•+, determined by pulse radiolysis and/or stopped-flow methods, correlate well in a plot of log k12 vs reduction potential E°1 for the OR. In the pulse radiolysis experiments the ORs were generated in situ by rapid reduction of the parent form by the formate radical CO2•-, and in the stopped-flow experiments prior reduction of the parent was with dithionite. In both procedures it was necessary to consider formation of double-reduced parent forms. Rate constants k12 are in the range 109 to 104 and E°1 values from -0.446 to +0.194V. The Marcus free-energy plot of log10 k12 - 0.5 log10 f vs F°1/0.059 gives a slope of 0.49, in excellent agreement with the theoretical value of 0.50, with an intercept at -E°1/0.059 = 0 of 6.55 in good agreement with a calculated value of 6.51 from known parameters. The latter includes the reduction potential E°2 (0.263V) and self-exchange rate constant k22 (0.36 x 103 M-1 s-1) for the cytochrome c(III)/(II) couple, and assumes a common self-exchange rate constant k11 of 1.0 x 106 M-1 s-1 for the ORs.
Author(s): Borman CD, Dobbing AM, Salmon GA, Sykes AG
Publication type: Article
Publication status: Published
Journal: Journal of Physical Chemistry B
Year: 1999
Volume: 103
Issue: 31
Pages: 6605-6610
Print publication date: 05/08/1999
ISSN (print): 1520-6106
ISSN (electronic): 1520-5207
Publisher: American Chemical Society
URL: http://dx.doi.org/10.1021/jp984520g
DOI: 10.1021/jp984520g
Altmetrics provided by Altmetric
