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Published May 5, 1991 | public
Book Section - Chapter

Long-Range Electron Transfer in Heme Proteins Porphyrin-Ruthenium Electronic Couplings in Three Ru(His)Cytochromes c

Abstract

The kinetics of long-range electron transfer (ET) have been measured in Ru(NH_3)_4L(His 39) derivatives (L is NH_3, pyridine, or isonicotinamide) of Zn-substituted Candida krusei cytochrome c and Ru(NH_3)_4L(His 62) derivatives (L is NH_3 or pyridine) of Zn-substituted Saccharomyces cerevisiae cytochrome c. The rates of both excited-state electron transfer and thermal recombination are approximately 3 times greater in Ru(His 39)cytochrome c (Zn) than the rates of the corresponding reactions in Ru(His 33)cytochrome c (Zn), but analogous ET reactions in Ru(His 62)cytochrome c (Zn) are roughly 2 orders of magnitude slower than in the His 33-modified protein. Analysis of driving-force dependences establishes that the large variations in the ET rates are due to differences in donor-acceptor electronic couplings. Examination of potential ET pathways indicates that hydrogen bonds could be responsible for the enhanced electronic couplings in the Ru(His 39) and Ru(His 33) proteins.

Additional Information

© 1991 American Chemical Society. Received for review April 27, 1990. Accepted revised manuscript August 29, 1990. Published in print 5 May 1991. We thank David Beratan for helpful discussions. Both M. J. Therien (National Institutes of Health) and Β. E. Bowler (Medical Research Council of Canada) acknowledge postdoctoral fellowships. Research at the California Institute of Technology was suported by the National Science Foundation (CHE88-22988) and the National Institutes of Health (DK19038). Research performed at Brookhaven National Laboratory was carried out under Contract DE-AC02-CH00016 with the U.S. Department of Energy and supported by its Division of Chemical Sciences, Office of Basic Energy Sciences.

Additional details

Created:
August 20, 2023
Modified:
January 14, 2024