INTRAMOLECULAR ELECTRON-TRANSFER BETWEEN RU(I) AND RU(III) AND THE HEME IRON OF CYTOCHROME-C LABELED WITH RUTHENIUM(II) POLYPYRIDINE COMPLEXES

The rates of intramolecular electron transfer between Ru(III) and Fe(II) of three derivatives of cytochrome c labeled at lysines 86, and and 7 with Ru(4,4'-dicarboxybipyridine)(bipyridine)2(2+) have been measured. The respective rate constants are 1.1x10(5), 1.3x10(5) and 6x10(5) s(-1). Corresponding rates of electron transfer between Ru(I) and Fe(III) of these derivatives have also been measured. The respective rate constants are 3.3 x 10(5), 5.7x10(5) and 1x10(6) s(-1). In addition the rate constant for a derivative labeled at lysine 87 was determined to be 2.7x10(5) s(-1). The two sets of rate constants appeared to be correlated with each other with respect to the location of the ruthenium label. The Ru(I) rate constants are 2-3 times larger than the corresponding Ru((III) rate constants. Preliminary analysis suggests that the observed rate constants are not consistent with the large free energy of reaction expected for Ru(I).