Microsecond luminescence emission from copper cytochrome c

The luminescence of Cu-substituted cytochrome c exhibits temperature-dependent decay modes and spectral shifts at temperatures below 80 K. By comparison with the data from metal-substituted porphyrins, we determined intramolecular rate parameters. The observed tripdoublet decay time is 13 +/- 1 mus at 77 K and the quartet decay time is 12 +/- 5 mus below 30 K. We also investigated the luminescence emission from Cu cytochrome c in the presence of cytochrome c depleted mitochondria and in the presence of soluble cytochrome c oxidase; upon binding, the intensity and decay time of the emission are altered. The results indicate an interaction between cytochrome c and its mitochondrial binding site which depends on the electronic state of cytochrome c.