Investigations of Soret excited resonance Raman excitation profiles in cytochrome c

Abstract

Resonance Raman excitation profiles of the ’’oxidation state marker bands’’ in ferric- and ferrocytochrome c are obtained using tunable laser excitation in the Soret region (350–450 nm). The excitation profiles are asymmetric and peak distinctively to the blue of the Soret absorption maximum. The data are explained using a simple model that analytically includes the complete subspace of Franck–Condon active vibrations associated with each intermediate electronic state. In this simple multimode model the damping factor is a ’’soft’’ fitting parameter taken to be wavelength independent. Nevertheless, an excellent fit of the Soret absorption band and Raman excitation profile is achieved. Our theoretical approach places upper limits on the Soret damping factors that are on the order of 50 cm−1 (HWHM) for ferrocytochrome c and on the order of 300 cm−1 (HWHM) for ferricytochrome c.