Low frequency dynamics of Cytochrome c

Femtosecond coherence spectroscopy is used to investigate the low frequency dynamics of cytochrome c (cyt c). There is good agreement between the higher frequency oscillatory components of the coherence spectra and the low frequency Raman spectra. A mode near $\sim $40 cm$^{-1}$ is a universal feature of heme systems and has been assigned to doming motions that are strongly enhanced upon ligand photolysis [1]. A dominant heme ruffling mode near $\sim $60 cm$^{-1}$ [2] appears in ferric cyt c for excitation in the region 425-432nm, to the red of the Soret maximum (408nm). This, along with a phase jump of $\sim \pi $ in this region, suggests the ruffling mode is coupled to a charge transfer (CT) band underlying the Soret band [3] and that it is a potentially important electron transfer reaction coordinate. [1] F. Gruia, M. Kubo, X. Ye, P. M. Champion, \textit{Biophys. J}., \textbf{2008}, $94$, 2252. [2] M. Kubo, F. Gruia, A. Benabbas, A. Barabanschikov, W. R. Montfort, E. M. Maes, P. M. Champion, \textit{J. Am. Chem. Soc.,} \textbf{2008}, $130$, 9800. [3] K. T. Schomacker, P. M. Champion, \textit{J. Chem. Phys.,} \textbf{1986}, $84$, 5314.