Solvent effects on conformational dynamics of proteins: Cytochrome c in a dried trehalose film

The spectral diffusion dynamics of free base cytochrome c (H2-Cc) in a dry trehalose film is tremendously enhanced as compared to a glycerol/water glass. We show that relaxation as well as fluctuation processes contribute to the spectral diffusion dynamics. Relaxation shows up in aging phenomena which can be measured in a separate fashion. In both solvents, the spectral diffusion as well as the aging dynamics follow power laws in time. The respective exponents are quite different, yet the influence of the solvent on them is only marginal. The large difference in the magnitude of the spectral diffusion dynamics in the two solvents can be traced back to a correspondingly large difference in the inhomogeneous width which itself seems to come from the much higher glass transition temperature in trehalose, which is close to the unfolding temperature of cytochrome c.