Dynamics of frozen proteins as investigated by optical hole burning experiments

We measured the spectral diffusion broadening of persistent holes burnt int o the absorption band of myoglobin- and cytochrome c-type proteins as a fun ction of waiting time. In addition we varied the ageing time. Although spec tral diffusion broadening is subject to ageing, especially below 1 K, the p roteins can be brought to conditions where spectral diffusion broadening is close to a stationary behavior. The time evolution of the linewidth follow s a power law in time which signals that the associated motion in conformat ion space seems to be governed by diffusive-like processes. (C) 2000 Elsevi er Science B.V. All rights reserved.