NONLOGARITHMIC SPECTRAL DIFFUSION IN PROTEINS AND GLASSES

In the first part of the paper, a quantitative theory is developed and new experimental data are presented, which attribute recently observe d plateaus in three-pulse photon echoes in glasses to laser heating ar tifacts. In the second part, the root t-spectral diffusion, recently o bserved in long time (> 3 h) hole-burning in proteins and glasses, is addressed. Avoiding interacting two-level systems (TLS), we present a model which is supported by MD-simulations and based on the notion of a hierarchical energy landscape. Within it, the algebraic line broaden ing is connected with the side chain dynamics of the polymer glass and the protein; contrary, the standard logarithmic spectral diffusion (S D) is associated with the collective backbone dynamics. Excellent agre ement with experiment is found for both proteins and glasses. The diff erence between them is attributed to the amount of disorder and organi zation in their energy landscapes. (C) 1998 Published by Elsevier Scie nce B.V. All rights reserved.