Models for Relaxation in Glasses and Protein Channels

Abstract

Generally speaking, similarities of relaxation in glasses and biomolecules are due to the fact that in both cases a very large number of molecular configurations is involved in the relaxation processes1. A characteristic feature of relaxation in such complex systems is the non-exponential time dependence of the relaxation functions; in the case of glasses the measured relaxation functions are usually well described by Kohlrausch’s fractional-exponential formula. One of the first models for non-exponential relaxation in glasses and undercooled melts was Glarum’s defect-diffusion model2. An extension of the model, in which the molecular units visited by a defect relax with a finite rate, is presented. It is shown that a related defect-diffusion model can be applied successfully to the relaxation processes in ionic channels in protein molecules, which lead to a non-exponential distribution of the closed times of the channels. Considering the special case of a closed-time distribution following a power law, a general model for the gating kinetics of ionic channels is formulated, which is characterized by a waiting-time distribution. The waiting-time distribution is found to follow the same power law.KeywordsChannel WallRelaxation FunctionClosed TimeFinite RateMolecular UnitThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.