Kinetics of quasi-isoenergetic transition processes in biological macromolecules

TL;DR

This paper derives a master equation for molecular state evolution under stochastic fields, revealing a temperature-independent transition mechanism in flexible biomolecules, exemplified by receptor desensitization and protein degradation.

Contribution

It introduces a novel physical mechanism explaining temperature-independent transitions in molecular systems due to stochastic broadening effects.

Findings

Temperature independence of transition rates at room temperature.

Physical interpretation of receptor desensitization onset.

Explanation of protein degradation processes.

Abstract

A master equation describing the evolution of averaged molecular state occupancies in molecular systems where alternation of molecular energy levels is caused by discrete dichotomous and trichotomous stochastic fields, is derived. This study is focused on the kinetics of quasi-isoenergetic transition processes in the presence of moderately high frequency stochastic field. A novel physical mechanism for temperature-independent transitions in flexible molecular systems is proposed. This mechanism becomes effective when the conformation transitions between quasi-isoenergetic molecular states take place. At room temperatures, stochastic broadening of molecular energy levels predominates the energy of low frequency vibrations accompanying the transition. This leads to a cancellation of the temperature dependence in the stochastically averaged rate constants. As examples, physical interpretations of the temperature-independent onset of P2X$_3$ receptor desensitization in neuronal membranes, as well as degradation of PER2 protein in embrionic fibroblasts, are provided.