Thermodynamics and kinetics of protein folding: A mean field theory

Abstract

The kinetic Ising model in the mean field approximation is applied to study the equilibrium and kinetic behaviors of protein folding–unfolding. In our model, we regard a protein as a topological collection of interacting peptide bonds (or other protein units). According to this model, thermodynamics and kinetics of protein folding–unfolding are related to the elementary process of folding ↔ unfolding of such interacting units. We shall show that even for the so-called two-state case of protein folding–unfolding, the kinetic behaviors are predicted to be in general non-exponential and that universal curves exist separately for the thermodynamic behaviors and kinetics behaviors of protein folding–unfolding. Our model can treat the effect of temperature and denaturant concentration on the thermodynamics and kinetics of protein folding–unfolding and provide the chevron plot. Satisfactory demonstrations are presented for treating experimental observations on the thermodynamical and kinetic responses of protein folding–unfolding to the changes in temperature and denaturant concentration and for exhibiting universal plots of proteins.