Microcanonical versus Canonical Analysis of Protein Folding

TL;DR

This paper demonstrates that microcanonical analysis effectively characterizes protein folding transitions, distinguishing good from bad folders by identifying first-order-like features such as negative specific heats and bimodal energy distributions.

Contribution

It introduces microcanonical analysis as a powerful method for studying protein folding, supported by off-lattice models and parallel tempering Monte Carlo simulations.

Findings

Microcanonical analysis reveals first-order-like folding transition features.

Good folders show robustness against interaction parameter perturbations.

Negative microcanonical specific heats indicate transition characteristics.

Abstract

The microcanonical analysis is shown to be a powerful tool to characterize the protein folding transition and to neatly distinguish between good and bad folders. An off-lattice model with parameter chosen to represent polymers of these two types is used to illustrate this approach. Both canonical and microcanonical ensembles are employed. The required calculations were performed using parallel tempering Monte Carlo simulations. The most revealing features of the folding transition are related to its first-order-like character, namely, the S-bend pattern in the caloric curve, which gives rise to negative microcanonical specific heats, and the bimodality of the energy distribution function at the transition temperatures. Models for a good folder are shown to be quite robust against perturbations in the interaction potential parameters.