Exact Partition Function Zeros of the Wako-Saitô-Muñoz-Eaton Protein Model

Abstract

Protein is an intrinsically finite size system with heterogeneous components, which is in contrast to infinite-size homogeneous systems studied in traditional statistical physics, and it is of interest to see to what extent methodologies of statistical physics can be used for studying protein folding. Partition function zeros(PFZs) method is a tool used in statistical physics for studying phase transition, where instead of computing quantities in real temperature, the zeros of the partition function in the complex temperature plane are examined. In this work, I show that the PFZs method can be used for distinguishing two-state and barrierless downhill folding transitions, by computing exact partition function zeros of the Wako-Saito-Munoz-Eaton protein model. I compute the PFZs for various secondary structural elements, and for two proteins 1BBL and 1I6C, which exhibit features that clearly distinguish distinct types of folding transitions. The result is expected to form basis for further application of the method to finite heterogeneous systems.Physical Review Letters 110 (2013) 248101.