Phase diagram of a semiflexible polymer chain in a $\theta$ solvent: application to protein folding

TL;DR

This paper models a semiflexible polymer in a bad solvent using a lattice approach, exploring how temperature, stiffness, and attraction influence its phase behavior, with implications for understanding protein folding.

Contribution

It introduces a lattice model incorporating stiffness and attraction to study the phase diagram relevant to protein folding.

Findings

Identifies phase transitions between extended and compact states.

Shows the role of stiffness in secondary structure formation.

Provides a simplified framework for protein folding thermodynamics.

Abstract

We consider a lattice model of a semiflexible homopolymer chain in a bad solvent. Beside the temperature $T$, this model is described by (i) a curvature energy $\varepsilon_h$, representing the stiffness of the chain (ii) a nearest-neighbour attractive energy $\varepsilon_v$, representing the solvent (iii) the monomer density $\rho={N \over \Omega}$, where $N$ and $\Omega$ denote respectively the number of monomers and the number of lattice sites. This model is a simplified view of the protein folding problem, which encompasses the geometrical competition between secondary structures (the curvature term modelling helix formation) and the global compactness (modeled here by the attractive energy), but contains no side chain information...