Statistical Mechanics of Torque Induced Denaturation of DNA

TL;DR

This paper presents a comprehensive theoretical model describing DNA denaturation driven by temperature or mechanical torque, highlighting a first-order phase transition and matching experimental observations.

Contribution

It introduces a unifying model coupling hydrogen-bond opening and helicoidal untwisting, providing new insights into DNA denaturation mechanisms.

Findings

Denaturation is a first-order phase transition from B-DNA to d-DNA.

The phase diagram in T-Gamma plane aligns with experimental data.

The model accurately predicts the temperature dependence of the twist angle.

Abstract

A unifying theory of the denaturation transition of DNA, driven by temperature T or induced by an external mechanical torque Gamma is presented. Our model couples the hydrogen-bond opening and the untwisting of the helicoidal molecular structure. We show that denaturation corresponds to a first-order phase transition from B-DNA to d-DNA phases and that the coexistence region is naturally parametrized by the degree of supercoiling sigma. The denaturation free energy, the temperature dependence of the twist angle, the phase diagram in the T,Gamma plane and isotherms in the sigma, Gamma plane are calculated and show a good agreement with experimental data.