Thermal Denaturation of Fluctuating DNA Driven by Bending Entropy

TL;DR

This paper presents an exact statistical model of DNA denaturation that couples internal base pair states with external chain fluctuations, revealing a transition driven by bending entropy and explaining experimental observations.

Contribution

It introduces a novel exactly solvable model linking DNA base pair states with chain fluctuations, elucidating the thermally driven denaturation transition.

Findings

Denaturation bubbles depend on temperature and DNA length.

The model predicts a transition driven by bending entropy.

Conformational properties match experimental data.

Abstract

A statistical model of homopolymer DNA, coupling internal base pair states (unbroken or broken) and external thermal chain fluctuations, is exactly solved using transfer kernel techniques. The dependence on temperature and DNA length of the fraction of denaturation bubbles and their correlation length is deduced. The thermal denaturation transition emerges naturally when the chain fluctuations are integrated out and is driven by the difference in bending (entropy dominated) free energy between broken and unbroken segments. Conformational properties of DNA, such as persistence length and mean-square-radius, are also explicitly calculated, leading, e.g., to a coherent explanation for the experimentally observed thermal viscosity transition.