Rigidity of Melting DNA

TL;DR

This paper investigates how DNA's flexibility varies with temperature under stretching and unzipping forces, comparing models with entropic elasticity and intrinsic rigidity, and deriving exact relations for elastic constants influenced by thermal bubbles.

Contribution

It introduces a comparative analysis of DNA flexibility models, deriving exact expressions for elastic constants affected by thermal bubbles and intrinsic rigidity.

Findings

Elastic constant change due to bubbles is obtained exactly.

Elastic constant proportional to square root of bubble fluctuations in rigid model.

Temperature influences DNA flexibility differently depending on the model.

Abstract

The temperature dependence of DNA flexibility is studied in the presence of stretching and unzipping forces. Two classes of models are considered. In one case the origin of elasticity is entropic due to the polymeric correlations, and in the other the double-stranded DNA is taken to have an intrinsic rigidity for bending. In both cases single strands are completely flexible. The change in the elastic constant for the flexible case due to thermally generated bubbles is obtained exactly. For the case of intrinsic rigidity, the elastic constant is found to be proportional to the square root of the bubble number fluctuation.