New Measurements of DNA Twist Elasticity

TL;DR

This paper reports the first direct measurement of the twist-stretch coupling in DNA, introduces a simple microscopic theory predicting similar values, and discusses implications for DNA elasticity under constraints.

Contribution

It provides the first experimental measurement of DNA's twist-stretch coupling and a theoretical prediction aligning with observed data.

Findings

Measured the twist-stretch coupling parameter in DNA.

Developed a simple microscopic theory predicting the coupling.

Discussed effects of twist constraints on DNA elasticity.

Abstract

The symmetries of the DNA double helix require a new term in its linear response to stress: the coupling between twist and stretch. Recent experiments with torsionally-constrained single molecules give the first direct measurement of this new material parameter. We extract its value from a recent experiment. We also present a very simple microscopic theory predicting a value comparable to the one observed. Finally we sketch the effect of constrained twist on entropic elasticity of DNA arising from the connection between Link, Twist, and Writhe.