Twist-Stretch Elasticity of DNA

TL;DR

This paper investigates the twist-stretch coupling in DNA, combining experimental measurements from torsionally-constrained molecules with a simple microscopic theory, revealing insights into DNA's elastic properties.

Contribution

It provides the first direct measurement of DNA's twist-stretch coupling and offers a simple theoretical model predicting its value.

Findings

Measured twist-stretch coupling from experiments

Found rough agreement with previous estimates

Developed a microscopic theory predicting the coupling

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 important material parameter. We extract its value from a recent experiment of Strick, et al. and find rough agreement with an independent experimental estimate recently given by Marko. We also present a very simple microscopic theory predicting a value comparable to the one observed.