Direct Determination of DNA Twist-Stretch Coupling

TL;DR

This paper reports the first direct measurement of DNA twist-stretch coupling from torsionally-constrained single-molecule experiments, compares it with previous estimates, and presents a simple microscopic theory predicting similar values.

Contribution

It provides the first direct experimental measurement of DNA twist-stretch coupling and introduces a simple microscopic model that predicts its magnitude.

Findings

Measured twist-stretch coupling value from experiments

Found rough agreement with previous estimates

Developed a microscopic theory predicting similar values

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. [Science 271 (1996) 1835] 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.