Twist-bend coupling and the torsional response of double-stranded DNA

TL;DR

This paper demonstrates that incorporating twist-bend coupling into models of double-stranded DNA explains experimental deviations in its torsional response, providing a new estimate for the coupling constant and aligning simulations with experimental data.

Contribution

It introduces the concept of twist-bend coupling into DNA mechanical models, resolving previous discrepancies and estimating the coupling constant from experimental data.

Findings

Twist-bend coupling constant estimated at 40 ± 10 nm.

Simulations with coupling align with high-resolution magnetic-tweezers data.

Coupling significantly influences DNA's mechanical properties.

Abstract

Recent magnetic tweezers experiments have reported systematic deviations of the twist response of double-stranded DNA from the predictions of the twistable worm-like chain model. Here we show, by means of analytical results and computer simulations, that these discrepancies can be resolved if a coupling between twist and bend is introduced. We obtain an estimate of 40 $\pm$ 10 nm for the twist-bend coupling constant. Our simulations are in good agreement with high-resolution, magnetic-tweezers torque data. Although the existence of twist-bend coupling was predicted long ago (Marko and Siggia, Macromolecules 27, 981 (1994)), its effects on the mechanical properties of DNA have been so far largely unexplored. We expect that this coupling plays an important role in several aspects of DNA statics and dynamics.