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Updated: Feb 28, 2026

Magnetic Tweezers for the Measurement of Twist and Torque
Published on: May 19, 2014
Twist-Bend Coupling and the Torsional Response of Double-Stranded DNA
Stefanos K Nomidis1,2, Franziska Kriegel3, Willem Vanderlinden3,4
1KU Leuven, Institute for Theoretical Physics, Celestijnenlaan 200D, 3001 Leuven, Belgium.
Abstract:
Recent magnetic tweezers experiments have reported systematic deviations of the twist response of double-stranded DNA from the predictions of the twistable wormlike 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±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 [J. Marko and E. Siggia, Macromolecules 27, 981 (1994)MAMOBX0024-929710.1021/ma00082a015], 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.
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