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Wringing Out DNA

2006; American Physical Society; Volume: 96; Issue: 17 Linguagem: Inglês

10.1103/physrevlett.96.178102

1092-0145

Timothée Lionnet, Sylvain Joubaud, Richard Lavery, David Bensimon, Vincent Croquette,

Nanopore and Nanochannel Transport Studies

The chiral nature of DNA plays a crucial role in cellular processes. Here we use magnetic tweezers to explore one of the signatures of this chirality, the coupling between stretch and twist deformations. We show that the extension of a stretched DNA molecule increases linearly by 0.42 nm per excess turn applied to the double helix. This result contradicts the intuition that DNA should lengthen as it is unwound and get shorter with overwinding. We then present numerical results of energy minimizations of torsionally restrained DNA that display a behavior similar to the experimental data and shed light on the molecular details of this surprising effect.