Wringing out DNA.
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.
Lionnet
Timothée
T
Laboratoire de Physique Statistique, CNRS UMR 8550, Ecole Normale Supérieure, Paris, France. lionnet@lps.ens.fr
Joubaud
Sylvain
S
Lavery
Richard
R
Bensimon
David
D
Croquette
Vincent
V
D020029:Base Pairing; D004247:DNA / Q000737:chemistry*; D004278:DNA, Superhelical / Q000737:chemistry; D004548:Elasticity; D019277:Entropy; D009690:Nucleic Acid Conformation; D013314:Stress, Mechanical
D004278:DNA, Superhelical; D004247:DNA