Wringing out DNA

Publication Type:

Journal Article

Source:

PHYSICAL REVIEW LETTERS, AMERICAN PHYSICAL SOC, Volume 96, Number 17, ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA (2006)

DOI:

10.1103/PhysRevLett.96.178102

Keywords:

ENTROPIC ELASTICITY; EXTENSION; FORCE; MODEL; MOLECULAR-DYNAMICS SIMULATIONS; NUCLEIC-ACIDS; SUPERCOILED DNA

Abstract:

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.