Volume 69, Number 1, January 2005
|142 - 148
|Interdisciplinary physics and related areas of science and technology
|10 December 2004
DNA loop statistics and torsional modulus
Laboratoire de Physique, École Normale Supérieure de Lyon 46 allée d'Italie, 69364 Lyon Cedex 7, France
Corresponding author: email@example.com
Accepted: 28 October 2004
The modelling of DNA mechanics under external constraints is discussed. Two analytical models are widely known, but disagree, for instance, on the value of the torsional modulus. The origin of this embarassing situation is located in the concept of writhe. This letter presents a unified model for DNA establishing a relation between the different approaches. I show that the writhe created by the loops of DNA is at the origin of the discrepancy. To take this into account, I propose a new treatment of loop statistics based on numerical simulations using the most general formula for the writhe, and on analytic calculations with only one fit parameter. One can then compute the value of the torsional modulus of DNA without the need of any cut-off.
PACS: 87.15.La – Biomolecules: structure and physical properties: Mechanical properties / 36.20.Ey – Conformation (statistics and dynamics) / 82.35.Lr – Physical properties of polymers
© EDP Sciences, 2005
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