Multi-plectoneme phase of double-stranded DNA under torsion

Abstract

We use the worm-like chain model to study supercoiling of DNA under tension and torque. The model reproduces experimental data for a broad range of forces, salt concentrations and contour lengths. We find a plane of first order phase transitions ending in a smeared out line of critical points, the multi-plectoneme phase, which is characterized by a fast twist mediated diffusion of plectonemes and a torque that rises after plectoneme formation with increasing linking number. The discovery of this new phase at the same time resolves the discrepancies between existing models and experiment.