RT Journal Article
SR Electronic
T1 Torque and buckling in stretched intertwined double-helix DNAs
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 135905
DO 10.1101/135905
A1 Brahmachari, Sumitabha
A1 Marko, John F.
YR 2017
UL http://biorxiv.org/content/early/2017/05/09/135905.abstract
AB We present a statistical-mechanical model for the behavior of intertwined DNAs, with a focus on their torque and extension as a function of their catenation (linking) number and applied force, as studied in magnetic tweezers experiments. Our model produces results in good agreement with available experimental data, and predicts a catenation-dependent effective twist modulus distinct from what is observed for twisted individual double-helix DNAs. We find that buckling occurs near to the point where experiments have observed a kink in the extension versus linking number, and that the subsequent “supercoiled braid” state corresponds to a proliferation of multiple small plectoneme structures. We predict a discontinuity in extension at the buckling transition corresponding to nucleation of the first plectoneme domain. We also find that buckling occurs for lower linking number at lower salt; the opposite trend is observed for supercoiled single DNAs.