PT  - JOURNAL ARTICLE
AU  - Brahmachari, Sumitabha
AU  - Marko, John F.
TI  - Torque and buckling in stretched intertwined double-helix DNAs
AID  - 10.1101/135905
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 135905
4099  - http://biorxiv.org/content/early/2017/05/09/135905.short
4100  - http://biorxiv.org/content/early/2017/05/09/135905.full
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.