Statistical mechanics of supercoiled DNA

J. F. Marko*, E. D. Siggia

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

322 Scopus citations


The two strands of a closed circular DNA molecule possess as a topological invariant their linking number. This property, combined with an appreciable twist elastic constant, causes the double helix to assume a supercoiled conformation in space when a nonequilibrium twist is imposed. Thermal fluctuations play a crucial role in determining the conformation of supercoils, setting the linking number scale at which a well defined interwound supercoil forms. In addition to equilibrium supercoil structure, we discuss supercoil bending and branching and show how at large scales supercoiled DNA becomes a branched polymer. The characteristic time required for intrasupercoil reactions to occur and the force necessary to extend twisted DNA are also derived.

Original languageEnglish (US)
Pages (from-to)2912-2938
Number of pages27
JournalPhysical Review E
Issue number3
StatePublished - 1995

ASJC Scopus subject areas

  • Statistical and Nonlinear Physics
  • Statistics and Probability
  • Condensed Matter Physics


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