Elastic theory of supercoiled DNA

This paper estimates the configurational energies of a closed DNA molecule in highly supercoiled states. Calculation is based on an elastic rod model characterized by the bending and torsional stiffness constants. We show that the global constraint due to topological restriction leads to highly branched metastable structures. We also clarify the conditions for formation of supercoils by linear stability theory and obtain low-frequency vibrational spectra of relatively simple supercoiled structures. It is shown that even a small number of duplex unwindings can lead to the instability of a circle for a wide range of elastic constants.