The relaxation time for a cruciform structure in superhelical DNA.

We have calculated the relaxation time of a cruciform structure in superhelical DNA as a function of the superhelix density for palindromic regions of different lengths. The relaxation time has a sharp maximum at the superhelix density which corresponds to the equilibrium transition point between the cruciform structure and the regular double helix. This maximal value is shown to depend dramatically on the length of the palindromic region.