FIG. 1.

(a) Schematic of stretched defect-free double-helix DNA plectonemically buckled under torsional stress. A plectoneme domain contains an end loop that is associated with a nucleation cost of the domain. (b) DNA with a defect located on its contour (denoted by an ‘X’). The defect allows a localized DNA kink that favors nucleation of a defect-pinned plectoneme domain characterized by an energy-saving kinked end loop. However, the immobile nature of the defect spatially pins the domain costing diffusion entropy.