Figure 1.

Chain-length dependence of the relative step energy per base pair ε for minicircles bearing a single HU (top) and Hbb (bottom) dimer. The blue circles correspond to the energies of relaxed minicircles over the complete range of chain lengths. The red and orange triangles represent the energies of over- and underwound minicircles, respectively. The horizontal dashed line (ε = 1) corresponds to the energy of a base-pair step in a naked minicircle of the same length. The vertical lines indicate the chain lengths equal to integral numbers of helical repeats.