Fig. 6.
Representative structure from an MD simulation of a highly overwound (σ=0.391) DNA duplex (Randall et al. 2009). The very high torsional strain is relieved by the formation of a 5 bp region of P-DNA, allowing the remainder of the helix to relax back to B-DNA (bottom). Counterion densities are contoured in dark blue showing the expected signatures in the grooves of the B-DNA region. In the region of P-DNA, counterions are highly concentrated near the intertwined negatively charged backbones.