Differential behavior of curved DNA upon untwisting

We have synthesized DNA segments with different handedness, twisting and radii of curvature, and have analyzed the effect of untwisting on them. The results indicate that the dynamic behavior of curved DNA upon untwisting is strongly determined by the initial sequence-dependent DNA trajectory. In particular, DNA with the same radii but with opposite handedness of superhelix twisting can show very different conformational responses to ethidium bromide untwisting. Upon treatment with ethidium bromide, right-handed superhelixes decrease their twist and increase the planarity of the superhelix, while left-handed superhelixes increase twisting and decrease their degree of planarity.