The Dynamics and Energy Landscape of DNA Plectoneme Nucleation

DNA buckling is the fundamental step for plectoneme nucleation and supercoil dynamics that are critical in the processing of genetic information. Here we systematically quantify DNA buckling dynamics using high-speed magnetic tweezers. Buckling times are [~]10-100 ms and depend exponentially on both applied force and twist. By deconvolving measured time traces with the instrument response, we reconstruct full 2D extension-twist energy landscapes of the buckling transition that reveal an asymmetry between the pre- and post-buckling states and suggest a highly bend transition state conformation.