Ard Louis

Abstract:

We apply a recently-developed coarse-grained model of DNA, designed to capture the basic physics of nanotechnological DNA systems, to the study of a 'burnt-bridges' DNA motor consisting of a single-stranded cargo that steps processively along a track of single-stranded stators. We demonstrate that the model is able to simulate such a system, and investigate the sensitivity of the stepping process to the spatial separation of stators, finding that an increased distance can suppress successful steps due to the build up of unfavourable tension. The mechanism of suppression suggests that varying the distance between stators could be used as a method for improving signal-to-noise ratios for motors that are required to make a decision at a junction of stators.

Abstract:

We use a recently developed coarse-grained model to simulate the overstretching of duplex DNA. Overstretching at 23C occurs at 74 pN in the model, about 6-7 pN higher than the experimental value at equivalent salt conditions. Furthermore, the model reproduces the temperature dependence of the overstretching force well. The mechanism of overstretching is always force-induced melting by unpeeling from the free ends. That we never see S-DNA (overstretched duplex DNA), even though there is clear experimental evidence for this mode of overstretching under certain conditions, suggests that S-DNA is not simply an unstacked but hydrogen-bonded duplex, but instead probably has a more exotic structure.