Berlin 2018 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 28: Single Molecule Biophysics

BP 28.5: Hauptvortrag

Donnerstag, 15. März 2018, 10:30–11:00, H 1058

Multiplexed Magnetic Tweezers: From DNA Mechanics to Retroviral Integration — •Jan Lipfert, Franziska Kriegel, Willem Vanderlinden, and Philipp Walker — Department of Physics and Center for Nanoscience, LMU Munich, Germany

Magnetic tweezers are a powerful tool to probe single DNA molecules and their complexes with proteins under controlled forces and torques at the single molecule level. Using a parallelized version of magnetic tweezers that can measure torque directly, we have carried out high-precision torque measurements of DNA mechanics. Our results indicate that the intrinsic torsional stiffness does not change with mono- or divalent ion concentration and is approximately independent of temperature, for temperatures well below the melting temperature. Quantitative comparison of high-resolution single molecules measurements to coarse-grained simulations of DNA mechanics shows that taking into account the anisotropy of DNA and introducing a non-zero twist-bend coupling significantly improves agreement with torque measurements. In addition, we demonstrate that all-atom molecular dynamics simulations correctly predict the temperature-dependence of DNA twist and of DNA torsional stiffness, if the most recent force fields are used. Going beyond bare DNA, we have developed a magnetic tweezers assay to follow retroviral integration in real time, revealing several critical steps along the integration free energy landscape. In particular, we find an ultra stable strand transfer complex that suggests the role of a resolving factor in vivo.