Regensburg 2010 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 3: DNA, RNA and Associated Enzymes
BP 3.5: Vortrag
Montag, 22. März 2010, 15:30–15:45, H43
Integrative investigation of DNA supercoiling under tension — •Robert Schöpflin1, Hergen Brutzer2, René Stehr1, Ralf Seidel2, and Gero Wedemann1 — 1University of Applied Sciences Stralsund, 18435 Stralsund, Germany — 2Biotechnology Center Dresden, University of Technology Dresden, 01062 Dresden, Germany
Recent studies of high resolution single molecule experiments yielded detailed information of DNA supercoiling under applied tension. Here, an approach integrating experimental, numerical and analytical methods was used to understand these data. Linear DNA was investigated with magnetic tweezers under different concentrations of monovalent ions over a range of pulling forces and added supercoils. According to this we performed Monte Carlo (MC) simulations with a coarse-grained DNA model considering stretching, bending, twisting and electrostatics. The simulations reproduce well the experimentally observed behavior: A force and salt dependent abrupt buckling at the onset of the plectonemic phase is followed by a linear length decrease with added turns. The buckling transition is accompanied by an abrupt DNA length decrease depending on the ionic conditions. Beyond an overall qualitative agreement, the MC simulations reproduce quantitatively many of the experimental parameters. These include the slope and torque of the linear decrease after buckling as well as the jump size and the torque change during abrupt buckling. Moreover, we developed an analytical model for the description of DNA supercoiling. This model describes well both data from experiment and simulation when incorporating a reduced DNA charge.