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BP: Fachverband Biologische Physik
BP 4: DNA \& DNA Enzymes
BP 4.8: Vortrag
Montag, 14. März 2011, 16:15–16:30, ZEU 260
Probing the elasticity of DNA on short length scales by modeling supercoiled DNA under tension — •Robert Schöpflin1, Hergen Brutzer2, Oliver Müller1, Ralf Seidel2, and Gero Wedemann1 — 1University of Applied Sciences Stralsund, 18435 Stralsund, Germany — 2Biotechnology Center Dresden, University of Technology Dresden, 01062 Dresden, Germany
The worm-like-chain (WLC) is the most commonly used theoretical framework for modeling the flexibility of DNA. However, recently alternative so-called sub-elastic chain (SEC) models [1] were proposed that predict for large deflections a higher flexibility than the usual harmonic model. So far, no unambiguous verification of these models has been obtained since probing the elasticity of DNA on short length scales remains challenging. Here, we address this question by modeling single-molecule supercoiling experiments of DNA under tension [2] using high-resolution Monte Carlo simulations. DNA supercoiling under tension is accompanied by an abrupt buckling at the transition from the stretched to the superhelical, i.e. plectonemic, state. This transition is due to the extreme bending of the DNA in the end loop of the plectoneme and serves therefore as a sensitive benchmark for model evaluations. While simulations that employ regular WLC bending energetics quantitatively reproduce the buckling transition, the buckling almost disappears for SEC models. Thus, DNA bending is best described by a harmonic model down to bending radii of 3 nm.
[1] Wiggins, P., et al. Nat Nanotechnol. 1(2):137-41 (2006)
[2] Brutzer, H., et al. Biophys J. 98(7):1267-76 (2010)