Dresden 2009 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 20: DNA, RNA and Chromatin

BP 20.6: Vortrag

Donnerstag, 26. März 2009, 15:30–15:45, HÜL 186

Modeling the BS-transition of DNA under tension — •Thomas Rudolf Einert¹, Douglas Staple^2,3, Hans-Jürgen Kreuzer², and Roland Netz¹ — ¹Physik Department, Technische Universität München, 85748 Garching b. München, Germany — ²Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS B3H 3J5 Canada — ³Max-Planck-Institut für Physik komplexer Systeme, 01187 Dresden, Germany

Stretching of double-stranded DNA leads to the denaturation of the molecule. A stretching force F ≈ 65  pN induces a sharp, structural transition where DNA changes from its native state (B-DNA) to a stretched state (S-DNA). At even higher forces the hydrogen bonds break up and loops start to form giving rise to a second, smoother transition.

We present two statistical mechanics models which exhibit both transitions. To describe the behavior of DNA under tension we use the worm-like chain (WLC) model. Our formulation allows to give arbitrary length-dependent weights for loops. Force-extension curves can be calculated analytically and show excellent agreement with experimental data. In the thermodynamic limit genuine phase transitions are possible depending on the parameterization of the three different states (B-DNA, S-DNA, or loops). The phase transitions are characterized by their order and critical exponents.