Regensburg 2004 – wissenschaftliches Programm
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AKB: Biologische Physik
AKB 50: Poster Session "Biological Physics"
AKB 50.123: Poster
Freitag, 12. März 2004, 10:30–13:00, B
Structure and Elasticity of DNA and Chromatin — •Ralf Everaers1 and Boris Mergell2 — 1Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzerstr. 38, 01187 Dresden, Germany — 2Max-Planck-Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany
We use computer simulations to study structure formation and response to mechanical forces in generic linked rigid body models of DNA and chromatin. In the case of DNA we use a variant of the Gay-Berne potential to represent the stacking interactions between neighboring base-pairs. The sugar-phosphate backbones are taken into account by semi-rigid harmonic springs with a non-zero spring length. The competition of these two interactions and the introduction of a simple geometrical constraint lead to a stacked right-handed B-DNA-like conformation. Beyond a critical stretching force we observe a transition to an overstretched S-DNA conformation with highly inclined bases that partially preserves the stacking of successive base-pairs. The geometry of the chromatin fiber is based on the two-angle crossed-linker model. In this case the Gay-Berne potential is used to model the excluded volume and short-range attraction between nucleosomes. We find that the elastic properties such as the bending and stretching moduli of condensed fibers are dominated by the internucleosomal interactions. They can lead to the formation of hairpin conformations whose tension induced opening manifests itself in a quasi-plateau in the force-extension curve.