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CPP: Chemische Physik und Polymerphysik

CPP 9: SYMPOSIUM: Polymer networks and beyond: From molecular structure to materials and biological functions POSTER

CPP 9.2: Poster

Saturday, March 5, 2005, 16:45–18:45, Poster TU D

Chromatin elasticity simulated by a Monte Carlo model — •Frank Aumann, Maïwen Caudron, and Jörg Langowski — Div. Biophysics of Macromolecules, German Cancer Research Center, INF 580, D-69120 Heidelberg

In the present work we estimate basic structural and physical properties of the 30 nm chromatin fiber such as the persistence length and stretching elasticity. The data was obtained by simulating the stretching of a single chromatin fiber on a computer. Our program, applying a Monte Carlo (MC) algorithm, is based on a flexible polymer chain with Debye-Hückel electrostatics, using the two-angle model for the chromatin fiber geometry. Flat disks interacting via an attractive Gay-Berne potential represent the nucleosome core particles. Our results show that a rise of the linker DNA length from 5 to 15 bp leads to a at least 5 times less stiffer chromatin fiber. A Variation of the twisting angles between nucleosomes form 90^∘ to 130^∘ gives a significantly stiffer fiber for higher angles. The simulated persistence lengths and elastic moduli confirm experimental data. Most importantly, we show that the chromatin fiber does not behave as an isotropic elastic rod, its rigidity depends on the direction of deformation: in particular, chromatin is much more resistant to stretching than to bending.