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BP: Fachverband Biologische Physik

BP 8: Posters: Proteins

BP 8.18: Poster

Montag, 11. März 2013, 17:30–19:30, Poster B2

Mechanical properties of sister chromatids studied by a polymer model — •Sebastian Isbaner, Yang Zhang, and Dieter W. Heermann — Institute for Theoretical Physics, Heidelberg University, Germany

A chromosome in metaphase consists of two highly condensed sister chromatids forming a chromosome. In experiments, chromosomes show characteristic force-extension curves with a linear region followed by a plateau. However, where and how exactly sister chromatids are linked to each other and how these links influence their overall organization and mechanical properties is still not well understood. In this work, we use a dynamic folding model for mitotic chromatids and investigate the influence of dynamic cross-links between two model sister chromatids. Our results show that the number of sister links has severe influence on the overall organization of the model chromatids. Too few cross-links cause the model chromatids to drift apart due to entropic repulsion, whereas many links result in an agglomeration. We characterize these different states in a phase diagram. We further investigate the force-extension behavior and find that it qualitatively reproduces experimental results. Our results also demonstrate that inter sister cross-links decrease the elasticity compared to isolated model chromatids. In summary, we show that only a limited range for the concentration of inter sister chromatid cross-links can exist to result in observed chromosome shapes and our model is able to reproduce experimental findings for the elasticity of chromosomes.