Berlin 2008 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 7: Posters I

BP 7.18: Poster

Montag, 25. Februar 2008, 17:00–19:30, Poster A

Characterizing circular semiflexible polymers — •Karen Alim and Erwin Frey — Arnold Sommerfeld Center for Theoretical Physics and CeNS, Department of Physics, Ludwig-Maximilians-Universtät München, Theresienstr. 37, 80333 München

Circular polymers such as viral DNA, plasmids or cytoskeletal bundles play a crucial role in various biological processes. We examine the shape of circular semiflexible polymers over their whole range of flexibility observing two distinct shape regimes depending on the flexibility of the polymer [1]. For small perimeter to persistence length the fluctuating rings exhibit only planar, elliptical configurations. At higher flexibilities three dimensional, crumpled structures arise. Analytic calculations confirm the qualitative behavior of the shape parameters and the elliptical shape in the stiff regime.

Further characteristic measures for circular semiflexible polymers are derived based on an elastic rod model with anisotropic bending stiffness and twist stiffness [2]. In this polymer ribbon model the geometric constraint causes an effective stiffning of bending modes and a coupling of bending and twisting modes. Furthermore, our model predicts the mean square diameter of a ribbonlike ring thus giving a novel parameter to determine bending and twist stiffnesses of polymers and especially bundles in experiments.

[1] K. Alim and E. Frey, Shapes of semiflexible polymer rings, Phys. Rev. Lett. 99, 198102 (2007)

[2] K. Alim and E. Frey, Fluctuating semiflexible polymer ribbon constrained to a ring, Eur. Phys. J. E, in press