Berlin 2012 – scientific programme

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BP: Fachverband Biologische Physik

BP 21: Focus: Stress Relaxation in Polymers - From single molecules to biological cells (with CPP)

BP 21.5: Invited Talk

Thursday, March 29, 2012, 10:45–11:15, C 243

Slow stress relaxation in recoiling polymers — •Ulrich F. Keyser — Cavendish Lab, University of Cambridge, JJ Thomson Ave, Cambridge, CB3 0HE, UK

The internal dynamics of semi-flexible chains in response to external forces is an important problem in soft matter, polymer and biological physics. Here, we describe a novel method to experimentally determine the relaxation of a single DNA molecule with one free end. The electric field in a nanopore[1] or nanocapillary[2] is used to apply a controlled force to one end of a DNA molecule while the other end is held in an optical trap[3,4]. High-speed video tracking of the colloidal particle[5] allows for a direct measurement of the relaxation in the recoiling DNA upon release from the nanopore. We show and discuss our single-molecule experiments for a range of forces and find that stress relaxation and recoiling is much slower than expected from the simple worm-like chain model. Our results pave the way towards investigating the nonlinear dynamics of semiflexible polymer relaxation and test recent theories[6] on propagation and relaxation of backbone tension in DNA.

[1] Keyser et al., Nature Physics 2, 473 (2006) [2] Steinbock et al., Nano Letters 10, 2493 (2010) [3] Steinbock et al., J. Phys. Cond. Mat. 23, 184114 (2010) [4] Otto et al., Rev. Sci. Instr. 82, 086102 (2011) [5] Otto et al., Optics Express 18, 22722 (2010) [6] Hallatschek et al., Phys. Rev. E 75, 031906 (2007)