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DY: Fachverband Dynamik und Statistische Physik

DY 10: Posters I

DY 10.4: Poster

Monday, March 14, 2011, 17:00–19:00, P4

Folding and unfolding of a triple-branch DNA molecule with four conformational states — •Sandra Engel¹, Anna Alemany^2,3, Nuria Forns^2,3, Philipp Maass¹, and Felix Ritort^2,3 — ¹Fachbereich Physik, Universität Osnabrück, Germany — ²Departament de Física Fonamental, Universitat de Barcelona, Spain — ³CIBER-BBN Networking center on Bioengineering, Biomaterials and Nanomedicine, Spain

Single-molecule experiments provide new insights into biological processes hitherto not accessible by measurements performed on bulk systems. We report on a study of the kinetics of a triple-branch DNA molecule with four conformational states by pulling experiments with optical tweezers and theoretical modelling. Three distinct force rips associated with different transitions between the conformational states are observed in the folding and unfolding trajectories. By applying transition rate theory to a free energy model of the molecule, probability distributions for the first rupture forces of the different transitions are calculated. Good agreement of the theoretical predictions with the experimental findings is achieved. Furthermore, due to our specific design of the molecule, we found a useful method to identify permanently frayed molecules by estimating the number of opened basepairs from the measured force jump values.