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DY: Fachverband Dynamik und Statistische Physik

DY 10: Posters I

DY 10.23: Poster

Montag, 14. März 2011, 17:00–19:00, P4

Anomalous diffusion in crowded fluids revealed by a novel single-particle tracking technique — •Dominique Ernst¹, Marcel Hellmann³, Matthias Weiss², and Jürgen Köhler¹ — ¹Experimental Physics IV, University of Bayreuth, 95440 Bayreuth, Germany — ²Experimental Physics I, University of Bayreuth, 95440 Bayreuth, Germany — ³Cellular Biophysics Group, German Cancer Research Center, 69120 Heidelberg, Germany

A versatile setup for automated single particle tracking in two dimensions is used to analyse anomalous diffusion processes in crowded fluids with a high spatio-temporal resolution. The ingenious tracking technique allows us to record trajectories of a single fluorescent nanoparticle (20 nm) for more than 15 minutes with a temporal resolution of 4 ms and a dynamic position accuracy of about 25 nm. We create a light orbit with a focussed laser beam and project that light orbit with a homebuilt fluorescence microscope into the sample plane. At the beginning of the tracking procedure, the nanoparticle has to be located in the center of the orbit. Subsequently, we detect the modulation of the emission intensity due to the movement of the particle out of the center of the light orbit, calculate the new position of the particle from the modulation parameters, and compensate for the movement of the particle with the aid of a piezostage. From that feedback we reconstruct the trajectory of the particle and determine the mean square displacement. Here we present the method and as an example its application to diffusion in crowded fluids like dextran as a model system for the cytoplasm of a cell.