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BP: Fachverband Biologische Physik

BP 7: Posters: Statistical Physics in Biological Systems

BP 7.13: Poster

Monday, March 14, 2011, 17:15–20:00, P3

Interaction Dynamics of Colloidal Particles in Scanning Line Optical Tweezers — •Benjamin Tränkle and Alexander Rohrbach — Lab for Bio- and Nano-Photonics, University of Freiburg, Germany

Inter-particle distances are of vital importance for the accomplishment of biological processes, e.g. the fusion of vesicles or drug delivery. Here, the vesicle motions are confined by compartments inherent to the cell structure and also determined by physical interactions, i.e. hydrodynamic and entropic forces. We mimic the biological system by observing the diffusive modes of silica spheres in an elongated potential, which is generated by an oscillating optical trap. The particle positions in 3D are obtained by back focal plane interferometry. Scanning frequencies up to 10 kHz and a spatial precision in the nanometer range are achieved. Our model system allows the particles to get in close contact to one another due to Brownian position fluctuations. Thus pair interactions and dynamics of microspheres can be investigated, e.g. by analyzing the particle trajectories in terms of correlated and anti-correlated motions. Here, the characteristic timescales, i.e. the interaction times are impaired by the shape and stiffness of the trapping potential. We use an acousto-optic deflector to control the laser intensity and hereby vary the trap properties in a broad range. This enables the study of different aspects of particle dynamics.