Dresden 2011 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 32: Posters: Other Topics in Biological Physics
BP 32.7: Poster
Donnerstag, 17. März 2011, 17:15–20:00, P3
Measuring the non-harmonic potential of an optical trap — •Marcus Jahnel1, 2, Martin Behrndt1, 2, Anita Jannasch3, Erik Schäffer3, and Stephan W. Grill1, 2 — 1Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany — 2Max Planck Institute for the Physics of Complex Systems, Dresden, Germany — 3Biotechnology Center, TU Dresden, Germany
Using optical traps to measure or apply forces on the molecular level requires a precise knowledge of the trapping potential. Close to the trap center, this potential is usually approximated as harmonic. However, applications demanding high forces at low laser intensities can probe the light-bead interaction beyond the linear regime. Here we measure the full non-linear force and displacement response of an optical trap in two dimensions using a dual-beam optical trap setup. We observe a stiffening of the trap beyond the linear regime that depends on bead size, in agreement with Mie theory calculations. We also find that the linear range for inferring forces from a back-focal-plane voltage detector signal is much larger than for inferring bead displacements from the same signal. Our approach thus allows for a complete two-dimensional characterization of the force response of an optical trap.