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AKB: Biologische Physik

AKB 27: Cell Mechanics II

AKB 27.1: Vortrag

Freitag, 31. März 2006, 11:30–11:45, ZEU 260

Investigating phagocytosis by optical tweezers-based microscopy — •Holger Kress¹, Ernst H.K. Stelzer¹, Gareth Griffiths¹, and Alexander Rohrbach² — ¹European Molecular Biology Laboratory (EMBL), Meyerhofstr. 1, 69117 Heidelberg, Germany — ²Institute of Microsystem Technology (IMTEK), University of Freiburg, Georges-Köhler-Allee 102, 79110 Freiburg, Germany

Phagocytosis is a central cellular mechanism in the innate mammalian immune system. When an invading bacterium binds to the membrane of a macrophage cell, the cell membrane starts to wrap around the invader and internalizes the bacterium. Thereby, the bacterium is enclosed into an intracellular membrane-organelle, the phagosome.

Coated latex beads are used as bacterial model systems to investigate phagocytosis by optical tweezers-based photonic force microscopy. The motion of an optically trapped bead is tracked interferometrically in 3D with nanometer precision at a microsecond timescale. Measuring the thermal fluctuations of a trapped bead during the binding to the cell membrane provides information about the dynamics of the binding process. Once the bead is bound to the cell, the motion of the bound bead reveals the mechanical cellular response to the binding event. Here the optical trap serves as a mechanical force transducer and also as an indicator of the cellular forces. After the bead is taken up by the cell, the phagosome is tracked in 3D during its intracellular transport. We found stepwise intracellular transport with a step size of about 36 nm indicating single molecular motor activity.