Berlin 2012 – scientific programme

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BP: Fachverband Biologische Physik

BP 26: Posters: Membranes and Vesicles

BP 26.14: Poster

Thursday, March 29, 2012, 17:30–19:30, Poster A

Measuring particle fluctuations near cell membranes — •Felix Jünger and Alexander Rohrbach — Lab for Bio- and Nano-Photonics, University of Freiburg, Georges-Köhler-Allee 102, 79110 Freiburg, Germany

Thermal fluctuations are omnipresent in the world of living cells and are mainly determined by elastic and viscous forces. It is well known that the viscous drag γ increases when a particle approaches a stiff wall, but is unclear, whether this is still true close to a lipid bilayer or close to a living cell. In our work we investigate how the viscous drag changes when a spherical particle approaches a biological cell and to what extent a cell can vary the bead’s temporal thermal fluctuations and the viscous drag γ in its extra-cellular space. We use photonic force microscopy (PFM) to investigate the fluctuations of an optically trapped bead, which is approached to a cell membrane. The motion of the bead is tracked interferometrically in three dimensions with nanometer precision and on a microsecond time scale. The viscous modulus G″(ω,d), but also the elastic modulus G′(ω,d) as a function of the particle distance d to the cell surface can be obtained by analyzing the fluctuation data on a broad spectral bandwidth ω. We have measured several bead-cell arrangements and present first results.