Dresden 2014 – scientific programme

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BP: Fachverband Biologische Physik

BP 4: Membranes and Vesicles I

BP 4.2: Talk

Monday, March 31, 2014, 15:30–15:45, HÜL 386

Measuring local viscosities near membranes of living cells with photonic force microscopy — •Felix Jünger and Alexander Rohrbach — Lab for Bio- and Nano-Photonics, University of Freiburg, Georges-Koehler-Allee 102, 79110 Freiburg, Germany

The diffusive motion of a particle in the vicinity of a boundary surface is relevant from a biological point of view, since the viscous drag γ changes significantly with the distance to the interface, e.g. a cell membrane. In our work we use photonic force microscopy (PFM) to investigate how γ changes when an optically trapped 1µm polystyrene bead approaches the plasma membrane of different biological cells. The bead’s temporal fluctuations are tracked interferometrically in three dimensions with nanometer precision and on a microsecond time scale. The autocorrelation of the bead’s motion reveals the friction coefficient γ(d) as a function of bead-membrane distance d.

We find a simple exponential decay for γ(d) with a hydrodynamic decay length Λ(d) that fits well to the obtained experimental data. We investigated different cell types (J774, HT29, MDCK) and a giant unilamellar vesicle (GUV). We find that all values Λ(d) measured at biological membranes are significantly longer than those of a rigid glass coverslip, giving rise to the conclusion that the deformable shape of the membrane influences the hydrodynamic interaction.