Berlin 2015 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 20: Membranes and vesicles I (joint session BP, CPP)

CPP 20.9: Talk

Tuesday, March 17, 2015, 12:00–12:15, H 1028

Local viscosities near plasma membranes of living cells — •Felix Jünger and Alexander Rohrbach — Lab for Bio- and Nano-Photonics, University of Freiburg, Georges-Koehler-Allee 102, 79110 Freiburg, Germany

The molecular processes of particle binding and endocytosis are influenced by the locally changing mobility of the particle nearby the plasma membrane of a living cell. Close to different cellular interfaces, the viscous drag γ changes strongly with the distance to the interface. 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.