Berlin 2008 – scientific programme
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BP: Fachverband Biologische Physik
BP 9: Membranes and Interfaces
BP 9.6: Talk
Tuesday, February 26, 2008, 12:00–12:15, PC 203
Fluorescence correlation spectroscopy measurement of anomalous diffusion and crowding of lipid-bound proteins — •Margaret Horton1, Felix Höfling1,2, Joachim Rädler1, and Thomas Franosch1,2 — 1Center for Nanoscience, Ludwigs-Maximilians-Universität, München, Germany — 2Arnold Sommerfeld Center for Theoretical Physics, Ludwigs-Maximilians-Universität, München, Germany
In cell membranes, proteins and lipids diffuse in a highly heterogeneous landscape. Aggregates and dense domains of proteins or lipids can modify the path of diffusing molecules, giving rise to anomalous transport. We study two-dimensional diffusion in membranes that are heterogeneous due to protein crowding. Using fluorescence correlation spectroscopy (FCS), we measure the diffusion of the protein avidin bound to biotinylated lipids in a supported bilayer. The density of avidin is controlled by varying the concentration of the lipid anchors. A clear distinction between anomalous and normal diffusion can be achieved with long measurement times (200s) and analysis of the mean squared displacement (MSD). This approach offers an alternative to standard methods of fitting autocorrelated FCS data to probe the dynamic arrangement of molecules in heterogeneous membranes. At low protein surface coverage, normal diffusion is observed. As more protein covers the membrane, there is a transition to anomalous diffusion that becomes more anomalous as the membrane becomes more crowded. These results suggest mechanisms by which cell membrane-associated molecules remain mobile in crowded environments.