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SYAT: Symposium Anomalous Transport in Heterogeneous Media - from Porous Materials to Cellular Crowding

SYAT 1: Anomalous Transport in Heterogeneous Media I

SYAT 1.2: Hauptvortrag

Mittwoch, 24. März 2010, 15:00–15:30, H1

Distinguishing anomalous from simple diffusion in crowded solutions and in cells with fluorescence correlation spectroscopy — •Cecile Fradin, Daniel Banks, Shyemaa Shehata, Felix Wong, and Robert Peters — Dept. of Physics and Astronomy, McMaster University, Hamilton, Canada

The diffusion of proteins in cells is at the core of many important biological processes, in particular signal transduction and pattern formation. Yet, whether and why protein diffusion in cells may deviate from simple diffusion remains a matter of debate. One model often proposed to explain the experimental results is that this diffusion is anomalous, where the mean-squared displacement of the particles scales with time as ∼ t^α (instead of ∼ t for simple diffusion). It has often been suggested that anomalous diffusion could arise due to the crowding of the cellular environment. To test this hypothesis, we have performed variable length scale fluorescence correlation spectroscopy experiments, where the size of the detection area was varied, allowing to check whether the apparent diffusion coefficient varied with the scale of observation, a non-ambiguous indication of anomalous behavior. In cross-linked gels, we observed as expected that the diffusion of tracer particles was anomalous. In crowded polymer solutions and in live C. elegans embryos, on the other hand, and although single length scale fluorescence correlation spectroscopy experiments point to a strong anomalous behavior, variable length scale analysis failed to detect anomalous diffusion.