Regensburg 2010 – wissenschaftliches Programm

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

SYAT 2: Anomalous Transport in Heterogeneous Media II

SYAT 2.1: Hauptvortrag

Mittwoch, 24. März 2010, 16:30–17:00, H1

The Lorentz model: a paradigm of anomalous transport — •Felix Höfling — Rudolf Peierls Centre f. Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP, United Kingdom

Transport in spatially heterogeneous materials such as rocks, soils, gels, and ceramics is strongly hindered and often anomalously slow. Subdiffusive motion is found further in cell membranes and in the cytoplasm, which are densely packed with differently sized proteins, lipids, and sugars, summarised as macromolecular crowding.

The Lorentz model provides a simplistic model for transport in a spatially heterogeneous medium, the latter being represented by randomly distributed obstacles. Slow dynamics and anomalous transport emerge generically over the full range of packing fractions. A localisation transition induces subdiffusive motion, which is observed over many decades in time close to the critical point. The dynamics is rationalised in terms of a cluster-resolved scaling theory and characterised by a set of universal exponents.

A two-dimensional version of the Lorentz model is motivated by the subdiffusive motion of membrane proteins, which can be measured with fluorescence correlation spectroscopy (FCS). Based on FCS experiments in silico, it is shown that varying the beam waist of the illuminating laser reveals the intricate interplay of the heterogeneous medium and the anomalous transport. Going beyond the common assumption of spatially Gaussian transport, the analogy of FCS to other dynamic scattering methods is highlighted, establishing its potential of resolving complex dynamics in both space and time.