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Issue 12, 2010
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Development of anomalous diffusion among crowding proteins

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Abstract

In cell membranes, proteins and lipids diffuse in a highly crowded and heterogeneous landscape, where aggregates and dense domains of proteins or lipids obstruct the path of diffusing molecules. In general, hindered motion gives rise to anomalous transport, though the nature of the onset of this behavior is still under debate and difficult to investigate experimentally. Here, we present a systematic study where proteins bound to supported lipid membranes diffuse freely in two dimensions, but are increasingly hindered by the presence of other like proteins. In our model system, the surface coverage of the protein avidin on the lipid bilayer is well controlled by varying the concentration of biotinylated lipid anchors. Using fluorescence correlation spectroscopy (FCS), we measure the time correlation function over long times and convert it to the mean-square displacement of the diffusing proteins. Our approach allows for high precision data and a clear distinction between anomalous and normal diffusion. It enables us to investigate the onset of anomalous diffusion, which takes place when the area coverage of membrane proteins increases beyond approximately 5%. This transition region exhibits pronounced spatial heterogeneities. Upon increasing the packing fraction further, transport becomes more and more anomalous, manifested in a decrease of the exponent of subdiffusion.

Graphical abstract: Development of anomalous diffusion among crowding proteins

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Publication details

The article was received on 23 Nov 2009, accepted on 18 Mar 2010 and first published on 07 May 2010


Article type: Paper
DOI: 10.1039/B924149C
Citation: Soft Matter, 2010,6, 2648-2656
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    Development of anomalous diffusion among crowding proteins

    M. R. Horton, F. Höfling, J. O. Rädler and T. Franosch, Soft Matter, 2010, 6, 2648
    DOI: 10.1039/B924149C

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