ANOMALOUS DIFFUSION AND ERGODICITY IN LIVE CELLS
The plasma membrane is a crowded environment where proteins and lipids move in the presence of mobile and immobile obstacles. Furthermore, membrane components often interact with cytosolic elements. We are exploring the dynamics of the voltage gated potassium channels Kv2.1and Kv1.4 and sodium channels Nav1.6, using single-molecule tracking. By dually labeling channels with GFP and quantum dots (QD), we gather information on both the individual molecule trajectories and the distribution of proteins in the plasma membrane as an ensemble.
We analyze individual trajectories in terms of the time- and ensemble-averaged mean square displacements. Our results revealed that ion channels experience anomalous subdiffusion. We observe that the diffusion pattern is not ergodic in HEK cells and in hippocampal neurons, that is the ensemble and temporal distributions of displacements are different. Channel dynamics can be accurately modeled by the combination of a nonergodic continuous time random walk (CTRW) and an obstructed environment.
Diffusion at solid–liquid interfaces is crucial in many technological and biophysical processes. Although its behavior seems to be deceivingly simple, recent studies showing passive superdiffusive transport suggest that diffusion on surfaces may hide rich complexities. In particular, bulk-mediated diffusion occurs when molecules are transiently released from the surface to perform three-dimensional excursions into the liquid bulk. This phenomenon bears the dichotomy where a molecule always return to the surface but the mean jump length is infinite.
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Krzysztof Burnecki, Olve Peersen, Grzegorz Sikora, Mike Tamkun, Aleksander Weron
THIS PROJECT IS SUPPORTED BY THE NATIONAL SCIENCE FOUNDATION THROUGH GRANT 1401432.
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