A Simple and Powerful Analysis of Lateral Subdiffusion Using Single Particle Tracking

In biological membranes, many factors such as cytoskeleton, lipid composition, crowding, and molecular interactions deviate lateral diffusion from the expected random walks. These factors have different effects on diffusion but act simultaneously, so the observed diffusion is a complex mixture of di...

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Bibliographic Details
Published inBiophysical journal Vol. 113; no. 11; pp. 2452 - 2463
Main Authors Renner, Marianne, Wang, Lili, Levi, Sabine, Hennekinne, Laetitia, Triller, Antoine
Format Journal Article
LanguageEnglish
Published United States Elsevier Inc 05.12.2017
Biophysical Society
The Biophysical Society
Subjects
Animals
Biochemistry, Molecular Biology
Biological membranes
Biophysics
Cell Biophysics
Cell Membrane - metabolism
Cytoskeleton
Diffusion
Diffusion effects
Lateral diffusion
Life Sciences
Lipid composition
Lipids
Mathematical analysis
Membranes
Molecular interactions
Molecules
Neurons - cytology
Particle tracking
Random walk
Rats
Receptors
Scaffolding
Single Molecule Imaging
Synapses
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Summary:In biological membranes, many factors such as cytoskeleton, lipid composition, crowding, and molecular interactions deviate lateral diffusion from the expected random walks. These factors have different effects on diffusion but act simultaneously, so the observed diffusion is a complex mixture of diffusive behaviors (directed, Brownian, anomalous, or confined). Therefore, commonly used approaches to quantify diffusion based on averaging of the displacements such as the mean square displacement, are not adapted to the analysis of this heterogeneity. We introduce a parameter—the packing coefficient Pc, which gives an estimate of the degree of free movement that a molecule displays in a period of time independently of its global diffusivity. Applying this approach to two different situations (diffusion of a lipid probe and trapping of receptors at synapses), we show that Pc detected and localized temporary changes of diffusive behavior both in time and in space. More importantly, it allowed the detection of periods with very high confinement as well as their frequency and duration, and thus it can be used to calculate the effective kon and koff of scaffolding interactions such as those that immobilize receptors at synapses.
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ISSN:0006-3495
1542-0086
DOI:10.1016/j.bpj.2017.09.017