Disentangling Random Motion and Flow in a Complex Medium

We describe a technique for deconvolving the stochastic motion of particles from large-scale fluid flow in a dynamic environment such as that found in living cells. The method leverages the separation of timescales to subtract out the persistent component of motion from single-particle trajectories....

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Bibliographic Details
Published inBiophysical journal Vol. 110; no. 3; pp. 700 - 709
Main Authors Koslover, Elena F., Chan, Caleb K., Theriot, Julie A.
Format Journal Article
LanguageEnglish
Published United States Elsevier Inc 02.02.2016
Biophysical Society
The Biophysical Society
Subjects
Biological Transport
Brownian motion
Cell Biophysics
Cell Line
Cells
Cytoplasm
Cytoplasm - metabolism
Diffusion
Humans
Lysosomes - metabolism
Microfluidics - methods
Models, Theoretical
Motion
Stochastic models
Stochastic Processes
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Summary:We describe a technique for deconvolving the stochastic motion of particles from large-scale fluid flow in a dynamic environment such as that found in living cells. The method leverages the separation of timescales to subtract out the persistent component of motion from single-particle trajectories. The mean-squared displacement of the resulting trajectories is rescaled so as to enable robust extraction of the diffusion coefficient and subdiffusive scaling exponent of the stochastic motion. We demonstrate the applicability of the method for characterizing both diffusive and fractional Brownian motion overlaid by flow and analytically calculate the accuracy of the method in different parameter regimes. This technique is employed to analyze the motion of lysosomes in motile neutrophil-like cells, showing that the cytoplasm of these cells behaves as a viscous fluid at the timescales examined.
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ISSN:0006-3495
1542-0086
DOI:10.1016/j.bpj.2015.11.008