Diffusive Motion in Cells

Hi, I had a question regarding superdiffusive and subdiffusive motion of particles. We know that inside the human cells, particles actively move towards a specific point. However, their displacement from the initial point to the final point is not completely active. Somewhere in the middle they diffuse around. Is there anyway to parse out that subdiffusive (and/or superdiffusive) motion from that trajectory? I appreciate all your help and thank you for taking the time out to answer this question.
- Abdullah Chaudhary (age 28)
Montreal, Quebec, Canada

Tough question! There are various ways to track diffusive motions. One is to use fluorescent labels, and watch the fluorescent cloud spread out with time.

For other readers, I should clarify that sub-diffusive means that particles start off diffusing, but their diffusion rates seem to slow down with time. This can happen if partcles rattle around more or less freely in a small region, but have to cross bigger barriers to get farther away, with the typical barrier height growing with distance. Super-diffusive means that the long-time motion is larger than you would expect based on short-time diffusion. Both types are briefly discussed, with references to experiments, here: 
https://en.wikipedia.org/wiki/Anomalous_diffusion
https://en.wikipedia.org/wiki/Anomalous_diffusion.

Here's a nice biological example, along the lines you're asking about:
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.103.018102
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.103.018102

Mike W.

 

 

(published on 12/09/2018)