Mean-Squared Displacement (MSD) - Biophysics Query

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BuddingYeastMitosis's picture
Mean-Squared Displacement (MSD) - Biophysics Query


I'm a grad student at Berkeley studying microtubule binding proteins.

I'm going nuts trying to figure out whether you calculate the mean-squared displacement of a group of particles at time t by taking the average of the squares of their displacements at time t from their initial positions or by taking the average of the squares of their cumulative displacements at time t.

I hope someone understands what I mean.  For example, one particle may have moved a cumulative distance of 500 nm in one second, but it may end up only 10 nm from where it started. Would you take the square of 500 or the square of 10 then to calculate the MSD.

If possible, I would also appreciate a reference to a primary article, review, or textbook that verifies the information, as it would be useful to cite.  I have searched and searched, and I have not found a satisfactory answer.

Thanks for any help!!