Accuracy of MSD-based transport coefficient estimates at finite observation times

Ascertain whether mean-squared-displacement-based estimates of the transport coefficient D(T) are accurate when transport measurements are conducted at finite lag times, given that MSD-based transport coefficients are defined in the limit of infinite time.

Background

The authors observe strong short-time, nanoscale correlations in lipid motion that differ from bulk long-time behavior. They caution that ensemble-averaged MSD, which is defined in the long-time limit, may hide local transport processes.

This raises the methodological question of whether MSD-based D(T) estimates remain accurate when applied to finite-time nanoscale measurements.