Enhanced diffusion in active intracellular transport

We show that within a living eukaryotic cell, mean square displacement of a n engulfed microsphere shows enhanced diffusion scaling as t(3/2) at short times, with a clear crossover to subdiffusive or ordinary diffusion scaling at longer times. The motion, observed nearby the nucleus, is due to intera ctions with microtubule-associated motor proteins rather than thermal Brown ian motion. We propose that time-dependent friction introduced by the intra cellular polymer networks leads to sub-ballistic motion, analogous to subdi ffusion observed in passive networks of semiflexible biopolymers.