Bursts of Active Transport in Living Cells

We scrutinize the temporally-resolved speed of active cargo transport in living cells, and show intermittent bursting motions. These nonlinear fluctuations follow a scaling law over several decades of time and space, the statistical regularities displaying a time-averaged shape that we interpret to reflect stress buildup followed by rapid release. The power law of scaling is the same as seen in driven jammed colloids, granular, and magnetic systems. The implied regulation of active transport with environmental obstruction extends the classical notion of molecular crowding.