IY Wong, ML Gardel, DR Reichman, ER Weeks, MT Valentine, AR Bausch, DA Weitz, Phys. Rev. Lett.

We study the thermal motion of colloidal tracer particles in entangled actin filament (F-actin) networks, where the particle radius is comparable to the mesh size of the F-actin network. In this regime, the ensemble-averaged mean-squared displacement of the particles is proportional to tau^gamma where 0 < gamma < 1 from 0.1 < tau < 100 sec and depends only on the ratio of the probe radius to mesh size. By directly imaging hundreds of particles over 20 minutes, we determine this anomalous subdiffusion is due to the dynamics of infrequent and large jumps particles make between distinct pores in the network.