Locality of entangled polymer dynamics

A combination of sparse and full fluorescence labeling of entangled actin solutions (filaments about 15 $\mu $m long at 1 mg/ml concentration) allowed us to probe both filament-scale polymer dynamics and effectively monomer dynamics. On the filament scale, the reptation tube idea of classical polymer physics works well. However, on a local scale comparable to mesh size, local tube width fluctuation becomes important. For the first time, the dependence of longitudinal diffusion on local tube width was quantified.