Self-Diffusion of an Entangled DNA Molecule by Reptation

Diffusion coefficients ($D$) of fluorescently labeled DNA molecules in entangled DNA solutions were measured by tracking Brownian motion. The measured lifetime of tubelike topological constraints that hinder diffusion was longer than the minimum lifetime assumed in the reptation theory. The scaling of $D$ with polymer length and concentration was close to reptation predictions for the highest concentration and longest chain studied. These observations illustrate reptation at the microscopic level.