Diffusion of circular DNA in two-dimensional cavity arrays.

Through a two-dimensional cavity array with connecting pores of submolecular size, diffusion of relaxed circular and linear DNA molecules is visualized by fluorescence microscopy. Across the entropic barriers transport regime, associated with spatially heterogeneous confinement of flexible polymers, circular DNA diffuses slower than linear DNA of the same length, a trend indicating that linear DNA preferably moves through connecting pores by the threading of an end rather than the looping of a midsection.