A localized transition in the size variation of circular DNA in nanofluidic slitlike confinement

We report strong evidence for a localized transition in the size variation of circular DNA between strong and moderate regimes of slitlike confinement. A novel and rigorous statistical analysis was applied to our recent experimental measurements of DNA size for linear and circular topologies in nanofluidic slits with depths around ≈ 2p, where p is the persistence length. This empirical approach revealed a localized transition between confinement regimes for circular DNA at a slit depth of ≈ 3p but neither detected nor ruled out the possibility for such a transition for linear DNA. These unexpected results provide the first indication of the localized influence of polymertopology on size variation in slitlike confinement. Improved understanding of differences in polymer behavior related to topology in this controversial and relevant system is of fundamental importance in polymer science and will inform nanofluidic methods for biopolymeranalysis.