Interaction prolonged DNA translocation through solid-state nanopores.

An interesting smooth blocked nanopore and corresponding "current ladder" phenomenon was observed in DNA translocation experiments through solid-state nanopores. The ionic current shows several drop steps (current levels in the current ladder) with an identical drop interval, which corresponds to an individual unfolded DNA translocation event. This indicates that multiple anchored DNA molecules have one end inside the nanopore to cause such a current ladder. On each current level, normal DNA translocation events were detected. The event duration time increases as the level number increases, which means DNA translocates more slowly when more DNA molecules are inside the nanopore due to DNA-DNA interactions. The Langevin dynamic model was used to explain the experimental observations. This finding strongly suggests that DNA-DNA interactions greatly impact the translocation dynamics when DNA passes through the nanopores.