We report double-strand DNA translocation experiments using silicon oxide nanopores with a diameter of about $10\mathrm{nm}$. By monitoring the conductance of a voltage-biased pore, we detect molecules with a length ranging from 6557 to 48 500 base pairs. We find that the molecules can pass the pore both in a straight linear fashion and in a folded state. Experiments on circular DNA further support this picture. We sort the molecular events according to their folding state and estimate the folding position. As a proof-of-principle experiment, we show that a nanopore can be used to distinguish the lengths of DNA fragments present in a mixture. These experiments pave the way for quantitative analytical techniques with solid-state nanopores.

• Received 16 August 2004

DOI:https://doi.org/10.1103/PhysRevE.71.051903