Identifying single bases in a DNA oligomer with electron tunnelling

It has been proposed that single molecules of DNA could be sequenced by measuring the physical properties of the bases as they pass through a nanopore 1 , 2 . Theoretical calculations suggest that electron tunnelling can identify bases in single-stranded DNA without enzymatic processing 3 , 4 , 5 , and it was recently experimentally shown that tunnelling can sense individual nucleotides 6 and nucleosides 7 . Here, we report that tunnelling electrodes functionalized with recognition reagents can identify a single base flanked by other bases in short DNA oligomers. The residence time of a single base in a recognition junction is on the order of a second, but pulling the DNA through the junction with a force of tens of piconewtons would yield reading speeds of tens of bases per second. Electrodes functionalized with recognition reagents can resolve and identify a single DNA base embedded in an oligomer.