Direct measurement of electrical transport through single DNA molecules

Abstract

The apparently contradictory results indicating the ability of DNA to transport charge as well as the possible charge transport mechanisms in DNA have been addressed by making scanning tunneling microscopy (STM) or current-sensing atomic force microscopy measurements using gold nanoparticle (GNP)-DNA complexes bound to a gold substrate designed to minimize nonreproducibility of the specific binding modes and configurations of the DNA-metal contacts. Using these GNP-DNA complexes but a different strand of DNA [13-base-pair poly(dA)-poly(dT) double-stranded DNA] and STM, semiconductorlike charge transport characteristics are demonstrated for DNA; importantly, several different observed I-V characteristics are correlated with different configurations of GNP-DNA complexes as well as with I-V characteristics calculated using a Landauer formalism. These joint measured and simulated I-V characteristics for the GNP-DNA complexes are consistent with charge transport in a semiconductor where the lowest unoccupied molecular orbital energy of the DNA serves as the lowest conduction band energy and the highest occupied molecular orbital energy of the DNA serves as the highest valence band energy.