Direct measurement of electrical transport through single DNA molecules of complex sequence

Seemingly contradicting results raised a debate over the ability of DNA to transport charge and the nature of the conduction mechanisms through it. We developed an experimental approach for measuring current through DNA molecules, chemically connected on both ends to a metal substrate and to a gold nanoparticle, by using a conductive atomic force microscope. Many samples could be made because of the experimental approach adopted here, which enabled us to obtain reproducible results with various samples, conditions, and measurement methods. We present multileveled evidence for charge transport through 26-bp-long dsDNA of a complex sequence, characterized by S-shaped current-voltage curves that show currents > 220 nA at 2 V. This significant observation implies that a coherent or band transport mechanism takes over for bias potentials leading to high currents (> 1 nA).