Probing DNA conductivity with photoinduced electron transfer and scanning tunneling microscopy

The possibility that the stacked DNA bases can mediate vectorial electron transfer has been examined using two different approaches. Experiments on photoinduced electron transfer with intercalated donors and acceptors (either randomly bound or linked dyads of ruthenium complex and viologen) indicate that while DNA may be a better medium than acetonitrile for electron transfer over short distances (2-3-base pair, equivalent to 10-14Å centre-to-centre separation), it is a poor medium for transport over larger separations. Attempts to measure conductivity of individual DNA molecules using scanning tunneling microscopy to image mixed monolayers of mercaptohexanol (MCH) and 30-mer or 10-mer DNAs with alkanethiol linkers also indicate that DNA in its native state is a poor conductor. AFM images of the DNA/MCH mixed monolayers show that the DNA molecules extend vertically upward from the surface in such surface architectures.