Oct 26, 2007
Measuring charge transport in a single DNA molecule
Double-stranded (ds)DNA is the longest polymer in which electrical charge transport has been measured so far (which is not a 1D crystal like carbon nanotubes). It is a perfect candidate to investigate electric transport mechanisms in single molecules in a controlled way, as it enables a rich variety of structural manipulations (for example, sequence, length, mismatches) that are reflected in the transport properties (both energy level structure and coupling along the molecule). This knowledge is considered to be very relevant for both molecular nanoelectronics and DNA damage repair.
Despite intensive efforts in the nanoelectronics community, the charge transport measurements in dsDNA provided a variety of results. This variability originated from the application of different experimental and environmental conditions, and from the different number of molecules measured in parallel. We have, therefore, developed in the last few years a method to measure 10 nm long single dsDNA molecules that are chemically connected to a gold substrate and a gold nanoparticle at their opposite ends, in a controlled way using special scanning probe microscopy methods. These measurements showed that relatively high currents can be transported through single dsDNA molecules. These high currents suggest that the charge transport mechanisms that govern the charge transfer in donor-bridge-acceptor systems in solution can not naively account for the high currents that we measure. Faster mechanisms should be called for. The results were reported in PNAS, Faraday discussions† and recently in Nanotechnology.
Further measurements using this method are expected to yield more accurate and reliable information on the charge transport mechanisms in dsDNA that are extremely difficult to obtain by alternative measurement methods.
This work was performed at the Hebrew University by Hezy Cohen, Daniela Ullien and Claude Nogues, under the supervision of Danny Porath, in collaboration with the group of Ron Naaman at the Weizmann Institute.
The work was supported by EU projects DNA NANOWIRES (IST-2001-38951) and DNA NANODEVICES (FP6-029192) and by the German Israel Foundation grant number I-892-190.10/2005.
About the author
Danny Porath is a faculty member of the physical chemistry department and the Center for Nanoscience and Nanotechnology of the Hebrew University in Jerusalem, Israel. He is one of the pioneers of electrical transport measurements in single DNA molecules (Nature 403, 635 ) and of scanning tunnelling spectroscopy in DNA (Nature Materials, in press).