Fig. 1.

Platforms for the study of DNA CT. In solution (top), donor and acceptor molecules are covalently tethered or otherwise incorporated into opposite ends of a DNA duplex. DNA CT is initiated by photoexcitation of the donor and measured by spectroscopic or biochemical methods. On electrode surfaces (center), DNA is covalently tethered to the surface by one end and modified with a redox-active probe moiety on the distal end. An applied potential to the electrode results in DNA CT to the distal probe and produces a characteristic DNA-mediated redox signal. With single molecules (bottom), one DNA duplex is covalently attached by amide bonds across a gap that has been cut in a carbon nanotube within an electrical circuit. Current flow through the CNT-DNA device is a reflection of DNA CT through the single DNA duplex that bridges the gap and can be used to make fundamental measurements of DNA conductivity.