A controllable DNA switch has been developed by a team from Arizona State University to regulate the flow of electricity within a single, atomic-sized molecule. This discovery could advance the development of small, low cost electronic devices.

"It has been established that charge transport is possible in DNA, but for a useful device, one wants to be able to turn the charge transport on and off. We achieved this goal by chemically modifying DNA," said Professor Nongjian Tao.

"Not only that, but we can also adapt the modified DNA as a probe to measure reactions at the single-molecule level. This provides a way for studying important reactions implicated in disease, or photosynthesis reactions for novel renewable energy applications."

To accomplish this, the group modified one of DNA's double helix chemical letters with another chemical group, called anthraquinone (Aq). Anthraquinone is a three-ringed carbon structure that can be inserted in between DNA base pairs but contains a redox group.

The modified Aq-DNA helix could then help the chemical groups perform the switch and the molecule could reversibly gain or lose electrons.

When the researchers sandwiched the DNA between a pair of electrodes, they controlled their electrical field and measured the ability of the modified DNA to conduct electricity.

"We found the electron transport mechanism in the present anthraquinone-DNA system favours electron ‘hopping’ via anthraquinone and stacked DNA bases," said Tao.

In addition, they found they could reversibly control the conductance states to make the DNA switch on for high conductance or switch off for low conductance.