Researchers have demonstrated that they can control how frequently a DNA-based nanodevice changes between two forms. Their "nanometronome" is the first example of such control over a single DNA molecule, the team contends.
The device consists of four strands of DNA, which in water assemble into a clover-shape structure. In the presence of magnesium ions, the assembly randomly switches between two stable, X-shaped forms, each with different strands paired into helices. The "ticking" rate between the two forms is mere milliseconds, the team reports.
To control the rate of ticking, Taekjip Ha of the University of Illinois at Urbana-Champaign and his colleagues added a short, overhanging DNA chain to one end of two of the strands. The two short chains complement each other. In the first DNA form, they can't reach each other. In the second DNA form, they are close together and so pair up. This stabilizes the form and lengthens the amount of time it keeps this shape, Ha says.