With DNA's ability to store the very blueprint of life, it may seem mundane to use it as an ordinary pair of tweezers. But a report in the 10 August issue of Nature describes how strands of DNA can be programmed to cyclically open and close, creating a minuscule device that can do mechanical work.
This is not the first time DNA has been recruited for new tasks at the molecular level. Some researchers have manipulated DNA strands to carry out computations (ScienceNOW, 16 February). Now another team of scientists is betting that DNA can also help build a whole new generation of components, such as integrated circuits and switches, that are hundreds of times smaller than the current leaders of chip technology.
To create the tweezers, Bernard Yurke, of Lucent Technologies' Bell Labs, and Andrew Turberfield, of the University of Oxford in the United Kingdom, assembled three strands of DNA into a V shape. One of these strands is bent, and it bonds with part of each of the other two strands, making two relatively stiff arms.
The researchers could pinch the tweezers shut by adding a fourth strand. This bent strand is the exact complement of the DNA dangling off the ends of the V. When the fourth strand bonds with both of these dangling ends, the two sides of the V are drawn together. To reopen them, the researchers added a stretch of DNA that binds even tighter to the fuel strand, breaking it away from the tweezers, which then spring open. How do they know it's working? Because there are two fluorescent markers at the V tips, one of which absorbs part of the other one's light when it's at close range. Thus, the tweezers glow brighter when open than when closed.
Yurke says the study shows that DNA could be used as an "intelligent glue" that could pick up components from a jumbled mass and assemble them. New York University chemist Ned Seeman, a pioneer in DNA nanotechnology, says the power of the method is that by changing the base pair sequence, researchers can make different tweezers that are closed by specific fuel strands. In theory, you could control each pair of DNA tweezers individually. "That, in my opinion, is a significant advance," he says.