Continuing the rapid advance of structural DNA nanotechnology, just three months after the last announcement of an improved bipedal walking DNA nanorobot comes the announcement from another team of a yet more improved bipedal walking DNA nanorobot. Feynman Prize winner Nadrian C. Seeman and his colleagues have succeeded in coordinating the movements of the biped’s legs so that it can walk in one direction along a DNA track without the need of intervention at each step. The authors believe that the principles they have uncovered underlying unidirectional movement without intervention point toward nanotech devices that can perform useful mechanical work. From the press release from New York University, via AAAS EurekAlert “NYU, Harvard chemists create bipedal, autonomous DNA walker“:
Chemists at New York University and Harvard University have created a bipedal, autonomous DNA “walker” that can mimic a cell’s transportation system. The device, which marks a step toward more complex synthetic molecular motor systems, is described in the most recent issue of the journal Science [abstract]. For a video demonstration of the walker, go to http://www.nyu.edu/public.affairs/videos/qtime/biped_movie.mov.
Two fundamental components of life’s building blocks are DNA, which encodes instructions for making proteins, and motor proteins, such as kinesin, which are part of a cell’s transportation system. In nature, single strands of DNA—each containing four molecules, or bases, attached to backbone—self-assemble to form a double helix when their bases match up. Kinesin is a molecular motor that carries various cargoes from one place in the cell to another. Scientists have sought to re-create this capability by building DNA walkers.
Earlier versions of walkers, which move along a track of DNA, did not function autonomously, thereby requiring intervention at each step. A challenge these previous devices faced was coordinating the movement of the walker’s legs so they could move in a synchronized fashion without falling off the track.
To create a walker that could move on its own, the NYU and Harvard researchers employed two DNA “fuel strands” (purple and green in the above video). These fuel strands push the walker (blue) along a track of DNA, thereby allowing the walker and the fuel strands to function as a catalytic unit.
The forward progress of the system is driven by the fact that more base pairs are formed every step—a process that creates the energy necessary for movement. As the walker moves along the DNA track, it forms base pairs. Simultaneously, the fuel strands move the walker along by binding to the track and then releasing the walker’s legs, thereby allowing the walker to take “steps”.
In commenting on the above research in the same issue of Science, William Sherman points out that the first automated, unidirectional walker reported three months ago lacked a track that was rigid enough to generate linear motion, but this research adopted a strategy that allows the track to be “constructed from rigid, modular components that can easily be extended or incorporated into larger and more complex assemblies. (Credit: ScienceDaily)