DNA nanotech continues to improve the devices it produces as Oxford University scientists fix several shortcomings seen in earlier versions of bipedal DNA molecular walkers that had been produced by several laboratories. A succinct summary of the improvements in the new DNA nanobot is given by Jessica Griggs at NewScientist.com. From “Nanobot lets DNA legs do the walking“:

A TWO-legged molecular machine that can walk unaided along a single strand of DNA could one day shift cargo around nanofactories. That’s the promise of a walking molecular nanobot made by researchers at the University of Oxford.

Molecular engines that walk along strands of DNA are nothing new, but none has featured as many successful features as the Oxford team’s device. Unlike earlier attempts, their nanobot doesn’t wander aimlessly back and forth, fall off its track or destroy its track as it walks. The team have also devised an ingenious way of powering the nanobot that allows it to move freely.

The walker consists of two connected feet, each made of a short sequence of DNA bases that attach to a complementary sequence on the DNA track. However, the sequence of bases on the track is designed so that the feet have to compete for a foothold. That means that as one foot steps down, the other is forced to lift off.

The power for this process is supplied by molecules floating nearby, which react together to release energy as long as a specific catalyst is there. The clever part of the design is that the DNA feet themselves act as the catalyst when they lift off the track.

Richard Jones also gives a clear description of the accomplishments of the Oxford group on his Soft Machines blog, “A synthetic, DNA based molecular motor“, adding this useful comparison:

In this paper the authors don’t directly show the motor in action — rather, they demonstrate experimentally the presence of the various bound and unbound states. But this does allow them to make a good estimate of the forces that the motor can be expected to exert — a few picoNewtons, very much in the ball-park of the forces exerted by biological motors.

The research was published in Physical Review Letters (abstract). A Physical Review Focus piece by Sarah Webb, “Putting One Foot in Front of the Other“, provides a helpful description of the research and includes a very useful animation of how the new DNA walker functions. Also provided for a beautiful comparison with the protein molecular motors that make so much of the work of living cells possible are links to the spectacular “The Inner Life of the Cell animations”, which were noted here on Nanodot a couple years ago.
—Jim