Tiny machines need tiny motors. Now, researchers have designed an on-off switch for a motor made from a spinning protein fragment just 11 nanometers wide.
A motor such as this one, based on a natural protein, might someday operate nanoscale machines such as drug-delivery systems, says Carlo Montemagno of the University of California, Los Angeles. He and his colleagues describe their controllable minimotor in the November Nature Materials.
The protein that Montemagno and his colleagues used is an enzyme ATP synthase, which produces the cellular fuel adenosine triphosphate. The researchers worked specifically with a spinning fragment of ATP synthase called F1-ATPase.
Many researchers have been looking at this protein fragment and other spinning proteins with an eye toward using them as motors in future nanoscale machines. Two years ago, Montemagno’s team reported that they had attached small nickel and protein propellers to F1-ATPase hubs that rotate about 8 times per second.
Yet to work in a functioning machine, a motor must be able to turn on and off. In the new work, Montemagno and his coworkers added a zinc-binding site to F1-ATPase. When the researchers then added zinc to a solution containing the modified protein fragment, it stopped rotating. They could restart the F1-ATPase spinning by removing the zinc with the help of molecules that bind to the metal even more strongly than the protein fragment does.
In contrast, unmodified F1-ATPase did not stop rotating with the addition of zinc.
The binding of zinc to the researchers’ modified protein fragment switches off spinning because “it’s like sticking a piece of glue in there,” says Montemagno. In other words, the zinc jams up the moving parts.
The switchable minimotor is “taking advantage of a biological system to control mechanical motion,” comments James Tour of Rice University in Houston. “To be able to stop it and turn it back on is really an important thing to do.”
There’s a long way to go before the nanoswitch can be controlled over numerous cycles of zinc addition and removal, adds Tour, “but it’s a step in the right direction . . . . It’s a very clever, clever approach.”
Any nanotech product eventually developed from this work won’t necessarily use F1-ATPase, says Montemagno, who’s working on several nanoscale devices. But the protein fragment is a good experimental model for nature-inspired motors, he says.
The work by Montemagno and his coworkers is bringing closer to reality some ideas of nanotechnology champions, says Peter Satir of the Albert Einstein College of Medicine in New York. On that dream list are cell-repair machines and membranes with nanoscale motors that segregate specific molecules.
Says Satir, “I think you’re on your way to engineering these machines that other people have only really dreamt of.”
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