Nature's tiniest rotor runs like clockwork.

With amazing efficiency, cells synthesize and store energy in the form of adenosine triphosphate, ATP for short. Bioengineers often regard the enzyme that makes this chemical energy as the ultimate molecular machine.

Hiroyasu Itoh at Hamamatsu Photonics in Tsukuba, Japan, and his colleagues have found a way to use the same enzyme, ATP synthase, to power nanoscale devices.

Embedded in the cell membrane, the enzyme is made of two protein units joined by a central rotor. Instead of using the entire enzyme, the researchers isolated the protein unit that binds to ATP, along with the rotor, and attached hundreds of these complexes to a glass surface. The researchers attached a magnetic bead to each rotor then and used electromagnets to induce the rotors to spin.

When rotating clockwise, the nanomachines churned out ATP from ingredients in a solution surrounding the devices. During counterclockwise rotations, the nanomachines consumed ATP. The researchers describe their results in the Jan. 29 Nature.

In the past, researchers have used ATP synthase to make structures that convert ATP into mechanical motion (SN: 11/9/02, p. 291). The new work shows that it's possible to reverse the process and generate chemical energy instead.

--A.G