NATURE鈥橲 smallest rotary motor has finally been coaxed into producing chemical energy in the lab. The experiment paves the way for molecular motors that might power future nanodevices.
Cells synthesise energy-carrying ATP molecules using an enzyme called ATP synthase. Part of the enzyme is a 鈥渕otor鈥� that is turned clockwise by electrochemical gradients within the cell, forcing the production of ATP. It also works in reverse, rotating anticlockwise to break down ATP and release energy.
To run this ATP machine artificially, Hiroyasu Itoh of Hamamatsu Photonics in Tsukuba, Japan, and his colleagues fixed the enzyme to a glass plate and attached a tiny magnetic bead to its rotor. When they added the necessary precursor molecules for ATP and switched on a rotating electromagnetic field, the bead and rotor started turning, and ATP was produced (Nature, vol 427, p 465).
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鈥淚t鈥檚 a very clever experiment,鈥� says Richard Cross, an expert on ATP synthesis at the State University of New York in Syracuse. He envisions attaching molecules of the amino acid cysteine to the enzyme鈥檚 rotor and stator, so that it could be turned on and off. Disulphide bonds between the cysteine molecules would lock the rotor in place, but introducing a reducing agent would break the bonds and let the motor spin. Adding an oxidising agent restores the bonds and stops the motor. 鈥淚f some device needed a little propeller, this is a propeller that could be turned on and off,鈥� says Cross.