IN MOTION-CAPTURE technology, actors are tagged with markers and videoed, allowing their movements to be transferred to lifelike digital creatures such as Gollum in The Lord of the Rings. Individual strands of DNA or proteins could get tagged up too, and their complex motion tracked in three dimensions.
This may be possible thanks to a device designed by Na Liu at the University of California, Berkeley, and colleagues. It is made up of five gold bars, each a few hundred nanometres long and arranged in the shape of a 3D letter H: four of the bars sit parallel to one another to form a rectangular cage, while the fifth lies crossways inside it.
In each bar, electrons vibrate at a natural frequency. Put the bars in this arrangement and these vibrations, known as plasmons, combine to form two sharp resonances that vary depending on the position of the central bar relative to the cage (Science, ).
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Liu鈥檚 team suggests attaching each bar to a different point on a 3D molecule. As the molecule interacts with an enzyme, or folds up, the distances between the rods will change, producing a series of plasmon resonances that can be measured to reveal the molecule鈥檚 motion in three dimensions.