Nanophotonics

Your body contains roughly 20,000 different kinds of proteins. Each one is a tiny machine that folds, twists, and flexes thousands of times per second to do its job: digesting food, firing neurons, fighting infections. When one of those machines jams or snaps into the wrong shape, you get disease. But for decades, watching a single protein change shape in real time has been like trying to film a hummingbird’s wings with a pinhole camera. The motions are too fast, the proteins are too small, and the measurement tools introduce too much noise.

Researchers at the University of Queensland just solved that problem. In a paper posted to arXiv on July 17, they describe a silicon-chip sensor that can track the shape changes of a single protein molecule at sub-microsecond speeds, continuously, for minutes at a time. No fluorescent dyes, no averaging over millions of molecules, no physical tether that might alter the protein’s behavior. The device is a nanoscale stethoscope pressed up against a single molecule, and it’s revealing things about protein motion that nobody had seen before.

In 1974, a group of scientists at Imperial College discovered that when you shine light on a rough silver surface, the molecules sitting on top of it scatter far more light than they should, about a million times more. That accidental finding, surface-enhanced Raman spectroscopy (SERS), gave chemists a superpower: the ability to identify individual molecules by the way they vibrate. A few years later, researchers found that infrared light, the kind your TV remote uses, could be similarly amplified on nanostructured surfaces. The catch? Nobody could get both techniques to work on the same device.