Imaging experts awarded Nobel Prize for Chemistry

Long thought to be impossible, imaging at such high resolution has allowed researchers to watch diseases taking hold in living cells, making possible huge strides in the development of new treatments.

Optical microscopy has long been thought limited because it was not possible to obtain clear images of anything smaller than half the wavelength of light, that is around 0.2micrometres. Although individual cells could be seen, the structures within them and even large protein molecules could not; viruses were also below this limit, which is knows as the Abbé Limit after microscopist Ernst Abbé, who came up with it in 1873.

The first of the Nobel breakthroughs came from Prof Stefan Hell, a German microscopist working at Turku in Finland. Using a technique called stimulated emission, Hell devised a way to use lasers to both induce and quench — switch on and off — fluorescence in antibodies which could be coupled to DNA. Hell’s technique, called stimulated emission depletion, uses a laser beam with a nanoscale diameter to induce fluorescence, which is surrounded by a wider, ring-shaped quenching beam. Both beams scan over the sample, with the narrow central beam acting like a torch, illuminating a tiny fraction of the sample at any one time. The microscope’s processors combines the images from the scan with positional information of where the laser probe was when the image was obtained to give a combined image whose resolution matches the width of the inducing beam. Hell perfected the technique at the University of Göttingen in 2000.