Nobel Prize/Chemistry

Microscopy to nanoscopy

Print edition : November 28, 2014

Eric Betzig. Photo: MICHAELA REHLE/REUTERS

Stefan Hell. Photo: Hubert Jelinek/AP

William Moerner. Photo: Demetrio Araujo/AP

The Diffraction limit on optical microscopy meant that scientists could distinguish whole cells as well as some parts of the cell called organelles. However, they would never be able to discern something as small as a normal-sized virus or single proteins.

(A) The Intensity distribution, called the Airy pattern, of a single fluorophore emitting light onto a CCD camera. The fluorophore is at the centre of the image and can be considered a point source. For a green fluorescent protein (GFP) emitting at a peak of 510 nm, and an objective numerical aperture of 1.4, the width of this intensity profile will be 444 nm. Thus, a point source (the fluorescent protein) is no longer viewed as a point source, but rather as a diffuse, delocalised intensity pattern. (b) The profile of this two-dimensional pattern along the green line.

To the left, an E. coli bacterium imaged using conventional microscopy; to the right, the same bacterium imaged using STED. The resolution of the STED image is three times better. Image from Proc. Natl. Acad. Sci. USA 97: 8206–8210

The centre image shows lysosome membranes. To the left, the same image taken using conventional microscopy. To the right, the image of the membranes has been enlarged. The scale division of 0.2 micrometre is equivalent to Abbe’s diffraction limit. The resolution is many times improved. Image from Science 313:1642–1645.

The Nobel Prize-winning works of Eric Betzig, Stefan W. Hell and William E. Moerner fall under what has come to be called “super-resolution microscopy”, an umbrella term for a number of techniques that achieve sub-diffraction resolution. Theoretically, there is no limit to the resolution that their methods can achieve.
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