microscopy
Overcoming the limits of optical microscopy When scientists in the 17th century studied living organisms under an optical microscope for the first time, a new world opened up before their eyes. This was the birth of microbiology, and ever since, the optical microscope has been one of the most important tools in the life-sciences toolbox. However, optical microscopy was limited by a physical restriction as to what size structures it was possible to resolve.
I
The development of superresolved fluorescence microscopy But Eric Betzig, Stefan W Hell and William E Moerner have found ways to circumvent Abbe’s limit. The equation still holds but, using molecular n 1873, the microscopist Ernst Abbe published
fluorescence, Betzig, Hell and Moerner independently
an equation demonstrating how microscope resolution
have overcome the limitation and have taken optical
is limited by, among other things, the wavelength of
microscopy into a new dimension. Theoretically there
the light. For the greater part of the 20th century,
is no longer any structure too small to be studied
this led scientists to believe that they would never be
and the optical microscope can now peer into the
able to observe things smaller than roughly half the
nanoworld.
wavelength of light, ie, 0.2 µm. This meant that while scientists could distinguish whole cells and some
How Abbe’s limit was circumvented
organelles, they would be unable to resolve things as
Stimulated emission depletion microscopy
small as a normal-sized virus or single proteins, or
Stimulated emission depletion (STED) microscopy was
to follow the interaction between individual protein
developed by Stefan Hell in 2000. Here, two laser beams
molecules in the cell.
are utilised; one stimulates fluorescent molecules to
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