Super Resolution Microscopy

E. coli and Shigella sp. bacteria
Fluorescence confocal light micrograph of E. coli and Shigella sp. bacteria (blue) in human cell (green) Credit: Stephanie Schuller/Science Source
Fluorescent micrograph of human insulin producing beta cells  Credit:  Doug Melton/Harvard University.  Photo by B.D. Colen
Fluorescent micrograph of human insulin producing beta cells Credit: Doug Melton/Harvard University. Photo by B.D. Colen

It used to be fact, and even children at school were taught one basic principle of light microscopy: it’s impossible to see things that are smaller than 200 nanometers – that is, a 200 millionth of a millimeter. This was called the diffraction limit. So you might be able to see the shapes of very large bacteria or human cells under your microscope, but you won’t be able to see smaller structures inside of these cells or viruses and certainly no single molecules. This year three new Nobel Laureates in Chemistry – William E. Moerner, Stefan W. Hell and Eric Betzig – have turned it all on its head with the development of super-resolved fluorescence microscopy.

Stefan Hell developed a special method which makes use of two laser beams. One stimulates fluorescent molecules to glow. A second laser beam, though, cancels out any glow caused by the first beam – except for that in a nanometer-sized volume. This way, he yielded images with a resolution much better than conventional confocal light microscopes. He called the new microscopy STED – stimulated emission depletion microscopy.

Working separately Moerner and Betzig, using the same concept of fluorescence and turning individual molecules on and off with laser beam pulses, made it possible to see single molecules only one nanometer big under a microscope.

This image demonstrates the difference in resolution of confocal and STED microscopy. It shows proteins of the nucleus, labeled with fluorescent dyes, imaged with a STED microscope.
This image demonstrates the difference in resolution of confocal and STED microscopy. It shows proteins of the nucleus, labeled with fluorescent dyes, imaged with a STED microscope.
Difference between confocual and super resolution view of a human cell.  Credit:  Dr. Dr. Kandasamy Biomedical Microscopy Core University of Georgia.
Difference between confocual and super resolution view of a human cell. Credit: Dr. Dr. Kandasamy Biomedical Microscopy Core University of Georgia.

Since this technology can be used with living cells it will be an invaluable resource when studying HIV or to observe how living cancer cells react to certain cancer drugs. Biologists will even be able to study nerve synapses and the interaction between viruses and cells. This will be a rapidly expanding field in many, many branches of science.

Super-resolution image of a living neuron captured on STED reveals dendritic spines in unprecedented detail.  Photo by Stefen Hell from the Max Planck Institute on Biophysical Chemistry.
Super-resolution image of a living neuron captured on STED reveals dendritic spines in unprecedented detail. Photo by Stefen Hell from the Max Planck Institute on Biophysical Chemistry.
Protein network in a mammalian cell captured with STED Photo from Max Planck Institute of Biophysical Chemistry
Protein network in a mammalian cell captured with STED Photo from Max Planck Institute of Biophysical Chemistry

To watch a video on the STED microscope produced by the Max Planck Institute click below.

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