Make molecules visible with nanoscopy

Nanoscopy? Never heard. This is certainly due to the fact that these high-resolution microscopes are still a relatively recent development.

Microscopes are among the most groundbreaking inventions of modern times. Without these devices, numerous discoveries within biology would not have been possible. With the help of the first light microscopes developed by Dutch lensmakers at the end of the 16th century, the lenses of which were also greatly improved by the Dutch natural scientist Antoni Van Leeuwenhoek, unicellular organisms (so-called protozoa), but also bacteria, could be made visible and thus into the mysterious World of the microcosm. Technically speaking, microscopes do nothing more than break the light, which makes its way through an object, through the special arrangement of various lenses and thereby enlarge them. If you want to learn more about the physical principles of light microscopes, read  here  .

However, classic light microscopes are subject to physical limits with regard to optical  resolution  , the so-called Abbe limit. This limits the possible optical resolution of a classic light microscope. So if you want to perceive two points lying next to each other as individual points, they must not be closer together than half the wavelength of the light used. Since blue light with a wavelength of 400 nanometers (nm) represents the lowest limit of the light spectrum that we can perceive, the Abbe limit is therefore 200 nm.

Overcoming this limit would provide unexpected new knowledge from areas such as cell biology or chemistry, since it would then be possible to observe molecules in real time. This is exactly what researchers led by Prof. Dr. Stefan Hell from the Max Planck Institute for Biophysical Chemistry and his US colleagues Eric Betzig and William Moerner through the development of the STED microscope, for which they also received the Nobel Prize in Chemistry in 2014. Resolutions up to 20 nm and live images from inside a cell were now possible. This very informative video by the Max Planck Society illustrates how exactly fluorescence-based STED microscopy works.

In principle, very simple: if you want to observe certain molecules with high resolution, you first mark them with a fluorescent dye, which binds to this molecule and lights up in a certain color when irradiated with a laser. However, if the molecules are now very close to each other, they will of course all light up, which leads to a single light spot and you cannot see anything. The trick is now to snap out some of the molecules again and thus reduce the intensity of the remaining molecules and thus increase the resolution. This is achieved by a second, dog-shaped laser, that is, a laser that emits a ring and leaves the molecules in the middle of the laser untouched, that is, switched on. An ingenious principle.

Thanks to scientists like the ones mentioned above and many others who put their time into improving so-called nanoscopy, basic research experienced an enormous upswing. Since standstill is foreign to scientists, the development of nanoscopy also continued. With the MINFLUX system, in which Prof. Hell is also involved, the journey continues into the depths of the microcosm, now to an incredible  2.1 nm or 1.2 nm resolution.

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