Super-sharp video clip of the cell

Scientists in Göttingen film for the first time cellular life process on the nanoscale

February 29, 2008

For a long time, biologists have dreamed of observing life processes inside cells in real-time. However, to observe relevant details, scientists need a resolution on the nanoscale, which using a light microscope has not been achieved in living cells to date. Scientists at the Max Planck Institute for Biophysical Chemistry and the Cluster of Excellence "Microscopy at the Nanometer Range", which was established in line with the German Excellence Initiative of the University of Göttingen, have succeeded in shooting the first video ever of the inside of a living cell. Using the STED-microscope, the researchers followed the rapid movements of tiny cell building blocks with up to 28 images per second and with an up to four times better resolution compared to conventional light microscopes. For the first time, scientists could track in real-time how vesicles move within living nerve cells (Science Express, February 21th, 2008).

If one succeeds in following the life processes inside cells in close detail, it is then easy to understand what happens inside a living cell. But detailed observation has so far only been possible using electron- or scanning probe microscopes. However, these techniques do not allow views inside living cells. In contrast, lens-based optical microscopy allows non-invasive investigations but the images are not sharp enough. The light microscopy method suffers from a critical disadvantage, namely their diffraction-imposed resolution, which is limited at best to 200 nm. This diffraction barrier seemed for a long time to be an insurmountable obstacle. With his newly developed "Stimulated Emission Depletion" (STED) microscope, Stefan W. Hell, director at the Max Planck Institute for Biophysical Chemistry, could dramatically increase the resolution in fluorescence microscopy and therefore allowed light microscopy with resolution on the nanoscale. Stefan Hell and co-workers have already successfully used the STED microscope to observe single protein complexes separated only 20 to 50 nanometres from each other - structures, which are more than 1000 times smaller than a human hair. But in almost all of these snap-shots, the cells were chemically arrested - and therefore "frozen" in their physiological processes. The long exposure time required for a single image did not allow the recording of movements.

By developing special fast recording techniques for the STED microscopy, the physicists Volker Westphal, Marcel Lauterbach and Stefan Hell, in cooperation with the biologists Reinhard Jahn as well as Silvio Rizzoli from the Cluster of Excellence "Microscopy at the Nanometer Range" succeeded in recording fast movements within living cells. They reduced the exposure time for single images in such a dramatic way that they could film the movements within living nerve cells with a resolution of 65 to 70 nanometres - a 3 to 4 times better resolution compared to conventional light microscopes - in real-time.

The scientists involved in this project at the STED-microscope used for the first video of the inside of a living cell on the nanoscale and in real-time. Dirk Kamin, Volker Westphal, Silvio Rizzoli, and Marcel Lauterbach (from left to right). In the background: Reinhard Jahn (left) and Stefan W. Hell.
The STED microscope (right) with an up-to 4-fold higher resolution in contrast to the confocal microscope (left) allows tracking vesicles separately from each other. Arrows indicate further movements of the vesicles in successive images. The exposure time for a single image is 35 milliseconds.

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