French scientists focus optical microscopes down to 30 nm

In fact, the French scientists are using two different imaging techniques to arrive at a resolution of 30 nm for their optical microscopes, according to the May 18, 2012 news item on Nanowerk.

Researchers from the Institut Pasteur and CNRS [Centre national de la recherche scientifique] have set up a new optical microscopy approach that combines two recent imaging techniques in order to visualize molecular assemblies without affecting their biological functions, at a resolution 10 times better than that of traditional microscopes. Using this approach, they were able to observe the AIDS virus and its capsids (containing the HIV genome) within cells at a scale of 30 nanometres, for the first time with light.

More specifically,

A study coordinated by Dr Christophe Zimmer (Institut Pasteur/CNRS), in collaboration with Dr Nathalie Arhel within the lab headed by Pr Pierre Charneau (Institut Pasteur/CNRS), shows that the association of two recent imaging techniques helps obtain unique images of molecular assemblies of HIV-1 capsids, with a resolution around 10 times better than that of traditional microscopes. This new approach, which uses super-resolution imaging and FlAsH labeling, does not affect the virus’ ability to self-replicate. It represents a major step forward in molecular biology studies, enabling the visualisation of microbial complexes at a scale of 30 nm without affecting their function.

The newly developed approach combines super-resolution PALM imaging and fluorescent FlAsH labeling. PALM imaging relies on the acquisition of thousands of low-resolution images, each of which showing only a few fluorescent molecules. The molecular positions are then calculated with high accuracy by computer programs and compiled into a single high-resolution image. FlAsH labeling involves the insertion of a 6-amino-acid peptide into the protein of interest. The binding of the FlAsH fluorophore to the peptide generates a fluorescent signal, thereby enabling the visualization of the protein. For the first time, researchers have combined these two methods in order to obtain high-resolution images of molecular structures in either fixed or living cells.

The researchers have supplied an image illustrating the difference between the conventional and new techniques will allow them to view (from the May 16, 2012 press release  [communiqué de presses] on the CNRS website),

© Institut Pasteur Reconstruction optique super-résolutive de la morphologie du VIH. L'image du dessous montre la distribution moyenne de l'enzyme intégrase observée par FlAsH-PALM. La résolution de cette technique (~30 nm) permet de retrouver la taille et la forme conique de la capside. Pour comparaison, la résolution de la microscopie conventionnelle (~200-300 nm), illustrée par l'image du dessus, ne permet pas une description détaillée de cette structure.

The conventional 200 – 300 nm resolution is shown at the top while the new 30 nm resolution achieved by combining the new techniques is shown below. This new technique has already allowed scientists to disprove a popular theory about the AIDS virus, from the May 18, 2012 news item on Nanowerk,

This new method has helped researchers visualise the AIDS Virus and localise its capsids in human cells, at a scale of 30 nm. Capsids are conical structures which contain the HIV genome. These structures must dismantle in order for the viral genome to integrate itself into the host cell’s genome. However, the timing of this disassembly has long been debated. According to a prevailing view, capsids disassemble right after infection of the host cell and, therefore, do not play an important role in the intracellular transport of the virus to the host cell’s nucleus. However, the results obtained by the researchers of the Institut Pasteur and CNRS indicate that numerous capsids remain unaltered until entry of the virus into the nucleus, confirming and strengthening earlier studies based on electron microscopy. Hence, capsids could play a more important role than commonly assumed in the replication cycle of HIV.

I gather excitement about this development is high as the scientists are suggesting that ‘microscopy’ could be known as ‘nanoscopy’ in the future.

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