Researchers at the Massachusetts Institute of Technology have recently developed a novel approach to overcome problems encountered inside a living cell.
As specified in a Phys.org report, inside a living cell, proteins and other molecules are frequently tightly packed together.
Microscopy technique reveals hidden nanostructures in cells and tissues @MIT @natBME https://t.co/0oOIkvMc6E
— Phys.org (@physorg_com) August 29, 2022
Such dense clusters can be challenging to image as the fluorescent labels used to make them visible cannot wedge themselves in between the molecules.
To overcome the limitations, MIT researchers have developed an approach to deal with the limitation to make the "invisible" molecules visible.
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Nanoscopy of Living Cells
'De-Crowding' Molecules
This new technique enables the study investigators to "de-crowd" the molecules by expanding a tissue or cell sample before labeling the molecules, making the latter mentioned more accessible to fluorescent tags.
Such an approach, which builds on a widely utilized approach known as expansion microscopy, previously developed at MIT, needs to allow scientists to visualize molecules and cellular structures that have never been seen in the past.
According to the Y. Eva Tan Professor Edward Boyden, also a professor of biological engineering and brain and cognitive sciences at MIT, it is clear that the expansion process will reveal a lot of new biological discoveries.
Using This technique, Boyden and his colleagues showed that they could image a nanostructure in the neurons' synapses.
They imaged, too, the structure of Alzheimer's-linked amyloid beta plaques in greater detail than has been plausible previously.
Describing the new method introduced in their study published in the Nature Biomedical Engineering journal, assistant professor Deblina Sarkar, from the Media Lab and one of the study's lead authors, said their technology, "which we named expansion revealing," allows visualization of such nanostructures, which stayed hidden before, using hardware easily available in academic laboratories.
Imaging Protein
Imaging a particular protein or other molecules inside a cell necessitates labeling it with a fluorescent tag carried by an antibody binding to the target.
Essentially, antibodies are roughly 10 nanometers in length, whereas typical cellular proteins are usually roughly two to five nanometers in diameter, and thus, if the target proteins are quite densely packed, the antibodies cannot go to them.
This has been a hindrance to traditional imaging and the original version of expansion microscopy, as well, first developed by Boyden in 2015.
In the expansion microscopy's original version, the study authors attached fluorescent labels to molecules of interest prior to the expansion of the tissues.
The labeling was initially done partly because the researchers needed an enzyme to chop proteins in the sample so the tissue could be expanded. This means the proteins could not be labeled following the expansion of the tissue.
Amyloid Beta Forming in Periodic Nanoclusters Discovered
The study investigators used their new technique to image beta-amyloid, a peptide forming plaques in the brains of Alzheimer's patients.
Using brain tissue from mice, the researchers discovered that amyloid beta is forming periodic nanoclusters, which had not been seen before.
Such clusters of amyloid beta also comprise potassium channels. The MIT report said that the authors also discovered amyloid beta molecules that formed helical structures along axons.
Related information about profiling cells in nanostructured materials is shown on the Department of Bioengineering's YouTube video below:
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