Bacteria will help: Proteins, nanoparticles and quantum dots

A particle of gold in the cavity of chaperonin

Chaperonins are able to form two-dimensional ordered arrays

A subunit of the natural chaperonin Sulfolobus (a) and its mutants (b, c, d, e, f). The middle column is a top view, the right is a side view. The protein subunit is colored yellow, one of the 18 identical components of the complex

Archaebacterium of the genus Sulfolobus - lover of extreme life

Chaperonins are large protein complexes that have an internal cavity with an average diameter of 3 nm. In the cell, they perform a very important function: ensure the correct folding of other proteins; however, experts in the field of nanotechnology have found another application for these molecules.

The fact is that not only protein can be placed in the chaperonin cavity, but also, for example, a particle of gold or a quantum dot. Chaperonins have another feature: under certain conditions, they are able to form ribbons and two-dimensional arrays with a high degree of ordering. Such "two-dimensional crystals" can already be used as matrices to create an ordered array of quantum dots.

However, the possibilities of using chaperonins are limited, it would seem, by nature itself: the diameter of the cavity (and, therefore, the size of the trapped particles) is determined rather rigidly. A group of scientists from the USA was able to correct this annoying “misunderstanding”. They took the chaperonin of one of the most extreme inhabitants of our planet - the archebacterium of the genus Sulfolobus, which lives at temperatures above 80 degrees and a pH below 3.0! Its chaperonins are composed of 18 subunits.

To begin with, the researchers studied the structure of chaperonin: this protein complex consists of two rings, each of which is formed by 9 protein subunits (however, this structure is characteristic of all chaperonins, only the number of subunits varies). Each subunit, in turn, has three domains: equatorial, small intermediate and apical. Scientists have suggested that the equatorial domain is responsible for the interaction of subunits, while the apical domain is responsible for the size of the central cavity. It should be noted that natural chaperonin has a cavity diameter of exactly 3 nm.

As a result, mutant subunits, lacking a part or the whole apical domain, were modeled, and the shape of chaperonins composed of such altered subunits was predicted. In order not to be unfounded, after modeling, scientists synthesized these proteins and studied their parameters. To their joy, mutant proteins not only assembled into double rings, as was predicted, but also formed ribbons and two-dimensional arrays. Now scientists have the opportunity to choose chaperonin with a cavity diameter of 3, 9, 10 or 11 nm. So, the technology of the future is one step closer.

Read also about the studies of another "extremal" that can survive even under the influence of extremely hard radiation: "A strange berry that is resistant to radiation."

"Nanometer"

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