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Sci Tech
New technique enables imaging of minute structures
In one of the first projects to refine imaging technique to the point of near-atomic level resolution, scientists have captured a three-dimensional image of a virus at a resolution of 4.5 angstroms (approximately 1 million angstroms equal the diameter of human hair).
Cryomicroscopy
“This breaks a threshold and allows us to now see a whole new level of detail in the structure. This is the highest resolution ever achieved for a living organism of this size,” said Wen Jiang, an assistant professor of biological sciences at Purdue University, who led a research team that used the emerging technique of single-particle electron cryomicroscopy.
Details of the structure of a virus provide valuable information for development of disease treatments, he said. “If we understand the system — how the virus particles assemble and how they infect a host cell — it will greatly improve our ability to design a treatment,” Jiang said. “Structural biologists perform the basic science and provide information to help those working on the clinical aspects.”A paper detailing the work was published in the February 28 issue of Nature.
The imaging technique, called cryo-EM, has the added benefit of maintaining the sample being studied in a state very similar to its natural environment, according to a Purdue University press release.
Sample manipulation
Other imaging techniques used regularly, such as X-ray crystallography, require the sample be manipulated. Roger Hendrix, a professor of biological sciences at the University of Pittsburgh, said what is learned about viruses can be applied to many other biological systems. “Getting to 4.5 angstrom using this technique is a watershed of sorts because it is the first time we can actually trace the polypeptide chain — the backbone of proteins. Now we can see the tiny gears and levers that allow the proteins to move and interact as they carry out their intricate biological roles.”
Greater detail
In electron microscopy, a beam of electrons takes the place of the light beam used in a conventional microscope. The use of electrons instead of light allows the microscope to ‘see’ in much greater detail. Cryo-EM cools specimens to temperatures well below the freezing point of water.
This decreases damage from the electron beam and allows the specimens to be examined for a longer period of time. Longer exposure time allows for sharper, more detailed images.
Researchers using cryo-EM had obtained images at a resolution of 6-9 angstroms but could not differentiate between smaller elements of the structure spaced only 4.5 angstroms apart. — Our Bureau
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