04:03pm Sunday 24 September 2017

NIH scientists identify novel approach to view inner workings of viruses

Cryo-electron microscopy (cryo-EM) is a technique that allows scientists to image very small particles, like structures on the surface of viruses. This method has been useful in helping researchers understand how vaccines work. But, despite the success of cryo-EM, scientists have been unable to clearly visualize structures inside of viruses, because radiation is used to image them. “With lower doses of radiation, it is not possible to see inside the organism,” said lead author Dr. Alasdair Steven of the NIAMS Laboratory of Structural Biology Research. “However, higher doses of radiation damage the virus, destroying the very structures that we would like to view.”

Image of virus and blow-up of inner virus structure.Working in collaboration with the group of Dr. Lindsay Black at the University of Maryland Medical School, Baltimore, Steven and his team were able to turn the problem of radiation damage into an asset. Viruses, one of the simplest life forms, are made up of nucleic acids (DNA or RNA) and the proteins encoded by the nucleic acid instruction manual. The researchers realized that proteins inside the virus are more sensitive to damage than DNA.

In the background, cryo-electron micrographs of purified viruses with their inner structure bubbling from radiation damage. Overlaid, (left) 3D computer reconstruction of a virus’s outer shell and tail in gray, with the inner structure in magenta; (right) blow-up of the inner viral structure in magenta.

“We first used low doses of radiation and recorded images in which the inner structure of the virus was invisible,” said Steven. “Next, we used high doses of radiation, and found that the inner structure could be seen as a cylinder of bubbles.” While the inner structure was damaged, the team was able to superimpose the images, using three-dimensional computer reconstruction. As a result, they were able to clearly visualize the viral structure. The investigators call this technique bubblegram imaging.

Moving forward, the team members anticipate many uses of bubblegram imaging. Ideally, this technique will allow a better understanding of the inner workings of viruses, providing more opportunities for developing novel therapies. Beyond studying viral structure, cryo-EM could be used to visualize interactions of proteins with DNA in human cells. One exciting prospect lies in using this approach to visualize differences in cancer vs. non-cancer cells. “This new cryo-EM procedure renders previously invisible proteins visible and, thus, will provide new understanding of cell biology,” said Steven.

For more information on the NIAMS Laboratory of Structural Biology Research, visit http://www.niams.nih.gov/Research/Ongoing_Research/Branch_Lab/Structural_Biology/default.asp.

The mission of the NIAMS, a part of the U.S. Department of Health and Human Services’ National Institutes of Health, is to support research into the causes, treatment and prevention of arthritis and musculoskeletal and skin diseases; the training of basic and clinical scientists to carry out this research; and the dissemination of information on research progress in these diseases. For more information about the NIAMS, call the information clearinghouse at (301) 495-4484 or (877) 22-NIAMS (free call) or visit the NIAMS website at http://www.niams.nih.gov.

About the National Institutes of Health (NIH): NIH, the nation’s medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov.

NIH…Turning Discovery Into Health

Trish Reynolds

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