Thaindian News

Washington, March 6 (IANS) A Purdue University research team has captured the biggest, brightest and clearest three dimensional image of a virus, the tiniest ever micro-organism in existence. The image is only 4.5 angstroms across, a million of which would equal the thickness of a strand of human hair. It is also twice as large as that obtained previously and with the highest ever resolution for a living organism of this size.

In a breakthrough, the team led by Wen Jiang captured the image with single-particle electron cryomicroscopy, Sciencedaily reported.

“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,” Wen said.

“It is as if the virus is frozen in glass and it is alive and infectious while we examine it.”

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. Other imaging techniques require the manipulation of the sample, Wen said.

Roger Hendrix of the University of Pittsburgh said: “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.”

In electron microscopy, a beam of electrons takes the place of the light beam used in a conventional microscope. Their use in place 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.

Cryo-EM requires high-end electron microscopes and powerful computing resources. The research team used the Baylor College of Medicine’s cryoelectron microscope. It is expected that Purdue will install a state-of-the-art cryoelectron microscope in 2009.

Computer programmes are used to extract the signal from the microscope and to combine thousands of two-dimensional images into an accurate three-dimensional image that maps the structure of the virus.