3D Virus Visualisation

Researchers at an I.B.M. laboratory have captured a 3D image of a biological virus using, for the first time, a technique that has some similarity to magnetic resonance imaging, a tool routinely used by physicians to peer inside the human body. Although the technique is akin to M.R.I., the results were 100 million times better in terms of resolution with the new technique, magnetic resonance force microscopy, or M.R.F.M. The team of researchers, reports in the ‘The Proceedings of the National Academy of Sciences’ that they have captured a 3D image of a tobacco mosaic virus with a spatial resolution down to four nanometers. Techniques like atomic force and scanning tunneling microscopes have provided images of individual atoms (an atom is about one-tenth of a nanometer in diameter). But these techniques are more destructive of biological samples because they send a stream of electrons at the target in order to get an image. And these microscopes cannot peer beneath the surface of the Lilliputian structures.

Magnetic resonance force microscopy employs an ultrasmall cantilever arm as a platform for specimens that are then moved in and out of proximity to a tiny magnet. At extremely low temperatures the researchers are able to measure the effect of a magnetic field on the protons in the hydrogen atoms found in the virus. By repeatedly flipping the magnetic field, the researchers are able to cause a minute vibration in the cantilever arm which can then be measured by a laser beam. By moving the virus through the magnetic field it is possible to build up a 3D image from many 2D samples. The researchers said they believed the tool would be of interest to structural biologists who are trying to unravel the structure and the interactions of proteins. It would be particularly useful for biological samples that cannot be crystallized for X-ray analysis. Although the structure of DNA molecules has already been characterized by other means, it will be possible to use the system both to look at the components that make up the basic DNA structure as well as to make images of interactions among biomolecules.

More information:

http://www.nytimes.com/2009/01/13/science/13mri.html?_r=1