Explosive X-ray diffraction

08 January 2012
Posted by Dave Ansell.

One of the major ways of discovering the structure of molecules, particularly complex ones like proteins, is X-ray diffraction.  This involves firing a beam of X-rays at a crystal and "reading" the pattern that the reflected x-rays produce.  This is possible because crystals contain repeating molecular units, and so X-rays reflected from the crystal produce a distinct pattern that can be used to identify the structure of the molecule.

However, to decipher a large molecule you need to use very bright X-rays, which can damage the sample.  This damage can create uncertainty as to what the original structure was.

X-Ray diffractionIn a bizzarre twist, scientists from the Center for Free-Electron Laser Science in Hamburg may have reduced this problem by making the X-rays brighter - much brighter.  They use an X-ray laser which produces X-rays a million trillion times more intense than sunlight.  They only fire the laser for 30 femtoseconds, or 30 million billionths of a second, but in just a fraction of this time the sample absorbs so much energy it violently explodes.

You would think this explosion would invalidate any results, but because the explosion is random, all it does is add a bit of background noise to the reflected X-ray pattern without distorting it at all, and because the laser is so much brighter, the results are much better than a conventional X-ray diffraction experiment.  This means that, even though they explosively sacrifice their sample, scientists should be able to discover the structure of proteins more easily in the future.

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