Facility ups top X-ray pulse rate by orders of magnitude
First results shed light on antibiotic resistance. Andrew Masterson reports.
X-ray flashes generated every 0.000,000,220 seconds that vapourise tiny crystals grown from a molecule extracted from a bacterium, propelled down a tunnel 3.4 kilometres long on a jet of water moving as fast as a Formula 1 race car, have helped scientists crack one of the mysteries of antibiotic resistance.
The result – achieved by a team of 125 researchers led by Max Wierdorn of the Centre for Free-Electron Laser Science at the Deutsches Elektronen-Synchrotron (DESY) in Germany – is published in the journal Nature Communications.
It concerns the mechanics of an enzyme known as CTX-M-14 β-lactamase, produced by a bacterial species known as Klebsiella pneumoniae, which is responsible for a growing number of drug-resistant hospital-acquired infections around the world.
And while the findings – which illuminate how the bacterium uses the enzyme much like a pair of scissors to render penicillin-derived antibiotics useless – are valuable, the true worth of the experiment is technical rather than biological.
The K.pneumoniae research constitutes the first proper work conducted inside the DESY facility’s brand spanking new X-ray free-electron laser, known as the European XFEL.
The laser works, essentially, by imaging crystals grown from target molecules. This has to be done multiple times, because the intense energy of the laser destroys each one crystal it hits, as well as instantly vaporising the water jet on which it is propelled.
And while the method, broadly speaking, is well established, the XFEL takes it to a completely and dramatically new level.
Until now the fastest laser pulse rate ever achieved was 120 per second, or about one every 8,000,000 nanoseconds. Wierdorn and his colleagues achieved a rate several orders of magnitude faster, at one every 220 nanoseconds.
Before starting work on its first piece of original research – the imaging of the bacterial enzyme – the scientists had to establish proof-of-concept, and create a reference point. They did this by imaging a very well known and fully understood enzyme, lysozyme, found in egg-white.
The result – the securing of which involved zapping thousands of crystals propelled on a water jet moving at 100 metres per second – perfectly matched existing lysozyme models, with details recorded down to an astounding 0.18 millionths of a millimetre.
The benefits of the XFEL facility, say the researchers, will derive not only from the extremely fine resolution that can be achieved, but also from the time needed to do it.
“This is an excellent proof of the X-ray laser's performance,” says co-author and XFEL pioneer Henry Chapman from Germany’s University of Hamburg.
“We are very excited about the speed of the analysis: Experiments that used to take hours can now be done in a few minutes, as we have shown. And the set-up that we used can even be further optimised, speeding up data acquisition even more. The European XFEL offers bright prospects for the exploration of the nanocosm.”