Aug 10, 2007
One of the few scientific success stories of the International Space Station has been its use to grow large, pure crystals in microgravity (see Space station unlocks new world of crystals (http://www.newscientist.com/article/dn3704-space-station-unlocks-new-world-of-crystals.html)).
Now scientists from the Netherlands and Japan have shown that a strong magnetic field can mimic the effects of microgravity when growing protein crystals. The new Earth-bound technique could provide a cheaper and easier way to produce crystals of the same quality as those grown aboard the ISS.
The approach uses the same principle famously employed to levitate a live frog (http://www.newscientist.com/article/mg15420771.600-frog-defies-gravity.html) in 1997. This exploits the fact that diamagnetic materials - including most organic materials - are repelled by very strong magnetic fields as a result of changes in the orbital motion of their electrons.
Researchers at the High Field Magnet Laboratory (http://www.hfml.ru.nl/) at Radboud University in Nijmegen and colleagues at Tohoku University, Japan, have now shown that this effect can be used to grow a pure crystal of the protein lysozyme.
Large, pure protein crystals are prized by researchers because they give good results with a technique called X-ray crystallography. This can reveal to biologists and drug designers the precise structure of the protein.
But the way crystals grow on Earth means they inevitably develop defects. As a growing crystal "feeds" on a solution, a small depleted zone of liquid is created around it. This liquid is more buoyant and floats upwards, creating a convection pattern on top of the crystal and introducing flaws.
Crystals grown in space do not suffer this problem due to the lack of gravity, although the acceleration of a spacecraft or the movements of astronauts can still cause defects to develop in crystals.
By adjusting the magnetic field produced by a 33-tesla magnet, the researchers were able to counteract the force of gravity, stilling the convection currents around the growing crystal.
They were even able to create a sort of negative gravity and make the growth plume travel downwards.
"The authors of the paper have a technique that can produce the same effects of microgravity on crystal growth in a much more controlled manner than could ever be achieved on the the International Space Station," says Edward Snell, a structural biologist at the State University of New York in Buffalo, US.
What's more, the technique will be faster and much cheaper than growing crystals in space, he says.
The researchers only ran the magnets long enough to show that they could control the growth plume. The next step, they say, is to design magnets that can be run for long enough to grow complete crystals of the necessary size.