New Scientist Tech

Magnetic gravity trick grows perfect crystals

* 18:28 10 August 2007

* NewScientist.com news service

* Kurt Kleiner

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).

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 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 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.

Precise structure

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.

Anti-gravity

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.

Journal reference: Applied Physics Letters (vol 90, p 264105).

--
R. A. Hettinga
The Internet Bearer Underwriting Corporation
44 Farquhar Street, Boston, MA 02131 USA
"... however it may deserve respect for its usefulness and antiquity,
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--- In spacesettlers@yahoogroups.com, "R.A. Hettinga" wrote:
>
>trick-grows-perfect-crystals.html>
>
> The approach uses the same principle famously employed to levitate a
> live frog 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.

Could this be used for pseudogravity, instead of having entire
structures rotate? (Assuming we had something that is to present
electromagnets as a laser is to an incandescent light bulb.)

On 8/13/07, Dan Wylie-Sears wrote:
(...)
> Could this be used for pseudogravity, instead of having entire
> structures rotate? (Assuming we had something that is to present
> electromagnets as a laser is to an incandescent light bulb.)
(...)

In principle, yes, though our electric and electronic stuff would need
a lot of... adaptations to cope with strong magnetic fields.

On 13/08/07, Dan Wylie-Sears wrote:
> Could this be used for pseudogravity, instead of having entire
> structures rotate? (Assuming we had something that is to present
> electromagnets as a laser is to an incandescent light bulb.)

The small frog that was levitated a while back in this kind of magnet
didn't die. However I did read that they analysed its DNA and there
seems to have been some damage. That would presumably rule this out as
a means of generating positive gees.

--
-Ian Woollard

We live in an imperfectly imperfect world. If we lived in a perfectly
imperfect world things could be a lot better.