U of S Researchers Use Synchrotron to Shed Light on Cadmium's Role in Carbon Cycle
Posted May 04, 2005
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FOR RELEASE - 11:00 a.m. May 4, 2005 2005-05-03-AR
U of S Researchers Use Synchrotron to Shed Light on Cadmium's Role in Carbon Cycle
An international team that includes two University of Saskatchewan Canada
Research Chairs has discovered that the element cadmium, well known for its
toxicity to humans and other animals, may play an essential role in
regulating atmospheric carbon.
The findings will be published in the May 5, 2005 issue of the prestigious
science journal Nature.
The team includes U of S geological sciences professors Graham George and
Ingrid Pickering and colleagues from Woods Hole Oceanographic Institute in
Massachusetts, Sandia Laboratories in California, ExxonMobil Research and
Engineering, and Princeton University in New Jersey.
Working at the Stanford Synchrotron Radiation Laboratory in California,
George and Pickering used synchrotron X-rays to partly determine the shape
of an enzyme that regulates levels of carbon dioxide in single-celled plants
called diatoms. Colleagues on the team isolated the genes responsible for
the cadmium enzyme, which also appear to be unique.
George and Pickering confirmed that the plant enzyme, cadmium carbonic
anhydrase, does indeed use cadmium - the first known biological use of the
element.
"Our research establishes a role for cadmium for the first time. No one has
done this before," George says.
The team found that the cadmium enzyme performs much the same role as
zinc-based enzymes in land plants. The U of S researchers compared the two
types of enzymes using data generated at the Stanford synchrotron.
"It turns out that cadmium may play a vital role in the global carbon
cycle," George says. "The enzyme is used by diatoms in the first step of
photosynthesis, which is responsible for uptake of carbon dioxide from the
atmosphere."
Like all plants, diatoms use photosynthesis to take in carbon dioxide and
release oxygen. Since they are present in all the world's oceans, which
cover about 70 per cent of the Earth's surface, diatoms have a huge
collective impact.
The researchers speculate that the diatoms' capacity to use cadmium
developed because ocean waters contain only trace amounts of certain
essential metals. In fact, the diatoms prefer to produce a zinc-based enzyme
rather than the cadmium version. But the ability to make a cadmium enzyme
allows the microscopic plants to better survive in their environment because
surface seawater contains almost no zinc.
Until now, cadmium was thought to be something solely to be avoided. While
our bodies can get rid of the metal, excessive amounts can damage the
kidneys, bones, nervous and cardiovascular systems.
Cadmium has many industrial uses such as nickel-cadmium rechargeable
batteries, paint pigments, plating, alloys, and plastics. It is a naturally
occurring element and can accumulate in crops, prompting efforts, for
example, to develop low-cadmium varieties of durum wheat for Saskatchewan
soils.
"What's interesting here is the changing face of cadmium from a bad guy to a
good guy," George says.
George and Pickering are experts in synchrotron X-ray analysis of metals in
natural systems, such as mercury in fish and selenium in Prairie plants. The
two are actively involved in the development of the Canadian Light Source
synchrotron at the University of Saskatchewan (www.lightsource.ca). They
actively promote its use through lectures and workshops such as the upcoming
"Frontiers in Bio-Metals" workshop at the University of Saskatchewan, Royal
University Hospital on May 11 (www.lightsource.ca/bio-metals).
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For more information, contact:
Graham George
Department of Geological Sciences
College of Arts and Science
University of Saskatchewan
(306) 966-5722
graham.george@usask.ca
Michael Robin
Research Communications
University of Saskatchewan
(306) 966-2427
michael.robin@usask.ca
www.usask.ca/research
