| Although
they've demonstrated their new molecule can encapsulate
arsenic in a laboratory setting, Johnson says, the challenge
of treating poisoned individuals remains. The next step
is to verify that the new molecule can render arsenic
harmless without creating new problems in the human
body. "We're now trying to prove that our molecule
wants arsenic more than things in your body want arsenic,"
says Johnson. Numerous
studies have linked consumption of minute amounts
of arsenic in drinking water with higher incidences
of lung, bladder, kidney and skin cancers, among other
potentially fatal conditions. Arsenic is naturally
abundant in the Earth's crust, and arsenic compounds
are involved in some industrial applications.
The
U.S. Environmental Protection Agency, in compliance
with the Safe Water Drinking Act, currently requires
that public water systems contain arsenic concentrations
of less than 50 parts per billion (ppb). In 2006,
this level is to be reduced to 10 ppb. This stricter
standard has been endorsed by the World Health Organization
since 1993.
Developing
countries face serious problems due to arsenic-laced
water sources but arsenic also is a problem in the
United States. Roughly 10 percent of U.S. groundwater
contains arsenic concentrations above 10 ppb. In Johnson's
backyard, Oregon's bucolic Willamette Valley, more
than 20 percent of wells have arsenic levels greater
than 10 ppb. Of these, almost 10 percent exceed 50
ppb.
While
they used computer-generated molecular models to predict
many of the features they observed, Johnson says,
the project also yielded some unexpected, and pleasant,
surprises.
"We
have stumbled upon some surprisingly stable self-assembled
arsenic complexes. Someday, this approach may provide
better agents for sensing and removing arsenic from
the environment as well as the body," Johnson
says.
Self-assembly
refers to the ability of molecules to naturally join
themselves together into larger structures due to
the manners in which their geometric and binding structures
complement one another. This feature, which is like
a puzzle that puts itself together, is quite promising
because it creates a final product that is more stable
than the sum of its parts, Johnson explains.
In
addition to modeled predictions, the structure of
the molecule was confirmed using two primary methods.
Nuclear magnetic resonance (NMR) spectroscopy uses
the same principles that are the basis for magnetic
resonance imaging (MRI), a commonly used medical scan
of human tissue. The sample molecules are placed in
a powerful magnetic field and are stimulated by specific
patterns of radio waves. The patterns of energy that
the molecules then release are interpreted to determine
composition and structure. Another technique, X-ray
diffraction, analyzes the scattering pattern of x-rays
directed at a substance in order to characterize its
atomic-scale structure.
Johnson,
a UO assistant professor of chemistry, supervises
the work of W. Jake Vickaryous (pronounced like the
word "vicarious"), the UO doctoral degree
candidate in chemistry who synthesized the molecule
and is the lead author for the Angewandte Chemie article.
Rainer Herges, the article's third co-author, is a
professor at the Institut for Organische Chemie in
Kiel, Germany, who produced the computer modeling
studies for the project.
This
phase of their work was funded by a UO research grant.
In September, Vickaryous was awarded a National Science
Foundation fellowship to support doctoral training
at the interface of chemistry and physics. He will
study new materials for electronics and optics through
control of nanoscale structure.
The Oregon Nanoscience and Microtechnologies Institute
is a collaboration involving Oregon's three public
research universities--the University of Oregon, Oregon
State University, Portland State University; the Pacific
Northwest National Laboratory (Richland, Wash.); the
state of Oregon; selected researchers from the Oregon
Graduate Institute and the Oregon Health & Sciences
University School of Dentistry; and the world-leading
"Silicon Forest" high technology industry
cluster of Oregon and southwest Washington.
CONTACT:
Melody Ward Leslie, 541-346-2060, mleslie@uoregon.edu
SOURCE:
Darren Johnson, 541-346-1695, dwj@uoregon.edu
LINKS:
Darren Johnson's home page: http://uoregon.edu/~chem/dwjohnson.html
Angewandte
Chemie (subscription needed): http://www3.interscience.wiley.com/cgi-bin/abstract/109746296/ABSTRACT
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