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This is the fish, Macropteris maculatus, with antifreeze protein structure. Credit: Konrad Meister
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Together
with cooperation partners from the U.S., the researchers surrounding
Prof. Dr. Martina Havenith (Physical Chemistry II of the RUB) describe
their discovery in a so-termed Rapid Communication in the prestigious
American chemistry journal, the Journal of the American Chemical Society
(JACS). The journal's independent reviewers evaluated the work as one
of the top 5% of all submissions.
Better than household antifreeze
Temperatures
of minus 1.8 ° C should really be enough to freeze any fish: the
freezing point of fish blood is about minus 0.9 ° C. How Antarctic fish
are able to keep moving at these temperatures has interested researchers
for a long time. As long as 50 years ago, special frost protection
proteins were found in the blood of these fish. These so-called
anti-freeze proteins work better than any household antifreeze. How they
work, however, was still unclear.
The
Bochum researchers used a special technique, terahertz spectroscopy, to
unravel the underlying mechanism. With the aid of terahertz radiation,
the collective motion of water molecules and proteins can be recorded.
Thus, the working group has already been able to show that water
molecules, which usually perform a permanent dance in liquid water, and
constantly enter new bonds, dance a more ordered dance in the presence
of proteins – "the disco dance becomes a minuet" says Prof. Havenith.
Souvenir from an Antarctic expedition
The
subject of the current investigations was the anti-freeze glycoproteins
of the Antarctic toothfish Dissostichus mawsoni, which one of the
American partners, Arthur L. Devries, had fished himself on an Antarctic
expedition.
"We
could see that the protein has an especially long-range effect on the
water molecules around it. We speak of an extended dynamical hydration
shell", says co-author Konrad Meister.
"This
effect, which prevents ice crystallization, is even more pronounced at
low temperatures than at room temperature", adds Prof. Havenith.
Nevertheless,
to freeze the water, lower temperatures would be necessary.
Complexation of the AFP by borate strongly reduces the antifreeze
activity. In this case, the researchers also found no change in the
terahertz dance. The researchers' results provide evidence for a new
model of how AFGPs prevent water from freezing: Antifreeze activity is
not achieved by a single molecular binding between the protein and the
water, but instead AFP perturbs the aqueous solvent over long distances.
The investigation demonstrated for the first time a direct link between
the function of a protein and its signature in the terahertz range. The
studies were funded by the Volkswagen Foundation.
Citation:
Simon
Ebbinghaus, Konrad Meister, Benjamin Born, Arthur L. DeVries, Martin
Gruebele and Martina Havenith: “Antifreeze glycoprotein activity
correlates with long-range protein-water dynamics.” In: Journal of the
American Chemical Society. August 16, 2010, DOI: 10.1021/ja1051632
SOURCE: Ruhr-University Bochum
