Scientists Isolate New Antifreeze Molecule in Alaska Beetle
Scientists have identified a novel antifreeze molecule in a
freeze-tolerant Alaska beetle able to survive temperatures below minus 100
degrees Fahrenheit. Unlike all previously described biological antifreezes that
contain protein, this new molecule, called xylomannan, has little or no
protein. It is composed of a sugar and a fatty acid and may exist in new places
within the cells of organisms.
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"Scientists have identified a novel
antifreeze molecule in a freeze-tolerant
Alaska beetle, Upis ceramboides,
able to survive temperatures
below minus 100 degrees Fahrenheit.
Unlike all previously described biological
antifreezes that contain protein, this
new molecule, called xylomannan, has little
or no protein. It is composed of a
sugar and a fatty acid and may exist in
new places within the cells of organisms."
(Credit: Todd Sformo and Franziska Kohl)
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"The most exciting part of this discovery is
that this molecule is a whole new kind of antifreeze that may work in a
different location of the cell and in a different way," said
zoophysiologist Brian Barnes, director of the University of Alaska Fairbanks
Institute of Arctic Biology and one of five scientists who participated in the
Alaska Upis ceramboides beetle project.
Just as ice crystals form over ice cream left too
long in a freezer, ice crystals in an insect or other organism can draw so much
water out of the organism's cells that those cells die. Antifreeze molecules
function to keep small ice crystals small or to prevent ice crystals from
forming at all. They may help freeze-tolerant organisms survive by preventing
freezing from penetrating into cells, a lethal condition. Other insects use
these molecules to resist freezing by supercooling when they lower their body
temperature below the freezing point without becoming solid.
UAF graduate student and project collaborator Todd
Sformo found that the Alaska Upis beetle, which has no common name, first
freezes at about minus 18.5 degrees Fahrenheit in the lab and survives
temperatures down to about 104 degrees below zero Fahrenheit.
"It seems paradoxical that we find an
antifreeze molecule in an organism that wants to freeze and that's adapted to
freezing," said Barnes, whose research group is involved in locating
insects, determining their strategies of overwintering and identifying the
mechanisms that help them get through the winter
A possible advantage of this novel molecule comes
from it having the same fatty acid that cells membranes do. This similarity,
says Barnes, may allow the molecule to become part of a cell wall and protect
the cell from internal ice crystal formation. Antifreeze molecules made of
proteins may not fit into cell membranes.
"There are many difficult studies ahead,"
said Barnes. "To find out how common this biologic antifreeze is and how
it actually prevents freezing and where exactly it's located."
This project was led by Kent Walters at the
University of Notre Dame with collaborators Anthony Serianni and John H. Duman of
UND and Barnes and Sformo of UAF and was published in the Dec. 1 issue of the
journal Proceedings of the National Academy of Sciences.
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