Richard A Lovett
Beetles adapted to life at temperatures as low as minus-40 or minus-50 degrees Celsius may hold clues to everything from better aeroplane de-icers to improved methods of storing tissues for organ transplants, scientists say.
Biologists have known since the 1960s that some animals contain proteins that act as antifreeze, allowing them to survive at temperatures where their cells should be freezing, says Konrad Meister, a protein biophysicist at Max Planck Institute for Polymer Research, in Germany.
These proteins, it was known, seek out microscopic ice crystals, adhere to them and block their growth before they become large enough to cause cellular damage.
“As soon as there’s an embryonic ice crystal, they bind to it and prevent the crystal from growing,” Meister says.
To find out how this worked, his team turned to one of the most powerful such antifreeze proteins yet discovered, from a Scandinavian insect called the black-spotted longhorn beetle (Rhagium mordax).
In a study published in The Journal of Chemical Physics, they placed this protein on smooth sheets of ice, then peered at the underlying ice surface with a method called heterodyne-detected vibrational sum-frequency generation spectroscopy to determine what was going on at the molecular scale.
Conventional antifreezes, such as the fluid put into car radiators, work by dissolving in the water, thereby lowering its freezing point, much like salt in the ocean.
Antifreeze proteins, Meister says, work by affecting how water molecules align at the surface of the ice crystal.
If these molecules align one way, they bind to the crystal, adding a new layer of ice. If they align the opposite way, they can’t bind to it, and freezing halts.
When an antifreeze protein binds to an ice crystal, Meister says, it basically forces the intervening water molecules to bind to it — pointing in its direction, rather than pointing toward the ice.
“We could show that these antifreeze proteins have, basically, a special power over the water, and it’s even stronger than the power of the ice,” he says.
“The water molecules are my dancing partner. We prevent another dancing partner from coming between us.”
Potential applications are numerous, though three obvious ones are the development of better materials for de-icing airplanes, preserving organs, and keeping taste-and-texture-destroying ice crystals from growing in frozen foods such as ice cream.
“Whenever there’s a problem that involves ice formation, this is very interesting,” Meister says. It could even be relevant for the development of new anti-ageing lotions, he says, because these, too, are affected by the behaviour of water.
That said, don’t expect to see beetle juice listed as an ingredient in ice cream or other products any time soon.
Although the research is “interesting and novel,” and “the biological relevance is extremely important,” Douglas Goff, a food scientist at the University of Guelph in Canada says, “I am not aware of any commercially available antifreeze proteins at a cost the food industry would bear.”
He adds that he fully supports research into how, exactly, antifreeze proteins do their jobs.
“I think all advances we can make regarding these very interesting molecules are extremely useful,” he says.
Meister agrees that applications go far beyond the specific proteins he studied. The goal, he says, is to understand how antifreeze proteins work, and to use that to develop synthetic compounds, possibly polymers, that work similarly.
“We hope other groups can use this information to optimise the design [and] help them make a compound which is as active as antifreeze proteins,” he says.
