Drs. Laurie Graham and Peter Davies of Queen's University in Canada found that the potent protein is capable of inhibiting ice growth by about six Celsius degrees. This could allow organs to be stored at lower temperatures, they suggest, expanding the time allowed between removal and transplant.

Lower Risk of Harmful Antibodies

"Transplant organs must now be kept at the freezing point or slightly warmer," Dr. Graham notes. "If we can drop the temperature at which the organ is safely stored, there will be a longer preservation period."

The hyperactive antifreeze protein produced by snow fleas is different from two other insect proteins discovered earlier at Queen's.

"Unlike the antifreeze proteins in beetles and moths, AFPs in snow fleas break down and lose their structure at higher temperatures," explains Dr. Davies, Canada Research Chair in Protein Engineering.

"This means that if used to store organs for transplants, they will be cleared from a person's system very quickly, reducing the possibility of harmful antibodies forming," he adds.

Ice Affinity Purification

An ancient species related to modern insects, snow fleas also are known as "springtails" because of the distinctive springing organ under their abdomen that allows them to leap hundreds of times their one-millimeter length.

Dr. Graham first noticed them while cross-country skiing, and brought several samples into the lab. "It was serendipity," she says now. "They looked like dots of pepper sprinkled on the snow. Later we were able to collect large numbers for testing at the Queen's University Biological Station."

The scientists used a process called ice affinity purification to isolate the new protein, which is rich in the amino acid glycine.

"When you grow a 'popsicle' of ice in the presence of these proteins, the AFPs bind to the ice and become included, while other proteins are excluded," says Dr. Davies. "We use their affinity for ice as a tool to purify the protein."

The antifreeze mechanism of snow fleas has been reported in other parts of the world, including Antarctica, but no one had isolated the protein prior to this study.

In addition to its potential use in organ transplants, it could help to increase frost resistance in plants and inhibit crystallization in frozen foods, the researchers suggest.