Antifreeze proteins can stop ice melting

The same antifreeze proteins that keep organisms from freezing in cold environments can also prevent ice from melting at warmer temperatures, according to a new Queen's University study.

Laurie Graham and Peter Davies look over ice crystals while in their lab in Botterell Hall. Photo by Michael Onesi

The study presents the first direct measurements of the superheating of ice crystals in anti-freeze protein solutions. Superheated ice crystals can be stabilised above the melting point for hours, at a maximum temperature of about +0.5 degree Celsius.

''You can hold the ice crystal at +0.5 C for an hour and it just doesn't melt. That's highly unusual. Without the antifreeze protein, there is no way that can happen,'' says Queen's biochemistry professor Peter Davies.

The results were published this week in the journal Proceedings of the National Academy of Sciences.

The new study has implications for understanding this process in nature, and also for understanding the recrystallisation of ice. Food stored in freezers is subject to recrystallization, where small ice crystals shrink and large ones grow, damaging the food.

''This particular discovery helps explain why these proteins are so good at stopping the recrystallization process. You have a double whammy – an effect where the ice crystals are stopped from growing, while they are also stopped from melting. I don't think people realized this up until now,'' says Dr. Davies.

Twenty years ago, researchers first proposed that antifreeze proteins can create superheating by suppressing melting at temperatures higher than the equilibrium melting point.

Other members of the international research team include Laurie Graham and Yee-Foong Mok at Queen's, and primary authors, Ido Braslavsky and Yeliz Celik of Ohio University, and Maya Bar of the Weizmann Institute of Science in Israel.