Bugged by Antifreeze

Winter has descended upon Alaska, and people who want to stay mechanically mobile throughout the cold season are asking the vital question: Did I check the antifreeze?

Meanwhile, uncountable numbers of Alaska's insects that intend to stay immobile for the season have adjusted their antifreeze levels without checking anything. Otherwise, they'd never regain mobility come spring. They didn't have to think about it, because generating antifreeze and adjusting its level is something certain northern insects have evolved to do.

Among the local creepy-crawlies capable of freeze-proofing themselves with homegrown chemicals is the spruce budworm. This pest is actually a kind of caterpillar, the larva of a small moth. Though not as spectacular as the damage spruce bark beetles can cause (as Alaska's forests now show), the economic and ecologic problems the cold-hardy budworms produce are bad enough to worry foresters.

It would be just, perhaps, if someone could find an economically valuable use for spruce budworms ...and yes, of course, it looks as if someone has. It's an indirect use, but even so--if you have a sensitive stomach, you may want to stop reading this now.

The potential use comes about because of the nature of insect (or at least budworm, and also mealworm---another pest) antifreeze. The insects don't use ethylene glycol such as car radiators require; instead, they use proteins. According to an article that appeared recently in the magazine Science News, the proteins lower the freezing point of water below 0 degrees centigrade (32 degrees F.) when it is chilled without changing the melting point of ice when it is heated. This neat trick is known as thermal hysterosis.

Members of Alaska's research community have long known about (and poked into the workings of) insect antifreeze, but the most recent studies are a Canadian effort. Scientists in Ontario are close to deciphering the nature of the buggy proteins. Though they haven't yet figured out exactly how the antifreeze produces thermal hysterosis, the Canadians think the proteins bind to the surface of tiny ice crystals and inhibit their growth. They speculate that the repeating arrangement of hydrophilic--that is, water-loving-amino acids within the proteins may match up nicely with the arrangement of water molecules in ice. This could, in effect, lock out additional water molecules otherwise ready to grab onto the ice crystal. However it operates, though, the process works well. The Canadian scientists found that insect antifreeze proteins could lower the freezing point by as much as five and a half degrees centigrade.

Now, unlikely as it may seem, this interesting investigation into the workings of nature in the cold regions potentially has some immediately practical applications. One such possibility now under consideration is using the antifreeze proteins to preserve organs and tissues for transplant. The great potency of the insect antifreeze means it could be used in very low concentrations for this purpose, a valuable feature when the least possible contamination is demanded.

The insect proteins have another quality that makes them appropriate for supercooling tissues for transplant. Unlike other natural antifreeze proteins, such as the one found in arctic and antarctic fishes, insect antifreeze affects the growth of ice crystals (when they finally do grow at all) so that they form smooth, hexagonal disks rather than spiky, sharp forms. Smooth disks do less damage to cells during freezing than would pointed spicules.

Another possible use--brace yourself, now--could be in processing frozen foods. One reason that foods kept a long time in a freezer lose quality is that ice recrystallizes within them. That can ruin texture and alter flavor; think, for example of the cardboard taste of elderly ice cream. And insect antifreeze inhibits that recrystallizing.

Yes, it may be coming: Ben & Jerry & Budworms' ice cream. Once buggy bits in food might cause lawsuits, but soon the right bit of bug (or at least of buggy chemistry) may be a most desirable additive.