In the 1950s, an interesting question was asked of Dr. Scholander by his friend Dr. Backus - "When arctic fishes swim about in ice water at -1.7 to -1.8 degrees Celsius, WHY DON'T THEY FREEZE?" He knew that fish blood normally freezes at about -0.7 degrees Celsius, and thus, to enable them to live at such low temperatures without freezing to death, these fishes must have developed an unusual survival mechanism.
Dr. Scholander investigated, and found that some marine fish species living in the high north had a compound in their blood that actually lowered the freezing point of the whole fish so that they were safe from freezing all year round. He called the substance "ANTIFREEZE" (See Reference Page). The true nature of these compounds remained unknown until Dr. A. L. DeVries, working with fish species in the Antarctic, identified the antifreezes as proteins.
In the early 1970s, a group of scientists working at the Ocean Sciences Centre of Memorial University, St. John's, Newfoundland also focused their investigations on these proteins that facilitate survival of fish in sub-zero waters. The studies were led by Dr. Garth Fletcher (a physiologist) and Dr. Choy Hew (a protein chemist/engineer and molecular biologist). They soon discovered that many species of fish inhabiting the coastal waters of Newfoundland were also capable of synthesizing antifreeze.
As each new species capable of producing antifreeze was identified, research was carried out to determine:
The molecular structure and activity of the antifreeze proteins or glycoproteins.
The gene sequences responsible for the appearance of antifreeze in the blood.
Mechanisms for secondary processing of antifreeze within the body
In many fish species, the pattern of antifreeze production appears to be related to the environment inhabited. Fish living in constantly cold, icy water are likely to produce antifreeze all year round, while those exposed to cold on a seasonal basis tend to produce antifreeze only during the cold winter months. Thus, certain environmental parameters such as photoperiod and water temperature were studied, and found to have a profound effect on the pattern of antifreeze production.
There are also certain species of insects, plants, fungi and bacteria known to produce antifreeze.
To date, four main types of antifreezes have been identified and characterized, and a fifth type was identified in 1997. While they are very different in molecular structure, they all appear to have similar capabilities - they confer protection from freezing at sub-zero temperatures by inhibiting the growth of ice crystals.
Due to their particular affinity for ice crystals, they are several hundred times more effective at depressing the freezing point than would be expected on the basis of numbers of molecules in solution. This means that while conferring protection from freezing, they are unlikely to cause osmotic problems in biological systems.
Antifreeze proteins have additional properties resulting from their affinity for the ice crystal lattice. They prevent recrystallization and the formation of large, tissue-damaging ice crystals within frozen materials; and they can interact with, and deactivate ice nucleating agents to maintain fluidity in undercooled solutions
In 1990, A/F Protein Principal, Dr. Boris Rubinsky, an expert in the field of ice physics, reported a further interesting property of the antifreeze proteins and glycoproteins - their ability to interact with mammalian cell membranes at hypothermic temperatures and protect such cells from depolarization and death. This important finding has led to considerable applied research in the fields of cell and tissue preservation.