With the weather turning cold off and on maybe it’s time to check the antifreeze in your car. Antifreeze is used in our vehicles to keep the engine blocks from cracking when the old worn out coolant freezes. This is the same thing that happens to cells in a living organism. Freezing water in a cell expands and ruptures the cellular membrane letting everything leak out. If you don’t think this happens, put a tomato in your freezer overnight and take it out the next morning to thaw. Make sure you put it in a bowl or you will have a mess on your floor. Well, if this happens to plants how do fish survive in temperatures cold enough to freeze saltwater?Some species of fish have “antifreeze molecules” in their blood that allows them to live in subfreezing water by plugging gaps in existing small ice crystals and preventing the attachment of more ice molecules. Further ice crystal growth is stopped. Antarctic fish have developed proteins that act as antifreeze. These antifreeze proteins are a group of unique molecules that help some coldwater fish to avoid freezing in the icy water. Dr. Art DeVries discovered these proteins from fish that he collected at McMurdo Station while he was a graduate student at Stanford University in the early 1960s.Waters of the southern oceans are so cold that temperate and tropical fish would freeze if they were placed in these waters. The presence of salt in seawater allows it to remain a liquid until about 28.6F, almost 3.5F degrees below the freezing point of freshwater. The antifreeze proteins, along with normal body salts, depresses the freezing point of blood and body fluids to 27.5F, which is slightly below the freezing point of seawater. These proteins bind to and inhibit growth of ice crystals within body fluids through an absorption-inhibition process. The proteins attach to small ice crystals, stemming their growth. The mechanism that inhibits further growth of the ice crystal remains under study. Apparently, Antarctic fish are able to survive with very small ice crystals present in their body fluids.There are several companies working on commercial applications of these antifreeze proteins. The antifreeze compounds are about 300 times more effective in preventing freezing than conventional chemical antifreezes at the same concentration. The effectiveness of the fish antifreeze proteins in inhibiting ice growth suggests that they might be used to prevent freezing of food. For example, they could be used in cryo-preservation of foods that normally are rendered inedible due to ice crystal damage or to bio-engineer cold resistance into living plants, as well as for the cryo-preservation of transplantation tissues and organs. Other areas of study include prevention of kidney stones, gout and gall stones.Some companies in the frozen dessert industry are also studying how antifreeze proteins modify the way that frozen foods recrystallize. Normally, when a product like ice cream melts and is frozen again it loses its smooth texture as ice crystals begin recrystallizing into larger crystals. The antifreeze proteins can modify this process and prevent the crystals from growing. Large quantities of the fish antifreeze protein can now be produced through use of DNA recombinant technology with yeast and bacteria.
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