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		ANTIFREEZE IN NATURE
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ANTIFREEZE IN FISH
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QUESTION: How many research groups are studying cold-adapted 
proteins in Antarctic fish? What are the results of this research?

ANSWER from Diane Stoecker on February 6, 1995
At McMurdo Station, there is one group working on fish anti-freeze 
proteins, headed by Dr. Art Devries (I think he was on at the end of 
one of the Live From Antarctica broadcasts). Basically, all the fish that 
live around sea-ice or come in contact with sea-ice have some type of 
anti-freeze protein. Most of the proteins work by binding to the lattice 
structure of ice crystals and thus preventing the crystals from growing.

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QUESTION: Can scientists take the lessons learned from the 
'antifreeze' in the blood of Antarctic fish and apply them to oranges to 
prevent them from freezing?

ANSWER from Craig Marshall on January 31, 1995
In some parts of the world fish live in sea water that is covered by sea 
ice where the water temperature is about -1.8 C (degrees Celsius). Fish 
blood has much less salt in it than sea water and so you might expect it 
to freeze, but it does not. In the blood of these fish are antifreeze 
proteins that help to lower the freezing point of their blood to below 
that of sea water.

When an orange freezes, the ice crystals that form break open its cells. 
When the orange thaws, all the cell contents leak out--the cells die and 
the fruit is spoiled. If you could stop the ice crystals from forming 
inside the cells, you might be able to stop the fruit  being damaged by 
frost. One way that has been suggested is to put fish antifreezes into 
the fruit to lower its freezing point.

However, fish antifreeze only lowers the freezing point by about 1 deg. 
C, and when the ice crystals eventually do form, they are much longer 
and sharper and do more damage. The amount of antifreeze in fish 
blood is very large and this amount of protein would probably affect 
the flavor of the oranges. It seems unlikely that this approach will help 
prevent frost damage to oranges. A better approach would be to find 
ways of keeping ice crystals very small inside the orange so they 
would not do so much damage.


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QUESTION: Can you eat the fish that have natural antifreeze? Does it 
effect their flavor?

ANSWER from Dr. Michael Castellini on January 12, 1995
There are no commercial fisheries for the Antarctic fish that have 
antifreeze in them, so they are not eaten by very many people. 
However, many of the explorers ate them and I have tasted some of 
them myself. The big cods taste very good and penguins and seals love 
to eat them! The actual amount of antifreeze is very tiny--it only takes 
a small amount to protect the fish, so it is not like the anti-freeze that 
you would find in your car!

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QUESTION: Why don't penguins freeze to death if it is way below 
freezing?

ANSWER from Terry Trimingham on January 31, 1995:
Penguins are protected by a nice layer of fat covered over by a close-
knit feather suit with a down lining. Their circulation systems are 
adapted to cold climates. Penguins LIKE it cold...I have seen them 
pant from heat when the temperature gets much over freezing!