Why fish in the Arctic don’t freeze

Antarctic or Arctic fish : fresh, not frozen
These fish can survive in the coldest marine environment on the planet

From Wired

Scientists studying why fish in the Arctic ocean don’t freeze have discovered how a natural antifreeze that keeps blood flowing at sub-zero temperatures works.

The temperature of the water in the Arctic is a fairly constant 28.6 degrees Fahrenheit year-round, close to the freezing point of seawater.
The freezing point of fish blood, however, is about 30.4 degrees Fahrenheit.
You’d expect fish traveling beyond a certain latitude to ice up.

Instead, fish are able to keep moving thanks to a frost-protection protein in their blood. It was discovered about 50 years ago, but only now are scientists discovering how the protein works.

Researchers led by Bochum University chemist Martina Havenith used terahertz spectroscopy to examine water molecules in the presence of the protein.
They saw that water molecules, which normally dance around, forming and breaking bonds, slow down in the protein’s vicinity.

“The disco dance becomes a minuet,” said Havenith.

The slowing of the bond-forming process prevents ice crystallization, which would be fatal for the fish.
Under extremely low temperatures the fish can still freeze, but by that point the water around it will have frozen solid too.

The research was funded by Volkswagen, who no doubt want to find better ways of anti-freezing their cars.
The natural proteins found in the fish perform far better than man-made antifreezes, which bond directly with water molecules to lower the freezing point.
The proteins don’t need to bond. Their mere presence is enough to slow freezing.

Links :

• JBC (1978) : Antifreeze glycoproteins from Arctic Fish