Friday, 14 February 2014

A short addendum to the molecule of the month: Water

"It's a strange world of language in which skating on thin ice can get you into hot water". A nice quote from the Philadelphia journalist Franklin P. Jones and it came to mind when I read in the Journal Science this week about the interactions between water molecules and an interesting anti-freeze protein from the winter flounder.

Anti-freeze, (typically propylene glycol) as you will know, is what we add to our cars to prevent freezing in the radiator and screen wash. These are compounds that lower the freezing point of water, and since we don't often experience severe freezing in the UK, they are good enough for most purposes. Some living organisms have evolved mechanisms to survive extreme temperatures and the expression of antifreeze proteins is just one. The interesting feature of these molecules is that they are able to offer an alternative to the organised packing of water molecules in ice. The image above is actually an antifreeze protein from the Mealworm, Tenebrio molitor, our very own UTC model organism! 

The new structure (left) reported by Peter Davies' group in Canada, shows how a protein wraps itself around a core of water molecules: exactly the opposite of most proteins, whose folding relies on burying its amino acid side chains into an oily (hydrophobic) core. This sequestering of water molecules effectively blocks (or slows) the nucleation of ice crystals. This is a great example of how Nature meets the challenges of the physical properties of water in order to take advantage of its other many, life sustaining properties.

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