16 April 2012

Water not necessary for life?

by Will Parker

The proteins that are vital to living creatures evolved in Earth's water-rich environment and it was thought that water was vital for proteins to function, but some intriguing new findings from the University of Bristol (UK) challenge this dogma.

Proteins consist of one or more polypeptides (chains of amino acids held together by peptide bonds) that convert food into energy, supply oxygen to our blood and muscles, and drive our immune systems. If a protein is heated in water to temperatures approaching boiling point, the polypeptides will unfold and lose their structure - known as denaturing.

An example of denaturing occurs when an egg is hard-boiled: the structures of the proteins in the egg unfold and stick together, creating a solid. In the egg's case, this process cannot be reversed - however there are many examples where cooling the protein results in the refolding of the structure. Previously, it was thought that water was essential to this refolding process; however, the new findings suggest this isn't necessarily the case.

Using a spectroscopic technique called circular dichroism, Adam Perriman and colleagues have shown that the oxygen-carrying protein myoglobin can refold in an environment that is almost completely devoid of water molecules.

"We achieved this by attaching polymer molecules to the surface of the protein and then removing the water to give a viscous liquid which, when cooled from a temperature as high as 155& #176;C, refolded back to its original structure," Perriman explained.

He believes the findings could enable the development of new industrial enzymes where hyper-thermal resistance plays a crucial role; in applications ranging from biosensor development to the electrochemical reduction of CO2 to liquid fuels.

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Source: University of Bristol