New
research by scientists at the University of Bristol, U.K., has challenged one
of the key beliefs in chemistry: that proteins are dependent on water to
survive and function. The team’s findings, published this month in
Chemical Science, could eventually lead to the development of new
industrial enzymes.

Proteins
are large organic molecules that are vital to every living thing,
allowing us to convert food into energy, supply oxygen to our blood and
muscles, and drive our immune systems.  Since proteins evolved in a
water-rich environment, it is generally thought that they are dependent
on water to survive and function.

Proteins
consist of one or more polypeptides—chains of amino acids held together
by peptide bonds.  If a protein in water is heated to temperatures
approaching the boiling point of water, these chains will lose their
structure and the protein will denature (unfold).

A
classic example of denaturing occurs when an egg is hard-boiled: the
structures of the proteins in the egg unfold with temperature 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 refolding of the structure.

Previously,
it was thought that water was essential to the refolding process,
however the Bristol findings suggest this isn’t necessarily the case.

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

Dr
Perriman said: “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 C, refolded
back to its original structure.

“We
then used the Circular Dichroism beamline (B23) at Diamond Light
Source, the UK’s national synchrotron science facility in Oxfordshire,
to track the refolding of the myoglobin structure and were astounded
when we became aware of the extremely high thermal resistance of the new
material.”

These
findings could pave the way for the development of new industrial
enzymes where hyper-thermal resistance would play a crucial role, in
applications ranging from biosensor development to electrochemical
reduction of CO2 to liquid fuels.

Hyper-thermal stability and unprecedented re-folding of solvent-free liquid myoglobin

Source: University of Bristol