|Water, water everywhere - but at least one protein can function without
the wet stuff. Researchers from the University of Bristol, UK, swapped
the coating of water on myoglobin proteins - which normally carry oxygen
to muscle and give raw meat its red colour - with a synthetic polymer
that acts as a surfactant, effectively turning the proteins into a
viscous liquid with the consistency of thick treacle.
Then they used a neutron-scattering technique to observe how well the
proteins could move, a measure of their proper functioning. They found
that the protein-polymer hybrids moved as well as proteins in water,
remaining flexible and exhibiting the usual internal dynamics.
Importantly, they could still bind oxygen as well as myoglobin does in
living tissue. The finding overturns the dogma that water is the most
important biological molecule.
Previous studies have shown that modifying proteins with polymers can
lead to therapeutic applications. For example, applying a polyethylene
glycol (PEG) coating - a process known as PEGylation - can mask a
protein and help it avoid rejection by the immune system. But where
previous studies have required some kind of solvent for the protein to
function, the Bristol team were able to observe proteins functioning
normally in an entirely solvent-free environment.
Among the applications the team intends to explore are wound dressings
in which the liquid protein is applied like a paste. It could then act
like an oxygen pump, with a chemical reaction between the protein layer
and a glucose membrane drawing oxygen down through the dressing to the
surface of the skin.