If this myoglobin molecule can function without water, how many other proteins could too? (Image: Laguna Design/SPL/Getty Images )

Water, water everywhere – but at least one protein can function without the wet stuff.

Adam Perriman at the University of Bristol, UK, and colleagues 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. “There are ways to replace water with something else and still keep proteins happy,” says Martin Weik of the Institute for Structural Biology in Grenoble, France, a co-author on the work.

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, Perriman and colleagues were able to observe proteins functioning normally in an entirely solvent-free environment.

“The proteins are themselves the liquid,” explains Perriman.

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.

John Ward of University College London, who was not involved in the study, suggests that this line of work could also lead to chemical engineering processes that produce fewer hazardous by-products. “For more green chemistry applications we need a closer marriage of biocatalysis and chemical catalysis. The modifications [demonstrated by Weik and his colleagues] and other modifications such as PEGylation will be useful,” he says.

An obvious question raised by the prospect of solvent-free proteins is whether protein-based life might be able to exist in waterless environments. This type of protein-polymer hybrid, however, wouldn’t occur naturally since the polymer used is unlike any found in nature.

Journal reference: Journal of the American Chemical Society, DOI: 10.1021/ja303894g