The first known example of a liquid protein has been made by chemists at Bristol University, opening up the possibility of a number of medical and industrial applications, including high-potency pharmaceuticals and protein-based coolants and lubricants.
Prof Stephen Mann and Dr Adam Perriman of the university’s School of Chemistry, along with Helmut Cölfen of the Max Planck Institute for Colloid and Interface Research in Germany, have made a liquid form of the iron storage protein, ferritin.
To achieve this, the Bristol team attached positively charged amine groups to the surface of the ferritin, which then acted as binding sites for the electrostatic attachment of a negatively charged polymer surfactant.
The ferritin-polymer composite forms a solid that melts at around 30°C to a liquid crystal with an orderly orientation of particles. When heated to 50°C, the liquid appears to act like an ordinary fluid, with disorder in the positions and orientations of particles.
The liquid protein is more highly concentrated than a protein dissolved in water, which means that higher doses of medically useful proteins could be administered, for example, in new wound dressing treatments. Enzymes that break apart other proteins could also be used to clear wounds of debris from dead cells.
Mann said: ‘This is a very exciting result with fundamental significance for understanding liquids comprised of nanostructured components. Also, it represents a possible way forward to a novel state of biomolecular matter and could, therefore, have a number of important applications. We hope to explore some of these – for example in biomedical and sensor technology – over the next five years or so.’
Ferritin is a globular protein complex consisting of 24 protein subunits and is the primary intracellular iron-storage protein