Angew. Chem. Int. Edn doi:10.1002/anie.200903100 (2009)

Proteins, like many other nanometre-scale objects, cannot normally exist in the liquid state. Instead they sublime or degrade upon heating.

Building on others' work with inorganic nanoparticles, Stephen Mann at the University of Bristol, UK, and his colleagues show that it is possible to generate liquid proteins by substituting a positively charged polymer for their carboxy-terminal groups. They then added another polymer, this time negatively charged. After removing water, the team heated the solid until it formed a liquid crystal, which melted at 50 °C. The protein melt returned to its solid phase at −50 °C.

The solid-to-liquid phase change is possible because the polymer extends the range of intermolecular forces. It is likely that the method could be generalized for a wide range of biological nanostructures.