The protein shells protecting some viruses rival plexiglass for strength but are surprisingly flexible, a new study suggests. Understanding ways in which viruses protect themselves could help scientists better understand--and fight--viral infections.

Gijs J. L. Wuite of Vrije University in Amsterdam and his colleagues used an atomic force microscope to investigate the shell of a virus known as phi29. A bacteriophage, phi29 infects bacteria and has an outer protein shell that protects its DNA as it is transferred from host to host. The shell, or capsid, withstood significant prodding without breaking, the scientists report. Just tens of nanometers wide, the shell is resilient enough to endure the pressure associated with packing DNA inside of it and withstands being deformed (see image) up to 30 percent before rupturing.

The capsid thus provides both a chemical shield and mechanical protection for its contents. In a report published online today by the Proceedings of the National Academy of Sciences the team concludes that "these biological construction principles suggest possible approaches for man-made nanoscale containers."