The sharp edges of a virus
Biophysicists from the FOM Foundation, the VU University Amsterdam and the University of California in Los Angeles have confirmed a nine-year-old prediction about why viruses are often so angular. Most viruses are not round but have an icosahedral structure like a 20-sided dice. The virus shell consists of proteins that are arranged in a honeycomb-like pattern. As these proteins are folded up tensions arise at the corners. The researchers have now demonstrated that these tensions are responsible for the angular shape of viruses. They published their results 19 October in Physical Review Letters.
Nanotechnology
Viruses are natural nanoparticles full of genetic material. Biophysicists at trying to verify their structure as a source of inspiration for the development of other nanoparticles. These can be used for example, in hospitals or industry for the transport and delivery of certain substances to a specific location. Many models already exist that can explain the shape of viruses but are these also correct? The researchers focused on a highly promising but previously untested theory from 2003, which predicts that the corners of viral nanoparticles are under tension and therefore ensure that the viruses assume their characteristic icosahedral shape.
Filing down edges
The researchers had to develop an indirect method to demonstrate this tension, as it cannot be measured directly. They compared the angular viruses with viruses without edges (type of football), which they produced by using biochemical techniques to 'file down' the sharp edges. They tested the stiffness of these viral shells by squashing the virus particles with a minute needle of an atomic force microscope. That proved to be more difficult in the case of the angular viruses that were found to be far stiffer. This mechanical difference can only be explained by assuming that the viruses are under tension.
With this research, FOM workgroup leader Prof.dr. Gijs Wuite and former FOM postdoc Dr. Wouter Roos, supported by the simulations of their American colleague, have demonstrated that existing ideas are very applicable for describing viruses. This marks an important step forwards, as this knowledge can now be used directly on viruses and other nanoparticles.
Reference
Unlocking Internal Pre-stress from Protein Nanoshells
W.S. Klug, W.H. Roos, G.J.L. Wuite
DOI: 10.1103/PhysRevLett.109.168104
Further information
Wouter Roos +31 (0)20 598 3974
http://www.few.vu.nl/~wroos/