A virus has a girth of only a few thousand atoms –so small, they can infect bacteria. These microscopic entities are protected by a protein shell or capsid, which grows and changes shape as the virus matures. Seen by Atomic Force Microscopy, young HK97 viruses – similar to the cold sore virus Herpes simplex – are pentagon-shaped (top left). They mature into football-like structures (bottom left). Arranged in a regular pattern of hexagons and pentagons, shell protein connections or cross-links increase with age. CGI (yellow and blue hexagons) highlights the changing structure (right-hand images). To test viral vulnerability researchers prodded capsids with tiny probes. While the more mature HK97 virus has chainmail-like armour its extra cross-links add surprisingly little strength. However, they do provide durability – the younger capsids disintegrate after relatively few pokes. Identifying weak points in the viral life cycle will inform the design of effective drugs.
Written by Alice Lighton
BPoD stands for Biomedical Picture of the Day. Managed by the MRC London Institute of Medical Sciences (the new name for the MRC Clinical Sciences Centre) the website aims to engage everyone, young and old, in the wonders of biomedicine. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.