Virions are isometric, non enveloped, c. 30 nm in diameter, with a rounded contour, and
prominent surface structure, with clustering of coat protein subunits in pentamers and
hexamers. The capsid of tymoviruses is made up of 20 hexameric and 12 pentameric
subunits arranged in a T = 3 icosahedron and the RNA appears to be at least partially ordered
in an icosahedral arrangement in the centre of the protein shell.
Physicochemical and