Abstract
The structure of the iridescent virus type I was examined using negative staining technique. After storage for 1 to 2 months at 4 °C or treatment with chloroform, the icosahedral capsid breaks up into its structural elements pentagons and triangles, each consisting of 31 and 55 subunits respectively. When such a preparation is centrifuged through a linear sucrose gradient (10 to 40%), 5 zones are revealed. An electron microscopic analysis showed the following distribution of the material (from top to bottom of the tube): (1) free triangles; (2) associated triangles, core; (3) partially disrupted virions; (4) free intact virus particles; (5) virus aggregates.
A model for iridescent virus type I capsid is proposed, consisting of 12 pentagons (372 subunits) and 20 triangles (1100 subunits). The total number of subunits is 1472.