Structure of isometric viruses containing nonidentical polypeptide chains

The theory of Caspar and Klug (1962) for the structure of isometric viruses has been generalized to the case in which the identical repeating unit is composed of n nonidentical polypeptide chains. This modified theory accounts for the structure of picornaviruses, the lambda phage head, cowpea mosaic virus, and phiX174, while at the same time conserving the principle of having identical subunits in identical environments. Furthermore, the modified theory suggests amending the triangulation number to T[n] for capsids with n nonidentical polypeptide chains as the repeating unit.

Diffusion constant and dimension of bacteriophage phi X174 as determined by self-beat laser light spectroscopy and electron microscopy

The diffusion constant of bacteriophage phiX174 was determined by laser light self-beat spectroscopy. The method allows one to establish the diffusion constant in comparatively short time and with high accuracy. From the diffusion constant D(37) = 1.96 +/- 0.08 x 10(-7) cm(2)/s, the size of the virus particles within their aqueous milieu can be calculated. For phiX174, a diffusional diameter of 31.4 +/- 1.0 nm was found, in good agreement with measurements of diameters of freezeetched (32.3 +/- 1.8 nm) and negatively stained particles (33.8 +/- 2.1 nm), provided that the entire spikes of the virion are included. Other isometric viruses may show a complex interaction of the virion with the surrounding water and its ions.