Observations on the Structure of Particles of White Clover Mosaic Virus

X-ray diffraction studies of oriented specimens of white clover mosaic virus particles suggest that the particles have a helical structure of pitch 3.25 ± 0.05 nm. The X-ray diffraction patterns indicate that there is an integral, or near integral, number of subunits in four turns of the helix and that the number is 4q + 3. Optical diffraction from micrographs of the virus particles are in agreement with the X-ray results and suggest that the number of subunits in four turns is close to 27.