Some Observations on the Structure of Potato Virus X

The flexible elongated plant virus, potato virus X, has been studied by a number of physical and physical-chemical methods. Here we wish to compare the results of these studies and to make some observations on the structure of the virus which these studies suggest.

X-ray diffraction studies of potato virus X were first made by Bernal & Fankuchen (1941), who obtained diffraction patterns suggesting a periodicity along the virus particle of 33 Å. Later X-ray studies (Tollin et al. 1967) showed that this periodicity varied from 33 to 36 Å depending on the amount of water in the specimen. A dry specimen of potato virus X with improved orientation has been obtained in an identical fashion to that for narcissus mosaic virus (Tollin, Wilson & Young, 1968). The X-ray diffraction pattern (Pl. 1) can be interpreted as being due to a helical arrangement of subunits with a pitch of 33 to 36 Å, depending on water content.