Published online by Cambridge University Press: 14 March 2011
Two crystal forms, orthorhombic and cubic, of satellite tobacco mosaic virus have been investigated. Atomic force microscopy showed that the orthorhombic crystals were characterized by a high density of point defects, while the cubic crystals were practically defect-free. Nonetheless, orthorhombic crystals diffract to a high resolution of 1.8 Å while the cubic crystals diffract to only about 4 to 6 Å resolution. Differences in the properties of viruses incorporated into the two crystal structures were demonstrated by growth kinetics studies. It appears that physical and chemical treatments applied to protein and virus solutions during their extraction and purification introduce a variety of specific structural changes and that these alterations may then affect the diffraction properties of resultant macromolecular crystals.