Virus purification

This chapter describes the proven methods of purifying enveloped versus non-enveloped viruses and labile versus stable viruses as these properties constitute important differences in the methods. The chapter also discusses those criteria used by various laboratories for determining the degree of purity achieved in virus preparations. Viruses need to be purified for many studies in which properties or structure of the virus must be distinguished from those of the host cells or culture medium, such as analyses of structure of viral polypeptides and function of membrane glycoproteins. Ultracentrifugation is the usual technique of choice for the purification of particles of defined size from their contaminating materials. Caesium chloride is one of the materials of choice used for the purification of viruses by a technique referred to as buoyant density-gradient sedimentation, isopycnic centrifugation, or equilibrium density gradient centrifugation.