Localization of proteins on viral nucleocapsids using immunoelectron microscopy

We have described an indirect immunoelectron microscope method to localize individual proteins on viral nucleocapsids using monoclonal antibodies and colloidal gold‐conjugated second antibodies. The procedure provides good binding and retention of antibodies, good resolution(< 24nm), and negligible nonspecific binding of antibodies to the background. In addition, the method is compatible with both negative and positive staining, the two staining procedures commonly used to derive ultrastructural information on viral chromosomes. We have illustrated the procedure by localizing the NP (nucleoprotein, ≈︁ 2,600 copies) and P (polymerase‐associated protein, ≈︁ 300 copies) proteins on the nucleocapsid of Sendai virus, a paramyxovirus.