FIG. 3.

Treatment of TGEV cores with nonionic agents. Purified cores were treated with increasing concentrations of a nonionic detergent, Triton X-100 (A) or 2-mercaptoethanol (B). The upper left panel shows that the protein composition was analyzed by SDS-PAGE using 5 to 20% gradient gels and silver staining. The positions of the TGEV structural proteins are indicated (arrows to the right of panel). The core structure is shown by electron microscopy of negatively stained specimens (2% uranyl acetate) after three representative treatments (bottom left). The percentage of the core-associated M protein after each treatment in relation to the M protein of untreated cores is also shown (right panel). The amount of virus protein was estimated by densitometry using the N protein as an internal control. The effect of detergent on core structure could not be evaluated when concentrations of Triton X-100 higher than 2% were used, due to interference with electron microscopy.