FIG. 2.

Treatment of TGEV cores with ionic agents. Purified cores were treated with increasing concentrations of NaCl and KCl (A) or guanidine isothiocyanate (B). For the upper left panels, the protein composition was analyzed by SDS-PAGE using 5 to 20% gradient gels and silver staining. The arrows to the right of the panel indicate the positions of TGEV structural proteins. The core structure observed by electron microscopy after negative staining (2% uranyl acetate) is shown for three representative treatments (bottom left panel). The right panel shows the percentage of the core-associated M protein after each treatment in relation to the M protein of untreated cores. The amount of each viral protein was estimated by densitometry using the N protein as an internal control.