FIGURE 6: Purification of secreted GST-tagged RBD. (A) Schematic overview and expected mass of the secreted RBD protein. (B) Western blot analysis with an antibody against the RBD domain. Recombinant RBD served as a positive control (p.c.). Cell, cell culture; P, pellet (10⁷ cells); S, supernatant (0.2%); asp, ammonium sulfate precipitation pellet (0.13%) and supernatant (0.13%); dia, dialysis (0.07%); ft, flow through (0.07%); wash, wash steps (0.08%); elution, eluate fractions (0.8%); all, pooled eluate; (C) SDS-PAGE analysis of the cell culture supernatant (cs), the wash, and eluate fractions of the affinity chromatography from panel B. The gel was stained with Coomassie blue.