Fig. 2. Stability and yield are higher for immunogens than WT RBD.

(A) All five immunogens expressed at higher levels than WT RBD and eluted as monomers by size exclusion chromatography (SEC). (B) SDS–polyacrylamide gel electrophoresis confirmed the high purity and yield of RBD immunogens. (C) Differential scanning fluorimetry indicated that four immunogens have higher thermostability than WT RBD. (D) T_m and purification yield averages and SDs from three separate purifications.