Fig. 5

Secondary structure characterization of RBD forms by CD spectroscopy. The spectra were recorded in pure water A RBD and B RBD-P and in a 50% (v/v) TFE aqueous mixture, C RBD and D RBD-P. Secondary structure contents (αH, α helix; βS, β strand; O, other) were calculated from a deconvolution analysis of the CD spectra with the BeStSel webserver. Black circles are experimental spectra, lines correspond to the best-fit spectra, and residuals between calculated and experimental data are shown with asterisks. High-resolution chromatography of the RBD-P and RBD antigens on an Xbridge Protein BEH C4 reverse phase column (E). The interest components were eluted at 39.6 min, in a gradient from 0 to 60% acetonitrile in 60 min, with a flow of 0.8 mL/min, and injected 25 μg