Figure 1.

(A) SDS-PAGE gel of the unfractionated S proteins (full-length and S1 subunit). Lane 1: molecular markers; lanes 2–6: S2P, S1, MS1, SF, and SN, respectively. (B) Size-exclusion chromatogram (UV detection at 216 nm) of the recombinant SARS-CoV-2 S proteins expressed in human (S2P, blue trace) and insect cells (SF, red trace). (C) Representative MS/MS spectra of the glycopeptides with a complex glycan, HexNAc₄Hex₄Fuc, at amino acid position 1074. The two peptides were cleaved from S2P by trypsin (top) and Asp-N/chymotrypsin (bottom), respectively.