Figure 3 .

On-chip ppGalNAc-Ts assay on the S protein peptide microarray(A) Scheme of the on-chip ppGalNAc-Ts assay. The peptide microarray contains short peptides covering the full length of the S proteins. ppGalNAc-T transfers GalNAc from UDP-GalNAc to the targeted Ser/Thr residues, and the resulting O-GalNAc glycan is immobilized with biotin-labeled VVA lectin and Cy5-labeled streptavidin. The signal was analyzed using a microarray scanner. (B) Overview of S protein peptide glycosylation modified by T1/T2/T3/T6 and (C) heatmap of glycopeptides with a signal-to-noise (S/N) intensity greater than 5.0.