Mass spectra of O-glycan distribution in SrtA cleaved versus noncleaved reaction products of desialylated IgG. HPLC–MS analysis of SrtA reaction products (left panel; Fc-part) and unreacted antibody (right panel) of desialylated, N-deglycosylated and reduced MAb<xxx>rRb-4H11-IgG (SrtA upper hinge) after SrtA reaction. Deconvoluted HC spectrum is shown, relative intensities of O-glycans in percentage compared to main form are indicated. Main glycosylation forms are illustrated, monosaccharide symbols follow the SNFG (symbol nomenclature for Glycans) system (PMID 26543186, Glycobiology 25:1323–1324, 2015) details at NCBI.