FIGURE 4.

Mass spectroscopic analysis revealed an unexpected O-linked glycosylation modification at threonine 5 of the anti-IL17A peptide. A, TOF-MS deconvoluted spectra of Q-GSE21-LC and Q-GSE21-LC-T5A, as described under “Experimental Procedures.” B, MS/MS fragmentation of the anti-IL17A trypsin generated peptide, after β-elimination and Michael addition with ethylamine, identified the site of O-linked glycosylation to be at position threonine 5, as described under “Experimental Procedures.”