Figure 5.

MS/MS spectrum of a doubly charged ion, m/z = 1127.53, for Peptide C (peptide sequence: QGPPASPT₄₀₇AS₄₀₉PEPPPPEGS₄₁₈GGGGDK) treated with sialidase and O-glycanase followed by alkaline β-elimination. Y-series ions including [y7], [y10], [y13], and [y15] have a loss of 18 Da due to GAG glycan elimination at Ser₄₁₈. [Color figure can be viewed in the online issue, which is available at http://wileyonlinelibrary.com.]