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. 2017 Feb 8;16(4 Suppl 1):S42–S53. doi: 10.1074/mcp.M116.066035

Fig. 4.

Fig. 4.

De novo identification of glycopeptides from a whole C. parvum oocyst lysate. A, Base peak and extracted oxonium ion chromatograms from a reversed phase C18 separation. The top trace shows the base peak chromatogram from the MS. The middle and bottom chromatograms are extracted oxonium ion chromatograms (XIC) from the 35-V HCD MS/MS spectra, corresponding to m/z 204.08 (HexNAc) and m/z 366.13 (HexNAc-Hex), respectively. The carat located at 15 min. indicates the time point for recording of the MS/MS spectrum shown in Fig. 4B and 4C. B, 35-V HCD MS/MS spectrum of an N-glycosylated peptide: NSTTEVR modified with Hex6HexNAc2, [M + 2H]2+ m/z 1092.9426. Prominent glycosidic bond fragmentation is observed, delineating the sequence of the glycan. C, Peptide sequence of the aglycon. Lower intensity y-ion peptide backbone fragments are observed in the same spectrum. Peptide fragment ion assignments are shown on this magnified view; these extend from y1 (Arg) at m/z 175.1189 to the complete aglycon, m/z 806.3992, defining the complete peptide sequence as NSTTEVR.