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. 2013 Jul 2;12(10):2981–2991. doi: 10.1074/mcp.M113.027953

Fig. 4.

Fig. 4.

Two distinct MS/MS spectra of the peptide sequence “DLDMFINASK” of the glycoprotein attractin (O75882, ATRN_HUMAN) confirmed a PO glycosite at asparagine-1198. A, The position of the nonsugar-modified asparagine within the sequence was identified by the y4/b7 ions (the precursor ion: m/z 577.2818 2+). B, The position of de-N-glycosylated asparagine (18O-incorporated aspartic acid) was identified by the 3 Da mass shift of a series of b- and y- ions (red highlight) (the precursor ion: m/z 578.7756 2+)The nomenclature of peptide fragment ions was based on previous report (45).