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Table 3 Unique fragment ions used to quantify phosphorylation sites

From: Insulin-stimulated phosphorylation of protein phosphatase 1 regulatory subunit 12B revealed by HPLC-ESI-MS/MS

Start Stop Peptide sequence Phosphorylation site Product ion ( m/z )* Mass (Da)
28 38 GpSLTEQEPAER Ser29 y8 (+1) 959.40
     y9 (+1) 1072.50
501 511 KLNpSTSDIEEK Ser504 b4 (+1) 523.23
     y7 (+1) 821.39
645 659 pSpTQGVTLTDLQEAER Ser645/Thr646 b2 (+1) 269.05
     b3 (+1) 397.11
     b4 (+1) 454.13
     b5 (+1) 553.20
     y10 (+1) 1175.59
     y11 (+1) 1274.66
     y12 (+1) 1331.68
     y13 (+1) 1459.74
711 720 pSLDEEPICHR Ser711 y6 (+1) 754.37
     y7 (+1) 883.41
     y8 (+1) 998.44
755 773 FSVPDpSESSETTTNTTTAK Ser760 b7 (+1) 842.30
     y12 (+1) 1241.59
     y13 (+1) 1370.63
837 853 LEpSGGSNPTTSDSYGDR Ser839 b3 (+1) 410.10
     y12 (+1) 1299.50
     y13 (+1) 1356.60
     y14 (+1) 1413.60
  1. * m/z, mass-to-charge ratio.
  2. Since Scaffold PTM analysis indicated that only Ser760 or Ser762 is phosphorylated on this peptide, unique fragment ion selection was based on the comparison between pSer760 and pSer762.