1. Phosphopeptide sequencing by MALDI-TOF/TOF of the C-terminal tail of AtPIP2;1.A, MS/MS spectrum of singly phosphorylated 277SLGSFRSAANV287 (m/z ). y7 and y8 ions allowed identification of Ser280 as the phosphorylated residue.
Phosphopeptide sequencing by MALDI-TOF/TOF of the C-terminal tail of AtPIP2;1.A, MS/MS spectrum of singly phosphorylated 277SLGSFRSAANV287 (m/z ). y7 and y8 ions allowed identification of Ser280 as the phosphorylated residue. B, MS/MS spectrum of the corresponding diphosphorylated peptide (m/z ). y4, y5, y7, and y9 ions allowed identification of the two phosphorylated residues as Ser280 and Ser283. *, fragment ions arising from loss of phosphoric acid (−98 Da). pS, phosphorylated serine; [MH]+, precursor ion; [MH − P]+, precursor ion with a loss of one metaphosphoric acid (-80 Da); [MH − P − 18]+, precursor ion with a loss of one phosphoric acid (−98 Da); [MH − 2P − 18]+, precursor ion with a loss of one metaphosphoric acid (−80 Da) and one phosphoric acid (−98 Da); [MH − 2P −2 × 18]+, precursor ion with a loss of two phosphoric acids (−196 Da).
Sodana Prak et al. Mol Cell Proteomics 2008;7:
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