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Figure 3 | Proteome Science

Figure 3

From: Phosphoproteomes of Strongylocentrotus purpuratus shell and tooth matrix: identification of a major acidic sea urchin tooth phosphoprotein, phosphodontin

Figure 3

Identification of the phosphorylation site of peptide NVAEAAGLSSNEVTQVK. Similar to the spectrum in Fig. 2, this spectrum shows the complexity to be expected from fragmentation of a relatively long peptide by multistage activation. However, the presence of extended series of y and b ions and the accurate mass of the intact peptide measured in the orbitrap enabled the unequivocal identification of the sequence. The phosphorylation site is identified by the increase of 80Da in the y-ion series starting with y8 and the absence of such an increase in b-ions up to b9. Loss of H3PO4, H2O, and NH3 is indicated by -P, -18, and -17, respectively. The neutral loss of water and NH3 is frequently observed upon fragmentation of peptides containing Asn, Gln, Glu, Ser and Thr, also contained in this peptide.

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Proteome Science

ISSN: 1477-5956