Figure 5.

Tandem spectrum of the [M + H]⁺² ion at m/z 955.03 of tryptic peptides from a 70 kDa iPLA₂β digest. An aliquot of the tryptic digest analyzed by MALDI/TOF/MS, illustrated in Figure 4, was analyzed by LC/ESI/MS, and the [M + H]⁺² ion at m/z 955.03 was analyzed by tandem MS. The observed tandem spectra of the [M + H]⁺² ion at m/z 955.03 produced by CAD is displayed and include the y- and b-series ions expected from the peptide sequence, illustrated in the inset. Inset: The expected peptide fragmentation patterns of the candidate peptide LVNTLSSVTNLFSNPFR with the [M + H]⁺² m/z of 955.03. The expected masses of b- and y-series ions and their deviation from observed masses are listed, respectively, above and below the expected m/z values.