FIGURE 5.

MS/MS spectrum assigned to the triply charged CP43 peptide, ³⁶³AP(W*)LEPLRGPNGLDLSR³⁷⁹. The labels in the figure indicate the N-terminal amino acids for the b-fragments and the C-terminal amino acids for the y-fragments. W is boldface because this residue carries a +32 m/z modification. The mass shift of +32 m/z can be unambiguously assigned to Trp-365 due to the y²⁺-ion and b-ion series. All relevant signals in the MS/MS spectra, which are complex due to the presence of singly, doubly, and triply charged fragment ions, can be explained by the peptide sequence.