Fig. 2.

MS/MS spectra obtained from data-dependent LC-MS/MS analysis of the peptide ion shown in Fig. 1. The exact modification type is difficult to determine because there is minimal b and y ion coverage for the N-terminal portion of the peptide that is modified; however, the +1-Da shift for y₂₄²⁺ provides further evidence for the sequence ^@YASICQQN^#GIVPIVEPEILPDGDHDLKR (where @ and # indicate carbamoylation of the N terminus and deamidation, respectively) determined by the accurate mass measurement presented in Fig. 1.