Fig. 6.

The L75 peptide is only expected to result from GluC-digestion following PNGaseF-digestion of a glycosylated N74-containing peptide. MS1 spectra of the L75 peptide identified in spectra collected using CD16a V158 following PNGaseF digestion in either ¹⁶O (A) or ¹⁸O (B) water. The positions of monoisotopic peaks for each species are indicated. (C–D) MS2 spectra of the major species from panels A and B, respectively, indicate the ion composition as well as demonstrate ¹⁸O incorporation in the C-terminal Glu residue.