Fig. 2.

Low-energy collision-induced dissociation mass spectra of (A) a tryptic peptide harboring autophosphorylated Tyr185 which was immunoprecipitated from tryptic digests of yeast expressing active Fyn or (B) a synthetic peptide of the same with an added stable isotope-containing mass tag on Leu187 to distinguish it from the otherwise near-identical spectrum in (A). See Supplementary Figs. 1–5 for additional validation spectra.