MS/MS spectrum of multiple esterified glutamic acid residues.

Abstract

(A) Two MS/MS spectra of HC 378–399 with identical m/z showing the esterification at E387 and E389 differentiated by distinct y11+ and y12+ ions. (B) MS/MS spectra of tryptic peptide HC 300–308 showing esterification at either E300 or E301. The highest intensity singly charged ion at m/z 1556.65 is a MS/MS fragment of a peptide containing the N-acetylglucosamine remnant of a liberated N- glycan. Color code: blue square-N-acetylglucosamine; red triangle-fucose; green circle-mannose. (C) MS/MS spectrum of HC 282–295 demonstrates E290 as the site of esterification.</p