Electron Capture Dissociation of Triantennary Complex-Type N-Glycosylated Peptides: A Case of Suppressed Peptide Backbone Cleavage

Abstract

We investigated the electron capture dissociation (ECD) of triantennary complex-type N-glycosylated peptides prepared from bovine fetuin. Previous reports on Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) suggested that ECD is an advantageous method for structural characterization of glycopeptides, because it can cleave the N-Cα bond on the peptide backbone while retaining the labile glycosidic bonds. We present here new data from ECD which resulted in the degradation of the glycan structure prior to any backbone cleavage. Based on the ECD experiment on deglycosylated samples, the character of the peptide backbone sequence, which contains carbamoylmethylated cysteine residue, seemed to prevent extensive N-Cα bond cleavage. It appears that more basic investigations are necessary to promote practical use of ECD for structural characterization of complex glycopeptides because each type of glycopeptide exhibits particular fragmentation patterns.