on 08-03-201207:26 AM - edited on 10-15-202111:14 AM by Closed Account
Singh C, Zampronio C, Creese A, Cooper HJ. J Proteome Res. 2012 Sep 7;11(9):4517-25. Large scale mass spectrometry analysis of N-linked glycopeptides is complicated by the inherent complexity of the glycan structures. Here, we evaluate a mass spectrometry approach for the targeted analysis of N-linked glycopeptides in complex mixtures which does not require prior knowledge of the glycan structures or pre-enrichment of the glycopeptides. Despite the complexity of N-glycans, the core of the glycan remains constant comprising two N-acetylglucosamine and three mannose units. Collision-induced dissociation (CID) mass spectrometry of N-glycopeptides results in the formation of the N-acetylglucosamine (GlcNAc) oxonium ion and a [Mannose+GlcNAc] fragment (in addition to other fragments resulting from cleavage within the glycan). In ion-trap CID, those ions are not detected due to the low m/z cut-off; however they are detected following the beam-type CID known as higher energy collision dissociation (HCD) on the orbitrap mass spectrometer. The presence of these product ions following HCD can be used as triggers for subsequent electron transfer dissociation (ETD) mass spectrometry analysis of the precursor ion. The ETD mass spectrum provides peptide sequence information, which is unobtainable from HCD. A Lys-C digest of ribonuclease B and trypsin digest of immunoglobulin G were separated by ZIC-HILIC liquid chromatography and analysed by HCD product ion-triggered ETD. The data were analysed both manually and searched against protein databases by commonly-used algorithms. The results show that the product ion triggered approach shows promise for the field of glycoproteomics and highlight the requirement for more sophisticated data mining tools.