| Popis: |
We used pseudo-triple-stage tandem MS to rapidly differentiate terminal α(2,3)- and α(2,6)-linked sialic acids of glycopeptides and native glycans. The precursor ions generate important diagnostic fragments to distinguish different terminal linked isomeric glycans and glycopeptides based on collision-induced dissociation (CID). The diagnostic ions include hexose linked with N-acetylhexosamine residues, sialic acid with the loss of water, and sialic acid residues. Their values of mass-to-charge ratio (m/z) are at 366.14, 274.09, and 292.10, respectively. The relative intensity ratios (RIR) were calculated by the intensity of signals at m/z 274.09 and 292.10 divided by the intensity of the signal at m/z 366.14. Under optimal conditions of an in-source fragmentation voltage of 70 V and a normalized collision energy of 30 %, the difference in RIR of diagnostic ions between terminal α(2,3)-linked sialic acid of glycopeptide (1.3) and terminal α(2,6)-linked sialic acid of glycopeptide ( |
