Method for characterizing sulfated glycoproteins in a glycosylation site-specific fashion, using ion pairing and tandem mass spectrometry

Structural analysis of sulfated glycans is essential in understanding their biological significance. Here, we present a new approach to characterize sulfated glycans present on glycoproteins. The analysis is performed on glycopeptides, so information about the sulfated species is obtained in a glycosylation site-specific manner. This method employs an ion-pairing reagent to stabilize the SO3 group of the glycopeptide, allowing useful information to be obtained during MS/MS experiments. The amount of structural information obtained from (+)ESI-MS/MS of the ion-pair complexes for sulfated glycopeptides of equine thyroid stimulating hormone is compared with information obtained by (-)ESI-MS/MS of the underivatized, sulfated glycopeptides. The results indicate that this new method provides detailed insights into the sequence, branching, and type of N-glycans present, compared to analysis via (-)ESI-MS/MS.