Characterization of Isomeric Unsulfated Glycosaminoglycan Oligosaccharides by Mass Spectrometry/Mass Spectrometry

Abstract

Both saturated and unsaturated forms of isomeric unsulfated glycosaminoglycan (GAG) oligosaccharides, i.e., tetrasaccharides of chondroitin (CH) and hyaluronan (HA), were analyzed by electrospray ionization mass spectrometry/mass spectrometry. Although the only structural di#erence between them was the hydroxyl group at the C-4 position in N-acetylhexosamine (GalNAc or GlcNAc, respectively), given the same m/z value of precursor ions, these isomers in both their saturated and unsaturated forms could be separated by careful examination of diagnostic fragment ions in their product ion mass spectra when the relative abundances of these fragment ions were considered. In addition, the product ion mass spectrum of the unsaturated HA tetrasaccharide was compared with its linkage isomer, N-acetylheparosan tetrasaccharide. In this case, the isomers were more easily di#erentiated by comparing their characteristic spectral patterns. By adopting this approach, systematic di#erentiation of isomeric unsulfated GAG oligosaccharides should be achieved by means of fragmentation. It should also contribute widely to GAG-related biochemical and medicinal research in the future.

Sequential synthesis of chondroitin oligosaccharides by immobilized chondroitin polymerase mutants

“…The number "−2" designates deprotonation (−2H) accompanied with cleavage of the glycosidic bond because proton transfer occurs at Z and B fragment formation in the negative ion mode (mass shift rule) [29]. The m/z values observed for fragment ions between C and Y fragments having the same sugar length from saturated free oligosaccharide of nonsulfated GAG and for fragment ions between C and Z fragments from unsaturated free oligosaccharides were the same [27,30]. All the observed fragments from PA-CH oligosaccharides were distinguished from each other due to the presence of aglycon PA at their reducing ends.…”

Glycosylated platycosides: Identification by enzymatic hydrolysis and structural determination by LC-MS/MS

“…The determination of linkage positions of oligosaccharides using MS has been reported , with MS/MS spectra mainly showing fragment ions corresponding to glycosidic bond cleavages . The reducing sugar ring cleavage could aid the identification of oligosaccharide linkage positions.…”