ABSTRACT
The present work focuses on the assignment of uronic acid stereochemistry in heparan sulfate (HS) oligomers. The structural elucidation of HS glycosaminoglycans is the subject of considerable importance due to the biological and biomedical significance of this class of carbohydrates. They are highly heterogeneous due to their non-template biosynthesis. Advances in tandem mass spectrometry activation methods, particularly electron detachment dissociation (EDD), has led to the development of methods to assign sites of sulfo modification in glycosaminoglycan oligomers, but there are few reports of the assignment of uronic acid stereochemistry, necessary to distinguish glucuronic acid (GlcA) from iduronic acid (IdoA). Whereas preceding studies focused on uronic acid epimers with no sulfo modification, the current work extends the assignment of the hexuronic acid stereochemistry to 2-O-sulfo uronic acid epimeric tetrasaccharides. The presence of a 2-O-sulfo group on the central uronic acid was found to greatly influence the formation of B3, C2, Z2, and Y1 ions in glucuronic acid and Y2 and 1,5X2 for iduronic acid. The intensity of these peaks can be combined to yield a diagnostic ratios (DR), which can be used to confidently assign the uronic acid stereochemistry.
ABSTRACT
Sulfated polysaccharides and their oligosaccharide components play an important biological role in physiological and pathophysiological processes. Glycosaminoglycans, such as heparin, are currently used as pharmaceutical agents to control coagulation. Moreover, there arc intensive efforts in developing rapid approaches for the analysis of such bioactive carbohydrates to assess their pharmacological activity and in glycomic applications. Soft ionization methods of mass spectrometry have been applied with recent success in the analysis of sulfated carbohydrates. This review will examine the application of mass spectrometry in the compositional analysis and structural characterization of these important highly charged molecules.
