Assignment of hexuronic acid stereochemistry in synthetic heparan sulfate tetrasaccharides with 2-O-sulfo uronic acids using electron detachment dissociation

• Published in: International journal of mass spectrometry Vol. 390; pp. 163 - 169
• Main Authors: Agyekum, Isaac, Patel, Anish B., Zong, Chengli, Boons, Geert-Jan, Amster, I. Jonathan
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.11.2015
• Subjects: Carbohydrates; Electron detachment dissociation; Epimers; FTICR; Glycosaminoglycans; Principal component analysis; Epimers; Carbohydrates; Glycosaminoglycans; FTICR; Electron detachment dissociation; Principal component analysis
• ISSN: 1387-3806; 1873-2798
• DOI: 10.1016/j.ijms.2015.08.018

[Display omitted] •Uronic acid assignment in glycosaminoglycans is a major analytical challenge.•Ten 2-O-sulfo HS tetrasaccharides were subjected to MS/MS analysis using EDD.•B3 and Y1 ions are diagnostic of GlcA, independent of the degree of sulfation.•The ratios of the sum of diagnostic ions predict GlcA versus IdoA in all cases. 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), have 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). While 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 diagnostic ratios (DR), which can be used to confidently assign the uronic acid stereochemistry.