title: Single Stage Tandem Mass Spectrometry Assignment of the C-5 Uronic Acid Stereochemistry in Heparan Sulfate Tetrasaccharides using Electron Detachment Dissociation.
abstract: The analysis of heparan sulfate (HS) glycosaminoglycans presents many challenges, due to the high degree of structural heterogeneity arising from their non-template biosynthesis. Complete structural elucidation of glycosaminoglycans necessitates the unambiguous assignments of sulfo modifications and the C-5 uronic acid stereochemistry. Efforts to develop tandem mass spectrometric-based methods for the structural analysis of glycosaminoglycans have focused on the assignment of sulfo positions. The present work focuses on the assignment of the C-5 stereochemistry of the uronic acid that lies closest to the reducing end. Prior work with electron-based tandem mass spectrometry methods, specifically electron detachment dissociation (EDD), have shown great promise in providing stereo-specific product ions, such as the B3´-CO2, which has been found to distinguish glucuronic acid (GlcA) from iduronic acid (IdoA) in some HS tetrasaccharides. The previously observed diagnostic ions are generally not observed with 2-O-sulfo uronic acids or for more highly sulfated heparan sulfate tetrasaccharides. A recent study using electron detachment dissociation and principal component analysis revealed a series of ions that correlate with GlcA versus IdoA for a set of 2-O-sulfo HS tetrasaccharide standards. The present work comprehensively investigates the efficacy of these ions for assigning the C-5 stereochemistry of the reducing end uronic acid in 33 HS tetrasaccharides. A diagnostic ratio can be computed from the sum of the ions that correlate to GlcA to those that correlate to IdoA. Graphical Abstract ᅟ.
authors.affiliation: Department of Chemistry, University of Georgia, Athens, GA, 30602, USA.
authors.forename: Isaac
authors.initials: I
authors.lastname: Agyekum
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia, Athens, GA, 30602, USA.
authors.forename: Chengli
authors.initials: C
authors.lastname: Zong
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia, Athens, GA, 30602, USA.
authors.forename: Geert-Jan
authors.initials: GJ
authors.lastname: Boons
authors.affiliation: Department of Chemistry, University of Georgia, Athens, GA, 30602, USA. jamster@uga.edu.
authors.forename: I Jonathan
authors.identifier: 0000-0001-7523-5144
authors.initials: IJ
authors.lastname: Amster
keywords: Electron detachment dissociation; FTICR; Glycosaminoglycans; Heparan sulfate; Stereochemistry; Uronic acids