Identification of Anomericity and Linkage of Arabinose and Ribose through Collision-Induced Dissociation

Arabinose and ribose are two common pentoses that exist in both furanose and pyranose forms in plant and bacteria oligosaccharides. In this study, each pentose isomer, namely alpha-furanose, beta-furanose, alpha-pyranose, and beta-pyranose, was first separated through high-performance liquid chromatography followed by an investigation of collision-induced dissociation in an ion trap mass spectrometer. The major dissociation channels, dehydration and cross-ring dissociation, were analyzed by using high-level quantum chemistry calculations and transition state theory. The branching ratio of major dissociation channels was governed by two geometrical features: one being the cis or trans configuration of O1 and O2 atoms determining dehydration preferability and the other being the number of hydroxyl groups on the same side of the ring as the O1 atom determining the preferability of cross-ring dissociation. The relative branching ratios of the major channels were used to identify anomericity and the linkages of arabinose and ribose. Arabinose in the beta-configuration and ribose in the alpha-configuration are predicted to have larger relative dehydration branching ratios than arabinose in the alpha-configuration and ribose in the beta-configuration, respectively. Arabinose and ribose at the reducing end of oligosaccharides with 1 -> 2 (pyranose and furanose), 1 -> 3 (pyranose and furanose), 1 -> 4 (pyranose only), and 1 -> 5 (furanose only) linkages are predicted to undergo X-0,X-2, X-0,X-3, (0,2)A, and (0,2)A/(0,3)A cross-ring dissociation, respectively. Application of the dissociation mechanism to the disaccharide linkage determination is demonstrated.