Collision-induced dissociation of sodiated glucose, galactose, and mannose, and the identification of anomeric configurations

Abstract

Collision-induced dissociation of sodiated α-glucose, β-glucose, α-galactose, β-galactose, α-mannose, and β-mannose was studied using electronic structure calculations and resonance excitation in a low-pressure linear ion trap. We made an extensive search of conformers and transition states in calculations to ensure the transition state with the lowest barrier height for each dissociation channel could be located. The major dissociation channels, in addition to desodiation, are cross-ring dissociation and dehydration. Cross-ring dissociation starts with H atom transfer from the O1 atom to the O0 atom, followed by the cleavage of the C1-O0 bond. Dehydration of the anomer with O1 and O2 atoms in the cis configuration involves the transfer of an H atom from the O2 atom to the O1 atom, followed by the cleavage of the C1-O1 bond. In contrast, dehydration of the anomer with O1 and O2 atoms in the trans configuration mainly occurs through H atom transfer from the O3 or O2 atom to the O1 atom for glucose, from the O3 or O4 atom to the O1 atom for galactose, and from the O4 or O2 atom to the O1 atom for mannose, followed by the cleavage of the C1-O1 bond. The dehydration barrier heights are lower than those of cross-ring dissociation for cis anomers, but higher than those of cross-ring dissociation for trans anomers. The relative barrier heights from calculations are consistent with the experimental measurements of branching ratios. Both computational and experimental results show that the branching ratio of dehydration can be generalized as a simple rule for rapidly identifying the anomeric configurations of these monosaccharides.

Automatically Full Glycan Structural Determination with Logically Derived Sequence Tandem Mass Spectrometry

“…Identifications of monosaccharides calculations have revealed that the water elimination barriers of the O1 and O2 atoms in the cis configuration of the sodium adduct was substantially smaller than that in the trans configuration. 41,42 We found lithium adducts have the similar properties. Therefore, the CID spectrum with high ion m/z 169 intensity, representing a high branching ratio in the dehydration reaction, can be assigned to the anomer that has the O1 and O2 atoms in the cis configuration (α-glucose, α-galactose, and β-mannose).…”

“…39,40 In this study, we extended the use of cross ring fragments to identify the linkage positions and anomeric configurations of disaccharides containing glucose, galactose, mannose, GalNAc, and GlcNAc based on the understanding of dissociation mechanism. [41][42][43] The third one is the capability to dissociate selective chemical bond and generate the chosen monosaccharide or disaccharide for subsequent structural determination. We have developed a procedure, namely logically derived sequence (LODES) for tandem MS, to generate the desired monosaccharide or disaccharide by collision induced dissociation of oligosaccharide sodium adducts.…”

Automatic Full Glycan Structural Determination through Logically Derived Sequence Tandem Mass Spectrometry

“…A major difference between the CID spectra of two anomers of a given hexose (e.g., Figure B and C for α‐ and β‐glucose, respectively) is the relative intensity of ion m / z 169, which represents H 2 O elimination. High‐level quantum chemistry calculations have revealed that the water elimination barriers of the O1 and O2 atoms in the cis configuration of the sodium adduct were substantially smaller than that in the trans configuration . We found that lithium adducts had similar properties.…”

“…These crossed‐ring fragmentation patterns (e.g., loss of m / z 120, 90, 60) were explained by the retro‐aldol reaction . Recent high‐level quantum chemistry calculations confirmed that the retro‐aldol reaction, starting from the O1 atom of the sugar at the reducing end is the dominant mechanism of cross‐ring dissociation. This mechanism does not depend on the orientation of hydroxyl groups or the sugar connecting to the hydroxy groups at the nonreducing end.…”

“…However, information on the anomeric configuration and monosaccharide constituents was not available. In this study, we extended the use of cross‐ring fragments to identify the linkage positions and anomeric configurations of disaccharides containing glucose, galactose, mannose, GalNAc, and GlcNAc based on an understanding of the dissociation mechanism . The third one is the capability to dissociate selective chemical bonds and generate the chosen mono‐ or disaccharide for subsequent structural determination.…”