Differentiation of the anomeric configuration and ring form of glucosyl-glycolaldehyde anions in the gas phase by mass spectrometry: isomeric discrimination between m/z 221 anions derived from disaccharides and chemical synthesis of m/z 221 standards

Differentiation of the Stereochemistry and Anomeric Configuration for 1-3 Linked Disaccharides Via Tandem Mass Spectrometry and 18O-labeling

“…Given that the CID patterns of m/z 221 ions will be used for structural identification, spectral reproducibility is an important issue. Similar to the findings from a Paul trap instrument [33,34], we noticed that the number of ions (m/z 221) in the linear ion trap and the energy input into an ion were among the most important parameters affecting spectral reproducibility. To ensure reasonable ion statistics and avoid adverse space charge effects, the intensity of the m/z 221 ions was kept at 1× 10 6 cps before MS 3 CID.…”

“…Ion trap CID of deprotonated 1-3 linked disaccharides (m/z 341) typically generates ions at m/z 221 in trace abundance on a Paul trap instrument, and isolation or further CID of m/z 221 ions have not been achieved before [14,15,34,36]. The 4000QTRAP mass spectrometer used in this study has a unique triple quadrupole-linear ion trap configuration, offering high sensitivity due to the large capacity of the linear ion trap, and allowing either beam-type or ion trap collisional activation.…”

“…Previous studies have demonstrated that m/z 221 product ions formed from collisional activation of disaccharide anions typically consist of an intact non-reducing sugar with a 2-carbon aglycone derived from the reducing sugar [34]. Three dominant fragment peaks are commonly observed from CID of m/z 221: m/z 101, 131, and 161.…”

“…Recently, a tandem mass spectrometry approach has been developed to differentiate the stereochemistry and anomeric configuration for the non-reducing unit of hexose-containing disaccharides having any of the 16 possible stereochemical variants [33,34]. In this method, diagnostic ions at m/z 221 were formed from CID of deprotonated disaccharide ions (m/z 341).…”

“…When m/z 221 ions were further dissociated by collisional activation, disaccharides having different non-reducing sugar units and anomeric configurations showed distinct fragmentation patterns that matched synthetic glycosyl-GAs. This method was shown to be useful for assigning the stereochemistry as well as the anomeric configuration of the glycosidic bond for the non-reducing sugar in disaccharides having 1-2, 1-4, and 1-6 linkages [33,34]. However, due to the low abundance of m/z 221 ions produced from 1-3 linked disaccharides, MS 3 CID of m/z 221 ions could not be performed, and it was unclear whether the fragmentation patterns could be used for assigning either their stereochemistry or anomeric configuration.…”