Characterizing the Dynamics of Solvated Disaccharides with In-Electrospray Ionization Hydrogen/Deuterium Exchange-Mass Spectrometry

Carbohydrates have various biological functions that are based on their structures. However, the composition and the glycosidic-bond linkage and configuration of carbohydrates present challenges for their characterization. Furthermore, isomeric features contribute to the formation of intramolecular hydrogen bonds, which influence the flexibility and dynamics of carbohydrates. Hydrogen/deuterium exchange-mass spectrometry (HDX-MS) enables the analysis of protein dynamics by monitoring deuterium labeling after HDX for different lengths of time. In-electrospray ionization (in-ESI) HDX-MS has been used to rapidly label solvated carbohydrates with labeling occurring during desolvation of ESI droplets. Therefore, HDX-labeling times can be altered by changing the spray-solvent conductivity, which changes the initial size of ESI droplets and their resulting lifetimes. Here, we utilize in-ESI HDX-MS to characterize nine isomeric disaccharides with different monosaccharide compositions and glycosidic-bond linkages and configurations. We compared both the relative D-uptake of isomers at individual conductivities, or HDX-labeling times, and the trends associated with labeling at multiple conductivities. Interestingly, the relative D-uptake trends were correlated to isomeric features that affect disaccharide flexibility, including formation of intramolecular hydrogen bonds. Among the isomeric features studied, linkage was observed to have a significant influence on relative D-uptake with (1-3)-linked disaccharides having more change in relative D-uptake with changing conductivity compared to other linkages. Overall, this research illustrates how in-ESI HDX-MS can be applied to structurally characterize disaccharides with distinct isomeric features. Furthermore, this work shows that in-ESI HDX-MS can be used to monitor the dynamics of solvated molecules with rapidly exchanging functional groups.