Mass Spectrometry Characterization of Branched Glycopolymers

Synthetic carbohydrates and carbohydrate-based polymers are increasingly used for the investigation of glycopolymer-protein interactions and tested for pharmaceutical and medical applications. It has been shown that the usefulness of glycopolymers depends on the spatial arrangement of the sugar units in the molecular structure. Creating and identifying specific structures are important in the production of glycopolymers for medical uses. Synthetic glycopolymers with the same compositions can have various architectures, including branched, dendric and comb-shaped. This complexity creates a challenge in deducing their structures. The development of glycotechnology and the potential applications of synthetic glycopolymers have inspired researchers to develop new methods for the characterization of sugar-containing polymers. In this work a new analytical approach for the precise structural characterization of glycopolymers is reported. It starts with matrix-assisted laser desorption ionization (MALDI) mass spectrometry to obtain information about molecular weights and distributions of the glycopolymers. The various possible structures with the same composition are subsequently identified based on collisionally activated dissociation (CAD) tandem mass spectrometry (MS2) studies. The characteristic elimination of bromomethane molecule (shown in Figure) provides convincing evidence of monomer connectivity, which enables the characterization of the branching architectures. The glycopolymer structures deduced this way are corroborated by comparing experimental collision cross-sections from traveling-wave ion-mobility mass spectrometry (TWIM-MS) results with theoretical values obtained from molecular dynamics