Building up key segments of N-glycans in the gas phase:: Intrinsic structural preferences of the α(1,3) and α(1,6) dimannosides

The intrinsic conformer specific vibrational spectra of two important subunits of the core pentasaccharide of Winked glycans, the alpha(1,3) and alpha(1,6) dimannosides, have been recorded in the gas phase. Coupling these measurements with a computational exploration of their conformational landscapes has enabled their conformational assignment and has identified characteristic vibrational signatures associated with particular conformational families-including those that do or do not display inter-ring hydrogen bonding across the glycosidic linkage. In addition, the IR spectra of the monosaccharide moieties provide benchmarks, through which the conformational assignments can be refined. This introduces a general concept of modularity and secondary structure in oligosaccharides-essential for the success of similar studies on larger oligosaccharides in the future.