Interplay of H-Bonds with Aromatics in Isolated Complexes Identifies Isomeric Carbohydrates

The tremendous isomeric diversity of carbohydrates enables a wide range of their biological functions but makes the identification and study of these molecules difficult. We investigated the ability of intermolecular interactions to communicate structural specificity of carbohydrates to protonated aromatic molecules in non-covalent complexes, isolated and cooled in the gas phase. Our study revealed that small structural differences between carbohydrate isomers of any type, including enantiomers, are accurately communicated by these interactions to aromatic molecules as detectable changes in their electronic excitation spectra. The specific response of the aromatics to the isomers of carbohydrates is fine-tuned by the interplay of the various involved non-covalent bonds. These findings enable the gas-phase identification and relative quantification of any isomers of oligosaccharides in their solution mixtures using the 2D UV-MS fingerprinting technique.