Methods for routine sequencing of carbohydrates lag behind those for sequencing nucleic acids and proteins. The lack of such methods makes fully characterizing carbohydrates difficult. Sequencing a carbohydrate is a challenge because many of the sugar building blocks are isomers of one another, making it hard to distinguish between them, and the stereochemistry of glycosidic bonds connecting the sugars must be characterized to fully analyze the carbohydrate’s structure.Reseachers led by Isabelle Compagnon of the University of Lyon report a hybrid method that allows them to sequence carbohydrates by combining infrared laser spectroscopy with mass spectrometry (Nat. Commun. 2017, DOI: 10.1038/s41467-017-01179-y). They break carbohydrates into monosaccharide fragments in the mass spectrometer with gas collisions. Those fragments are then further dissociated with IR photons from a tunable light source to record the IR spectra of the fragments.The researchers first used the method to analyze disaccharides. The...