Distinguishing Oligosaccharide Isomers Using Far-Infrared Ion Spectroscopy: Identification of Biomarkers for Inborn Errors of Metabolism

Distinguishing isomeric saccharides poses a major challengeforanalytical workflows based on (liquid chromatography) mass spectrometry(LC-MS). In recent years, many studies have proposed infraredion spectroscopy as a possible solution as the orthogonal, spectroscopiccharacterization of mass-selected ions can often distinguish isomericspecies that remain unresolved using conventional MS. However, thehigh conformational flexibility and extensive hydrogen bonding insaccharides cause their room-temperature fingerprint infrared spectrato have broad features that often lack diagnostic value. Here, weshow that room-temperature infrared spectra of ion-complexed saccharidesrecorded in the previously unexplored far-infrared wavelength range(300-1000 cm(-1)) provide well-resolved andhighly diagnostic features. We show that this enables distinctionof isomeric saccharides that differ either by their composition ofmonosaccharide units and/or the orientation of their glycosidic linkages.We demonstrate the utility of this approach from single monosaccharidesup to isomeric tetrasaccharides differing only by the configurationof a single glycosidic linkage. Furthermore, through hyphenation withhydrophilic interaction liquid chromatography, we identify oligosaccharidebiomarkers in patient body fluid samples, demonstrating a generalizedand highly sensitive MS-based method for the identification of saccharidesfound in complex sample matrices.

Automated summary

The room-temperature infrared spectra of ion-complexed saccharides recorded in the far-infrared wavelength range can distinguish isomeric saccharides and have high diagnostic value. This approach, combined with liquid chromatography, can identify saccharide biomarkers in complex sample matrices.