Identification of Mobility-Resolved N -Glycan Isomers.

Glycan analysis has evolved considerably during the last decade. The advent of high-resolution ion-mobility spectrometry has enabled the separation of isomers with only the slightest of structural differences. However, the ability to separate such species raises the problem of identifying all the mobility-resolved peaks that are observed, especially when analytical standards are not available. In this work, we report an approach based on the combination of IMS n with cryogenic vibrational spectroscopy to identify N -glycan reducing-end anomers. By identifying the reducing-end α and β anomers of diacetyl-chitobiose, which is a disaccharide that forms part of the common core of all N -glycans, we are able to assign mobility peaks to reducing anomers of a selection of N -glycans of different sizes, starting from trisaccharides such as Man-1 up to glycans containing nine monosaccharide units, such as G2. By building an infrared fingerprint database of the identified N -glycans, our approach allows unambiguous identification of mobility peaks corresponding to reducing-end anomers and distinguishes them from positional isomers that might be present in a complex mixture.