Identification of Mobility-Resolved N-Glycan Isomers

ABSTRACT: 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 IMSn with cryogenic vibrational spectroscopy to identify N-glycan reducing-end anomers. By identifying the reducing-end alpha and beta 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.

Automated summary

Glycan analysis has made significant progress in the past decade, with the development of high-resolution ion-mobility spectrometry allowing for the separation of structurally similar positional isomers. This study combines IMSn with cryogenic vibrational spectroscopy to identify the reducing-end anomers of N-glycans, and also establishes an infrared fingerprint database for unambiguous identification of these anomers from positional isomers in complex mixtures.