Oligosaccharides are of great importance for a variety of biological functions such cell-cell-recognition, immune response or protein folding. However, compared to proteins or DNA, oligosaccharides are not assembled in a linear, template-derived fashion. Instead they are synthesized by a complex biological machinery, which leads to branched structures with a diverse regio- and stereochemistry. The analysis of the resulting isomers is usually very challenging and typically involves a combination of sophisticated chromatography, mass spectrometry and ion mobility mass spectrometry steps.<br/>Here we show that cold-ion gas phase infrared spectroscopy is a very promising alternative for the in-depth structural analysis of complex oligosaccharides. Spectra of a series of synthetically derived standards and biological glycans were recorded. For each of these oligosaccharides, unique and highly diagnostic absorption patterns with a variety of well-resolved bands was obtained. This unprecedented resolution reveals remarkable differences in the overall IR signatures and allows a simple, fingerprint-based discrimination between isomers, even if they merely differ in the stereochemistry of a single OH group. For larger glycans, the variety of fragments obtained by sequential MS also enables a fragment-based fingerprinting. These spectra can be stored in databases to provide reference data for quality control or serve as increments for the identification of unknown samples. As such, cold ion spectroscopy has the potential to serve as the ultimate analytical tool to fully disentangle the detailed structure of oligosaccharides.

Glycan fingerprinting using cold-ion infrared spectroscopy

256th National Meeting (2018)

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