Identification of sialic acid linkage isomers in glycans using coupled InfraRed Multiple Photon Dissociation (IRMPD) spectroscopy and mass spectrometry

International audience; The gas phase IR spectra of α2,3 and α2,6 linkage isomers of sialic acid-containing human milk oligosaccharides and N-glycans epitopes are measured in the 3 µm spectral range using IRMPD spectroscopy in protonated and Na+ charge states. Each linkage isomer has a unique IRMPD fingerprint, providing a convenient diagnostic of the sialic acid position. Finally, a generic trend is observed: 3-linked sialic acid results in a significant broadening of the spectroscopic signature regardless of the glycan core and the charge state which suggests a drastic influence of the sialic acid position on the glycan conformation.