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

Abstract 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.