Characterization of simple isomeric oligosaccharides and the rapid separation of glycan mixtures by ion mobility mass spectrometry

Ion mobility techniques, using both traveling wave-based technology and standard drift tube methods, along with molecular modeling were used to examine the gas-phase conformational properties of a series of isomeric oligosaccharides and hydrazine-released N-linked glycans from various sources. Electrospray ionization was used to generate H⁺ and Na⁺ adducts of oligosaccharides as well as Na⁺ and H₂PO₄^- adducts of released N-linked glycans. The ion mobility mass spectrometry techniques were used to separate the isomeric oligosaccharides and the glycan mixtures. Good agreement was obtained between the theoretical and measured collision cross-sections. Glycans common to each glycoprotein were observed to have the same arrival time distribution independent of their source. In some cases support for multiple isomers was observed which correlated well with evidence obtained, where possible, from other experimental techniques. The sensitivity of the traveling wave ion mobility spectrometry (TWIMS) technique, together with the rapid experimental timescale, reproducibility and high information content make this an attractive approach for the characterization of complex mixtures of glycans released from glycoproteins. Successful calibration of the TWIMS arrival times/cross-sections was demonstrated using data from the drift tube instrument.