Oxonium Ion-Guided Ion Mobility-Assisted Glycoproteomics on the timsTOF Pro

Spatial separation of ions in the gas-phase, providing information about their size as collisional cross-sections, can readily be achieved through ion mobility. The timsTOF Pro combines a trapped ion mobility device with a quadrupole, collision cell and a time-of-flight analyser to enable the analysis of ions at great speed. Here, we show that the timsTOF Pro is capable of physically separating N-glycopeptides from non-modified peptides and producing high-quality fragmentation spectra, both beneficial for glycoproteomics analyses of complex samples. The glycan moieties enlarge the size of glycopeptides compared to non-modified peptides, yielding a clear cluster in the mobilogram that, next to increased dynamic range from the physical separation of glycopeptides and non-modified peptides, can be used to make an effective selection filter for directing the mass spectrometer to analytes of interest. This new approach was applied to selected glycoproteins, human plasma- and neutrophil-derived glycopeptides. We show that the achieved physical separation, combined with the focussing of the mass spectrometer, allows for improved extraction of information from the samples, even at shorter LC gradients of 15 min. We validated our approach on human neutrophil and plasma samples of known make-up, in which we captured the anticipated glycan heterogeneity (paucimannose, phosphomannose, high mannose, hybrid and complex glycans) from diverse biological samples (plasma and neutrophils) at the expected abundances. As the method is compatible with off-the-shelve data acquisition routines and data analysis software, it can readily be applied by any laboratory with a timsTOF Pro and is reproducible as demonstrated by an inter-laboratory comparison between two laboratories.