Utilizing Sub-ambient Pressure Ionization with Nanoelectrospray (SPIN) to Enable High Sensitivity Detection and Extended Structural Coverage of N-glycans in Human Serum

spectrometry has been employed to study several disease conditions and demonstrated promise in clinical biomarker discovery. However, investigations into the extent of glycosylation of human serum proteins is currently limited by the quality of instrumental analysis. Larger glycans, such as heavily sialylated and polysialylated glycans are typically not detected by LC-MS because they are extremely labile and also exhibit low ionization efficiency. By combining subambient pressure ionization with nanoelectrospray (SPIN) coupled to high resolution MS and advanced data processing tools, we demonstrate much extended glycan and sialic acid polymer coverage as compared to a conventional ESI-MS interface. The benefits of improved instrument sensitivity and gentler ionization conditions in the SPIN-MS interface facilitate the detection of sialic acid containing N-glycans without the need of sample derivatization. In addition, we show that SPIN-MS is effective in elucidating structures of heavily sialylated and polysialylated glycans previously unattainable by ESI.