Structural Characterization of GSLs and Phospholipids by nanoESI-MS

The structures of GSLs and phospholipids were analyzed by means of nano electrospray ionization mass spectrometry (nanoESI MS) using a SYNAPT G2-S mass spectrometer (Waters, Manchester, UK) endowed with a Z-spray as previously described [13 (link),14 (link),17 (link),71 (link)]. In short, GSL were structurally characterized in positive ion mode with the following source settings: temperature 80 °C, capillary voltage 0.8 kV, sampling cone voltage 20 V, and offset voltage 50 V. Verification of MS¹ postulated GSL and phospholipid structures were verified by low-energy collision-induced dissociation (CID) MS² experiments. For this purpose, analyte precursor ions were selected in the quadrupole analyzer and separated by ion mobility under the following conditions: wave velocity 700–800 m/s, wave height 40 V, nitrogen gas flow rate 90 mL/min, and helium gas flow rate 180 mL/min. Ion fragmentation was achieved in the transfer cell using collision energies of 70 to 100 eV (E_lab). The nomenclature established by Domon and Costello served for denomination of MS²-derived GSL fragment ions [98 (link),99 (link)].