Systematic analysis of choline-containing phospholipids using multi-dimensional mass spectrometry-based shotgun lipidomics

Herein, a systematic study on the identification and quantitation of choline-containing phospholipid molecular species, including choline glycerophospholipid (PC), lysoPC, and sphingomyelin (SM), is described using multi-dimensional mass spectrometry-based shotgun lipidomics after intrasource separation (MDMS-SL). Current methods for analysis of choline-containing lipids were improved through multiple modifications leading to: (1) identification of constituents present in the PC and SM classes, subclasses of PC, and individual molecular species using MDMS-SL analysis in the positive-ion mode; (2) identification of the fatty acyl constituents and their regiospecificity in diacyl PC molecular species through the neutral loss of trimethylamine plus fatty acids; (3) direct identification of the alkenyl chains of plasmenylcholine species using precursor ion scans of the fragment ions carrying the alkenyl chains; (4) elimination of the effects of polyunsaturation on the quantitation of PC species by multiple ratiometric comparisons; (5) accurate identification and quantitation of lysoPC molecular species including regioisomers by diagnostic fragment ions; and (6) accurate identification and quantitation of SM molecular species by neutral loss scans of phosphocholine plus methyl aldehyde which is specific to SM molecular species. With these enhancements, the application of MDMS-SL for the analyses of choline-containing phospholipid molecular species in biomedical research has been extended to a much larger number of molecular species with greater quantitative accuracy and an increased depth of structural information.