Lipid Isomer Analysis on the Development of SRM Based Method for Diacylphospholipids Profiling

Abstract

Lipids are the molecules in charge of physiological functions such as membrane structure, energy storage or bioactive lipids themselves. Molecular weight of lipid is at most 2000, which is not so larger than that of DNA or proteins. Over 40,000 lipid species are registered in LIPID MAPS (http://www.lipidmaps.org/). It means that dozens of isomeric and isobaric lipid species are condensed in 1 mass unit. Lipidomics is a technology to analyze comprehensive lipid molecules quantitatively using mass spectrometer. Accurate MS such as time of flight or orbital trap type MS coupled with database search is major platform in lipidomics. Recent study using accurate MS based comprehensive lipidomics shown that over 1000 lipids were identified in biological sample. Widely targeted lipidomics using selected reaction monitoring (SRM) with triple quadrupole MS (TQ-MS) is the other platform. Ultra-fast TQ-MS enables to set 500 SRM transition per second including polarity switching. Here we present that development of SRM based lipidomics methods for phospholipids using TQ-MS coupled with reversed phase chromatography. Over 200 phospholipids were identified using the SRM based method from the lipid extracts of mouse tissues. Also we would like to discuss how to identify lipid isomers and isobaric species in the SRM based lipidomics focused on diacylphospholipids analysis.