Fig. 2.

Overview of the quantitative shotgun lipidomics approach. Yeast cell lysates were spiked with internal lipid standards. Samples were processed by 2-step lipid extraction for fractionation of apolar and polar lipids. The lipid extracts were analyzed by automated shotgun lipidomics analysis in negative and positive ion mode. Lipid species were detected by MPIS or MRM analysis on a QSTAR instrument, or by FT MS analysis on a LTQ Orbitrap machine. Quantification of ergosterol was achieved by chemical acetylation followed by MRM analysis. Identification and quantification of detected lipid species were performed by Lipid Profiler and ALEX.