FIGURE 8. Expanded negative ion electrospray ionization mass spectra of myocardial lipid extracts from iPLA₂γ KO mice and their wild type littermates.

Myocardial lipid extracts of wild type mice (A) and iPLA₂γ KO mice (B) were prepared by a modified Bligh and Dyer procedure. Negative ion electrospray ionization mass spectra were acquired using a QqQ mass spectrometer as described under “Experimental Procedures.” Spectra have been normalized to a CL internal standard (see insets). The asterisks indicate the doubly charged CL plus-one isotopologues whose ion peak intensities were utilized to quantify individual CL molecular species as described previously (26). The results indicate the paucity of tetra-18:2 CL molecular species in the iPLA₂γ KO in comparison with WT (compare peaks at m/z 723.5 in control versus iPLA₂γ KO). The insets on the right of each panel show the extended mass spectra that display additional internal standards and other major anionic phospholipids.