Lipid structural information from a single equine embryo by MALDI-MS

The aim of this work was to report the potential of MALDI-MS for the characterization of lipid species present in a single equine embryo, and to study some lipid structures detected by collision induced dissociation (CID) experiments. In the positive ion mode spectrum, we could observe mostly protonated and sodiated species of sphingomyelins (SM), phosphatidylcholines (PC) and triacylglycerols (TAG). In the negative ion mode, we observed phosphatidylethanolamines (PE) and phosphatidylinositols (PI). MS/MS spectrum of most intense lipid ions was performed to show MALDI-MS/MS structural information potential. MS/MS spectrum in the positive mode of m/z 760.6 (attributed as PC34:1) depicted characteristic PC fragments of m/z 184.1 (choline polar head), and the neutral loss (NL) of 183 (phosphorylcholine). For the ion of m/z 766.6 (attributed as PE 38:5), we observed the NL of 140, characteristic of PE. For the ion of m/z 808.7 (attributed as PC 38.5), besides the fragment at m/z 184.1 at the NL of 183, it was possible to observe the loss of trimethylamine (ion of m/z 749.6), and the cyclophosphane (ion of m/z 147.0). Finally, for the negative ion mode, we isolated and fragmented the ion at m/z 863.6, which was attributed as PI 36:1 due to the presence of m/z 153 (glycerol phosphate – H2O-H), 223 (phospho inositol – 2H2O-H), 241 (phospho inositol – H2O-H), 281 (oleic acid), and 581.3 (lysophosphoinositol – H2O-H). We conclude that MALDI-MS allowed the detection of a broad range of PC, SM, PE, PI and TAG lipid species, as well as a fast and confident characterization of lipid structures from a single equine embryo.