Identification and Quantitation of Unsaturated Fatty Acid Isomers by Electrospray Ionization Tandem Mass Spectrometry: A Shotgun Lipidomics Approach

Abstract

Identification and quantification of unsaturated fatty acid (FA) isomers in a biological system are significant in the study of lipid metabolism and catabolism, membrane biophysics, and pathogenesis of diseases, but are challenging in lipidomics. We developed a novel approach for identification and quantitation of unsaturated FA isomers by exploiting two facts: (1) unsaturated FA anions yield fragment ion(s) from loss of CO2 or H2O from the anions upon collision-induced dissociation; and (2) the fragment ions yielded from discrete FA isomers have distinct profiles of the fragment ion intensity vs. collision conditions. These distinct profiles likely result from the differential interactions of the negative charge of the fragment ion with the electron clouds of the double bonds due to their different distances in discrete FA isomers. The novel approach was also extended to analyze the double bond isomers of FA chains present in phospholipids by multi-stage tandem mass spectrometry. Collectively, we developed a new approach for identification and quantification of the double bond isomers of endogenous FA species or FA chains present in intact phospholipid species. We believe that this approach should further advance the lipidomic power for identification of the biochemical mechanisms underlying metabolic diseases.

Comparative Phospholipid Profiles of Control and Glaucomatous Human Trabecular Meshwork

“…The advent of mass spectrometry, and the recent developments of bioinformatic approaches and databases have eliminated these critical barriers. [8][9][10][11] We present the results of profiling for four phospholipids classes, namely phosphatidylcholines (PCs), phosphatidylserines (PSs), phosphatidylethanolamines (PEs), and phosphatidylinositols (PIs), in the TM, and their comparative analyses between glaucomatous and control donors.…”

Phospholipid makeup of the breast adipose tissue is impacted by obesity and mammary cancer in the mouse: Results of a pilot study

“…An aliquot of 100 uL for each sample was suspended in 200 uL mixture of Acetonitrile: Isopropanol (1:1) solution (Sigma Aldrich) and directly infused into the mass spectrometer. Lipid class settings were determined from previously published papers [18–20,22–25] and analysis was performed for each of the phospholipids. A nanospray was used (Advion, Ithaca, NY) for infusion.…”

“…New profiling methods employing shotgun lipidomics, a technique used in mass spectrometry via direct loading of crude lipid extracts into the mass spectrometer for intra-source separation and identification of numerous lipids, allows for extensive cellular lipid profiles of different tissues being accrued with relative ease [16–20]. Using the new technology of shotgun lipidomics allowed us to analyze bAT including the differences in profiles of phospholipids between lean control mice (non-tumor bearing), lean mammary tumor-bearing, obese control mice, and obese mammary tumor-bearing mice.…”

The Electrophile Responsive Proteome: Integrating Proteomics and Lipidomics with Cellular Function

“…It has been established that the oxylipidome generated by controlled enzymatic pathways (e.g., LOX and COX) and nonspecific lipid peroxidation are distinct in two important areas: (i) The isomers, for example, F 2 -isoprostanes, generated from nonspecific lipid peroxidation, show little stereospecificity. In contrast, the enzymatic mechanism of lipid peroxidation generates specific and limited numbers of stereoisomers, for example, PGF 2a and, hence, different oxylipidomes (26,32,98). (ii) The nonspecific oxylipidome is populated by RLS not formed by enzymatic mechanisms.…”