title: Determination of the fatty acyl profiles of phosphatidylethanolamines by tandem mass spectrometry of sodium adducts.
abstract: Phosphatidylethanolamines (PEs) are one of the major constituents of cellular membranes, and, along with other phospholipid classes, have an essential role in the physiology of cells. Profiling of phospholipids in biological samples is currently done using mass spectrometry (MS). In this work we describe the MS fragmentation of sodium adducts of 2-oleoyl-1-palmitoyl-sn-glycero-3-phosphatidylethanolamine (POPE) and 2-linoleoyl-1-palmitoyl-sn-glycero-3-phosphatidylethanolamine (PLPE). This study was performed by electrospray ionization tandem mass spectrometry (ESI-MS/MS) using three different instruments and also by matrix-assisted laser desorption/ionization tandem mass spectrometry (MALDI-MS/MS). All MS/MS spectra show product ions related to the polar head fragmentation and product ions related to the loss of acyl chains. In ESI-MS/MS spectra, the product ions [M+Na-R1COOH-43]+ and [M+Na-R2COOH-43]+ show different relative abundance, as well as [M+Na-R1COOH]+ and [M+Na-R2COOH]+ product ions, allowing identification of both fatty acyl residues of PEs, and their specific location. MALDI-MS/MS shows the same product ions reported before and other ions generated by charge-remote fragmentation of the C3-C4 bond (gamma-cleavage) of fatty acyl residues combined with loss of 163 Da. These fragment ions, [M+Na-(R2-C2H3)-163]+ and [M+Na-(R1-C2H3)-163]+, show different relative abundances, and the product ion formed by the gamma-cleavage of sn-2 is the most abundant. Overall, differences noted that are important for identification and location of fatty acyl residues in the glycerol backbone are: relative abundance between the product ions [M+Na-R1COOH-43]+ > [M+Na-R2COOH-43]+ in ESI-MS/MS spectra; and relative abundance between the product ions [M+Na-(R2-C2H3)-163]+ > [M+Na-(R1-C2H3)-163]+ in MALDI-MS/MS spectra.
authors.affiliation: Mass Spectrometry Centre, Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Cláudia
authors.initials: C
authors.lastname: Simões
authors.forename: Vanda
authors.initials: V
authors.lastname: Simões
authors.forename: Ana
authors.initials: A
authors.lastname: Reis
authors.forename: Pedro
authors.initials: P
authors.lastname: Domingues
authors.forename: M Rosário M
authors.initials: MR
authors.lastname: Domingues
mesh_terms: D005227:Fatty Acids / Q000032:analysis*; D010714:Phosphatidylethanolamines / Q000032:analysis* / Q000737:chemistry; D012964:Sodium / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D053719:Tandem Mass Spectrometry
chemical_list: D005227:Fatty Acids; D010714:Phosphatidylethanolamines; C057561:1-palmitoyl-2-oleoylphosphatidylethanolamine; C052154:1-palmitoyl-2-linoleoyl-3-phosphatidylethanolamine; D012964:Sodium