title: Structural characterization of oxidized glycerophosphatidylserine: evidence of polar head oxidation.
abstract: Non-oxidized phosphatidylserine (PS) is known to play a key role in apoptosis but there is considerable research evidence suggesting that oxidized PS also plays a role in this event, leading to the increasing interest in studying PS oxidative modifications. In this work, different PS (1-palmitoyl-2-linoleoyl-sn-glycero-3-phospho-L-serine (PLPS), 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine (POPS), and 1,2-dipalmitoyl-sn-glycero-3-phospho-L-serine (DPPS) were oxidized in vitro by hydroxyl radical, generated under Fenton reaction conditions, and the reactions were monitored by ESI-MS in negative mode. Oxidation products were then fractionated by thin layer chromatography (TLC) and characterized by tandem mass spectrometry (MS/MS). This approach allowed the identification of hydroxyl, peroxy, and keto derivatives due to oxidation of unsaturated fatty acyl chains. Oxidation products due to oxidation of serine polar head were also identified. These products, with lower molecular weight than the non-modified PS, were identified as [M - 29 - H](-) (terminal acetic acid), [M - 30 - H](-) (terminal acetamide), [M - 13 - H](-) (terminal hydroperoxyacetaldehyde), and [M - 13 - H](-) (terminal hydroxyacetaldehyde plus hydroxy fatty acyl chain). Phosphatidic acid was also formed in these conditions. These findings confirm the oxidation of the serine polar head induced by the hydroxyl radical. The identification of these modifications may be a valuable tool to evaluate phosphatidylserine alteration under physiopathologic conditions and also to help understand the biological role of phosphatidylserine oxidation in the apoptotic process and other biological functions.
authors.affiliation: Mass Spectrometry Centre, QOPNA, Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Elisabete
authors.initials: E
authors.lastname: Maciel
authors.forename: Raquel Nunes
authors.initials: RN
authors.lastname: da Silva
authors.forename: Cláudia
authors.initials: C
authors.lastname: Simões
authors.forename: Pedro
authors.initials: P
authors.lastname: Domingues
authors.forename: M Rosário M
authors.initials: MR
authors.lastname: Domingues
mesh_terms: D017665:Hydroxyl Radical / Q000737:chemistry; D010084:Oxidation-Reduction; D010718:Phosphatidylserines / Q000737:chemistry* / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry
chemical_list: D010718:Phosphatidylserines; C038694:dipalmitoylphosphatidylserine; D017665:Hydroxyl Radical; C050294:1-palmitoyl-2-oleoylglycero-3-phosphoserine