title: Photosensitized oxidation of phosphatidylethanolamines monitored by electrospray tandem mass spectrometry.
abstract: Photodynamic therapy combines visible light and a photosensitizer (PS) in the presence of molecular oxygen to generate reactive oxygen species able to modify biological structures such as phospholipids. Phosphatidylethanolamines (PEs), being major phospholipid constituents of mammalian cells and membranes of Gram-negative bacteria, are potential targets of photosensitization. In this work, the oxidative modifications induced by white light in combination with cationic porphyrins (Tri-Py(+)-Me-PF and Tetra-Py(+)-Me) were evaluated on PE standards. Electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (ESI-MS/MS) were used to identify and characterize the oxidative modifications induced in PEs (POPE: PE 16:0/18:1, PLPE: PE 16:0/18:2, PAPE: PE 16:0/20:4). Photo-oxidation products of POPE, PLPE and PAPE as hydroxy, hydroperoxy and keteno derivatives and products due to oxidation in ethanolamine polar head were identified. Hydroperoxy-PEs were found to be the major photo-oxidation products. Quantification of hydroperoxides (PE-OOH) allowed differentiating the potential effect in photodamage of the two porphyrins. The highest amounts of PE-OOH were notorious in the presence of Tri-Py(+)-Me-PF, a highly efficient PS against bacteria. The identification of these modifications in PEs is an important key point in the understanding cell damage processes underlying photodynamic therapy approaches.
authors: Mass Spectrometry Centre, UI QOPNA, Department of Chemistry, University of Aveiro, 3810-193, Aveiro, Portugal.
authors: Tânia
authors: T
authors: Melo
authors: Nuno
authors: N
authors: Santos
authors: Diana
authors: D
authors: Lopes
authors: Eliana
authors: E
authors: Alves
authors: Elisabete
authors: E
authors: Maciel
authors: Maria A F
authors: MA
authors: Faustino
authors: João P C
authors: JP
authors: Tomé
authors: Maria G P M S
authors: MG
authors: Neves
authors: Adelaide
authors: A
authors: Almeida
authors: Pedro
authors: P
authors: Domingues
authors: Marcela A
authors: MA
authors: Segundo
authors: M Rosário M
authors: MR
authors: Domingues
mesh_terms: D010084:Oxidation-Reduction; D010714:Phosphatidylethanolamines / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D010714:Phosphatidylethanolamines
keywords: electrospray; phosphatidylethanolamines; photo-oxidation; photodynamic therapy; photosensitizer; tandem mass spectrometry