SOYBEAN PHOSPHATIDYLCHOLINE LIPOSOMES AS A TOOL TO STUDY PEROXIDATION PHOTOINDUCED BY PTERIN

MARIANA VIGNONI; ANGEL CATALA; ANDRÉS H. THOMAS

Maresias, São Paulo

Congreso; XII Encuentro Latinoamericano de Fotoquímica y Fotobiología (XII Elafot); 2015

ELAFOT

Lipid peroxidation is thought to be involved in many physiological and pathological events, and is usually due to oxidative stress. This procces can proceed by 3 different mechanisms: free radical-mediated oxidation, which occurs by chain reaction mechanism (initiation, propagation and termination), free radical-independent, nonenzymatic oxidation (that involves 1O2) and enzymatic oxidation [1,2]. The most important one is the free radical mechanism, where the initiation phase includes hydrogen atom abstraction, and the main compounds of lipid membranes, phospholipids containing polyunsaturated fatty acids, are predominantly susceptible to this.Pterins (Pt) are heterocyclic compounds that can be found in biological systems in multiple forms and playing different roles, such as pigments or enzymatic cofactors for numerous redox and one-carbon transfer reactions [3]. They act as photosensitizers under UVA radiation on biomolecules such as nucleotides, plasmid DNA, amino acids, proteins [4,5]. In addition, it has been found that pterins have phototoxic effect on cell culture [6].In order to get further insight into the photosensitizing effect of pterin on cell membranes, liposomes can be used as model systems in a first approach. Therefore, in this work, sonicated liposomes prepared with soybean phosphatidylcholine (SoyPC) were submitted to lipid peroxidation, under air atmosphere at room temperature, with pterin (Ptr) as a photosensitizer under UVA irradiation. Conjugated dienes and trienes, determined by absorption at 234 and 270 nm respectively, were measured as a function of irradiation time. Mass spectrometry measurements were performed to identify peroxidation products. In addition, location of pterin in the liposomes was investigated by size exclusion chromatography and absorption/fluorescence spectra.