CORRELATION BETWEEN MEMBRANE RIGIDITY AND PEROXIDATION EFFICIENCY IN DPPC LIPOSOMES ENCAPSULATING A-TOCOPHEROL

NADIA S. CHIARAMONI; VALERIA RISSO; MARINA MARSANASCO; MARÍA C. TAIRA; SILVIA DEL V. ALONSO

Buzios, Brasil

Congreso; VII Iberoamerican Congress of Biophysics 2009; 2009

CORRELATION BETWEEN MEMBRANE RIGIDITY AND PEROXIDATION EFFICIENCY IN DPPC LIPOSOMES ENCAPSULATING a-TOCOPHEROL.   Chiaramoni, N.S. *, Risso, V.A.+, Marsanasco, M. *, Taira, M.C. *, Alonso, S. del V*. *Laboratorio de Biomembranas (LBM), Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, R. Saenz Peña 352, (B1876BXD), Bernal, Argentina. + Laboratorio de Plegado de Proteínas (LPP), Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, R. Saenz Peña 352, (B1876BXD), Bernal, Argentina.       Vitamin E is a generic term including many tocol and tocotrienol compounds, which most active form is α-tocopherol. It is a major lipid-soluble antioxidant responsible for protecting membranes against lipid peroxidation which could slow the aging process in human or animals. A study involving liposome structure and peroxidation was carried out with the main goal of establish a possible relation between membrane packing and lipid peroxidation of liposomes encapsulating α-tocopherol. Liposomes composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and α-tocopherol with the different mol/mol percentages: 1; 5; 10 and 20.   Methods: Membrane structure was studied by two spectroscopic methods: fluorescence, followed by 1,6-diphenyl-1,3,5-hexatriene (DPH) anisotropy and absorbance measuring merocyanine 540 (MC540) probe hydrophobicity index. The protection efficiency of membrane oxidation was studied in mithochondrias by TBA method.   Results and Discussion: show that α-tocopherol decreases anisotropy in gel phase but only in concentrations lower than 10 % mol/mol, probably due to possible phase separation. Regarding to the hydrophobicity index, α-tocopherol also decreases with all concentrations tested.   Conclusion: Presence of liposomes and α-tocopherol decreases peroxidation in mitochondrias in comparison with free α-tocopherol, but the decrement in the case of 10 and 20 % mol/mol was lower than in the case of 1 and 5 %, showing that a homogeneous packed phase is more efficient in avoiding peroxidation than a heterogeneous one, with defects in their surface.