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.

Buzios, Rio de Janeiro, Brasil

Congreso; VII Congreso Iberolatinoamericano de Biofísica; 2009

Sociedad Brasilera de Biofisica, Sociedad Argentina de Biofisica, IUPAB

A study involving liposome structure and peroxidation was carried out with the main goal of experimentally find if there was a relation between membrane packing and lipid peroxidation in liposomes encapsulating  a-tocopherol. Model membranes were liposomes composed by 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and  a-tocopherol was included in the membrane in the ratios 1; 5; 10 and 20 (% mol/mol). Membrane anisotropy was determined by fluorescence of 1,6-diphenyl-1,3,5-hexatriene (DPH) and hydrophobicity index was followed by spectroscopy, using merocyanine 540 (MC540). Efficiency to avoid membrane oxidation was studied in mitochondria by TBA method. Results showed that  a-tocopherol decreased anisotropy in gel phase but only in concentrations lower than 10 % mol/mol, probably due to an existence of phase separation. Regarding to hydrophobicity index, a-tocopherol also decreased it but in all tested concentrations. Presence of liposomes and a -tocopherol decreased peroxidation in mitochondria in comparison with free a -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 lipid peroxidation than an heterogeneous one, with defects in their surface