engleski

LIPID MODIFICATION PROCESSES INDUCED BY THIYL RADICALS

Free radicals originating either naturally within the body or coming from the environment damage cell membranes primarily through two pathways involving thiol chemistry: lipid peroxidation, which is inhibited by thiols, and lipid isomerization, which is catalysed by S-centered radicals. It has been shown that one process can be parallel with the occurrence of the other and that lipid hydroperoxides and mono-trans fatty acids can be formed to a comparable extent under oxidative free radical conditions.1 In this study the formation of lipid hydroperoxides and trans-isomers were carried out under biomimetic conditions.1 Thiyl radicals were generated by γ-radiation of simple model micellar system containing linoleic acid2 and 2-mercaptoethanol under air and air free conditions. Besides low doses the effect of high irradiation doses on both lipid modification processes were studied. In air-equilibrated solutions of 10─5 M linoleic acid the propagation proceeded rapidly up to 400 Gy after which the termination prevailed thus interrupting lipid peroxidation up to 10 kGy. At the same time the concentration of the trans-isomers reached the maximum level already at about 1 kGy. In addition, we investigated the effect of the micelle size and kinetic stability of micelles on the outcome of the two lipid modification processes. This study revealed that lipid peroxidation and trans-isomerization processes depend on the supramolecular organization, in particular for the positional preference of the double bond isomerization in lipid model systems. References: [1] B. Mihaljević, I. Tartaro, C. Ferreri, C. Chatgilialoglu, Org. Biomol. Chem. 9 (2011) 3541–3548. [2] B. Mihaljević, I. Tartaro, N. Filipović Vinceković, Eur. J. Lipid Sci. Technol. 114 (2012) 1292–1303.

lipid hydroperoxides; cis; trans isomers; thiyl radicals

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