engleski

Sulfur centered radicals in lipid modification processes

Hydrogen sulfide (H2S) had been conventionally considered as a toxic molecule but recent studies suggest that it plays an important function in cardiovascular and brain functions, acting as an intracellular messenger, a signaling molecule which can be a source of free radicals. Different H2S-derived radicals can be involved in inflammation during radical stress and in cell signaling. The reactions of thiyl radicals as isomerizing agents are not well known especially with the interplay of lipid peroxidation process. Oxidation of polyunsaturated fatty acids (PUFA) by thiyl radicals is believed to be responsible for some of the biological damage in cell membranes. At the same time, thiyl radicals can cause the isomerization of the PUFA double bonds with formation of trans-isomers, the irreparable and harmful process occuring in the lipid bilayers. The aim of this study is to investigate the role of H2S as a precursor of diffusible simple S- centered radicals on lipid peroxidation and geometrical isomerization processes in biomimetic lipid model system. In this study lipid peroxidation and geometrical trans-isomerization were determined under biomimetic conditions. Thiyl radicals were generated by γ-radiation of simple model micellar system containing linoleic acid and H2S or 2- mercaptoethanol (2-ME). Model lipid systems were irradiated up to the dose of 400 Gy, under different biomimetic free radical conditions at room temperature using panoramic 60Co source at the Ruđer Bošković Institute. The concentrations of hydroperoxides of linoleic acid were determined by the spectrophotometric ferric thiocyanate method and the geometrical isomerization of LH methyl ester was studied by capillary gas chromatography. In addition, we investigated the concentration effect of thiols on the outcome of the two lipid modification processes. We believe that this study could contribute to the understanding of chemical basis of H2S reactions which take place in biomembranes that could be essential for explaining the intriguing role of this the simplest thiol as a signaling molecule in biological systems.

gamma irradiation, sulfur radicals, lipid peroxidation, isomerization

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