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  • Title: Interaction between an organic hydroperoxide and an unsaturated phospholipid and alpha-tocopherol in model membranes.
    Author: Nakano M, Sugioka K, Nakamura T, Oki T.
    Journal: Biochim Biophys Acta; 1980 Aug 11; 619(2):274-86. PubMed ID: 7407212.
    Abstract:
    The behavior of an organic hydroperoxide in the presence of lipid and/or alpha-tocopherol in model membranes has been studied using 14C-labeled cholesterol-5 alpha-hydroperoxide as the organic hydroperoxide. Cholesterol-F alpha-hydroperoxide in saturated phospholipid micelles is rapidly isomerized to cholesterol-7 alpha-hydroperoxide. Such an isomerization is inhibited by alpha-tocopherol, but not by an alpha-tocopheryl analogue with a substituted OH groups, present in the micelles, indicating the formation of hydrogen bonds between OH group in alpha-tocopherol and OOH group in the 5 alpha-hydroperoxide. The double bonds in unsaturated phospholipid can also serve to form a hydrogen bond with OOH in the 5 alpha-hydroperoxide moiety in the micelles. The resulting hydrogen-bonded complex could be decomposed by iron-induced lipid peroxidation, accompanied by isomerization of the 5 alpha-hydroperoxide and the further degradation to the 7-ketocholesterol and 7 alpha-hydroxycholesterol. When three components, such as unsaturated phospholipid, 5 alpha-hydroperoxide and alpha-tocopherol, are present in the same micelles, they form hydrogen bonded complexes. Such complexes could be decomposed by iron in the ferrous state, yielding mainly 5 alpha-hydroxycholesterol without significant change in the structure of alpha-tocopherol and peroxidative cleavage of unsaturated phospholipid.
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