Kinetics and dynamics of singlet oxygen scavenging by alpha-tocopherol in phospholipid model membranes
Kinetics and dynamics of singlet oxygen scavenging by alpha-tocopherol in phospholipid model membranes
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DOI：
10.1016/s0891-5849(96)00485-6
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发表时间：
1997-01-01
影响因子：
7.4
通讯作者：
Terao, J
中科院分区：
文献类型：
--
作者：
Fukuzawa, K;Matsuura, K;Terao, J
在脂质体中研究了α-生育酚（alpha-Toc）对单线态氧（O-1（2））的清除作用。O-1（2）是在水溶性亚甲基蓝（MB）和脂溶性12-（1-芘）十二烷酸（PDA）两种光敏剂存在下，通过光照射产生的。α-Toc的氧化速率取决于光敏染料和膜电荷：在MB系统中，α-Toc在含二鲸蜡基磷酸盐（DCP）的带负电荷的二肉豆蔻酰磷脂酰胆碱（DMPC）脂质体中氧化较快，在含硬脂胺（SA）的带中性电荷的DMPC脂质体和带正电荷的DMPC脂质体中氧化较慢，但在PDA系统中，氧化速率与膜电荷无关。MB系统中的电荷依赖性差异可能是由于O-1（2）生成的位点取决于MB的电荷依赖性分布，因为带正电荷的MB通过与膜表面的DCP相互作用增加了DCP-DMPC脂质体的zeta电位，但由于其位于本体水相中，因此对DMPC和SA-DMPC脂质体的zeta电位的改变较小。α-Toc在脂质体中的氧化速率与在乙醇溶液中的氧化速率不同：在MB体系中，在乙醇溶液中的氧化速率比在DMPC或SA-DMPC脂质体中的氧化速率快，而与在DCP-DMPC脂质体中的氧化速率相同。然而，在PDA系统中，在EtOH溶液中的氧化速率比在带或不带电荷的DMPC脂质体中慢。膜流动性改变了脂质体中α-Toc氧化的速率，该速率在液晶相中高于凝胶相中，这是通过在30 ℃下DMPC脂质体中的速率高于二棕榈酰磷脂酰胆碱（DPPC）脂质体来判断的。使用捕获O-1（2）的1，3-二苯基异苯并呋喃（DPBF）标记的DCP-DMPC脂质体，在膜中测定了α-Toc清除O-1（2）的速率常数、化学反应和物理猝灭。这些常数在两种光敏化系统中不同，在MB-系统中高于PDA-系统，并且低于EtOH溶液中的那些。版权所有（C）1997 Elsevier Science Inc.
Scavenging of singlet oxygen (O-1(2)) by alpha-tocopherol (alpha-Toc) was investigated in liposomes. O-1(2) was generated by photoirradiation in the presence of two photosensitizers, water-soluble methylene blue (MB) and lipid-soluble 12-(1-pyrene)dodecanoic acid (PDA). The rates of oxidation of alpha-Toc differed depending on the photosensitizing dye and the membrane charge: in the MB system, alpha-Toc was oxidized fast in negatively charged dimyristoylphosphatidylcholine (DMPC) liposomes containing dicetylphosphate (DCP) and slowly in neutrally charged DMPC liposomes and positively charged DMPC liposomes containing stearylamine (SA), but in the PDA-system, the oxidation rate was independent of the membrane charge. The charge-dependent difference in the MB-system would be due to the site of O-1(2) generation depending on the charge-dependent distribution of MB, because positively charged MB increased the zeta-potential of DCP-DMPC liposomes by its interaction with DCP at the membrane surface, but changed the zeta-potentials of DMPC and SA-DMPC liposomes less because of its location in the bulk water phase. The oxidation rate of alpha-Toc in liposomes was different from that in EtOH solution: in the MB system, the oxidation rate was faster in EtOH solution than in DMPC or SA-DMPC liposomes but the same as that in DCP-DMPC liposomes. However, in the PDA system, the oxidation rate was slower in EtOH solution than in DMPC liposomes with or without a charge. Membrane fluidity changed the rate of alpha-Toc oxidation in liposomes, the rate being higher in the liquid crystalline phase than the gel phase, as judged by the higher rate in DMPC liposomes than in dipalmitoylphosphatidylcholine (DPPC) liposomes at 30 degrees C. The rate constants of alpha-Toc for scavenging, the chemical reaction and physical quenching of O-1(2) were determined in membranes using DCP-DMPC liposomes labeled with 1,3-diphenyl-isobenzofuran (DPBF), which traps O-1(2). These constants differed in the two photosensitizing systems, being higher in the MB-system than in the PDA-system and were lower than those in EtOH solution. Copyright (C) 1997 Elsevier Science Inc.