Phosphatidylcholine vesicle-mediated decomposition of hydrogen peroxide.
Phosphatidylcholine vesicle-mediated decomposition of hydrogen peroxide.
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DOI：
10.1021/la701277f
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发表时间：
2007-07
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影响因子：
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通讯作者：
M. Yoshimoto;Yuya Miyazaki;Ayumi Umemoto;P. Walde;R. Kuboi;K. Nakao
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作者：
M. Yoshimoto;Yuya Miyazaki;Ayumi Umemoto;P. Walde;R. Kuboi;K. Nakao
过氧化氢（H2 O2）的分解在水溶液（50 mM Tris-HCl缓冲液，pH 7.4，含有100 mM NaCl）中，在25 ℃纯缓冲液中或在由各种磷脂酰胆碱（PC）形成的囊泡或胶束的存在下进行了检查。在不存在PC的情况下，超过90%的初始添加的H2 O2（1.0 mM）在孵育120 h后保持完整。通过使用不同的PC，在两个酰基链n中的碳原子数以及在不饱和度方面的变化的PC上的过氧化氢的分解的效果进行了研究。短链PC（n = 4，6-8）以非缔合单体或胶束的形式溶解于缓冲溶液中，在固定PC浓度为10 mM时，短链PC的存在略微提高了H2 O2的分解速率。由非脂质洗涤剂（胆酸钠、Triton X-100和十二烷基硫酸钠）形成的胶束具有类似的效果。与此形成鲜明对比的是，以囊泡（脂质体）形式分散在缓冲溶液中的具有长烃链（n ≥ 10）的PC显著提高了H2 O2的分解速率，其中最有效的PC是25 ℃时的1，2-二肉豆蔻酰-sn-甘油基-3-磷酸胆碱（DMPC）。这表明PC分子的堆积密度影响反应性，推测是通过PC组装体与H2 O2分子的直接相互作用。此外，在由具有不饱和酰基链的PC（1-棕榈酰基-2-油酰基-sn-甘油基-3-磷酸胆碱，POPC; 1，2-二油酰基-sn-甘油基-3-磷酸胆碱，DOPC）形成的囊泡的情况下，在所使用的条件下不会广泛地发生碳-碳双键氧化。这表明所观察到的PC对H2 O2分解的影响确实与组装结构（囊泡vs胶束vs单体）有关，并且显然与不饱和烃链的存在无关。嵌入囊泡酰基链区域的两种荧光探针的荧光偏振测量（DPH，1，6-diphenyl-1，3，5-hexatriene）或囊泡表面（TMA-DPH，1-（4-trimethylammoniumphenyl）-6-phenyl-1，3，5-碘化己三烯）表明，H2 O2的存在导致脂质流动性的降低。水表面，而不是囊泡双层的疏水区域的流动性的变化。这表明H2 O2的分解是通过H2 O2和PC囊泡的极性头基区域之间的相互作用触发的。
The decomposition of hydrogen peroxide (H2O2) was examined in aqueous solution (50 mM Tris-HCl buffer, pH 7.4, containing 100 mM NaCl) at 25 degrees C in pure buffer or in the presence of either vesicles or micelles formed from various phosphatidylcholines (PCs). In the absence of PCs, more than 90% of the initially added H2O2 (1.0 mM) remained intact after incubation for 120 h. The effect of the PCs on the decomposition of H2O2 was studied by using different PCs that varied in terms of number of carbon atoms in the two acyl chains n as well as in terms of the degree of unsaturation. PCs with short hydrocarbon chains (n = 4, 6-8) were dissolved in the buffer solution in the form of nonassociated monomers or as micelles in equilibrium with monomers at a fixed PC concentration of 10 mM. The presence of these short-chain PCs slightly enhanced the H2O2 decomposition rate. Micelles formed by non-lipid detergents (sodium cholate, Triton X-100, and sodium dodecylsulfate) had a similar effect. In marked contrast, PCs with long hydrocarbon chains (n > or = 10) dispersed in buffer solution as vesicles (liposomes) significantly enhanced the rate of H2O2 decomposition, with the most effective PC being 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) at 25 degrees C. This indicates that the packing density of the PC molecules influences the reactivity, presumably through the direct interaction of the PC assemblies with H2O2 molecules. Furthermore, in the case of vesicles formed from PCs with unsaturated acyl chains (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, POPC; 1,2-dioleoyl-sn-glycero-3-phosphocholine, DOPC), carbon-carbon double bond oxidation did not occur extensively under the conditions used. This indicates that the observed effect of PCs on the decomposition of H2O2 is indeed related to the assembly structure (vesicle vs micelles vs monomers) and is clearly not related to the presence of unsaturated hydrocarbon chains. Fluorescence polarization measurements of two fluorescent probes embedded either in the acyl chain region of the vesicles (DPH, 1,6-diphenyl-1,3,5-hexatriene) or on the surface of the vesicles (TMA-DPH, 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene iodide) show that the presence of H2O2 leads to a decrease in the fluidity of the lipid-water surface and not to a change in the fluidity of the hydrophobic region of the vesicle bilayer. This indicates that the decomposition of H2O2 is triggered through interactions between H2O2 and the polar head group area of PC vesicles.