Acyl chain unsaturation and vesicle curvature alter outer leaflet packing and promote poly(ethylene glycol)-mediated membrane fusion.
Acyl chain unsaturation and vesicle curvature alter outer leaflet packing and promote poly(ethylene glycol)-mediated membrane fusion.
复制标题
DOI：
10.1021/bi962437i
复制
发表时间：
1997-05
期刊：
影响因子：
2.9
通讯作者：
W. Talbot;L. Zheng;B. Lentz
中科院分区：
文献类型：
--
作者：
W. Talbot;L. Zheng;B. Lentz
使用两种测定内部囊泡内容物混合和渗漏的方法，比较了聚乙二醇 (PEG) 诱导的超声单层囊泡 (SUV) 和由多种磷脂酰胆碱组成的大单层囊泡 (LUV) 的融合。在第一个[Lentz 等人。 (1992) Biochemistry, 31, 2643]，8-氨基萘-1,3,6-三磺酸二钠 (ANTS) 荧光被共封装的 N,N'-p-亚二甲苯基双(溴化吡啶) (DPX) 猝灭。对于该测定，PEG 中杂质荧光的干扰要求在进行测量之前通过稀释来降低样品的 PEG 含量。第二次测定[Viguera 等人。 (1993) Biochemistry, 32, 3708] 直接在浓 PEG 溶液中监测与吡啶二羧酸 (DPA) 复合的 Tb3+ 的荧光。对于用浓度增加的 PEG 处理的 Egg PC SUV，这两种测定给出了相同的融合曲线，表明融合在 PEG 存在的脱水状态下发生，并且不需要稀释。与SUV或LUV中掺入不同不饱和度的脂质种类获得的结果的比较表明，酰基链不饱和度和高膜曲率相结合有利于纯磷脂酰胆碱膜的融合。不同膜中膜探针 1-(4-三甲基铵)-6-苯基-1,3,5-己三烯 (TMA-DPH) 的荧光寿命或有序参数与诱导这些膜融合所需的 PEG 浓度之间存在明显的相关性。然而，对于不同的脂质种类，在 D2O 与 H2O 缓冲液中测量的 TMA-DPH 寿命比率是相同的，这表明探针渗透对于不同的脂质种类并没有太大差异。结果表明，高膜曲率和广泛的链不饱和度的综合作用是双层上部区域脂质运动速率的增强，反映了不饱和SUV双层外层堆积密度的降低，可能允许增强的水渗透性，从而增加融合的可能性。
The poly(ethylene glycol) (PEG)-induced fusion of sonicated, unilamellar vesicles (SUV) and large, unilamellar vesicles (LUV) composed of a variety of phosphatidylcholine species was compared using two assays for the mixing and leakage of internal vesicle contents. In the first [Lentz et al. (1992) Biochemistry, 31, 2643], disodium 8-aminonaphthalene-1,3,6-trisulfonate (ANTS) fluorescence is quenched by co-encapsulated N,N'-p-xylylenebis(pyridinium bromide) (DPX). For this assay, interference by the fluorescence of impurities in PEG demands that the PEG content of the sample be reduced by dilution before measurements are taken. The second assay [Viguera et al. (1993) Biochemistry, 32, 3708] monitors the fluorescence of Tb3+ complexed with dipicolinic acid (DPA) directly in concentrated PEG solutions. The two assays gave identical fusion profiles for egg PC SUVs treated with increasing concentrations of PEG, demonstrating that fusion occurs in the dehydrated state in the presence of PEG and does not require dilution. Comparison of results obtained with lipid species of varying degrees of unsaturation incorporated into either SUV or LUV suggested that acyl chain unsaturation and high membrane curvature combine to favor fusion of pure phosphatidylcholine membranes. There was a clear correlation between the fluorescence lifetime or the order parameter of the membrane probe 1-(4-trimethylammonium)-6-phenyl-1,3,5-hexatriene (TMA-DPH) in different membranes and the concentration of PEG needed to induce fusion of these membranes. However, the ratios of TMA-DPH lifetimes measured in D2O versus H2O buffers were the same for different lipid species, indicating that probe penetration was not very different for different lipid species. The results suggest that the combined effect of high membrane curvature and extensive chain unsaturation is an enhanced rate of lipid motion in the upper region of the bilayer, reflective of decreased packing density in the outer leaflet of unsaturated SUV bilayers, probably allowing for enhanced water penetration leading to an enhanced probability of fusion.