MODULATION OF MEMBRANE-FUSION BY ASYMMETRIC TRANSBILAYER DISTRIBUTIONS OF AMINO LIPIDS
MODULATION OF MEMBRANE-FUSION BY ASYMMETRIC TRANSBILAYER DISTRIBUTIONS OF AMINO LIPIDS
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DOI：
10.1021/bi00208a007
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发表时间：
1994-10-25
期刊：
影响因子：
2.9
通讯作者：
CULLIS, PR
中科院分区：
文献类型：
--
作者：
BAILEY, AL;CULLIS, PR
融合的模型脂质双层含有合成的氨基脂质和这种融合的调节诱导transbilayer不对称性，这些氨基脂质通过施加pH梯度证明。在卵磷脂酰胆碱（EPC）、二油酰磷脂酰乙醇胺（DOPE）和胆固醇（比例为35：20：45）的混合物中，由5 mol % 1，2-二油酰-3-（N，N-二甲基氨基）丙烷（AL 1）组成的直径为100 nm的脂质体在pH 4.0时不融合。当这些囊泡的外部pH增加到7.5时也没有观察到融合，这导致所有的快速运输到内部单层，如通过对表面电荷敏感的荧光探针所测量的。然而，施加的pH梯度的耗散导致AL1在pH 7.5的外单层的重新分配，并导致脂质体融合，如通过荧光脂质混合试验和冷冻断裂电子显微镜检测。不同的碳氢化合物结构的AL 1的融合率的影响证明了与五个合成类似物，AL 2-AL 6。含有较长不饱和酰基链的脂质和膜结合氨基脂质的pK（a）值较低时，融合率较高。融合也与在pH 7.5的双层的不稳定，所示的六方H-II相的形成。
The fusion of model lipid bilayers containing synthetic amino lipids and the regulation of this fusion by inducing transbilayer asymmetry of these amino lipids via imposed pH gradients are demonstrated. Liposomes of 100 nm diameter consisting of 5 mol % 1,2-dioleoyl-3-(N,N-dimethylamino)propane (AL1) in a mixture of egg phosphatidylcholine (EPC), dioleoylphosphatidylethanolamine (DOPE), and cholesterol in a ratio of 35:20:45 do not fuse at pH 4.0. Fusion also is not observed upon increasing the external pH of these vesicles to 7.5, which results in the rapid transport of All to the inner monolayer, as measured by a fluorescent probe sensitive to surface charge. However, dissipation of the imposed pH gradient leads to redistribution of AL1 to the outer monolayer at pH 7.5 and causes liposomal fusion, as detected by fluorescent lipid-mixing assay and freeze-fracture electron microscopy. The effect of varying the hydrocarbon structure of AL1 on the rate of fusion is demonstrated with five synthetic analogues, AL2-AL6. Higher rates of fusion occur with lipids containing longer unsaturated acyl chains and with lower values of pK(a) for the membrane-bound amino lipids. Fusion is also associated with destabilization of the bilayer at pH 7.5, as indicated by the formation of the hexagonal H-II phase.