Physical properties and surface interactions of bilayer membranes containing N-methylated phosphatidylethanolamines.
Physical properties and surface interactions of bilayer membranes containing N-methylated phosphatidylethanolamines.
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含有 N-甲基化磷脂酰乙醇胺的双层膜的物理性质和表面相互作用。
DOI：
10.1021/bi00337a022
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发表时间：
1985
期刊：
影响因子：
2.9
通讯作者：
Silvius,JR
中科院分区：
文献类型：
--
作者：
Gagné,J;Stamatatos,L;Diacovo,T;Hui,SW;Yeagle,PL;Silvius,JR
采用扫描量热法、31P核磁共振和冷冻断裂电镜研究了1,2 -二酰基-5n-甘油-3-磷酸乙醇胺及其n-甲基化类似物的水分散体的结构和物理性质。二酰基磷脂酰乙醇胺的连续n -甲基化只会导致其凝胶到液晶相变温度的轻微降低，而引入一个7v -甲基则会急剧提高脂质形成六方II相的温度。然而，31P核磁共振和电子显微镜显示，与纯PE不同，n -甲基化PE在远低于形成明确的六方II相的温度下可以形成各种不规则的非片层结构。当PE被n -甲基化衍生物取代时，钙诱导的由二酰或二酰磷脂酰丝氨酸和相应的PE组成的大单层囊泡中包裹的羧基荧光素的泄漏率大大降低。随着PE组分被其单、二、三n甲基化（磷脂酰胆碱）衍生物所取代，钙诱导的PE/磷脂酰丝氨酸（PS）囊泡脂质混合速率稳步降低。通过将量热法获得的相图与囊泡脂质混合的测量结果相关联，我们得出结论，像PE一样，二酰酰基- tv -甲基磷脂酰乙醇胺可以支持PS/ n -甲基-PE囊泡表面之间的直接相互作用，而不需要PS （Ca2+）富相的横向分离，而二酰酰基- ayv -二甲基-PE（和磷脂酰胆碱）不能。然而，当检测二油基脂质时，单甲基和二甲基PE都可以支持含有少量PS的囊泡膜之间的脂质混合。PE支持PS/Ca2+在囊泡表面之间引发的相互作用的能力总是优于其n -甲基化衍生物，这一事实似乎反映了未取代PE比其相对较小的头基团具有更高的氢键提供能力。1,2 -二酰基-$ n-甘油-3-磷酸胆碱（PC） 1和1,2 -二酰基-。-甘油-3-磷酸乙醇胺（PE）是哺乳动物细胞膜上两种主要的两性离子甘油脂，它们的物理性质和对体内膜功能的贡献有很大的不同(Crocken & Nyc，
The structure and physical properties of aqueous dispersions of 1, 2-diacyl-5n-glycero-3-phosphoethanolamines (PE’s) and theirN-methylated analogues have been studied by scanning calorimetry, 31P nuclear magnetic resonance, and freeze-fracture electron microscopy. While successive N-methylations of a diacylphosphatidylethanolamine cause only modestdecreases in its gel to liquid-crystalline phase transition temperature, the introduction of even a single 7V-methyl group sharply increases the temperature at which the lipid forms a hexagonal II phase. However, 31P nuclear magnetic resonance and electron microscopy show that unlike pure PE species, N-methylated PE’s can form a variety of irregular nonlamellar structures at temperatures well below that at which a well-defined hexagonal II phase is formed. The rate of calcium-induced leakage of encapsulated carboxyfluorescein from large unilamellar vesicles composed of dioleoyl-or dielaidoylphosphatidylserine and the corresponding PE is strongly reduced when PE is replaced by N-methylated derivatives. The rate of calcium-induced intermixing of lipids of PE/phosphatidylserine (PS) vesicles steadily decreases as the PE component is successively replaced by its mono-, di-, and tri-N-methylated (phosphatidylcholine) derivatives. By correlating calorimetrically obtained phase diagrams with measurements of vesicle lipid intermixing, we conclude that dielaidoyl-TV-methylphosphatidylethanolamine, like PE, can support direct interactions between the surfaces of PS/N-methyl-PE vesicles without lateral separation of a PS (Ca2+)-rich phase, while dielaidoyl-AyV-dimethyl-PE (and phosphatidylcholine) cannot. When dioleoyl lipids are examined, however, both the monomethyl-and dimethyl-PE species can support lipid intermixing between the membranes of vesicles containing even low amounts of PS. The ability of PE to support PS/Ca2+-initiated interactions between vesicle surfaces is invariably superiorto that of its N-methylated derivatives, a fact that appears to reflect the higher hydrogen bond donating abilityof unsubstituted PE more than the relatively small size of its head group. l, 2-Diacyl-$ n-glycero-3-phosphocholine (PC) 1 and 1, 2-diacyl-.?/!-glycero-3-phosphoethanolamine (PE), the two major zwitterionic glycerolipids of mammalian cellular membranes, differ markedlyin their physical properties and in their con-tributions to membranefunction in vivo (Crocken & Nyc,