Yeagle P L, Hutton W C, Huang C H, Martin R B
Biochemistry. 1976 May 18;15(10):2121-4. doi: 10.1021/bi00655a014.
The structure of the head-group region of some phospholipid bilayers in vesicle form has been studied and an intermolecular association of the N-methyl protons of phosphatidylcholine (PC) with the phosphate of phosphatidylethanolamine (PE) in mixed vesicles has been identified. Observation of a 31P[1H] nuclear Overhauser effect (NOE) in the phosphorus nuclear magnetic resonances of both PC and PE in mixed vesicles demonstrates an intimate dipolar interaction between some protons and the phosphorus nuclei. Substitution of deuterium for the N-methyl protons of PC eliminated the majority of the effect and necessitated the construction of a model of the bilayer surface in which the N-methyl protons of PC could interact closely with the phosphates of neighboring PE molecules. The predominant orientation of the head group must then be parallel to the bilayer surface. The amino protons of PE do not contribute significantly to the observed NOE. A corollary of these results is that there is little if any tendency for either PC or PE in the mixed vesicles to segregate into separate domains. A decrease in NOE in sphingomyelin vesicles on going from H2O to D2O suggests that an exchangeable proton contributes to the NOE. In addition the low value of the NOE observed in D2O suggests that the head-group conformation of sphingomyelin differs from that of PC.
已经研究了一些呈囊泡形式的磷脂双层头部基团区域的结构，并确定了混合囊泡中磷脂酰胆碱（PC）的N-甲基质子与磷脂酰乙醇胺（PE）的磷酸基团之间存在分子间缔合。在混合囊泡中PC和PE的磷核磁共振中观察到31P[1H]核Overhauser效应（NOE），这表明一些质子与磷核之间存在紧密的偶极相互作用。用氘取代PC的N-甲基质子消除了大部分效应，因此需要构建一个双层表面模型，其中PC的N-甲基质子可以与相邻PE分子的磷酸基团紧密相互作用。那么头部基团的主要取向必须与双层表面平行。PE的氨基质子对观察到的NOE贡献不大。这些结果的一个推论是，混合囊泡中的PC或PE几乎没有或根本没有分离成单独区域的趋势。从H2O到D2O，鞘磷脂囊泡中NOE的降低表明一个可交换质子对NOE有贡献。此外，在D2O中观察到的NOE值较低，这表明鞘磷脂的头部基团构象与PC不同。
