STAGES OF THE BILAYER-MICELLE TRANSITION IN THE SYSTEM PHOSPHATIDYLCHOLINE-C(12)E(8) AS STUDIED BY DEUTERIUM-NMR AND PHOSPHORUS-NMR, LIGHT-SCATTERING, AND CALORIMETRY
STAGES OF THE BILAYER-MICELLE TRANSITION IN THE SYSTEM PHOSPHATIDYLCHOLINE-C(12)E(8) AS STUDIED BY DEUTERIUM-NMR AND PHOSPHORUS-NMR, LIGHT-SCATTERING, AND CALORIMETRY
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DOI：
10.1016/s0006-3495(95)80220-1
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发表时间：
1995-02-01
影响因子：
3.4
通讯作者：
BEYER, K
中科院分区：
文献类型：
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作者：
OTTEN, D;LOBBECKE, L;BEYER, K
本文用H-2-和P-31-NMR、静态和动态光散射以及差示扫描量热法研究了非离子型洗涤剂八甘醇单正十二烷基醚（C（12）E（8））对磷脂双层膜的扰动作用。在宽温度范围内研究了饱和磷脂1，2-二棕榈酰-SN-甘油-3-磷酸胆碱（DPPC）、1，2-二肉豆蔻酰-SN-甘油-3-磷酸胆碱（DMPC）和1，2-二月桂酰-SN-甘油-3-磷酸胆碱（DLPC）与洗涤剂的预平衡混合物，包括纯磷脂的主要热致相变温度。在此温度以上，在磷脂/洗涤剂摩尔比2：1下，膜在磁场中取向。低于纯磷脂的热致相变温度的混合物的冷却导致胶束形成。在DPPC和DMPC与C（12）E（8）的混合物中，在增溶起始温度下的窄量热信号表明胶束形成与磷脂酰基链的无序-有序转变有关。在双层-胶束转变的温度范围内，粒径从150 nm变化到接近7 nm。膜在高温下的自发取向使得能够从氘光谱直接测定链段序参数。磷脂酰基链的序参数分布可以归因于整个膜的缓慢波动和洗涤剂引起的双层秩序的局部扰动。在混合双层，最终导致双层增溶的包装约束反映了界面磷脂酰基链段和磷脂头基的顺序参数。这些结果被解释在变化的平均形状的组成分子。考虑到在酰基链区域中的横截面积减小和洗涤剂头基的水合作用增加，双层胶束转变是链和头基排斥不平衡的结果。根据界面四极分裂的温度依赖性，可以定义一个中性面或枢轴面。
The perturbation of phospholipid bilayer membranes by a nonionic detergent, octaethyleneglycol mono-n-dodecylether (C(12)E(8)), was investigated by H-2- and P-31-NMR, static and dynamic light scattering, and differential scanning calorimetry. Preequilibrated mixtures of the saturated phospholipids 1,2-dipalmitoyl-sn-glycero-3-phosphorylcholine (DPPC), 1,2-dimyristoyl-sn-glycero-3-phosphorylcholine (DMPC), and 1,2-dilauroyl-sn-glycero-3-phosphorylcholine (DLPC) with the detergent were studied over a broad temperature range including the temperature of the main thermotropic phase transition of the pure phospholipids. Above this temperature, at a phospholipid/detergent molar ratio 2:1, the membranes were oriented in the magnetic field. Cooling of the mixtures below the thermotropic phase transition temperatures of the pure phospholipids led to micelle formation. In mixtures of DPPC and DMPC with C(12)E(8), a narrow calorimetric signal at the onset temperature of the solubilization suggested that micelle formation was related to the disorder-order transition in the phospholipid acyl chains. The particle size changed from 150 nm to similar to 7 nm over the temperature range of the bilayer-micelle transition. The spontaneous orientation of the membranes at high temperatures enabled the direct determination of segmental order parameters from the deuterium spectra. The order parameter profiles of the phospholipid acyl chains could be attributed to slow fluctuations of the whole membrane and to detergent-induced local perturbations of the bilayer order. The packing constraints in the mixed bilayers that eventually lead to bilayer solubilization were reflected by the order parameters of the interfacial phospholipid acyl chain segments and of the phospholipid headgroup. These results are interpreted in terms of the changing average shape of the component molecules. Considering the decreasing cross sectional areas in the acyl chain region and the increasing hydration of the detergent headgroups, the bilayer-micelle transition is the result of an imbalance in the chain and headgroup repulsion. A neutral or pivotal plane can be defined on the basis of the temperature dependence of the interfacial quadrupolar splittings.