Bilayer polarity and its thermal dependency in the eo and ed phases of binary phosphatidylcholine/cholesterol mixtures
Bilayer polarity and its thermal dependency in the eo and ed phases of binary phosphatidylcholine/cholesterol mixtures
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DOI：
10.1016/j.bbamem.2007.08.012
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发表时间：
2007-11-01
影响因子：
3.4
通讯作者：
Martins, Jorge
中科院分区：
文献类型：
--
作者：
Arrais, Dalila;Martins, Jorge
在二元磷脂酰胆碱/胆固醇混合物中观察到膜性质的不同变化。这些混合物是非理想的，根据化学成分和其他热力学参数，表现为单相或单相共存。与纯磷脂双分子层相比，磷脂双分子层的透水性、厚度和热力学性能、磷脂酰基链的分子堆积和构象自由度、内偶极势和脂质横向扩散都发生了变化。基于DMPC/胆固醇和DPPC/胆固醇的相图，我们使用Py经验极性尺度比较了纯双分子层与这些混合物的特定组成的等效极性。除了纯脂质双层和混合脂质双层的对比外，我们还发现液体有序相和液体无序相（e(d)）表现出明显不同的极性。此外，在e(o)相中，双分子层的极性及其热依赖性随化学成分的不同而变化，在35、40和45 mol%时胆固醇的比例有显著差异。在20℃时，DMPC/胆固醇浓度为35 mol%和45 mol%时，等效介电常数分别为21.8和23.8。此外，我们说明极性在各种基于膜的过程和反应中的潜在影响，提出对于含胆固醇的双层，它也可能伴随着生物膜中侧异质性的发生。(c) 2007 Elsevier B.V.版权所有
Diverse variations in membrane properties are observed in binary phosphatidylcholine/cholesterol mixtures. These mixtures are nonideal, displaying single or phase coexistence, depending on chemical composition and other thermodynamic parameters. When compared with pure phospholipid bilayers, there are changes in water permeability, bilayer thickness and thermomechanical properties, molecular packing and conformational freedom of phospholipid acyl chains, in internal dipolar potential and in lipid lateral diffusion. Based on the phase diagrams for DMPC/cholesterol and DPPC/cholesterol, we compare the equivalent polarity of pure bilayers with specific compositions of these mixtures, by using the Py empirical scale of polarity. Besides the contrast between pure and mixed lipid bilayers, we find that liquid-ordered and liquid-disordered (e(d)) phases display significantly different polarities. Moreover, in the e(o) phase, the polarities of bilayers and their thermal dependences vary with the chemical composition, showing noteworthy differences for cholesterol proportions at 35, 40, and 45 mol%. At 20 degrees C, for DMPC/ cholesterol at 35 and 45 mol%, the equivalent dielectric constants are 21.8 and 23.8, respectively. Additionally, we illustrate potential implications of polarity in various membrane-based processes and reactions, proposing that for cholesterol containing bilayers, it may also go along with the occurrence of lateral heterogeneity in biological membranes. (c) 2007 Elsevier B.V. All rights reserved.