Cluster model of lipid phase transitions with application to passive permeation of molecules and structure relaxations in lipid bilayers
Cluster model of lipid phase transitions with application to passive permeation of molecules and structure relaxations in lipid bilayers
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脂质相变的簇模型及其在分子被动渗透和脂质双层结构松弛中的应用
DOI：
10.1021/ja00470a011
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发表时间：
1978
影响因子：
15
通讯作者：
T. Tsong
中科院分区：
文献类型：
--
作者：
M. Kanehisa;T. Tsong
本文从二维伊辛模型出发，用Fisher集团模型描述了脂双层中凝胶到液晶的相变。团簇被定义为非主导相的脂质分子通过最近邻连接在一起的微区。这一概念的灵感来自于许多实验观察，这些实验观察表明相边界在脂质相变或二元脂质混合物的相分离过程中的功能重要性。从量热数据的分析磷脂双层，它的结论是，脂质膜不表现出很强的合作过渡从完整的凝胶phaseto完整的液晶相。相反，脂质体系中含有大量的非优势相的团簇，这可能具有重要的生物学意义。这方面的双层行为很好地反映在两种实验数据：分子通过脂质膜的被动渗透和松弛到一个新的平衡状态后，温度跳跃的脂质体悬浮液。通过回顾脂双层渗透性的相变依赖性实验结果，将渗透基本分为三种类型，分别对应于水分子的渗透、非疏水性分子的渗透和疏水性分子的渗透。据报道，某些分子的渗透在凝胶向液晶相转变的中点处明显增强，这归因于两相之间的“结构无序”边界区域。得到的弛豫时间在相变温度处有一个极大值，这也可以用一个简单的团簇反应模型来解释.
A phenomenological description of the gel to liquid-crystalline phase transition in lipid bilayers is presented in terms of Fisher’s cluster model starting from the two-dimensional Ising model. A cluster is defined as a microdomain of lipid molecules in the nondominant phase linked together bynearest neighbors. The concept was inspired by many experimental observations suggesting the functional importance of the phase boundary during the lipid phase transition or phase separations of bina-ry lipid mixtures. From the analysis of calorimetric data for phospholipid bilayers, it is concluded that the lipid membrane does not exhibit a strong cooperative transition from the complete gel phaseto the complete liquid-crystalline phase. Instead, the lipid system contains a considerable amount of clusters of the nondominant phase, which may be of great biological impor-tance. This aspect of bilayer behavior is well reflected on two kinds of experimental data: the passive permeation of molecules through the lipid membraneand the relaxation to a new equilibrium state after the temperature jump of liposome suspensions. By reviewing the experimental results on the phase transition dependence of the permeability of lipid bilayers, the permeation is classified basically into three types, corresponding to the permeation of water molecules, nonhydrophobic molecules, and hydrophobic molecules. The permeation of certain molecules, which has been reported to be enhancedappreciably at the mid-point of the gel to liquid-crystalline phase transition, is attributed to the “structurally disordered” boundary regions between two phases. The relaxation times obtained for the phase transition of lipid bilayers show a maximum at the transition tempera-ture, which is also explained by a simple cluster reaction scheme.