Sennato S, Bordi F, Cametti C, Coluzza C, Desideri A, Rufini S
Dipartimento di Fisica, Universita' di Roma La Sapienza, Piazzale A. Moro 5, I-00185 Rome, Italy.
J Phys Chem B. 2005 Aug 25;109(33):15950-7. doi: 10.1021/jp051893q.
The interaction of the three main components of the mitochondrial membrane, namely cardiolipin, phosphatidylcholine, and phosphatidylethanolamine, has been studied investigating mixed cardiolipin-phosphatidylcholine and cardiolipin-phosphatidylethanolamine monolayers at different cardiolipin molar fractions. The thermodynamic behavior of the mixed monolayers was investigated by means of surface pressure and surface potential measurements, and atomic force microscopy was employed to characterize the morphology of the monolayers. Langmuir isotherms and surface potential curves show a regular behavior with a progressive transition toward the isotherm of the pure component. Positive deviations from ideality in the excess Gibbs energies of mixing suggest the presence of repulsive interactions in both systems. Analysis of partial molecular dipole moment indicates a discontinuity at a definite cardiolipin/phosphatidylethanolamine molar fraction, suggesting the formation of a stoichiometric complex; as a consequence, in mixed cardiolipin-phosphatidylethanolamine monolayers, a phase separation is observed at phosphatidylethanolamine excess. AFM measurements indicate the presence of two domains: one made by phosphatidylethanolamine and the other by a regular arrangement of phosphatidylethanolamine and cardiolipin at a fixed molecular ratio.
已通过研究不同心磷脂摩尔分数下的心磷脂 - 磷脂酰胆碱和心磷脂 - 磷脂酰乙醇胺混合单层，对线粒体膜的三个主要成分，即心磷脂、磷脂酰胆碱和磷脂酰乙醇胺之间的相互作用进行了研究。通过表面压力和表面电位测量研究了混合单层的热力学行为，并采用原子力显微镜对单层的形态进行了表征。朗缪尔等温线和表面电位曲线呈现出规则的行为，逐渐向纯组分的等温线转变。混合超额吉布斯自由能的正偏差表明两个体系中均存在排斥相互作用。部分分子偶极矩分析表明，在一定的心磷脂/磷脂酰乙醇胺摩尔分数处存在不连续性，这表明形成了化学计量复合物；因此，在心磷脂 - 磷脂酰乙醇胺混合单层中，在磷脂酰乙醇胺过量时观察到相分离。原子力显微镜测量表明存在两个区域：一个由磷脂酰乙醇胺构成，另一个由按固定分子比规则排列的磷脂酰乙醇胺和心磷脂构成。
