Department of Chemical Engineering, National Cheng Kung University, Tainan 701, Taiwan.
Langmuir. 2012 May 29;28(21):8156-64. doi: 10.1021/la300651u. Epub 2012 May 15.
The physical stability of catanionic vesicles is important for the development of novel drug or DNA carriers. For investigating the mechanism by which catanionic vesicles are stabilized, molecular dynamics (MD) simulation is an attractive approach that provides microscopic structural information on the vesicular bilayer. In this study, MD simulation was applied to investigate the bilayer properties of catanionic vesicles composed of an ion pair amphiphile (IPA), hexadecyltrimethylammonium-dodecylsulfate (HTMA-DS), and a double-tailed cationic surfactant, ditetradecyldimethylammonium chloride (DTDAC). Structural information regarding membrane elasticity and the organization and conformation of surfactant molecules was obtained based on the resulting trajectory. Simulation results showed that a proper amount of DTDAC could be used to complement the asymmetric structure between HTMA and DS, resulting in an ordered hydrocarbon chain packing within the rigid membrane observed in the mixed HTMA-DS/DTDAC system. The coexistence of gel and fluid phases was also observed in the presence of excess DTDAC. MD simulation results agreed well with results obtained from experimental studies examining mixed HTMA-DS/DTDAB vesicles.
混合离子型囊泡的物理稳定性对于新型药物或 DNA 载体的开发非常重要。为了研究稳定混合离子型囊泡的机制，分子动力学（MD）模拟是一种很有吸引力的方法，它可以提供囊泡双层的微观结构信息。在这项研究中，应用 MD 模拟研究了由离子对两亲物（IPA）十六烷基三甲基溴化铵-十二烷基硫酸钠（HTMA-DS）和双尾阳离子表面活性剂十四烷基二甲基氯化铵（DTDAC）组成的混合离子型囊泡的双层性质。基于所得轨迹获得了关于膜弹性以及表面活性剂分子的组织和构象的结构信息。模拟结果表明，适量的 DTDAC 可用于补充 HTMA 和 DS 之间的不对称结构，从而在混合 HTMA-DS/DTDAC 体系中观察到刚性膜内有序的烃链堆积。在存在过量 DTDAC 的情况下，还观察到凝胶相和流动相共存。MD 模拟结果与研究混合 HTMA-DS/DTDAB 囊泡的实验结果吻合良好。
