Molecular dynamics simulation of sodium dodecylsulfate (SDS) bilayers
Molecular dynamics simulation of sodium dodecylsulfate (SDS) bilayers
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十二烷基硫酸钠 (SDS) 双层的分子动力学模拟
DOI：
10.1016/j.jcis.2017.07.042
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发表时间：
2017
影响因子：
9.9
通讯作者：
Hou Wanguo
中科院分区：
文献类型：
--
作者：
Zhang Hongshu;Yuan Shiling;Sun Jichao;Liu Jianqiang;Li Haiping;Du Na;Hou Wanguo
十二烷基硫酸钠（SDS）是一种简单的单尾表面活性剂（STS），它的胶束溶液在固体表面的作用下不需要任何添加剂即可形成稳定的囊泡。为了在分子水平上进一步理解这种转变的机制，在双分子层的下层小叶已经从固体表面分离的情况下，进行了分子动力学模拟，系统地研究了体溶液中SDS双分子层的片段（作为囊泡的一部分）。当烷基链间初始交叉度（δi）大于8.0±1.4%时，SDS膜更倾向于保持其双层结构，而不是回到胶束结构。当达到平衡时，交叉度总是接近31.7±2.0%。随着下叶截面积的增加，聚集体表现为弯曲双层、平面双层、穿孔双层和胶束。此外，DS -和Na+离子或水分子之间形成盐桥和水桥结构，有利于SDS双分子层的稳定性。两小叶间盐桥沿S-O轴方向的分布差异导致了双层结构的不对称性，对双层结构曲率的形成起辅助作用。我们期望这项工作有助于在分子水平上理解界面现象和简单单尾表面活性剂囊泡自组装的机制。
Sodium dodecylsulfate (SDS) - a simple single tailed surfactant (STS) can form stable vesicles from its micellar solution without any additives under the mediation of solid surfaces. To further understand the mechanism of this transition on the molecular level, molecular dynamics simulations are performed to study segments of SDS bilayers (as part of vesicles) in the bulk solution systematically, at the moment that the lower leaflet of bilayers already detached from solid surfaces. The SDS membrane would rather keep their bilayers structure than return to micelles when the initial interdigitated degree (δi) between alkyl chains is more than 8.0 ± 1.4%. And the interdigitated degree is always approaching to 31.7 ± 2.0% while the equilibrium is reached. The aggregates behave as curved bilayers, planar bilayers, perforated bilayers, and micelles with the increase of the lower leaflet cross-sectional area. Besides, the structures of salt bridge and water bridge structures are formed between DS−and Na+ions or water molecules, which contribute to the stability of SDS bilayers. The distribution difference of the salt bridges along the direction of S-O axis between the two leaflets leads to the asymmetry of the bilayers, which plays supplementary role to the formation of bilayers curvature. We expect that this work help to shed light on the understanding of interface phenomena and the mechanism of simple single-tailed surfactant vesicle self-assembly on the molecular level.