Zwitterionic lipid assemblies: molecular dynamics studies of monolayers, bilayers, and vesicles using a new coarse grain force field.
Zwitterionic lipid assemblies: molecular dynamics studies of monolayers, bilayers, and vesicles using a new coarse grain force field.
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DOI：
10.1021/jp9107206
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发表时间：
2010-05-27
期刊：
影响因子：
--
通讯作者：
Klein ML
中科院分区：
文献类型：
--
作者：
Shinoda W;DeVane R;Klein ML
针对一系列两性离子脂类，提出了一种新的粗粒(CG)分子间力场。该模型是我们以前在非离子表面活性剂方面工作的扩展，旨在从全原子分子动力学(MD)模拟中再现实验表面/界面性质以及分布函数。利用简单的泛函形式，同时对多个脂质分子的力场参数进行了优化。由此得到的CG类双层膜具有合理的分子面积、链序参数和弹性性质。计算的DPPC单层表面压力-面积(π-A)曲线表明，与以前的CG模型相比，有了显著的改进。DPPC单层比聚乙二醇脂单层具有更长的持续长度，在负张力下表现出长寿命的弯曲单层表面。从过饱和的DPPC单层中喷出的芽具有大的双胞状结构，这与由过饱和的聚乙二醇脂类单层形成的胶束芽不同。在CG-MD模拟过程中，我们从DMPC分子的聚集体开始，成功地观察到了囊泡的形成。根据聚集的大小，脂集合自发地转变为闭合的小泡或双小泡。介于这两个极端之间的各种中间结构似乎都不稳定。通过施加外部粘附力来观察两个囊泡融合的尝试没有成功。目前的CG力场也支持稳定的多层DMPC囊泡。
A new coarse-grained (CG) intermolecular force field is presented for a series of zwitterionic lipids. The model is an extension of our previous work on nonionic surfactants and is designed to reproduce experimental surface/interfacial properties as well as distribution functions from all-atom molecular dynamics (MD) simulations. Using simple functional forms, the force field parameters are optimized for multiple lipid molecules, simultaneously. The resulting CG lipid bilayers have reasonable molecular areas, chain order parameters, and elastic properties. The computed surface pressure vs. area (π-A) curve for a DPPC monolayer demonstrates a significant improvement over the previous CG models. The DPPC monolayer has a longer persistence length than a PEG lipid monolayer, exhibiting a long-lived curved monolayer surface under negative tension. The bud ejected from an oversaturated DPPC monolayer has a large bicelle-like structure, which is different from the micellar bud formed from an oversaturated PEG lipid monolayer. We have successfully observed vesicle formation during CG-MD simulations, starting from an aggregate of DMPC molecules. Depending on the aggregate size, the lipid assembly spontaneously transforms into a closed vesicle or a bicelle. None of the various intermediate structures between these extremes seem to be stable. An attempt to observe fusion of two vesicles through the application of an external adhesion force was not successful. The present CG force field also supports stable multi-lamellar DMPC vesicles.
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