Impact of Ionic Liquids in Aqueous Solution on Bacterial Plasma Membranes Studied with Molecular Dynamics Simulations
Impact of Ionic Liquids in Aqueous Solution on Bacterial Plasma Membranes Studied with Molecular Dynamics Simulations
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DOI：
10.1021/jp5060952
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发表时间：
2014-09-04
影响因子：
3.3
通讯作者：
Klaehn, Marco
中科院分区：
文献类型：
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作者：
Lim, Geraldine S.;Zidar, Jernej;Klaehn, Marco
使用分子动力学 (MD) 模拟研究了五种不同的咪唑基离子液体 (IL) 稀释在水中对细菌质膜特性的影响。考虑的阳离子有 1-辛基-3-甲基咪唑鎓 (OMIM)、1-辛氧基甲基-3-甲基咪唑鎓 (OXMIM) 和 1-十四烷基-3-甲基咪唑鎓 (TDMIM)，以及阴离子氯离子和乳酸根。膜双层的原子模型旨在重现革兰氏阴性大肠杆菌质膜的脂质组成。在所有 IL 中都观察到阳离子自发插入膜中。 OMIM 的插入明显多于 OXMIM，并且与乳酸相比，氯化物的存在减少了阳离子插入。相反，阴离子不会吸附到膜表面上，也不会扩散到双层中。插入后，阳离子与膜脂平行，阳离子烷基尾部嵌入疏水膜核心，而咪唑鎓环大部分仍暴露在溶剂中。这种插入的阳离子与膜中的一到两个磷脂密切相关。插入OMIM和OXMIM后，脂质的整体顺序下降，而相反，TDMIM附近的脂质顺序增加。 OMIM 和 OXMIM 的短烷基尾部在双层中产生空隙，这些空隙由卷曲脂质填充。这种阳离子诱导的脂质紊乱也会降低平均膜厚度。由于阳离子烷基链和脂质的脂肪酸长度相似，在 TDMIM 插入后没有观察到这种效应。插入的 TDMIM 的这种模拟脂质的行为表明该阳离子具有高膜亲和力，随着时间的推移，可能会导致膜中阳离子的积累增加。总的来说，模拟揭示了阳离子如何插入细菌膜以及这种插入如何改变其特性。此外，还强调了阳离子和阴离子的不同作用，并证明了阳离子烷基链长度及其官能化的根本重要性。
The impact of five different imidazolium-based ionic liquids (ILs) diluted in water on the properties of a bacterial plasma membrane is investigated using molecular dynamics (MD) simulations. Cations considered are 1-octyl-3-methylimidazolium (OMIM), 1-octyloxymethyl-3-methylimidazolium (OXMIM), and 1-tetradecyl-3-methylimidazolium (TDMIM), as well as the anions chloride and lactate. The atomistic model of the membrane bilayer is designed to reproduce the lipid composition of the plasma membrane of Gram-negative Escherichia coli. Spontaneous insertion of cations into the membrane is observed in all ILs. Substantially more insertions of OMIM than of OXMIM occur and the presence of chloride reduces cation insertions compared to lactate. In contrast, anions do not adsorb onto the membrane surface nor diffuse into the bilayer. Once inserted, cations are oriented in parallel to membrane lipids with cation alkyl tails embedded into the hydrophobic membrane core, while the imidazolium-ring remains mostly exposed to the solvent. Such inserted cations are strongly associated with one to two phospholipids in the membrane. The overall order of lipids decreased after OMIM and OXMIM insertions, while on the contrary the order of lipids in the vicinity of TDMIM increased. The short alkyl tails of OMIM and OXMIM generate voids in the bilayer that are filled by curling lipids. This cation induced lipid disorder also reduces the average membrane thickness. This effect is not observed after TDMIM insertions due to the similar length of cation alkyl chain and the fatty acids of the lipids. This lipid-mimicking behavior of inserted TDMIM indicates a high membrane affinity of this cation that could lead to an enhanced accumulation of cations in the membrane over time. Overall, the simulations reveal how cations are inserted into the bacterial membrane and how such insertions change its properties. Moreover, the different roles of cations and anions are highlighted and the fundamental importance of cation alkyl chain length and its functionalization is demonstrated.