Modeling Lipid-Lipid Correlations across a Bilayer Membrane Using the Quasi-chemical Approximation
Modeling Lipid-Lipid Correlations across a Bilayer Membrane Using the Quasi-chemical Approximation
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DOI：
10.1021/acs.langmuir.5b01719
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发表时间：
2015-09-15
期刊：
影响因子：
3.9
通讯作者：
May, Sylvio
中科院分区：
文献类型：
--
作者：
Bossa, Guilherme Volpe;Roth, Joseph;May, Sylvio
混合流体样脂类膜不仅表现出特定小叶内的脂类之间的相互作用，而且还表现出跨双层的相互作用。随后的整个膜结构域的集体小叶间耦合先前已经使用各种平均场方法进行了建模。然而，也在单个脂类的水平上，通过实验观察到带电/未带电的脂类的二元混合物与不匹配的短和长酰基链长的组合在双分子层上的相关性。本研究提出了一个格子气体模型来量化这些关联。为此，我们用两个耦合的二维晶格气体来表示宏观上均一的脂质双层，我们用准化学近似来研究这种气体。我们证明，只有当我们的模型除了考虑双层内和跨双层的两体脂相互作用外，还考虑了额外的多体相互作用机制，即由短链和长链脂类配对造成的局部疏水高度失配，才有可能对先前的实验结果进行合理化。通过与蒙特卡罗模拟的比较，验证了准化学近似的稳健性。
Mixed fluid-like lipid membranes exhibit interactions not only among the lipids within a given leaflet but also across the bilayer. The ensuing collective interleaflet coupling of entire membrane domains has been modeled previously using various mean-field approaches. Yet, also on the level of individual lipids have correlations across the bilayer been observed experimentally for binary mixtures of charged/uncharged lipids with mismatching combinations of short and long acyl chain lengths. The present study proposes a lattice gas model to quantify these correlations. To this end, we represent a macroscopically homogeneous lipid bilayer by two coupled two-dimensional lattice gases that we study using the quasi-chemical approximation. We demonstrate that the rationalization of previous experimental results is only possible if besides two-body lipid lipid interactions within and across the bilayer our model also accounts for an additional multibody interaction mechanism, namely the local hydrophobic height mismatch created by pairing short and long chain lipids together. The robustness of the quasi-chemical approximation is verified by comparison with Monte Carlo simulations.