Fluid-gel coexistence in lipid membranes under differential stress
Fluid-gel coexistence in lipid membranes under differential stress
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DOI：
10.1016/j.bpj.2022.07.021
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发表时间：
2022-08-16
影响因子：
3.4
通讯作者：
Deserno, Markus
中科院分区：
文献类型：
--
作者：
Foley, Samuel L.;Hossein, Amirali;Deserno, Markus
许多生物脂质双层的广泛保守性质是它们的不对称性。除了在其两侧具有不同的组成之外，膜还可以在其两个小叶中表现出不同的张力，这种状态被称为差应力。在这里，我们研究这种应力如何影响单组分膜的组成脂质单层的相行为。对于温度足够接近，但仍然高于，主要的转变，分子动力学模拟显示有限的凝胶域内压缩的小叶的出现。我们通过添加两个经验的流体-凝胶转变的单小叶自由能来描述这种现象的热力学，每个自由能在其各自的不对称依赖的脂质密度下进行评估。在模拟中产生的有限尺寸效应包括在理论中通过一个几何形状依赖的界面项。我们的模型再现了模拟中观察到的相共存。因此，它可以用来连接的“隐藏变量”的差异应力的实验观察到的主要相变的属性。这些想法可以推广到任何一级双层相变的存在下的不对称性，包括液体有序/液体无序相分离。
A widely conserved property of many biological lipid bilayers is their asymmetry. In addition to having distinct com-positions on its two sides, a membrane can also exhibit different tensions in its two leaflets, a state known as differential stress. Here, we examine how this stress can influence the phase behavior of the constituent lipid monolayers of a single-component membrane. For temperatures sufficiently close to, but still above, the main transition, molecular dynamics simulations show the emergence of finite gel domains within the compressed leaflet. We describe the thermodynamics of this phenomenon by adding two empirical single-leaflet free energies for the fluid-gel transition, each evaluated at its respective asymmetry-dependent lipid density. Finite size effects arising in simulation are included in the theory through a geometry-dependent interfacial term. Our model reproduces the phase coexistence observed in simulation. It could therefore be used to connect the "hidden variable"of differential stress to experimentally observable properties of the main phase transition. These ideas could be generalized to any first-order bilayer phase transition in the presence of asymmetry, including liquid-ordered/liquid-disordered phase separation.