Membranes serve diverse functions in biological systems. Variations in their molecular compositions impact their physical properties and lead to rich phase behavior such as switching from the gel to fluid phase and/or separation to micro- and macrodomains with different molecular compositions. We present a combined computational and experimental study of the phase behavior of a mixed membrane of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) molecules. This heterogeneous membrane changes from gel to fluid and shows separate domains as a function of temperature. Atomically detailed simulations provide microscopic information about these molecular assemblies. However, these systems are challenging for computations since approaching equilibrium necessitates exceptionally long molecular dynamics trajectories. We use the simulation method of MDAS (Molecular Dynamics with Alchemical Steps) to generate adequate statistics. Isotope-edited IR spectroscopy of the lipids was used to benchmark the simulations. Together, simulations and experiments provide insight into the structural and dynamical features of the phase diagram.

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异质膜中的相变：原子详细图片。

膜在生物系统中具有多种功能。其分子组成的变化会影响其物理性质并导致丰富的相行为，例如从凝胶相转变为液相和/或分离为具有不同分子组成的微域和宏观域。我们对 1,2-二棕榈酰- sn -甘油-3-磷酸胆碱 (DPPC) 和 1,2-二月桂酰- sn -甘油-3-磷酸胆碱 (DLPC)混合膜的相行为进行了综合计算和实验研究分子。这种异质膜从凝胶变为流体，并随着温度的变化显示出不同的域。原子详细模拟提供了有关这些分子组装体的微观信息。然而，这些系统对计算具有挑战性，因为接近平衡需要非常长的分子动力学轨迹。我们使用 MDAS（分子动力学与炼金步骤）的模拟方法来生成足够的统计数据。使用同位素编辑的脂质红外光谱来对模拟进行基准测试。模拟和实验共同提供了对相图结构和动力学特征的深入了解。