Tascini Anna Sofia, Noro Massimo G, Chen Rongjun, Seddon John M, Bresme Fernando
Department of Chemistry, Imperial College London, UK.
Phys Chem Chem Phys. 2018 Jan 17;20(3):1848-1860. doi: 10.1039/c7cp06889a.
In recent years, sebum oil has been found to play a key role in the regulation of the hydration of the outermost layer of the skin, the stratum corneum. Understanding how a major component of the sebum oil, the triglyceride tri-cis-6-hexadecenoin (TG), interacts with water is an important step in gaining insight into the water regulation function of the sebum oil. Here we use molecular dynamics simulations to investigate the structural and interfacial properties of TG in bulk and at the air and water interface. Our model performs very well in reproducing experimental results, such as density, surface tensions and surface pressure area isotherms. We show that triglyceride molecules in the liquid phase assemble together, through the glycerol group, forming a single percolating network. TG-air interfaces orient the lipids with the interface enriched with the hydrophobic tails and the glycerol groups buried inside. When in contact with water, the TG molecules at the interface orient the glycerol group towards the water phase and adopt a characteristic trident conformation. Water is shown to penetrate the TG layer thanks to the interaction with the oxygen atoms of the TG molecules, which acts as a pathway for water diffusion. The activation energy for the passage of water is found to be ≈9.5kT at 310 K, showing that the layer is permeable to water diffusion.
近年来，人们发现皮脂在调节皮肤最外层即角质层的水合作用中起着关键作用。了解皮脂的主要成分甘油三酯三顺 - 6 - 十六碳烯酸酯（TG）如何与水相互作用，是深入了解皮脂水调节功能的重要一步。在此，我们使用分子动力学模拟来研究TG在本体以及空气 - 水界面处的结构和界面性质。我们的模型在重现实验结果方面表现出色，如密度、表面张力和表面压力 - 面积等温线。我们表明，液相中的甘油三酯分子通过甘油基团聚集在一起，形成单个渗透网络。TG - 空气界面使脂质定向排列，界面处富含疏水尾部，甘油基团埋在内部。当与水接触时，界面处的TG分子将甘油基团朝向水相，并呈现出特征性的三叉戟构象。由于与TG分子的氧原子相互作用，水被证明可以穿透TG层，这为水的扩散提供了一条途径。在310 K时，水通过的活化能约为9.5kT，表明该层对水的扩散是可渗透的。
