角质层脂质混合物的模拟研究
Simulation studies of stratum corneum lipid mixtures
摘要：
我们目前的原子分子动力学的结果完全水合的双层组成的神经酰胺NS-24：0，游离脂肪酸24：0和胆固醇，以解决角质层（皮肤的最外层）脂质基质的不同成分对其结构特性的影响。与磷脂双层相比，含有神经酰胺分子的双层显示出更高的面内密度，因此显示出更低的被动转运速率。在生理温度下，对于探索的所有组合物比率，脂质处于具有有序脂质尾部的凝胶相中。然而，神经酰胺分子的两个尾部的长度的大的不对称性导致在双层中平面处的流体状环境。侧向压力曲线显示纯神经酰胺或任何两种组分混合物在整个双层中存在较大的局部变化。接近皮肤组成比，侧向压力波动被极大地抑制，来自两个小叶的神经酰胺尾部显著地相互交叉，小叶间区域的局部密度的凹陷降低，并且双层具有降低的弹性模量。这表明角质层脂质层中观察到的组成比是脂质结构对机械应力的良好屏障性质和稳定性的原因。
英文摘要：
We present atomistic molecular dynamics results for fully hydrated bilayers composed of ceramide NS-24:0, free fatty acid 24:0 and cholesterol, to address the effect of the different components in the stratum corneum (the outermost layer of skin) lipid matrix on its structural properties. Bilayers containing ceramide molecules show higher in-plane density and hence lower rate of passive transport compared to phospholipid bilayers. At physiological temperatures, for all composition ratios explored, the lipids are in a gel phase with ordered lipid tails. However, the large asymmetry in the lengths of the two tails of the ceramide molecule leads to a fluid like environment at the bilayer mid-plane. The lateral pressure profiles show large local variations across the bilayer for pure ceramide or any of the two component mixtures. Close to the skin composition ratio, the lateral pressure fluctuations are greatly suppressed, the ceramide tails from the two leaflets interdigitate significantly, the depression in local density at the inter-leaflet region is lowered, and the bilayer have lowered elastic moduli. This indicates that the observed composition ratio in the stratum corneum lipid layer is responsible for both the good barrier properties and the stability of the lipid structure against mechanical stresses.
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