Das Chinmay, Noro Massimo G, Olmsted Peter D
School of Physics and Astronomy, University of Leeds, United Kingdom.
Biophys J. 2009 Oct 7;97(7):1941-51. doi: 10.1016/j.bpj.2009.06.054.
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 fluidlike environment at the bilayer midplane. 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 interleaflet region is lowered, and the bilayers 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.
我们展示了由神经酰胺NS - 24:0、游离脂肪酸24:0和胆固醇组成的完全水合双层膜的原子分子动力学结果，以研究角质层（皮肤最外层）脂质基质中不同成分对其结构性质的影响。与磷脂双层膜相比，含有神经酰胺分子的双层膜表现出更高的面内密度，因此被动运输速率更低。在生理温度下，对于所研究的所有组成比，脂质处于具有有序脂质尾部的凝胶相。然而，神经酰胺分子两条尾部长度的巨大不对称性导致双层膜中间平面处呈现类似流体的环境。对于纯神经酰胺或任何一种两组分混合物，横向压力分布在整个双层膜上显示出很大的局部变化。接近皮肤组成比时，横向压力波动被极大抑制，来自两个叶层的神经酰胺尾部显著相互交错，叶层间区域的局部密度降低，并且双层膜的弹性模量降低。这表明角质层脂质层中观察到的组成比既决定了良好的屏障性能，也决定了脂质结构对机械应力的稳定性。
