Bouwstra J A, Gooris G S, van der Spek J A, Bras W
Center for Bio-Pharmaceutical Sciences, Leiden University, The Netherlands.
J Invest Dermatol. 1991 Dec;97(6):1005-12. doi: 10.1111/1523-1747.ep12492217.
The structure of human stratum corneum was investigated with small-angle X-ray scattering (SAXS). At room temperature the scattering curve was characterized by a strong intensity at low scattering vector (Q less than 0.8 nm-1) and two complicated diffraction peaks originating from a lamellar structure of the lipids. The lamellar lipid structure in the stratum corneum transformed to a disordered structure between 65 degrees C and 75 degrees C, the same temperature region at which a thermal lipid transition occurred. After cooling down to room temperature a recrystallization of at least a part of the lipids took place, after which only one unit cell with a repeat distance of 13.4 nm could be detected. Comparison of the scattering curve of the stratum corneum after crystallization with the scattering curve of the stratum corneum before recrystallization leads to the conclusion that in the original curve the lipids are arranged in two unit cells with repeat distances of 6.4 nm and 13.4 nm. From model calculations it appears that the latter unit cell consists of more than one bilayer. The scattering curves of stratum corneum hydrated to various levels were measured. A change in the water content of stratum corneum between 6% w/w and 60% w/w (fully hydrated) did not result in swelling of the bilayers, but the scattering curve obtained with stratum corneum hydrated to 60% w/w differed from those at lower hydration levels: the scattering curve at 60% w/w showed only the diffraction peaks corresponding to a unit cell with a repeat distance of 6.4 nm. This observation implies that the ordering of a part of the lipids is reduced at very high water contents, which may explain the strong penetration-enhancing effects of water in the stratum corneum.
采用小角X射线散射（SAXS）研究了人体角质层的结构。在室温下，散射曲线的特征是在低散射矢量（Q小于0.8 nm-1）处有很强的强度，以及源自脂质层状结构的两个复杂衍射峰。角质层中的层状脂质结构在65℃至75℃之间转变为无序结构，这与脂质发生热转变的温度区域相同。冷却至室温后，至少一部分脂质发生了重结晶，之后只能检测到一个重复距离为13.4 nm的晶胞。将结晶后角质层的散射曲线与重结晶前角质层的散射曲线进行比较，得出的结论是，在原始曲线中，脂质排列在两个重复距离分别为6.4 nm和13.4 nm的晶胞中。从模型计算来看，后一个晶胞由不止一个双层组成。测量了水合至不同程度的角质层的散射曲线。角质层含水量在6% w/w至60% w/w（完全水合）之间变化时，双层并未膨胀，但水合至60% w/w的角质层得到的散射曲线与较低水合水平时的不同：60% w/w时的散射曲线仅显示对应于重复距离为6.4 nm的晶胞的衍射峰。这一观察结果表明，在非常高的含水量下，一部分脂质的有序性降低，这可能解释了水对角质层的强烈促渗作用。
