Pechtold L A, Abraham W, Potts R O
Cygnus Inc., Redwood City, California, USA.
J Investig Dermatol Symp Proc. 1998 Aug;3(2):105-9. doi: 10.1038/jidsymp.1998.22.
Using fluorescence techniques, we studied the dynamics of the lipid bilayer matrix of human stratum corneum (SC) and compared the results with that of distearoyl-phosphatidylcholine (DSPC). We employed a series of 9-anthroyloxy fatty acids (AF) that partitioned into the bilayer, enabling us to evaluate this structure as a function of depth within the lamellae. With AF probes, the re-orientation of the fluorophore is known to be affected by the polarity, hydrogen bonding, and rigidity of the surrounding medium, altering the emission maximum and lifetime in the excited state. In addition, we evaluated quenching, in which iodide collides with the fluorophore, revealing information on the accessibility of the fluorophore located in the bilayer. The emission and lifetime data showed that the reorientation of the fluorophore in SC was more hindered than in DSPC, indicating that SC bilayers were more rigid than DSPC bilayers. Quenching data of both SC and DSPC indicated that the deeper the fluorophore was positioned in the bilayer, the less accessible it was to iodide, pointing to a gradient in accessibility. In addition, the quenching results also showed that the SC is less accessible to iodide than in DSPC. The observed differences in bilayer rigidity and quencher accessibility between the two systems can be explained by differences in lipid composition and hydration. Whereas the DSPC bilayer consists of phospholipids, SC bilayers are composed of more anhydrous lipids like cholesterol and ceramides, which form a tight bilayer packing. In this way SC lipids exist in a relatively anhydrous and rigid environment, forming an effective diffusion barrier to water and ions.
我们使用荧光技术研究了人类角质层（SC）脂质双层基质的动力学，并将结果与二硬脂酰磷脂酰胆碱（DSPC）的结果进行了比较。我们采用了一系列可分配到双层中的9-蒽氧基脂肪酸（AF），使我们能够评估该结构作为薄片内深度的函数。对于AF探针，已知荧光团的重新取向会受到周围介质的极性、氢键和刚性的影响，从而改变激发态下的发射最大值和寿命。此外，我们评估了猝灭，其中碘化物与荧光团碰撞，揭示了位于双层中的荧光团可及性的信息。发射和寿命数据表明，SC中荧光团的重新取向比DSPC中更受阻碍，这表明SC双层比DSPC双层更刚性。SC和DSPC的猝灭数据均表明，荧光团在双层中的位置越深，其对碘化物的可及性就越低，这表明存在可及性梯度。此外，猝灭结果还表明，SC比DSPC对碘化物的可及性更低。两个系统在双层刚性和猝灭剂可及性方面观察到的差异可以通过脂质组成和水合作用的差异来解释。DSPC双层由磷脂组成，而SC双层由更多无水脂质如胆固醇和神经酰胺组成，它们形成紧密的双层堆积。通过这种方式，SC脂质存在于相对无水和刚性的环境中，形成对水和离子的有效扩散屏障。
