Insights into the molecular organization of lipids in the skin barrier from infrared spectroscopy studies of stratum corneum lipid models

In order to gain some insight into the molecular organization of lipids in the skin barrier we used Fourier transform infrared (FTIR) spectroscopy to investigate models of the stratum corneum (SC) containing deuterated hexade canoic acid, cholesterol, and ceramide 2 or ceramide 5. Tn both models ther e is clear evidence of separate conformationally ordered domains of ceramid e and fatty acids. In addition, these chains are packed in orthorhombic sub cells at physiological temperatures. The ceramide headgroup behavior indica tes distinct hydrogen bonding patterns between the ceramide 2 and ceramide 5 models. In the ceramide 2 model the amide I mode is split into two compon ents suggesting strong transverse intermolecular hydrogen bonding between h eadgroups. In contrast, no amide splitting is observed for ceramide 5 altho ugh the amide frequencies are indicative of strong hydrogen bonding. These observations on the molecular organization of SC Lipids are discussed in te rms of skin barrier function.