Lipid biophysics of water loss through the skin.

The regulation of water loss through the skin is a poorly understood but crucial process in maintaining terrestrial life-forms. In mammalian skin, the outermost layer, called the stratum corneum (SC), is rate-limiting to water loss. We have evaluated temperature-dependent changes in water vapor permeability and infrared spectra of porcine SC. In particular, we have analyzed the infrared absorption peaks due to the extracellular lipids of the SC. These results show a remarkable correlation between water permeability and the frequency of the C-H stretching vibrations over a broad range of temperature. Since the spectral changes reflect an increased number of alkyl gauche conformers, these results suggest that water permeability is dependent upon the hydrocarbon-chain disorder of SC lipids.