Lipid thermotropic transitions in human stratum corneum.

The techniques of differential scanning calorimetry (DSC) and thermal perturbation infrared (IR) spectrometry were used to investigate thermal transitions in intact, fractionated, and lipid-extracted human stratum corneum. The DSC results show 3 major and one minor thermal transition in the range of 30-120 degrees C. Of particular interest to this study are 2 transitions seen near 65 degrees and 75 degrees C in intact stratum corneum and a stratum corneum membrane preparation, but absent from lipid-extracted samples. Results of IR spectrometry show that thermally induced spectral changes related to enhanced motion of the lipid acyl chains also occur in the region of about 60-80 degrees C. The combined DSC and IR results show that the thermal transitions near 65 degrees and 75 degrees C depend on water concentration in a manner identical to that seen for a variety of lipid-water systems. Taken together, these results suggest that thermal transitions occurring near 65 degrees and 85 degrees C involve increased acyl chain motion of stratum corneum lipids.