The lipid and protein structure of mouse stratum corneum: a wide and small angle diffraction study

The structure of mouse stratum corneum was investigated using small and wide angle X-ray scattering. Diffraction patterns were collected as a function of temperature and hydration. The lipid lamellar structure is characterized by a repeat distance of 13.4 nm. Occasionally a second lipid lamellar phase has been found with a repeat distance of 6.1 nm. Upon hydration neither swelling of the lamellae nor lateral swelling of the lipids was found. On the basis of these facts it was concluded that the size of the crystallographic unit cell of the lipid structure is insensitive to the water content. The 13.4 nm lamellar phase disappeared upon heating to 55 degrees C. At 45 degrees C the orthorhombic lateral packing disappeared. At this temperature only an hexagonal and liquid lateral packing of the lipids was observed. The hexagonal lateral packing transformed to a liquid one between 45 degrees C and 80 degrees C. Model calculations were carried out to obtain the electron density profile of the lamellar structure. In all models three electron lucent regions were fitted between which electron dense regions are located indicating that the 13.4 nm lamellar structure consist of three bilayers.