STUDY OF LIPID AND NONLIPID STRUCTURE IN HUMAN STRATUM-CORNEUM BY X-RAY-DIFFRACTION

The molecular organization of human stratum corneum (SC) is still poorly known, in spite of its importance for the understanding of its biological functions. By using synchrotron X-ray diffraction and oriented samples, new basic features were revealed in the 2.5-to- 125 angstrom domain. The X-ray patterns were richer and more complex than previously published. Lipid extraction allows discrimination between the proteic or lipidic origin of the numerous ares and rings observed. Concerning the proteins, we found that the keratin organization (alpha versus beta) in human stratum corneum depends on its origin and environment, contrary to the commonly accepted alpha form for skin keratin. For common SC it would be close to beta, and for "callus" type it is alpha. An unknown beta-pleated sheet protein with an 9.4 angstrom interchain distance was inferred from the diffraction data. Reticular distances of the lipidic lamellar organization were evidenced by small-angle diffraction (10-65 angstrom). Wide angle diffraction (2.5-10 angstrom) showed intermolecular distances of different species of lipids. Certain features of the X-ray diagrams can be assigned (i.e., cholesterol). Liposomes, which are made also of organized lipids, can be characterized by an X-ray diagram. This fact is important for cosmetic research, providing the possibility to study the interaction between the stratum corneum and liposomes. Some examples will be reported.