title: Lipid domains and orthorhombic phases in model stratum corneum: evidence from Fourier transform infrared spectroscopy studies.
abstract: A three component model for the lipid barrier of the stratum corneum (SC) consisting of ceramide III, cholesterol, and perdeuterated palmitic acid, has been characterized by Fourier transform infrared spectroscopy. At physiological temperature the CD2 scissoring mode of the palmitic acid methylenes, and the CH2 rocking mode of the ceramide methylenes, are each split into two components. This indicates that both components exist in separate, conformationally ordered phases, probably with orthorhombic perpendicular subcells. The magnitude of the splitting indicates that the domains are at least 100 chains in size. The thermotropic behavior of the CD2 stretching vibrations demonstrates that conformational disordering of the palmitic acid commences at 42 degrees C with a transition midpoint of 50 degrees C. The CH2 stretching frequency indicates the ceramide chains remain ordered until 50 degrees C then disorder with a midpoint of 67 degrees C. The results provide a molecular characterization for the complex low temperature (10-40 degrees C) dynamic behavior suggested by recent 2H NMR experiments.
authors.affiliation: International Specialty Products, Skin R&D, Wayne, New Jersey 07470, USA. dmoore@ispcorp.com
authors.forename: D J
authors.initials: DJ
authors.lastname: Moore
authors.forename: M E
authors.initials: ME
authors.lastname: Rerek
authors.forename: R
authors.initials: R
authors.lastname: Mendelsohn
mesh_terms: D055592:Biophysical Phenomena; D001703:Biophysics; D002518:Ceramides / Q000737:chemistry; D002784:Cholesterol / Q000737:chemistry; D004817:Epidermis / Q000737:chemistry* / Q000648:ultrastructure; D008055:Lipids / Q000737:chemistry*; D008954:Models, Biological; D019308:Palmitic Acid / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature
chemical_list: D002518:Ceramides; D008055:Lipids; D019308:Palmitic Acid; D002784:Cholesterol