title: Hexagonal phase with ordered acyl chains formed by a short chain asymmetric ceramide.
abstract: Ceramides constitute a group of lipids with usually high melting temperature that also favor negative curvature in membranes when mixed with other lipids. The short chain C10:0 ceramide is an asymmetric lipid which consists of an 18 carbon sphingosine base N-acylated with decanoic acid. According to high sensitivity differential scanning calorimetry, it shows a minor exothermic peak at 61°C and a main endothermic transition at 75°C. By small angle X-ray scattering and polarized light microscopy we found that, at temperatures below the main transition, the fully hydrated lipid dispersions are arranged in a tridimensional structure corresponding to an inverted hexagonal phase. Infrared spectroscopy and wide angle X-ray diffraction indicated that the acyl chains of ceramides exhibit a relatively high order in the hexagonal phase. As far as we know, this is the first report of a lipid hexagonal phase having highly ordered acyl chains. Molecular asymmetry due to the different length of the sphingosine and the N-acyl chains of C10:0 ceramide may explain why this novel phase is formed.
authors.affiliation: Instituto Superior de Investigaciones Biológicas (INSIBIO), CONICET-UNT, and Instituto de Química Biológica "Dr. Bernabé Bloj", Facultad de Bioquímica, Química y Farmacia, UNT. Chacabuco 461, T4000ILI San Miguel de Tucumán, Argentina.
authors.forename: F G
authors.initials: FG
authors.lastname: Dupuy
authors.affiliation: Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), FaMAF, Universidad Nacional de Córdoba, Argentina.
authors.forename: S P
authors.initials: SP
authors.lastname: Fernández Bordín
authors.affiliation: Centro de Investigaciones en Química Biológica de Córdoba, CIQUIBIC, CONICET and Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, X5000HUA Córdoba, Argentina.
authors.forename: B
authors.initials: B
authors.lastname: Maggio
authors.affiliation: Centro de Investigaciones en Química Biológica de Córdoba, CIQUIBIC, CONICET and Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, X5000HUA Córdoba, Argentina. Electronic address: oliveira@fcq.unc.edu.ar.
authors.forename: R G
authors.initials: RG
authors.lastname: Oliveira
mesh_terms: D000215:Acylation; D002236:Carbohydrate Conformation; D002518:Ceramides / Q000737:chemistry*; D003652:Decanoic Acids / Q000737:chemistry*; D044367:Phase Transition; D012996:Solutions; D013696:Temperature; D013816:Thermodynamics
chemical_list: D002518:Ceramides; D003652:Decanoic Acids; D012996:Solutions; C031071:decanoic acid
keywords: Asymmetry; Hexagonal phase; Short chain ceramide