title: Cholesteryl sulphate and phosphate in the solid state and in aqueous systems.
abstract: Cholesteryl sodium sulphate (CS) crystallizes as the dihydrate, the crystal structure of which is known. On heating the dihydrate, solid state phase transitions are observed at 65 degrees C and 95 degrees C and melting occurs at 165 degrees C. The structure of the high temperature phase has not been determined. Cholesteryl dihydrogen phosphate (CP) is not isostructural with any phases of CS. It undergoes a phase transition at 50 degrees C and melts at 190 degrees C. In systems with water CS is unstable whereas it was possible to determine the phase diagram of CP. In most of the composition range a crystalline hydrate is in equilibrium with a gel-phase. The latter has remarkable properties in that lamellar order exists with the 46 A lipid bilayer interleaved with water layers up to 1000 A. The monofilm behaviour of CS and CP at different pH levels is also reported.
mesh_terms: D002784:Cholesterol; D003460:Crystallization; D008968:Molecular Conformation; D009943:Organophosphorus Compounds; D011312:Pressure; D013463:Sulfuric Acid Esters; D013499:Surface Properties; D014867:Water; D014961:X-Ray Diffraction
chemical_list: D009943:Organophosphorus Compounds; D013463:Sulfuric Acid Esters; D014867:Water; D002784:Cholesterol