title: Structure and phase behavior of O-stearoylethanolamine: a combined calorimetric, spectroscopic and X-ray diffraction study.
abstract: Recent studies show that O-acylethanolamines (OAEs), structural isomers of the putative stress-fighting lipids, namely N-acylethanolamines (NAEs), can be derived from NAEs and are present in biological membranes under physiological conditions. In view of this, we have synthesized O-stearoylethanolamine (OSEA) as a representative OAE and investigated its phase behavior and crystal structure. The thermotropic phase transitions of OSEA dispersed in water and in 150mM NaCl were characterized using calorimetric, spectroscopic, turbidimetric and X-ray diffraction studies. These studies have revealed that when dispersed in water OSEA undergoes a cooperative phase transition centered at 53.8 degrees C from an ordered gel phase to a micellar structure whereas in presence of 150mM NaCl the transition temperature increases to 55.8 degrees C and most likely the bilayer structure is retained above the phase transition. O-Stearoylethanolamine crystallized in the orthorhombic space group P2(1)2(1)2(1) with four symmetry-related molecules in the unit cell. Single-crystal X-ray diffraction studies show that OSEA molecules adopt a linear structure with all-trans conformation in the acyl chain region. The molecules are organized in a tail-to-tail fashion, similar to the arrangement in a bilayer membrane. These studies are relevant to understanding the role of salt on the phase properties of this new class of lipids.
authors.affiliation: School of Chemistry, University of Hyderabad, Hyderabad-500046, India.
authors.forename: Pradip K
authors.initials: PK
authors.lastname: Tarafdar
authors.forename: Musti J
authors.initials: MJ
authors.lastname: Swamy
mesh_terms: D002152:Calorimetry, Differential Scanning / Q000379:methods*; D004578:Electron Spin Resonance Spectroscopy; D004983:Ethanolamines / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D015394:Molecular Structure; D009391:Nephelometry and Turbidimetry; D044367:Phase Transition; D012492:Salts / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013229:Stearic Acids / Q000737:chemistry*; D014961:X-Ray Diffraction / Q000379:methods*
chemical_list: D004983:Ethanolamines; D012492:Salts; D013229:Stearic Acids