title: Ca2+- and ba2+-ligand coordinated unilamellar, multilamellar, and oligovesicular vesicles.
abstract: Ca(2+)- and Ba(2+)-coordinated vesicle phases were prepared in mixed aqueous solutions of tetradecyldimethylamine oxide (C(14)DMAO) and calcium oleate (Ca(OA)(2)) or barium oleate (Ba(OA)(2)). At the right mixing ratios, metal-ligand coordination between Ca(OA)(2) or Ba(OA)(2) and C(14)DMAO results in the formation of molecular bilayers due to the reduction in area per head group. Ca(2+) and Ba(2+) tightly associate to the head groups of surfactants and in this system the bilayer membranes are not shielded by excess salts. The structures of the birefringent samples of the Ca(OA)(2)/C(14)DMAO/H(2)O and Ba(OA)(2)/C(14)DMAO/H(2)O systems were determined by freeze-fracture transmission electron microscopy (FF-TEM), small-angle X-ray scattering (SAXS), and rheological measurements to consist of unilamellar, multilamellar, and oligovesicular vesicles. The coordination between C(14)DMAO and Ba(OA)(2) or Ca(OA)(2) plays an important role in the formation of the vesicles, which was easily confirmed by studying the phase behavior of the KOA/C(14)DMAO/H(2)O system in which only the L(1) phase forms, due to the absence of coordination between KOA and C(14)DMAO. A mechanism is proposed that accounts for the formation of these new metal-ligand coordinated vesicles.
authors.affiliation: Key Laboratory of Colloid and Interface Chemistry, Shandong University, Ministry of Education, Jinan 250100, China.
authors.forename: Aixin
authors.initials: A
authors.lastname: Song
authors.forename: Xiangfeng
authors.initials: X
authors.lastname: Jia
authors.forename: Minmin
authors.initials: M
authors.lastname: Teng
authors.forename: Jingcheng
authors.initials: J
authors.lastname: Hao
mesh_terms: D001464:Barium / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry*; D004123:Dimethylamines / Q000737:chemistry*; D004553:Electric Conductivity; D005614:Freeze Fracturing; D008081:Liposomes / Q000138:chemical synthesis / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular; D015394:Molecular Structure; D009227:Myristic Acids / Q000737:chemistry*; D019301:Oleic Acid / Q000737:chemistry*; D044367:Phase Transition; D053838:Scattering, Small Angle; D013501:Surface-Active Agents / Q000737:chemistry*; D053835:Unilamellar Liposomes / Q000138:chemical synthesis / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D004123:Dimethylamines; D008081:Liposomes; D009227:Myristic Acids; D013501:Surface-Active Agents; D053835:Unilamellar Liposomes; D001464:Barium; D019301:Oleic Acid; C518255:myristyldimethylamine oxide; D002118:Calcium