title: Synthesis and characterization of a new gemini surfactant derived from 3alpha,12alpha-dihydroxy-5beta-cholan-24-amine (steroid residue) and ethylenediamintetraacetic acid (spacer).
abstract: A new gemini steroid surfactant derived from 3alpha,12alpha-dihydroxy-5beta-cholan-24-amine (steroid residue) and ethylenediamintetraacetic acid (spacer) was synthesized and characterized in aqueous solution by surface tension, fluorescence intensity of pyrene, and light scattering (static and dynamic) measurements. These techniques evidence the existence of a threshold concentration (cac), below which a three layers film is formed at the air-water interface. Above the cac, two types of aggregates--micelles and vesicle-like aggregates--coexist in a metastable state. Filtration of a solution with a starting concentration of 2.6 mM (buffer 150 mM, pH 10) allows isolation of the micelles, which have an average aggregation number of 12, their density being 0.28 g cm(-3). Under conditions where only the vesicle-like aggregates are detected by dynamic light scattering, a value of 5.5 x 10(4) was obtained for their aggregation number at 30 microM, their density being 6.8 x 10(-4) g cm(-3). At high concentrations, the intensity ratio of the vibronic peaks of pyrene, I1/I3, (=0.68) is very close to published values for deoxycholate micelles, indicating that the probe is located in a region with a very low polarity and far from water. A hypothesis to explain the observed aggregation behavior (small aggregates are favored with increasing gemini concentration) is outlined.
authors.affiliation: Departamento de Química Física, Facultad de Ciencias, Universidad de Santiago de Compostela, Avenida Alfonso X El Sabio s/n, 27002 Lugo, Spain.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Alvarez Alcalde
authors.forename: Aida
authors.initials: A
authors.lastname: Jover
authors.forename: Francisco
authors.initials: F
authors.lastname: Meijide
authors.forename: Luciano
authors.initials: L
authors.lastname: Galantini
authors.forename: Nicolae Viorel
authors.initials: NV
authors.lastname: Pavel
authors.forename: Alvaro
authors.initials: A
authors.lastname: Antelo
authors.forename: José
authors.initials: J
authors.lastname: Vázquez Tato
mesh_terms: D000588:Amines / Q000737:chemistry*; D002021:Buffers; D002793:Cholic Acids / Q000737:chemistry*; D004492:Edetic Acid / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008823:Micelles; D046529:Microscopy, Electron, Transmission; D008956:Models, Chemical; D008968:Molecular Conformation; D008970:Molecular Weight; D012542:Scattering, Radiation; D013256:Steroids / Q000737:chemistry*; D013499:Surface Properties; D013501:Surface-Active Agents / Q000138:chemical synthesis* / Q000737:chemistry; D013816:Thermodynamics
chemical_list: C530421:3alpha,12alpha-dihydroxy-5beta-cholan-24-amine; D000588:Amines; D002021:Buffers; D002793:Cholic Acids; D008823:Micelles; D013256:Steroids; D013501:Surface-Active Agents; D004492:Edetic Acid