title: Micellization of dissymmetric cationic gemini surfactants and their interaction with dimyristoylphosphatidylcholine vesicles.
abstract: The micellization process of a series of dissymmetric cationic gemini surfactants [CmH2m+1(CH3)2N(CH2)6N(CH3)2C6H13]Br2 (designated as m-6-6 with m = 12, 14, and 16) and their interaction with dimyristoylphosphatidylcholine (DMPC) vesicles have been investigated. In the micellization process of these gemini surfactants themselves, critical micelle concentration (cmc), micelle ionization degree, and enthalpies of micellization (DeltaHmic) were determined, from which Gibbs free energies of micellization (DeltaGmic) and entropy of micellization (DeltaSmic) were derived. These properties were found to be influenced significantly by the dissymmetry in the surfactant structures. The phase diagrams for the solubilization of DMPC vesicles by the gemini surfactants were constructed from calorimetric results combining with the results of turbidity and dynamic light scattering. The effective surfactant to lipid ratios in the mixed aggregates at saturation (Resat) and solubilization (Resol) were derived. For the solubilization of DMPC vesicles, symmetric 12-6-12 is more effective than corresponding single-chain surfactant DTAB, whereas the dissymmetric m-6-6 series are more effective than symmetric 12-6-12, and 16-6-6 is the most effective. The chain length mismatch between DMPC and the gemini surfactants may be responsible for the different Re values. The transfer enthalpy per mole of surfactant within the coexistence range may be associated with the total hydrophobicity of the alkyl chains of gemini surfactants. The transfer enthalpies of surfactant from micelles to bilayers are always endothermic due to the dehydration of headgroups and the disordering of lipid acyl chain packing during the vesicle solubilization.
authors.affiliation: Key Laboratory of Colloid and Interface Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, People's Republic of China.
authors.forename: Yanru
authors.initials: Y
authors.lastname: Fan
authors.forename: Yajuan
authors.initials: Y
authors.lastname: Li
authors.forename: Meiwen
authors.initials: M
authors.lastname: Cao
authors.forename: Jinben
authors.initials: J
authors.lastname: Wang
authors.forename: Yilin
authors.initials: Y
authors.lastname: Wang
authors.forename: Robert K
authors.initials: RK
authors.lastname: Thomas
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D000475:Alkenes / Q000737:chemistry*; D002412:Cations; D008051:Lipid Bilayers / Q000737:chemistry*; D011726:Pyridinium Compounds / Q000737:chemistry*; D012542:Scattering, Radiation; D012995:Solubility; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D000475:Alkenes; D002412:Cations; D008051:Lipid Bilayers; D011726:Pyridinium Compounds; D013501:Surface-Active Agents; C523169:annulene gemini surfactant A; C523167:annulene gemini surfactant B; C523168:annulene gemini surfactant C; D015060:1,2-Dipalmitoylphosphatidylcholine