Spontaneous vesicles, disks, threadlike and spherical micelles found in the solubilization of DMPC liposomes by the detergent DTAC

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• 作者：Raquel F. Correia^a ; Maria Isabel Viseu^a ; ^{isabelviseu@ist.utl.pt} ; Telmo J.V. Prazeres^b ; José ; M.G. Martinho^b
• 关键词：1 ; 2-Dimyristoyl-sn-glycero-3-phosphocholine ; Dodecyltrimethylammonium chloride ; Chlorophyll-a ; Liposomes ; Discoidal micelles ; Cylindrical micelles ; Neutral-sphere-equivalent hydrodynamic diameters ; Spontaneous colloidal nanostructures
• 刊名：Journal of Colloid and Interface Science
• 出版年：2012
• 期刊代码：125_00219797
• 类别：ch
• 出版时间：1 August, 2012
• 卷：379
• 期：1
• 页码：56-63
• 文件大小：904 K

摘要

The spontaneous colloidal nanostructures formed in water by the zwitterionic phospholipid DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) with the cationic detergent DTAC (n-dodecyltrimethylammonium chloride) were investigated at a fixed DMPC concentration and variable detergent:lipid total molar ratios (D:L). Apparent (neutral-sphere-equivalent) hydrodynamic diameters (桅_e) of liposomes and micelles were obtained by dynamic light scattering (DLS). Fluorescence lifetime imaging microscopy (FLIM), using chlorophyll-a as a probe, showed the morphology of giant vesicles and threadlike micelles. Micro-differential scanning calorimetry (micro-DSC) detected the presence of bilayers, in vesicles and discoidal micelles (disks). Pure DMPC liposomes are multilamellar and polydisperse (桅_e 鈮?#xA0;100-10,000 nm). As D:L increased, smaller vesicles were found, due to the bigger spontaneous curvature of the bilayer: at D:L = 1, ULVs (unilamellar vesicles; 桅_e 鈮?#xA0;100 nm) appeared and, at D:L = 2-10, ULVs coexisted with disks (桅_e 鈮?#xA0;30 nm). Bilayers totally disappeared at D:L 猢?#xA0;15, giving rise to spheroidal (桅_e 鈮?#xA0;2-16 nm) and threadlike (桅_e 鈮?#xA0;100-10,000 nm) micelles. A quasi-equilibrium structural diagram for the DMPC-DTAC-water system shows equivalent diameters of the scattering nanoparticles as a function of D:L. The results obtained herein for the system DMPC-DTAC show the role of electrostatic interactions in the formation of the mixed structures.