Vesicle-to-micelle transition

P Schurtenberger, NA Mazer, W Kanzig. Dynamic laser-light-scattering studies of the micelle to vesicle transition in a model and native bile. Hepatology 4 143-147, 1984. 

Salkar, R.A. Mukesh, D. Samant, S.D. Manohar, C. Mechanism of micelle to vesicle transition in cationic-anionic surfactant mixtures. Langmuir 1998, 14, 3778-3782. 

Rg. 16 Structure and multistimuli-responsive micelle to vesicle transition. Adapted with permission from ref. 84. Copyright 2012 John Wiley and Sons. 

Egelhaaf, S.U. and Schurtenberger, R, Micelle-to-vesicle transition A time-resolved structural study. Physical Rev. Letts., 82, 2804, 1999. 

A series of cationic gemini surfactants, alkanediyl-ot,a)-bis[di(2-hydro-xylethyl) dodecylammonium] dibromide (abbreviated as 12-S-12 (OH), with s = 4, 6, 8 and 10 methylenes) have been synthesized, and their aggregation properties in aqueous solution have been studied by surface tension, calorimetry, H NMR, DLS, and TEM. Two critical aggregation concentrations are observed for these surfactants. These surfactants start to form dimers at concentrations well below their critical micelle concentrations (CMC). Above the CMC, these surfactants can form both micelles and vesicles spontaneously with a micelle-to-vesicle transition.The formation and characterization of catanionic vesicles by newly synthesized lysine- and... 

Blume and coworkers have pioneered the use of isothermal titration calorimetry and differential scanning calorimetry in studies of micelle-to-vesicle transitions induced by increasing the temperature. Specifically the system DMPC/SDS has been studied, and some hysteresis effects were observed based on study of both the heating and cooling cycles. 

Egelhaaf et al. have studied the kinetics of the micelle-to-vesicle transition when lecithin/cholesterol/bile salt micelles... 

Interactions between oppositely charged micelles in aqueous solutions spontaneously form vesicles. The self-diffusion coefficient of water and 2H relaxation of 2H-labeled dodecyl trimethyl ammonium chloride of the dodecyl trimethyl ammonium chloride-sodium dodecyl benzenesulfonate systems show that in these mixtures there is limited growth of the micelles with changes in composition. The vesicles abruptly begin to form at a characteristic mixing ratio of the two surfactants. The transition is continuous.205 Transformation from micelle to vesicle in dodecyl trimethyl ammonium chloride-sodium perfluoro-nonanoate aqueous solution has been studied by self-diffusion coefficient measurements, and it was found that at a concentration of 35 wt% with a molar ratio of 1 1, the self-diffusion coefficient of the mixed micelles is far smaller than that of the two individual micelles.206 The characteristics of mixed surfactant... 

What is noteworthy about the series is that for the monatomic alkali metal cations their order does not agree with their size or charge density or their lyotropic series (Voet 1937b). This apparent disorder (note the position of Cs+) is not universal, however, since cases where the lyotropic series is followed are also known. An instance is the rate of the penetration of the alkali metal cations through leaf cuticles that decreases in the order Cs+ >Rb+ > K+ > Na+ > Li+, i.e., in the expected order according to their surface charge densities. The cuticular pores were supposed by McFarlane and Berry to be lined with a protein that has exposed positive sites (McFarlane and Berry 1974). The critical micelle concentration (cmc) of sodium dodecylsulphate increases in the reverse order by these cations (Maiti et al. 2009), where Cs+ is at the expected position. The transition of a mixed surfactant (sodium dodecylsulfate + dodecyltrimethylammonium bromide with an excess of the former) from micelles to vesicles (Sect. 4.5) is also promoted in this sequence, explained by counter-ion association depending on relative ease of ion dehydration (Renoncourt et al. 2007). 

Priya MH, Shah JK, Asthagiri D, Paulaitis ME (2008) Distinguishing thermodynamic and kinetic views of the preferential hydration of protein surfaces. Biophys J 95 2219-2225 Renoncourt A, Vlachy N, Bauduin P, Drechsler M, Touiaud D, Veibavatz J-M, Dubois M, Kunz W, Ninham BW (2007) Specific alkati cation effects in the transition from micelles to vesicles through salt addition. Langmuir 23 2376-2381... 

O. Soderman, K. L. Herrington, E. W. Kaler and D. D. Miller, Transition from micelles to vesicles... 

CrystaUisation of biliary cholesterol monohydrate is a multiphase process not yet fuUy understood [60]. Bile is normally supersaturated with respect to cholesterol [61] which is solubilised by bile salts (the soluble end product of cholesterol metabolism, such as sodium glycocholate and sodium taurocholate [9]) within micelles, whose solubilising capacity is considerably increased by the incorporation of phosphohpid molecules such as lecithin [62]. Biliary vesicles contain virtually no bile salts but may accumulate cholesterol up to a cholesterol/phosphohpid ratio of 2 1 (by phospholipid transfer to micelles) [63]. These thermodynamically unstable (but kinetically stabilised) vesicles then aggregate and nucleate cholesterol crystals [64,65]. The mechanism of this crucial miceUe-to-vesicle transition has been the subject of various physicochemical studies, including, e.g. calorimetric, turbidimetric, dynamic light and neutron scattering methods [66-69]. 

Doubtlessly, lipid membranes are among the most important biological interfaces. They control transport of molecules in and out of the cell and are responsible for cell adhesion, fusion, etc. The ions in the aqueous medium around the membranes play a significant role for the surface potential, the dipole potential, the structure and dynamics of the lipids, the transition from micelles to vesicles, etc. Relevant references on these different aspects can be found in the paper by Garcia-Celma et Furthermore, it is still mostly trial and erroneous to extract proteins out of membranes and to stabilise them at convient pH with detergents and added salts. 

Micellar structure has been a subject of much discussion [104]. Early proposals for spherical [159] and lamellar [160] micelles may both have merit. A schematic of a spherical micelle and a unilamellar vesicle is shown in Fig. Xni-11. In addition to the most common spherical micelles, scattering and microscopy experiments have shown the existence of rodlike [161, 162], disklike [163], threadlike [132] and even quadmple-helix [164] structures. Lattice models (see Fig. XIII-12) by Leermakers and Scheutjens have confirmed and characterized the properties of spherical and membrane like micelles [165]. Similar analyses exist for micelles formed by diblock copolymers in a selective solvent [166]. Other shapes proposed include ellipsoidal [167] and a sphere-to-cylinder transition [168]. Fluorescence depolarization and NMR studies both point to a rather fluid micellar core consistent with the disorder implied by Fig. Xm-12. 

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