The lamellar and sponge phases of dilute surfactant systems: Structures and defects at equilibrium and under shear

Kléman, M.

doi:10.1007/s12043-999-0143-3

Cited by 7 publications

(10 citation statements)

References 27 publications

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“…We expected that the obtained DNA/C 12 JC n lipoplexes would create liposomal, lamellar or sponge-phase structures, as suggested by previous SAXS studies of similar systems. [28][29][30][31][32][33] Structural characterisation of dsDNA and C 12 JC n /dsDNA lipoplexes To obtain information on the structure of the studied initial dsDNA oligomer in solution and the microstructures of dsDNA complexes with gemini surfactants, we utilised the SAXS technique. We rst performed shape determination studies for the dsDNA molecule in solution using the DAMMIN 34 program from the ATSAS soware package.…”

Section: Resultsmentioning

confidence: 99%

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The study of complexation between dicationic surfactants and the DNA duplex using structural and spectroscopic methods

et al. 2017

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Section: Resultsmentioning

confidence: 99%

“…For C 12 JC 4 lipoplexes, we also observed an additional peak, which can be ascribed to stacked DNA (s DNA ¼ 1.59 nm À1 ). For the next group of lipoplexes, prepared using C 12 JC 5 and C 12 JC 6 surfactants, the highest concentrations of surfactant (p/n 3-5) produced a liposomal-like or even sponge phase [28][29][30][31][32][33] (Fig. 8e).…”

Section: Resultsmentioning

confidence: 99%

The study of complexation between dicationic surfactants and the DNA duplex using structural and spectroscopic methods

et al. 2017

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“…In this context, the studies have been restricted to the swollen L α or L 3 phase with highly flexible bilayers dominated by steric repulsion, where the transitions occur due to shearinduced suppression of thermal fluctuations above a critical shear rate of _ γ c (19). Because _ γ c ∼ ϕ n , where ϕ is the surfactant volume fraction and the exponent n lies (18) in the range of 1.5-3, the transitions are absent for ϕ > 0.3 within the experimentally accessible range of shear rates (∼1,000 s −1 ) (20). Our present study is different from the earlier studies on sponge phases because it examines the role of steady shear in weakly swollen, concentrated (ϕ > 0.5) isotropic phases (15,21) …”

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confidence: 94%

Reversible shear-induced crystallization above equilibrium freezing temperature in a lyotropic surfactant system

Rathee

Krishnaswamy

Pal

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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We demonstrate a unique shear-induced crystallization phenomenon above the equilibrium freezing temperature ðT o K Þ in weakly swollen isotropic ðL i Þ and lamellar ðL α Þ mesophases with bilayers formed in a cationic-anionic mixed surfactant system. Synchrotron rheological X-ray diffraction study reveals the crystallization transition to be reversible under shear (i.e., on stopping the shear, the nonequilibrium crystalline phase L c melts back to the equilibrium mesophase). This is different from the shear-driven crystallization below T o K , which is irreversible. Rheological optical observations show that the growth of the crystalline phase occurs through a preordering of the L i phase to an L α phase induced by shear flow, before the nucleation of the L c phase. Shear diagram of the L i phase constructed in the parameter space of shear rate ð_ γÞ vs. temperature exhibits L i → L c and L i → L α transitions above the equilibrium crystallization temperature ðT o K Þ, in addition to the irreversible shear-driven nucleation of L c in the L i phase below T o K . In addition to revealing a unique class of nonequilibrium phase transition, the present study urges a unique approach toward understanding shear-induced phenomena in concentrated mesophases of mixed amphiphilic systems.shear-induced phase separation | strongly binding counterions | coagels S hear is known to assist crystallization below the equilibrium freezing temperature in complex fluids like colloidal glasses (1, 2), dense granular suspensions (3), polymer melts (4, 5), micellar solutions of block copolymers (6), and multicomponent surfactant systems (7,8). Shear-driven crystallization is equally relevant for simple fluids like bulk metallic glasses (9), molecular liquids (10), and atomic systems (11). The general understanding is that shear lowers the energy barrier for nucleation and accelerates the growth of a stable crystalline phase from a metastable, amorphous/ isotropic solution at Peclet number Pe = σa 3 kBT > 1, where σ is the shear stress, a is the characteristic length scale, and k B T is the thermal energy (12). The crystalline phase primarily induced by the effect of flow on the internal structure and ordering of the constituents does not revert to the starting fluid state when the imposed shear is removed, indicating that the phenomenon is not a dynamic phase transition. In the present study, we report a unique phenomenon, where under steady shear, crystallization occurs above the equilibrium crystallization temperature ðT o K Þ in an isotropic mesophase ðL i Þ consisting of bilayers formed in a lyotropic surfactant system. Notably, above T o K , when the imposed shear is removed, the crystalline phase melts back to the starting L i phase.The studies were carried out in a cationic-anionic mixed surfactant system formed by SDS and the strong binding counter-ion paratoluene hydrochloride (PTHC) in water. At equilibrium, the organic counter-ion PTHC has the tendency to remain at the micelle-water interface, decreasing the spontaneous curvat...

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“…To do so, we use a system of model bilayers, called “sponge” phase (or L 3 ) [13], some of which have been successfully used to crystallize membrane protein [14]. This phase consists of a randomly connected, continuous membrane.…”

Section: Introductionmentioning

confidence: 99%

“…The first step is to incorporate membrane proteins inside bilayers whose separation can be controlled at will in a kind of “soft” Surface Force Apparatus geometry. To do so, we use a system of model bilayers, called “sponge” phase (or L 3 ) [13] , some of which have been successfully used to crystallize membrane protein [14] . This phase consists of a randomly connected, continuous membrane.…”

Section: Introductionmentioning

confidence: 99%

Tracking Membrane Protein Association in Model Membranes

et al. 2009

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Membrane proteins are essential in the exchange processes of cells. In spite of great breakthrough in soluble proteins studies, membrane proteins structures, functions and interactions are still a challenge because of the difficulties related to their hydrophobic properties. Most of the experiments are performed with detergent-solubilized membrane proteins. However widely used micellar systems are far from the biological two-dimensions membrane. The development of new biomimetic membrane systems is fundamental to tackle this issue.We present an original approach that combines the Fluorescence Recovery After fringe Pattern Photobleaching technique and the use of a versatile sponge phase that makes it possible to extract crucial informations about interactions between membrane proteins embedded in the bilayers of a sponge phase. The clear advantage lies in the ability to adjust at will the spacing between two adjacent bilayers. When the membranes are far apart, the only possible interactions occur laterally between proteins embedded within the same bilayer, whereas when membranes get closer to each other, interactions between proteins embedded in facing membranes may occur as well.After validating our approach on the streptavidin-biotinylated peptide complex, we study the interactions between two membrane proteins, MexA and OprM, from a Pseudomonas aeruginosa efflux pump. The mode of interaction, the size of the protein complex and its potential stoichiometry are determined. In particular, we demonstrate that: MexA is effectively embedded in the bilayer; MexA and OprM do not interact laterally but can form a complex if they are embedded in opposite bilayers; the population of bound proteins is at its maximum for bilayers separated by a distance of about 200 Å, which is the periplasmic thickness of Pseudomonas aeruginosa. We also show that the MexA-OprM association is enhanced when the position and orientation of the protein is restricted by the bilayers. We extract a stoichiometry for the complex that exhibits a strong pH dependance: from 2 to 6 MexA per OprM trimer when the pH decreases from 7.5 to 5.5.Our technique allows to study membrane protein associations in a membrane environment. It provides some challenging information about complexes such as geometry and stoichiometry.

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The lamellar and sponge phases of dilute surfactant systems: Structures and defects at equilibrium and under shear

Cited by 7 publications

References 27 publications

The study of complexation between dicationic surfactants and the DNA duplex using structural and spectroscopic methods

The study of complexation between dicationic surfactants and the DNA duplex using structural and spectroscopic methods

Reversible shear-induced crystallization above equilibrium freezing temperature in a lyotropic surfactant system

Tracking Membrane Protein Association in Model Membranes

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