Ufasomes are Stable Particles surrounded by Unsaturated Fatty Acid Membranes

Gebicki, Janusz M.; Hicks, Mark

doi:10.1038/243232a0

Cited by 337 publications

(228 citation statements)

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“…Obviously, chemical modifications of fatty acids can yield to an increase of fatty acid solubility but others methods can be applied without any modification of the fatty acid molecule [3]. More than 40 years ago, Gebicki and Hicks reported the dispersion of oleic acid in vesicles in an aqueous solution [14]. The bilayer of these vesicles is formed by both the non-ionized and ionized forms of the fatty acid molecule.…”

Section: 2) Self-assemblies Based On Fatty Acids In Aqueous Solutionmentioning

confidence: 99%

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Responsive self-assemblies based on fatty acids

Fameau

Arnould

Saint‐Jalmes

2014

Current Opinion in Colloid & Interface Science

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Section: 2) Self-assemblies Based On Fatty Acids In Aqueous Solutionmentioning

confidence: 99%

“…By adding NaOH, the pH increases leading higher ratio of ionized to protonated molecules and micelles are the dominant self-assembly [14,33,34]. When the pH is decreased by…”

Section: 1) Ph Effectmentioning

confidence: 99%

Responsive self-assemblies based on fatty acids

Fameau

Arnould

Saint‐Jalmes

2014

Current Opinion in Colloid & Interface Science

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“…The morphology of the mixture depends on pH and ionic strength (I). [9][10][11] In I = 0.1 pH 8-10 aqueous media, oleates form vesicles (Fig. 2a).…”

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Macroscopic motion of supramolecular assemblies actuated by photoisomerization of azobenzene derivatives

et al. 2013

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Submillimetre size self-assemblies composed of oleate and azobenzene derivatives show forceful motions such as screwtype coiling-recoiling motion by photoirradiation.In the past half century, many molecular-level machines which 10 change their molecular structure upon exposure to stimuli have been reported. 1 Nowadays, studies on macroscopic thermal motion of soft matters received attentions from the viewpoint of biomimetics. 2,3 Next key step for soft matters is to create a material whose macroscopic motion is controlled by external 15 stimuli. 4 One of the strategies is to create soft materials consisting of subunits sensitive to external inputs, for instance, the photoinduced bending of polymer films consisted of azobenzene derivatives. 5,6 Another strategy is to create soft materials in which macroscopic motions of molecular assemblies 20 are actuated by small amount of molecular machines. 7 To date, there are few reports describing macroscopic mechanical behaviour based on the latter strategy. 8 Here, we report reversible and spatially controlled macroscopic motion of oleate assembles which have submillimetre length. 25Mixtures of oleic acid (1H) and oleate (1 -) ( Fig. 1) are capable of self-assembly in aqueous solution. The morphology of the mixture depends on pH and ionic strength (I). [9][10][11] In I = 0.1 pH 8-10 aqueous media, oleates form vesicles (Fig. 2a). Between pH 7 and 8, they form several complex aggregates called "blocks" that 30 exhibit an inverted hexagonal phase 12 (Fig. 2b). In the transition region, helical and straight multilayer assemblies are coexisted with vesicles and blocks. 11 It is considered that the shape of assembly depends on the ratio of 1H and 1 -in each assembly. According to the microscopic observations of shape and 35 dynamics described in Ref. 11, the helical assemblies are sufficiently flexible to change their macroscopic helical pitch and curvature, but are also elastic because of the highly-ordered stacking structure of oleate molecules in the assembly. As demonstrated in Fig. 3, the helical assemblies exhibit a highly 40 elastic response to mechanical stress. We assumed that this softness and elasticity of the self-assembly is suitable to the spatially moving material in which motion of molecular machine should be propagated.Azobenzene derivatives 2-5 ( Fig. 1) display reversible 2-5 by addition of 70 mM KH 2 PO 4 -K 2 HPO 4 buffer solution (1.0 mL) and sonication for 20 min. A 125 µL aliquot of each suspension containing one of 2-5 was placed in a sealed microscope slide and incubated for 1 day at 25°C. All 60 azobenzene derivatives dissolved into oleate assemblies. The pH range required for formation of helical assemblies was slightly lowered by the addition of 2-5. 14 Helical assemblies were formed when pH 7.3 buffer solution was used as the dispersing medium (the pH of the dispersion was approximately 7.5); pH 65 values of buffer solution higher than 7.3 resulted in vesicle formation, and pH values lower than 7.3 led to the formation of

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“…28), which is consistent with the thermodynamics of vesicle systems (29). These preparations can be extruded through small-pore filters to yield vesicles of a defined size (30) that are stable for at least several hours (3,25). Under these conditions, fatty acid micelles and free molecules are present in equilibrium with vesicles at a concentration equal to the critical aggregate concentration (cac), which is similar to a phase equilibrium (1,31).…”

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confidence: 99%

“…Although previous work on proton and cation permeation has focused on pure phospholipid membranes or phospholipid membranes doped with a small amount of fatty acid, fatty acids themselves form negatively charged vesicles when prepared at a pH close to the pK a of the acid when incorporated into the membrane (25)(26)(27). Vesicles are initially formed as an aqueous dispersion of fatty acid, with a highly polydisperse size distribution (50 nm to several microns in diameter; ref.…”

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Membrane growth can generate a transmembrane pH gradient in fatty acid vesicles

Chen

Szostak²

2004

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

144

140

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Electrochemical proton gradients are the basis of energy transduction in modern cells, and may have played important roles in even the earliest cell-like structures. We have investigated the conditions under which pH gradients are maintained across the membranes of fatty acid vesicles, a model of early cell membranes. We show that pH gradients across such membranes decay rapidly in the presence of alkali-metal cations, but can be maintained in the absence of permeable cations. Under such conditions, when fatty acid vesicles grow through the incorporation of additional fatty acid, a transmembrane pH gradient is spontaneously generated. The formation of this pH gradient captures some of the energy released during membrane growth, but also opposes and limits further membrane area increase. The coupling of membrane growth to energy storage could have provided a growth advantage to early cells, once the membrane composition had evolved to allow the maintenance of stable pH gradients.

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Ufasomes are Stable Particles surrounded by Unsaturated Fatty Acid Membranes

Cited by 337 publications

References 10 publications

Responsive self-assemblies based on fatty acids

Responsive self-assemblies based on fatty acids

Macroscopic motion of supramolecular assemblies actuated by photoisomerization of azobenzene derivatives

Membrane growth can generate a transmembrane pH gradient in fatty acid vesicles

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