Lipid tubes with a temperature-tunable diameter.
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Calorimetry, Differential Scanning↗
Biomedical subjects
Jean-Paul Douliez
Publications and source records attributed to Jean-Paul Douliez.
Novel lipid system forming hollow microtubes at high yields and concentration.
There is considerable interest in constructing supramolecular hollow tube architectures based on amphiphilic molecules. This can be achieved by using relatively expensive synthetic lipids. Herein, we report on the facile preparation of self-assembled microtubes from a novel low-cost lipid mixture that does not require a previous chemical synthesis step and consists of the ethanolamine salt of 12-hydroxy-stearic acid in water. Tubes of more than 10 microm in length spontaneously form upon cooling from an isotropic solution. They exhibit inner and outer diameters of 400 and 600 nm, respectively, and their walls consist of concentric stacked bilayers of fatty acid salts, each separated by a layer of water.
Journal Article↗
Self-assembly of fatty acid-alkylboladiamine salts.
Long-chain fatty acids are insoluble in aqueous solution and form crystal precipitates. It is then of particular importance to determine the physicochemical parameters allowing their dispersion in water to improve their bioavailability and their utilization as surfactants. Herein, we report a study on salt-free catanionic systems in aqueous solution made of mixtures between palmitic or stearic fatty acids and alkylboladiamines (Abd's) differing by their alkyl chain length. Phase contrast microscopy, solid-state NMR, Fourier transform infrared spectroscopy, and small-angle neutron scattering were used to characterize the phase behavior of these systems at molar ratio of fatty acid to Abd of 1 and 2. Whatever the Abd and the molar ratio, fatty acids were embedded at low temperature in a bilayer gel phase which crystallizes after a period of rest. At an equimolar ratio, the gel phases transited upon raising the temperature to an isotropic phase made of worm-like micelles except in the case of the ethylenediamine chain for which a lamellar fluid phase was observed. At a molar ratio of 2 and high temperature, fatty acids were embedded in a lamellar fluid phase which self-orients with its stacking axis perpendicular to the magnetic field. However, for a long alkylboladiamine such as spermine, worm-like micelles formed. The phase behavior at high temperature is discussed in terms of molecular volume.
Alkanes↗
Self-assembly of hollow cones in a bola-amphiphile/hexadiamine salt solution.
Cones are a very rare form of supramolecular self-assembly. It is shown that mixing of an unsymmetrical bola-fatty acid and a diamine (catanionic system) in dilute solutions can produce aggregates having a conical shape. These assemblies are made of frozen unsymmetrical monolayers in which bolas are arranged on a regular hexagonal lattice. Cones are stabilized by the introduction of pentagonal or n-gonal defects in the bola-lattice which yields the quantification of the cone apex angle according to the Euler theorems. The formation of cones represents a novel route for lipid and surfactant systems to minimize the edge energy of a flat membrane.
Diamines↗
Cutin and suberin monomers are membrane perturbants.
The interaction between cutin and suberin monomers, i.e., omega -hydroxylpalmitic acid, alpha, omega -hexadecanedioic acid, alpha, omega --hexadecanediol, 12-hydroxylstearic acid, and phospholipid vesicles biomimicking the lipid structure of plant cell membranes has been studied by optical and transmission electron microscopy, quasielastic light scattering, differential scanning calorimetry, and (31)P solid-state NMR. Monomers were shown to penetrate model membranes until a molar ratio of 30%, modulating their gel to fluid-phase transition, after which monomer crystals also formed in solution. These monomers induced a decrease of the phospholipid vesicle size from several micrometers to about 300 nm. The biological implications of these findings are discussed.
Calorimetry, Differential Scanning↗
Phase behavior of the palmitic acid/palmitin system. A 2H NMR study.
The phase behavior of mixtures of palmitic acid (PA) and 1-monohexadecanoyl-rac-glycerol, palmitin, was studied by phase contrast microscopy and deuterium solid-state NMR. At pH 5, mixtures remained precipitated as lumps in solution. The NMR spectrum of the perdeuterated PA (PAd31) at 300 K exhibited a shape and quadrupolar splittings, deltav, characteristic of lipids embedded in a gel phase. The alkyl chains remained in a trans conformation with their long molecular axis oriented at about 15 degrees with respect to the bilayer normal. However, gauche defects were shown to occur at the end of the alkyl chain. At 330 K, the system underwent a phase transition to a hexagonal phase followed by an isotropic phase at 340 K. Upon cooling to 330 K, the spectrum in the hexagonal phase was oriented at 0 degrees showing that the cylinders were oriented with their long axis parallel to the field. Up to 11 positions (from 15) of PAd31 could be assigned. At pH 7 and 9 at room temperature, the mixtures were fully dispersed in a viscous solution of vesicles. The system underwent a phase transition at 320 K from a gel phase to a fluid phase with the bilayer normal oriented at 90 degrees with respect to the field. Analogous experiments performed with PA selectively labeled on carbon C2 allowed for the assignment of deltav for that position and suggested different conformations of the headgroup in the gel and fluid or hexagonal phases. The implications of these findings for the bio-availability of these fatty acids, in the understanding of the contribution of hydroxyl and carboxyl groups in the membrane formation, and for the production of simple self-oriented systems are discussed.
Glycerides↗
Dynamic magnetic resonance microscopy of flour dough fermentation.
Magnetic resonance microscopy was carried out at 9.4 T with a voxel volume of 117 x 117 x 500 microm(3) and temporal resolution was adjusted to 8.5 min for a dynamic follow-up of bread dough fermentation during 2 h at a constant temperature of 30 degrees C. An image analysis procedure based on gray levels mathematical morphology routines was performed to assess bubble distribution and cell wall thickness inside the imaged bread dough. The evolution of the extracted curves allows one to characterize quantitatively the amount of bubbles and their growth. Using this procedure, different bread doughs were examined to determine the impact of dough composition on the structure modification during fermentation.
Fermentation↗
Formation of tubules and giant vesicles from large multilamellar vesicles.
This study reports an observation of submicrometer multilamellar vesicles (MLVs) prepared by simply freeze-thawing a phospholipid dispersion at full hydration that transformed into giant vesicles (GVs) and tubules (TUs) when confined between microscope glass slides. Cover slide cleaning and surface treatment did not hamper the formation of GVs or TUs. However, when small unilamellar vesicles (SUV) were prepared or when MLVs were not confined but rather freely moved between the glass slides or when the phospholipid was in its gel phase, neither GVs nor TUs were observed. Altogether, our results suggested that MLVs would play a role as a lipid reservoir and that the liquid flow between the glass slides induces the peeling of the external bilayers, yielding the formation of tubules and giant unilamellar vesicles.
Letter↗
Glycerol derivatives of cutin and suberin monomers: synthesis and self-assembly.
Glycerol derivatives of cutin and suberin monomers were synthesized by acid catalysis. Their dispersion in an aqueous solution was examined by phase contrast microscopy, neutron scattering, and solid state NMR. It is shown that the phase behavior strongly depends on the nature of the derivatives forming either lumps of aggregated membranes or well dispersed membranes.
Glycerol↗