Kinetic asymmetry in the gel-liquid crystalline state transitions of DDAB vesicles studied by differential scanning calorimetry

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Spontaneous vesicles of sodium dihexadecylphosphate in HEPES buffer

The formation of spontaneous vesicles of dihexadecylphosphate (DHP) in a HEPES buffered solution at pH 7.4, the size, morphology and melting temperature, obtained by cryogenic transmission electron microscopy (cryo-TEM) and differential scanning calorimetry (DSC), are reported. The vesicles were formed by simply mixing a 5.0 mM lipid-solvent mixture at a temperature (75 degrees C) safely above the higher melting temperature T-m = 70.4 degrees C of DHP. The vesicle diameter ranges from 100 to 332 nm and their geometry is spherical, faceted or oblong. T-m increases from 66.8 to 70.4 as DHP concentration is raised from 0.6 to 5.0 mM. (c) 2008 Elsevier B.V. All rights reserved.

New Insight into the Mechanism of Action of Wasp Mastoparan Peptides: Lytic Activity and Clustering Observed with Giant Vesicles

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The role of counterion on the thermotropic phase behavior of DODAB and DODAC vesicles

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Anticardiolipin antibodies from syphilis and systemic lupus erythematosus induce leakage in cardiolipin vesicles

Anticardiolipin antibodies from sera of patients with systemic lupus erythematosus or syphilis induced leakage of entrapped carboxyfluorescein (CF) from cardiolipin (CL)/phosphatidylcholine(PC) vesicles prepared by sonication of equimolar mixtures of CL:PC. The sera dilution used here was 1:7500. IgG (5-20 mu g/ml) from the same sera, not containing beta(2)GPI, also produced a concentration-dependent leak. Vesicle leakage was inhibited by salt and was not detected with vesicles prepared exclusively with phosphatidylcholine. The demonstration of antibody-induced vesicle leakage offers a convenient system to investigate the mechanism of antibody-lipid binding as well as a potential diagnostic tool.

Unilamellar vesicles obtained by simply mixing dioctadecyldimethylammonium chloride and bromide with water

Optically clear dispersions of dioctadecyldimethylammonium bromide and chloride (DODAX, X = Br-, Cl-) in water can be obtained by simply mixing the amphiphiles at low concentrations (I mM) and at a temperature safely above the gel to liquid crystalline phase transition temperature (T-m approximate to 45-48 degrees C) of DODAX in water. Under these conditions, dynamic light scattering shows that, at room temperature, the dispersions contain two well-defined populations of large vesicles with average hydrodynamic radii (RH) of 80 and 337 nm for DODAB and of 69 and 247 nm for DODAC. Cryo-transmission electron microscopy (cryo-TEM) micrographs show that DODAX vesicles are unilamellar and polydisperse with apparent radius up to 800 nm. The vesicles are stable for at least I month according to the ageing time-dependence of the turbidity and molar absorption coefficient. (c) 2006 Elsevier B.V.. All rights reserved.

INTEGRATION OF THE NONLINEAR POISSON BOLTZMANN-EQUATION FOR CHARGED VESICLES IN ELECTROLYTIC SOLUTIONS

The Poisson-Boltzmann equation (PBE), with specific ion-surface interactions and a cell model, was used to calculate the electrostatic properties of aqueous solutions containing vesicles of ionic amphiphiles. Vesicles are assumed to be water- and ion-permeable hollow spheres and specific ion adsorption at the surfaces was calculated using a Volmer isotherm. We solved the PBE numerically for a range of amphiphile and salt concentrations (up to 0.1 M) and calculated co-ion and counterion distributions in the inside and outside of vesicles as well as the fields and electrical potentials. The calculations yield results that are consistent with measured values for vesicles of synthetic amphiphiles.

Toxicity of chronic ethanol ingestion and superoxide radical formation on seminal vesicles of rats

The toxic effects of chronic ethanol ingestion were evaluated in male adult rats for 300 days. The animals were divided into three groups: the controls received only tap water as liquid diet; the chronic ethanol ingestion group received only ethanol solution (30%) in semivoluntary research; and the withdrawal group received the same treatment as chronic ethanol-treated rats until 240 days, after which they reverted to drinking water. Chronic ethanol ingestion induced increased lipoperoxide levels and acid phosphatase activities in seminal vesicles. Cu-Zn superoxide dismutase (SOD) decreased from its basal level 70.8 +/- 3.5 to 50.4 +/- 1.6 U/mg protein at 60 days of chronic ethanol ingestion. As changes in GSH-PX activity were observed in rats after chronic ethanol ingestion, while SOD activities were decreased in these animals, it is assumed that superoxide anion elicits lipoperoxide formation and induces cell damage before being converted to hydrogen peroxide by SOD. Ethanol withdrawal induced increased SOD activity and reduced seminar vesicle damage, indicating that the toxic effects were reversible, since increased SOD activity was adequate to scavenge superoxide radical formation. Superoxide radical is an important intermediate in the toxicity of chronic ethanol ingestion. Copyright (C) 1996 Elsevier B.V. Ltd

Dioctadecyldimethylammonium bromide vesicles prepared by the surfactant removal method

Dioctadecyldimethylammonium bromide (DODAB) is a double chain vesicle-forming cationic surfactant, whereas octa-ethyleneglycol mono-n-dodecyl ether (C12E8) is a single chain micelle-forming nonionic surfactant. At room temperature (ca. 22 degrees C) C12E8 molecules self-assemble in water as micelles while DODAB is insoluble. A mixture of DODAB and C12E8, however, can be soluble in water at room temperature depending on the relative amount of the compounds. We report the formation of small unilamellar vesicles (SUVs) by dialyzing at room temperature a mixture of 1.0 mM DODAB with 10 mM C12E8 in water. Extended bilayers are formed as well in equilibrium with vesicles. Such structures are viewed by a cryogenic transmission electron microscopy (cryo-TEM) image. (c) 2006 Elsevier B.V. All rights reserved.

Size, electrophoretic mobility, and ion dissociation of vesicles prepared with synthetic amphiphiles

Vesicles prepared with synthetic amphiphiles (dioctadecyldimethylammonium bromide and chloride, dihexadecyl phosphate and its sodium salt) were obtained by sonication, ethanol injections, and chloroform injections. The hydrodynamic diameter of vesicles (Dh), estimated from the diffusivity measured by quasielastic light scattering, ranged from 230 to 3000 Å. The electrophoretic mobility (Um) was measured by free-flow electrophoresis. The zeta potential (ζ) and the degree of counterion dissociation (α) of the vesicles were calculated from Um and conductivity data, α decreased with increasing Dh of the vesicles, probably due to the decreasing headgroup area and the increasing counterion association needed to relax the surface electrostatic potential. The electrophoretic mobility was also calculated (Uc) according to an impenetrable, nonconducting sphere model with a spherically symmetric charge distribution approximation. Within the limits of the experimental error(s) of the (different) methods employed and the assumptions made in the calculations, the fact that the Um/Uc ratio ranged from 1.3 to 7.5 was considered to be a good agreement between the calculated and the experimental values. © 1990 American Chemical Society.

Morphology of the ventral lobe of the prostate and seminal vesicles in an ethanol-drinking strain of rats (UChA and UChB)

Chronic alcoholism alters reproduction and therefore may be responsible for alterations of prostate and seminal vesicles, which are the subject of this analysis in UCh ethanol-drinking rats. The prostate and seminal vesicles of 20 animals were submitted to macroscopic, light microscopy, electron microscopy and morphometric analysis. The UCh rats showed atrophy of the epithelium and reduction of the weight of the prostate and seminal vesicle, liver hypertrophy and fat infiltration and alterations of the hypothalamus-pituitary axis. Ethanol induces changes in the weight and in the epithelium of prostate and seminal vesicles and hypothalamus-pituitary axis of UCh rats.

Effect of the aspartic acid D2 on the affinity of Polybia-MP1 to anionic lipid vesicles

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

On the distinct molecular architectures of dipping- and spray-LbL films containing lipid vesicles

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Reversibility of Thermal Transitions in Dilute Dioctadecyl-Dimethyl-Ammonium Bromide Vesicles

Dioctadecyl-dimethyl-ammonium bromide (DODAB) vesicles can be characterized by their differential scanning calorimetry (DSC) thermograms comprised of two endotherms at T (s) a parts per thousand 36 A degrees C and T (m) a parts per thousand 45 A degrees C in the heating, ascribed respectively to the subgel-to-gel and gel-to-liquid crystalline transitions, and two exotherms at T'(m) a parts per thousand 40 A degrees C and T'(s) a parts per thousand 16 A degrees C in the cooling, ascribed respectively to the liquid crystalline-to-gel and gel-to-subgel transitions. It has been reported but not proved that the T (m)-transitions, the T'(m)-transitions, the T (s)-transitions, and the T'(s)-transitions are reverse to each other, displaying hystheresis Delta T (m) a parts per thousand 5 A degrees C and Delta T (s) a parts per thousand 20-25 A degrees C, respectively. By investigating the effects of the initial scanning temperature (T (i)) on the transition enthalpies (Delta H (m), Delta H (s), Delta H'(m) and Delta H'(s)), we have seen that these transitions are the reverse to each other and display different kinetics.