Cetylpyridinium removal using phosphate-assisted electrocoagulation, electroreduction and adsorption on electrogenerated sorbents

International audienceCetylpyridinium (CP+) is a cationic surfactant that can be found in various effluents and known due its toxicity against aquatic organisms. The removal of this compound was investigated in water solutions by electrocoagulation, phosphate-assisted electrocoagulation and adsorption on electrogenerated adsorbents. Electrocoagulations were carried out with aluminum electrodes in CP+ synthetic solutions. After 2 h of electrolysis in 0.1 M NaCl solutions, CP+ was mainly removed by electroreduction at calculated rates of 0.024 and 0.0416 μmol/C corresponding to abatements of 28 and 24% for starting concentrations of CP+ at 0.5 mM and 1.0 mM, respectively. The voltammetric study on steel or graphite electrodes confirmed a possible electroreduction of CP+ which may explain its removal during electrolysis. The change of the cathode from aluminum to carbon or steel did not change notably the removal efficiency of electrolysis in 0.1 M NaCl solution. However, after 2 h of electrolysis in 0.1 M NaCl in the presence of 0.1 M phosphate buffer, CP+ was mainly removed by adsorption on electrogenerated aluminum phosphate with rates of 0.0694 and 0.138 μmol/C corresponding to abatements of 80% for 0.5 or 1 mM CP+ solutions. The key role of phosphate ions was proved by adsorption experiments. The electro-synthesized alumina adsorbed CP+ with a removal capacity of 10.2 mg/g. But on electro-synthesized and chemical-synthesized aluminum phosphate the removal capacities were 94.2 and 165.3 mg/g, respectivel

Melittin modifies bending elasticity in an unexpected way

International audienceUnderstanding the molecular mechanism of the interaction of amphipathic and antimicrobial peptides with membranes is of fundamental interest, especially because of the potential of amphipathic peptides as therapeutics. The most studied amphipathic peptides in this context are certainly melittin, magainin and alamethicin, of which melittin is the only one to exhibit a powerful hemolytic and therefore toxic action. Herein we study the effect of the antimicrobial but hemolytic peptide melittin on the bending elasticity of giant unilamellar vesicles (GUVs). The results are compared to the effects of non-hemolytic amphipathic peptides such as alamethicin. We found that monomeric melittin acts very differently on the membrane mechanical properties. Strikingly, the difference is the most pronounced for low peptide concentrations, relevant for the hemolytic action. This gives some insight into the subtle nature of this peptide-membrane interaction. Furthermore, the results show that bending elasticity measurements might be a sensitive way to distinguish between lytic and non-lytic antimicrobial peptides

Softening of POPC membranes by magainin

International audienc

Selective removal of dodecyl sulfate during electrolysis with aluminum electrodes

International audienceElectrolyses with aluminum electrodes were performed to control the removal of dodecyl sulfate (DS) from aqueous solutions. When electrolyses were conducted in 0.1 M HCl solution and in the presence of 6.9-13.8 mmol L−1 of DS the pH increased and electrogenerated Al3+ ions and DS anion led to the formation of a precipitate after an induction period. The abatement of DS anion was about 80% at a concentration of 13.8 mmol L−1, when the molar ratio DS/Al was near 3. For electrolyses carried out in 0.1 M NaCl solution, the pH increased from 5 to 9.4 and an alumina precipitate was formed. The removal of DS anion was less efficient than in acid solution. The abatement did not depend upon the DS concentration in the range 6.9-13.8 mmol L−1 and it slightly increased until 20% with the electrolysis time. These results were in agreement with a DS anion adsorption on electro-generated alumina which was investigated. The adsorption capacity was found at 0.865 mmol g−1 of alumina. This selective removal of DS anion, thanks to a pH control, was applied in the recycling of a deinking wastewater

Alamethicin influence on the membrane bending elasticity.

We investigate the bending elasticity of lipid membranes with the increase of the alamethicin concentrations in the membrane via analysis of the thermally induced shape fluctuations of quasi-spherical giant vesicles. Our experimental results prove the strong influence of alamethicin molecules on the bending elasticity of diphytanoyl phosphatidylcholine and dilauroyl phosphatidylcholine membranes even in the range of very low peptide concentrations (less than 10(-3) mol/mol in the membrane). The results presented in this work, testify to the peripheral orientation of alamethicin molecules at low peptide concentrations in the membrane for both types of lipid bilayers. An upper limit of the concentration of the peptide in the membrane is determined below which the system behaves as an ideal two-dimensional solution and the peptide molecules have a planar orientation in the membrane

Impact of membrane-anchored fluorescent probes on the mechanical properties of lipid bilayers

International audienceFluorescent probes are used in membrane biophysics studies to provide information about physical properties such as lipid packing, polarity and lipid diffusion or to visualize membrane domains. However, our understanding of the effects the dyes themselves may induce on the membrane structure and properties are sparse. As mechanical properties like bending elasticity were already shown to be highly sensitive to the addition of "impurities" into the membranes, we have investigated the impact of six different commonly used fluorescent membrane probes (LAURDAN, TR-DPPE, Rh-DPPE, DiIC18, Bodipy-PC and NBD-PC) on the bending elasticity of dye containing POPC GUVs as compared to single component POPC GUVs. Small changes in the membrane bending elasticity compared to single POPC bilayers are observed when 2 mol% of Rh-DPPE, Bodipy-PC or NBD-PC are added in POPC membranes. These binary membranes are showing non reproducible mechanical properties attributed to a photo-induced peroxidation processes that may be controlled by a reduction of the fluorescent dye concentration. For TR-DPPE, a measurable decrease of the bending elasticity is detected with reproducible bending elasticity measurements. This is a direct indication that this dye, when exposed to illumination by a microscope lamp and contrary to Rh-DPPE, does not induce chemical degradation. At last, LAURDAN and DiIC18 probes mixed with POPC do not significantly affect the bending elasticity of pure POPC bilayers, even at 2 mol%, suggesting these latter probes do not induce major perturbations on the structure of POPC bilayers

Lanthanide-based hexanuclear complexes usable as molecular precursor for new hybrid materials : state of the art.

WOSInternational audienceLanthanide containing octahedral hexanuclear complexes with general chemical formula [Ln6O(OH)8(NO3)6(H2O)x].2NO3.yH2O where Ln = Ce-Lu (except Pm) or Y, x = 0, 6, 12, 14 or 16 and y = 0, 2, 4 or 5 constitute a great family of polymorphic compounds. The synthesis and the crystal structures of all these compounds are overviewed. The hydration/dehydration processes that allow the structural transitions from one compound to another are described. The crystal structure of compounds with general chemical formula [Ln6O(OH)8(NO3)6(H2O)6].2NO3 where Ln = Ce-Lu (except Pm) or Y is described. It has been solved on the basis of a powder XRD diagram. The use of such hexanuclear complexes as molecular precursors for new materials is also discussed

Mechanics of POPC bilayers in presence of alkali salts

International audienceMembranes mechanical properties are affected by solvent properties, i.e. the salt content. In this study, we use POPC GUVs (Giant Unilamellar Vesicles) as model membranes and we measure the membrane mechanical moduli by flickering analysis and micropipette technique for a series of alkali salt solutions. Salt concentration effects and ion specificity are investigated in these measurements. Membrane mechanical moduli are shown to display a complex dependence on the salt solution composition