Unexpected effect of copper ions on electrochemical impedance behaviour of self-assembled alkylaminethiol monolayer

Effect of copper ions on the electrochemical behaviour of an alkylaminethiol monolayer has been studied by electrochemical impedance spectrosocpy. RAMAN experiment shows the effective adsorption of receptor onto the gold surfaces. The study of Nyquist plot shows that the gold/monolayer/electrolyte interface can be described by a serial combination of two R, CPE electrical circuits. In the presence of increasing amounts of copper, the Nyquist plots at low frequencies were modified showing an increase of the resistance of the second R, CPE electrical circuit. Moreover, this increase of resistance varies linearly with the amounts of copper ions added in solution from 10−8 mol·L−1 to 10−5 mol·L−1

First examples of neutral rhenium(V) complexes with a novel semi-rigid ligand containing a P,N,N,S donor atom set: Synthesis, characterisation and crystal structure

A new PN2S ligand, N-[2-(diphenylphosphino)phenyl]-2-[(S-trityl)acetylamino]ethanamide [Ph-P(Ph2)N2S(Trt)], was synthesised and reacted with ReV precursors. The reaction of both tritylated and detritylated ligands with ReOCl3(PPh3)2 gave the same expected neutral complex [ReO{Ph-P(Ph2)N2S}] (4) in good yield. An unexpected neutral and diamagnetic species, [ReN{Ph-P(Ph2)N2S(Trt)}] (5), has been isolated during the complexation of the tritylated ligand with ReNCl2(PPh3)2. The complexes, characterized by classical spectroscopic methods and X-ray analysis for 4, are the first examples of neutral semi-rigid-PN2S rhenium(V) complexes

Correlations between electrochemical behaviors and DNA photooxidative properties of non-steroïdal anti-inflammatory drugs and their photoproducts

Alkali-labile lesion to DNA photosensitized, via an electron transfer mechanism, by three non-steroidalanti-inflammatorydrugs (NSAIDs), ketoprofen, tiaprofenic acid and naproxen and their photoproducts during drug photolysis, was investigated using 32P-end labelled synthetic oligonucleotide. These photooxidative damages were correlated with the photophysical and electrochemicalproperties of drugs, appearing as the photosensitizer PS. Photophysical studies provided the excited state energies of the photosensitizer while their redox potentials and the relative stabilities of the PSradical dot− radical-anions were determined by cyclic voltammetry. On the basis of these data, we have calculated the Gibbs energy of photoinduced electron-transfer and evaluated the exergonicity of the oxidative photodamage. Moreover, kinetic control may be invoked according to the stabilities of PSradical dot−. Applied to this NSAIDs family, the photoxidative damages through electron transfer mechanism were analyzed and a good correlation with photoredox and photobiological properties was established

On the use of liquid metals as cathode in molten fluorides

The aim of this article is to investigate the behaviour of liquid metallic electrodes in pyroprocesses. Thus, studies of electrochemical properties of various liquid metallic electrodes (Bi, Sb, Sn, Pb, Ga) were performed in LiF–NaF (750 °C) and LiF–CaF2 (850 °C). Thanks to linear sweep voltammetry technics, electroactivity domains were determined as well as a reactivity (Sb > Bi > Pb > Sn > Ga > Mo) and a nobility scale (Ga < Sn < Pb < Sb < Bi < Mo), valid in both solvent: from these data, the extraction yield of an element can be evaluated. Then the preparation of alloyed cathodes for reductive extraction process, corresponding to a spontaneous reaction between a reducing agent contained in the liquid metal and the element to be removed from the molten salt, was examined. The in situ generation of liquid Bi–Li, Na or Ca (reducing agents) reactive electrodes was performed in LiF–NaF and LiF–CaF2 solvent by galvanostatic electrolyses. Elementary analyses showed that Li+ and Ca2+ were reduced on Bi at the same reaction rate in LiF–CaF2, whereas Na was preferentially inserted into Bi, compared to Li, in LiF–NaF. Linear relationships between the electrolysis potential and the logarithm of the global mole fraction of reducing agent were found. As a consequence, by fixing the potential at the end of the electrolysis, Bi reactive cathodes with a controlled quantity of reducing agent can be produced in galvanostatic condition

Correlation of cyclic voltammetry behaviour and photooxidative properties of indoprofen and its photoproducts

International audienceThe electrochemical behaviour of indoprofen (INP) and its photoproducts was investigated in acetonitrile containing tetrabutylammonium hexafluorophosphate at a Pt or Cv ultramicro-electrodes. These photosensitizers (PS) undergo irreversible oxidation yielding at first a radical cation PS+ and more or less reversible reductions through monoelectronic exchange involving a radical anion PS−. By varying the potential scan speed, the stabilities of the radical anions were evaluated. The determination of the redox potential and Rehm–Weller's equation shows the high exergonicity of the oxidative photodamagings whatever is the compound PS. The difference in DNA photosensitizing properties could rather be related to a kinetic control and then to the relative stabilities of the radical anions PS−. Cyclic voltammetry was found powerful in order to get a new insight in the photosensitizing properties of drugs

Seaweed Extracts: A Promising Source of Antibiofilm Agents with Distinct Mechanisms of Action against Pseudomonas aeruginosa

The organization of bacteria in biofilms is one of the adaptive resistance mechanisms providing increased protection against conventional treatments. Thus, the search for new antibiofilm agents for medical purposes, especially of natural origin, is currently the object of much attention. The objective of the study presented here was to explore the potential of extracts derived from three seaweeds: the green Ulva lactuca, the brown Stypocaulon scoparium, and the red Pterocladiella capillacea, in terms of their antibiofilm activity against P. aeruginosa. After preparation of extracts by successive maceration in various solvents, their antibiofilm activity was evaluated on biofilm formation and on mature biofilms. Their inhibition and eradication abilities were determined using two complementary methods: crystal violet staining and quantification of adherent bacteria. The effect of active extracts on biofilm morphology was also investigated by epifluorescence microscopy. Results revealed a promising antibiofilm activity of two extracts (cyclohexane and ethyl acetate) derived from the green alga by exhibiting a distinct mechanism of action, which was supported by microscopic analyses. The ethyl acetate extract was further explored for its interaction with tobramycin and colistin. Interestingly, this extract showed a promising synergistic effect with tobramycin. First analyses of the chemical composition of extracts by GC&ndash;MS allowed for the identification of several molecules. Their implication in the interesting antibiofilm activity is discussed. These findings suggest the ability of the green alga U. lactuca to offer a promising source of bioactive candidates that could have both a preventive and a curative effect in the treatment of biofilms

Аўтарскія праўкі Лукаша Калюгі: узаемасувязь моўнага і ідэйнага ўзроўняў

This work presents a solution for the photocatalytic degradation of the antibiotic ciprofloxacin (CIP) in water, without using P25 TiO2 powder and thus getting rid of expensive separation steps. It consists in using a TiO2 coating that is directly deposited on the optical window of a photocatalytic micro-reactor and 365 nm UV LEDs as radiation source. P25 TiO2 powder was also studied as reference. HPLC-MS was used to determine the transformation products and the pathways reactions. CIP was slowly degraded by the photolysis reaction at 365 nm: (75 % removal after 8 h of UV irradiation). However, no significant decrease of the total organic carbon (TOC) was noticed, thus showing the presence of transformation products not degraded by the action of UV-light alone. For a low catalyst amount (i.e 0.12 g of TiO2, whatever the form, powder or coating, per liter of contaminated water,), excellent CIP degradation by photocatalysis was observed. Complete CIP degradation after 1 h of irradiation was required using P25 and 8 h using TiO2 coating. Different preferential reaction pathways were identified for both TiO2 catalysts. The Langmuir-Hinshelwood model showed a very good representation of the kinetics, unlike its simplified pseudo-first order model. Photocatalysis experiments did not show a complete mineralization (60–70 % of TOC removal), but most of the aromatic transformation products were degraded. The last transformation products were identified as small aliphatic acids. There is therefore a real interest in using MOCVD coating of TiO2 for sustainable wastewater treatment to avoid expensive catalyst separation. A study with a spiked real effluent from a wastewater treatment plant was performed and a satisfactory degradation was obtained. Slower kinetics were found due to the presence of additional organic products and scavenger compounds such as HCO3-

Preliminary study of electrochemical conversion of glucose on novel modified nickel electrodes

International audienceGluconic acid and sorbitol are among the value-added chemicals that can be derived from biomass. Nowadays, these compounds are typically produced through biotechnological processes, but electrochemical methods offer numerous advantages over alternative approaches. While studies have extensively explored metals like copper, palladium, gold, and platinum, nickel has received relatively limited attention in this context. Notably, nickel exhibits electrochemical activity suitable for organic electrosynthesis. This work has been achieved with 5-h long-term electrolysis, glucose as a reactant, utilizing modified nickel electrodes in a KOH solution. While these studies achieved substantial conversion rates, the selectivities and Faraday efficiencies toward gluconic acid and sorbitol remained comparatively low. The long-term electrolysis of glucose using modified nickel electrodes resulted in the identification of various side products. These include formic acid, oxalic acid, glycolic acid, tartronic acid, glyceric acid, and arabinose

Two polygenic mouse models of major depressive disorders identify TMEM161B as a potential biomarker of disease in humans

International audienceTreatments are only partially effective in major depressive disorders (MDD) but no biomarker exists to predict symptom improvement in patients. Animal models are essential tools in the development of antidepressant medications, but while recent genetic studies have demonstrated the polygenic contribution to MDD, current models are limited to either mimic the effect of a single gene or environmental factor. We developed in the past a model of depressive-like behaviors in mice (H/Rouen), using selective breeding based on behavioral reaction after an acute mild stress in the tail suspension test. Here, we propose a new mouse model of depression (H-TST) generated from a more complex genetic background and based on the same selection process. We first demonstrated that H/Rouen and H-TST mice had similar phenotypes and were more sensitive to glutamate-related antidepressant medications than selective serotonin reuptake inhibitors. We then conducted an exome sequencing on the two mouse models and showed that they had damaging variants in 174 identical genes, which have also been associated with MDD in humans. Among these genes, we showed a higher expression level of Tmem161b in brain and blood of our two mouse models. Changes in TMEM161B expression level was also observed in blood of MDD patients when compared with controls, and after 8-week treatment with duloxetine, mainly in good responders to treatment. Altogether, our results introduce H/Rouen and H-TST as the two first polygenic animal models of MDD and demonstrate their ability to identify biomarkers of the disease and to develop rapid and effective antidepressant medications