Electrocarboxylation of chloroacetonitrile mediated by electrogenerated cobalt(I) phenanthroline

The electrocarboxylation of chloroacetonitrilemediated by [Co(II)(phen)3]2+ has been investigated. Cyclic voltammetry studies of [Co(II)(phen)3]2+ have shown that [Co(I)(phen)3]+, an 18 electron complex, activates chloroacetonitrile by an oxidative addition through the loss of a phenanthroline ligand to give [RCo(III)(phen)2Cl]+. The unstable one-electron-reduced complex underwent Co–C bond cleavage. In carbon dioxide saturated solution, CO2 insertion proceeds after reduction of the alkylcobalt complex. A catalytic current is observed which corresponds to the electrocarboxylation of chloroacetonitrile into cyanoacetic acid. Electrolyses confirmed the process and gave faradic yield of 62% in cyanoacetic acid at potentials that are about 0.3 V less cathodic than the one required for Ni(salen)

Electrocarboxylation of chloroacetonitrile by a Cobalt(I) complex of terpyridine

The electrocarboxylation of chloroacetonitrile (NC–CH2–ClRCl) mediated by [CoIIL2]2+ (L = terpyridine) was investigated by cyclic voltammetry. Electrochemical studies under argon atmosphere showed that the monoelectronic reduction of [CoIIL2]2+ yielded a Cobalt(I) complex which after the loss of a terpyridine ligand reacted with chloroacetonitrile. The oxidative addition of chloroacetonitrile on [CoIL]+ gave an alkylCobalt(III) complex [R–CoIIIL]2+ which was reduced into an alkylCobalt(II) complex, highly unstable and decomposed into an alkyl anion and a Cobalt(II) complex. Under carbon dioxide atmosphere, Cobalt(I) complex was shown to be unreactive towards CO2 but CO2 insertion was observed in the alkylCobalt(III) complex [R–CoIIIL] 2+ giving probably a CO2 adduct [R–CoIIIL(CO2)]2+. This adduct presented a strong adsorption at the carbon electrode and was reduced at potential less cathodic than the one of alkylCobalt(III) complex. After reduction, the carboxylate RCO2− (NC–CH2–CO2−) was released and a catalytic bielectronic carboxylation of chloroacetonitrile took place. Controlled potential electrolyses confirmed the catalytic process and gave for cyanoacetic acid faradic yields up to 60% under low overpotential conditions

X-ray structures of dinuclear copper(I) and polynuclear copper(II) complexes with the 2,4-bis(cyanamido)cyclobutane-1,3-dione dianion

From the 2,4-bis(cyanamido)cyclobutane-1,3-dione dianion (2,4-NCNsq2−), two copper complexes [Cu2(PPh3)4(PhCN)2(μ-2,4-NCNsq)] · PhCN (1) and [Cu(dien)(μ-2,4-NCNsq) · H2O]n (2) have been synthesized and characterized by IR and electronic absorption spectroscopies. Their structures have been determined by X-ray crystallography. Complex 1 is a dinuclear copper(I) compound with a 2,4-NCNsq2− ligand bridging two copper atoms through the nitrile nitrogen atoms. Complex 2 appears as a 3D network constituted of copper(II) atoms bridged by 2,4-NCNsq2− dianions. This complex presents an unexpected coordination mode of the bis(cyanamido) ligands which are both coordinated via the nitrile functions and via the amido nitrogen atoms of the NCN groups

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

Characterization of oxidative stress in Leishmaniasis-infected or LPS-stimulated macrophages using electrochemical impedance spectroscopy

The physiological changes caused by external stimuli can be employed as parameters to study pathogen infection in cells and the effect of drugs. Among analytical methods, impedance is potentially useful to give insight into cellular behavior by studying morphological changes, alterations in the physiological state, production of charged or redox species without interfering with in vitro cellular metabolism and labeling. The present work describes the use of electrochemical impedances spectroscopy to simply monitor by modeling impedance plots (Nyquist diagram) in appropriate equivalent circuit, the changes affecting murine macrophage cell line (RAW 264.7) in response to parasite infection by Leishmania amazonensis or to lipopolysaccharide (LPS) treatment. These results demonstrate the ability of electrochemical impedance spectroscopy to discriminate between two opposite cell responses associated to two different stimuli, one caused by the internalization of a parasite, and the other by activation by a bacterium component. Indeed, the study has allowed the characterization, from an electrical point of view, of the extra-cellular NO radical produced endogenously and in great quantities by the inducible form of NO-synthase in the case of LPS-stimulatedmacrophages. This production was not observed in the case of Leishmania-infectedmacrophages for which to survive and multiply, the parasite itself possesses mechanisms which may interfere with NO production. In this latest case, only the intracellular production of ROS was observed. To confirm these interpretations confocal microscopy analysis using the ROS (reactive oxygen species) fluorescent probe 2′,7′-dichlorodihydrofluorescein diacetate and electron paramagnetic resonance experiments using Fe(DETC)2 as NO radical spin trap were carried out

Property Model Methodology: A First Assessment in the Avionics Domain

International audienceThe aim of this paper is twofold. Firstly, it is intended to provide an overview of the goals, the concepts and the process of a new Model Based Systems Engineering methodology, called Property Model Methodology (PMM). The second aim is to provide a feedback on its application in the avionics domain. In this experiment, PMM has been used in order to develop a top level specification model regarding a textual specification of an avionics function, to validate the top level specification model, and according to PMM rules to develop (1) a design model of the function taking into account architectural constraints of an integrated avionics, (2) building block specification models and (3) building block design models. Building block specification models were validated regarding their encompassing system specification model and the selected system design model while the design models were integrated and verified, level by level up to the top level design model, regarding their specification model. This paper summarizes the lessons learnt during this process and some additional results related to safety issues. This paper, with others [1,2], proves the fundamental concepts of PMM and provides a starting point for further research on Model Based Systems Engineering of a wide range of engineered systems (discrete, hybrid, continuous and multi-physics systems), but also support additional systems engineering activities (e.g. safety-reliability activities)

Electrochemical impedance spectroscopy to study physiological changes affecting the red blood cell after invasion by malaria parasites

The malaria parasite, Plasmodium falciparum, invades human erythrocytes and induces dramatic changes in the host cell. The idea of this work was to use RBC modified electrode to perform electrochemical impedance spectroscopy (EIS) with the aim of monitoring physiological changes affecting the erythrocyte after invasion by the malaria parasite. Impedance cell-based devices are potentially useful to give insight into cellular behavior and to detect morphological changes. The modelling of impedance plots (Nyquist diagram) in equivalent circuit taking into account the presence of the cellular layer, allowed us pointing out specific events associated with the development of the parasite such as (i) strong changes in the host cell cytoplasm illustrated by changes in the film capacity, (ii) perturbation of the ionic composition of the host cell illustrated by changes in the film resistance, (iii) releasing of reducer (lactic acid or heme) and an enhanced oxygen consumption characterized by changes in the charge transfer resistance and in the Warburg coefficient characteristic of the redox species diffusion. These results show that the RBC-based device may help to analyze strategic events in the malaria parasite development constituting a new tool in antimalarial research

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

Electrochemical behavior of indolone-N-oxides: Relationship to structure and antiplasmodial activity

Indolone-N-oxides exert high parasiticidal activity at the nanomolar level in vitro against Plasmodiumfalciparum, the parasite responsible for malaria. The bioreductive character of these molecules was investigated using cyclic voltammetry and EPR spectroelectrochemistry to examine the relationship between electrochemical behavior and antimalarial activity and to understand theirmechanisms of action. For all the compounds (37 compounds) studied, the voltammograms recorded in acetonitrile showed a well-defined and reversible redox couple followed by a second complicated electron transfer. The first reduction (−0.88 VbE1/2b−0.50 V vs. SCE) was attributed to the reduction of the N-oxide function to form a radical nitroxide anion. The second reduction (−1.65 VbE1/2b−1.14 V vs. SCE) was assigned to the reduction of the ketone function. By coupling electrochemistry with EPR spectroscopy, the EPR spectra confirmed the formation of the nitroxide anion radical.Moreover, the experiments demonstrated that a slowprotonation occurs at the carbon of the nitrone function and not at the NO function. A relationship between electrochemical behavior and indolone-N-oxide structure can be established for compounds with R1=―OCH3, R2=H, and electron-withdrawing substituents on the phenyl group at R3. The results help in the design of new molecules with more potent in vivo antimalarial activity

High resolution, on-line identification of strains from the Mycobacterium tuberculosis complex based on tandem repeat typing

BACKGROUND: Currently available reference methods for the molecular epidemiology of the Mycobacterium tuberculosis complex either lack sensitivity or are still too tedious and slow for routine application. Recently, tandem repeat typing has emerged as a potential alternative. This report contributes to the development of tandem repeat typing for M. tuberculosis by summarising the existing data, developing additional markers, and setting up a freely accessible, fast, and easy to use, internet-based service for strain identification. RESULTS: A collection of 21 VNTRs incorporating 13 previously described loci and 8 newly evaluated markers was used to genotype 90 strains from the M. tuberculosis complex (M. tuberculosis (64 strains), M. bovis (9 strains including 4 BCG representatives), M. africanum (17 strains)). Eighty-four different genotypes are defined. Clustering analysis shows that the M. africanum strains fall into three main groups, one of which is closer to the M. tuberculosis strains, and an other one is closer to the M. bovis strains. The resulting data has been made freely accessible over the internet to allow direct strain identification queries. CONCLUSIONS: Tandem-repeat typing is a PCR-based assay which may prove to be a powerful complement to the existing epidemiological tools for the M. tuberculosis complex. The number of markers to type depends on the identification precision which is required, so that identification can be achieved quickly at low cost in terms of consumables, technical expertise and equipment