Bioanalytical characterisation of multiple endocrine- and dioxin-like activities in sediments from reference and impacted small rivers.

International audienceA comprehensive evaluation of organic contamination was performed in sediments sampled in two reference and three impacted small streams where endocrine disruptive (ED) effects in fish have been evidenced. The approach combined quantitative chemical analyses of more than 50 ED chemicals (EDCs) and a battery of in vitro bioassays allowing the quantification of receptor-mediated activities, namely estrogen (ER), androgen (AR), dioxin (AhR) and pregnane X (PXR) receptors. At the most impacted sites, chemical analyses showed the presence of natural estrogens, organochlorine pesticides, parabens, polycyclic aromatic hydrocarbons (16 PAHs), bisphenol A and alkylphenols, while synthetic steroids, myco-estrogens and phyto-estrogens were not detected. Determination of toxic-equivalent amounts showed that 28-96% of estrogenic activities in bioassays (0.2-6.3 ng/g 17beta-estradiol equivalents) were explained by 17beta-estradiol and estrone. PAHs were major contributors (20-60%) to the total dioxin-like activities. Interestingly, high PXR and (anti)AR activities were detected; however, the targeted analysed compounds could not explain the measured biological activities. This study highlighted the presence of multiple organic EDCs in French river sediments subjected to mixed diffuse pollution, and argues for the need to further identify AR and PXR active compounds in the aquatic environment

Development of conductive protonic materials with an architecture interpenetrating polymer networks from microemulsions

La «chimie verte » comprend le développement de procédés de synthèse respectueux de l'environnement, en réduisant notamment l'usage de solvants organiques. Dans ce but, nous avons montré qu'il était possible de synthétiser, à partir de microémulsions, des matériaux conducteurs protoniques, de structure prédéfinie, sans l'usage d'un autre solvant que l'eau.La première partie de cette étude a permis de démontrer la faisabilité de ce procédé. Le système ternaire choisi est composé d'une solution aqueuse d'acide 2-acrylamido-2-méthylpropane sulfonique (AMPS), de méthacrylate d'hexyle (HMA) comme phase hydrophobe et du tensioactif, le Brij® 35. Les structures des microémulsions ont été identifiées, selon leur composition, à partir de mesures de conductivité, de viscosité et d'imagerie par microscopies optique et confocale. Ces structures peuvent être inverse, lamellaire, bicontinue et directe. La polymérisation/réticulation par voie radicalaire des monomères présents dans les différentes phases conduit à des matériaux présentant ces mêmes structures. Les polymères étant réticulés, ces matériaux sont des réseaux interpénétrés de polymères (RIP).La seconde partie de cette étude a été consacrée à l'optimisation de la formulation des microémulsions pour obtenir des matériaux aux propriétés souhaitées. Ainsi, la fraction soluble et le taux de gonflement dans l'eau ont été considérablement réduits, tout en conservant une conductivité protonique de l'ordre de 10-3 S.cm-1. Les meilleurs résultats ont été obtenus en synthétisant un « double RIP », c'est-à-dire un RIP dans chacune des phases, matériau tout à fait original à ce jour."Green chemistry" includes the development of synthetic methods respectful of the environment, including reducing the use of organic solvents. For this purpose, we have shown that it is possible to synthesize, from microemulsions, proton conductive materials, predefined structure, without the use of a solvent other than water. The first part of this study demonstrates the feasibility of this method. The ternary system is selected from an aqueous solution consisting of 2-acrylamido-2-methylpropane sulphonic acid (AMPS), hexyl methacrylate (HMA) as hydrophobic phase and the surfactant, Brij® 35. The structures of microemulsions have been identified, depending on their composition from measurements of conductivity, viscosity and imaging optical and confocal microscopies. These structures can be inverse, lamellar, bicontinuous and direct. The polymerization/crosslinking of the monomers by free radical present in the various phases leads to materials having the same structures. Being crosslinked polymers, these materials are interpenetrating polymers networks (IPN). The second part of this study has been devoted to the optimization of the formulation of microemulsions to obtain materials with desired properties. Thus, the soluble fraction and the degree of swelling in water were significantly reduced, while maintaining proton conductivity of the order of 10-3 S.cm-1. The best results were obtained by synthesizing a "double IPN", that is to say, an IPN in each phase, entirely original material

Fragmentation mechanisms of protonated benzylamines. Electrospray ionisation-tandem mass spectrometry study and ab initio molecular orbital calculations.

International audienceOur research into neurotransmitters in a biological fluid presented an opportunity to investigate the fragmentations under low collision energy characterising benzyl-amines protonated under electrospray ionisation (ESI) conditions in a triple quadrupole mass spectrometer. In this work we present the breakdown graphs of protonated 3,4-dihydroxybenzylamine, DHBAH(+), and 3-methoxy, 4-hydroxybenzylamine, HMBAH(+), at various source temperatures and various pressures in the collision cell, the collision energy varying from 0 to 46 eV in the laboratory frame. Both parent ions eliminate first NH(3) at very low collision energy. The fragmentations of [MH - NH(3)](+) occur at high collision energy and are quite different for DHBAH(+) and HMBAH(+): formation of [MH - NH(3) - H(2)O - CO](+) for the former; formation of the radical cation [MH - NH(3) - CH(3)](+.) for the latter. These fragmentations are interpreted by means of ab initio calculations up to the B3LYP/6-311+G(2d,2p) level of theory. The successive losses of H(2)O and CO involve first the rearrangement in two steps of benzylic ions formed by loss of NH(3) into tropylium ions. The transition states associated with this rearrangement are very high in energy (about 400 kJ mol(-1) above MH(+)) explaining (i). the absence of an ion corresponding to [DHBAH - NH(3) - H(2)O](+). The determining steps associated with the losses of H(2)O and with H(2)O + CO are located lower in energy than the transition states associated with the isomerisation of benzylic ions into tropylium ions; explaining (ii). the formation of the radical cation [MH - NH(3) - CH(3)](+.). The homolytic cleavage of CH(3)-O requires less energy than does the rearrangement

B3LYP DFT molecular orbital approach, an efficient method to evaluate the thermochemical properties of MALDI matrices

International audienceThe thermochemical properties of seven UV-MALDI matrices and two IR-MALDI matrices were evaluated by means of ab initio molecular orbital calculations using the B3LYP functional density approach with 6-31+G(d,p) and 6-311+G(2d,2p) basis sets. These thermochemical properties include ionization energy, proton and electron affinities of neutral molecules and proton affinity of deprotonated molecules. The choosen UV-MALDI matrices are: 2,5-dihydroxybenzoic acid (2,5DHB), nicotinic acid (NA) and 2-aminonicotinic acid (2ANA), picolinic acid (PA) and 3-hydroxypicolinic acid (3HPA), 2-aminobenzoic acid (2ABA) and 4-nitroaniline (4NiAn) while the studied IR-MALDI matrices are urea (U) and glycerol (G). The proton affinities of neutral and deprotonated molecules are in very good agreement with the available experimental values (the differences between experimental and calculated values are smaller than the precision on the experimental measurements); the calculated ionization energies are close to the experimental values of adiabatic electronic transitions; the calculated electron affinities are new and cannot be compared with corresponding experimental values since they are not available. (C) 2002 Elsevier Science B.V. All rights reserved

Decarboxylation of carnitine and alpha-cyano-4-hydroxycinnamic acid under particle bombardment

International audienceProtonated carnitine and alpha -cyano-4-hydroxycinnamic acid were formed by laser photon irradiation, by MeV-ion bombardment and by electrospray. The spontaneous fragmentations of protonated molecules formed upon particle bombardment are compared with the decompositions induced by low- and high-energy collisions of molecules protonated by electrospray, The determination of fragmentation mechanisms was achieved using labelled compounds and by means of ab initio calculations. The most prominent fragmentation of protonated molecules formed under particle bombardment is an unexpected loss of carbon dioxide. More classical processes dominate the decomposition induced by collisions of electrosprayed species: loss of trimethylamine and 4-hydroxybutyrolactone from protonated carnitine, loss of water from protonated cinnamic acid but no loss of CO2. Decarboxylation occurring before or concomitant with protonation is proposed to interpret these results

Discovery of a series of portimine-A fatty acid esters in mussels

International audienceVulcanodinium rugosum is a benthic dinoflagellate known for producing pinnatoxins, pteriatoxins, portimines and kabirimine. In this study, we aimed to identify unknown analogs of these emerging toxins in mussels collected in the Ingril lagoon, France. First, untargeted data acquisitions were conducted by means of liquid chromatography coupled to hybrid quadrupole-orbitrap mass spectrometry. Data processing involved a molecular networking approach, and a workflow dedicated to the identification of biotransformed metabolites. Additionally, targeted analyses by liquid chromatography coupled to triple quadrupole mass spectrometry were also implemented to further investigate and confirm the identification of new compounds. For the first time, a series of 13-O-acyl esters of portimine-A (n = 13) were identified, with fatty acid chains ranging between C12:0 and C22:6. The profile was dominated by the palmitic acid conjugation. This discovery was supported by fractionation experiments combined with the implementation of a hydrolysis reaction, providing further evidence of the metabolite identities. Furthermore, several analogs were semi-synthesized, definitively confirming the discovery of these metabolization products. A new analog of pinnatoxin, with a molecular formula of C42H65NO9 , was also identified across the year 2018, with the highest concentration observed in August (4.5 μg/kg). The MS/MS data collected for this compound exhibited strong structural similarities with PnTX-A and PnTX-G, likely indicating a substituent C2H5O2 in the side chain at C33. The discovery of these new analogs will contribute to deeper knowledge of the chemodiversity of toxins produced by V. rugosum or resulting from shellfish metabolism, thereby improving our ability to characterize the risks associated with these emerging toxins

Fragmentation mechanisms of glycine-Cu+ in the gas phase. An experimental and theoretical study.

International audienceElectrosprayed copper complexes of glycine (GlyCu-) were formed from a glycine/CuX2 (X = Cl, CH3CO2) mixture, in methanol. The collision-induced fragmentation of the most abundant isotopic form Gly63Cu+ was studied as a function of collision energy. Four fragment ions are observed: 63CuNHCH2+, 63Cu+, CH2NH2+, plus a minor loss of H2O. The potential energy surface for formation of these fragment ions has been investigated at the B3LYP/6-311+G(2d,2p)//B3LYP/6-31G* level. Several types of mechanisms were considered, involving either metal insertion into covalent bonds (C-C, C-O, and C-N) or dissociative attachment whereby the metal ion catalyzes the fragmentation by its distant electronic influence. Mechanisms starting with copper insertion into the C-C bond account for the most favorable pathways for the formations of CuNHCH2+ and CH2NH 2+. Dissociative attachment cannot be excluded to participate to the formation of CuNHCH2+ and is the only way to explain H2O loss. Finally, calculations on the possible mechanisms for NH3 loss (not observed experimentally) indicate that the observed ions are the result of a competition between several fragmentation modes with relatively similar energetic requirements

Gas-phase basicity and acidity of tryptophan

International audienceExtensive exploration of the conformational space of neutral, protonated and deprotonated tryptophan has been conducted at various levels of theory including B3LYP, M06-2X, CBS-QB3 and G4MP2 methods. The two latter composite methods, CBS-QB3 and G4MP2, and the M06-2X functional provide very close results in term of relative H degrees(298) and G degrees(298) values between conformers. By contrast, B3LYP functional leads to less satisfying results. Theoretical protonation and deprotonation thermochemistry has been calculated using either the most stable conformers or an equilibrium population of conformers at 298 K. Gas-phase protonation thermochemistry of tryptophan has been experimentally determined by the extended kinetic method using ESI-TQ tandem mass spectrometry. Proton affinity and protonation entropy deduced from these experiments, PA(Trp) = 945.6 +/- 2.0(4.3) kJ mol(-1) and Delta S-p degrees(Trp) = - 16 +/- 2(5) J mol(-1) K-1 (uncertainties are standard deviation and, into parentheses, 95% confidence limit). These figures lead to a gas-phase basicity value of GB(Trp) = 908.4 +/- 2.1(4.6) kJ mol(-1). These experimental data are perfectly reproduced by theoretical calculations performed at the G4MP2 level. Computational results provide also insights on possible re-interpretation of (i) IRMPD spectrum of deprotonated tryptophan, and (ii) mechanism of the NH3 loss from protonated tryptophan. (c) 2012 Elsevier B.V. All rights reserved

Ionization of 2,5-dihydroxybenzoic acid (DHB) matrix-assisted laser desorption ionization experiments and theoretical study

International audienceThe 2,5-dihydroxybenzoic acid (DHB), well known as one of the most efficient matrix-assisted laser desorption ionization (MALDI) matrices, was photoionized at different irradiances of a UV laser. Molecular orbital calculations were performed with a Becke-style 3 parameter using the Lee-Yang-Parr correlation functional density approach to estimate the thermochemical properties of DHB and showed a very good agreement with available experimental data. We report a first estimation of the electron affinity of DHB (54 kJ/mol). In a second step, the calculation method was used to evaluate the thermochemical reliability of several ionization models postulated from MALDI experiments. Among those proposed, we report the reactions, which are thermodynamically the most probable in the solid state and in the gas phase. We evaluated the energy involved in the formation of DHB*+ and DHB*- molecular ions, DHBH+ and [DHB-H]- pseudomolecular ions. The phenomenon of reduction of molecular ions was also theoretically studied as well as the role of the DHBH* radical species. Our results on the reactivity of DHBH* radical species show evidence of their very probable implication in molecular ion formation and of the great role played by the hydroxyl substituants in the particular efficiency of DHB as a MALDI matrix. We propose a simple thermochemical diagram showing evidence that MALDI is a very energy demanding process and that differences in efficiency between matrices should be related to their chemical structures rather than to their physical properties. © 2001 Elsevier Science B.V