Sophie Bourcier

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

A 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.

FeIII‐Hydroperoxo and Peroxo Complexes with Aminopyridyl Ligands and the Resonance Raman Spectroscopic Identification of the Fe−O and O−O Stretching Modes

Nonheme Fe(III)-hydroperoxo and Fe(III)-peroxo complexes with aminopyridyl-type ligands have been prepared and characterized by UV/Vis, EPR, mass and Resonance Raman (RR) spectroscopy. The Fe(III)(OOH) species are low-spin and exhibit a deep purple color due to the ligand-to-metal charge transfer (LMCT) hand centered at ca. 550 nm. The RR spectra of the Fe(III)(OOH) complexes display two bands at ca. 620 and 800 cm-1 that are assigned to the respective Fe-O and O-O stretching modes on the basis of the characteristic H/D and 16O/18O frequency shifts. Upon deprotonation, Fe(III)(O2) species are obtained which possess a high-spin configuration of nearly axial symmetry and a LMCT transition in the near infrared (ca. 750 nm). The frequencies of the Fe-O and O-O stretching modes at ca. 465 and 820 cm-1, as well as their respective 16O/18O shifts of -16 and -45 cm-1, indicate an ?2 coordination geometry for the Fe(III)(O2) complex.

Reactivity of an Aminopyridine [LMnII]2+ Complex with H2O2. Detection of Intermediates at Low Temperature

In the present work we report the reactivity of [LMnII]2+ toward addition of hydrogen peroxide (H2O2) in acetonitrile solution, where L is a pentadentate polypyridine ligand. Formation of peroxo complexes is evidenced by low-temperature UV-visible spectroscopy, ESI-mass spectrometry, and EPR spectroscopy using parallel as well as perpendicular mode detection. The influence of the medium (basicity, water content) on the formation of various species is investigated. In basic nonanhydrous medium the fate of the reaction mixture solution is the formation of the di-mu-oxo mixed-valent Mn(III)Mn(IV) dinuclear complex. In acidic medium the building of the oxo bridges is avoided and the reaction mixture evolves toward oxidation of the ligand L. This reaction route offers new opportunities for the study of oxidation reactivity of Mn (hydro)peroxo complexes.

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

Abstract The 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.

Biomimetic Catalysis of Catechol Cleavage by O2 in Organic Solvents − Role of Accessibility of O2 to FeIII in 2,11‐Diaza[3,3](2,6)pyridinophane‐Type Catalysts

Three new complexes, [Fe(LN4H2)Cl2]+, [Fe(LN4H2)(Cat)]+, and [Fe(LN4H2)(DBC)]+, were synthesized by using the tetradentate macrocyclic ligand LN4H2 (where LN4H2, Cat, and DBC stand for 2,11-diaza[3,3](2,6) pyridinophane, catecholate, and 3,5-di-tert-butylcatecholate, respectively). The structure of [Fe(LN4H2)Cl2]+ was determined by X-ray diffraction. It crystallizes in the monoclinic space group C2/c with a = 9.613(1), b = 11.589(1), c = 14.063(2) A, β=110.20(2)°, V = 1541.9(3) A3, and Z = 4. These complexes were found to catalyze the oxidation of catechol groups using O2. This was performed in various organic solvents at 20 °C. The reaction rates were measured for the stoichiometric complexes [Fe(LN4H2)(Cat)]+ and [Fe(LN4H2)(DBC)]+. It was found that despite the relatively high energy of the ligand-to-metal charge transfer O(DBC or Cat)FeIII, their activity was comparable to that of the fast TPA systems [TPA indicates tris(2-pyridylmethyl)amine]. The oxidation products of DBCH2 have been studied. It has then been shown that the LN4H2 systems catalyse by means of both intra- and extradiol cleavage of catechol groups. The existence of multiple reactive pathways can account for the fast reactivity observed.

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

The 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.

Study of the chemical derivatization of zearalenone and its metabolites for gas chromatography-mass spectrometry analysis of environmental samples.

This study compares different silylation procedures of zearalenone and its metabolites: alpha-zearalenol, beta-zearalenol, zearalanone, alpha-zearalanol and beta-zearalanol for gas chromatography-mass spectrometry (GC-MS) analysis. Four silylating agents among the most frequently used to derivatize polar organic compounds were tested: N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA), N-methyl-N-trimethylsilyltrifluoroacetamide (MSTFA), N,N-diethyltrimethylsilylamine (TMSDEA) and a commercial mixture of N,O-bis(trimethylsilyl)acetamide, trimethylchlorosilane and N-trimethylsilyimidazole. Previous studies showed that the addition of polar and/or basic solvents can significantly improve the yield of a reaction of derivatization. In this work, four solvents were tested: pyridine, dimethylformamide, acetonitrile and acetone. The influence of each solvent was studied as a function of the silylating agent/solvent ratio. The influences of the temperature and of the reaction time on the reaction yields were also evaluated. A GC-MS quantitation method associating methanol chemical ionization and selected ion storage with three ions was developed and successfully tested on a reconstituted sediment spiked in zearalenone and its metabolites.

Application of the kinetic method to bifunctional bases: ESI tandem quadrupole experiments

Abstract The applicability of the kinetic method to the determination of the basicity of bidentate molecules has been assessed by considering several molecules M previously studied by equilibrium method (M=acetone (1), 1,3-propanediol (2), glycerol (3), 1,4-butanediol (4), 1,3-propanolamine (5), 1,4-butanolamine (6), 1,3-propanediamine (7) and 1,4-butanediamine (8)). Protonated adducts [MHBi]+ (where Bi is a reference base) were produced by electrospray ionisation and analysed by tandem quadrupole mass spectrometry. Application of the classical correlation of the natural logarithm of the ratio of peak intensities, ln([MH]+/[BiH]+), with either the proton affinities (PA) or the gas phase basicities (GB) of the reference bases Bi to deduce PA(M) or GB(M) has been examined. It is confirmed that only the use of several experiments at different collision energies (“extended” or “isothermal point” methods) may lead to meaningful results. Good agreement is observed between the PA(M) values tabulated or obtained from the isothermal point for molecule M = 1 and 5–8. However, the present PA values appear to be different from that obtained by equilibrium method in the case of diols 2–4. It is generally observed that the measured “apparent” protonation entropies of all the bifunctional molecules examined are significantly less than that obtained by equilibrium methods.

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

Our 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 NH3 at very low collision energy. The fragmentations of [MH – NH3]+ occur at high collision energy and are quite different for DHBAH+ and HMBAH+: formation of [MH – NH3 – H2O – CO]+ for the former; formation of the radical cation [MH – NH3 – CH3]+• 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 H2O and CO involve first the rearrangement in two steps of benzylic ions formed by loss of NH3 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 – NH3 – H2O]+. The determining steps associated with the losses of H2O and with H2O + 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 – NH3 – CH3]+•. The homolytic cleavage of CH3–O requires less energy than does the rearrangement.

Identification and ecotoxicity of degradation products of chloroacetamide herbicides from UV-treatment of water

The widespread occurrence of chlorinated herbicides and their degradation products in the aquatic environment raises health and environmental concerns. As a consequence pesticides, and to a lesser degree their degradation products, are monitored by authorities both in surface waters and drinking waters. In this study the formation of degradation products from ultraviolet (UV) treatment of the three chloroacetamide herbicides acetochlor, alachlor and metolachlor and their biological effects were investigated. UV treatment is mainly used for disinfection in water and wastewater treatments. First, the chemical structures of the main UV-degradation products were identified using gas chromatography coupled with mass spectrometry and liquid chromatography-mass spectrometry. The main transformation reactions were dechlorination, mono- and multi-hydroxylation and cyclizations. The ecotoxicity of the mixed photoproducts formed by UV-treatment until 90% of the original pesticide was converted was compared to the toxicity of chloroacetamides using the green alga Pseudokirchneriella subcapitata, the crustacean Daphnia magna and the marine bacteria Vibrio fischeri as test organisms. UV-treatment of alachlor and metolachlor increased the toxicity compared to the parent compounds while an equal toxicity was found for photolysis products of acetochlor. This suggests that toxic photodegradation products are generated from chloroacetamides under UV-treatment. An important perspective of this finding is that the photolysis products are at least as toxic as the parent compounds.