Etudes structurales d'absorption de rayons X appliquées à des métalloprotéines à cuivre

GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

A combined spectroscopic and theoretical approach to investigate structural properties of Co(II)/Co(III) tris-cysteinato complexes in aqueous mediumw

International audiencePhysiological and toxicological effects of metallic ions depend on their speciation and on the structure of their associated bioligand complexes. In the field of chemical and/or nuclear toxicological studies, we are investigating cobalt complexes with biorelevant ligands such as amino acids or peptides. The aqueous reaction of cobalt dichloride with an excess of cysteine (Cys, C$_3$H$_5$NSO$_2$$^{2-}$) in a basic medium under an anaerobic atmosphere and subsequent oxidation by O$_2$ , afforded the mononuclear complexes Co(II):3Cys and Co(III):3Cys, respectively. A combination of X-ray absorption spectroscopy (XAS) measurements and Car-Parrinello molecular dynamics (CPMD) simulations allowed us to assess structural features of the already explored Co(III):3Cys complex. Inclusion of the temperature effects in the CPMD calculations gives an implicit access to disorder effects in the extended X-ray absorption fine structure (EXAFS) equation. The very good agreement between the measured and the simulated data showed the accuracy of these models provided by CPMD. The present investigation is completed by new UV-visible, X-ray absorption near edge structure (XANES) and electron paramagnetic resonance (EPR) data of Co(II):3Cys. These data are consistent with a Co(II) high-spin d$^7$ complex in a distorted octahedral geometry. This work contributes to the knowledge of topics such as metal-bioligand interaction which is of major interest in the field of bioinorganic chemistry

Speciation of ruthenium in TBP/TPH organic phases (structure and reactivity)

International audienceRuthenium is one of the major fission products and draws attention to it because it is partly extracted with uranium and plutonium during the reprocessing of the used nuclear fuel. The decontamination factors of the recoverable materials are impacted by this unwanted transfer from the nitric acid phase to the tributylphosphate (TBP) phase. During dissolution of used nuclear fuel, ruthenium forms trivalent nitrosyl complexes with nitrate, nitrite, hydroxo and aquo ligands. The admitted general formula is [RuNO(NO$_3$)x(NO$_2$)$_y$(OH)$_z$(H$_2$O)$_{5-x-y-z}$]$^{3-(x+y+z)}$ where x, y, z depend on the chemical conditions. Only the most nitrated complexes must be extracted with a quantitative yield

XAS examination of glutathione cobalt complexes in solution.

International audienceIn the present work, we have investigated the coordination modes of cobalt with glutathione (γ-l-glutamyl-l-cysteinyl-glycine, GSH). A systematic study of cobalt-GSH complexes at basic and neutral pH has been undertaken with a multi-spectroscopic approach combined with quantum chemistry calculations. XAS (x-ray absorption spectroscopy) has been performed at the cobalt K edge in order to shed light into the cation coordination sphere and formal oxidation states. XANES (x-ray absorption near edge structure) enabled to show that in basic and neutral media, cobalt oxidation state is equal to +III and +II respectively. EXAFS (extended x-ray absorption fine structure) provided indications on the donor atoms involved in the coordination with cobalt as well as the bond lengths. DFT (density functional theory)-based calculations and NMR experiments have been performed to assess the most stable structure of the cobalt-GSH complex in basic conditions

Speciation Change of Uranyl in Lithium Borate Glasses

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Inner to outer-sphere coordination of plutonium( iv ) with N,N-dialkyl amide: influence of nitric acid

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Oxidized derivatives of Octopus vulgaris and Carcinus aestuarii hemocyanins at pH 7.5 and related models by x-ray absorption spectroscopy.

The binuclear copper sites of the met and met-azido derivatives of Octopus vulgaris and Carcinus aestuarii hemocyanins at pH 7.5 were characterized by high-resolution x-ray absorption spectroscopy in the low energy region (XANES) and in the higher region (EXAFS). The accuracy of the analysis of the data was tested with two mononuclear and six binuclear copper(II) complexes of the poly(benzimidazole) ligand systems 2-BB, L-5,5 and L-6,6 (Casella et al., 1993, Inorg. Chem. 32:2056-2067; 1996, Inorg. Chem. 35:1101-1113). Their structural and reactivity properties are related to those of the protein's derivatives. The results obtained for those models with resolved x-ray structure (the 2-BB-aquo and azido mononuclear complexes, and the binuclear L-5,5 Cu(II)-bis(hydroxo) (Casella et al., unpublished)), extends the validity of our approach to the other poly(benzimidazole)-containing complexes and to the hemocyanin derivatives. Comparison between the protein's and the complexes' data, support a description of the met-derivatives as a five-coordinated O-bridged binuclear copper(II) center and favors, for both species, a bis(hydroxo) structure with a 3-A Cu-Cu distance. For O. vulgaris met-azido derivative a mu-1,3 bridging mode for the ligand appears the most likely. The structural situation of C. aestuarii met-azido-derivative is less clear: a mu-1,1 mode is favored, but a terminal mode cannot be excluded

Synchrotron radiation investigations of microstructural evolutions of ODS steels and Zr-based alloys irradiated in nuclear reactors

International audienceSynchrotron-based x-ray techniques are used to bring complementary information to local probes such as atom probe tomography and transmission electron microscopy. Two examples of nuclear materials used for the cladding of fuel assembly are given: oxide dispersion strengthened (ODS) alloys and M5 Zr-based alloys. In both cases, synchrotron radiation analyses bring original results concerning nanosized secondary phases: for M5, radiation-enhanced precipitation of β-Nb precipitates has been evidence and the crystallographic structure (lattice parameter and Nb content) is reported for the first time and for irradiated ODS, the dissolution of larger oxides is evidenced while a finer distribution of complex Y-Ti-O oxides still acts as obstacles for dislocations