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Etude de la spéciation des radionucléides avec les molécules d'intérêt biologique par approche spectrométrique

Abstract : Mechanisms of complexation and accumulation of the radionuclides at the cellular and molecular level are complex and poorly known because the studies on these subjects are scarce. Within the framework of this thesis, we studied the interactions of europium (analogue of trivalent actinides) and uranium (VI) (actinide) with biological molecules of interest : phytochelatins. Their role is to protect cells against intrusions from nonessential heavy metals (thus toxic). These proteins are likely to be implied in the mechanisms of sequestration of radionuclides in living organisms. However, their structure is complex, this is why, in order to better understand their reactivity, we extended our studies to lower entities which constitute them (amino acids and glutathione).
We determined solution speciation (stoichiometry, structure) as well as the complexing constants associated with the formation of these species. These studies were undertaken by Time Resolved Laser induced Fluorescence (TRLIF), ElectroSpray-Mass Spectrometry (ES-MS), Nuclear Magnetic Resonance (NMR), Fourier Transform Infra-Rouge spectroscopy (FTIR) and Extended X-ray Absorption Fine Structure Spectroscopy (EXAFS). The determination of the complexation constants enabled us to conclude that the complexing capacity of these molecules with respect to radionuclides was moderate (log10K1 < 3, pH 3 or 6), the formed species are mononuclear with only one ligand molecule (1:1). The interaction is performed via oxygenated (hard) groups. The direct complexation of europium with phytochelatins at acidic pH was studied jointly by TRLIF and ES-MS. The complexing capacity of these molecules is much higher than that of GSH from which they result. In addition to studies undertaken on synthetic solutions reproducing the "biological" conditions (pH close to neutrality, ionic strength 0.1 mol/L, etc), tests of cellular contamination were realized. The quantification of integrated europium showed that those are able to incorporate europium significantly.
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Contributor : Valérie Lourenço <>
Submitted on : Wednesday, November 7, 2007 - 12:36:13 PM
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Valérie Lourenço. Etude de la spéciation des radionucléides avec les molécules d'intérêt biologique par approche spectrométrique. Autre. Université Paris Sud - Paris XI, 2007. Français. ⟨tel-00179617v2⟩

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