Interaction of solutions of uranyl formate or acetate with mycobactin S in anhydrous organic solvents leads to the formation of 11 complexes which can be isolated as dark orange, vitreous, non-hygroscopic solids. Aqueous extraction measurements with the232U-labelled complexes show that extensive dissociation occurs in acidic medium. On the other hand, the compounds are highly resistant to photolytic decomposition. Spectrophotometric characterization and structural considerations suggest that coordination geometry of the ionophore with UO
is practically identical in both derivatives, and may impose sterical requirements different from those of other metalmycobactin complexes.
Addition of solutions of mycobactin S in acetone or methanol/acetone mixtures to solutions of NpO
in the same solvent leads to the immediate reduction of neptunium/VI/ to neptunium/V/. Np/V/ interacts with the ionophore to form a yellow complex with a cation: ligand ratio of 21. The course of these reactions is followed by measurement of changes in characteristic optical absorption and by spectrophotometric titration within the range 700–1350 nm.
Measurements of Group IIA/IIIB cation adsorption by non-proliferative suspensions of Mycobacterium smegmatis in acidic medium show regular trends in percent adsorption and specific uptake of both ion types in the90Sr/90Y filiation for carrier concentrations in the range 50–2000 M. In comparative measurements with the47Ca/47Sc filiation, the corresponding adsorption of Sc3+ is consistently higher than that of Y3+, and both ions are preferentially adsorbed with respect to the divalent species Sr2+ and Ca2+. Ion separation efficiency in the calcium/scandium pair is more pronounced at lower concentrations and appears highest in the 100 M carrier region.
Authors:H. MacCordick, J.-C. Hubert, and J. Schleiffer
The absorption effect of 5% w/w non-proliferative cell suspensions of Mycobacterium smegmatis on labelled solutions of Eu3+ ions, both alone and in admixtures with Am3+, Co2+ and Cs+, was studied at pH 1.0 as a function of time and cationic concentration. For 10 M concentrations of Eu, Co and Cs, selective adsorption of the trivalent lanthanide and actinide ions was practically quantitative after 90 min; no significant adsorption was observed for cobalt and cesium ions. Column adsorption measurements with the mycobacterial biomass showed that desorption of the M3+ ions did not occur at less than 2M HCl and remained incomplete even at higher acidities.
Biosorption of Th4+ and UO
ions, both separately and in mixed equimolar ratio, was carried out using nitrate-buffered solutions of the cations at pH 1 in the presence of 5%w/w non-proliferative cell suspensions of Mycobacterium smegmatis. At equilibrium following a 3 h treatment, specific adsorption for 2 mM Th and U was, respectively, 102 and 115 mol g–1 dry biomass for individual solutions and 102 and 42 mol g–1 for the mixed 2/2 mM solution. Desorption studies of the cation-loaded biomass preparations in aqueous media and in soilbacterial suspensions within the pH range <1 to 11 showed that leaching of throium was generally less than 1% at pH 1–11 after 7 d, whereas uranium was leached to the extent of 2% at pH 1 and up to 10% under the same conditions in Th–U mixtures.
Authors:H. MacCordick, F. Taghva, J. Meyer, and D. Gelus
The reaction product of uranyl nitrate with whole-protein Bushmaster snake venom in nitrate buffer at pH 3.5 has been studied. The maximum uptake of uranium was 291 mol U·g–1 of venom. The infrared spectrum of the product showed an asymmetric O–U–O vibration at 921 cm–1 typical of complex formation with the uranyl ion. Stability measurements with the UO
-protein complex in neutral medium indicated moderate hydrolytic stability, with 14% dissociation after 16 hours at 0°C. Neutron irradiation and desorption studies with a235U-labelled complex showed that generated fission products such as lanthanides and barium were readily lixiviated at pH 7, whereas Ru and Zr were highly retained by the protein substrate.