Volume 104, Issue 1

A spectroelectrochemical cell was fabricated for in-situ X-ray absorption spectroscopy (in-situ XAS). The XAS spectra of the uranium L III edge were monitored in electrolyte solutions during the electrochemical reduction. Tetravalent uranium, U 4+ , in 1 mol dm – 3 (M) hydrochloric acid (HCl) was electrochemically prepared from hexavalent uranium, UO 2 2+ , by constant current electrolysis, and the extended X-ray absorption fine structure (EXAFS) was analyzed. The concentration ratio of UO 2 2+ and U 4+ , which were formed via the disproportionation of pentavalent uranium, UO 2 + , during the electrolysis, were calculated based on the intensity of the signal for the two axial oxygen atoms in the linear UO 2 2+ unit, the U–O ax , bond that had a radial structural function. The apparent redox potential of the UO 2 2+ /U 4+ couple in 1 M HCl was determined based on the Nernst equation using the concentrations of UO 2 2+ and U 4+ . The electrode potential was shown to be close to the formal potential of the UO 2 2+ /UO 2 + couple as reported previously. This result indicates that the UO 2 + that was formed electrochemically at the electrode disproportionated to form UO 2 2+ and U 4+ in the bulk solution. The in-situ XAS of UO 2 2+ in 0.1 M nitric acid was also performed. The U 4+ that formed was partially re-oxidized to UO 2 2+ by the NO 3 – present in the solution. The formation of the UO 2 + carbonato complex was observed by in-situ XAS in a 1 M sodium carbonate solution during the bulk electrolysis. The edge jump of the X-ray absorption near edge structure (XANES) spectrum shifted from 17.164 to 17.163 keV, and the bond distances of U–O ax and U–O for CO 3 2 – increased from 1.78 to 1.88 Å and from 2.42 to 2.53 Å, respectively, because of the reduction of the UO 2 2+ to the UO 2 + carbonato complex.

Diglycolamic acid was anchored on a polyamine matrix and the product (PA-DGAH) was characterized by ion-exchange capacity measurement, TG-DTA and FT-IR spectroscopy. The extraction behavior of Am(III) and Eu(III) in PA-DGAH was studied from dilute nitric acid medium to examine the feasibility using the anchored adsorbent for their mutual separation. The effect of various parameters such as the duration of equilibration, concentration of europium, nitric acid and diethylenetriaminepentaacetic acid (DTPA) in aqueous phase on the distribution coefficient ( K d ) of Am(III) and Eu(III) was studied. The distribution coefficient decreased with increase in the concentration of nitric acid. Rapid extraction of metal ions in the initial stages of equilibration followed by the establishment of equilibrium occurred within 4 h. The data on the rate of uptake of Am(III) and Eu(III) were fitted into pseudo-first order and pseudo-second order rate equation. The extraction isotherm was fitted to Langmuir and Freundlich adsorption models and the apparent europium extraction capacity was determined. The mechanism of extraction was elucidated and the conditions needed for efficient separation of Am(III) from Eu(III) was optimized using DTPA. The study indicated the possibility of using PA-DGAH for the separation of Eu(III) from Am(III) with high separation factors.

The interaction between UO 2 2+ and ammonium-N,N-tetramethylenedithiocarbamate (ATMDTC) was investigated experimentally by means of UV-Vis spectrophotometry. Central Composite Design (CCD) was applied to optimisation of reaction with 54 runs in duplicate. This design type was also used to developed mathematical model equation. Analysis of Variance (ANOVA) indicates that the terms of the model are significant within the 95% confident interval. Remarkably initial solution pH, initial ATMDTC concentration, initial Cu 2+ concentration and temperature have effect on the reaction. Formation constant (log  K f ) was calculated as 2.917 by using Rank Annihilation Factor Analysis (RAFA).

The distribution coefficients ( K d ) are determined for the sorption of Th(IV), U(VI), Np(V), Pu(III/IV/VI), and Am(III) in the system natural Opalinus Clay (OPA) from Mont Terri, Switzerland, and synthetic OPA pore water at pH7.6 as a function of solid-to-liquid ratio and element concentration. A linear sorption behavior under the chosen experimental conditions was obtained. The K d values strongly depend on the oxidation state of the actinide. The K d values for the tri- and tetravalent actinides are in the range of 29–159 m 3 /kg. U and Np in the oxidation states six and five, respectively, are weakly sorbed on OPA with K d values of 0.04–0.05 m 3 /kg. The K d values for the redox-stable Am(III) and Th(IV) are in the same range as for Pu(III) and Pu(IV) which are redox sensitive. The K d value of Pu(VI) (13 ± 3 m 3 /kg) is about one order of magnitude lower than the K d values of Pu(III) and Pu(IV), but still more than two orders of magnitude higher compared to the values obtained for U(VI) and Np(V). This discrepancy is attributed to the partial reduction of Pu(VI) to Pu(IV) during sorption.

A chemical separation system was developed to separate group 4 and 5 elements using extraction from HCl/HF solution into methyl-isobutyl-ketone (MIBK). The system is proposed to be applied for a confident assignment of the spontaneous fissioning radionuclide produced as decay product of element 115 either as dubnium (Db, Z  = 105) or rutherfordium (Rf, Z  = 104). Moreover, extraction systems are proposed allowing the investigation of chemical properties of Db in comparison to the properties of its lighter homologs Nb and Ta.

The activity concentrations of isotopes of uranium, thorium and radium-226 in dominant species of plants ( Xantium strumarium , Phragmites communis , Artemisia nitrosa and Artemisia serotina ) growing on the territories contaminated by uranium industry of Kazakhstan (close to dam impoundment Tasotkel and the Lower Shu region) are presented. The obtained data showed the significant variations of activity concentrations of isotopes of uranium, thorium and radium-226 in above ground parts. The concentrations of most of the investigated radionuclides in the root system are higher than in the aboveground parts; it can be explained by root barrier. It was found that the highest root barrier has Xantium strumarium , especially for uranium isotopes. The concentration ratios of radionuclides were calculated, and as the result it was found that the highest accumulation ability in the investigated region has Artemisia serotina .

KRAS is very commonly mutated resulting in a constitutively activated protein, which is independent of epidermal growth factor receptor (EGFR) ligand binding and resistant to anti-EGFR therapy. Although KRAS is frequently studied, there is still no uniform standard for detecting of KRAS mutations. In this report, a new scintillation proximity assay-based approach is described that determines the relative affinities of wild-type and mutated KRAS to the anti-KRAS antibody. We performed in vitro experiments using normal human colonic cells (CCD18Co), KRAS wild type (Caco-2) and KRAS mutant (HCT 116) cell lines to determine the relative affinities of wild type or mutated KRAS toward an anti-KRAS monoclonal antibody. The process consists of two primary steps: immunoprecipitation from cell lysate to enrich the KRAS protein and the scintillation proximity assay of the immunoprecipitant to determine the relative affinity against the antibody. A fixed concentration of cell lysates was purified by the immunoprecipitation method. The expressions of the KRAS protein in all cell lines was quantitatively confirmed by western blot analysis. For the scintillation proximity assay, the KRAS standard protein was radiolabeled with 125 I by a simple mixing process in the iodogen tube immediately at room temperature immediately before use. The obtained CPM (count per minute) values of were used to calculate the KRAS concentration using purified KRAS as the standard. The calculated relative affinities of 7 μg of Caco-2 and HCT 116 immunoprecipitants for the anti-KRAS antibody were 77 and 0%, respectively. The newly developed scintillation proximity assay-based strategy determines the relative affinities of wild-type or mutated KRAS towards the anti-KRAS monoclonal antibody. This determination can help distinguish mutated KRAS from the wild type protein. The new SPA based approach for detecting KRAS mutations is applicable to many other cancer-related mutations.