Influence of freezing on physicochemical forms of natural and technogenic radionuclides in Chernozem soil

Sharp variations of different climatic parameters influence the transport, transfer, and deposition of contaminants in nature. Investigations of the impact of environmental temperature on the fractionation of radionuclides in soil are necessary for adequate assessment of their distribution and bioavailability in case of a nuclear accident. The impact of a sharp decrease of environmental temperature shortly after radioactive contamination on the physicochemical fractionation of natural and technogenic radionuclides in Chernozem soil and its influence on their potential migration ability and bioavailability in case of subsequent warming were evaluated. The soil was contaminated in a laboratory with ²⁴¹Am, ⁶⁰Co, ¹³⁷Cs, ²²⁸Ra, ²³⁴Th, and U and two temperature regimes were used for storage. Changes of the radionuclides association with various soil phases in the first weeks after contamination were studied. Physicochemical forms of ²⁴¹Am, ⁶⁰Co, ²²⁸Ra, ²³⁴Th, and U were determined using two sequential extraction procedures. The ion-exchangeable forms of ¹³⁷Cs were evaluated by single extraction with 1 M NH₄NO₃. The data showed that the freezing, following the radioisotope contamination of the soil, causes an increase of the amount of potentially mobile forms of radiocobalt, radiocesium, radium, and thorium and has an insignificant impact on the fractionation of americium and uranium.     

Solution combustion synthesis of YCoO3 and investigation of its catalytic properties by cyclic voltammetery

In this paper, the synthesis of YCoO₃ by solution combustion method and investigation of its catalytic activity using cyclic voltammetry is presented. The perovskite phase was obtained by thermal initializing of the solutions of the metal nitrates and the fuel (urea). The obtained solid precursor was further heated yielding the perovskite phase. The obtained perovskite compound has orthorhombic unit cell, within the space group Pnma, with unit cell parameters a = 5.4223 ?, b = 7.3657 ?, and c = 5.1385 ?. The catalytic activity of the prepared perovskite was investigated by cyclic voltammetry using YCoO₃-modified paraffin impregnated graphite electrode, in several electrolytes. It was found that the YCoO₃ perovskite has a distinct catalytic activity towards the oxidation of chloride anions in which Co³⁺ ions being the active centers. Also, this material enhances the oxidation of methanol in KOH.     

The different flexibility of c-Src and c-Abl kinases regulates the accessibility of a druggable inactive conformation

c-Src and c-Abl are two closely related protein kinases that constitute important anticancer targets. Despite their high sequence identity, they show different sensitivities to the anticancer drug imatinib, which binds specifically to a particular inactive conformation in which the Asp of the conserved DFG motif points outward (DFG-out). We have analyzed the DFG conformational transition of the two kinases using massive molecular dynamics simulations, free energy calculations, and isothermal titration calorimetry. On the basis of the reconstruction of the free energy surfaces for the DFG-in to DFG-out conformational changes of c-Src and c-Abl, we propose that the different flexibility of the two kinases results in a different stability of the DFG-out conformation and might be the main determinant of imatinib selectivity.