De Novo Structure-Based Design of Bis-amidoxime Uranophiles

This paper presents a computational approach to the deliberate design of host architectures that recognize and bind specific guests. De novo molecule building software, HostDesigner, is interfaced with molecular mechanics software, PCModel, providing a tool for generating and screening millions of potential structures. The efficacy of this computer-aided design methodology is illustrated with a search for bis-amidoxime chelates that are structurally organized for complexation with the uranyl cation

Predicting Stability Constants for Uranyl Complexes Using Density Functional Theory

The ability to predict the equilibrium constants for the formation of 1:1 uranyl/ligand complexes (log <i>K</i>₁ values) provides the essential foundation for the rational design of ligands with enhanced uranyl affinity and selectivity. We use density functional theory (B3LYP) and the integral equation formalism polarizable continuum model (IEF-PCM) to compute aqueous stability constants for UO₂²⁺ complexes with 18 donor ligands. Theoretical calculations permit reasonably good estimates of relative binding strengths, while the absolute log <i>K</i>₁ values are significantly overestimated. Accurate predictions of the absolute log <i>K</i>₁ values (root-mean-square deviation from experiment <1.0 for log <i>K</i>₁ values ranging from 0 to 16.8) can be obtained by fitting the experimental data for two groups of mono- and divalent negative oxygen donor ligands. The utility of correlations is demonstrated for amidoxime and imide dioxime ligands, providing a useful means of screening for new ligands with strong chelating capability to uranyl

Liberalization Of Account Of Operations With Capital And Violation Of Financial Stability

У статті досліджено вплив процесів фінансової лібералізації на стан макроекономічної та фінансової стійкості, альтернативні позиції щодо використання інструментів контролю над капіталом з метою нейтралізації проциклічного впливу міжнародних потоків капіталу.In the article influence of processes of financial liberalization is investigational on the state of macroeconomic and financial firmness, alternative positions in relation to the use of control instruments above a capital with the aim of neutralization of проциклічного influence of international streams of capital

Ketene Reactions with Tertiary Amines

Tertiary amines react rapidly and reversibly with arylketenes in acetonitrile forming observable zwitterions, and these undergo amine catalyzed dealkylation forming <i>N,N</i>-disubstituted amides. Reactions of <i>N</i>-methyldialkylamines show a strong preference for methyl group loss by displacement, as predicted by computational studies. Loss of ethyl groups in reactions with triethylamine also occur by displacement, but preferential loss of isopropyl groups in the phenylketene reaction with diisopropylethylamine evidently involves elimination. Quinuclidine rapidly forms long-lived zwitterions with arylketenes, providing a model for catalysis by cinchona and related alkaloids in stereoselective additions to ketenes

How Amidoximate Binds the Uranyl Cation

This study identifies how the amidoximate anion, AO, interacts with the uranyl cation, UO₂²⁺. Density functional theory calculations have been used to evaluate possible binding motifs in a series of [UO₂(AO)_<i>x</i>(OH₂)_<i>y</i>]^2–<i>x</i> (<i>x</i> = 1–3) complexes. These motifs include monodentate binding to either the oxygen or the nitrogen atom of the oxime group, bidentate chelation involving the oxime oxygen atom and the amide nitrogen atom, and η² binding with the N–O bond. The theoretical results establish the η² motif to be the most stable form. This prediction is confirmed by single-crystal X-ray diffraction of UO₂²⁺ complexes with acetamidoxime and benzamidoxime anions

A Peptoid-Based Combinatorial and Computational Approach to Developing Ligands for Uranyl Sequestration from Seawater

The selective binding of uranyl for extraction from seawater by using polymer sorbents holds promise as a sustainable source of uranium for nuclear energy. A combinatorially synthesized peptoid library (N-substituted glycine oligomers) was screened for uranyl binding with the goal of identifying high-affinity ligands for use in polymer sorbents. Qualitative screening techniques using a dye, arsenazo III, identified three uranyl-binding sequences, all of which contained only carboxylic acids as the active binding groups. Fluorescence spectroscopy was used to determine a dissociation constant for one of the identified peptoids by monitoring the decrease in peptoid fluorescence upon uranyl binding. Density functional theory calculations were used to model the solution-state binding of these sequences to understand favored binding modes and geometries