6 research outputs found
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><sub>1</sub> 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 UO<sub>2</sub><sup>2+</sup> complexes
with 18 donor ligands. Theoretical calculations permit reasonably
good estimates of relative binding strengths, while the absolute log <i>K</i><sub>1</sub> values are significantly overestimated. Accurate
predictions of the absolute log <i>K</i><sub>1</sub> values
(root-mean-square deviation from experiment <1.0 for log <i>K</i><sub>1</sub> 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, UO<sub>2</sub><sup>2+</sup>. Density functional
theory calculations have been used to evaluate possible binding motifs
in a series of [UO<sub>2</sub>(AO)<sub><i>x</i></sub>(OH<sub>2</sub>)<sub><i>y</i></sub>]<sup>2–<i>x</i></sup> (<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 η<sup>2</sup> binding
with the N–O bond. The theoretical results establish the η<sup>2</sup> motif to be the most stable form. This prediction is confirmed
by single-crystal X-ray diffraction of UO<sub>2</sub><sup>2+</sup> 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