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31.
Cristiane R. Winck Mariana P. Darbem Roberto S. Gomes Andrelson W. Rinaldi Nelson Luís C. Domingues 《Tetrahedron letters》2014
Hybrid materials have seized attention from scientific community mainly as heterogenic catalysts in organic reactions on a large scale succeeding in some organic compounds with high yields. One of the most important classes of hybrid materials used for this purpose involves the complexation of Zn and aminoacids. Herein, we introduced Zn[Pro]2 and Zn[Gly]2 in the synthesis of several β-enaminones via solvent free protocol and using an ultrasound device. 相似文献
32.
33.
David Adeyemi Janes Mokgadi James Darkwa Chimezie Anyakora Grace Ukpo Charlotta Turner Nelson Torto 《Chromatographia》2011,73(9-10):1015-1020
Electrospun polystyrene (PS) nanofibers (130–500 nm) incorporating a potassium salt of imidazole-1-carbodithioate were evaluated as potential sorbents for the pre-concentration of a model organochlorine pesticide; 1,1-dichloro-2,2bis-(4-chlorophenyl)ethylene (DDE). The efficiencies of DDE (0.25–1.0 μg L?1) adsorption by the nanofiber sorbent followed by desorption employing pressurized hot water extraction (PHWE) were investigated and monitored using gas chromatography with electron capture detection (GC-ECD). Parameters such as time, temperature and pressure of extraction, sample volume, DDE concentration and sorbent mass were optimized. The maximum adsorption of DDE (0.50 μg L?1) on electrospun PS and carbodithioate incorporated PS nanofibers was at 43.7 and 94.6%, respectively, in 20 min. Incorporation of carbodithiote doubled the adsorption efficiency of PS and achieved LOD of 0.000234 μg L?1 for DDE. The optimal DDE desorption on the PHWE system was 93.8% in 10 min. It would seem that the use of electrospun nanofibers as sorbent material with subsequent desorption by PHWE has great potential and thus warrants further investigations. This approach as it uses water as an extraction solvent for an organochlorine pesticide provides an opportunity to eliminate organic solvents, especially for procedures aimed at monitoring organic pollutants in the environment. 相似文献
34.
Nicole A.S. White Henry A. Ellis Peter N. Nelson Paul T. Maragh 《The Journal of chemical thermodynamics》2011,43(4):584-590
Thermotropic phase transition temperatures, enthalpies and entropies of phase changes and odd–even alternation, in a homologous series of anhydrous lithium n-alkanoates, LiCnH2n?1O2 (LiC8–19 inclusive), have been investigated by differential scanning calorimetry (d.s.c.), hot stage polarizing microscopy and solid state 13C NMR spectroscopy. The number of phases observed, between the room temperature microcrystalline solid and isotropic melt, shows a clear dependence on chain length. For LiC8–13, only one intermediate lamellar II crystalline phase is observed. For LiC14–19, a lamellar II and high temperature phase are evident. The high temperature phase is characterized by pre-melting and disordering of hydrocarbon chains as they change from nearly all-trans to one with increased gauche conformers. It is probably a solid rotator phase. Odd–even alternation in melting temperature, density and some thermodynamic data result from the relative distance between methyl groups, from opposite layers in a bi-layer. Molecular models indicate that the methyl groups in odd chains are more favourably orientated which lead to a more energetically favoured staggered conformer. As a consequence, the methyl groups, for odd chains, are in closer proximity than even chains. This subtle change in the molecular lattice could account for the presence of polymorphic structures on cooling from the melt. 相似文献
35.
Min Tian Sapanbir S. Thind Shuai Chen Nelson Matyasovzsky Aicheng Chen 《Electrochemistry communications》2011,13(11):1186-1189
In the present work, we report on a facile and effective approach to significantly enhance the photocatalytic activity of TiO2 nanotubes. The TiO2 nanotubes prepared by the electrochemical oxidation of titanium in dimethyl sulfoxide (DMSO) with 2% HF were treated in a methanol solution under UV light irradiation. In comparison with the untreated TiO2 nanotubes, the treatment resulted in a dramatic increase in the donor density of the TiO2 nanotubes by approximately 3 orders of magnitude. The treated TiO2 nanotubes exhibited a 15-fold enhancement in photocurrent and a 6.8-fold increase in the photoelectrochemical degradation of 4-nitrophenol, significant for hydrogen generation and wastewater treatment. 相似文献
36.
The glassy carbon electrode was modified with a nickel pentacyanonitrosylferrate film by electrodeposition of Ni and subsequent derivatization with NaPCNF. The film was characterized by XPS and electrochemical methods. Cyclic voltammetry of the NiPCNF onto the GC shows a redox couple (FeIII/FeII) with E°′ of 538 mV (Ipa/Ipc around 1) and ΔEp of 93 mV in 0.5 mol L?1 KNO3, with a diffusion‐controlled process. There was a decrease of anodic peak currents of the film in the presence of sulfide and 2‐propanethiol due to a precipitation reaction on the film surface by nucleophilic attack. 相似文献
37.
Ryky Nelson Christina Ertural Janine George Volker L. Deringer Geoffroy Hautier Richard Dronskowski 《Journal of computational chemistry》2020,41(21):1931-1940
We present an update on recently developed methodology and functionality in the computer program Local Orbital Basis Suite Toward Electronic-Structure Reconstruction (LOBSTER) for chemical-bonding analysis in periodic systems. LOBSTER is based on an analytic projection from projector-augmented wave (PAW) density-functional theory (DFT) computations (Maintz et al., J. Comput. Chem. 2013 , 34, 2557), reconstructing chemical information in terms of local, auxiliary atomic orbitals and thereby opening the output of PAW-based DFT codes to chemical interpretation. We demonstrate how LOBSTER has been improved by taking into account time-reversal symmetry, thereby speeding up the DFT and LOBSTER calculations by a factor of 2. Over the recent years, the functionalities have also been continually expanded, including accurate projected densities of states (DOSs), crystal orbital Hamilton population (COHP) analysis, atomic and orbital charges, gross populations, and the recently introduced k -dependent COHP. The software is offered free-of-charge for non-commercial research. 相似文献
38.
Kristina Hetherington Dr. Zsofia Hegedus Dr. Thomas A. Edwards Dr. Richard B. Sessions Prof. Adam Nelson Prof. Andrew J. Wilson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(34):7638-7646
Protein–protein interactions (PPIs) control virtually all cellular processes and have thus emerged as potential targets for development of molecular therapeutics. Peptide-based inhibitors of PPIs are attractive given that they offer recognition potency and selectivity features that are ideal for function, yet, they do not predominantly populate the bioactive conformation, frequently suffer from poor cellular uptake and are easily degraded, for example, by proteases. The constraint of peptides in a bioactive conformation has emerged as a promising strategy to mitigate against these liabilities. In this work, using peptides derived from hypoxia-inducible factor 1 (HIF-1α) together with dibromomaleimide stapling, we identify constrained peptide inhibitors of the HIF-1α/p300 interaction that are more potent than their unconstrained sequences. Contrary to expectation, the increased potency does not correlate with an increased population of an α-helical conformation in the unbound state as demonstrated by experimental circular dichroism analysis. Rather, the ability of the peptide to adopt a bioactive α-helical conformation in the p300 bound state is better supported in the constrained variant as demonstrated by molecular dynamics simulations and circular dichroism difference spectra. 相似文献
39.
Simone Manzini Dr. Albert Poater Dr. David J. Nelson Prof. Dr. Luigi Cavallo Prof. Dr. Alexandra M. Z. Slawin Prof. Dr. Steven P. Nolan 《Angewandte Chemie (International ed. in English)》2014,53(34):8995-8999
The decomposition of a series of benzylidene, methylidene, and 3‐phenylindenylidene complexes has been probed in alcohol solution in the presence of base. Tricyclohexylphosphane‐containing precatalysts are shown to yield [RuCl(H)(H2)(PCy3)2] in isopropyl alcohol solutions, while 3‐phenylindenylidene complexes lead to η5‐(3‐phenyl)indenyl products. The potential‐energy surfaces for the formation of the latter species have been probed using density functional theory studies. 相似文献
40.
Ahmed Hussein Msmali Mark I. Nelson Maureen P. Edwards 《Journal of mathematical chemistry》2014,52(8):2234-2258
We provide a detailed, and thorough, investigation into the concentration multiplicity and dynamic stability of a prototype non-linear chemical mechanism: quadratic autocatalysis subject to non-linear decay in a continuously stirred tank reactor. This model was previously investigated in the literature using numerical path-following techniques. The contribution of this study is the application of singularity theory and degenerate Hopf-bifurcation theory to obtain analytical representations of many of the features of interest in this system. In particular, we use these presentations to identify critical values of an unfolding parameter below which specified phenomenon are no longer exhibited. 相似文献