Search results for "visual_art"
showing 10 items of 2987 documents
Persistence of oxidation state III of gold in thione coordination
2017
Ligands N,N'-tetramethylthiourea and 2-mercapto-1-methyl-imidazole form stable Au(III) complexes [AuCl3(N,N'-tetramethylthiourea)] (1) and [AuCl3(2-mercapto-1-methyl-imidazole)] (2) instead of reducing the Au(III) metal center into Au(I), which would be typical for the attachment of sulfur donors. Compounds 1 and 2 were characterized by spectroscopic methods and by X-ray crystallography. The spectroscopic details were explained by simulation of the UV-Vis spectra via the TD-DFT method. Additionally, computational DFT studies were performed in order to find the reason for the unusual oxidation state in the crystalline materials. The preference for Au(III) can be explained via various weak in…
Pigments and their solubility in and extractability by supercritical CO2 - I: the case of curcumin
2000
A specially designed high-pressure cell was used simultaneously as extractor/autoclave and photometric cell in a Perkin Elmer Lambda 5 spectrophotometer. Based on this cell, a simple method was developed to determine the extractability of pigments by pure and by modified supercritical (sc) CO2. The method is demonstrated with curcumin from turmeric. With sc CO2 modified by 10% ethanol, the extraction yield for curcumin from two commercial finely ground dry turmeric samples was about 100%, measured by reference to the (complete) extraction of samples of the same charge with pure ethanol under standard conditions. Extractable curcumin content was from 1.8 to 2.5%, with three samples of turmer…
A Computational Study of Adsorption of CO2, SO2, and H2CO on Free-Standing and Molybdenum-Supported CaO Films
2018
Oxide films play a significant role in a wide range of fields from catalysis to solar cell materials. CaO films are promising sorbents for many environmentally harmful molecules. Here, we report a systematic investigation of adsorption of CO2, SO2, and H2CO on bulk and Mo-supported CaO(100) films using density functional theory. Significant effects on adsorption energy, charge transfer to the molecules, and degree of the C–O bond activation were demonstrated on Mo-supported CaO films by changing the film thickness, composition, and the strength and direction of an applied external electric field. These findings are relevant for interpreting results from scanning tunneling microscopy of smal…
Structural and Electrochemical Analysis of CIGS: Cr Crystalline Nanopowders and Thin Films Deposited onto ITO Substrates
2021
A new approach for the synthesis of nanopowders and thin films of CuInGaSe2 (CIGS) chalcopyrite material doped with different amounts of Cr is presented. The chalcopyrite material CuInxGa1 − xSe2 was doped using Cr to form a new doped chalcopyrite with the structure CuInxCryGa1 − x − ySe2, where x = 0.4 and y = 0.0, 0.1, 0.2, or 0.3. The electrical properties of CuInx CryGa1 − x − ySe2 are highly dependent on the Cr content and results show these materials as promising dopants for the fabrication thin film solar cells. The CIGS nano-precursor powder was initially synthesized via an autoclave method, and then converted into thin films over transparent substrates. Both crystalline precursor p…
Molecular mechanics models for the image charge, a comment on “including image charge effects in the molecular dynamics simulations of molecules on m…
2017
We re-investigate the image charge model of Iori and Corni (Iori and Corni, J. Comput. Chem. 2008, 29, 1656). We find that a simple symmetrization of their model allows to obtain quantitatively correct results for the electrostatic interaction of a water molecule with a metallic surface. This symmetrization reduces the magnitude of the electrostatic interaction to less than 10% of the total interaction energy. © 2017 Wiley Periodicals, Inc.
Characterization of Rabbit Mesenchymal Cell Attachment on Calcium Phosphate Surface
2014
In the current study, the effect of three different treated surfaces of hydroxyapatite and β-tricalcium phosphate on mesenchymal cell attachment has been investigated. Calcium phosphate powders have been synthesized, uniaxially pressed, polished and sintered. Mesenchymal cells have been seeded onto unpolished, polished and polished-thermally etched ceramic samples. The ceramic samples have been characterized by XRD, FTIR and SEM. Results have shown that the best cell attachment and morphology are on the unpolished surface indicating that relatively rough surface is better for cell application.
Effect of in Doping on the ZnO Powders Morphology and Microstructure Evolution of ZnO:In Ceramics as a Material for Scintillators
2018
Transparent ZnO ceramics are of interest for use as material for high-efficiency fast scintillators. Doping ZnO ceramics in order to improve complex of their properties is a promising direction. In the present research, the role of indium in the ZnO nanopowders surface interactions and in the change of microstructures and photoluminescence (PL) characteristics of sintered cera-mics is considered. Undoped and 0.13 wt% In doped ZnO ceramics are obtained by hot pressing sintering. It has been found that indium leads to the transition of initially faceted ZnO particles to rounded, contributing to good sintering with formation of diffusion active grain boundaries (GBs). Unlike ZnO ceramics, ZnO:…
Uncapping the N-terminus of a ubiquitous His-tag peptide enhances its Cu2+ binding affinity
2019
Metal complexes with an N-terminally free and N-terminally acetylated polyhistidine region of Echis ocellatus venom, with an interesting His-rich motif present in numerous metal binding proteins from all kingdoms of life (DHDHDHHHHHHPGSSV-NH2 and Ac-DHDHDHHHHHHPGSSV-NH2) show the role of the free amino group in the thermodynamic enhancement of Cu2+, Ni2+ and Zn2+ binding. In the studied sequences, Cu2+ can be coordinated by different sets of imidazole rings, and a 3–10 helix is detected in close proximity of Cu2+ binding sites. The complexes are more stable than those with a typical His6-tag, despite a similar copper(II) coordination mode in both cases.
Structural Origin of Metal Specificity in Isatin Hydrolase from Labrenzia aggregata Investigated by Computer Simulations.
2017
We performed quantum-chemical calculations, ab initio molecular dynamics, hybrid quantum mechanics/molecular mechanics (QM/MM) and enhanced sampling metadynamics simulations to investigate the origin of metal specificity in isatin hydrolase from Labrenzia aggregata. The peculiar octahedral binding geometry of the Mn2+ ion in the Michaelis complex includes both the isatin substrate and the catalytic water within the first coordination shell of the cation. Our calculations show that the same arrangement of the ligands cannot be efficiently achieved in the presence of other small divalent metal cations such as Zn2+ or Cu2+ . On the contrary, bulkier alkaline-earth cations such as Mg2+ , which …
Chemical and physical characterization of thermal aggregation of model proteins modulated by zinc(II) and copper(II) ions
2016
BACKGROUND: Metal ions are implicated in protein aggregation processes of several neurodegenerative pathologies, where the protein deposition occurs, and in the biotechnology field like the food technology where many processes in food manufacturing are based on thermal treatments. OBJECTIVE: The influence of Cu2+ or Zn2+ ions on the thermal aggregation process of Bovine beta-lactoglobulin (BLG) and Bovine Serum Albumin (BSA), two protein models, was studied with the aim of delineating the role of these ions in the protein aggregation kinetics and to clarify the related molecular mechanisms. METHODS: The protein structure changes were monitored by Raman spectroscopy, whereas the aggregate gr…