Search results for "visual_art.visual_art_medium"
showing 10 items of 2982 documents
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…
Multi-channel receptors based on thiopyrylium functionalised with macrocyclic receptors for the recognition of transition metal cations and anions.
2010
We report herein the synthesis and characterization of a family of ligands containing different cation binding sites covalently connected to a thiopyrylium signalling reporter. The receptors L1–L6 are able to signal the presence of certain metal cations via three different channels; i.e. electrochemically, fluorogenically and chromogenically. An acetonitrile solution of L1–L6 shows a bright blue colour due to a charge-transfer band in the 575–585 nm region. The colour variation in acetonitrile of L1–L6 in the presence of the metal cations Ag+, Cd2+, Cu2+, Fe3+, Hg2+, Ni2+, Pb2+ and Zn2+ has been studied. A selective hypsochromic shift of the blue band was found for the systems L4-Pb2+ and L…
Open-chain polyamine ligands bearing an anthracene unit - Chemosensors for logic operations at the molecular level
2001
In this work the absorption and the fluorescence emission properties as well as the protonation sequence of three open chain polyamine ligands of different dimensions bearing an anthracene unit were studied. The protonation and stability constants with Ni2+, Cu2+, Zn2+, and Cd2+ have been determined in 0.15 mol·dm−3 NaCl at 298.1 ± 0.1 K. The values of both protonation and stability constants follow the expected trends according to the number of nitrogen donors, sequence of chelate rings and hydrophilic−hydrophobic balance. Chelation enhancement of the fluorescence emission (CHEF) was observed for some complexes of these ligands with Zn2+ and Cd2+. In contrast the analog complexes containin…
Effect of cadmium pre-exposure in cadmium accumulation by brine shrimp Artemia: Involvement of low-molecular-weight cadmium-binding ligands
1993
Abstract Cadmium is a ubiquitous non-essential element that possesses high toxicity and is easily accumulated from the environment by aquatic organisms. It is known that pre-exposure to cadmium increases the resistance of animals to a subsequent exposure. In this work, we report studies of the effect of pre-exposure to cadmium on the accumulation of this metal from seawater by brine shrimp Artemia, as well as the involvement of low-molecular-weight cadmium-binding ligands in this process. During the pre-exposure experiments, animals were kept in seawater containing 20 mg/litre Cd for 24 h and then transferred to clean seawater for 48 h. Afterwards, pre-exposed and control animals were expos…
The effect of gold addition on the catalytic performance of copper manganese oxide catalysts for the total oxidation of propane
2011
Mixed copper manganese oxide catalysts (Hopcalite) have been studied for the total oxidation of propane, as a model for hydrocarbon volatile organic compound emission control. Catalysts were prepared using coprecipitation with and without gold. Calcination temperature influenced the catalyst activity and those prepared at 300 °C were the most active. Characterization showed that the catalysts had a nanowire-type morphology, and for those containing gold it was present as metallic particles occluded within the nanowires. The incorporation of gold into the catalyst enhanced the activity for propane conversion, but the presence of gold did not noticeably enhance the light-off activity. Althou…
Micro-scale post-fire surface cover changes monitored using high spatial resolution photography in a semiarid environment: A useful tool in the study…
2012
[ES] Although post-fire soil erosion has been studied, little attention has been paid to changes in soil surface cover following fires, despite this being a key factor in understanding the water and sediment yield. This study, at Peñaflor (Spain), investigated the effect of fire on soil erosion using data from soil erosion plots and high spatial resolution photography (HSRP). Measurements were made from October 2003 to October 2005 in a control plot and a plot experimentally exposed to a fire in October 2004. Ground cover components were identified, including vegetation, bare soil, stones, charcoal and ash. Runoff and sediment concentrations were low because of the absence of intense rainfa…