Search results for "element"
showing 10 items of 13601 documents
Equilibrium and structural studies of complexes with a hexadentate ligand containing amide, amine and pyridyl nitrogen donors. Crystal structures of …
2002
A novel potentially hexadentate ligand, 1,8-bis(2-pyridylcarbamoyl)-3,6-diazaoctane (pyctrien) has been synthesised as its tetrahydrochloride salt; its protonation constants and the stability constants of the copper(II) and nickel(II) chelates have been determined by potentiometry. Amide group deprotonation permits the formation of [MLH−1]+ and [MLH−2] species in all cases, whereas the detection of the neutral or the protonated species depends on the nature of the metal ions. The solid complexes of copper, nickel and cobalt with the neutral and the deprotonated ligand have been synthesised and characterised by IR and UV–VIS spectroscopy. The amidic groups are coordinated through the oxygen …
Effect of Mg2+ ions on competitive metal ions adsorption/desorption on magnesium ferrite: Mechanism, reusability and stability studies
2021
Abstract The adsorption behavior of magnesium ferrite in single- and multicomponent metal ions solutions in the presence of Mg2+ ions were studied. A dramatic decrease in the adsorption capacity of magnesium ferrite towards Mn2+, Co2+, and Ni2+ ions for comparison study of single- and multicomponent solutions was established. The affinity of the sorbent in accordance with the maximum sorption capacities increases in the following order Cu2+ > Co2+ > Ni2+ > Mn2+. High efficiency of magnesium ferrite regeneration (~100%) with aqueous solutions of magnesium chloride in the concentration range of 0.001–0.1 M was shown. The low degree of toxic metal ions desorption combined with XRD, IR spectros…
Mechanism of sulfur transfer across protein-protein interfaces: The cysteine desulfurase model system
2016
CsdA cysteine desulfurase (the sulfur donor) and the CsdE sulfur acceptor are involved in biological sulfur trafficking and in iron-sulfur cluster assembly in the model bacterium Escherichia coli. CsdA and CsdE form a stable complex through a polar interface that includes CsdA Cys328 and CsdE Cys61, the two residues known to be involved in the sulfur transfer reaction. Although mechanisms for the transfer of a sulfur moiety across protein-protein interfaces have been proposed based on the IscS-IscU and IscS-TusA structures, the flexibility of the catalytic cysteine loops involved has precluded a high resolution view of the active-site geometry and chemical environment for sulfur transfer. H…
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…
Asymmetric [N–I–N]+halonium complexes in solution?
2020
Assessment of the solution equilibria of [bis(pyridine)iodine(I)]+ complexes by ESI-MS and NMR reveals the preference of iodine(I) to form complexes with a more basic pyridine. Mixtures of symmetric [bis(pyridine)iodine(I)]+ complexes undergo statistical ligand exchange, with a predominant entropic driving force favoring asymmetric systems. The influence of ligand basicity, concentration, temperature, and ligand composition is evaluated. Our findings are expected to facilitate the investigations, and the supramolecular and synthetic applications of halonium ions’ halogen bonds. peerReviewed
Self-Assembled Molecular Rafts at Liquid|Liquid Interfaces for Four-Electron Oxygen Reduction
2011
The self-assembly of the oppositely charged water-soluble porphyrins, cobalt tetramethylpyridinium porphyrin (CoTMPyP(4+)) and cobalt tetrasulphonatophenyl porphyrin (CoTPPS(4-)), at the interface with an organic solvent to form molecular "rafts", provides an excellent catalyst to perform the interfacial four-electron reduction of oxygen by lipophilic electron donors such as tetrathiafulvalene (TTF). The catalytic activity and selectivity of the self-assembled catalyst toward the four-electron pathway was found to be as good as that of the Pacman type cofacial cobalt porphyrins. The assembly has been characterized by UV-visible spectroscopy, Surface Second Harmonic Generation, and Scanning …
Cross-Linked Imidazolium Salts as Scavengers for Palladium.
2014
Five imidazolium-based materials have been synthesised and used for the first time as palladium scavengers. Radical reactions of suitable bis-vinylimidazolium salts led to a series of insoluble materials through homo-polymerisation, immobilisation with a 3-mercaptopropyl-modified silica gel or co-polymerisation with ethylene glycol dimethylacrylate. These materials were screened as palladium scavengers with a set of palladium(0) and palladium(II) compounds in different solvents and at different starting amounts of palladium. In many cases, residual amounts of palladium were lower than 5 ppm, as requested for the manufacture of active pharmaceutical ingredients and fine chemicals. The applic…
Plasma selenium levels and oxidative stress biomarkers: a gene-environment interaction population-based study.
2014
The role of selenium exposure in preventing chronic disease is controversial, especially in selenium-repleted populations. At high concentrations, selenium exposure may increase oxidative stress. Studies evaluating the interaction of genetic variation in genes involved in oxidative stress pathways and selenium are scarce. We evaluated the cross-sectional association of plasma selenium concentrations with oxidative stress levels, measured as oxidized to reduced glutathione ratio (GSSG/GSH), malondialdehyde (MDA), and 8-oxo-7,8-dihydroguanine (8-oxo-dG) in urine, and the interacting role of genetic variation in oxidative stress candidate genes, in a representative sample of 1445 men and women…
Correlations of blood selenium with hematological parameters in West German adults.
1988
The serum selenium and the whole blood selenium of 72 healthy persons (47 women, 25 men) was determined. There exist sex specific differences of the whole blood selenium between men (98 +/- 19 micrograms Se/L) and women (89 +/- 17 micrograms Se/L). The serum selenium did not show sex specific differences, but sex specific differences are found if the total amount of extracellular selenium is calculated by correction of the serum selenium with the hematocrit. Women have more extra-cellular selenium/L whole blood (40 +/- 8 micrograms Se) than men (36 +/- 7 micrograms Se). Men have more intraerythrocyte selenium (cellular selenium = 67 +/- 14 micrograms Se) in one L whole blood than women (52 …
The arsenic content of human semen.
2009
Arsenic concentration was measured by atomic absorption spectrometer in ejaculates of 13 subfertile men, 6 control individuals and pool-ejaculate of 24 further andrological patients. While the detection limit was 1 microgram/l, arsenic concentration amounted to 2 micrograms AS/l in ejaculates. In the cellular fractions of seminal fluid, concentration of arsenic was under the detection limit. Arsenic concentration of smokers and non-smokers did not differ.