Search results for "Oxidation."

Electrochemical oxidation of tetramethoxy precursor as a key step for the synthesis of coenzyme Q10

2007

The feasibility of electrosynthesis of coenzyme Q10 (1) by electrooxidation of tetramethoxy precursor (2) has been investigated at carbon, Pt and BDD anodes in a divided cell. The process strongly depends on the applied potential, anode material and water content of the solvent. At carbon anodes in CH3CN/CH2Cl2 + 0.15 M Bu4NBF4 at proper operative conditions high faradic efficiency (>60%) and excellent selectivity (95–97%) of the target product were obtained. Keywords: Electrosynthesis, Coenzyme Q10, Anodic oxidation

Mo-containing tetragonal tungsten bronzes. The influence of tellurium on catalytic behaviour in selective oxidation of propene

2009

Abstract Te-free and Te-containing multicomponent Mo-based catalysts presenting tetragonal tungsten bronze (TTB) structure have been prepared, characterized and tested for the selective oxidation of propene. The catalysts were prepared hydrothermally and heat treated at 700 °C. The structural characterization performed by means of XRD, FTIR, SAED and HRTEM confirms the incorporation of tellurium to the TTB structural framework and shows that its presence does not modify in essence the crystalline structure. However, the incorporation of Te strongly modifies the catalytic performance, and the highest yield to acrolein has been achieved on catalysts with Te/Mo atomic ratios in bulk of 0.03. T…

Effects of aldicarb and propoxur on cytotoxicity and lipid peroxidation in CHO-K1 cells

2010

Abstract Cytotoxic effects of aldicarb, its sulfone and sulfoxide, and propoxur, lipid peroxidation and antioxidant parameters in Chinese Hamster Ovary (CHO-K1) cells were determined. d , l -buthionine-( S , R )-sulfoximine (BSO) was assayed to determine the role of GSH in the protection against carbamate cytotoxicity. Pre-treatment with 60 μM BSO, induced a significant decrease in the glutathione reductase (GR; 64–141%), the glutathione peroxidase (GPx; 10–30%) and the glutathione S-transferase (GST; 59–93%) activities, and its GSH levels (79–85%), while the oxidized glutathione (GSSG) levels significantly increased (64–78%) respect to experiment non-BSO-pretreated. Carbamates BSO pre-trea…

Chemical oxidation and reduction of hexachlorocyclohexanes: A review

2019

Abstract Lindane (γ-hexachlorocyclohexane) and its isomers (HCH) are some of the most common and most easily detected organochlorine pesticides in the environment. The widespread distribution of lindane is due to its use as an insecticide, accompanied by its persistence and bioaccumulation, whereas HCH were disposed of as waste in unmanaged landfills. Unfortunately, certain HCH (especially the most reactive ones: γ- and α-HCH) are harmful to the central nervous system and to reproductive and endocrine systems, therefore development of suitable remediation methods is needed to remove them from contaminated soil and water. This paper provides a short history of the use of lindane and a descri…

Multibiomarker approach to fipronil exposure in the fish Dicentrarchus labrax under two temperature regimes

2020

12 pages, 5 figures, 3 tables, supplementary data https://doi.org/10.1016/j.aquatox.2019.105378

Fluorescence emission and enhanced photochemical stability of Zn(II)-5-triethyl ammonium methyl salicylidene ortho-phenylendiiminate interacting with…

2010

Abstract The photophysical and photochemical properties of the cationic Zn II complex of 5-triethyl ammonium methyl salicylidene ortho-phenylendiimine (ZnL 2+ ) interacting with native DNA were investigated by steady state and time-resolved fluorescence spectroscopies. Experimental results indicate that, in the presence of DNA, ZnL 2+ is efficiently protected from a photochemical process, which occurs when it is in the free state dispersed in aqueous solution. The analysis of the absorption and emission spectra of ZnL 2+ , both stored in the dark and after exposure to tungsten lamp light for 24 h, corroborated by quantum chemical calculations, allowed us to point out that ZnL 2+ undergoes a…

Cytotoxic effect of As(III) in Caco-2 cells and evaluation of its human intestinal permeability.

2005

Inorganic arsenic has been classified as a carcinogen for humans (Group I). However, its transit across the human intestinal epithelium has not been characterized. Using Caco-2 cells, the thiol-redox balance and apparent permeability coefficients (P(app)) for As(III) in the apical to basolateral (AP-BL) and basolateral to apical (BL-AP) direction were evaluated. After As(III) exposure, GSH-induced synthesis was observed, increasing the GSH/GSSG ratio by elevating the As(III) concentration. The AP-BL permeabilities decreased as the As(III) concentrations increased, indicating the existence of a mediated transport mechanism. The (BL-AP)/(AP-BL) permeability ratios were higher than unity, sugg…

Biomarkers of lipid peroxidation in the aqueous humor of primary open-angle glaucoma patients

2016

Objective To investigate the lipid peroxidation (PEROX) processes in primary open-angle glaucoma (POAG) patients, and whether this mechanism may be related to disease progression. Material and methods A prospective, observational, cross-sectional, non-experimental, and analytical study was conducted on a case and a comparison group, consisting of 175 surgical patients divided into: (1) POAG group (GG; n = 88) and (2) comparison group of patients with cataracts (CG; n = 87). Demographic data, patient characteristics, lifestyle data, as well as ophthalmological examination were registered in an Excel spreadsheet. Biochemical data were obtained by processing the aqueous humor collected at the …

IONIC LIQUIDS MODIFIED CATALYSTS: SYNTHESIS, IMMOBILIZATION AND USES.

Synthesis, catalytic activity and recovery of Ionic liquid modified and un-modified catalysts have mainly been focused in this thesis. Particularly, our attention has been given to 2,2,6,6-Tetramethyl-piperidine-N-oxyl (TEMPO) catalyst for its unique redox behavior in alcohol oxidation to carbonyl compounds. In order to tag appropriate number of IL moieties, [60]Fullerene as well as benzylic linker units were employed as a molecular support. However, covalently supported catalysts were recovered by a short silica pad while, ionic liquid-tagged TEMPO catalysts were recovered by a non-covalent “Release and Catch” approach using silica grafted polymeric multilayered covalently supported ionic …

Dynamics of closure of zinc bis-porphyrin molecular tweezers with copper(II) ions and electron transfer.

2011

Zinc bis-porphyrin molecular tweezers composed of a N(4) spacer bound through pyridyl units to the meso position of porphyrins were synthesized, and the tweezers are closed by the coordination of a copper(II) ion inside the spacer ligand. The effect of the π-π interaction between the porphyrin rings in the closed conformation on the absorption spectra of multi-electron oxidized species and the reduction potentials were clarified by chemical and electrochemical oxidation of the closed form of the zinc bis-porphyrin molecular tweezers in comparison with the open form without copper(II) ion and the corresponding porphyrin monomer. The shifts in redox potentials and absorption spectrum of the p…