Search results for "OXIDATION"
showing 10 items of 1913 documents
Direct measurement of the melting temperature of supported DNA by electrochemical method
2003
The development of biosensors based on DNA hybridization requires a more precise knowledge of the thermodynamics of the hybridization at a solid interface. In particular, the selectivity of hybridization can be affected by a lot of parameters such as the single-strand (ss)DNA density, the pH, the ionic strength or the temperature. The melting temperature, T(m), is in part a function of the ionic strength and of the temperature and therefore provides a useful variable in the control of the selectivity and sensitivity of a DNA chip. The electrochemical technique has been used to determine the T(m) values when the probe is tethered by a DNA self-assembled monolayer (SAM). We have built a speci…
Molecular and electronic structure of square-planar nickel(ii), nickel(iii) and nickel(iii)π-cation radical complexes with a tetradentate o-phenylene…
2005
The molecular and electronic structures of the electron transfer series of four-coordinate square-planar nickel complexes with the ligand o-phenylenebis(N'-methyloxamidate), [NiL]z (z = 2-, 1-, 0), have been evaluated by DFT and TDDFT calculations, and most of their experimentally available structural and spectroscopic properties (X. Ottenwaelder et al., Dalton Trans., 2005, DOI: 10.1039/b502478a) have been reasonably reproduced at the B3LYP level of theory. The anionic species [NiL]2- and [NiL]- are genuine low-spin nickel II and nickel III complexes with diamagnetic singlet (S = 0) and paramagnetic doublet (S = 1/2) states, respectively. The nickel III complex presents shorter Ni-N(amidat…
Flow-chemiluminescence: a growing modality of pharmaceutical analysis.
2001
The present article deals with a review of the applications of the chemiluminescence to pharmaceutical analyses by using continuous-flow assemblies. A comprehensive study on the fundamentals of the chemiluminescence is also included.
Biomass-based composite catalysts for catalytic wet peroxide oxidation of bisphenol A:preparation and characterization studies
2019
The wet granulation process was used to prepare new, efficient, and cost-effective granular biomass-based composite catalysts for catalytic wet peroxide oxidation (CWPO) of bisphenol A (BPA). The most stable composite granules was prepared by mixing biomass-based carbon residue (CR) with metakaolin (MK) combined with calcium oxide (CaO) or cement and a solvent (NaOH or KOH). For all the prepared composite granules, the optimized binding agents to carbon ratio was 0.3, the solvent to carbon ratio 1.2, and the agitation rate 1200 rpm. The specific surface area of the prepared catalysts was 152–205 m2/g. The composite granular catalyst (CR + MK + CaO + NaOH) had the most durable and stable str…
The significance of the order of impregnation on the activity of vanadia promoted palladium-alumina catalysts for propane total oxidation
2011
The increased activity of alumina-supported palladium catalysts promoted with vanadium oxide has been investigated. Three different vanadium promoted Pd/Al2O3 catalysts with the same composition but synthesized employing sequential and co-impregnation were tested for the total oxidation of propane. The order of impregnation was critical to produce high activity catalysts. Vanadium and palladium co-impregnation on the Al2O3 support led to the most active catalyst, whereas the step-wise impregnated catalysts show a catalytic performance similar to or slightly better than unpromoted palladium catalysts. The high activity of the co-impregnated catalysts is related to the particle size and oxida…
Molecular dynamics simulations of the nano-scale room-temperature oxidation of aluminum single crystals
2005
The oxidation of aluminum single crystals is studied using molecular dynamics (MD) simulations with dynamic charge transfer between atoms. The simulations are performed on three aluminum low-index surfaces ((1 0 0), (1 1 0) and (1 1 1)) at room temperature. The results show that the oxide film growth kinetics is independent of the crystallographic orientation under the present conditions. Beyond a transition regime (100 ps) the growth kinetics follow a direct logarithmic law and present a limiting thickness of 3 nm. The obtained amorphous structure of the oxide film has initially Al excess (compared to the composition of Al2O3) and evolves, during the oxidation process, to an Al percentage …
Enhanced susceptibility of cholesteryl sulfate-enriched low density lipoproteins to copper-mediated oxidation
1995
AbstractCholesteryl sulfate (CS) is a minor component of cell membranes, also present in lipoproteins, and its exact function is unknown. Since oxidation of low density lipoproteins (LDL) is thought to be an important determinant of atherogenesis, we investigated the influence of CS enrichment on copper-mediated oxidation of LDL. CS was found to act as a pro-oxidant, as measured by lipid oxidation parameters. The results also suggest that these effects were dependent on the sulfate group since pure cholesterol or cholesteryl acetate did not promote Cu2+-mediated oxidation. Our findings imply that CS may affect the oxidizability and hence the potential atherogenicity of LDL.
Pro-oxidant effects of 7-hydroperoxycholest-5-en-3β-ol on the copper-initiated oxidation of low density lipoprotein
1995
AbstractIn low density lipoproteins (LDL) supplemented with aged cholesterol and oxidized in the presence of Cu2+, an increase of the lipid oxidation parameters was observed compared with pure cholesterol-enriched LDL. A compound, identified as 7-hydroperoxycholesterol (7HPC), isolated from aged cholesterol and added to LDL, reproduced the above effects. The results indicate that the pro-oxidant effect of 7HPC is dependent on the hydroperoxy group since the corresponding alcohol derivative, 7α-hydroxycholesterol, had no such effect. These data suggest that among the LDL-associated lipid peroxides, cholesterol peroxides may have important implications in the susceptibility of this lipoprotei…
C172S Substitution in the Chloroplast-encoded Large Subunit Affects Stability and Stress-induced Turnover of Ribulose-1,5-bisphosphate Carboxylase/Ox…
1999
Previous work has indicated that the turnover of chloroplast ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1. 39) may be controlled by the redox state of certain cysteine residues. To test this hypothesis, directed mutagenesis and chloroplast transformation were employed to create a C172S substitution in the Rubisco large subunit of the green alga Chlamydomonas reinhardtii. The C172S mutant strain was not substantially different from the wild type with respect to growth rate, and the purified mutant enzyme had a normal circular dichroism spectrum. However, the mutant enzyme was inactivated faster than the wild-type enzyme at 40 and 50 degrees C. In contrast, C172S mutant …
Cysteines 449 and 459 modulate the reduction-oxidation conformational changes of ribulose 1.5-bisphosphate carboxylase/oxygenase and the translocatio…
2006
The role of cysteines 449 (Cys449) and 459 (Cys459) from the large subunit (LS) of ribulose 1-5-bisphosphate carboxylase/oxygenase (Rubisco) in the reduction-oxidation (redox) regulation of the enzyme was assessed by site-directed mutagenesis of these residues and chloroplast transformation of Chlamydomonas reinhardtii. In vitro studies indicated that mutations C449S, C459S or C449S/ C459S do not affect the activity and proteolytic susceptibility of the enzyme in the reduced state. However, when oxidized, the mutant enzymes differed from the wild type (WT), showing an increased resistance to inactivation and, in the case of the double mutant (DM), an altered structural conformation as refle…