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Reagent

About: Reagent is a research topic. Over the lifetime, 60091 publications have been published within this topic receiving 1234928 citations. The topic is also known as: reagens.


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Journal ArticleDOI
TL;DR: Reactions of H( 2)O(2) with superoxide dismutase were studied by e.p.r. (electron paramagnetic resonance) spectroscopy and other methods and it is suggested that this histidine is close to the metal in the native enzyme and essential for its enzymic activity.
Abstract: Reactions of H2O2 with superoxide dismutase were studied by e.p.r. (electron paramagnetic resonance) spectroscopy and other methods. In agreement with earlier work, the Cu2+ of the enzyme is reduced by H2O2, although the reaction does not go to completion and its kinetics are not simple. With dilute enzyme the time for half-reduction with 9mm-H2O2 is about 150ms. It is suggested that the reaction is a one-electron reduction, involving liberation of O2−. On somewhat more prolonged exposure to H2O2, the enzyme is inactivated. For enzyme in dilute solution and over a limited range of H2O2 concentrations, inactivation is first-order with respect to enzyme and reagent, with k=3.1m−1·s−1 at 20–25°C. Inactivation is accompanied by marked changes in the e.p.r. and visible spectra and appears to be associated with destruction of one histidine residue per subunit. It is suggested that this histidine is close to the metal in the native enzyme and essential for its enzymic activity.

382 citations

Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: The water-soluble titanium(IV)-porphyrin complex, oxo[5, 10, 15, 20, 20-tetra(4-pyridyl)porphrinato]titanium(IV)[TiO(tpyH4)4+], was found to enhance the spectrophotometric determination of trace amounts of hydrogen peroxide as mentioned in this paper.
Abstract: The water-soluble titanium(IV)–porphyrin complex, oxo[5, 10, 15, 20-tetra(4-pyridyl)porphyrinato]titanium(IV)[TiO(tpyH4)4+], was found to enhance the spectrophotometric determination of trace amounts of hydrogen peroxide. A 0.05 mol dm–3 hydrochloric acid solution containing TiO(tpypH4)4+ was used (the Ti—TPyP reagent), the absorbance of which decreased at 432 nm as hydrogen peroxide was added. This was due to the consumption of the TiO(tpypH4)4+ complex following the formation of peroxo[5, 10, 15, 20-tetra(4-pyridyl)porphyrinato]titanium(IV). The decrease in absorbance at 432 nm (ΔA432) was proportional to the concentration of hydrogen peroxide, from 1.0 × 10–8 to 2.8 × 10–6 mol dm–3, in the sample solution (25 pmol–7.0 nmol per assay). The reaction was accelerated by hydrogen ions; the presence of 1.6 mol dm–3 perchloric acid was found to promote complexation to the greatest extent. A ΔA432 of 1.9 × 105 was found for 1 mol dm–3 hydrogen peroxide. A measurement precision of 1.2% for 1.0 × 10–6 mol dm–3 hydrogen peroxide (n= 8) was obtained. The reagent can be used for the determination of hydrogen peroxide in water samples such as tap water and rainwater over the range from 1.05 × 10–7 to 3.34 × 10–5 mol dm–3.

382 citations

Journal ArticleDOI
TL;DR: Fine-tuning of the reaction conditions allowed remarkably selective transformations within multifunctional substrates, elevating the status of this reagent to that of a highly useful and chemoselective oxidant.
Abstract: o-Iodoxybenzoic acid (IBX), a readily available hypervalent iodine(V) reagent, was found to be highly effective in carrying out oxidations adjacent to carbonyl functionalities (to form α,β-unsaturated carbonyl compounds) and at benzylic and related carbon centers (to form conjugated aromatic carbonyl systems). Mechanistic investigations led to the conclusion that these new reactions are initiated by single electron transfer (SET) from the substrate to IBX to form a radical cation which reacts further to give the final products. Fine-tuning of the reaction conditions allowed remarkably selective transformations within multifunctional substrates, elevating the status of this reagent to that of a highly useful and chemoselective oxidant.

379 citations

Journal ArticleDOI
TL;DR: A glass microchip with a postcolumn reactor was fabricated to conduct postseparation derivatization using o-phthaldialdehyde as a fluorescent "tag" for amino acids as mentioned in this paper.
Abstract: A glass microchip with a postcolumn reactor was fabricated to conduct postseparation derivatization using o-phthaldialdehyde as a fluorescent «tag» for amino acids. This miniaturized separation device was constructed using standard photolithographic, wet chemical etching, and bonding techniques. Effects of the reagent stream on separation efficiency were investigated. In addition, a novel gated injector was demonstrated which maintains the integrity of the analyte, buffer, and reagent streams

377 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20232,117
20224,093
2021785
20201,317
20191,860
20182,158