scholarly journals Production of hydroxyl radicals from the simultaneous generation of superoxide and nitric oxide

1992 ◽  
Vol 281 (2) ◽  
pp. 419-424 ◽  
Author(s):  
N Hogg ◽  
V M Darley-Usmar ◽  
M T Wilson ◽  
S Moncada
Keyword(s):  
Nitric Oxide ◽  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Sodium Benzoate ◽  
Fenton Reaction ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Radical Scavenger ◽  
Fluorescence Emission Spectra ◽  
Simultaneous Generation

Both nitric oxide (NO) and superoxide are generated by macrophages, neutrophils and endothelial cells. It has been postulated that the generation of these two radicals under physiological conditions can lead to the formation of peroxynitrite and (as a result of the homolytic lysis of this molecule) the production of hydroxyl radicals. We have used 3-morpholinosydnonimine N-ethylcarbamide (SIN-1), a sydnonimine capable of generating both NO and superoxide simultaneously, to test this hypothesis. SIN-1 (1 mM) generated superoxide and NO at rates of 7.02 microM/min and 3.68 microM/min respectively in phosphate-buffered saline, pH 7.2, at 37 degrees C. Incubation of SIN-1 with both deoxyribose and sodium benzoate resulted in the formation of malondialdehyde (MDA). In addition, the incubation of SIN-1 with sodium benzoate resulted in the production of compounds with fluorescence emission spectra characteristic of hydroxylated products. Both the production of MDA and the generation of fluorescent compounds were inhibited by the hydroxyl radical scavenger mannitol. In all the above respects, SIN-1 mimicked the production of hydroxyl radicals from the ascorbate-driven Fenton reaction. Catalase had no effect on the SIN-1-dependent generation of MDA, and superoxide dismutase was partially inhibitory. SIN-1 produces an oxidant with the properties of the hydroxyl radical by a mechanism clearly different to that of the Fenton reaction. We conclude that the simultaneous production of NO and superoxide from SIN-1 results in the formation of hydroxyl radicals.

scholarly journals Involvement of a local Fenton reaction in the reciprocal modulation by O2 of the glucagon-dependent activation of the phosphoenolpyruvate carboxykinase gene and the insulin-dependent activation of the glucokinase gene in rat hepatocytes

1998 ◽  
Vol 335 (2) ◽  
pp. 425-432 ◽  
Author(s):  
Thomas KIETZMANN ◽  
Torsten PORWOL ◽  
Karl ZIEROLD ◽  
Kurt JUNGERMANN ◽  
Helmut ACKER
Keyword(s):  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Fenton Reaction ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Gene Activation ◽  
Three Dimensional ◽  
Rat Hepatocytes ◽  
Confocal Laser ◽  
Radical Scavenger ◽  
Insulin Dependent

H2O2 mimicked the action of periportal pO2 in the modulation by O2 of the glucagon-dependent activation of the phosphoenolpyruvate carboxykinase (PCK) gene and the insulin-dependent activation of the glucokinase (GK) gene. H2O2 can be converted in the presence of Fe2+ in a Fenton reaction into hydroxyl anions and hydroxyl radicals (•OH). The hydroxyl radicals are highly reactive and might interfere locally with transcription factors. It was the aim of the present study to investigate the role of and to localize such a Fenton reaction. Hepatocytes cultured for 24 h were treated under conditions mimicking periportal or perivenous pO2 with glucagon or insulin plus the iron chelator desferrioxamine (DSF) or the hydroxyl radical scavenger dimethylthiourea (DMTU) to inhibit the Fenton reaction. PCK mRNA was induced by glucagon maximally under conditions of periportal pO2 and half-maximally under venous pO2. GK mRNA was induced by insulin with reciprocal modulation by O2. DSF and DMTU reduced the induction of PCK mRNA to about half-maximal and increased the induction of GK mRNA to maximal under both O2 tensions. Hydroxyl radical formation was maximal under arterial pO2. Perivenous pO2, DSF and DMTU each decreased the formation of •OH to about 70% of control. The Fenton reaction could be localized in a perinuclear space by confocal laser microscopy and three-dimensional reconstruction techniques. In the same compartment, iron could be detected by electron-probe X-ray microanalysis. Thus a local Fenton reaction is involved in the O2 signalling, which modulated the glucagon- and insulin-dependent PCK gene and GK gene activation.

scholarly journals Contribution of Oxidative Damage to Antimicrobial Lethality

2009 ◽  
Vol 53 (4) ◽  
pp. 1395-1402 ◽  
Author(s):  
Xiuhong Wang ◽  
Xilin Zhao
Keyword(s):  
Oxidative Stress ◽  
Escherichia Coli ◽  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Fenton Reaction ◽  
Iron Chelator ◽  
Radical Scavenger ◽  
Alkyl Hydroperoxide ◽  
Hydroxyl Radical Scavenger ◽  
Rapid Conversion

ABSTRACT A potential pathway linking hydroxyl radicals to antimicrobial lethality was examined by using mutational and chemical perturbations of Escherichia coli. Deficiencies of sodA or sodB had no effect on norfloxacin lethality; however, the absence of both genes together reduced lethal activity, consistent with rapid conversion of excessive superoxide to hydrogen peroxide contributing to quinolone lethality. Norfloxacin was more lethal with a mutant deficient in katG than with its isogenic parent, suggesting that detoxification of peroxide to water normally reduces quinolone lethality. An iron chelator (bipyridyl) and a hydroxyl radical scavenger (thiourea) reduced the lethal activity of norfloxacin, indicating that norfloxacin-stimulated accumulation of peroxide affects lethal activity via hydroxyl radicals generated through the Fenton reaction. Ampicillin and kanamycin, antibacterials unrelated to fluoroquinolones, displayed behavior similar to that of norfloxacin except that these two agents showed hyperlethality with an ahpC (alkyl hydroperoxide reductase) mutant rather than with a katG mutant. Collectively, these data are consistent with antimicrobial stress increasing the production of superoxide, which then undergoes dismutation to peroxide, from which a highly toxic hydroxyl radical is generated. Hydroxyl radicals then enhance antimicrobial lethality, as suggested by earlier work. Such findings indicate that oxidative stress networks may provide targets for antimicrobial potentiation.

Optical Properties and Zinc Nitride Thin Films Prepared Using Magnetron Reactive Sputtering

2014 ◽  
Vol 940 ◽  
pp. 11-15
Author(s):  
Jun Qin Feng ◽  
Jun Fang Chen
Keyword(s):  
Thin Films ◽  
Band Gap ◽  
Near Infrared ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Sem Images ◽  
Fluorescence Emission Spectra ◽  
Glass Substrates ◽  
Zinc Nitride ◽  
Direct Band

Zinc nitride films were deposited by ion sources-assisted magnetron sputtering with the use of Zn target (99.99% purity) on 7059 glass substrates. The films were characterized by XRD, SEM and EDS, the results of which show that the polycrystalline zinc nitride thin film can be grown on the glass substrates, the EDS spectrum confirmed the chemical composition of the films and the SEM images revealed that the zinc nitride thin films have a dense structure. Ultraviolet-visible-near infrared spectrophotometer was used to study the transmittance behaviors of zinc nitride thin films, which calculated the optical band gap by Davis Mott model. The results of the fluorescence emission spectra show the zinc nitride would be a direct band gap semiconductor material.

Stress and Phase Transformation Phenomena in Oxide Films: Real-Time Spectroscopic Measurements

1992 ◽  
Vol 271 ◽  
Author(s):  
Gregory J. Exarhos ◽  
Nancy J. Hess
Keyword(s):  
Phase Transformation ◽  
Applied Pressure ◽  
Oxide Films ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Film Deposition ◽  
Optical Methods ◽  
Fluorescence Emission Spectra ◽  
Line Intensities ◽  
Deposition Parameters

ABSTRACTIn situ optical methods are reviewed for characterization of phase transformation processes and evaluation of residual stress in solution-deposited metastable oxide films. Such low density films most often are deposited as disordered phases making them prone to crystallization and attendant densification when subjected to increased temperature and/or applied pressure. Inherent stress imparted during film deposition and its evolution during the transformation are evaluated from phonon frequency shifts seen in Raman spectra (TiO2) or from changes in the laser-induced fluorescence emission spectra for films containing rare earth (Sm+3:Y3Al5O12) or transition metal (Cr+3 :Al2O3) dopants. The data in combination with measured increases in line intensities intrinsic to the evolving phase are used to follow crystallization processes in thin films. In general, film deposition parameters are found to influence the crystallite ingrowth kinetics and the magnitude of stress and stress relaxation in the film during the transformation. The utility of these methods to probe crystallization phenomena in oxide films will be addressed.

scholarly journals Fluorescence emission spectra of silver and silver/cobalt nanoparticles

2012 ◽  
Vol 19 (3) ◽  
pp. 943-947 ◽  
Author(s):  
Z. Parang ◽  
A. Keshavarz ◽  
S. Farahi ◽  
S.M. Elahi ◽  
M. Ghoranneviss ◽  
...  
Keyword(s):  
Fluorescence Emission ◽  
Emission Spectra ◽  
Cobalt Nanoparticles ◽  
Fluorescence Emission Spectra

pH sensitive smart gels of cetylpyridinium chloride in binary solvent mixtures: phase behaviour, structure and composition

RSC Advances ◽  
2015 ◽  
Vol 5 (62) ◽  
pp. 50306-50311 ◽  
Author(s):  
Illa Ramakanth ◽  
Jaromír Pištora
Keyword(s):  
Cetylpyridinium Chloride ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Phase Behaviour ◽  
Binary Solvent ◽  
Solvent Mixtures ◽  
Gel Formation ◽  
Fluorescence Emission Spectra ◽  
Effect Of Ph ◽  
Binary Solvent Mixtures

Figure showing the effect of pH on CPC gel formation at 25 °C and fluorescence emission spectra of CPC solutions at pH ∼ 11.8.

scholarly journals The dependence of electrophoretic and spectroscopic properties of the pyruvate dehydrogenase complex on mono- and divalent ions.

1994 ◽  
Vol 41 (1) ◽  
pp. 63-72
Author(s):  
T Pawełczyk ◽  
R A Easom ◽  
M S Olson
Keyword(s):  
Ionic Strength ◽  
Pyruvate Dehydrogenase ◽  
Pyruvate Dehydrogenase Complex ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Spectroscopic Properties ◽  
Uv Absorption ◽  
Divalent Ions ◽  
Fluorescence Emission Spectra ◽  
Dehydrogenase Complex

The effects of various mono- and divalent ions on the pyruvate dehydrogenase complex (PDC) were investigated. To determine the radius of PDC under various conditions a two-dimensional agarose gel electrophoresis technique was used. The radius of PDC cross-linked with glutaraldehyde at ionic strength 0.04 M was calculated to be 22.0 +/- 0.1 nm. The presence of K+, Na+ or HPO4(2-) prevented changes in electromobility and of the calculated radius of PDC induced by alteration in ionic strength. The fluorescence emission spectra of PDC depended on the ionic strength and monovalent cations. The fluorescence intensity of PDC increased in the presence of 80 mM K+, and decreased in the presence of 80 mM Na+ with no shift in the emission maximum wavelength. Changes in the ionic strength to which PDC was exposed resulted in alteration of the UV absorption spectra in the 230 nm region. These alterations were prevented by HPO4(2-), whereas Na+ or K+ ions had no effect on the UV absorption spectrum of PDC.

scholarly journals Luminescent Hybrid Materials Based on Curcumin Derivatives Embedded in Palygorskite

2018 ◽  
Vol 55 (1) ◽  
pp. 63-67
Author(s):  
Monica Florentina Raduly ◽  
Valentin Raditoiu ◽  
Alina Raditoiu ◽  
Luminita Eugenia Wagner ◽  
Viorica Amariutei ◽  
...  
Keyword(s):  
Hybrid Materials ◽  
Fluorescence Spectra ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Hydroxyl Groups ◽  
Fluorescent Properties ◽  
Fluorescence Emission Spectra ◽  
Curcumin Derivatives ◽  
Absorption Studies ◽  
Inorganic Matrix

The seven curcumin derivatives were deposited on palygorskite in order to obtain hybrid materials. The fluorescence emission spectra of the obtained materials show a decrease in fluorescence intensity relative to the respective dyes, due to the environments around the dyestuff molecules created in the host matrices. Absorption studies show the best adsorption on the inorganic matrix, for the compounds with the hydroxyl groups. Correlating fluorescence spectra of hybrid materials with the results for absorption spectra of the dyes adsorbtion on the surface of the clay lead to the conclusion that a high percentage of the adsorbed dye had the effect of fluorescence quenching. Thus, it was confirmed that the fluorescent properties of hybrid materials depend on the interactions established between the fluorescent dyestuff and the inorganic network.

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