Mechanisms of chain scission and the role of oxidation products in the oxidative radiolysis of ethylenepropylene copolymer

1988 ◽  
Vol 126 (3) ◽  
pp. 211-218 ◽  
Author(s):  
M. S. Kabamba
Keyword(s):  
Chain Scission ◽  
Oxidation Products

scholarly journals The Effectiveness of Glutathione Redox Status as a Possible Tumor Marker in Colorectal Cancer

2021 ◽  
Vol 22 (12) ◽  
pp. 6183
Author(s):  
Delia Acevedo-León ◽  
Lidia Monzó-Beltrán ◽  
Segundo Ángel Gómez-Abril ◽  
Nuria Estañ-Capell ◽  
Natalia Camarasa-Lillo ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Redox State ◽  
Reduced Glutathione ◽  
Redox Status ◽  
Oxidation Products ◽  
Interventional Study ◽  
Thiol Redox State ◽  
Thiol Redox ◽  
Glutathione Redox

The role of oxidative stress (OS) in cancer is a matter of great interest due to the implication of reactive oxygen species (ROS) and their oxidation products in the initiation of tumorigenesis, its progression, and metastatic dissemination. Great efforts have been made to identify the mechanisms of ROS-induced carcinogenesis; however, the validation of OS byproducts as potential tumor markers (TMs) remains to be established. This interventional study included a total of 80 colorectal cancer (CRC) patients and 60 controls. By measuring reduced glutathione (GSH), its oxidized form (GSSG), and the glutathione redox state in terms of the GSSG/GSH ratio in the serum of CRC patients, we identified significant changes as compared to healthy subjects. These findings are compatible with the effectiveness of glutathione as a TM. The thiol redox state showed a significant increase towards oxidation in the CRC group and correlated significantly with both the tumor state and the clinical evolution. The sensitivity and specificity of serum glutathione levels are far above those of the classical TMs CEA and CA19.9. We conclude that the GSSG/GSH ratio is a simple assay which could be validated as a novel clinical TM for the diagnosis and monitoring of CRC.

Free Radicals Generated in Rubber during Fracture

1975 ◽  
Vol 48 (3) ◽  
pp. 445-461 ◽  
Author(s):  
K. L. DeVries
Keyword(s):  
Failure Criteria ◽  
Chain Scission ◽  
Systematic Investigation ◽  
Matrix Interaction ◽  
Filled Elastomers ◽  
Final Note ◽  
Ozone Stress ◽  
Type Of Failure ◽  
Insight Into

Abstract EPR has been used to measure molecular phenomena during fracture of elastomers. To date, because of various technical limitations, the studies have been largely confined to identification of the polymer chain scission site during fracture at low temperature in rubbers, to studying ozone-stress-induced cracking of rubber, to development of a micro-macro Griffith-type failure criteria for this type of failure, and lastly to systematic investigation of the role of filler-matrix interaction in fracture of filled elastomers. It is hoped that the brief outline presented here will give the reader some insight into the uses and potential of the EPR methods for the study of fracture. As a final note, while we have concentrated almost totally on EPR fracture studies in rubbers, there has been fairly extensive EPR work on fracture in oriented plastic, fibers, and films. Even though some of this knowledge may be transferable, directly or indirectly, to elastomers, it has not been reviewed here, but important aspects of these studies have been reviewed elsewhere.

scholarly journals Oxidation of the Tryptophan 32 Residue of Human Superoxide Dismutase 1 Caused by Its Bicarbonate-dependent Peroxidase Activity Triggers the Non-amyloid Aggregation of the Enzyme

2014 ◽  
Vol 289 (44) ◽  
pp. 30690-30701 ◽  
Author(s):  
Fernando R. Coelho ◽  
Asif Iqbal ◽  
Edlaine Linares ◽  
Daniel F. Silva ◽  
Filipe S. Lima ◽  
...  
Keyword(s):  
Superoxide Dismutase ◽  
Peroxidase Activity ◽  
Oxidation Products ◽  
Superoxide Dismutase 1 ◽  
Amyloid Aggregation ◽  
Post Translational Modifications ◽  
Covalent Dimer ◽  
Als Patients ◽  
Lateral Sclerosis

The role of oxidative post-translational modifications of human superoxide dismutase 1 (hSOD1) in the amyotrophic lateral sclerosis (ALS) pathology is an attractive hypothesis to explore based on several lines of evidence. Among them, the remarkable stability of hSOD1WT and several of its ALS-associated mutants suggests that hSOD1 oxidation may precede its conversion to the unfolded and aggregated forms found in ALS patients. The bicarbonate-dependent peroxidase activity of hSOD1 causes oxidation of its own solvent-exposed Trp32 residue. The resulting products are apparently different from those produced in the absence of bicarbonate and are most likely specific for simian SOD1s, which contain the Trp32 residue. The aims of this work were to examine whether the bicarbonate-dependent peroxidase activity of hSOD1 (hSOD1WT and hSOD1G93A mutant) triggers aggregation of the enzyme and to comprehend the role of the Trp32 residue in the process. The results showed that Trp32 residues of both enzymes are oxidized to a similar extent to hSOD1-derived tryptophanyl radicals. These radicals decayed to hSOD1-N-formylkynurenine and hSOD1-kynurenine or to a hSOD1 covalent dimer cross-linked by a ditryptophan bond, causing hSOD1 unfolding, oligomerization, and non-amyloid aggregation. The latter process was inhibited by tempol, which recombines with the hSOD1-derived tryptophanyl radical, and did not occur in the absence of bicarbonate or with enzymes that lack the Trp32 residue (bovine SOD1 and hSOD1W32F mutant). The results support a role for the oxidation products of the hSOD1-Trp32 residue, particularly the covalent dimer, in triggering the non-amyloid aggregation of hSOD1.

Study of interaction and adsorption of aromatic amines by manganese oxides and their role in chemical evolution

2016 ◽  
Vol 16 (2) ◽  
pp. 143-155 ◽  
Author(s):  
Brij Bhushan ◽  
Arunima Nayak ◽  
Kamaluddin
Keyword(s):  
Aromatic Amines ◽  
Manganese Oxides ◽  
Oxidation Products ◽  
Gas Chromatography Mass Spectrometry ◽  
Spectroscopy Analysis ◽  
Electron Microscopic ◽  
Microscopic Studies ◽  
The Fourier Transform ◽  
Langmuir Constants

AbstractThe role of manganese oxides in concentrating organic moieties and offering catalytic activity for prebiotic reactions is investigated by studying their interaction with different aromatic amines such as aniline, p-chloroaniline, p-toluidine and p-anisidine. For all amines, metal oxides showed highest adsorption at neutral pH. The order of their adsorption capacity and affinity as revealed by the Langmuir constants was found to be manganosite (MnO) > bixbyite (Mn2O3) > hausmannite (Mn3O4) > and pyrolusite (MnO2). At alkaline pH, these manganese oxides offered their surfaces for oxidation of amines to form coloured oligomers. Analysis of the oxidation products by gas chromatography–mass spectrometry showed the formation of a dimer from p-anisidine and p-chloroaniline, while a trimer and tetramer is formed from p-toluidine and aniline, respectively. A reaction mechanism is proposed for the formation of the oligomers. While field-emission scanning electron microscopic studies confirm the binding phenomenon, the Fourier transform infrared spectroscopy analysis suggests that the mechanism of binding of amines on the manganese oxides was primarily electrostatic. The adsorption behaviour of the studied aromatic amines followed the order: p-anisidine > p-toluidine > aniline > p-chloroaniline, which is related to the basicities and structure of the amines. Our studies confirmed the significance of the role of manganese oxides in prebiotic chemistry.

The First Observation of HOx radicals in the Chengyu Urban Agglomeration

2020 ◽  
Author(s):  
Xinping Yang ◽  
Keding Lu ◽  
Xuefei Ma ◽  
Yuanhang Zhang
Keyword(s):  
New York ◽  
Urban Agglomeration ◽  
Oxidation Products ◽  
Oh Radicals ◽  
Secondary Pollution ◽  
Sensitivity Tests ◽  
Reaction Channels ◽  
Daily Concentration ◽  
Field Campaigns

<p>A comprehensive field campaign was carried out in summer 2019 in Chengdu, which obtained the first complete radical dataset of Chengyu Urban Agglomeration. Observed daily concentration maxima of radicals by the laser-induced-fluorescence (LIF) technique were in the range of (2-10)×10<sup>6</sup> cm<sup>-3</sup> for OH and (4-15)×10<sup>8</sup> cm<sup>-3</sup> for HO<sub>2</sub>. During daytime, OH reactivities were generally high (5-32 s<sup>-1</sup>). The missing reactivity was not be observed within uncertainty, and inorganics, observed VOCs and the calculated oxidation products contributed about one-third in total reactivity, respectively.</p><p>The chemical box model RACM 2 was used to interpret the observed radical concentrations. The model over-predicted OH and HO<sub>2</sub> at noon during the O<sub>3</sub> polluted episode. Constraining the model by the observed HO<sub>2</sub> concentration, the overestimation of OH can be explained almost by the overestimation of HO<sub>2</sub>. Besides, as in the previous field campaigns (e.g. Pennsylvania, Mexico City, New York and so on), the underestimation of the net conversion of OH into HO<sub>2</sub> enlarged with the increasing NO concentration, indicating the conversion of HO<sub>2</sub> into OH still need to be studied based on the discussion above. Different schemes to improve the agreement between observed and modelled HO<sub>2</sub> were explored in this work. The sensitivity tests indicated observed and modelled HO<sub>2</sub> can be agreed well by reducing the HO<sub>2</sub> yield in the reaction of OH and HCHO a half.</p><p>The oxidation rate of primary pollutants dominated by OH radicals was significantly higher than that in winter Beijing, which contributes significantly to secondary pollution, especially O<sub>3</sub>. Besides, the atmospheric self-cleaning ability and recycling efficiency both peaked for about 600 pptv of NO, indicating small amounts of NO can help to maintain the atmospheric oxidation. The campaign emphasizes the important role of HO<sub>2</sub> yield in the reaction channels of OH and VOCs especially, and the need for further laboratory experiments of the HO<sub>2</sub> yield measurement in order to understand radical chemistry in VOC-rich air.</p>

Antioxidant Properties of Carbon Black in Unsaturated Elastomers. Studies with cis-Polybutadiene

1965 ◽  
Vol 38 (3) ◽  
pp. 636-646
Author(s):  
J. T. Gruver ◽  
K. W. Rollmann
Keyword(s):  
Antioxidant Activity ◽  
Carbon Black ◽  
Antioxidant Properties ◽  
Chain Scission ◽  
Oxygen Absorption ◽  
Hydroxyl Groups ◽  
Carbon Blacks ◽  
Crosslinking Reactions ◽  
Absorption Measurements

Abstract The thermal antioxidant behavior of carbon black was studied in vulcanized cis-polybutadiene and related to the surface chemistry of the black. Continuous and intermittent stress relaxation and oxygen absorption measurements were employed to determine the antioxidant ability of the carbon blacks. The blacks were characterized by the surface concentrations of oxygen-containing functional groups, using methods described in the literature. Antioxidant activity was found to be highest in carbons containing relatively large amounts of bound oxygen. These carbons are also acidic and decompose peroxides by the ionic mechanism. This was demonstrated with cumyl peroxide. However, even though the acidity and ability to decompose cumyl peroxide to phenol and acetone could be destroyed by methylation, this treatment did not seriously impair the antioxidant activity, so that the role of acidic groups appears to be minor. Evidence is presented which suggests strongly that the antioxidant behavior of carbon blacks is due to surface quinones, possibly hydrogen-bonded with adjacent hydroxyl groups. Measurements made on samples vulcanized in peroxide and sulfur curing systems indicate that the antioxidant behavior of carbon black is independent of the method of vulcanization in the absence of other antioxidants. A characteristic feature of the antioxidant action of carbon blacks is their tendency to repress the oxidative crosslinking reactions, the relative amount of compensation of chain scission by crosslinking being smaller than in gum vulcanizates.

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