[1] Chemistry of dioxygen
Publisher Summary
The chemistry of molecular oxygen, or dioxygen as it is increasingly coming to be called, is dominated by the relative reluctance with which the element reacts with most, but not all, compounds. This quality is rarely thermodynamic in origin; rather the slow rate of reaction is associated with either the strong oxygen–oxygen bond or the character of the ground state of dioxygen or both. If a reaction is to take place with dioxygen in its ground state, there must be a change of spin at some stage during the reaction. This is forbidden, within the limitations of the descriptions used; at the very least, the reactions are improbable. For dioxygen to react rapidly, this spin restriction should be removed or the oxygen–oxygen bond should be partially weakened or both of these should occur simultaneously. It is not surprising that much of the chemistry of dioxygen is concerned with reactions with paramagnetic species, with electron-donating species, with light, or with various combinations of these three factors. This chapter discusses the chemistry of the reduction products of dioxygen, but one should be aware of the marked influence of all of these factors on most reactions of dioxygen. They are often, if not always, responsible for the promotion or catalysis of oxidation reactions.
References (16)
- B. Halliwell
FEBS. Lett.
(1978) - M.R. Green et al.
FEBS. Lett.
(1979) - J.M. McCord et al.
J. Biol. Chem.
(1969) - A. Azzi et al.
Biochem. Biophys. Res. Commun.
(1975) - C. Auclair et al.
FEBS. Lett.
(1978) - R.L. Arudi et al.
FEBS. Lett.
(1981) - W.A. Pryor et al.
Biochem. Biophys. Res. Commun.
(1978) - R. Richmond et al.
Anal. Biochem.
(1981)
Cited by (215)
Chemical background of silver nanoparticles interfering with mammalian copper metabolism
2023, Journal of Hazardous MaterialsThe rapidly increasing application of silver nanoparticles (AgNPs) boosts their release into the environment, which raises a reasonable alarm for ecologists and health specialists. This is manifested as increased research devoted to the influence of AgNPs on physiological and cellular processes in various model systems, including mammals. The topic of the present paper is the ability of silver to interfere with copper metabolism, the potential health effects of this interference, and the danger of low silver concentrations to humans. The chemical properties of ionic and nanoparticle silver, supporting the possibility of silver release by AgNPs in extracellular and intracellular compartments of mammals, are discussed. The possibility of justified use of silver for the treatment of some severe diseases, including tumors and viral infections, based on the specific molecular mechanisms of the decrease in copper status by silver ions released from AgNPs is also discussed.
The tobacco cutworm, Spodoptera litura (Fabricius) is a serious cosmopolitan pest that attacks several economically important crops such as maize, sorghum, chickpea, pigeon pea, cotton, tobacco and sunflower. It has developed resistance to most pesticides resulting in its continual outbreak. The effect of caffeic acid on second instar larvae of S. litura was evaluated by carrying out bioassays, nutritional assays, immune assays and biochemical assays with phenolic acids. Bioassays carried out with second instar larvae of S. litura showed growth inhibiting effects of various concentrations (5 ppm, 25 ppm, 125 ppm, 625 ppm and 3125 ppm) of caffeic acid on S. litura in comparison to control. A significant increase in mortality as well as an increased development time was observed with increase in the concentration of caffeic acid. A decrease in nutritional indices, including relative growth rate (RGR), relative consumption rate (RCR), efficiency of conversion of ingested food (ECI), efficiency of conversion of digested food (ECD), and approximate digestibility (AD), indicated that dietary caffeic acid also negatively impacted the nutritional physiology of S. litura larvae. Caffeic acid has a significant impact on the immunological response of S. litura larvae. As the concentration of caffeic acid increased, the overall number of hemocytes decreased. Enzymatic assays revealed a significant increase in antioxidant enzymes when S. litura larvae were given an artificial diet containing LC50 concentration of phenolic acid for an interval of 24, 48, 72 and 96 h. The levels of oxidative stress markers (hydrogen peroxide, protein carbonyl and lipid peroxide) were also significantly enhanced in S. litura larvae after treatment with phenolic acid. According to our study, caffeic acid can be employed as a substitute for traditional insecticides to reduce the population of S. litura.
Effect of daidzein on growth, development and biochemical physiology of insect pest, Spodoptera litura (Fabricius)
2022, Comparative Biochemistry and Physiology Part - C: Toxicology and PharmacologyAnti- insecticidal potential of daidzein was studied by feeding second instar larvae of Spodoptera litura (Fabricius) on artificial diet incorporated with different concentrations (5 ppm, 25 ppm, 125 ppm, 625 ppm) of diadzein. Results revealed high larval mortality, prolongation of pupal and total developmental period of the larvae treated with diadzein. Anti-nutritional/post ingestive toxicity of diadzein was also revealed by the decrease in the nutritional indices such as relative growth rate (RGR), relative consumption rate (RCR), efficiency of conversion of digested food (ECD), efficiency of conversion of ingested food (ECI) and approximate digestibility (AD). The suppression of immune function due to decline in the total hemocytes count was also observed in treated S. litura larvae. Profiles of detoxifying enzymes viz. superoxide dismutases (SOD), catalase (CAT), ascorbate peroxidases (APOX) and glutathione S-transferase (GST) were also significantly increased with diadzein treatment. The hydrogen peroxide content (H2O2), lipid peroxide content (LP) and protein carbonyl content were also significantly enhanced in the treated larvae thus, indicating oxidative stress in the insect. Our findings suggest that daidzein can be used as the alternative to conventional pesticides for controlling S. litura population.
Oviposition behaviour and biochemical response of an insect pest, Zeugodacus cucurbitae (Coquillett) (Diptera: Tephritidae) to plant phenolic compound phloroglucinol
2022, Comparative Biochemistry and Physiology Part - C: Toxicology and PharmacologyPhenolic compounds are the secondary metabolites (SMs) present in plants carrying different bioactivities. In the present study, we explored the influence of a phenolic compound namely phloroglucinol on oviposition behaviour and different biochemical entities of an insect pest Zeugodacus cucurbitae (Coquillett) (Diptera: Tephritidae) using artificial diet. Phloroglucinol (IUPAC name: benzene-1,3,5-triol) affected the activity of antioxidant and detoxifying enzymes viz. superoxide dismutases (SOD), catalase (CAT), ascorbate peroxidases (APOX). dehydroascorbate reductase (DHAR), peroxidases (POX), phenol oxidase (PO), glutathione peroxidase (GPOX), glutathione S-transferase peroxidase (GSTpox), glutathione reductase (GR), glutathione S-transferase (GST) and esterases (EST) as well as the biological antioxidants viz. ascorbate content and glutathione. The lipid peroxide content (LP) and hydrogen peroxide content (H2O2) were significantly enhanced in the treated larvae indicating oxidative stress in the insect. Significant inhibition in oviposition was observed and effective repellency percentage increased with phloroglucinol treatment as compared to control. The oviposition deterrent activity and toxic effects of phloroglucinol on various biochemical parameters of Z. cucurbitae larvae revealed in the present study clearly confirms its suitability for use in pest management.
Thiol- and selenol-based peroxidases: Structure and catalytic properties
2022, Redox Chemistry and Biology of ThiolsThe three families of thiol- or selenol-based peroxidases (peroxiredoxins, Prx; glutathione peroxidases, GPx; and organic hydroperoxide resistance protein/osmotically inducible protein C, Ohr/OsmC) catalyze the reduction of hydroperoxides at the expense of thiol-containing compounds. In Prx, Ohr/OsmC, and some GPx, the catalysis involves a peroxidatic cysteine, while in other GPx, a selenocysteine. Their specificities for reducing and oxidizing substrates are distinct and may reflect their physiological roles. Prx and GPx share the thioredoxin fold common to the proteins belonging to the thioredoxin superfamily. In contrast, Ohr/OsmC present a unique barrel shape α/β fold. Some Prx change their oligomeric state under different conditions, including protein redox state, which is associated with a chaperone function. Ohr/OsmC are dimers and GPx can be monomeric or tetrameric, irrespective of their oxidation state. The mechanisms behind the extraordinary catalytic efficiency of these enzymes in the reduction of hydroperoxides are discussed.
Concanavalin A-Rose Bengal bioconjugate for targeted Gram-negative antimicrobial photodynamic therapy
2020, Journal of Photochemistry and Photobiology B: BiologyPhotodynamic therapy (PDT) is considered a very promising therapeutic modality for antimicrobial therapy. Although several studies have demonstrated that Gram-positive bacteria are very sensitive to PDT, Gram-negative bacteria are more resistant to photodynamic action. This difference is due to a different cell wall structure. Gram-negative bacteria have an outer cell membrane containing lipopolysaccharides (LPS) that hinder the binding of photosensitizer molecules, protecting the bacterial cells from chemical attacks. Combination of the lipopolysaccharides-binding activity of Concanavalin A (ConA) with the photodynamic properties of Rose Bengal (RB) holds the potential of an innovative protein platform for targeted photodynamic therapy against Gram-negative bacteria. A ConA-RB bioconjugate was synthesized and characterized. Approximately 2.4 RB molecules were conjugated per ConA monomer. The conjugation of RB to ConA determines a decrease of the singlet oxygen generation and an increase of superoxide and peroxide production. The photokilling efficacy of the ConA-RB bioconjugate was demonstrated in a planktonic culture of E. coli. Irradiation with white light from a LED lamp produced a dose-dependent photokilling of bacteria. ConA-RB conjugates exhibited a consistent improvement over RB (up to 117-fold). The improved uptake of the photosensitizer explains the enhanced PDT effect accompanying increased membrane damages induced by the ConA-RB conjugate. The approach can be readily generalized (i) using different photo/sonosensitizers, (ii) to target other pathogens characterized by cell membranes containing lipopolysaccharides (LPS).