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International Journal of Molecular... Dec 2023Dinitrosyl iron complexes (DNICs) are important physiological derivatives of nitric oxide. These complexes have a wide range of biological activities, with antioxidant...
Dinitrosyl iron complexes (DNICs) are important physiological derivatives of nitric oxide. These complexes have a wide range of biological activities, with antioxidant and antiradical ones being of particular interest and importance. We studied the interaction between DNICs associated with the dipeptide L-carnosine or serum albumin and prooxidants under conditions mimicking oxidative stress. The ligands of these DNICs were histidine residues of carnosine or His39 and Cys34 in bovine serum albumin. Carnosine-bound DNICs reduced the level of piperazine free radicals in the reaction system containing -butyl hydroperoxide (-BOOH), bivalent iron ions, a nitroxyl anion donor (Angeli's salt), and HEPES buffer. The ability of carnosine DNICs to intercept organic free radicals produced from -BOOH decay could lead to this effect. In addition, carnosine DNICs reacted with the superoxide anion radical (O) formed in the xanthine/xanthine oxidase enzymatic system. They also reduced the oxoferryl form of the heme group formed in the reaction of myoglobin with -BOOH. DNICs associated with serum albumin were found to be rapidly destroyed in a model system containing metmyoglobin and t-BOOH. At the same time, these protein DNICs inhibited the -BOOH-induced oxidative degradation of coenzymes Q and Q in rat myocardial homogenate. The possible mechanisms of the antioxidant and antiradical action of the DNICs studied and their role in the metabolism of reactive oxygen and nitrogen species are discussed.
Topics: Rats; Animals; Antioxidants; Histidine; Carnosine; Nitrogen Oxides; Iron; Nitric Oxide; Free Radicals; Superoxides; Oxygen; Serum Albumin
PubMed: 38139065
DOI: 10.3390/ijms242417236 -
Molecules (Basel, Switzerland) Nov 2022Sterically shielded nitroxides, which demonstrate high resistance to bioreduction, are the spin labels of choice for structural studies inside living cells using pulsed...
Sterically shielded nitroxides, which demonstrate high resistance to bioreduction, are the spin labels of choice for structural studies inside living cells using pulsed EPR and functional MRI and EPRI in vivo. To prepare new sterically shielded nitroxides, a reaction of cyclic nitrones, including various 1-pyrroline-1-oxides, 2,5-dihydroimidazole-3-oxide and 4-imidazole-3-oxide with alkynylmagnesium bromide wereused. The reaction gave corresponding nitroxides with an alkynyl group adjacent to the N-O moiety. The hydrogenation of resulting 2-ethynyl-substituted nitroxides with subsequent re-oxidation of the N-OH group produced the corresponding sterically shielded tetraalkylnitroxides of pyrrolidine, imidazolidine and 2,5-dihydroimidazole series. EPR studies revealed large additional couplings up to 4 G in the spectra of pyrrolidine and imidazolidine nitroxides with substituents in 3- and/or 4-positions of the ring.
Topics: Bromides; Cyclic N-Oxides; Nitrogen Oxides; Spin Labels; Oxides; Pyrrolidines; Imidazolidines; Electron Spin Resonance Spectroscopy
PubMed: 36364453
DOI: 10.3390/molecules27217626 -
Angewandte Chemie (International Ed. in... May 2022Oxidase-type oxidation is an attractive strategy in organic synthesis due to the use of O as the terminal oxidant. Organic photocatalysis can effect metal-free oxidase...
Oxidase-type oxidation is an attractive strategy in organic synthesis due to the use of O as the terminal oxidant. Organic photocatalysis can effect metal-free oxidase chemistry. Nevertheless, current methods are limited in reaction scope, possibly due to the lack of suitable photocatalysts. Here we report an isoquinoline-derived diaryl ketone-type photocatalyst, which has much enhanced absorption of blue and visible light compared to conventional diaryl ketones. This photocatalyst enables dehydrogenative cross-coupling of heteroarenes with unactivated and activated alkanes as well as aldehydes using air as the oxidant. A wide range of heterocycles with various functional groups are suitable substrates. Transient absorption and excited-state quenching experiments point to an unconventional mechanism that involves an excited state "self-quenching" process to generate the N-radical cation form of the sensitizer, which subsequently abstracts a hydrogen atom from the alkane substrate to yield a reactive alkyl radical.
Topics: Alkanes; Catalysis; Hydrogen; Isoquinolines; Ketones; Oxidants; Oxidoreductases
PubMed: 35253971
DOI: 10.1002/anie.202202649 -
International Journal of Environmental... Jun 2022Electrochemical oxidation of landfill leachate after biological treatment by a novel electrochemical system, which was constructed by introducing a corroding electrode...
Electrochemical oxidation of landfill leachate after biological treatment by a novel electrochemical system, which was constructed by introducing a corroding electrode of iron (Fe) between a boron-doped diamond (BDD) anode and carbon felt (CF) cathode (named as BDD-Fe-CF), was investigated in the present study. Response surface methodology (RSM) with Box-Behnken (BBD) statistical experiment design was applied to optimize the experimental conditions. Effects of variables including current density, electrolytic time and pH on chemical oxygen demand (COD) and ammonia nitrogen (NH-N) removal efficiency were analyzed. Results showed that electrolytic time was more important than current density and pH for both COD and NH-N degradation. Based on analysis of variance (ANOVA) under the optimum conditions (current density of 25 mA·cm, electrolytic time of 9 h and pH of 11), the removal efficiencies for COD and NH-N were 81.3% and 99.8%, respectively. In the BDD-Fe-CF system, organic pollutants were oxidized by electrochemical and Fenton oxidation under acidic conditions. Under alkaline conditions, coagulation by Fe(OH) and oxidation by Fe(VI) have great contribution on organic compounds degradation. What is more, species of organic compounds before and after electrochemical treatment were analyzed by GC-MS, with 56 kinds components detected before treatment and only 16 kinds left after treatment. These results demonstrated that electrochemical oxidation by the BDD-Fe-CF system has great potential for the advanced treatment of landfill leachate.
Topics: Biological Oxygen Demand Analysis; Boron; Carbon; Diamond; Electrodes; Hydrogen Peroxide; Iron; Organic Chemicals; Oxidation-Reduction; Water Pollutants, Chemical
PubMed: 35805405
DOI: 10.3390/ijerph19137745 -
The Science of the Total Environment Feb 2021Lead is a toxic environmental contaminant associated with current and historic mine sites. Here we studied the natural attenuation of Pb in a limestone cave system that...
Lead is a toxic environmental contaminant associated with current and historic mine sites. Here we studied the natural attenuation of Pb in a limestone cave system that receives drainage from the ancient Priddy Mineries, UK. Extensive deposits of manganese oxides were observed to be forming on the cave walls and as coatings in the stream beds. Analysis of these deposits identified them as birnessite (δ-MnO), with some extremely high concentrations of sorbed Pb (up to 56 wt%) also present. We hypothesised that these cave crusts were actively being formed by microbial Mn(II)-oxidation, and to investigate this the microbial communities were characterised by DNA sequencing, enrichment and isolation experiments. The birnessite deposits contained abundant and diverse prokaryotes and fungi, with ~5% of prokaryotes and ~ 10% of fungi closely related to known heterotrophic Mn(II)-oxidisers. A substantial proportion (up to 17%) of prokaryote sequences were assigned to groups known as autotrophic ammonia and nitrite oxidisers, suggesting that nitrogen cycling may play an important role in contributing energy and carbon to the cave crust microbial communities and consequently the formation of Mn(IV) oxides and Pb attenuation. Enrichment and isolation experiments showed that the birnessite deposits contained Mn(II)-oxidising microorganisms, and two isolates (Streptomyces sp. and Phyllobacterium sp.) could oxidise Mn(II) in the presence of 0.1 mM Pb. Supplying the enrichment cultures with acetate as a source of energy and carbon stimulated Mn(II)-oxidation, but excess organics in the form of glucose generated aqueous Mn(II), likely via microbial Mn(IV)-reduction. In this karst cave, microbial Mn(II)-oxidation contributes to the active sequestration and natural attenuation of Pb from contaminated waters, and therefore may be considered a natural analogue for the design of wastewater remediation systems and for understanding the geochemical controls on karst groundwater quality, a resource relied upon by billions of people across the globe.
Topics: Groundwater; Humans; Lead; Manganese; Manganese Compounds; Oxidation-Reduction; Oxides
PubMed: 33254903
DOI: 10.1016/j.scitotenv.2020.142312 -
Chemosphere Apr 2022Bio-Fenton reaction supported by glucose oxidase (GOx) for producing HO was applied to degrade persistent chloroacetanilide herbicides in the presence of Fe...
Bio-Fenton reaction supported by glucose oxidase (GOx) for producing HO was applied to degrade persistent chloroacetanilide herbicides in the presence of Fe (Ⅲ)-citrate at pH 5.5. There were pH decrease to 4.3, the production of 8 mM HO and simultaneous consumption to produce •OH radicals which non-specifically degraded the herbicides. The degradation rates followed the order acetochlor ≈ alachlor ≈ metolachlor > propachlor ≈ butachlor with the degradation percent of 72.8%, 73.4%, 74.0%, 47.4%, and 43.8%, respectively. During the Bio-Fenton degradation, alachlor was dechlorinated and filtered into catechol via the production of intermediates formed through a series of hydrogen atom abstraction and hydrogen oxide radical addition reactions. The current Bio-Fenton reaction leading to the production of •OH radicals could be applied for non-specific oxidative degradation to various persistent organic pollutants under in-situ environmental conditions, considering diverse microbial metabolic systems able to continuously supply HO with ubiquitous Fe(II) and Fe(III) and citrate.
Topics: Acetamides; Ferric Compounds; Glucose Oxidase; Herbicides; Hydrogen Peroxide
PubMed: 34954194
DOI: 10.1016/j.chemosphere.2021.133417 -
Molecules (Basel, Switzerland) Mar 2022Ozone has been successfully employed in water treatment due to its ability to oxidize a wide variety of refractory compounds. In order to increase the process efficiency... (Review)
Review
Ozone has been successfully employed in water treatment due to its ability to oxidize a wide variety of refractory compounds. In order to increase the process efficiency and optimize its economy, the implementation of heterogeneous catalysts has been encouraged. In this context, the use of cheap and widely available natural materials is a promising option that would promote the utilization of ozone in a cost-effective water treatment process. This review describes the use of natural clays, zeolites and oxides as supports or active catalysts in the ozonation process, with emphasis on the structural characteristics and modifications performed in the raw natural materials; the catalytic oxidation mechanism; effect of the operating parameters and degradation efficiency outcomes. According to the information compiled, more research in realistic scenarios is needed (i.e., real wastewater matrix or continuous operation in pilot scale) in order to transfer this technology to the treatment of real wastewater streams.
Topics: Catalysis; Clay; Environmental Pollutants; Oxides; Ozone; Wastewater; Water Pollutants, Chemical; Water Purification; Zeolites
PubMed: 35408550
DOI: 10.3390/molecules27072151 -
Inorganic Chemistry May 2024One of the crucial metabolic processes for both plant and animal kingdoms is the oxidation of the amino acid tryptophan (TRP) that regulates plant growth and controls...
One of the crucial metabolic processes for both plant and animal kingdoms is the oxidation of the amino acid tryptophan (TRP) that regulates plant growth and controls hunger and sleeping patterns in animals. Here, we report revolutionary insights into how this process can be crucially affected by interactions with metal oxide nanoparticles (NPs), creating a toolbox for a plethora of important biomedical and agricultural applications. Molecular mechanisms in TRP-NP interactions were revealed by NMR and optical spectroscopy for ceria and titania and by X-ray single-crystal study and a computational study of model TRP-polyoxometalate complexes, which permitted the visualization of the oxidation mechanism at an atomic level. Nanozyme activity, involving concerted proton and electron transfer to the NP surface for oxides with a high oxidative potential, like CeO or WO, converted TRP in the first step into a tricyclic organic acid belonging to the family of natural plant hormones, auxins. TiO, a much poorer oxidant, was strongly binding TRP without concurrent oxidation in the dark but oxidized it nonspecifically via the release of reactive oxygen species (ROS) in daylight.
Topics: Cerium; Metal Nanoparticles; Models, Molecular; Oxidation-Reduction; Oxides; Titanium; Tryptophan
PubMed: 38684718
DOI: 10.1021/acs.inorgchem.3c03674 -
Environmental Science & Technology Nov 2015Biogeochemical transformations of plant-derived soil organic matter (SOM) involve complex abiotic and microbially mediated reactions. One such reaction is halogenation,...
Biogeochemical transformations of plant-derived soil organic matter (SOM) involve complex abiotic and microbially mediated reactions. One such reaction is halogenation, which occurs naturally in the soil environment and has been associated with enzymatic activity of decomposer organisms. Building on a recent finding that naturally produced organobromine is ubiquitous in SOM, we hypothesized that inorganic bromide could be subject to abiotic oxidations resulting in bromination of SOM. Through lab-based degradation treatments of plant material and soil humus, we have shown that abiotic bromination of particulate organic matter occurs in the presence of a range of inorganic oxidants, including hydrogen peroxide and assorted forms of ferric iron, producing both aliphatic and aromatic forms of organobromine. Bromination of oak and pine litter is limited primarily by bromide concentration. Fresh plant material is more susceptible to bromination than decayed litter and soil humus, due to a labile pool of mainly aliphatic compounds that break down during early stages of SOM formation. As the first evidence of abiotic bromination of particulate SOM, this study identifies a mechanistic source of the natural organobromine in humic substances and the soil organic horizon. Formation of organobromine through oxidative treatments of plant material also provides insights into the relative stability of aromatic and aliphatic components of SOM.
Topics: Bromides; Forests; Halogenation; Humic Substances; Hydrogen Peroxide; Hydrogen-Ion Concentration; Iron; Light; New Jersey; Oxidation-Reduction; Pinus; Quercus; Soil; Soil Microbiology; X-Ray Absorption Spectroscopy
PubMed: 26468620
DOI: 10.1021/acs.est.5b03937 -
Molecules (Basel, Switzerland) Dec 2022The use of clays as adsorbents and catalysts in the ozonation of organic pollutants (Atrazine, bis-Phenol A, Diazinon, and Diclofenac sodium) allowed simulating their...
The use of clays as adsorbents and catalysts in the ozonation of organic pollutants (Atrazine, bis-Phenol A, Diazinon, and Diclofenac sodium) allowed simulating their natural oxidative degradation in clay soils and to evaluate the ecotoxicity of mixtures partially oxidized on the species , a biodiversity representative of plants in the aquatic environment. Kinetic data showed that the adsorption of organic pollutants on clay particles obeys the pseudo-second-order model, while the adsorption isotherms satisfactorily fit the Langmuir model. Adsorption reduces the dispersion of the organic pollutant in the environment and prolongs its persistence and its natural degradation probability. Measurements of the Zeta potential and particle size as a function of pH demonstrate that the catalytic activity of clay depends on its cation, its silica/alumina ratio, and therefore on its permanent and temporary ion exchange capacities. These factors seem to govern its delamination and dispersion in aqueous media, its hydrophilic-hydrophobic character, and its porosity. Tests conducted on in contact with ozonation mixtures revealed that the toxicity could be due to pH decrease and to the toxicity of the intermediates yielded. Ecotoxicity would depend on the structure of the organic molecules, the chemical composition of the clay surface and ozonation time, which determines the oxidation progress. These results are of great importance for further research because they allow concluding that the negative impact of the persistence of an organic molecule in clay-containing media depends on the type and composition of the very clay mineral.
Topics: Clay; Aluminum Silicates; Environmental Pollutants; Water; Molecular Structure; Catalysis; Ozone; Adsorption; Water Pollutants, Chemical; Bentonite
PubMed: 36615416
DOI: 10.3390/molecules28010222