Segui questo link per vedere altri tipi di pubblicazioni sul tema: Peroxides.
Articoli di riviste sul tema "Peroxides"
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Vedi i top-50 articoli di riviste per l'attività di ricerca sul tema "Peroxides".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Vedi gli articoli di riviste di molte aree scientifiche e compila una bibliografia corretta.
1
Zhao, Rong, Denghu Chang e Lei Shi. "Recent Advances in Cyclic Diacyl Peroxides: Reactivity and Selectivity Enhancement Brought by the Cyclic Structure". Synthesis 49, n. 15 (12 giugno 2017): 3357–65. http://dx.doi.org/10.1055/s-0036-1588458.
Testo completoAbstract (sommario):
Preliminarily studies on cyclic diacyl peroxides have shown novel and superior reactivities compared with their acyclic diacyl peroxide counterparts in many reaction types. After summarizing the methods available for the preparation of cyclic diacyl peroxides and describing their structural features, this review brings together an overview of their reactivities with respect to oxidations and decarboxylations, and demonstrates the advantages of reactions with cyclic diacyl peroxides, which include metal-free, additive-free, milder conditions, higher yields and better selectivities.1 Introduction2 Methods of Preparation of Cyclic Diacyl Peroxides3 Structures and Stabilities of Cyclic Diacyl Peroxides4 Oxidation Reactions4.1 Oxidative Additions to Alkenes4.2 Oxidation Reactions of Heteroatoms4.3 Oxidation Reactions of 1,3-Dicarbonyl Compounds4.4 Hydroxylations of Arenes5 Decarboxylations6 Conclusion
2
Lubeigt, X., F. Flies, M. J. Bourgeois, E. Montaudon e B. Maillard. "Déplacements homolytiques intramoléculaires. 19. Stéréochimie de la décomposition induite de peroxydes insaturés conduisant à la formation d'hétérocycles à trois et quatre chaînons". Canadian Journal of Chemistry 69, n. 8 (1 agosto 1991): 1320–25. http://dx.doi.org/10.1139/v91-196.
Testo completoAbstract (sommario):
Homolytic decomposition induced by addition of dichloromethyl radicals to β- and γ-unsaturated peroxides having a substituent on the chain linking the unsaturation and the peroxide function was studied. The stereochemistry of the heterocycles produced was determined by I3C NMR and the stereoselectivity of intramolecular homolytic substitution on the peroxidic bond discussed. Key words: unsaturated peroxides, homolytic intramolecular substitutions, radical additions, oxygenated heterocycles.
3
Ajima, A., SG Cao, K. Takahashi, A. Matsushima, Y. Saito e Y. Inada. "An attempt to determine lipid peroxides with polyethylene glycol‐modified hemin". Biotechnology and Applied Biochemistry 9, n. 1 (febbraio 1987): 53–57. http://dx.doi.org/10.1111/j.1470-8744.1987.tb00462.x.
Testo completoAbstract (sommario):
Hemin, having two carboxyl groups, was coupled with alpha‐(3‐aminopropyl)‐omega‐methoxypoly(oxyethylene) through the acid‐amide bond formed with carbodiimide. The modified hemin catalyzed the peroxidase reaction in 1,1,1‐trichloroethane using benzoyl peroxide or peroxides in unsaturated fatty acids as the hydrogen acceptor and leuco crystal violet as the hydrogen donor. A basic study on quantitative microanalysis of the lipid peroxides was attempted.
4
Veal, Elizabeth A., Lewis E. Tomalin, Brian A. Morgan e Alison M. Day. "The fission yeast Schizosaccharomyces pombe as a model to understand how peroxiredoxins influence cell responses to hydrogen peroxide". Biochemical Society Transactions 42, n. 4 (1 agosto 2014): 909–16. http://dx.doi.org/10.1042/bst20140059.
Testo completoAbstract (sommario):
As a more selectively reactive oxygen species, H2O2 (hydrogen peroxide) has been co-opted as a signalling molecule, but high levels can still lead to lethal amounts of cell damage. 2-Cys Prxs (peroxiredoxins) are ubiquitous thioredoxin peroxidases which utilize reversibly oxidized catalytic cysteine residues to reduce peroxides. As such, Prxs potentially make an important contribution to the repertoire of cell defences against oxidative damage. Although the abundance of eukaryotic 2-Cys Prxs suggests an important role in maintaining cell redox, the surprising sensitivity of their thioredoxin peroxidase activity to inactivation by H2O2 has raised questions as to their role as an oxidative stress defence. Indeed, work in model yeast has led the way in revealing that Prxs do much more than simply remove peroxides and have even uncovered circumstances where their thioredoxin peroxidase activity is detrimental. In the present paper, we focus on what we have learned from studies in the fission yeast Schizosaccharomyces pombe about the different roles of 2-Cys Prxs in responses to H2O2 and discuss the general implications of these findings for other systems.
5
Missall, Tricia A., Jocie F. Cherry-Harris e Jennifer K. Lodge. "Two glutathione peroxidases in the fungal pathogen Cryptococcus neoformans are expressed in the presence of specific substrates". Microbiology 151, n. 8 (1 agosto 2005): 2573–81. http://dx.doi.org/10.1099/mic.0.28132-0.
Testo completoAbstract (sommario):
Glutathione peroxidases catalyse the reduction of peroxides by reduced glutathione. To determine if these enzymes are important for resistance to oxidative stress and evasion of the innate immune system by the fungal pathogen Cryptococcus neoformans, two glutathione peroxidase homologues, which share 38 % identity, were identified and investigated. In this study, these peroxidases, Gpx1 and Gpx2, their localization, their contribution to total glutathione peroxidase activity, and their importance to the oxidative and nitrosative stress resistance of C. neoformans are described. It is shown that the two glutathione peroxidase genes are differentially expressed in response to stress. While both GPX1 and GPX2 are induced during t-butylhydroperoxide or cumene hydroperoxide stress and repressed during nitric oxide stress, only GPX2 is induced in response to hydrogen peroxide stress. Deletion mutants of each and both of the glutathione peroxidases were generated, and it was found that they are sensitive to various peroxide stresses while showing wild-type resistance to other oxidant stresses, such as superoxide and nitric oxide. While the glutathione peroxidase mutants are slightly sensitive to oxidant killing by macrophages, they exhibit wild-type virulence in a mouse model of cryptococcosis.
6
Gutowicz, Marzena. "Antioxidant and detoxycative mechanisms in central nervous system". Postępy Higieny i Medycyny Doświadczalnej 74 (19 febbraio 2020): 1–11. http://dx.doi.org/10.5604/01.3001.0013.8548.
Testo completoAbstract (sommario):
Since the brain contains a large amount of polyunsaturated fatty acids, consumes up to 20% of oxygen used by the whole body and exhibits low antioxidants activity, it seems to be especially vulnerable to oxidative stress. The most important antioxidant enzymes are superoxide dismutase (SOD), which catalyze the dismutation of superoxide anion to hydrogen peroxide, catalase (CAT), which converts toxic hydrogen peroxide to water and oxygen, and glutathione peroxidase (Se-GSHPx), which reduces hydrogen peroxide and organic peroxides with glutathione as the cofactor. Among other detoxifying enzymes, the most significant is glutathione transferase (GST), which shows detoksyvarious catalytic activities allowing for removal of xenobiotics, reducing organic peroxides and oxidized cell components. One of the most important brain nonenzymatic antioxidants is reduced glutathione (GSH), which (individually or in cooperation with peroxidases) participates in the reduction of free radicals, repair of oxidative damage and the regeneration of other antioxidants, such as ascorbate or tocopherol. Glutathione as a cosubstrate of glutathione transferase scavenges toxic electrophilic compounds. Although the etiology of the major neurodegenerative diseases are unknown, numerous data suggest that reactive oxygen species play an important role. Even a small change in the level of antioxidants can leads to the many disorders in the CNS.
7
Iturbe-Ormaetxe, Iñaki, Manuel A. Matamoros, Maria C. Rubio, David A. Dalton e Manuel Becana. "The Antioxidants of Legume Nodule Mitochondria". Molecular Plant-Microbe Interactions® 14, n. 10 (ottobre 2001): 1189–96. http://dx.doi.org/10.1094/mpmi.2001.14.10.1189.
Testo completoAbstract (sommario):
The mitochondria of legume root nodules are critical to sustain the energy-intensive process of nitrogen fixation. They also generate reactive oxygen species at high rates and thus require the protection of antioxidant enzymes and metabolites. We show here that highly purified mitochondria from bean nodules (Phaseolus vulgaris L. cv. Contender × Rhizobium leguminosarum bv. phaseoli strain 3622) contain ascorbate peroxidase primarily in the inner membrane (with lesser amounts detected occasionally in the matrix), guaiacol peroxidases in the outer membrane and matrix, and manganese superoxide dismutase (MnSOD) and an ascorbate-regenerating system in the matrix. This regenerating system relies on homoglutathione (instead of glutathione) and pyridine nucleotides as electron donors and involves the enzymes monodehy-droascorbate reductase, dehydroascorbate reductase, and homoglutathione reductase. Homoglutathione is synthesized in the cytosol and taken up by the mitochondria and bacteroids. Although bacteroids synthesize glutathione, it is not exported to the plant in significant amounts. We propose a model for the detoxification of peroxides in nodule mitochondria in which membrane-bound ascorbate peroxidase scavenges the peroxide formed by the electron transport chain using ascorbate provided by L-galactono-1,4-lactone dehydrogenase in the inner membrane. The resulting monodehydroascorbate and dehydroascorbate can be recycled in the matrix or cytosol. In the matrix, the peroxides formed by oxidative reactions and by MnSOD may be scavenged by specific isozymes of guaiacol peroxidase, ascorbate peroxidase, and catalase.
8
Naskar, Kinsuk, e Jacques W. M. Noordermeer. "Dynamically Vulcanized PP/EPDM Blends: Multifunctional Peroxides as Crosslinking Agents — Part I". Rubber Chemistry and Technology 77, n. 5 (1 novembre 2004): 955–71. http://dx.doi.org/10.5254/1.3547862.
Testo completoAbstract (sommario):
Abstract Thermoplastic vulcanizates (TPVs) or dynamic vulcanizates are a special class of thermoplastic elastomers, produced by mixing and crosslinking of a rubber and a thermoplastic polymer simultaneously. In a previous study, it was demonstrated that the use of dicumyl peroxide in combination with triallyl cyanurate as crosslinking agents provides a good overall balance of physical properties of PP/EPDM TPVs. Commonly used peroxides like dicumyl peroxide generally produce volatile decomposition products, which sometimes provide a typical smell or show a blooming effect. In this paper multifunctional peroxides are described, which reduce the above-mentioned problems. They consist of a peroxide and co-agent-functionality combined in a single molecule. The multifunctional peroxides provide properties of TPVs, which are comparable with commonly employed co-agent assisted peroxides. The solubility and kinetic aspects of the various peroxides are highlighted, as well as the decomposition products of the multifunctional peroxides with respect to the avoidance of smelly by-products. Particularly, 2,4-diallyoxy-6-tert-butylperoxy-1,3,5-triazine turns out to be a very good alternative to the dicumyl peroxide/triallyl cyanurate combination.
9
Brenot, Audrey, Katherine Y. King, Blythe Janowiak, Owen Griffith e Michael G. Caparon. "Contribution of Glutathione Peroxidase to the Virulence of Streptococcus pyogenes". Infection and Immunity 72, n. 1 (gennaio 2004): 408–13. http://dx.doi.org/10.1128/iai.72.1.408-413.2004.
Testo completoAbstract (sommario):
ABSTRACT Glutathione peroxidases are widespread among eukaryotic organisms and function as a major defense against hydrogen peroxide and organic peroxides. However, glutathione peroxidases are not well studied among prokaryotic organisms and have not previously been shown to promote bacterial virulence. Recently, a gene with homology to glutathione peroxidase was shown to contribute to the antioxidant defenses of Streptococcus pyogenes (group A streptococcus). Since this bacterium causes numerous suppurative diseases that require it to thrive in highly inflamed tissue, it was of interest to determine if glutathione peroxidase is important for virulence. In this study, we report that GpoA glutathione peroxidase is the major glutathione peroxidase in S. pyogenes and is essential for S. pyogenes pathogenesis in several murine models that mimic different aspects of streptococcal suppurative disease. In contrast, glutathione peroxidase is not essential for virulence in a zebrafish model of streptococcal myositis, a disease characterized by the absence of an inflammatory cell infiltrate. Taken together, these data suggest that S. pyogenes requires glutathione peroxidase to adapt to oxidative stress that accompanies an inflammatory response, and the data provide the first demonstration of a role for glutathione peroxidase in bacterial virulence. The fact that genes encoding putative glutathione peroxidases are found in the genomes of many pathogenic bacterial species suggests that glutathione peroxidase may have a general role in bacterial pathogenesis.
10
Fleychuk, Roman, Lidiya Vuytsyk, Ananiy Kohut e Orest Hevus. "Synthesis of Epoxyperoxides and Peroxide Derivatives of -D-Galactopyranose Based Thereon". Chemistry & Chemical Technology 14, n. 4 (15 dicembre 2020): 439–47. http://dx.doi.org/10.23939/chcht14.04.439.
Testo completoAbstract (sommario):
New epoxide-containing peroxides have been synthesized via the interaction between epichlorohydrin and ditertiary -hydroxyalkyl peroxides. The effect of reaction conditions on both the yield and composition of the reaction products has been established. Through the reactions of either the synthesized epoxide-containing peroxides with 1,2;3,4-di-O-isopropylidene--D-galactopyranose or 6-O-glycidyl-1,2;3,4-di-O-isopropylidene--D-galactopyranose with the -hydroxyalkyl peroxides, new peroxide derivatives with ditertiary and primary-tertiary peroxide groups have been synthesized successfully. The decomposition of the developed substances has been studied by complex thermal analysis and the kinetic parameters of the thermolysis have been determined.
11
Mertes, P., L. Pfaffenberger, J. Dommen, M. Kalberer e U. Baltensperger. "Development of a sensitive long pathlength absorbance photometer to quantify peroxides in aerosol particles (Peroxide-LOPAP)". Atmospheric Measurement Techniques Discussions 5, n. 1 (13 febbraio 2012): 1431–57. http://dx.doi.org/10.5194/amtd-5-1431-2012.
Testo completoAbstract (sommario):
Abstract. A new off-line instrument to quantify peroxides in aerosol particles using iodometry in long pathlength absorption spectroscopy has been developed and is called peroxide long pathlength absorbance photometer (Peroxide-LOPAP). The new analytical setup features important technical innovations compared to hitherto published iodometric peroxide measurements. Firstly, the extraction, chemical conversion and measurement of the aerosol samples are performed in a closed oxygen-free (∼1 ppb) environment. Secondly, a 50-cm optical detection cell is used for an increased photometric sensitivity. The limit of detection was 0.1 μM peroxide in solution or 0.25 nmol m−3 with respect to an aerosol sample volume of 1000 l. The test reaction was done at a constant elevated temperature of 40 °C and the reaction time was 60 min. Calibration experiments showed that the test reaction with all reactive peroxides, i.e. hydrogen peroxide (H2O2), peracids and peroxides with vicinal carbonyl groups (e.g. lauroyl peroxide) goes to completion and their sensitivity (slope of calibration curve) varies by only ±5%. However, very stable peroxides have a lower sensitivity. For example tert-butyl hydroperoxide shows only 37% sensitivity compared to H2O2 after 1h. A kinetic study revealed that even after 5 h only 85% of this stable compound had reacted. The time trends of the peroxide content in secondary organic aerosol (SOA) from the ozonolysis and photo-oxidation of α-pinene in smog chamber experiments were measured. The highest amount of peroxides with 34% (assuming a MW of 300 g mol−1) was found in freshly generated SOA from α-pinene ozonolysis. Contents decreased with increasing NO levels in the photo-oxidation experiments. A decrease of the peroxide content was observed with aging of the aerosol indicating a decomposition of peroxides in the particles.
12
Mertes, P., L. Pfaffenberger, J. Dommen, M. Kalberer e U. Baltensperger. "Development of a sensitive long path absorption photometer to quantify peroxides in aerosol particles (Peroxide-LOPAP)". Atmospheric Measurement Techniques 5, n. 10 (2 ottobre 2012): 2339–48. http://dx.doi.org/10.5194/amt-5-2339-2012.
Testo completoAbstract (sommario):
Abstract. A new off-line instrument to quantify peroxides in aerosol particles using iodometry in long path absorption spectroscopy has been developed and is called peroxide long path absorption photometer (Peroxide-LOPAP). The new analytical setup features important technical innovations compared to hitherto published iodometric peroxide measurements. Firstly, the extraction, chemical conversion and measurement of the aerosol samples are performed in a closed oxygen-free (~ 1 ppb) environment. Secondly, a 50-cm optical detection cell is used for an increased photometric sensitivity. The limit of detection was 0.1 μM peroxide in solution or 0.25 nmol m−3 with respect to an aerosol sample volume of 1 m3. The test reaction was done at a constant elevated temperature of 40 °C and the reaction time was 60 min. Calibration experiments showed that the test reaction with all reactive peroxides, i.e. hydrogen peroxide (H2O2), peracids and peroxides with vicinal carbonyl groups (e.g. lauroyl peroxide) goes to completion and their sensitivity (slope of calibration curve) varies by only ±5%. However, very inert peroxides have a lower sensitivity. For example, tert-butyl hydroperoxide shows only 37% sensitivity compared to H2O2 after 1 h. A kinetic study revealed that even after 5 h only 85% of this inert compound had reacted. The time trends of the peroxide content in secondary organic aerosol (SOA) from the ozonolysis and photo-oxidation of α-pinene in smog chamber experiments were measured. The highest mass fraction of peroxides with 34% (assuming a molecular weight of 300 g mol−1) was found in freshly generated SOA from α-pinene ozonolysis. Mass fractions decreased with increasing NO levels in the photo-oxidation experiments. A decrease of the peroxide content was also observed with aging of the aerosol, indicating a decomposition of peroxides in the particles.
13
Broden, Nicole J., Sarah Flury, Alyssa N. King, Braden W. Schroeder, Gabrielle Dierker Coe e Melinda J. Faulkner. "Insights into the Function of a Second, Nonclassical Ahp Peroxidase, AhpA, in Oxidative Stress Resistance in Bacillus subtilis". Journal of Bacteriology 198, n. 7 (19 gennaio 2016): 1044–57. http://dx.doi.org/10.1128/jb.00679-15.
Testo completoAbstract (sommario):
ABSTRACTOrganisms growing aerobically generate reactive oxygen-containing molecules, such as hydrogen peroxide (H2O2). These reactive oxygen molecules damage enzymes and DNA and may even cause cell death. In response,Bacillus subtilisproduces at least nine potential peroxide-scavenging enzymes, two of which appear to be the primary enzymes responsible for detoxifying peroxides during vegetative growth: a catalase (encoded bykatA) and an alkylhydroperoxide reductase (Ahp, encoded byahpC). AhpC uses two redox-active cysteine residues to reduce peroxides to nontoxic molecules. A specialized thioredoxin-like protein, AhpF, is then required to restore oxidized AhpC back to its reduced state. Curiously,B. subtilishas two genes encoding Ahp:ahpCandahpA. Although AhpC is well characterized, very little is known about AhpA. In fact, numerous bacterial species have multipleahpgenes; however, these additional Ahp proteins are generally uncharacterized. We seek to understand the role of AhpA in the bacterium's defense against toxic peroxide molecules in relation to the roles previously assigned to AhpC and catalase. Our results demonstrate that AhpA has catalytic activity similar to that of the primary enzyme, AhpC. Furthermore, our results suggest that a unique thioredoxin redox protein, AhpT, may reduce AhpA upon its oxidation by peroxides. However, unlike AhpC, which is expressed well during vegetative growth, our results suggest that AhpA is expressed primarily during postexponential growth.IMPORTANCEB. subtilisappears to produce nine enzymes designed to protect cells against peroxides; two belong to the Ahp class of peroxidases. These studies provide an initial characterization of one of these Ahp homologs and demonstrate that the two Ahp enzymes are not simply replicates of each other, suggesting that they instead are expressed at different times during growth of the cells. These results highlight the need to further study the Ahp homologs to better understand how they differ from one another and to identify their function, if any, in protection against oxidative stress. Through these studies, we may better understand why bacteria have multiple enzymes designed to scavenge peroxides and thus have a more accurate understanding of oxidative stress resistance.
14
Clark, Donald E. "Peroxides and peroxide-forming compounds". Chemical Health and Safety 8, n. 5 (settembre 2001): 12–22. http://dx.doi.org/10.1016/s1074-9098(01)00247-7.
Testo completo
15
Wang, Yin, Zhongming Chen, Qinqin Wu, Hao Liang, Liubin Huang, Huan Li, Keding Lu et al. "Observation of atmospheric peroxides during Wangdu Campaign 2014 at a rural site in the North China Plain". Atmospheric Chemistry and Physics 16, n. 17 (6 settembre 2016): 10985–1000. http://dx.doi.org/10.5194/acp-16-10985-2016.
Testo completoAbstract (sommario):
Abstract. Measurements of atmospheric peroxides were made during Wangdu Campaign 2014 at Wangdu, a rural site in the North China Plain (NCP) in summer 2014. The predominant peroxides were detected to be hydrogen peroxide (H2O2), methyl hydroperoxide (MHP) and peroxyacetic acid (PAA). The observed H2O2 reached up to 11.3 ppbv, which was the highest value compared with previous observations in China at summer time. A box model simulation based on the Master Chemical Mechanism and constrained by the simultaneous observations of physical parameters and chemical species was performed to explore the chemical budget of atmospheric peroxides. Photochemical oxidation of alkenes was found to be the major secondary formation pathway of atmospheric peroxides, while contributions from alkanes and aromatics were of minor importance. The comparison of modeled and measured peroxide concentrations revealed an underestimation during biomass burning events and an overestimation on haze days, which were ascribed to the direct production of peroxides from biomass burning and the heterogeneous uptake of peroxides by aerosols, respectively. The strengths of the primary emissions from biomass burning were on the same order of the known secondary production rates of atmospheric peroxides during the biomass burning events. The heterogeneous process on aerosol particles was suggested to be the predominant sink for atmospheric peroxides. The atmospheric lifetime of peroxides on haze days in summer in the NCP was about 2–3 h, which is in good agreement with the laboratory studies. Further comprehensive investigations are necessary to better understand the impact of biomass burning and heterogeneous uptake on the concentration of peroxides in the atmosphere.
16
Laborie, Sophie, Jean-Claude Lavoie, Marjolain Pineault e Philippe Chessex. "Contribution of Multivitamins, Air, and Light in the Generation of Peroxides in Adult and Neonatal Parenteral Nutrition Solutions". Annals of Pharmacotherapy 34, n. 4 (aprile 2000): 440–45. http://dx.doi.org/10.1345/aph.19182.
Testo completoAbstract (sommario):
OBJECTIVE: To compare the concentrations of peroxides between adult and neonatal total parenteral nutrition (TPN) solutions in response to protection against inducers of peroxidation such as multivitamins and exposure to light or air. METHODS: Peroxide concentrations were measured in freshly prepared adult and neonatal solutions of fat-free TPN in four settings: with or without an air inlet, and protected or unprotected from ambient light. An oxygen washout was performed by exposing a fat-free neonatal TPN solution to a continuous flow of nitrogen. RESULTS: Globally, light was the main inducer of peroxides in adult and neonatal solutions. However, in adult solutions the concentration of peroxides remained <15 μmol/L, while in neonatal solutions the peroxide concentration was as high as 300 μmol/L in ambient light. Although the oxygen washout did prevent the generation of peroxides, avoiding air inlet was not as effective as was photoprotection in decreasing the important peroxide load in the neonatal TPN solution. CONCLUSIONS: The higher concentration of peroxides found in neonatal solutions compared with adult solutions is explained by the differences in nutrient composition between the two solutions. Contamination of parenteral solutions by air during compounding accounts for the photoinduced generation of peroxides in TPN solutions. It is more convenient to protect TPN solutions from light exposure after the admixture of the multivitamin solution than to avoid contact with oxygen.
17
Jacob, Peter, Bernhard Wehling, Wieland Hill e Dieter Klockow. "Feasibility Study of Raman Spectroscopy as a Tool to Investigate the Liquid-Phase Chemistry of Aliphatic Organic Peroxides". Applied Spectroscopy 51, n. 1 (gennaio 1997): 74–80. http://dx.doi.org/10.1366/0003702971938795.
Testo completoAbstract (sommario):
The described investigations are focused on peroxides occurring as products in atmospheric chemical processes, namely, hydrogen peroxide, methylhydroperoxide, hydroxymethylhydroperoxide, bis-(hydroxymethyl)peroxide, 1-hydroxyethylhydroperoxide, bis-(hydroxyethyl)peroxide, and hydroxymethylmethylperoxide. The compounds are identified and determined through the position and intensity of their characteristic O–O stretching bands in the range between 767 and 878 cm−1. Time-resolved Raman spectroscopy of peroxide solutions permits the in situ investigation of pathways and kinetics of reactions between peroxides and aldehydes.
18
Gaetani, GF, AM Ferraris, M. Rolfo, R. Mangerini, S. Arena e HN Kirkman. "Predominant role of catalase in the disposal of hydrogen peroxide within human erythrocytes". Blood 87, n. 4 (15 febbraio 1996): 1595–99. http://dx.doi.org/10.1182/blood.v87.4.1595.bloodjournal8741595.
Testo completoAbstract (sommario):
Purified enzymes were mixed to form a cell-free system that simulated the conditions for removal of hydrogen peroxide within human erythrocytes. Human glutathione peroxidase disposed of hydrogen peroxide (H2O2) at a rate that was only 17% of the rate at which human catalase simultaneously removed hydrogen peroxide. The relative rates observed were in agreement with the relative rates predicted from the kinetic constants of the two enzymes. These results confirm two earlier studies on intact erythrocytes, which refuted the notion that glutathione peroxidase is the primary enzyme for removal of hydrogen peroxide within erythrocytes. The present findings differ from the results with intact cells, however, in showing that glutathione peroxidase accounts for even less than 50% of the removal of hydrogen peroxide. A means is proposed for calculating the relative contribution of glutathione peroxidase and catalase in other cells and species. The present results raise the possibility that the major function of glutathione peroxidase may be the disposal of organic peroxides rather than the removal of hydrogen peroxide.
19
Mano, T., R. Sinohara, Y. Sawai, N. Oda, Y. Nishida, T. Mokuno, K. Asano et al. "Changes in lipid peroxidation and free radical scavengers in the brain of hyper- and hypothyroid aged rats". Journal of Endocrinology 147, n. 2 (novembre 1995): 361–65. http://dx.doi.org/10.1677/joe.0.1470361.
Testo completoAbstract (sommario):
Abstract To determine how lipid peroxides and free radical scavengers are changed in the brain of hyper- or hypothyroid rats, we examined the behavior of lipid peroxide and free radical scavengers in the cerebral cortex of aged (1·5 years old) rats that had been made hyper- or hypothyroid by the administration of thyroxine or methimazol for 4 weeks. Concentrations of catalase, Mn-superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) were increased in hyperthyroid rats compared with euthyroid rats. Concentrations of total SOD, Cu,Zn-SOD and GSH-PX were increased but that of Mn-SOD was decreased in hypothyroid animals. There were no differences among hyperthyroid, hypothyroid and euthyroid rats in the levels of coenzymes 9 or 10. The concentration of lipid peroxides, determined indirectly by the measurement of thiobarbituric acid reactants, was decreased in hyperthyroid rats but not in hypothyroid rats when compared with euthyroid animals. These findings suggest that free radicals and lipid peroxides are scavenged to compensate for the changes induced by hyper- or hypothyroidism. Journal of Endocrinology (1995) 147, 361–365
20
Wang, Shunyao, Tengyu Liu, Jinmyung Jang, Jonathan P. D. Abbatt e Arthur W. H. Chan. "Heterogeneous interactions between SO<sub>2</sub> and organic peroxides in submicron aerosol". Atmospheric Chemistry and Physics 21, n. 9 (4 maggio 2021): 6647–61. http://dx.doi.org/10.5194/acp-21-6647-2021.
Testo completoAbstract (sommario):
Abstract. Atmospheric models often underestimate particulate sulfate, a major component in ambient aerosol, suggesting missing sulfate formation mechanisms in the models. Heterogeneous reactions between SO2 and aerosol play an important role in particulate sulfate formation and its physicochemical evolution. Here we study the reactive uptake kinetics of SO2 onto aerosol containing organic peroxides. We present chamber studies of SO2 reactive uptake performed under different relative humidity (RH), particulate peroxide contents, peroxide types, and aerosol acidities. Using different model organic peroxides mixed with ammonium sulfate particles, the SO2 uptake coefficient (γSO2) was found to be exponentially dependent on RH. γSO2 increases from 10−3 at RH 25 % to 10−2 at RH 71 % as measured for an organic peroxide with multiple O–O groups. Under similar conditions, the kinetics in this study were found to be structurally dependent: organic peroxides with multiple peroxide groups have a higher γSO2 than those with only one peroxide group, consistent with the reactivity trend previously observed in the aqueous phase. In addition, γSO2 is linearly related to particle-phase peroxide content, which in turn depends on gas–particle partitioning of organic peroxides. Aerosol acidity plays a complex role in determining SO2 uptake rate, influenced by the effective Henry's Law constant of SO2 and the condensed-phase kinetics of the peroxide–SO2 reaction in the highly concentrated aerosol phase. These uptake coefficients are consistently higher than those calculated from the reaction kinetics in the bulk aqueous phase, and we show experimental evidence suggesting that other factors, such as particle-phase ionic strength, can play an essential role in determining the uptake kinetics. γSO2 values for different types of secondary organic aerosol (SOA) were measured to be on the order of 10−4. Overall, this study provides quantitative evidence of the multiphase reactions between SO2 and organic peroxides, highlighting the important factors that govern the uptake kinetics.
21
Dutka, Volodymyr, Olena Aksimentyeva, Nataliya Oschapovska, Yaroslav Kovalskyi e Halyna Halechko. "Adsorption and Decomposition of Peroxides on the Surfaces of Dispersed Oxides Fe2O3, Cr2O3 and V2O5". Colloids and Interfaces 3, n. 1 (17 gennaio 2019): 13. http://dx.doi.org/10.3390/colloids3010013.
Testo completoAbstract (sommario):
The adsorption of peroxides on dispersed oxides Fe2O3, Cr2O3 and V2O5 was studied. It is shown that the adsorption of peroxides is described by the Langmuir equation. The adsorption of benzoyl peroxide grows within Fe2O3<Cr2O3<V2O5. Adsorption-desorption equilibrium constants (K) for Cr2O3 and V2O5 are the same, but for Fe2O3 this value is 6 times higher. The decomposition of peroxides is observed in the solution and on the surface of adsorbents. The effective activation energy (E) of the thermal decomposition of peroxides in the studied systems is in the range of 80–140 kJ/mol. The activation energy of degradation of peroxides on the surface (Es) of the dispersed oxides studied is lower. The degradation reaction of peroxides on the surface of Fe2O3 and V2O5 has an oxidation-reducing nature, during which free radicals are produced. On the surface of Cr2O3, there is a heterolytic decay of peroxides. The parameters of the reaction of peroxides decomposition are found. The decomposition of peroxides in the presence of Fe2O3, Cr2O3 and V2O5 in styrene is accompanied by the formation of polystyrene both in the solution and on the surface of the adsorbent.
22
Atack, John M., Philippa Harvey, Michael A. Jones e David J. Kelly. "The Campylobacter jejuni Thiol Peroxidases Tpx and Bcp Both Contribute to Aerotolerance and Peroxide-Mediated Stress Resistance but Have Distinct Substrate Specificities". Journal of Bacteriology 190, n. 15 (30 maggio 2008): 5279–90. http://dx.doi.org/10.1128/jb.00100-08.
Testo completoAbstract (sommario):
ABSTRACT The microaerophilic food-borne pathogen Campylobacter jejuni experiences variable oxygen concentrations during its life cycle, especially during transitions between the external environment and the avian or mammalian gut. Single knockout mutations in either one of two related thiol peroxidase genes, tpx and bcp, resulted in normal microaerobic growth (10% [vol/vol] oxygen) but poorer growth than that of the wild type under high-aeration conditions (21% [vol/vol] oxygen). However, a tpx/bcp double mutant had a severe microaerobic growth defect and did not grow at high aeration in shake flasks. Although the single mutant strains were no more sensitive than the wild-type strains in disc diffusion assays with hydrogen peroxide, organic peroxides, superoxide, or nitrosative stress agents, in all cases the double mutant was hypersensitive. Quantitative cell viability and cellular lipid peroxidation assays indicated some increased sensitivity of the single tpx and bcp mutants to peroxide stress. Protein carbonylation studies revealed that the tpx/bcp double mutant had a higher degree of oxygen- and peroxide-induced oxidative protein damage than did either of the single mutants. An analysis of the peroxidase activity of the purified recombinant enzymes showed that, surprisingly, Tpx reduced only hydrogen peroxide as substrate, whereas Bcp also reduced organic peroxides. Immunoblotting of wild-type cell extracts with Tpx- or Bcp-specific antibodies showed increased abundance of both proteins under high aeration compared to that under microaerobic growth conditions. Taken together, the results suggest that Tpx and Bcp are partially redundant antioxidant enzymes that play an important role in protection of C. jejuni against oxygen-induced oxidative stress.
23
Yaremenko, Ivan A., Vera A. Vil’, Dmitry V. Demchuk e Alexander O. Terent’ev. "Rearrangements of organic peroxides and related processes". Beilstein Journal of Organic Chemistry 12 (3 agosto 2016): 1647–748. http://dx.doi.org/10.3762/bjoc.12.162.
Testo completoAbstract (sommario):
This review is the first to collate and summarize main data on named and unnamed rearrangement reactions of peroxides. It should be noted, that in the chemistry of peroxides two types of processes are considered under the term rearrangements. These are conventional rearrangements occurring with the retention of the molecular weight and transformations of one of the peroxide moieties after O–O-bond cleavage. Detailed information about the Baeyer−Villiger, Criegee, Hock, Kornblum−DeLaMare, Dakin, Elbs, Schenck, Smith, Wieland, and Story reactions is given. Unnamed rearrangements of organic peroxides and related processes are also analyzed. The rearrangements and related processes of important natural and synthetic peroxides are discussed separately.
24
Bourgeois, Marie-Josèphe, Marianne Vialemaringe, Monique Campagnole e Evelyne Montaudon. "Réaction compétitive de la substitution homolytique intramoléculaire : décomposition de peroxydes allyliques dans le thioglycolate de méthyle". Canadian Journal of Chemistry 79, n. 3 (1 marzo 2001): 257–62. http://dx.doi.org/10.1139/v01-024.
Testo completoAbstract (sommario):
The decomposition of allylic peroxides in methyl thioglycolate always leads to both epoxide and adduct peroxide. According to the nature of the allylic chain, either epoxide or peroxide is the predominant product, if not the only one. It is the first example where the hydrogen transfer is as fast as the intramolecular homolytic substitution. The influence of different factors upon the competition is studied.Key words: allylic peroxides, epoxides, intramolecular homolytic substitution, transfer.
25
Li, H., Z. M. Chen, L. B. Huang e D. Huang. "Organic peroxides gas-particle partitioning and rapid heterogeneous decomposition on secondary organic aerosol". Atmospheric Chemistry and Physics Discussions 15, n. 20 (20 ottobre 2015): 28133–65. http://dx.doi.org/10.5194/acpd-15-28133-2015.
Testo completoAbstract (sommario):
Abstract. Organic peroxides, important species in the atmosphere, will promote secondary organic aerosols (SOA) aging, affect HOx radicals cycling, and cause adverse health effects. However, the formation, gas-particle partitioning, and evolution of organic peroxides are extremely complicated and still unclear. In this study, we investigate in the laboratory the production and gas-particle partitioning of peroxides from the ozonolysis of α-pinene, which is one of the major biogenic volatile organic compounds in the atmosphere and is an important precursor for SOA at a global scale. We have determined the molar yields of hydrogen peroxide (H2O2), hydroxymethyl hydroperoxide (HMHP), peroxyformic acid (PFA), peroxyacetic acid (PAA) and total peroxides (TPO, including unknown peroxides) and the fraction of peroxides in SOA. Comparing the gas-phase and particle-phase peroxides, we find that gas-particle partitioning coefficients of PFA and PAA are 104 times higher than theoretical prediction, indicating that organic peroxides play a more important role in the SOA formation than expected previously. Here, we give the partitioning coefficients of TPO as (2–3) × 10-4 m3μg-1. Even so, more than 80 % of the peroxides formed in the reaction remain in the gas phase. Water does not affect the total amount of peroxides in either the gas or particle phase, but can change the distribution of gaseous peroxides. About 18 % gaseous peroxides undergo rapid heterogeneous decomposition on SOA particles in the presence of water vapor, resulting in the additional production of H2O2. This process can partially interpret the unexpected high H2O2 yield under wet conditions. Transformation of organic peroxides to H2O2 also saves OH in the atmosphere, helping to improve the understanding of OH cycling.
26
Li, Huan, Zhongming Chen, Liubin Huang e Dao Huang. "Organic peroxides' gas-particle partitioning and rapid heterogeneous decomposition on secondary organic aerosol". Atmospheric Chemistry and Physics 16, n. 3 (17 febbraio 2016): 1837–48. http://dx.doi.org/10.5194/acp-16-1837-2016.
Testo completoAbstract (sommario):
Abstract. Organic peroxides, important species in the atmosphere, promote secondary organic aerosol (SOA) aging, affect HOx radicals cycling, and cause adverse health effects. However, the formation, gas-particle partitioning, and evolution of organic peroxides are complicated and still unclear. In this study, we investigated in the laboratory the production and gas-particle partitioning of peroxides from the ozonolysis of α-pinene, which is one of the major biogenic volatile organic compounds in the atmosphere and an important precursor for SOA at a global scale. We have determined the molar yields of hydrogen peroxide (H2O2), hydromethyl hydroperoxide (HMHP), peroxyformic acid (PFA), peroxyacetic acid (PAA), and total peroxides (TPOs, including unknown peroxides) and the fraction of peroxides in α-pinene/O3 SOA. Comparing the gas-phase peroxides with the particle-phase peroxides, we find that gas-particle partitioning coefficients of PFA and PAA are 104 times higher than the values from the theoretical prediction, indicating that organic peroxides play a more important role in SOA formation than previously expected. Here, the partitioning coefficients of TPO were determined to be as high as (2–3) × 10−4 m3 µg−1. Even so, more than 80 % of the peroxides formed in the reaction remain in the gas phase. Water changes the distribution of gaseous peroxides, while it does not affect the total amount of peroxides in either the gas or the particle phase. Approx. 18 % of gaseous peroxides undergo rapid heterogeneous decomposition on SOA particles in the presence of water vapor, resulting in the additional production of H2O2. This process can partially explain the unexpectedly high H2O2 yields under wet conditions. Transformation of organic peroxides to H2O2 also preserves OH in the atmosphere, helping to improve the understanding of OH cycling.
27
Lin, Shuqiong, Behnam Ashrafi, Kurtis Laqua, Keun Su Kim e Benoit Simard. "Covalent derivatization of boron nitride nanotubes with peroxides and their application in polycarbonate composites". New Journal of Chemistry 41, n. 15 (2017): 7571–77. http://dx.doi.org/10.1039/c7nj00193b.
Testo completo
28
WILKINSON, Shane R., David J. MEYER e John M. KELLY. "Biochemical characterization of a trypanosome enzyme with glutathione-dependent peroxidase activity". Biochemical Journal 352, n. 3 (8 dicembre 2000): 755–61. http://dx.doi.org/10.1042/bj3520755.
Testo completoAbstract (sommario):
In most eukaryotes, glutathione-dependent peroxidases play a key role in the metabolism of peroxides. Numerous studies have reported that trypanosomatids lack this activity. Here we show that this is not the case, at least for the American trypanosome Trypanosoma cruzi. We have isolated a single-copy gene from T. cruzi with the potential to encode an 18kDa enzyme, the sequence of which has highest similarity with glutathione peroxidases from plants. A recombinant form of the protein was purified following expression in Escherichia coli. The enzyme was shown to have peroxidase activity in the presence of glutathione/glutathione reductase but not in the presence of trypanothione/trypanothione reductase. It could metabolize a wide range of hydroperoxides (linoleic acid hydroperoxide and phosphatidylcholine hydroperoxide> cumene hydroperoxide>t-butyl hydroperoxide), but no activity towards hydrogen peroxide was detected. Enzyme activity could be saturated by glutathione when both fatty acid and short-chain organic hydroperoxides were used as substrate. For linoleic acid hydroperoxide, the rate-limiting step of this reaction is the reduction of the peroxidase by glutathione. With lower-affinity substrates such as t-butyl hydroperoxide, the rate-limiting step is the reduction of the oxidant. The data presented here identify a new arm of the T. cruzi oxidative defence system.
29
Bhowmick, Debasish, e Govindasamy Mugesh. "Insights into the catalytic mechanism of synthetic glutathione peroxidase mimetics". Organic & Biomolecular Chemistry 13, n. 41 (2015): 10262–72. http://dx.doi.org/10.1039/c5ob01665g.
Testo completoAbstract (sommario):
This review focuses on the variation of the catalytic mechanisms of synthetic glutathione peroxidase (GPx) mimics depending on their structures and reactivities towards thiols and peroxides. Compounds of different categories follow a characteristic mechanism for the reduction of peroxides.
30
Liu, Wenqiu, Xuejun Liu, David Knaebel, Linda Luck e Yuzhou Li. "Synthesis and Antibacterial Evaluation of Novel Water-Soluble Organic Peroxides". Antimicrobial Agents and Chemotherapy 42, n. 4 (1 aprile 1998): 911–15. http://dx.doi.org/10.1128/aac.42.4.911.
Testo completoAbstract (sommario):
ABSTRACT A set of new water-soluble organic peroxides has been synthesized and evaluated for in vitro antibacterial activity as part of an effort to develop new antibacterial agents for the treatment of acne vulgaris. The water solubility of these new dialkyl peroxides and peroxyesters was achieved by incorporating either a quaternary ammonium group or a polyethylene glycol moiety. These peroxides are effective against both gram-positive and gram-negative bacteria and have a prolonged activity compared to that of benzoyl peroxide and other peroxide-type antiseptic agents. Among them 4-[[(tert-butylperoxy)carbonyl]benzyl]triethylammonium chloride and [10-(tert-butylperoxy)decyl]trimethylammonium bromide have the broadest antimicrobial spectrums. We have shown that the oxidizing properties of the dioxy group of these compounds are responsible for their antibacterial activities.
31
Chessex, Philippe, Jean‐Claude Lavoie, Sophie Laborie e Thérèse Rouleau. "Parenteral Multivitamin Supplementation Induces Both Oxidant and Antioxidant Responses in the Liver of Newborn Guinea Pigs". Journal of Pediatric Gastroenterology and Nutrition 32, n. 3 (marzo 2001): 316–21. http://dx.doi.org/10.1002/j.1536-4801.2001.tb07275.x.
Testo completoAbstract (sommario):
ABSTRACTBackgroundThe multivitamin solution is a major component of photo‐induced generation of peroxides in parenteral nutrition. The aim of this study was to determine whether the parenteral multivitamin preparation induces in the liver a peroxide‐induced oxidant challenge or an antioxidant protection associated with the antiradical components of the solution.MethodsNewborn guinea pigs were infused with dextrose supplemented with peroxides (250 μmol/L H2O2 or 350 μmol/L tert‐butylhydroperoxide) or with a multivitamin preparation (MVP, 1% vol/vol). After 4 days, total glutathione and a free radical–sensitive eicosanoid marker (prostaglandin I2 [PGI2]/total prostaglandins) were measured in livers.ResultsThere was a significant decrease in the PGI2/total prostaglandin ratio (mean ± SEM ) [dextrose: 0.068 ± 0.007 vs. (dextrose + H2O2: 0.048 ± 0.001, dextrose + TBH: 0.043 ± 0.001)] and glutathione concentrations decreased [dextrose: 55 ± 7 vs. (dextrose + H2O2: 37 ± 7, dextrose + TBH: 18 ± 7 nmol/mg protein)] after infusion of peroxides. Despite the peroxide load in the multivitamin solution, it did not alter the measured variables as prostanoid ratio remained at control concentrations (dextrose: 0.066 ± 0.008 vs. dextrose + MVP: 0.065 ± 0.006), as did glutathione levels (dextrose: 52 ± 6 vs. dextrose + MVP: 45 ± 7 nmol/mg prot).ConclusionIn the liver of guinea pig pups, infused peroxides cause oxidation of membrane‐derived prostanoids. The decrease in glutathione in response to administration of peroxides suggests consumption rather than a response to a free radical attack. Despite the oxidant load associated with peroxides generated in MVP, the multivitamin preparation protected membranes as the prostanoid ratio, and glutathione levels remained at control levels.
32
Terent'ev, Alexander O., Dmitry A. Borisov, Vera A. Vil’ e Valery M. Dembitsky. "Synthesis of five- and six-membered cyclic organic peroxides: Key transformations into peroxide ring-retaining products". Beilstein Journal of Organic Chemistry 10 (8 gennaio 2014): 34–114. http://dx.doi.org/10.3762/bjoc.10.6.
Testo completoAbstract (sommario):
The present review describes the current status of synthetic five and six-membered cyclic peroxides such as 1,2-dioxolanes, 1,2,4-trioxolanes (ozonides), 1,2-dioxanes, 1,2-dioxenes, 1,2,4-trioxanes, and 1,2,4,5-tetraoxanes. The literature from 2000 onwards is surveyed to provide an update on synthesis of cyclic peroxides. The indicated period of time is, on the whole, characterized by the development of new efficient and scale-up methods for the preparation of these cyclic compounds. It was shown that cyclic peroxides remain unchanged throughout the course of a wide range of fundamental organic reactions. Due to these properties, the molecular structures can be greatly modified to give peroxide ring-retaining products. The chemistry of cyclic peroxides has attracted considerable attention, because these compounds are used in medicine for the design of antimalarial, antihelminthic, and antitumor agents.
33
Huang, D., Z. M. Chen, Y. Zhao e H. Liang. "Newly observed peroxides and the water effect on the formation and removal of hydroxyalkyl hydroperoxides in the ozonolysis of isoprene". Atmospheric Chemistry and Physics 13, n. 11 (12 giugno 2013): 5671–83. http://dx.doi.org/10.5194/acp-13-5671-2013.
Testo completoAbstract (sommario):
Abstract. The ozonolysis of alkenes is considered to be an important source of atmospheric peroxides, which serve as oxidants, reservoirs of HOx radicals, and components of secondary organic aerosols (SOAs). Recent laboratory investigations of this reaction identified hydrogen peroxide (H2O2) and hydroxymethyl hydroperoxide (HMHP) in ozonolysis of isoprene. Although larger hydroxyalkyl hydroperoxides (HAHPs) were also expected, their presence is not currently supported by experimental evidence. In the present study, we investigated the formation of peroxides in the gas phase ozonolysis of isoprene at various relative humidities on a time scale of tens of seconds, using a quartz flow tube reactor coupled with the online detection of peroxides. We detected a variety of conventional peroxides, including H2O2, HMHP, methyl hydroperoxide, bis-hydroxymethyl hydroperoxide, and ethyl hydroperoxide, and interestingly found three unknown peroxides. The molar yields of the conventional peroxides fell within the range of values provided in the literature. The three unknown peroxides had a combined molar yield of ~ 30% at 5% relative humidity (RH), which was comparable with that of the conventional peroxides. Unlike H2O2 and HMHP, the molar yields of these three unknown peroxides were inversely related to the RH. On the basis of experimental kinetic and box model analysis, we tentatively assigned these unknown peroxides to C2−C4 HAHPs, which are produced by the reactions of different Criegee intermediates with water. Our study provides experimental evidence for the formation of large HAHPs in the ozonolysis of isoprene (one of the alkenes). These large HAHPs have a sufficiently long lifetime, estimated as tens of minutes, which allows them to become involved in atmospheric chemical processes, e.g., SOA formation and radical recycling.
34
Hill, Stephen, Wesley Box e Robert A. DiSilvestro. "Moderate Intensity Resistance Exercise, Plus or Minus Soy Intake: Effects on Serum Lipid Peroxides in Young Adult Males". International Journal of Sport Nutrition and Exercise Metabolism 14, n. 2 (aprile 2004): 125–32. http://dx.doi.org/10.1123/ijsnem.14.2.125.
Testo completoAbstract (sommario):
Lipid peroxides can be both a product and an initiator of oxidant stress. Conceivably, exercise can either increase concentrations of lipid peroxides (by causing oxidant stress), or decrease them (by accelerating peroxide breakdown). The net effect could depend on exercise intensity and nutritional intake of antioxidants. The present study examined the response of serum lipid peroxides to the combination of moderate intensity, weight resistance exercise plus intake of soy protein, a source of antioxidant phytochemicals. Recreationally trained, young adult men (N = 18) consumed soy protein or antioxidant-poor whey protein for 4 weeks (40 g protein/d) before a session of moderate intensity, weight resistance exercise. In the soy group, exercise decreased values for serum lipid peroxides at 5 min, 3 h, and 24 h post-exercise. The whey group showed the depression only at 24 h. In both the soy and whey groups, a small rise was seen for interleukin-8, which is consistent with the idea that the exercise session induced a moderate muscle stress. In summary, a moderate intensity, weight resistance exercise session, despite inducing mild inflammation, depressed plasma serum peroxide values, especially when combined with 4 weeks of soy consumption.
35
Abran, D., D. R. Varma e S. Chemtob. "Increased thromboxane-mediated contractions of retinal vessels of newborn pigs to peroxides". American Journal of Physiology-Heart and Circulatory Physiology 268, n. 2 (1 febbraio 1995): H628—H632. http://dx.doi.org/10.1152/ajpheart.1995.268.2.h628.
Testo completoAbstract (sommario):
The vasomotor effects of three peroxides (H2O2, cumene hydroperoxide, and t-butyl hydroperoxide) on the retinal vasculature, as well as the role of thromboxane in these effects, were studied using time-frame photography of isolated eyecup preparations from newborn and adult pigs. All three peroxides caused constriction of retinal arteries and veins, and these effects were greater in the newborn than in the adult. The cyclooxygenase inhibitor indomethacin, the thromboxane synthase blocker CGS-13080, and the thromboxane receptor blockers GR-32191B and L-670,596 inhibited the peroxide-induced vasoconstriction. The peroxides also increased thromboxane levels in the retina, and this increase was greater in newborn than in adult tissues. Both indomethacin and CGS-13080 prevented the peroxide-induced increase in retinal thromboxane. The thromboxane analogue U-46619 also produced constriction of newborn and adult retinal vessels, but its effects on the retinal veins of newborn pigs were less than those on adult veins. Data indicate an important role for increased production of thromboxane in the relative increase in the vasoconstrictor effects of peroxides on the newborn retinal vasculature. These findings suggest that the vasoconstriction and occlusion after oxidative stresses, which precede retinal neovascularization, are mediated by thromboxane.
36
Furletov, Aleksei, Vladimir Apyari, Alexey Garshev e Stanislava Dmitrienko. "A Comparative Study on the Oxidation of Label-Free Silver Triangular Nanoplates by Peroxides: Main Effects and Sensing Applications". Sensors 20, n. 17 (27 agosto 2020): 4832. http://dx.doi.org/10.3390/s20174832.
Testo completoAbstract (sommario):
Nowadays, analytical systems based on silver triangular nanoplates (AgTNPs) have been shown as good prospects for chemical sensing. However, they still remain relatively poorly studied as colorimetric probes for sensing various classes of compounds. This study shows that these nanoparticles are capable of being oxidized by peroxides, including both hydrogen peroxide and its organic derivatives. The oxidation was found to result in a decrease in the AgTNPs’ local surface plasmon resonance band intensity at 620 nm. This was proposed for peroxide-sensitive spectrophotometric determination. Five peroxides differing in their structure and number of functional groups were tested. Three of them easily oxidized AgTNPs. The effects of a structure of analytes and main exterior factors on the oxidation are discussed. The detection limits of peroxides in the selected conditions increased in the series peracetic acid < hydrogen peroxide < tert-butyl hydroperoxide, coming to 0.08, 1.6 and 24 μmol L−1, respectively. tert-Butyl peroxybenzoate and di-tert-butyl peroxide were found to have no effect on the spectral characteristics of AgTNPs. By the example of hydrogen peroxide, it was found that the determination does not interfere with 100–4000-fold quantities of common inorganic ions. The proposed approach was successfully applied to the analysis of drugs, cosmetics and model mixtures.
37
Huang, D., Z. M. Chen, Y. Zhao e H. Liang. "Newly observed peroxides and the water effect on the formation and removal of hydroxyalkyl hydroperoxides in the ozonolysis of isoprene". Atmospheric Chemistry and Physics Discussions 13, n. 2 (25 febbraio 2013): 5279–314. http://dx.doi.org/10.5194/acpd-13-5279-2013.
Testo completoAbstract (sommario):
Abstract. The ozonolysis of alkenes is considered to be an important source of atmospheric peroxides, which serve as oxidants, reservoirs of HOx radicals, and components of secondary organic aerosols (SOAs). Recent laboratory investigations of this reaction identified hydrogen peroxide (H2O2) and hydroxymethyl hydroperoxide (HMHP). Although larger hydroxyalkyl hydroperoxides (HAHPs) were also expected, their presence is not currently supported by experimental evidence. In the present study, we investigated the formation of peroxides in the gas phase ozonolysis of isoprene at various relative humidities on a time scale of tens of seconds, using a quartz flow tube reactor coupled with the online detection of peroxides. We detected a variety of conventional peroxides, including H2O2, HMHP, methyl hydroperoxide, bis-hydroxymethyl hydroperoxide, and ethyl hydroperoxide, and interestingly found three unknown peroxides. The molar yields of the conventional peroxides fell within the range of values provided in the literature. The three unknown peroxides had a combined molar yield of ~30% at 5% relative humidity (RH), which was comparable with that of the conventional peroxides. Unlike H2O2 and HMHP, the molar yields of these three unknown peroxides were inversely related to the RH. On the basis of experimental kinetic and box model analysis, we tentatively assigned these unknown peroxides to C2–C4 HAHPs, which are produced by the reactions of different Criegee intermediates with water. Our study provides experimental evidence for the formation of large HAHPs in the ozonolysis of isoprene (one of the alkenes). These large HAHPs have a sufficiently long lifetime, estimated as tens of minutes, which allows them to become involved in atmospheric chemical processes, e.g. SOA formation and radical recycling. These standards are needed to accurately specify HAHPs, although their synthesis is a challenge.
38
Naskar, K., e J. W. M. Noordermeer. "Dynamically Vulcanized PP/EPDM Blends: Effects of Different Types of Peroxides on the Properties". Rubber Chemistry and Technology 76, n. 4 (1 settembre 2003): 1001–18. http://dx.doi.org/10.5254/1.3547766.
Testo completoAbstract (sommario):
Abstract Thermoplastic vulcanizates (TPVs) or dynamic vulcanizates are thermoplastic elastomers produced by simultaneous mixing and crosslinking of a rubber and a thermoplastic. The effects of different types of peroxides as curing agents on the properties of PP/EPDM TPVs were investigated at a fixed blend ratio. The mechanical properties change significantly with the chemical nature of the peroxides, the extent of crosslinking of EPDM and the extent of degradation of PP. Three main parameters have been identified governing the final mechanical properties of TPVs: the solubility parameter of a peroxide relative to the substrates PP and EPDM, the fragmentation mechanism of the peroxide and the kinetic aspects of the peroxide fragmentation. Dicumyl peroxide gives the best balance of all properties, it complies the best of all with these parameters.
39
Saccoccia, Fulvio, Francesco Angelucci, Giovanna Boumis, Gianni Desiato, Adriana E. Miele e Andrea Bellelli. "Selenocysteine robustness versus cysteine versatility: a hypothesis on the evolution of the moonlighting behaviour of peroxiredoxins". Biochemical Society Transactions 42, n. 6 (17 novembre 2014): 1768–72. http://dx.doi.org/10.1042/bst20140212.
Testo completoAbstract (sommario):
Peroxiredoxins (Prxs) and glutathione peroxidases (Gpxs) provide the majority of peroxides reducing activity in the cytoplasm. Both are peroxidases but differences in the chemical mechanism of reduction of oxidative agents, as well as in the reactivity of the catalytically active residues, confer peculiar features on them. Ultimately, Gpx should be regarded as an efficient peroxides scavenger having a high-reactive selenocysteine (Sec) residue. Prx, by having a low pKa cysteine, is less efficient than Gpx in reduction of peroxides under physiological conditions, but the chemistry of the sulfur together with the peculiar structural arrangement of the active site, in typical Prxs, make it suitable to sense a redox environment and to switch-in-function so as to exert holdase activity under redox-stress conditions. The complex macromolecular assembly would have evolved the chaperone holdase function and the moonlighting behaviour typical of many Prxs.
40
Arp, Fabian F., Shin Hye Ahn, Nattamai Bhuvanesh e Janet Blümel. "Selective synthesis and stabilization of peroxides via phosphine oxides". New Journal of Chemistry 43, n. 44 (2019): 17174–81. http://dx.doi.org/10.1039/c9nj04858h.
Testo completo
41
Johnson, Robert M., Gerard Goyette, Yaddanapudi Ravindranath e Ye-Shih Ho. "Red cells from glutathione peroxidase-1–deficient mice have nearly normal defenses against exogenous peroxides". Blood 96, n. 5 (1 settembre 2000): 1985–88. http://dx.doi.org/10.1182/blood.v96.5.1985.
Testo completoAbstract (sommario):
Abstract The role of glutathione peroxidase in red cell anti-oxidant defense was examined using erythrocytes from mice with a genetically engineered disruption of the glutathione peroxidase-1 (GSHPx-1) gene. Because GSHPx-1 is the sole glutathione peroxidase in the erythrocyte, all red cell GSH peroxidase activity was eliminated. Oxidation of hemoglobin and membrane lipids, using the cis-parinaric acid assay, was determined during oxidant challenge from cumene hydroperoxide and H2O2. No difference was detected between wild-type red cells and GSHPx-1–deficient cells, even at high H2O2 exposures. Thus, GSHPx-1 appears to play little or no role in the defense of the erythrocyte against exposure to peroxide. Simultaneous exposure to an H2O2 flux and the catalase inhibitor 3-amino-1,2,4-triazole supported this conclusion. Hemoglobin oxidation occurred only when catalase was depleted. Circulating erythrocytes from the GSHPx-1–deficient mice exhibited a slight reduction in membrane thiols, indicating that high exposure to peroxides might occur naturally in the circulation.
42
Johnson, Robert M., Gerard Goyette, Yaddanapudi Ravindranath e Ye-Shih Ho. "Red cells from glutathione peroxidase-1–deficient mice have nearly normal defenses against exogenous peroxides". Blood 96, n. 5 (1 settembre 2000): 1985–88. http://dx.doi.org/10.1182/blood.v96.5.1985.h8001985_1985_1988.
Testo completoAbstract (sommario):
The role of glutathione peroxidase in red cell anti-oxidant defense was examined using erythrocytes from mice with a genetically engineered disruption of the glutathione peroxidase-1 (GSHPx-1) gene. Because GSHPx-1 is the sole glutathione peroxidase in the erythrocyte, all red cell GSH peroxidase activity was eliminated. Oxidation of hemoglobin and membrane lipids, using the cis-parinaric acid assay, was determined during oxidant challenge from cumene hydroperoxide and H2O2. No difference was detected between wild-type red cells and GSHPx-1–deficient cells, even at high H2O2 exposures. Thus, GSHPx-1 appears to play little or no role in the defense of the erythrocyte against exposure to peroxide. Simultaneous exposure to an H2O2 flux and the catalase inhibitor 3-amino-1,2,4-triazole supported this conclusion. Hemoglobin oxidation occurred only when catalase was depleted. Circulating erythrocytes from the GSHPx-1–deficient mice exhibited a slight reduction in membrane thiols, indicating that high exposure to peroxides might occur naturally in the circulation.
43
Opsenica, Dejan, e Bogdan Solaja. "Antimalarial peroxides". Journal of the Serbian Chemical Society 74, n. 11 (2009): 1155–93. http://dx.doi.org/10.2298/jsc0911155o.
Testo completoAbstract (sommario):
The problem of endemic malaria continues unabated globally. Malaria affects 40 % of the global population, causing an estimated annual mortality of 1.5-2.7 million people. The World Health Organization (WHO) estimates that 90 % of these deaths occur in sub-Saharan Africa among infants under the age of five. While a vaccine against malaria continues to be elusive, chemotherapy remains the most viable alternative towards treatment of the disease. During last years, the situation has become urgent in many ways, but mainly because of the development of chloroquine-resistant (CQR) strains of Plasmodium falciparum (Pf). The discovery that artemisinin (ART, 1), an active principle of Artemisia annua L., expresses a significant antimalarial activity, especially against CQR strains, opened new approaches for combating malaria. Since the early 1980s, hundreds of semi-synthetic and synthetic peroxides have been developed and tested for their antimalarial activity, the results of which were extensively reviewed. In addition, in therapeutic practice, there is no reported case of drug resistance to these antimalarial peroxides. This review summarizes recent achievements in the area of peroxide drug development for malaria chemotherapy.
44
Shahnaj, Sharifun, Rimpy Chowhan, Potshangbam Meetei, Pushpa Kakchingtabam, Khundrakpam Herojit Singh, Laishram Rajendrakumar Singh, Potshangbam Nongdam, Aron Fisher e Hamidur Rahaman. "Hyperoxidation of Peroxiredoxin 6 Induces Alteration from Dimeric to Oligomeric State". Antioxidants 8, n. 2 (2 febbraio 2019): 33. http://dx.doi.org/10.3390/antiox8020033.
Testo completoAbstract (sommario):
Peroxiredoxins(Prdx), the family of non-selenium glutathione peroxidases, are important antioxidant enzymes that defend our system from the toxic reactive oxygen species (ROS). They are thiol-based peroxidases that utilize self-oxidation of their peroxidatic cysteine (Cp) group to reduce peroxides and peroxidized biomolecules. However, because of its high affinity for hydrogen peroxide this peroxidatic cysteine moiety is extremely susceptible to hyperoxidation, forming peroxidase inactive sulfinic acid (Cys-SO2H) and sulfonic acid (Cys-SO3H) derivatives. With the exception of peroxiredoxin 6 (Prdx6), hyperoxidized sulfinic forms of Prdx can be reversed to restore peroxidase activity by the ATP-dependent enzyme sulfiredoxin. Interestingly, hyperoxidized Prdx6 protein seems to have physiological significance as hyperoxidation has been reported to dramatically upregulate its calcium independent phospholipase A2 activity. Using biochemical studies and molecular dynamic (MD) simulation, we investigated the roles of thermodynamic, structural and internal flexibility of Prdx6 to comprehend the structural alteration of the protein in the oxidized state. We observed the loosening of the hydrophobic core of the enzyme in its secondary and tertiary structures. These changes do not affect the internal dynamics of the protein (as indicated by root-mean-square deviation, RMSD and root mean square fluctuation, RMSF plots). Native-PAGE and dynamic light scattering experiments revealed the formation of higher oligomers of Prdx6 under hyperoxidation. Our study demonstrates that post translational modification (like hyperoxidation) in Prdx6 can result in major alterations of its multimeric status.
45
Foglia, Thomas A., Leonard S. Silbert e Peter D. Vail. "Peroxides". Journal of Chromatography A 637, n. 2 (maggio 1993): 157–65. http://dx.doi.org/10.1016/0021-9673(93)83208-a.
Testo completo
46
Chung, Chun-Hui, Tsung-yong Ma, Shin-yuan Fen e Hin-chung Wong. "Activities of Alkyl Hydroperoxide Reductase Subunits C1 and C2 of Vibrio parahaemolyticus against Different Peroxides". Applied and Environmental Microbiology 80, n. 23 (19 settembre 2014): 7398–404. http://dx.doi.org/10.1128/aem.02701-14.
Testo completoAbstract (sommario):
ABSTRACTAlkyl hydroperoxide reductase subunit C gene (ahpC) functions were characterized inVibrio parahaemolyticus, a commonly occurring marine food-borne enteropathogenic bacterium. TwoahpCgenes,ahpC1(VPA1683) andahpC2(VP0580), encoded putative two-cysteine peroxiredoxins, which are highly similar to the homologous proteins ofVibrio vulnificus. The responses of deletion mutants ofahpCgenes to various peroxides were compared with and without gene complementation and at different incubation temperatures. The growth of theahpC1mutant andahpC1 ahpC2double mutant in liquid medium was significantly inhibited by organic peroxides, cumene hydroperoxide andtert-butyl hydroperoxide. However, inhibition was higher at 12°C and 22°C than at 37°C. Inhibiting effects were prevented by the complementaryahpC1gene. Inconsistent detoxification of H2O2byahpCgenes was demonstrated in an agar medium but not in a liquid medium. Complementation with anahpC2gene partially restored the peroxidase effect in the doubleahpC1 ahpC2mutant at 22°C. This investigation reveals thatahpC1is the chief peroxidase gene that acts against organic peroxides inV. parahaemolyticusand that the function of theahpCgenes is influenced by incubation temperature.
47
Burkhart, Craig G., Cynthia Butcher, Craig N. Burkhart e Paul Lehmann. "Effects of Benzoyl Peroxide on Lipogenesis in Sebaceous Glands Using an Animal Model". Journal of Cutaneous Medicine and Surgery 4, n. 3 (luglio 2000): 138–41. http://dx.doi.org/10.1177/120347540000400305.
Testo completoAbstract (sommario):
Background: Benzoyl peroxide is the most widely used topical agent for acne since the 1960s. Concomitant treatment of benzoyl peroxide with oral, or topical antibiotics diminishes the multiplication of antibiotic-resistant strains of Propionibacteria acnes. Besides being antibacterial, the chemical also functions as a peeling agent, has comedolytic activity, reduces free fatty acid levels, and is touted to be sebosuppressive. Objective: The purpose was to determine the ability of topically applied benzoyl peroxide to suppress lipogenesis of the sebaceous glands. Methods: The data were obtained employing an animal model for human sebaceous glands, namely, the flank organs of female golden Syrian hamsters. Results: Our results reveal no inhibition of lipogenesis in sebaceous glands by topical application of benzoyl peroxide. Conclusion: Despite many functions beneficial in acne therapy, benzoyl peroxide does not possess sebosuppressive capabilities. With the advent of water-soluble organic peroxides revealing similar antimicrobial activity to benzoyl peroxide, all therapeutic parameters (save for sebosup-pression) will need to be assessed to weigh the benefits of these second-generation acne-fighting peroxides.
48
Sakamoto, Toshio, Victoria B. Delgaizo e Donald A. Bryant. "Growth on Urea Can Trigger Death and Peroxidation of the Cyanobacterium Synechococcus sp. Strain PCC 7002". Applied and Environmental Microbiology 64, n. 7 (1 luglio 1998): 2361–66. http://dx.doi.org/10.1128/aem.64.7.2361-2366.1998.
Testo completoAbstract (sommario):
ABSTRACT Laboratory conditions have been identified that cause the rapid death of cultures of cyanobacteria producing urease. Once the death phase had initiated in the stationary growth phase, cells were rapidly bleached of all pigmentation. Null mutations in the ureCgene, encoding the alpha subunit of urease, were constructed, and these mutants were no longer sensitive to growth in the presence of urea. High levels of peroxides, including lipid peroxides, were detected in the bleaching cells. Exogenously added polyunsaturated fatty acids triggered a similar death response. Vitamin E suppressed the formation of peroxides and delayed the onset of cell bleaching. The results suggest that these cyanobacterial cells undergo a metabolic imbalance that ultimately leads to oxidative stress and lipid peroxide formation. These observations may provide insights into the mechanism of sudden cyanobacterial bloom disappearance in nature.
49
Schweizer, Ulrich, Jazmin Chiu e Josef Köhrle. "Peroxides and Peroxide-Degrading Enzymes in the Thyroid". Antioxidants & Redox Signaling 10, n. 9 (settembre 2008): 1577–92. http://dx.doi.org/10.1089/ars.2008.2054.
Testo completo
50
van der Westhuyzen, Christiaan W., Richard K. Haynes, Jenny-Lee Panayides, Ian Wiid e Christopher J. Parkinson. "Anti-Mycobacterial Peroxides: A New Class of Agents for Development Against Tuberculosis". Medicinal Chemistry 16, n. 3 (17 aprile 2020): 392–402. http://dx.doi.org/10.2174/1573406415666190430143535.
Testo completoAbstract (sommario):
Background: With few exceptions, existing tuberculosis drugs were developed many years ago and resistance profiles have emerged. This has created a need for new drugs with discrete modes of action. There is evidence that tuberculosis (like other bacteria) is susceptible to oxidative pressure and this has yet to be properly utilised as a therapeutic approach in a manner similar to that which has proven highly successful in malaria therapy. Objective: To develop an alternative approach to the incorporation of bacterial siderophores that results in the creation of antitubercular peroxidic leads for subsequent development as novel agents against tuberculosis. Methods: Eight novel peroxides were prepared and the antitubercular activity (H37Rv) was compared to existing artemisinin derivatives in vitro. The potential for toxicity was evaluated against the L6 rat skeletal myoblast and HeLa cervical cancer lines in vitro. Results: The addition of a pyrimidinyl residue to an artemisinin or, preferably, a tetraoxane peroxidic structure results in antitubercular activity in vitro. The same effect is not observed in the absence of the pyrimidine or with other heteroaromatic substituents. Conclusion: The incorporation of a pyrimidinyl residue adjacent to the peroxidic function in an organic peroxide results in anti-tubercular activity in an otherwise inactive peroxidic compound. This will be a useful approach for creating oxidative drugs to target tuberculosis.