Journal articles: 'Oxidized system'

1

Hu, Yan Fang, Xiao Dong Zhang, Zhao Guang Nie, Ya Cheng Xing, Bo Qun Lin, and Li Li Song. "Selective Oxidation of Corn Starch in TEMPO-Mediated System." Advanced Materials Research 1051 (October 2014): 221–24. http://dx.doi.org/10.4028/www.scientific.net/amr.1051.221.

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With TEMPO-NaClO-NaBr as the selective oxidation system, the oxidized corn starch was prepared from the corn starch, substituting traditional pre-gelatinized corn starch. The relationship of the carboxyl mass fraction of the oxidized starch and the dosage of oxidant was studied under the conditions such as: the mass of the corn starch was 5.0g, the pH was 10.00, the reaction temperature was 20 °C. The structure of the oxidized corn starch was characterized by IR. The results showed that when the consumption of NaClO was 67.5 mL, the reaction time was 2.5 h, the carboxyl of oxidized starch can reach 10.60%.

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Khodaei, Mohammad Mehdi, Kiumars Bahrami, and Mohammad Khedri. "The efficient and chemoselective MoO3-catalyzed oxidation of sulfides to sulfoxides and sulfones with H2O2." Canadian Journal of Chemistry 85, no. 1 (January 1, 2007): 7–11. http://dx.doi.org/10.1139/v06-177.

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Hydrogen peroxide together with MoO3 as catalyst can efficiently and chemoselectivity oxidize sulfides to sulfoxides and sulfones in the presence of other oxidized functional groups in ethanol at 50 °C in short reaction times.Key words: oxidation, sulfides, sulfoxides, sulfones, H2O2–MoO3 system.

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3

Uetrecht, Jack P. "Myeloperoxidase as a generator of drug free radicals." Biochemical Society Symposia 61 (November 1, 1995): 163–70. http://dx.doi.org/10.1042/bss0610163.

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Reactive metabolites are believed to be responsible for many types of toxicity, including idiosyncratic drug reactions. Bone marrow is a frequent target of idiosyncratic reactions, and, since these reactions have characteristics that suggest involvement of the immune system, the formation of reactive metabolites by leucocytes could also play a role in the aetiology of idiosyncratic drug reactions. The major oxidation system in neutrophils and monocytes is a combination of NADPH oxidase and myeloperoxidase. This system oxidizes primary arylamines, such as sulphonamides, to reactive metabolites and these drugs are also associated with a high incidence of agranulocytosis, generalized idiosyncratic reactions and/ or drug-induced lupus. Clozapine is oxidized by this system to a relatively stable nitrenium ion; clozapine is also associated with a high incidence of agranulocytosis. Arylamines that have an oxygen or nitrogen in the para position, such as amodiaquine, vesnarinone and 5-aminosalicylic acid, are oxidized to quinone-like reactive intermediates. Aminopyrine is oxidized to a very reactive dication. Such reactive metabolites could also inhibit neutrophil function and mediate some of the therapeutic effects of these drugs: for example, the use of dapsone for dermatitis herpetiformis and the use of 5-aminosalicylic acid for inflammatory bowel disease.

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Grisham, M. B., and E. M. Ryan. "Cytotoxic properties of salivary oxidants." American Journal of Physiology-Cell Physiology 258, no. 1 (January 1, 1990): C115—C121. http://dx.doi.org/10.1152/ajpcell.1990.258.1.c115.

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Salivary peroxidase and to a lesser extent myeloperoxidase are present in significant concentrations in saliva and catalyze the oxidation of thiocyanate anion (SCN-) by H2O2 to yield the potent oxidants hypothiocyanous acid (HOSCN) and its conjugate base hypothiocyanite anion (OSCN-). The objective of this study was to characterize the cytotoxic potential of peroxidase-generated HOSCN/OSCN- toward human erythrocytes. We found that HOSCN/OSCN- (0.25 mM) generated by the peroxidase-H2O2-SCN- system caused significant hemolysis at pH 6.0 but not at pH 6.5, 7.0, or 7.4. Erythrocyte hemoglobin (OxyHb) was oxidized to methemoglobin (MetHb) at all pH values tested; however, the rate of MetHb formation was dramatically increased at low pH and was not affected by inosine hexaphosphate, suggesting that hemoglobin was oxidized primarily by HOSCN. Concurrent with oxidation of hemoglobin (Hb), there was a pH-dependent consumption of HOSCN/OSCN- with more of the oxidant consumed at pH 6.0 compared with pH 6.5, 7.0, or 7.4. The enhanced oxidation of Hb at acidic pH was not due simply to increased membrane permeability by the uncharged species (HOSCN), since both erythrocyte lysate Hb and purified Hb were oxidized to the same extent at low pH as were intact erythrocytes. It is concluded that both OSCN- and HOSCN enter human erythrocytes where the protonated oxidant (HOSCN) mediates hemolysis and oxidizes OxyHb to MetHb, whereas both HOSCN and OSCN- oxidize glutathione (GSH). These data suggest that the extracellular pH may play an important role in modulating the cytotoxic properties of salivary oxidants.

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Mattson, Bengt, Bengt Stenberg, Sture Persson, and Erik Östman. "Thermo-Oxidative Degradation of Thick-Walled Rubber Materials Studied by IR-Technique and Computed X-Ray Tomography Scanning." Rubber Chemistry and Technology 63, no. 1 (March 1, 1990): 23–31. http://dx.doi.org/10.5254/1.3538239.

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Abstract Natural rubber cylinders vulcanized with two different systems, TMTD, which is an efficient vulcanizing system (EV system) and S/CBS, which is a conventional system, have been studied with respect to thermo-oxidative aging gradients, by the ATR-IR-technique (attenuated total-reflection infrared spectroscopy), computed x-ray tomography scanning and swelling. Observed aging processes are dominated by the formation of an oxidized layer whose low permeability to oxygen protects the interior of the material from oxidative aging processes as long as it is intact. The time to the formation of the oxidized layer is the major reason for the differences in the aging gradients. The oxidized layer is formed rapidly in the conventional system, whereas the formation is inhibited by dithiocarbamates in the EV system. Oxygen therefore diffuses into the EV materials, giving deeper oxidative aging than in the conventional materials at the same temperature. The conclusion drawn from the results of this study is that an earlier formation of an oxidized layer is advantageous with respect to thermo-oxidative aging of the bulk. Although it must be stated that, due to the better thermal stability of an EV system and to the poor mechanical properties of an oxidized layer, no objection is here raised to the accepted view that an EV system has superior aging properties.

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Liu, G. D., Z. X. Zhao, G. C. Che, J. W. Li, and F. Wu. "Superconducting properties of the oxidized La2−xBaxCuO4 system." Physica C: Superconductivity 282-287 (August 1997): 755–56. http://dx.doi.org/10.1016/s0921-4534(97)00392-4.

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Aksu, Seda, Isabel W. C. E. Arends, and Frank Hollmann. "A New Regeneration System for Oxidized Nicotinamide Cofactors." Advanced Synthesis & Catalysis 351, no. 9 (June 2009): 1211–16. http://dx.doi.org/10.1002/adsc.200900033.

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Canales, Camila, Leyla Gidi, Roxana Arce, Francisco Armijo, María Aguirre, and Galo Ramírez. "Electro-Reduction of Molecular Oxygen Mediated by a Cobalt(II)octaethylporphyrin System onto Oxidized Glassy Carbon/Oxidized Graphene Substrate." Catalysts 8, no. 12 (December 6, 2018): 629. http://dx.doi.org/10.3390/catal8120629.

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The oxygen reduction reaction (ORR) is the most important reaction in life processes and in energy transformation. The following work presents the design of a new electrode which is composed by deposited cobalt octaethylporphyrin onto glassy carbon and graphene, where both carbonaceous materials have been electrochemically oxidized prior to the porphyrin deposition. The novel generated system is stable and has an electrocatalytic effect towards the oxygen reduction reaction, as a result of the significant overpotential shift in comparison to the unmodified electrode and to the electrodes used as target. Kinetic studies corroborate that the system is capable of reducing molecular oxygen via four electrons, with a Tafel slope value of 60 mV per decade. The systems were morphologically characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM) Electrochemical impedance spectroscopy studies showed that the electrode previously oxidized and modified with cobalt porphyrin is the system that possesses lower resistance to charge transfer and higher capacitance.

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9

Mander, Gerd J., Huaming Wang, Elizabeth Bodie, Jens Wagner, Kay Vienken, Claudia Vinuesa, Caroline Foster, et al. "Use of Laccase as a Novel, Versatile Reporter System in Filamentous Fungi." Applied and Environmental Microbiology 72, no. 7 (July 2006): 5020–26. http://dx.doi.org/10.1128/aem.00060-06.

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ABSTRACT Laccases are copper-containing enzymes which oxidize phenolic substrates and transfer the electrons to oxygen. Many filamentous fungi contain several laccase-encoding genes, but their biological roles are mostly not well understood. The main interest in laccases in biotechnology is their potential to be used to detoxify phenolic substances. We report here on a novel application of laccases as a reporter system in fungi. We purified a laccase enzyme from the ligno-cellulolytic ascomycete Stachybotrys chartarum. It oxidized the artificial substrate 2,2′-azino-di-(3-ethylbenzthiazolinsulfonate) (ABTS). The corresponding gene was isolated and expressed in Aspergillus nidulans, Aspergillus niger, and Trichoderma reesei. Heterologously expressed laccase activity was monitored in colorimetric enzyme assays and on agar plates with ABTS as a substrate. The use of laccase as a reporter was shown in a genetic screen for the isolation of improved T. reesei cellulase production strains. In addition to the laccase from S. charatarum, we tested the application of three laccases from A. nidulans (LccB, LccC, and LccD) as reporters. Whereas LccC oxidized ABTS (Km = 0.3 mM), LccD did not react with ABTS but with DMA/ADBP (3,5-dimethylaniline/4-amino-2,6-dibromophenol). LccB reacted with DMA/ADBP and showed weak activity with ABTS. The different catalytic properties of LccC and LccD allow simultaneous use of these two laccases as reporters in one fungal strain.

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Kooti, Mohammad, and Mehdi Jorfi. "Mild and Efficient Oxidation of Aromatic Alcohols and Other Substrates Using NiO2/CH3COOH System." E-Journal of Chemistry 5, no. 2 (2008): 365–69. http://dx.doi.org/10.1155/2008/826184.

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A variety of aromatic alcohols were efficiently oxidized to their corresponding aldehydes and ketones in good to excellent yields using nickel peroxide activated by acetic acid. Some thiols and amines were also readily oxidized by this oxidant under mild conditions.

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Rencoret, Jorge, Antonio Pereira, Gisela Marques, José Carlos del Río, Ángel T. Martínez, and Ana Gutiérrez. "A commercial laccase-mediator system to delignify and improve saccharification of the fast-growing Paulownia fortunei (Seem.) Hemsl." Holzforschung 73, no. 1 (December 19, 2018): 45–54. http://dx.doi.org/10.1515/hf-2018-0095.

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Abstract It was demonstrated for the first time that a laccase-based enzymatic pretreatment is able to delignify fast-growing paulownia species. The treatment was performed with a commercial low-redox potential laccase isolated from Myceliophthora thermophila (Apinis) Oorschot and methyl syringate (MeS) as a natural phenolic mediator. Up to 24% lignin removal was attained by the laccase-MeS treatment (L/MeS), followed by alkaline peroxide extraction in a multistage sequence. The reduction in lignin content was accompanied by a significant improvement in the subsequent enzymatic saccharification, with increases of up to 38% glucose and 34% xylose yields. The structural modifications of the lignin were analyzed in situ by two dimensional-nuclear magnetic resonance (2D-NMR) spectroscopy. A considerable removal of guaiacyl and syringyl lignin units with respect to the carbohydrate signals was visible as well as the cleavage of β-O-4′, β-5′ and β-β′ linkages leading to elevated amounts of Cα-oxidized guaiacyl and syringyl units. The presence of oxidized lignin compounds in the filtrates of the enzymatic treatments – such as vanillin, vanillic acid, syringaldehyde and syringic acid – conclusively demonstrates the ability of L/MeS treatment to oxidize and depolymerize the lignin in paulownia wood.

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12

Davies, P. K., and C. M. Katzan. "Oxidation, reduction, and stability of the BaLa4Cu5O13±δ system." Proceedings, annual meeting, Electron Microscopy Society of America 47 (August 6, 1989): 162–63. http://dx.doi.org/10.1017/s0424820100152781.

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The electronic and structural properties of most of the high temperature superconducting copper oxides are highly dependent upon the oxidation conditions used to prepare the cuprate compounds. Until recently superconductivity had only been observed in highly oxidized compounds, however recent work has shown that under certain circumstances superconducting transitions can also occur in n-doped, reduced cuprates. In an effort to understand some of the chemical factors that lead to the stabilization of both oxidized and reduced cuprates, we have investigated the stability of several cuprates. In this paper we report our results on the metallic, non-superconducting BaLa4Cu5O13±δ (“145”) system.At high temperature most of the highly oxidized cuprates are reduced as oxygen is reversibly removed from the perovskite lattice and the Cu valence is lowered to ≤ 2. However, for compounds with the 145 stoichiometry there is no significant oxygen loss in “non-reactive” gases such as air, O2 or He, and even at 1000°C Cu is apparently stable in a valence state greater than 2.3+.

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Lerner, Natalie, Itay Chen, Sofia Schreiber-Avissar, and Elie Beit-Yannai. "Extracellular Vesicles Mediate Anti-Oxidative Response—In Vitro Study in the Ocular Drainage System." International Journal of Molecular Sciences 21, no. 17 (August 25, 2020): 6105. http://dx.doi.org/10.3390/ijms21176105.

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The importance of extracellular vesicles (EVs) as signaling mediators has been emphasized for several pathways with only limited data regarding their role as protective messages during oxidative stress (OS). The ocular drainage system is unique by being continuously exposed to OS and having a one-way flow of the aqueous humor carrying EVs taking role in glaucoma disease. Here, we aimed to examine the ability of EVs derived from the non-pigmented ciliary epithelium (NPCE)—the aqueous humor producing cells exposed to OS—to deliver protecting messages to the trabecular meshwork (TM)—the aqueous humor draining cells—a process with significance to the pathophysiology of glaucoma disease. EVs extracted from media of NPCE cells exposed to non-lethal OS and their unstressed control were incubated with TM cells. The effects of EVs derived from oxidative stressed cells on the activation of the nuclear factor erythroid 2-related factor 2-Kelch-like ECH-associated protein 1 (Nrf2-Keap1), a major OS pathway, and of the Wnt pathway, known for its role in primary open-angle glaucoma, were evaluated. EVs derived from oxidized NPCE cells significantly protected TM cells from direct OS. The TM cells uptake of EVs from oxidized NPCE and their cytosolic Nrf2 levels were significantly higher at 8 h post-exposure. EVs derived from oxidized NPCE cells significantly attenuated Wnt protein expression in TM cells and activated major antioxidant genes as measured by qRT-PCR. TM cells exposed to EVs derived from oxidized NPCE cells exhibited significantly lower OS and higher super oxide dismutase and catalase activity. Finally, we were able to show that carbonylated proteins and products of oxidized protein are presented in significantly higher levels in EVs derived from oxidized NPCE cells, supporting their suggested role in the signaling process. We hypothesize that these findings may have implications beyond understanding the pathophysiology of glaucoma disease and that transmitting signals that activate the antioxidant system in target cells represent a broad response common to many tissues communication.

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Magacz, Marcin, Maria Oszajca, Izabela Nawrot-Hadzik, Ryszard Drożdż, Anna Jurczak, Jakub Hadzik, Aleksander Smakosz, and Wirginia Krzyściak. "Phenolic Compounds of Reynoutria sp. as Modulators of Oral Cavity Lactoperoxidase System." Antioxidants 10, no. 5 (April 26, 2021): 676. http://dx.doi.org/10.3390/antiox10050676.

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Lactoperoxidase (LPO) together with its (pseudo)halogenation cycle substrates, H2O2 and thiocyanate ions oxidized to hypothiocyanite ions, form one of the main systems involved in antimicrobial defense within the oral cavity. In bacterial diseases such as dental caries, lactoperoxidase is oxidized to a form known as Compound II, which is characterized by its inability to oxidize SCN–, resulting in a decreased generation of antimicrobial products. Reynoutria sp. rizome extracts, due to their high polyphenol content, have been tested as a source of compounds able to regenerate the antimicrobial activity of lactoperoxidase through converting the Compound II to the native LPO state. In the presented study, acetone extracts of R. japonica, R. sachalinensis, and R. x bohemica, together with their five fractions and four selected polyphenols dominating in the studied in extracts, were tested toward lactoperoxidase reactivating potential. For this purpose, IC50, EC50, and activation percentage were determined by Ellman’s method. Furthermore, the rate constants for the conversion of Compound I–Compound II and Compound II–native-LPO in the presence of extracts, extracts fractions, and selected polyphenols were determined. Finally, the ability to enhance the antimicrobial properties of the lactoperoxidase system was tested against Streptococcus mutans. We proved that Reynoutria sp. rhizome is the source of lactoperoxidase peroxidation cycle substrates, which can act as activators and inhibitors of the antimicrobial properties of that system. The presented study shows that the reactivation of lactoperoxidase could become a potential therapeutic target in prevention and treatment support in some infectious oral diseases.

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Jones, Colleen P., Seth N. Lyman, Daniel A. Jaffe, Tanner Allen, and Trevor L. O'Neil. "Detection and quantification of gas-phase oxidized mercury compounds by GC/MS." Atmospheric Measurement Techniques 9, no. 5 (May 18, 2016): 2195–205. http://dx.doi.org/10.5194/amt-9-2195-2016.

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Abstract. Most mercury pollution is emitted to the atmosphere, and the location and bioavailability of deposited mercury largely depends on poorly understood atmospheric chemical reactions that convert elemental mercury into oxidized mercury compounds. Current measurement methods do not speciate oxidized mercury, leading to uncertainty about which mercury compounds exist in the atmosphere and how oxidized mercury is formed. We have developed a gas chromatography/mass spectrometry (GC-MS)-based system for identification and quantification of atmospheric oxidized mercury compounds. The system consists of an ambient air collection device, a thermal desorption module, a cryofocusing system, a gas chromatograph, and an ultra-sensitive mass spectrometer. It was able to separate and identify mercury halides with detection limits low enough for ambient air collection (90 pg), but an improved ambient air collection device is needed. The GC/MS system was unable to quantify HgO or Hg(NO3)2, and data collected cast doubt upon the existence of HgO in the gas phase.

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Yang, Hua, Pei Pei Meng, Rui Wang, Pei Ran Li, Peng Li, Chang Lu Wang, and Li Zhen Ma. "Effect of Oxidized Myofibrils Protein Subjected to Mutiple Freeze-Thaw Cycles on N-Nitrosamine Formation in In Vitro Model System." Advanced Materials Research 550-553 (July 2012): 1590–94. http://dx.doi.org/10.4028/www.scientific.net/amr.550-553.1590.

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N-nitrosamine is a kind of carcinogenic substance, which is possibly formed in the reaction of nitrites with amino acids or secondary amines. Two in vitro model systems were designed to evaluate the influence of oxidized myofibrils protein subjected to repeated freeze-thaw cycles (0, 1, 2, 3, 4, 7, 10 times) on N-nitrosamine formation. Model system I contains diethylamine and sodium nitrite, while model system II contains only sodium nitrite as reaction solution. Oxidized myofibrils protein were added to both systems. The results revealed that as the number of freeze-thaw cycles increased, cross-linking of myosin heavy chains and the content of protein carbonyl increased, but the content of protein sulfydryl decreased, which indicates oxidization of protein occurred. The concentration of N-nitrosodiethylamine increased as the number of freeze-thaw cycles increased, especially after four cycles. Oxidized myofibrils protein promoted the formation of N-nitrosodiethylamine. The more the times of freeze-thaw cycles were subjected, the more oxidization of myofibrils protein occurred and the higher yield of the N-nitrosodiethylamine.

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Tramutola, Antonella, Fabio Di Domenico, Eugenio Barone, Marzia Perluigi, and D. Allan Butterfield. "It Is All about (U)biquitin: Role of Altered Ubiquitin-Proteasome System and UCHL1 in Alzheimer Disease." Oxidative Medicine and Cellular Longevity 2016 (2016): 1–12. http://dx.doi.org/10.1155/2016/2756068.

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Free radical-mediated damage to macromolecules and the resulting oxidative modification of different cellular components are a common feature of aging, and this process becomes much more pronounced in age-associated pathologies, including Alzheimer disease (AD). In particular, proteins are particularly sensitive to oxidative stress-induced damage and these irreversible modifications lead to the alteration of protein structure and function. In order to maintain cell homeostasis, these oxidized/damaged proteins have to be removed in order to prevent their toxic accumulation. It is generally accepted that the age-related accumulation of “aberrant” proteins results from both the increased occurrence of damage and the decreased efficiency of degradative systems. One of the most important cellular proteolytic systems responsible for the removal of oxidized proteins in the cytosol and in the nucleus is the proteasomal system. Several studies have demonstrated the impairment of the proteasome in AD thus suggesting a direct link between accumulation of oxidized/misfolded proteins and reduction of this clearance system. In this review we discuss the impairment of the proteasome system as a consequence of oxidative stress and how this contributes to AD neuropathology. Further, we focus the attention on the oxidative modifications of a key component of the ubiquitin-proteasome pathway, UCHL1, which lead to the impairment of its activity.

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Germanenko, I. N., M. Dongol, Y. B. Pithawalla, M. Samy El-Shall, and J. A. Carlisle. "Effect of atmospheric oxidation on the electronic and photoluminescence properties of silicon nanocrystal." Pure and Applied Chemistry 72, no. 1-2 (January 1, 2000): 245–55. http://dx.doi.org/10.1351/pac200072010245.

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Web-like aggregates of coalesced Si nanocrystals produced by a laser vaporization-controlled condensation technique show luminescence properties that are similar to those of porous Si. The results are consistent with a quantum confinement mechanism as the source of the red photoluminescence (PL) in this system. The oxidized Si nanoparticles do not exhibit the red PL that is characteristic of the surface-oxidized Si nanocrystals. The nanoparticles are allowed to oxidize slowly, and the PL is measured as a function of the exposure time in air. A significant blue shift in the red PL peak is observed as a result of the slow oxidation process. The dependence of quantum size effects on the bonding structure is established by correlating the PL data with the photon-yield electronic structure measurements made at the Advanced Light Source. The results indicate that as the nanoparticles oxidize, the radius of the crystalline core decreases in size, which gives rise to a larger bandgap and consequently to the observed blue-shift in the PL band. The correlation between the PL, SXF, and NEXAFS results provides further support for the quantum confinement mechanism as the origin of the visible PL in Si nanocrystals.

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Sherwood, Peter M. A., Ian D. Welsh, and David M. Hercules. "Surface Studies of the Nickel Electrode System Using a Special Transfer Cell." Applied Spectroscopy 42, no. 4 (May 1988): 658–66. http://dx.doi.org/10.1366/0003702884429337.

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Nickel metal with an unoxidized and an electrochemically oxidized surface can be transferred considerable distances between vacuum systems, without significant surface change, in an anaerobic cell for study by various surface science methods (XPS, Auger, ISS, and SIMS). The SIMS and ISS spectra are very sensitive to hydrocarbon contamination, which can be nearly eliminated by using the transfer cell. Complementary information is obtained using these surface analytical methods. Electrochemically oxidized nickel metal samples show the presence of oxide and hydroxide species. The results are compared with spectral data for a number of nickel compounds.

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Kolesnikova, L. I., O. A. Vanteeva, N. A. Kurashova, and B. Ya Vlasov. "GLUTATHION AS AN IMPORTANT COMPONENT OF THIOSULFID SYSTEM OF INFERTILITY PATHOGENESIS IN OVERWEIGHT MEN." Annals of the Russian academy of medical sciences 68, no. 7 (July 19, 2013): 9–12. http://dx.doi.org/10.15690/vramn.v68i7.705.

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Aim: to study the glutathionic part of thiosulfid system and oxidative stress in infertile men with different body mass index. Patients and methods: examined 60 infertile men with normal and overweight, and 40 healthy men with proven fertility. Active components of the antioxidant defense system of the body was assessed by the level of reduced and oxidized glutathione by the method of PY Hissin, determination of TBA-active products was carried out by the method VB Gavrilova. In the analysis of inter-group differences for independent samples was used parametric Student criterion. Results: the oxidative stress in obese men was characterized by significant elevation of oxidized form of glutathione (GSSG) in comparison with its reduced form. We discussed our results in the context of GSSG «quantivalence» to numerous of cellular processes in the setting of metabolic disorders in infertile and obese men. The ratio of reduced glutathione to oxidized infertile men decreased by 1,5 times in patients with obesity and 1,2 times in those with normal body mass index. Conclusions: Glutathione is the most important link in the study of oxidative stress in men with infertility. Raising the level of oxidized glutathione is due to the presence of his additional functions that are implemented at higher values of body mass index, especially in association with infertility.

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Avdeenko, A. P., Yu P. Kholmovoi, and A. L. Yusina. "REDOX PROCESSES IN THE REACTIONS OF N-ARYLSULFONYL-1,4-NAPHTНOQUINONЕIMINES WITH CERTAIN NUCLEOPHILES." Odesa National University Herald. Chemistry 26, no. 3(79) (November 24, 2021): 55–62. http://dx.doi.org/10.18524/2304-0947.2021.3(79).240753.

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Quinone-hydroquinone pairs are prototypes of organic redox systems, and studies of the electrochemical behavior of these compounds are of great interest for research. Electrochemical behavior associated with the equilibrium of electron-proton transfer provides information about the molecular structure and environment of the process. Apart from chemical aspects, quinones play an important role in the biochemistry of living cells. Quinone derivatives, used as drugs for several types of human cancers, have been found to have their biological activity related to their redox behavior. Quinoneimines-aminophenols form similar pairs. In nucleophilic addition reactions of N‑substituted p-quinoneimines, parallel redox processes are often observed, and the higher the redox potential of quinoneimine, the greater the likelihood of such processes. Naphthoquinoneimines with aromatic amines and acylhydrazines follow the scheme of 1,4-addition, but as reaction products are oxidized products -4-arylsulfonylamido‑2-arylamino(2-aroylamino)-1,4-naphthoquinoneimines. The oxidant may be the original naphthoquinoneimine and oxygen. Studies have shown that oxygen in the reaction of 1,4-naphthoquinoneimines with acylhydrazines is the only oxidant that oxidizes the product of 1,4-addition, as evidenced by the study of redox potentials. Both oxidized and reduced form of the compounds, as naphthoquinoneimine and the corresponding aminonaphthol, are used to determine the redox potential by direct potentiometry. Due to the instability of the reduced form in the case of the pair naphthoquinoneimine-aminonaphthol, we used only the reduced form, which is oxidized in the cell by oxygen. The redox potential of the naphthoquinoneimine-aminonaphthol galvanic pair was determined as the average value between the potential Emax, which was established in the system upon complete oxidation of the starting substance, that is, when only naphthoquinone imine remains in the system, and the potential Emin, which was registered at the beginning of the process in the system with the reduced form – the corresponding aminonaphthol. This is the method of direct potentiometry in the variant of the middle potential.

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Friguet, Bertrand. "Protein Repair and Degradation during Aging." Scientific World JOURNAL 2 (2002): 248–54. http://dx.doi.org/10.1100/tsw.2002.98.

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Cellular aging is characterized by a build-up of oxidatively modified proteins. The steady-state level of oxidized proteins depends on the balance between the rate of protein oxidative damage and the rates of protein degradation and repair. Therefore, the accumulation of oxidized protein with age can be due to increased protein damage, decreased oxidized protein degradation and repair, or the combination of both mechanisms. The proteasomal system is the major intracellular proteolytic pathway implicated in the degradation of oxidized protein, and the peptide methionine sulfoxide reductase catalyzes the reduction of methionine sulfoxide (i.e., oxidized methionine) to methionine within proteins. A short summary on protein oxidative damage and oxidized protein degradation is given, and evidence for a decline of proteasome function with age is presented. Arguments for the implication of peptide methionine sulfoxide reductase in the age-related accumulation of oxidized protein are also discussed.

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Serikbayeva, A. K., K. Zh Zhumashev, F. A. Berdikulova, and Sh K. Akilbekova. "STUDY OF PHASE TRANSFORMATIONS IN OXIDIZED COPPER ORE – SULFUR SYSTEM." Izvestiya Vuzov Tsvetnaya Metallurgiya (Proceedings of Higher Schools Nonferrous Metallurgy, no. 5 (November 4, 2017): 34–41. http://dx.doi.org/10.17073/0021-3438-2017-5-34-41.

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Costa Pessoa, J., I. Tomaz, T. Kiss, and P. Buglyó. "The system VO2++oxidized glutathione: a potentiometric and spectroscopic study." Journal of Inorganic Biochemistry 84, no. 3-4 (April 2001): 259–70. http://dx.doi.org/10.1016/s0162-0134(00)00233-6.

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GROSSMAN, Lawrence, Alexei V. FEDKIN, and Steven B. SIMON. "Formation of the first oxidized iron in the solar system." Meteoritics & Planetary Science 47, no. 12 (July 9, 2012): 2160–69. http://dx.doi.org/10.1111/j.1945-5100.2012.01353.x.

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Tetik, Sermin, Kurtulus Kaya, and Turay Yardimci. "Effect of Oxidized Fibrinogen on Hemostatic System: In Vitro Study." Clinical and Applied Thrombosis/Hemostasis 17, no. 3 (June 7, 2010): 259–63. http://dx.doi.org/10.1177/1076029610363129.

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Lourenço dos Santos, Sofia, Isabelle Petropoulos, and Bertrand Friguet. "The Oxidized Protein Repair Enzymes Methionine Sulfoxide Reductases and Their Roles in Protecting against Oxidative Stress, in Ageing and in Regulating Protein Function." Antioxidants 7, no. 12 (December 12, 2018): 191. http://dx.doi.org/10.3390/antiox7120191.

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Cysteine and methionine residues are the amino acids most sensitive to oxidation by reactive oxygen species. However, in contrast to other amino acids, certain cysteine and methionine oxidation products can be reduced within proteins by dedicated enzymatic repair systems. Oxidation of cysteine first results in either the formation of a disulfide bridge or a sulfenic acid. Sulfenic acid can be converted to disulfide or sulfenamide or further oxidized to sulfinic acid. Disulfide can be easily reversed by different enzymatic systems such as the thioredoxin/thioredoxin reductase and the glutaredoxin/glutathione/glutathione reductase systems. Methionine side chains can also be oxidized by reactive oxygen species. Methionine oxidation, by the addition of an extra oxygen atom, leads to the generation of methionine sulfoxide. Enzymatically catalyzed reduction of methionine sulfoxide is achieved by either methionine sulfoxide reductase A or methionine sulfoxide reductase B, also referred as to the methionine sulfoxide reductases system. This oxidized protein repair system is further described in this review article in terms of its discovery and biologically relevant characteristics, and its important physiological roles in protecting against oxidative stress, in ageing and in regulating protein function.

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Mun, Ji Eun, Woo Joong Kim, Jeung Ri Kong, and Nam Jin Kim. "Effects of Nano Particles Attached onto a Heat Transfer Surface in the Thermal-Hydraulic System." Key Engineering Materials 775 (August 2018): 127–31. http://dx.doi.org/10.4028/www.scientific.net/kem.775.127.

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This work experimentally explored the influence of nano-fouling, and it was also compared and analyzed CHF, flow boiling heat transfer coefficient, contact angle, and surface roughness. The working fluids in this study were used as purewater and a 0.01 vol% oxidized MWCNT nanofluid. The flow velocity conditions are established at 0.5, 1.0, and 1.5 m/s. Also, the nanoparticles of oxidized graphene were deposited on a heat transfer surface, and artificial spray coating times for nano-fouling are established at 0, 120, 180, and 240 sec. As the results, it was found that the superheated temperature to the CHF extremely increased in case of nano-fouling, it is caused by physical damage of heat transfer system. The flow boiling heat transfer coefficient in an oxidized graphene nanofluid increased up to 24.29% without any treatment on the heat transfer surface, but the coefficient in case of nano-fouling decreased down to 16.26% more than in the purewater.

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Bihlmaier, Karl, Nikola Mesecke, Nadia Terziyska, Melanie Bien, Kai Hell, and Johannes M. Herrmann. "The disulfide relay system of mitochondria is connected to the respiratory chain." Journal of Cell Biology 179, no. 3 (October 29, 2007): 389–95. http://dx.doi.org/10.1083/jcb.200707123.

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All proteins of the intermembrane space of mitochondria are encoded by nuclear genes and synthesized in the cytosol. Many of these proteins lack presequences but are imported into mitochondria in an oxidation-driven process that relies on the activity of Mia40 and Erv1. Both factors form a disulfide relay system in which Mia40 functions as a receptor that transiently interacts with incoming polypeptides via disulfide bonds. Erv1 is a sulfhydryl oxidase that oxidizes and activates Mia40, but it has remained unclear how Erv1 itself is oxidized. Here, we show that Erv1 passes its electrons on to molecular oxygen via interaction with cytochrome c and cytochrome c oxidase. This connection to the respiratory chain increases the efficient oxidation of the relay system in mitochondria and prevents the formation of toxic hydrogen peroxide. Thus, analogous to the system in the bacterial periplasm, the disulfide relay in the intermembrane space is connected to the electron transport chain of the inner membrane.

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Matthews, D., A. Altus, and A. Hope. "Photochemical Electron Transfer in the System Polypyrrole-Methylene Blue." Australian Journal of Chemistry 47, no. 6 (1994): 1163. http://dx.doi.org/10.1071/ch9941163.

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Methylene Blue incorporated into colloidal oxidized polypyrrole was investigated by absorption spectroscopy and laser flash photolysis. The absorption spectra of Methylene Blue and polypyrrole were unaffected by incorporation. Flash photolysis transients of Methylene Blue and triplet Methylene Blue in ethanol were affected by 1,4-benzoquinone and 1,4-benzoquinol but not by the long-chain naphthoquinone Vitamin K1. Incorporation of Methylene Blue in polypyrrole produced distinct changes in the flash photolysis transients of Methylene Blue and triplet Methylene Blue. Very long-lived transients, with lifetimes of the order of 10 ms, were observed. These effects were accompanied by long-lived changes in the absorption spectrum of Methylene Blue. The transients were modified by the addition of 1,4-benzoquinone but not 1,4-benzoquinol. The results indicate photochemical reduction of oxidized polypyrrole by triplet Methylene Blue with the production of stable long-lived species capable of reducing 1,4-benzoquinone.

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Alguacil, Francisco J., Irene García-Díaz, Esther Escudero Baquero, Olga Rodríguez Largo, and Félix A. López. "Oxidized and Non-Oxidized Multiwalled Carbon Nanotubes as Materials for Adsorption of Lanthanum(III) Aqueous Solutions." Metals 10, no. 6 (June 8, 2020): 765. http://dx.doi.org/10.3390/met10060765.

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The behavior of oxidized and non-oxidized multiwalled carbon nanotubes (MWCNTs) in the adsorption of lanthanum(III) from aqueous solutions is described. Metal uptake is studied as a function of several variables such as the stirring speed of the system, pH of the aqueous solution and metal and nanomaterial concentrations. The experimental results are fitted to various kinetic and isotherm models, the rate law being fitted to the film diffusion and particle diffusion models, when the non-oxidized and the oxidized nanomaterials are used to remove lanthanum from the solution, respectively. Sulfuric acid solutions seem to be appropriate to recover the metal from La-loaded nanomaterials.

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Zhang, Chi, Xiao Dong Jia, Ya Lin Lu, Dian Wen Liu, and Xiao Lin Zhang. "Review on New Process and New Reagent of Copper Oxide." Advanced Materials Research 1010-1012 (August 2014): 1618–21. http://dx.doi.org/10.4028/www.scientific.net/amr.1010-1012.1618.

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The paper briefly analyzes and systematically summarizes flotation process and chemical treatment method of low-grade oxidized copper ores in recent years. The new high-efficient collectors and system of reagent combined usage are developed widely and have become an important research direction of oxidized copper ores.

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Zingg, Jean-Marc, Adelina Vlad, and Roberta Ricciarelli. "Oxidized LDLs as Signaling Molecules." Antioxidants 10, no. 8 (July 26, 2021): 1184. http://dx.doi.org/10.3390/antiox10081184.

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Levels of oxidized low-density lipoproteins (oxLDLs) are usually low in vivo but can increase whenever the balance between formation and scavenging of free radicals is impaired. Under normal conditions, uptake and degradation represent the physiological cellular response to oxLDL exposure. The uptake of oxLDLs is mediated by cell surface scavenger receptors that may also act as signaling molecules. Under conditions of atherosclerosis, monocytes/macrophages and vascular smooth muscle cells highly exposed to oxLDLs tend to convert to foam cells due to the intracellular accumulation of lipids. Moreover, the atherogenic process is accelerated by the increased expression of the scavenger receptors CD36, SR-BI, LOX-1, and SRA in response to high levels of oxLDL and oxidized lipids. In some respects, the effects of oxLDLs, involving cell proliferation, inflammation, apoptosis, adhesion, migration, senescence, and gene expression, can be seen as an adaptive response to the rise of free radicals in the vascular system. Unlike highly reactive radicals, circulating oxLDLs may signal to cells at more distant sites and possibly trigger a systemic antioxidant defense, thus elevating the role of oxLDLs to that of signaling molecules with physiological relevance.

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Ohwaki, T., and H. Ishida. "Optimization of the Surface Characterization of Carbon Fiber by FT-IR Internal Reflection Spectroscopy." Applied Spectroscopy 49, no. 3 (March 1995): 341–48. http://dx.doi.org/10.1366/0003702953963634.

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Infrared spectra of surface-oxidized carbon fibers have been obtained with different angles of incidence, polarization states, and internal reflection elements (IREs) to find the optimal condition by internal reflection spectroscopy. It has been found that the maximum peak area of a surface functional group is obtained by using s-polarized light at a 30° angle of incidence for the multiple reflection technique. However, the highest signal-to-noise ratio is observed if unpolarized light is used. Spectral simulations have been performed to understand the observed spectra of the surface-oxidized carbon fibers according to exact optical theory. In the spectral simulations, Fresnel's three-layered system has been adopted to model the “IRE/oxidized layer/bulk of carbon fiber” system.

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D’Ambro, Emma L., Noora Hyttinen, Kristian H. Møller, Siddharth Iyer, Rasmus V. Otkjær, David M. Bell, Jiumeng Liu, et al. "Pathways to Highly Oxidized Products in the Δ3-Carene + OH System." Environmental Science & Technology 56, no. 4 (February 4, 2022): 2213–24. http://dx.doi.org/10.1021/acs.est.1c06949.

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Johnson, Erika L., and Michael R. Hyman. "Propane and n-Butane Oxidation by Pseudomonas putida GPo1." Applied and Environmental Microbiology 72, no. 1 (January 2006): 950–52. http://dx.doi.org/10.1128/aem.72.1.950-952.2006.

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ABSTRACT Propane and n-butane inhibit methyl tertiary butyl ether oxidation by n-alkane-grown Pseudomonas putida GPo1. Here we demonstrate that these gases are oxidized by this strain and support cell growth. Both gases induced alkane hydroxylase activity and appear to be oxidized by the same enzyme system used for the oxidation of n-octane.

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Rungrodnimitchai, Supitcha, Sirinapa Mayod, Suphatra Hiranphinyophat, Ditpon Kotatha, and Chittra Dokbua. "Oxidized Cellulose Nanofiber for Hemostatic Materials." Key Engineering Materials 792 (December 2018): 80–85. http://dx.doi.org/10.4028/www.scientific.net/kem.792.80.

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In this study, oxidized cellulose nanofiber was prepared from squeeze dried Nata de Coco sheet by the oxidation system of HNO3/H3PO4-NaNO2 at 30 °C for 24 hours. The ratio between HNO3 and H3PO4 was 1:3 v/v and the concentration of NaNO2 was 1.4% w/v. The carboxyl content and %yield of oxidized cellulose nanofiber from Nata de Coco (Nata-OC) was 28.6% and 68.4%, respectively. Then the Nata-OC was treated by several types of bases. Sodium hydroxide (NaOH) or triethanolamine (TEA) treated Nata-OC showed superior in gelation property to the original Nata-OC. The powder of base-treated Nata-OC gave stable Nata-OC aqueous dispersion, which might be applicable for spray-typed materials. The test papers obtained from 10% of base-treated Nata-OC dispersion showed good blood agglutinating property as same as dry sheet of pure Nata-OC. Moreover, the dispersion of base-treated Nata-OC could be coated on the surface of gauze without any additive.

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Roy, H. N., Pijush K. Roy, SA Shumi, MM Rahman, and MN Islam. "Smooth Dearomatization of Some Phenols by BAIB and Facile Aerial Oxidation of Two γ-Hydrogen Containing Anthraquinones." Journal of the Bangladesh Chemical Society 25, no. 1 (September 2, 2012): 21–29. http://dx.doi.org/10.3329/jbcs.v25i1.11767.

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At ambient condition bis(acetoxy)iodo benzene (BAIB) oxidized phenol and substituted phenols and the oxidized products undergo easy annulation reaction with cyanophthalide at ice cold temperature. Methyl or ethyl group at position C-1 in anthraquinone system has participated smooth aerial oxidation under sunlight. DOI: http://dx.doi.org/10.3329/jbcs.v25i1.11767 Journal of Bangladesh Chemical Society, Vol. 25(1), 21-29, 2012

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Shchapin, Igor Yu, Andrey I. Nekhaev, Dzhamalutdin N. Ramazanov, Mohammed Al-Yusufi, Vadim O. Samoilov, and Anton L. Maximov. "Hydrocarbon Oxidation Depth: H2O2/Cu2Cl4·2DMG/CH3CN System." Catalysts 12, no. 4 (April 7, 2022): 409. http://dx.doi.org/10.3390/catal12040409.

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The oxidation of hydrocarbons of different structures under the same conditions is an important stage in the study of the chemical properties of both the hydrocarbons themselves and the oxidation catalysts. In a 50% H2O2/Cu2Cl4·2DMG/CH3CN system, where DMG is dimethylglyoxime (Butane-2,3-dione dioxime), at 50 °C under the same or similar conditions, we oxidized eleven RH hydrocarbons of different structures: mono-, bi- and tri-cyclic, framework and aromatic. To compare the composition of the oxidation products of these hydrocarbons, we introduced a new quantitative characteristic, “distributive oxidation depth D(O), %” and showed the effectiveness of its application. The adiabatic ionization potentials (AIP) and the vertical ionization potentials (VIP) of the molecules of eleven oxidized and related hydrocarbons were calculated using the DFT method in the B3LYP/TZVPP level of theory for comparison with experimental values and correlation with D(O). The same calculations of AIP were made for the molecules of the oxidant, solvent, DMG, related compounds and products. It is shown that component X, which determines the mechanism of oxidation of hydrocarbons RH with AIP(Exp) ≥ AIP(X) = 8.55 ± 0.03 eV, is a trans-DMG molecule. Firstly theoretically estimated experimental values of AIP(trans-DMG) = 8.53 eV and AIP(cis-DMG) = 8.27 eV.

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Weih, Markus, Marion Schmitt, Janette Gieche, Christoph Harms, Karsten Ruscher, Ulrich Dirnagl, and Tilman Grune. "Proteolysis of Oxidized Proteins after Oxygen–Glucose Deprivation in Rat Cortical Neurons is Mediated by the Proteasome." Journal of Cerebral Blood Flow & Metabolism 21, no. 9 (September 2001): 1090–96. http://dx.doi.org/10.1097/00004647-200109000-00006.

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Oxidative injury contributes to cellular damage during and after cerebral ischemia. However, the downstream catabolic pathways of damaged cellular components in neurons are largely unknown. In the current study, the authors examined the formation of oxidized proteins and their active degradation by the proteasome. In near-pure rat primary cortical neurons, it was found that protein-bound carbonyls as markers for oxidized proteins are increased after oxygen-glucose deprivation (OGD). During and after OGD, degradation of proteins metabolically radiolabeled before OGD increases two-to threefold compared with the normal protein turnover. Proteolysis after reoxygenation was attenuated by the presence of dimethylthiourea, a radical scavenger, and was blocked by lactacystin, a specific proteasome inhibitor. Lactacystin also increased the amount of protein carbonyls formed. In contrast, the activity of the proteasome complex itself after OGD was not different from sham-washed controls. The authors suggest that oxygen-glucose deprivation increases free radicals, which, in turn, oxidize proteins that are recognized and actively degraded by the proteasome complex. This protease itself is relatively resistant against oxidative injury. The authors conclude that the proteasome may be an active part of the cellular defense system against oxidative stress after cerebral ischemia.

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Yang, Chunxia, Wei Zhao, Zhiguo Cheng, Baomin Luo, and Dongqin Bi. "Catalytic system for pyridine oxidation to N-oxides under mild conditions based on polyoxomolybdate." RSC Advances 5, no. 46 (2015): 36809–12. http://dx.doi.org/10.1039/c5ra05196g.

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A reusable and effective catalytic system has been developed for oxidation of pyridines catalyzed by Keplerate polyoxomolybdate ({Mo₁₃₂}) at room temperature. Pyridine compounds could be oxidized in high yields under mild conditions.

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Elghali, Abdellatif, Mostafa Benzaazoua, Bruno Bussière, and Thomas Genty. "Spatial Mapping of Acidity and Geochemical Properties of Oxidized Tailings within the Former Eagle/Telbel Mine Site." Minerals 9, no. 3 (March 14, 2019): 180. http://dx.doi.org/10.3390/min9030180.

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At some orphaned and abandoned mine sites, acid mine drainage can represent a complex challenge due to the advanced tailings’ oxidation state as well as the combination of other factors. At the field scale, several parameters control sulfides’ oxidation rates and, therefore, the acidity generation. The objective of this paper is to map the acidity and geochemical properties of oxidized tailings within a closed tailings storage facility. Based on systematic sampling, various geochemical parameters were measured within the oxidized Joutel tailings, including the: Neutralization potential, acid-generating potential, net neutralization potential, neutralization potential ratio, paste pH, thickness of oxidized, hardpan, and transition zones. The different parameters were integrated in geographical information system (GISs) databases to quantify the spatial variability of the acidity and geochemical properties of oxidized tailings. The oxidized tailings were characterized by low sulfide (mainly as pyrite) and carbonate (mainly as siderite/ankerite) contents compared to unweathered tailings. Acidic zones, identified based on paste pH, were located in the eastern portion of the southern zone and at the northern tip of the northern zone.

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Dille, Sara A., Kyle J. Colston, Stephen C. Ratvasky, Jingzhi Pu, and Partha Basu. "Interligand communication in a metal mediated LL′CT system – a case study." RSC Advances 11, no. 39 (2021): 24381–86. http://dx.doi.org/10.1039/d1ra04716g.

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The interligand communication between non-innocent dithiolene ligands of different oxidation states has been described in a Mo system. The fully reduced ene-dithiolate (Dt²⁻) acts as a donor moiety to the oxidized dithione (Dt⁰) in an LL′CT process.

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Han, D. W., J. S. Chang, and D. J. Kim. "Nitrifying microbial community analysis of nitrite accumulating biofilm reactor by fluorescence in situ hybridization." Water Science and Technology 47, no. 1 (January 1, 2003): 97–104. http://dx.doi.org/10.2166/wst.2003.0026.

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Biological nitrogen removal via nitrite pathway in wastewater treatment is very important especially in the cost of aeration and as an electron donor for denitrification. Wastewater nitrification and nitrite accumulations were carried out in a biofilm reactor. The biofilm reactor showed almost complete nitrification and most of the oxidized ammonium was present as nitrite at the ammonium load of 1.2 kg N/m3/d. Nitrite accumulation was achieved by the selective inhibition of nitrite oxidizers by free ammonia and oxygen limitation. Nitrite oxidation activity was recovered as soon as the inhibition factor was removed. Fluorescence in situ hybridization studies of the nitrite accumulating biofilm system have shown that genus Nitrosomonas which is specifically hybridized with probe NSM156 was the dominant nitrifying bacteria while Nitrospira was less abundant than those of normal nitrification systems. Further FISH analysis showed that the combinations of Nitrosomonas and Nitrospira cells were identified as important populations of nitrifying bacteria in an autotrophic nitrifying biofilm system.

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Zhou, Xiao-Han, Ying Liu, Rui-Jie Zhou, Hao Song, Xiao-Yu Liu, and Yong Qin. "Construction of the highly oxidized bicyclo[3.2.1]octane CD ring system of aconitine via a late stage enyne cycloisomerization." Chemical Communications 54, no. 86 (2018): 12258–61. http://dx.doi.org/10.1039/c8cc06819d.

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Harahuc, Lesia, and Isamu Suzuki. "Sulfite oxidation by iron-grown cells ofThiobacillus ferrooxidansat pH 3 possibly involves free radicals, iron, and cytochrome oxidase." Canadian Journal of Microbiology 47, no. 5 (May 1, 2001): 424–30. http://dx.doi.org/10.1139/w01-024.

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Thiobacillus ferrooxidans cells grown on ferrous iron oxidized sulfite to sulfate at pH 3, possibly by a free radical mechanism involving iron and cytochrome oxidase. A purely chemical system with low concentrations of Fe3+simulated the T. ferrooxidans system. Metal chelators, ethylenediamine tetraacetic acid (EDTA), 4,5-dihydroxy-1-3-benzene disulfonic acid (Tiron), o-phenanthroline, and 2,2'-dipyridyl, inhibited both sulfite oxidation systems, but the T. ferrooxidans system was inhibited only after the initial brief oxygen consumption. EDTA and Tiron, strong chelators of Fe3+, inhibited the oxidation at lower concentrations than o-phenanthroline and 2,2'-dipyridyl, strong chelators of Fe2+. Inhibition of Fe3+-catalyzed sulfite oxidation by EDTA and Tiron was instant, but the inhibition by o-phenanthroline and dipyridyl was briefly delayed, presumably for the reduction of Fe3+to Fe2+. Mannitol, a free radical scavenger, inhibited both systems to the same extent. Cyanide and azide inhibited only the T. ferrooxidans system, suggesting a role of cytochrome oxidase. It is proposed that sulfite is oxidized by a free radical mechanism initiated by Fe3+on the cell surface of T. ferrooxidans. Cytochrome oxidase is possibly involved in the regeneration of Fe3+from Fe2+by the normal Fe2+-oxidizing system of T. ferrooxidans.Key words: Thiobacillus ferrooxidans, sulfite oxidation, iron, free radical, cytochrome oxidase.

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Chakraborty, Anirban, Eric E. Roden, Jürgen Schieber, and Flynn Picardal. "Enhanced Growth of Acidovorax sp. Strain 2AN during Nitrate-Dependent Fe(II) Oxidation in Batch and Continuous-Flow Systems." Applied and Environmental Microbiology 77, no. 24 (October 14, 2011): 8548–56. http://dx.doi.org/10.1128/aem.06214-11.

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ABSTRACTMicrobial nitrate-dependent, Fe(II) oxidation (NDFO) is a ubiquitous biogeochemical process in anoxic sediments. Since most microorganisms that can oxidize Fe(II) with nitrate require an additional organic substrate for growth or sustained Fe(II) oxidation, the energetic benefits of NDFO are unclear. The process may also be self-limiting in batch cultures due to formation of Fe-oxide cell encrustations. We hypothesized that NDFO provides energetic benefits via a mixotrophic physiology in environments where cells encounter very low substrate concentrations, thereby minimizing cell encrustations.Acidovoraxsp. strain 2AN was incubated in anoxic batch reactors in a defined medium containing 5 to 6 mM NO3−, 8 to 9 mM Fe2+, and 1.5 mM acetate. Almost 90% of the Fe(II) was oxidized within 7 days with concomitant reduction of nitrate and complete consumption of acetate. Batch-grown cells became heavily encrusted with Fe(III) oxyhydroxides, lost motility, and formed aggregates. Encrusted cells could neither oxidize more Fe(II) nor utilize further acetate additions. In similar experiments with chelated iron (Fe(II)-EDTA), encrusted cells were not produced, and further additions of acetate and Fe(II)-EDTA could be oxidized. Experiments using a novel, continuous-flow culture system with low concentrations of substrate, e.g., 100 μM NO3−, 20 μM acetate, and 50 to 250 μM Fe2+, showed that the growth yield ofAcidovoraxsp. strain 2AN was always greater in the presence of Fe(II) than in its absence, and electron microscopy showed that encrustation was minimized. Our results provide evidence that, under environmentally relevant concentrations of substrates, NDFO can enhance growth without the formation of growth-limiting cell encrustations.

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Kanemitsu, Yoshihiko. "Photoluminescence spectrum and dynamics in oxidized silicon nanocrystals: A nanoscopic disorder system." Physical Review B 53, no. 20 (May 15, 1996): 13515–20. http://dx.doi.org/10.1103/physrevb.53.13515.

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Hou, Huiyuan, Alejandra Nieto, Feiyan Ma, William R. Freeman, Michael J. Sailor, and Lingyun Cheng. "Tunable sustained intravitreal drug delivery system for daunorubicin using oxidized porous silicon." Journal of Controlled Release 178 (March 2014): 46–54. http://dx.doi.org/10.1016/j.jconrel.2014.01.003.

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Lü, Shaoyu, Mingzhu Liu, and Boli Ni. "An injectable oxidized carboxymethylcellulose/N-succinyl-chitosan hydrogel system for protein delivery." Chemical Engineering Journal 160, no. 2 (June 2010): 779–87. http://dx.doi.org/10.1016/j.cej.2010.03.072.

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Journal articles on the topic 'Oxidized system'

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