Dismutation Reaction Research Articles

Complexes of a piperazine based macrocycle as Cu-Zn SOD biomimetic: approach by constants determination

Obtaining new compounds capable of catalyzing the dismutation reaction of the superoxide anion carried out by the enzyme Cu,Zn-SOD has become a topic of great interest. In the present work, the study of a ligand with a piperazine fragment and its Cu(II) and Zn(II) complexes is introduced. The protonation constants of the ligand, the stability constants of the complex species un with equivalent of Cu(II) and Zn(II), forming both mononuclear and heterobinuclear species, in the presence and absence of histidine as secondary ligand were determined. For all cases, species distribution diagrams were obtained, from which the spectra in the visible region of the species of greatest interest were obtained. As an approach to the Cu,Zn-SOD system, the formation of quaternary species formed between these ions, the main ligand and histidine as a secondary ligand, was verified, which could be used as mimetics of said enzyme. Some theoretical studies were carried out to support this study.

Promising Catalyst for Chlorosilane Dismutation

Currently, the most common method of silane synthesis for electronics and photovoltaics is trichlorosilane dismutation. Therefore, an experimental study of the kinetics of the dismutation reaction of chlorosilanes is of scientific and practical interest. A catalyst has been proposed that allows the dismutation reaction to be carried out in a wide range of temperatures and pressures. Both kinetic and thermodynamic data on the dependence of the rate of the dismutation reactions of trichlorosilane, dichlorosilane, and monochlorosilane on pressure were experimentally obtained. In addition, the dependence of saturated vapor pressure on temperature for monochlorosilane and dichlorosilane were also experimentally determined. Using the example of TCS, it was experimentally established that increasing the pressure to six atmospheres makes it possible to increase the specific productivity of the reactor by at least an order of magnitude due to the acceleration of the chemical reaction and the increase in the molar concentration of chlorosilanes in the vapor mixture. Consequently, it becomes possible to multiply the reactor’s load on the substance and, accordingly, the performance of the chlorosilane dismutation apparatus in general.

Anchoring of Copper(II)-Schiff Base Complex in SBA-15 Matrix as Efficient Oxidation and Biomimetic Catalyst.

A new mononuclear Cu(II) complex [Cu(L2)(H2O)2], where L is the Schiff base 2-[2-(3-bromopropoxy)benzylideneamino] benzoic acid, was synthesized and covalently anchored onto an amino-functionalized SBA-15 mesoporous silica in order to obtain an efficient heterogeneous catalyst. The elemental, structural, textural and morphological characterization confirmed the coordination of the central Cu(II) ion with two ligands and two H2O molecules in the synthesized complex and its successful immobilization into the inner pore surface of the NH2-functionalized support without the loss of the mesoporous structure. The catalytic activity of the free or immobilized Cu(II) complex was tested in the oxidation of cyclohexene with H2O2 under an air atmosphere and the dismutation reaction of the superoxide radical anions with very good results. In addition, catalyst reuse tests claim its suitability in alkene oxidation processes or as a biomimetic catalyst.

Coordination chemistry of alkali metal dimesityl-thio- and dimesityl-selenophosphinites [(L)2A-EPMes2]2 (A = Li, Na, K; E = S, Se; L = THF, THP) and [(18C6)K-SPMes2

The reactions of dimesitylphosphane oxide Mes2P(O)H with Lawessons reagent and dimesitylphoshane with selenium yield Mes2P(E)H with E = S (1a) and E = Se (1b), respectively, with moderate yields. Metalation of dimesitylphosphane sulfide 1a with n-butyllithium, sodium hydride or potassium hydride in THF allows the isolation of dinuclear dimesityl-thiophosphinites of the type [(thf)2A-S-PMes2]2 [A = Li (4), Na (5), K (2a)] with central four-membered A2S2 rings. The weaker base THP leads to the very similar aggregate [(thp)2K-S-PMes2]2 (3a) as has also been observed for the homologous potassium dimesityl-selenophosphinites of the type [(L)2K-Se-PMes2]2 [L = thf (2b), thp (3b)]. Addition of 18-crown-6 ether leads to deaggregation and expectedly to formation of mononuclear [(18C6)K-S-PMes2] (6). Moderate yields have been obtained due to dismutation reactions that yield the corresponding phosphinates AE2PMes2 and phosphanides APMes2, a degradation process which has been observed earlier also for Li-O-PMes2. This side reaction hampers the application of these thio- and selenophosphinites as catalysts in the addition of phosphane sulfides and selenides across alkynes.

NMR spectroscopic investigations on the successive implementation of nickel and zinc ions to a NacNac‐dibenzofuran‐Br ligand precursor

AbstractThe ligand precursor HNacNac‐dibenzofuran‐Br, LH, was synthesized by the condensation of 6‐bromo‐4‐dibenzofuranamine and 4‐(N‐(mesityl)amino)pent‐3‐en‐2‐one with the aim of preparing heterodinuclear nickel/zinc complexes in two successive steps. Reacting LH with Zn(HMDS)2, Zn(C6F5)2 and Zn(C2H5)2 led to the respective X‐Zn‐NacNac‐dibenzofuran‐Br complexes (X=HMDS (2), C6F5 (3), Et (4)). However, in case of 2 and 3 the subsequent treatment with Ni(COD)2/TMEDA did not lead to any conversion, probably as the steric bulk imposed by the NacNac‐Zn‐X entities was too high. 4 did react with Ni(COD)2/TMEDA, likely in the envisaged manner, but apparently the targeted product complex Et‐Zn‐NacNac‐dibenzofuran‐Ni(TMEDA)Br, once formed, immediately reacts further via a Negishi coupling reaction, so that Br‐Zn‐NacNac‐dibenzofuran‐Et (5) is formed. The reaction of 4 with triethylammonium bromide led to the formation of the Br‐Zn‐NacNac‐dibenzofuran‐Br (6) complex that could be reacted with Ni(COD)2/TMEDA successfully. All attempts to purify the product led to Zn(NacNac‐dibenzofuran‐Ni(TMEDA)Br)2, which is insoluble in THF and thus drives a dismutation reaction.

Thermodynamics and Kinetics of the Reaction of Catalytic Dismutation of Chlorosilanes in the Vapor Phase in the Temperature Range of 353–393 K

Currently, the most common method of silane synthesis for electronics and photovoltaics is trichlorosilane (TS) dismutation. TS dismutation proceeds in the form of a reactions cascade, therefore its study is of both practical and scientific interest. The results of calculating the equilibrium composition of the reaction mixture in the vapor phase based on literature data from various sources were not reliable. Therefore, the dependence of the composition of the reaction mixture on the time of contact of the TS vapor with the catalyst under static conditions was experimentally investigated. The stationary composition of the mixture, close to equilibrium, was determined. A good agreement of the obtained results with the literature data in one of the sources was shown. The kinetics of the dismutation reaction of TS and dichlorosilane (DCS) was carried out by the flow method. As a result of regression analysis of experimental data, the rate constants of the direct and reverse dismutation reactions of TS, DCS, and monochlorosilane (MSC) were obtained. The rate constants were used to calculate the equilibrium composition of the reaction mixture. A good agreement between the calculated and experimental data was shown.

Nanostructured binuclear Fe(III) and Mn(III) porphyrin materials: Tuning the mimics of catalase and peroxidase activity

Tuning of the structures and electronic effects of nanocrystals is of great relevance to the preparation of specialized materials such as artificial enzymes.In this study, binary porphyrin materials have been prepared by ionic self-assembly of oppositely charged Fe(III) and Mn(III) porphyrins. The materials have been characterized by SEM, XPS and UV–vis spectroscopy and tested as biomimetic models of catalase. The heterometallic material [Mn/Fe], prepared by association of MnTHPyP and FeTSPP, showed the highest activity for H2O2 dismutation reaction, 89–95 U·mg−1, over a pH range of 4–7. An enhancement in activity of one to two orders of magnitude can be observed relatively to the individual Fe(III) or Mn(III) porphyrins and to the mono-metallic materials that were prepared by association of a metalloporphyrin (MP) and a metal free porphyrin (H2P). These results support the occurrence of cooperative mechanisms between two metal ion centers within the structure. The materials with the highest catalase-like activity were also tested as peroxidase mimetics in ABTS oxidation. Best activity was observed for the [Mn/Fe] material at pH 4, while at pH 6 the activity decreases by 97%. EPR studies at pH 6 demonstrate the absence of free hydroxyl or superoxide radicals in the mechanism and thus support the activity of the [Mn/Fe] material as a catalytic antioxidant under these conditions.

Synergistic enhancement of ferrous ion with zero-valent copper/oxygen system: In-site formation and catalysis of H2O2

Zero-valent copper (ZVC) coupled with oxygen gas (O2) was extensively studied to degrade refractory contaminant, while the active dismutation reaction and low reactivity of Cu(I) refrained the performance at acid condition. In this study, ferrous ion (Fe(II)) was added to the ZVC/O2 system (ZVC/Fe(II)/O2 system) to enhance the degradation ability, the degradation rate of acid orange 7 in the ZVC/Fe(II)/O2 system was enhanced by 34.8% compared to the ZVC/O2 system, and the corresponding apparent rate constant was almost three times higher than that of the ZVC/O2 system. In the reactive species identification experiments, by electron spin resonance experiments and quenching experiments of nitrobenzene, tert butyl alcohol and methanol, hydroxyl radical was proven as primary reactive oxygen species rather than high-valent metal-Cu(III). In addition, the optimum ZVC dosage, Fe(II) concentration, pH and stirring rate were derived based on optimization experiments combined with economic applicability. In the ZVC/Fe(II)/O2 system, the mechanism was analyzed by detecting the variation of the concentration of H2O2, Cu(I) and total dissolved copper in the solution. In the degradation process, ZVC was corroded to form Cu(I) by H+, then Cu(I) reacted with O2 to generate hydrogen peroxide, the generated hydrogen peroxide was induced by Fe(II) and Cu(I) to produce hydroxyl radical, at the same time, ZVC and Cu(I) could reduce Fe(III) to Fe(II). The coexisting substances like carbonate ion, nitrate ion, sulfate ion and phosphate ion did not affect the demineralization of acid orange 7 in the ZVC/Fe(II)/O2 system, chloride ion remarkably accelerated the degradation rate of acid orange 7, while fulvic acid limited the acid orange 7 removal. The ZVC/Fe(II)/O2 system also showed excellent degradability in well water, lake water and tap water. Total dissolved copper concentration was controlled within 1 mg/L by the alkali precipitation method, which was within II-level environmental quality criteria in China. These facts suggested that Fe(II)-enhanced ZVC system had great development potential in water treatment.

Phosphorus and kalium co-doped g-C3N4 with multiple-locus synergies to degrade atrazine: Insights into the depth analysis of the generation and role of singlet oxygen

In this work, with the help of KH2PO4, a phosphorus and kalium co-doped g-C3N4 with cyano and nitrogen vacancies (PKCN) have been prepared via a simple thermal treatment. The prepared PKCN exhibited excellent singlet oxygen (1O2) generation ability for the highly efficient degradation of atrazine (ATZ), reaching 95% (pH=5) of decomposition efficiency within 60 min under visible light. Density functional theory (DFT) calculation results visualize the role of cyano groups, nitrogen vacancies, K atoms and P atoms, and the synergistic effect of the above four aspects contributed to the three pathways of hole oxidation, energy transfer and dismutation reaction for efficient 1O2 generation. Moreover, the T.E.S.T and soybean culture experiment demonstrated the toxicity of ATZ have been significantly reduced after the photocatalytic process. This work can give deep insights into the roles and synergy of each active unit for designing and synthesizing efficient g-C3N4.

Atomically dispersed 3d metal bimetallic dual-atom catalysts and classification of the structural descriptors

Solid atomic catalysts with well-defined and complex structures are believed to effectively bridge homogeneous and heterogeneous catalysis. Nonetheless, the current limited capacity of “precise engineering” in solid atomic catalysts has led to structural heterogeneity and thus unsatisfactory catalytic selectivity. Here, we show that late 3 d metal cations, such as Co 2+ , Ni 2+ , Cu 2+ , and Zn 2+ , can be assembled to afford combinations of “dual atoms” within zeolitic micropores, and this clearly avoids issues like uncontrolled metal aggregation during synthesis. In this work, by the quantitative evaluation of the structural descriptors over a probe superoxide dismutation reaction, we demonstrate the unique synergistic advantage between (i) neighboring bimetallic active motifs, (ii) tertiary structure around the zeolitic support, and (iii) the local coordination environment. The identification and tunability of the structural descriptors shown in this work unravel a reliable approach to the precise engineering of next-generation solid dual-atom catalysts. • Atom-precise synthesis of supported bimetallic dual-atom catalysts • Reliable approach for precise microenvironment engineering in solid catalysts • Discovery of the interplay between the structural descriptors and catalytic properties • Demonstration of synergistic effect with sorafenib for augmented tumor cell apoptosis We aim to present a creative approach to afford dual-atom bimetallic catalysts in a controlled and modular manner. This directly allows the combinations of different late 3 d metals (forming M 1 -M 2 -supported dual atoms) and shows extensive possibility not limited to catalytic applications. Through the unique synergistic advantage between the two metal species and the tertiary structure around the zeolitic support, we demonstrated the feasibility of developing next-generation dual-atom bimetallic catalysts in a controlled manner as well as the identification of the structural descriptors. The manipulation and control of materials and phenomena at atomic and molecular dimensions are achieved by utilizing the fundamental concepts of coordination and solid-state chemistries. The findings presented in this work reveal the precise engineering of supported dual-atom catalysts (such as combinations of 3 d /4 d metals) over support materials not only for biochemical applications but also for more extensive applications. This shall genuinely bring heterogeneous catalysis toward the molecular frontier that addresses the critical challenges in the field.

Multiple reinforcement of chloride ion on oxidizing acetaminophen with zero-valent copper particles: In-site formation and catalysis of hydrogen peroxide

Zero-valent copper particles (Cu0) used to degrade pollutant due to its in-site generation and activation of hydrogen peroxide (H2O2), while the disproportionation of Cu+ limited the efficacy. In this study, spiking chloride ion (Cl−) into zero-valent copper (Cu0) system (Cl−/Cu0 system) enhanced greatly acetaminophen degradation. The addition of Cl− not only reduced the dismutation reaction of Cu+, but also helped the comproportionation reaction of Cu0 and Cu2+, leading to much generation of Cu+ and H2O2. Hydroxyl radical (OH) and reactive chlorine species were identified as the dominant reactive oxidants in the Cl−/Cu0 system with its contribution ratio of degrading acetaminophen being respectively 73.4 % and 23.8 %. In the Cl−/Cu0 system, Cu+ was released by H+ corrosion from Cu0, and then Cu+ coupled with Cl− forming Cu-Cl complexes; Meanwhile, the reaction of O2 and the species of Cu+ (e. g. Cu-Cl complexes and Cu+) produced H2O2 and, then the species of Cu+ catalyzed H2O2 to form OH; Thereinto, partial OH was shifted by Cl− to reactive chlorine species. Except for fulvic acid, coexisting substrates such as sulphate, nitrate and phosphate ions had no obvious inhibition impact on oxidizing acetaminophen in the Cl−/Cu0 system. Furthermore, the Cl−/Cu0 system presented a good removal rate of acetaminophen in three actual water samples. Moreover, three kinds of dyes and painkillers was removed over 78 % in the Cl−/Cu0 system. The residual total dissolved copper was under II-level of environmental quality standards for surface water in China by alkali precipitation and filtration after reaction. Therefore, the study provided a new idea to enhance Cu0 for the purification of pollutants.

The Use of Thiocyanate Formulations to Create Manganese Porphyrin Antioxidants That Supplement Innate Immunity.

The innate immune response to infection results in inflammation and oxidative damage, creating a paradox where most anti-inflammatory and antioxidant therapies can further suppress an already inadequate immune response. We have previously reported the beneficial effects of the exogenous supplementation of innate immunity with small pseudohalide thiocyanate (−SCN) in a mouse model of a cystic fibrosis (CF) lung infection and inflammation. The object of this study was to evaluate the use of −SCN as a counter anion for cationic manganese porphyrin (MnP) catalytic antioxidants, which could increase the parent compound’s antioxidant spectrum against hypohalous acids while supplementing innate immunity. The antioxidant activities of the parent compound were examined, as its chloride salt was compared with the −SCN-anion exchanged compound, (MnP(SCN) versus MnP(Cl)). We measured the superoxide dismutase activity spectrophotometrically and performed hydrogen peroxide scavenging using oxygen and hydrogen peroxide electrodes. Peroxidase activity was measured using an amplex red assay. The inhibition of lipid peroxidation was assessed using a thiobarbituric acid reactive species (TBARS) assay. The effects of the MnP compounds on macrophage phagocytosis were assessed by flow cytometry. The abilities of the MnP(Cl) formulations to protect human bronchiolar epithelial cells against hypochlorite (HOCl) and glycine chloramine versus their MnP(SCN) formulations were assessed using a cell viability assay. We found that anions exchanging out the chloride for −SCN improved the cellular bioavailability but did not adversely affect the cell viability or phagocytosis and that they switched hydrogen-peroxide scavenging from a dismutation reaction to a peroxidase reaction. In addition, the −SCN formulations improved the ability of MnPs to protect human bronchiolar epithelial cells against hypochlorous acid (HOCl) and glycine chloramine toxicity. These novel types of antioxidants may be more beneficial in treating lung disease that is associated with chronic infections or acute infectious exacerbations.

Catalytic oxidation of 4-acetamidophenol with Fe3+-enhanced Cu0 particles: In-site generation and activation of hydrogen peroxide

Cu0 coupled with O2 was used to degrade contaminant due to in-site generation and catalysis of H2O2, while the low reactivity and active dismutation reaction of Cu+ refrained the performance at acidic condition. In this study, the removal rate of 4-acetamidophenol increased from 27 % to 83.4 % with Fe3+ spiked into the Cu0 system within 60 min •OH was the primary reactive species in the Fe3+/Cu0 system. In the Fe3+/Cu0 system, Cu0 was corroded to form Cu+ by H+ and O2, and then Cu+ interacted with O2 generating H2O2, and meanwhile Fe3+ was reduced to Fe2+ by Cu+ and Cu0; Consequently, Cu+ and Fe2+ induced H2O2 to produce •OH, but Fe2+ was easier to catalyze H2O2 than Cu+ at acidic pH. Except for fulvic acid, common water matrix including sulfate ion, phosphate ion, chloride ion and nitrate ion had no inhibition effect on the degradation of 4-acetamidophenol in the Fe3+/Cu0 system. over 62 % of 4-acetamidophenol in tap water, Hou-lake water and well water was greatly oxidized by the Fe3+/Cu0 system. Furthermore, the amount of total dissolved copper decreased to 0.895 mg/L by the method of alkali precipitation in the Fe3+/Cu0 system. The study provided a theoretical direction to the Fe3+-enhanced Cu0 system for purifying wastewater.

Ab initio study of superoxide dismutase (SOD) and catalase activity of EUK-134.

Dismutation reaction of superoxide radical catalyzed by EUK-134 has lower activation energy than non-catalytic reaction, and therefore, EUK-134 catalyzes dismutation reaction of superoxide radical. For non-catalytic dismutation reaction of hydrogen peroxide, there are three possible reaction paths, among which MEP3 has the lowest activation energy, and therefore, is thought to be the most probable reaction path. Dismutation reaction of hydrogen peroxide catalyzed by EUK-134 occurs in two successive steps and has lower energy barrier than non-catalytic dismutation reaction, and therefore, EUK-134 is thought to catalyze the dismutation reaction of hydrogen peroxide. HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) and ESP-fitted charge analysis of EUK-134 indicate that Mn atom plays an electron acceptor and donor for dismutation reactions of superoxide radical and hydrogen peroxide catalyzed by EUK-134, respectively.

Multifunctionalized Mesostructured Silica Nanoparticles Containing Mn2 Complex for Improved Catalase-Mimicking Activity in Water

We report the synthesis of a hybrid nanocatalyst obtained through the immobilization of bio-inspired [{Mn(bpy)(H2O)}(µ-2-MeC6H4COO)2(µ-O){Mn(bpy)(NO3)}]NO3 compound into functionalized, monodispersed, mesoporous silica nanoparticles. The in situ dual functionalization sol–gel strategy adopted here leads to the synthesis of raspberry-shaped silica nanoparticles of ca. 72 nm with a large open porosity with preferential localization of 1,4-pyridine within the pores and sulfobetaine zwitterion on the nanoparticles’ periphery. These nano-objects exhibit improved catalase-mimicking activity in water thanks to the encapsulation/immobilization of the catalytic active complex and high colloidal stability in water, as demonstrated through the dismutation reaction of hydrogen peroxide.

Combined action of FOXO1 and superoxide dismutase 3 promotes MDA-MB-231 cell migration

Superoxide dismutase 3 (SOD3), one of SOD isozymes, maintains extracellular redox homeostasis through the dismutation reaction of superoxide. Loss of SOD3 in tumor cells induces oxidative stress and exacerbates tumor progression; however, interestingly, overexpression of SOD3 also promotes cell proliferation through the production of hydrogen peroxide. In this study, we investigated the functional role of SOD3 in human breast cancer MDA-MB-231 cell migration and the molecular mechanisms involved in high expression of SOD3 in MDA-MB-231 cells and human monocytic THP-1 cells. The level of histone H3 trimethylation at lysine 27 (H3K27me3), a marker of gene silencing, was decreased in 12-O-tetra-decanoylphorbol-13-acetate (TPA)-treated THP-1 cells. Also, that reduction was observed within the SOD3 promoter region. We then investigated the involvement of H3K27 demethylase JMJD3 in SOD3 induction. The induction of SOD3 and the reduction of H3K27me3 were inhibited in the presence of JMJD3 inhibitor, GSK-J4. Additionally, it was first determined that the knockdown of the transcription factor forkhead box O1 (FOXO1) significantly suppressed TPA-elicited SOD3 induction. FOXO1-mediated SOD3 downregulation was also observed in MDA-MB-231 cells, and knockdown of FOXO1 and SOD3 suppressed cell migration. Our results provide a novel insight into epigenetic regulation of SOD3 expression in tumor-associated cells, and high expression of FOXO1 and SOD3 would participate in the migration of MDA-MB-231 cells.

Potentialities of mass spectrometry on activation energy and secondary reactions determination of calcium oxalate thermal decomposition

AbstractThis work investigates the potentialities of the thermal analysis (TA) coupled with the mass spectrometry (MS) technique by studying the thermal decomposition of calcium oxalate monohydrate (CaC2O4·H2O). The aim of this work is twofold: to demonstrate, at first, the efficacy of coupling the thermal gravimetric (TG)‐MS experimental approach to check the presence of intermediate reactions beyond the conventional three‐step decomposition: dehydration, decarbonylation, and decarbonation; second, to test the reliability of different modeling approaches in determining the activation energy (E) including, as innovative alternative, the use of the MS signals. The TA is carried out at selected constant heating rates by recording both the thermal gravimetric analysis, differential thermal analysis) profiles, and, simultaneously from the MS data, the signals of the total ion current and the ion currents selected to monitor the release of the H2O, CO, and CO2 species. These experimental results are effective in determining the E through different modeling approaches based on the maximum reaction rate method and isoconversional procedures including both TG and MS signals. Coupling the TA‐MS technique has allowed us to check the concurrent presence of the dismutation reaction of carbon monoxide, occurring during the decarbonylation event, and to determine the corresponding E value (E = 169.7 kJ/mol). These results present a surprising correlation between the global enthalpy of the two reactions involved in this second step and their activation energy values. On the whole, the results satisfy the conventional constraints usually adopted to test the reliability of the E results and are consistent with the majority of the datasets published in the literature on this subject.

Effects of the Use of Staphylococcus carnosus in the Curing Process of Meat with a Reduced Amount of Sodium Nitrite on Colour, Residue Nitrite and Nitrate, Content of Nitrosyl Pigments, and Microbiological and the Sensory Quality of Cooked Meat Product

The aim of the work was to apply the bacteria Staphylococcus carnosus ATCC 51365 in the meat curing process with the use of a reduced amount of sodium nitrite and to evaluate the effects of bacteria on residual nitrites and nitrates, the content of nitrosyl pigments, colour, pH, oxidation-reduction potential, microbiological, and the sensory quality of a cooked meat product. Three meat batters in cans were prepared: (C) a control batter cured with NaNO2—100 mg/kg, (L) a batter cured with NaNO2—15 mg/kg, and (LS) a batter cured with NaNO2—15 mg/kg and S. carnosus (107 CFU/g). The cans were stored at a temperature of 4°C for 24 h (curing time) and cooked. The analysis was carried out after production and after 4 and 8 weeks of storage. The use of denitrifying bacteria in the curing process with a reduced amount of sodium nitrite increased the availability of nitrite in the meat, by reducing nitrates formed as a result of a dismutation reaction. The reaction contributed to the formation of nitrosyl pigments in a larger quantity than in the treatment in which the denitrifying bacteria were not used. The LS treatment was characterized by the greatest redness. The colour of the LS treatment was stable during storage. No negative effect of S. carnosus on the sensory quality of the meat product was found. The use of S. carnosus had no influence on the microbiological quality of meat product during storage.

Toxicity of different forms of antimony to rice plants: Effects on reactive oxidative species production, antioxidative systems, and uptake of essential elements

Antimonite [Sb(III)] and antimonate [Sb(V)] are known to have different toxicity to plants, but the corresponding mechanisms are not fully understood. This study was conducted to investigate reactive oxygen species (ROS), antioxidant systems, and levels of certain essential elements in response to exposure to Sb(III) and Sb(V). Results showed that exposure to Sb(V) caused oxidative stress in a rice plant (Yangdao No.6). Sb(III) was shown to be more toxic than Sb(V) as judged from a lower shoot biomass, a higher loss of essential elements, and higher production of superoxide anion free radicals (O2−). The toxicity of Sb(III) might partially be due to the disturbance of the O2ˉ dismutation reaction, which resulted in root cell membrane damage under exposure to 20 mg L−1 Sb(III). Sb(V) stimulated the shoot fresh weight and the shoot uptake of many essential elements. Moreover, Sb(V) and Sb(III) both stimulated the accumulation of calcium in the shoots and roots, and calcium was found to significantly correlate with the concentrations of many essential elements and with some parameters correlated to antioxidant systems, suggesting a Ca-induced regulatory mechanism. The activity of glutathione peroxidase was significantly enhanced by Sb(V) and Sb(III), suggesting a role in scavenging hydrogen peroxide. Catalase was activated by exposure to 20 mg L−1 Sb(III) in the roots and by exposure to 20 mg L−1 Sb(V) both in the shoots and roots. However, peroxidase was activated by exposure to 5 mg L−1 Sb(III) in the shoots and by exposure to 5 mg L−1 Sb(V) in the roots. This study, for the first time, showed the differences between Sb(V) and Sb(III) toxicity when looking at the antioxidant response and essential element uptake.

IgG-Dependent Dismutation of Superoxide in Patients with Different Types of Multiple Sclerosis and Healthy Subjects.

This work is the first to demonstrate that class G immunoglobulins (IgGs) in patients with multiple sclerosis and healthy individuals have the ability to catalyze the dismutation reaction of the superoxide anion radical. Thus, superoxide dismutase (SOD) activity is an intrinsic property of antibodies, which is confirmed by a number of stringent criteria. SOD activity of IgGs in patients with multiple sclerosis statistically significantly exceeds such activity in healthy individuals by 2-4 times. Moreover, the maximum activity has been registered in patients with relapsing remitting multiple sclerosis. The kinetic characteristics of the SOD reaction of IgGs are several orders of magnitude lower than those for the SOD enzyme but do not differ between patients with multiple sclerosis and healthy individuals. Consequently, abzymes with SOD activity have a lower catalysis rate than that of the enzymes and form a stronger complex with the substrates. Inhibitory analysis showed that this activity is inhibited by classical metal-dependent SOD inhibitors. The activity of IgGs was inhibited by classical metal-dependent inhibitors EDTA and TETA (triethylenetetramine). Also, high catalase activity of IgGs was detected in these patients. We suggest that these abzymes help protect the body from oxidative stress.