Conversion Of Peroxide Research Articles

Reactive Oxygen Species Scavengers Improve Voltage‐Gated K+ Channel Function in Pulmonary Arteries of Newborn Pigs with Progressive Hypoxia‐Induced Pulmonary Hypertension

Abstract Changes in voltage-gated K(+) (Kv) channel function contribute to the pathogenesis of pulmonary hypertension. Yet the mechanisms underlying Kv channel impairments in the pulmonary circulation remain unclear. We tested the hypothesis that reactive oxygen species (ROSs) contribute to the Kv channel dysfunction that develops in resistance-level pulmonary arteries (PRAs) of piglets exposed to chronic in vivo hypoxia. Piglets were raised in either room air (control) or hypoxia for 3 or 10 days. To evaluate Kv channel function, responses to the Kv channel antagonist 4-aminopyridine (4-AP) were measured in cannulated PRAs. To assess the influence of ROSs, PRAs were treated with the ROS-removing agent M40403 (which dismutates superoxide to hydrogen peroxide), plus polyethylene glycol catalase (which converts hydrogen peroxide to water). Responses to 4-AP were diminished in PRAs from both groups of hypoxic piglets. ROS-removing agents had no impact on 4-AP responses in PRAs from piglets exposed to 3 days of hypoxia but significantly increased the response to 4-AP in PRAs from piglets exposed to 10 days of hypoxia. Kv channel function is impaired in PRAs of piglets exposed to 3 or 10 days of in vivo hypoxia. ROSs contribute to Kv channel dysfunction in PRAs from piglets exposed to hypoxia for 10 days but are not involved with the Kv channel dysfunction that develops within 3 days of exposure to hypoxia. Therapies to remove ROSs might improve Kv channel function and thereby ameliorate the progression, but not the onset, of pulmonary hypertension in chronically hypoxic newborn piglets.

Identification of Electron Transfer Complexes between Shewanella Oneidensis Cytochrome C Peroxidase and ScyA through Computational and Biochemical Analysis

Bacterial diheme cytochrome c peroxidases form part of the detoxification pathways in the periplasmic space that convert hydrogen peroxide to water. The turnover of peroxide requires a two-electron reduction, and these reducing equivalents must be delivered to the peroxidase by soluble electron transfer proteins. This study focuses on the electron transfer complexes formed between the diheme cytochrome c peroxidase from Shewanella oneidensis (So CcP) and its native electron donor ScyA. Due to the transient nature of this interaction and its presumed dependence on redox state of the two binding partners, traditional biophysical analysis of this system has proved challenging. Here, we report the use of RosettaDock to predict the protein-protein interaction surfaces on So CcP when in the inactive, oxidized state and the active, semi-reduced state. We validate these models by generating site-directed mutants designed to interfere with specific hydrophobic interfaces suggested in the docking analysis and measuring their kinetic competence for both single-electron reductive activation and two-electron peroxide turnover. These results suggest how redox-driven changes in So CcP conformation regulate protein-protein interactions.

Modification with hemeproteins increases the diffusive movement of nanorods in dilute hydrogen peroxide solutions

Nanorods were decorated with different hemeproteins that are able to convert hydrogen peroxide. When dispersed into hydrogen peroxide solutions, most of these nanorods are characterized by diffusion coefficients which increase with the concentration of hydrogen peroxide. Such a behaviour does not characterize unmodified nanorods.

Mono, Di and Trifunctional Cyclic Organic Peroxides: The Effect of Substituents and Ring Size on their Thermolysis in 1,4-dioxan

The thermal decomposition reaction of cyclic organic peroxides was studied in 1,4-dioxan at initial concentrations between ~10–4 and 10–2 mol L–1 and at a temperature interval between 100 and 170°C, according to the thermal stability of each compound. The kinetic behaviour observed in all systems studied follows a pseudo first order kinetic law up to at least ~86 % of peroxide conversion. An important substituent effect is operative on the rate constant values and consequently on the activation parameters of the thermal decomposition reaction. The application of different treatments (compensation affect or a statistical treatment) on the kinetic data shows the existence of two sets of cyclic peroxides with comparable kinetic behaviour. Different peroxide–solvent interaction mechanisms can be considered within each series.

Iron Overload Impairs Hematopoiesis by Damaging MSCs Through ROS Signaling Pathway.

Abstract 2097Iron is a useful component of cytochromes, oxygen-binding molecules and some enzymes due to its capacity to accept and donate electrons readily. However, excessive iron accumulation can damage tissues and cells by catalyzing the conversion of superoxide and hydrogen peroxide to free radical species that can attack cellular membranes, proteins and DNA. Recent multiple data revealed that iron chelation therapy was effective in treating cytopenia in iron overload disease, which supported the idea that iron overload affected hematopoiesis in bone marrow(BM). Based on these findings, We demonstrated that iron overload suppressed hematopoiesis by inhibiting hematopoietic stem/progenitor cells and the effects could be restored by iron chelation or anti-oxidants(Zhao et al., Blood, 2010, 116:4247a). However, it is unclear whether iron overload can impair BM hematopoiesis by injuring the microenvironment. As an important component of the BM microenvironment, Mesenchymal stem cells (MSCs) secrete a large amount of cytokines and extracellular matrix protein which provides a favorable platform for the localization, self-renewal, and differentiation of hematopoietic stem cells. Here we hypothesize that iron overload impairs BM microenvironment by affecting the function and survival of MSCs which is mediated by ROS.In this study we first established an iron overload model of MSCs by adding ferric ammonium citrae (FAC) to the culture medium. To confirm this model, the labile iron pool (LIP) level of MSCs was detected using the calcein-AM method. We found that the LIP of MSCs was significantly higher than control and reached the highest level when cultured at 400μmol/L FAC for 12h. Next we analyzed whether iron overload can affect proliferation, apoptosis and function of MSCs by the following experiments. Firstly, the proliferation of MSCs was evaluated using population doubling time (DT). Under iron overload, the population doubling time (DT) of MSCs was 24.43± 2.72 hours, which was signifcantly longer than control(16.03± 2.31 hours; P=0.015). However, the difference wasn’t significant after two passages (P=0.936). Possible explanation could be that the injury to MSCs is reversible following decreased concentration of iron after passaging. Secondly, the apoptosis of MSCs altered by iron overload was measured by staining Annexin V/PI, and we found the apoptosis rate was higher in the iron overload group(12.75±0.32%) than control (3.63±0.80%)(P<0.05). Finally, mono-nuclear cells were purified from umbilical cord blood and co-cultured with MSCs to assess the hematopoiesis-supportive function of MSCs. Iron overload group showed decreased hematopoietic support capacity than control. Taken together, these findings proved iron overload impaired hematopoietic microenvironment by decreasing proliferation, inducing apoptosis and injuring the hematopoietic support capacity of MSCs.We then explored the possible mechanism that may take part in this process. It has already been reported that iron overload may result in the generation of reactive oxygen species (ROS). Similarly, we found that ROS level of MSCs could be positively correlated with the concentration of FAC and reached its highest level when cultured at 400μmol/L FAC for 12h. Finally, Western blot analysis of whole cell lysates from umbilical derived MSC using antibodies recognizing known ROS-related signaling pathways revealed robust increases in phospho-p38, p53 in response to FAC compared with control, with inhibition of these signaling pathways noted in response to NAC or GSH at suitable dose, suggesting that antioxidant can inhibit ROS-induced signaling pathway in iron overload.In conclusion, Our finding indicates that iron overload can injure hematopoiesis by enhancing oxidative stress in MSC. Our data further suggests creatively that antioxidant and cytotherapy may be an effective method in curing deficient hematopoiesis in iron overload. Disclosures:No relevant conflicts of interest to declare.

Redox Reactions and Microbial Killing in the Neutrophil Phagosome

When neutrophils kill microorganisms, they ingest them into phagosomes and bombard them with a burst of reactive oxygen species. This review focuses on what oxidants are produced and how they kill. The neutrophil NADPH oxidase is activated and shuttles electrons from NADPH in the cytoplasm to oxygen in the phagosomal lumen. Superoxide is generated in the narrow space between the ingested organism and the phagosomal membrane and kinetic modeling indicates that it reaches a concentration of around 20 μM. Degranulation leads to a very high protein concentration with up to millimolar myeloperoxidase (MPO). MPO has many substrates, but its main phagosomal reactions should be to dismutate superoxide and, provided adequate chloride, catalyze efficient conversion of hydrogen peroxide to hypochlorous acid (HOCl). Studies with specific probes have shown that HOCl is produced in the phagosome and reacts with ingested bacteria. The amount generated should be high enough to kill. However, much of the HOCl reacts with phagosomal proteins. Generation of chloramines may contribute to killing, but the full consequences of this are not yet clear. Isolated neutrophils kill most of the ingested microorganisms rapidly by an MPO-dependent mechanism that is almost certainly due to HOCl. However, individuals with MPO deficiency rarely have problems with infection. A possible explanation is that HOCl provides a frontline response that kills most of the microorganisms, with survivors killed by nonoxidative processes. The latter may deal adequately with low-level infection but with high exposure, more efficient HOCl-dependent killing is required. Better quantification of HOCl and other oxidants in the phagosome should clarify their roles in antimicrobial action.

Mitochondrial ROS and muscle glucose uptake during exercise in transgenic mice

much research has examined the factors regulating skeletal muscle glucose uptake during exercise. Part of the impetus for this work has been to describe and understand the effects of regular physical activity (i.e., exercise training) on muscle glucose uptake and energy substrate partitioning,

Vanadium(III) and vanadium(IV) catalysts in a membrane reactor for benzene hydroxylation to phenol and study of membrane material resistance

Benzene hydroxylation to phenol by using vanadium based catalysts and product recovery were performed in a two-phase membrane reactor. Benzene permeates, through the hydrophobic polypropylene membrane, in the aqueous phase containing the catalyst while phenol permeates back accumulating in the organic phase. The following fundamental aspects have been studied: dose of hydrogen peroxide, initial oxidation states of vanadium catalysts, duration of catalytic tests and lifetime of the membrane in terms of physical and chemical resistance. It was observed that feeding the oxidant by a micro pump, working in the “bulk tube” mode, phenol yield, final phenol concentration in the organic phase, phenol turnover number and system productivity increased, and no tar was formed. Initial oxidation state of vanadium catalysts influenced system performance: indeed improved results in terms of yield (35.2% vs. 25.1%), conversion of hydrogen peroxide to phenol (36.6% vs. 25.9%), productivity (0.97 g gcat−1 h−1 vs. 0.78 g gcat−1 h−1) were obtained by using vanadium(III) chloride compared to vanadium(IV) acetyl acetonate. Higher phenol extraction/recovery in the organic phase (61.1% vs. 46.3%) and then higher selectivity (97.5% vs. 92.8%) were obtained by increasing test duration from 270 to 510min. A weak membrane resistance was observed after 246h of consecutive catalytic runs on the same membrane piece, showing degradation of the membrane material (polypropylene) caused by the OH radical generated in the reacting mixture.

Antioxidant activity of the ethanolic extracts of leaves, stems and fruits of Solanum nigrum

Free radicals contribute to more than one hundred disorders in humans including atherosclerosis, arthritis, ischemia and reperfusion injury of many tissues, central nervous system injury, gastritis, cancer and AIDS.[1-2] Free radicals due to environmental pollutants, radiation, chemicals, toxins, deep fried and spicy foods as well as physical stress cause depletion of immune system antioxidants, change in gene expression and induce abnormality in proteins. Oxidation process is one of the most important routes for producing free radicals in food, drugs and even living systems. Catalase and hydroperoxidase enzymes convert hydrogen peroxide and hydroperoxides to non-radical forms and functions as natural antioxidants in human body. Due to depletion of immune system natural antioxidants in different maladies, consuming antioxidants as free radical scavengers may be necessary. [3-5]

Synthesis of titanium silicalite-1 with small crystal size by using mother liquor of titanium silicalite-1 as seeds (II): Influence of synthesis conditions on properties of titanium silicalite-1

Titanium silicalite-1 with small crystal size (small-crystal TS-1) was synthesized in a TPABr–ethylamine hydrothermal system by using the mother liquor of nano-sized TS-1 as seeds. The synthesis conditions were systematically studied, including the purification methods of the small-crystal TS-1, Si/Ti molar ratio in TS-1, amount of the added seed and the crystallization period. The as-synthesized TS-1 was characterized by X-ray powder diffraction (XRD), Fourier-transform infrared (FT-IR), Ultraviolet–visible diffuse reflectance (UV–vis), Ultraviolet Raman spectroscopy (UV-Raman), nitrogen sorption, elemental analysis, atomic force microscope (AFM) and scanning electron microscopy (SEM). The size of the TS-1 crystals formed (about 600nm×400nm×250nm) was not significantly affected by the synthesis conditions except for the amount of added seed. The catalytic performance of the synthesized small-crystal TS-1 for the epoxidation of propylene was evaluated. The conversion of hydrogen peroxide, the selectivity of propylene oxide and the utilization of hydrogen peroxide reached 92.2%, 98.0% and 97.0%, respectively, when the mother liquor of small-crystal TS-1 was purified three times by precipitation, the Si/Ti molar ratio was 50, the seed/SiO2 weight ratio was 0.06 and the crystallization time was 48h.

The level of ascorbate peroxidase is enhanced in benznidazole-resistant populations of Trypanosoma cruzi and its expression is modulated by stress generated by hydrogen peroxide

Ascorbate peroxidases (APX) are class I heme-containing enzymes that convert hydrogen peroxide into water molecules. The gene encoding APX has been characterized in 11 strains of Trypanosoma cruzi that are sensitive or resistant to benznidazole (BZ). Bioinformatic analysis revealed the presence of two complete copies of the T. cruzi APX (TcAPX) gene in the genome of the parasite, while karyotype analysis showed that the gene was present in the 2.000-kb chromosome of all of the strains analyzed. The sequence of TcAPX exhibited greater levels of similarity to those of orthologous enzymes from Leishmania spp than to APXs from the higher plant Arabidopsis thaliana. Northern blot and real-time reverse transcriptase polymerase chain reaction (RT-PCR) analyses revealed no significant differences in TcAPX mRNA levels between the T. cruzi strains analyzed. On the other hand, Western blots showed that the expression levels of TcAPX protein were, respectively, two and three-fold higher in T. cruzi populations with in vitro induced (17 LER) and in vivo selected (BZR) resistance to BZ, in comparison with their corresponding susceptible counterparts. Moreover, the two BZ-resistant populations exhibited higher tolerances to exogenous hydrogen peroxide than their susceptible counterparts and showed TcAPX levels that increased in a dose-dependent manner following exposure to 100 and 200 µM hydrogen peroxide.

Structural impact of honeycomb catalysts on hydrogen peroxide decomposition for micro propulsion

Hydrogen peroxide is under investigation with regard to its potential to replace the presently used highly toxic rocket propellants NTO and MON-3. Catalytically decomposed hydrogen peroxide results in a steam–oxygen mixture at elevated temperature and can be used either as a monopropellant or as an oxidizer in a bipropellant system. To guide the monolith catalyst design, a lumped parameter model of the decomposition implemented into a numerical thermal model has been developed. The one dimensional flow model includes decomposition and is coupled to a finite element structural domain of the decomposition chamber and catalyst to investigate the impact of the catalyst and the chamber structure on the decomposition behavior. Special focus is laid on the transitional behavior of hydrogen peroxide conversion to facilitate immediate start-up of the thruster system after valve opening command. The numerical results have been validated with experimental data. Major findings of the model such as the existence of a radial temperature gradient across the catalyst have been experimentally validated. The presented theoretical method predicted a strong impact of structural mass capacities of catalyst and decomposition chamber on the transient decomposition performance. This prediction has shown to be in good correlation with the experimental results.

Oxidative deterioration of platinum nanoparticle and its prevention by palladium

Pt nanoparticle is a strong reductant and has been used as an antioxidant in cosmetics and medicine. It was reported to have catalase-like activity, which converts hydrogen peroxide to water and oxygen. However, in this study, freshly prepared Pt nanoparticle was almost inert towards decomposing hydrogen peroxide. The catalase-like activity of Pt nanoparticle increased with increasing weeks of storage at room temperature and became more significant when the Pt nanoparticle was exposed to air. No hydroxyl radical formation was confirmed by several methods such as ESR spin-trapping, dimethyl sulphoxide oxidation, salicylic acid hydroxylation and hydroxytoluene oxidation, indicating that the decomposition of hydrogen peroxide proceeds by the two-electron oxidation/reduction reaction. The oxidatively deteriorated Pt nanoparticle catalytically decomposed ascorbic acid, which is one of the most important biological antioxidants. We found that such oxidation was effectively prevented by the addition of Pd nanoparticle. We also discussed the reaction mechanisms and application of Pt nanoparticle.

Genetic polymorphism of the iron-regulatory protein-1 and -2 genes in age-related macular degeneration

Iron can be involved in the pathogenesis of AMD through the oxidative stress because it may catalyze the Haber–Weiss and Fenton reactions converting hydrogen peroxide to free radicals, which can induce cellular damage. We hypothesized that genetic polymorphism in genes related to iron metabolism may predispose individuals to the development of AMD and therefore we checked for an association between the g.32373708 G>A polymorphism (rs867469) of the IRP1 gene and the g.49520870 G>A (rs17483548) polymorphism of the IRP2 gene and AMD risk as well as the modulation of this association by some environmental and life-style factors. Genotypes were determined in DNA from blood of 269 AMD patients and 116 controls by the allele-specific oligonucleotide-restriction fragment length polymorphism and the polymerase chain reaction-restriction fragment length polymorphism. An association between AMD, dry and wet forms of AMD and the G/G genotype of the g.32373708 G>A-IRP1 polymorphism was found (OR 3.40, 4.15, and 2.75). On the other hand, the G/A genotype reduced the risk of AMD as well as its dry or wet form (OR 0.23, 0.21, 0.26). Moreover, the G allele of the g.49520870 G>A-IRP2 polymorphism increased the risk of the dry form of the disease (OR 1.51) and the A/A genotype and the A allele decreased such risk (OR 0.43 and 0.66). Our data suggest that the g.32373708 G>A-IRP1 and g.49520870 G>A-IRP2 polymorphisms may be associated with increased risk for AMD.

Catalytic activity of HKUST-1 coated on ceramic foam

The in situ preparation of a Cu-bearing metal-organic framework material, HKUST-1, coated on an open-cell ceramic foam (CF) is presented. The material used as coating is a robust metal-organic framework with a micro-porous structure that is a reminiscent of the zeolite framework topology. In spite of relatively low thermal stability of HKUST-1 with respect to zeolites, this material has an interesting catalytic behavior in the formation of hydroxyl radicals. The synthesized HKUST-1 coated on CF (HKUST-1/CF) samples has been characterized and then used to carry out the preliminary hydroxyl radicals formation from hydrogen peroxide (HP) decomposition and the consecutive phenol oxidation tests. The maximum phenol abatement obtained is 95% after about 40min, using a solution with an HP conversion of 70%. The HP kinetic data analysis has been done varying the reaction temperature in the range 60–80°C. The hierarchical micro/macro-porous catalytic system has been used for more than 40 consecutive reaction runs, maintaining the catalytic activity and showing a negligible copper leaching.

Progress on Hepatic Oxidative Damage Mediated by Iron Homeostasis Disregulation and Other Detrimental Factors and Antioxidative Protection Strategy

Iron is an essential metal in human nutrition.The unique activities of iron make it an important component of hemoglobin and various enzymes.However,excess iron can damage tissues by catalyzing the conversion of hydrogen peroxide to hydroxyl radicals,via the so-called Fenton reaction.The resulting free radicals would attack cell membranes,proteins,and DNA.As the major iron storage organ,liver plays a central role in maintenance of human iron homeostasis.Genetic disorder of iron metabolism in liver or external factors(i.e.infections of hepatitis C virus,hepatitis B virus and over-consumption of alcohol) will result in over-production of reactive oxygen species(ROS).The excess ROS would lead to oxidative stress and consequently result liver damage.Clinical studies have showed that patients with liver diseases administered with iron chelators or antioxidants may be effective treatment modalities.Therefore,study of iron metabolism and liver oxidative stress caused by iron overload or association with other risk factors will be of great clinical significance.

Characterization of Binding and Electron Transfer Between Shewanella Cytochrome C Peroxidase and its Monoheme Electron Donor C5

Bacterial diheme cytochrome c peroxidases are a critical part of the detoxification pathways in the periplasmic space that convert hydrogen peroxide to water. The turnover of peroxide requires a two-electron reduction, and these reducing equivalents must be delivered to the peroxidase by soluble electron transfer proteins. This study focuses on the diheme cytochrome c peroxidase from Shewanella oneidensis (So CcP). We have shown previously that a monoheme electron transfer protein from Shewanella oneidensis, So c5, is capable of both activating and turning over the So CcP protein during in vitro peroxidase assays. The nature of the protein-protein interface is not known, especially since two different molecules of So c5 must bind So CcP, either sequentially or simultaneously, during the catalytic cycle. We postulate that for efficient in vivo activity, oxidized So CcP should preferentially bind to the reduced So c5, and the interaction should weaken substantially once the electron has been transferred. In our current work, we show that charge-reversal amino acid mutations on the putative protein-protein interface failed to substantially change the Km for So c5 in peroxidase activity assays. However, surface charge-reversal mutations did have subtle effects consistent with changes in the electron transfer pathways as measured by protein film voltammetry. We further investigated the interaction between So c5 and So CcP using a surface acoustic wave binding method. Binding between So CcP and So c5 is very weak, with observed dissociation constants around 20 μM, and the interaction can be modulated by surface charge-reversal mutations. However, the rate of dissociation of oxidized So CcP from oxidized So c5 is surprisingly slow, suggesting our current models of the in vivo catalytic cycle of So CcP may need to be revisited.

Low-temperature bleaching of cotton induced by glucose oxidase enzymes and hydrogen peroxide activators

Glucose oxidase enzymes were used to produce hydrogen peroxide from glucose and oxygen in aqueous solutions. Different working conditions, that is, temperature, aeration with liquefied air, presence of cotton fibre and time of enzyme activity, were tested in order to obtain a solution with the highest possible concentration of hydrogen peroxide. The hydrogen peroxide produced was transformed into different peracids which could bleach the cotton fabric under mild conditions, at a pH between 7 and 8 and at a temperature of around 60°C. The conversion or activation of hydrogen peroxide was conducted with the bleach activators TAED, NOBS and TBBC. The concentrations of hydrogen peroxide and peracids in the solutions were measured with sodium thiosulphate titrations.The results indicated that the formation of hydrogen peroxide with glucose oxidase was effective under optimal conditions, which are 50°C, pH 4.6 and aeration. Convenient activators for the conversion of hydrogen peroxide into peracids were TAED and TBBC, which enabled attainment of a relatively high degree of whiteness at pH 7.5 and temperature 50°C. Using the activator NOBS under these conditions did not provide enough peracid to markedly improve whiteness.

Field-controlled electron transfer and reaction kinetics of the biological catalytic system of microperoxidase-11 and hydrogen peroxide

Controlled reaction kinetics of the bio-catalytic system of microperoxidase-11 and hydrogen peroxide has been achieved using an electrostatic technique. The technique allowed independent control of 1) the thermodynamics of the system using electrochemical setup and 2) the quantum mechanical tunneling at the interface between microperoxidase-11 and the working electrode by applying a gating voltage to the electrode. The cathodic currents of electrodes immobilized with microperoxidase-11 showed a dependence on the gating voltage in the presence of hydrogen peroxide, indicating a controllable reduction reaction. The measured kinetic parameters of the bio-catalytic reduction showed nonlinear dependences on the gating voltage as the result of modified interfacial electron tunnel due to the field induced at the microperoxidase-11-electrode interface. Our results indicate that the kinetics of the reduction of hydrogen peroxide can be controlled by a gating voltage and illustrate the operation of a field-effect bio-catalytic transistor, whose current-generating mechanism is the conversion of hydrogen peroxide to water with the current being controlled by the gating voltage.

Kinetics and mechanism of oxygen electroreduction on PtCoCr/C catalyst containing 20–40 wt % platinum

It is shown that the mechanism of oxygen electroreduction on the PtCoCr/C systems in 0.5 M H2SO4 is similar to that proposed for the Pt/C catalyst. The activity of ternary catalysts is by two and more times higher than that of monoplatinum catalyst. The constant k1 is much larger than k2 (k1 and k2 are the rate constants of O2 reduction to water and H2O2, respectively) for all catalysts studied. This indicates that the catalytic systems are selective with respect to O2 reduction immediately to water in the practically important potential range from 1.0 to 0.6 V. The yield of H2O2 increases with a shift of potential in the cathodic direction (<0.7 V) and does not exceed 1%. The sum of rate constants of further conversion of hydrogen peroxide also increases with a shift of potential in the cathodic direction. After a corrosion attack (a treatment in the acid for 24 h), a ratio between the rate constants (k1/k2) for the PtCoCr/C catalysts increases. This is caused by a considerable increase in k1, which is 2.84 × 10−2 cm/s for the catalyst containing 34 wt % Pt (against 1.5 × 10−2 cm/s for the untreated catalyst). This can be explained by the reaction proceeding on the particle surface, which was enriched in platinum in the course of corrosion treatment. The properties of platinum clusters on the alloy surface differ from those of monoplatinum as a result of the ligand effect. The amount of oxygen chemisorbed from water on this surface is lower than on Pt/C catalyst. This is the main factor determining an increase in the activity and stability of ternary catalysts.