Hydrogen peroxide

ABSTRACT: A hydroponics experiment was carried out to study the role of hydrogen peroxide (H 2 O 2 ) through changes of oxidative stress and antioxidation activity in Salvinia natans Linn. H 2 O 2 is an active oxygen species, widely generated in many biological systems, and mediates various physiological and biochemical processes in plants. In this study, we demonstrated that exogenous H 2 O 2 causes the degradation of pigments and induces the oxidative stress and the antioxidation activity. These effects enhanced with increments of applied H 2 O 2 concentration. Application of polyamine reduced the generation and the accumulation of H 2 O 2 and modulated the enzyme activities.

In the present study, decomposition characteristics of hydrogen peroxide (6% by volume) inside a mini channel of 2.50 mm diameter with a silver catalyst is analysed experimentally. Various two phase flow patterns are observed. Slug flow pattern is observed for the majority of the flow rates considered in the experiment. The length of slug which gives the amount of oxygen formed for a specific flow rate is measured using image processing technique. The amount of oxygen collected experimentally shows that the reaction percentage can be enhanced further with proper design of the catalytic reactor. This method of generating oxygen and water at lower concentration of hydrogen peroxide can be used for precise thrust production after passing through mini/micro nozzles. More detailed studies are required to have increased reaction percentage by optimizing the design of catalytic reactor.

Bacillus pumilus is characterized by a higher oxidative stress resistance than other comparable industrially relevant Bacilli such as B. subtilis or B. licheniformis. In this study the response of B. pumilus to oxidative stress was investigated during a treatment with high concentrations of hydrogen peroxide at the proteome, transcriptome and metabolome level. Genes/ proteins belonging to regulons, which are known to have important functions in the oxidative stress response of other organisms, were found to be upregulated, such as the Fur, Spx, SOS or CtsR regulon. Strikingly, parts of the fundamental PerR regulon responding to peroxide stress in B. subtilis are not encoded in the B. pumilus genome. Thus, B. pumilus misses the catalase KatA, the DNA-protection protein MrgA or the alkyl hydroperoxide reductase AhpCF. Data of this study suggests that the catalase KatX2 takes over the function of the missing KatA in the oxidative stress response of B. pumilus. The genome-wide expression analysis revealed an induction of bacillithiol (Cys-GlcN-malate, BSH) relevant genes. An analysis of the intracellular metabolites detected high intracellular levels of this protective metabolite, which indicates the importance of bacillithiol in the peroxide stress resistance of B. pumilus.

Cardoso LM, Colombari DSA, Menani JV, Toney GM, Chianca Jr. DA, Colombari E. Cardiovascular responses to hydro- gen peroxide into the nucleus tractus solitarius. Am J Physiol Regul Integr Comp Physiol 297: R462–R469, 2009. First published June 10, 2009; doi:10.1152/ajpregu.90796.2008.—The nucleus tractus soli- tarius (NTS), a major hindbrain area involved in cardiovascular regulation, receives primary afferent fibers from peripheral barore- ceptors and chemoreceptors. Hydrogen peroxide (H 2 O 2 ) is a rela-

of reserve of carbohydrate in plants and the main source in the human diet due to its abundance in the nature. There no other food ingredient that can be compared with starch in terms of sheer versatility of application in the food industry. Unprocessed native starches are structurally too weak and functionally too restricted for application in today’s advanced food and industrial technologies. The main objective of this study was to compare the thermal behavior of native cassava starch and those treated with hydrogen peroxide, as well as those treated with hydrogen peroxide and ferrous sulfate. The cassava starch was extracted from cassava roots (Manihot esculenta, Crantz) and treated by standardized hydrogen peroxide (H 2 O 2 ) solutions at 1, 2 and 3% (with or without FeSO 4 ). Investigated by using they are thermoanalytical techniques: thermogravimetry - TG, differential thermal analysis – DTA and differential scanning calorimetry - DSC, as well as optical microscopy and X-ray powder diffractometry. The results showed the steps of thermal decomposition, changes in temperatures and in gelatinization enthalpy and small changes in crystallinity of the granules.

continuous system containing commercial iron wool, the process afforded almost total discolorization of aqueous solutions of three reactive azo-dyes (reactive orange 16, reactive black 5 and brilliant yellow 3G-P) at a hydraulic retention time of 2.5 min. At these conditions the hydrogen peroxide is almost totally consumed while the released total soluble iron reaches a concentration compatible with the current Brazilian legislation (15 mg L -1 ).

6. Schraufstatter IU, Hyslop PA, Hinshaw DB, Spaag RG, Sklar LA & Cochrane CG (1986). Hydrogen peroxide induced injury of cells and its prevention by inhibitors of poly (ADP-ribose) polymerase. Proceed- ings of the National Academy of Sciences, USA, 83: 4908-4912.

11. Nithart M, Alliot E, Salen-Picard C. Production, respiration and ammonia excretion of two polychaete species in a north Norfolk saltmarsh. J Mar Biol Ass U K 1999; 79: 1029-1037. 12. Cavaletto M, Ghezzi A, Burlando B, Evangelisti V, Ceratto N, Viarengo A. Effect of hydrogen peroxide on antioxidant enzymes and metallothionein level in the digestive gland of Mytilus galloprovincialis. cavalett@unipmn.it. Comp Bio- chem Physiol C Toxicol Pharmacol 2002; 131: 447-455. 13. Beutler E. The preparation of red cells for assay. In: Beutler

molecular parameters for hydrogen peroxide and its two (cis and trans) conformers were determined using the coupled-cluster level of theory, CCSD(T) and cc-pVX Z Dunning’s basis sets, which ranged from double- to quadruple-zeta quality. With the recourse to the same theoretical ab initio method combined with a quadruple-zeta basis set, cc-pVQZ, Koput et al. determined the anharmonic quartic force field and used the variational method to calculate the vibrational-rotational energy levels for the molecule [64] and for its various isotopomers [65]. The influence of the core-electron correlation on the molecular parameters and on the torsion potential energy were also studied [64] by employing both cc-pCVTZ and cc-pwCVTZ basis sets. Later, Malyszek and Koput [66] computed an enhanced version of the ground state potential using the conventional CCSD(T) and the explicitly correlated coupled-cluster method, CCSD(T)-F12, in conjunction with the augmented correlation-consistent basis sets, aug-cc-pVnZ, up to septuple-zeta quality. This highly accurate potential was applied to predict the vibrational-rotation energy levels of H 2 O 2 , D 2 O 2 and HOOD molecules [66] as well as highly excited rovibrational energy

by enhanced mutagenesis (1,2). Oxidative DNA damage induced by hydrogen peroxide is thought to occur through the Fenton reaction in the Haber-Weiss cycle. Our group and others have demonstrated (2-4) that pretreatment with the iron chelators 2-2’dipyridyl, 1-10 phenanthrolene or de- feroxamine protects E. coli cells against the lethal effect of H 2 O 2 , suggesting that ionic iron is the main transition metal

Tooth bleaching is one of the most popular treatments to achieve esthetic whitening and is considered a conservative, easily performed and relatively low-cost procedure (1). At-home bleaching is the most widely used bleaching technique for vital teeth, with recognized efficacy and biosafety (2). The patient uses carbamide peroxide gel at low concentrations under the supervision of a dentist. (3). Another alternative for vital tooth bleaching is the in-office technique, characterized by the use of products based on hydrogen peroxide (HP) in concentrations ranging from 20% to 38%. Obtaining fast results with immediate lightening effects through observation is the main marketing appeal that anchors the success of this technique (4). It is known that whatever the used bleaching agent, the active ingredient that will act in tooth structure is hydrogen peroxide, which should penetrate into the enamel and reach the dentin to produce the desired effect.

was carried out at different current densities by the constant current method. Cell voltage and concentration of hydrogen peroxide produced are monitored. Concentration of hydrogen peroxide produced was determined by the permanganate titration method [4]. Current efficiency of the process and specific power consumption are calculated. One drawback of porous cathodes is low gas utilization efficiency [5]. Theoretical oxygen requirement for this process is only 0.47 litre at STP per Ampere hour current passed. Effect of oxygen flow rate on the concentration of hydrogen peroxide formed and current efficiency are also studied. Addition of EDTA to the anolyte has been reported to increase current efficiency and to prevent fouling of the membrane [6]. So effect of EDTA dosage was also studied.

Background: The cyanobacterium Microcystis aeruginosa is one of the principal bloom-forming cyanobacteria present in a wide range of freshwater ecosystems. M. aeruginosa produces cyanotoxins, which can harm human and animal health. Many metabolic pathways in M. aeruginosa, including photosynthesis and microcystin synthesis, are controlled by its circadian rhythms. However, whether xenobiotics affect the cyanobacterial circadian system and change its growth, physiology and biochemistry is unknown. We used real-time PCR to study the effect of hydrogen peroxide (H 2 O 2 ) on the

Hydrogen peroxide is commonly described as a cytotoxic to a wide range of animal, plant and bacterial culture [67]. It is dangerous to mucosal cells, easily penetrating through membranes and causing, depending on their concentration, their apoptosis and necrosis [24].The LD50 (lethal dose of a compound that is needed to kill half of the population) value depends on the cell type, physiological state, length of exposure and concentration [70]. Even though, it is a normal metabolite aerobic cells. Hence, the elimination must be a quick process, engaging enzymes as catalases or peroxidases [42], [66].

CONSIDERATIONS ON THE HYDROGEN PEROXIDE ELECTROGENERATION. This paper presents some results that may be used as previous considerations to a hydrogen peroxide electrogeneration process design. A kinetic study of oxygen dissolution in aqueous solution is carried out and rate constants for oxygen dissolution are calculated. Voltammetric experiments on vitreous carbon cathode shown that the low saturation concentration drives the oxygen reduction process to a mass transfer controlled process which exhibits low values of limiting currents. Results have shown that the hydrogen peroxide formation and its decomposition to water are separated by 400 mV on the vitreous carbon surface. Diffusion coefficients for oxygen and hydrogen peroxide are calculated using data taken from Levich and Tafel plots. In a series of bulk electrolysis experiments hydrogen peroxide was electrogenerated at several potential values, and concentration profiles as a function of the electrical charged passed were obtained. Data shown that, since limiting current plateaus are poorly defined onto reticulated vitreous carbon, cathodic efficiency may be a good criterion for choosing the potential value in which hydrogen peroxide electrogeneration should be carried out.

Fernández-Santos MR., Domínguez-Rebolledo AE, Esteso MC, Garde JJ, Martínez-Pastor F. 2008. Catalase supplementation on thawed bull spermatozoa abolishes the detrimental effect of oxidative stress on motility and DNA integrity. Int J Androl, 32:353-359. Garg A, Kumaresan A, Ansari MR. 2009. Effects of hydrogen peroxide (H 2 O 2 ) on fresh and cryopreserved

SCE can be observed, that indicate a electrocatalytic process by metal centers of the conducting polymer. The electrocatalytic mechanism was based on reduction of the Mn IV ions then undergoes a catalytic reduction by the hydrogen peroxide molecular in solution to the Mn III ions (Eq. 1), which can then be electrochemically re-oxidized to produce an enhancement of the anodic current (Eq. 2).

Hydrogen peroxide is an important reactive oxygen species (ROS) that arises either during the aerobic respiration process or as a by-product of water radiolysis after exposure to ionizing radiation. The reaction of hydrogen peroxide with transition metals imposes on cells an oxidative stress condition that can result in damage to cell components such as proteins, lipids and principally to DNA, leading to mutagenesis and cell death. Escherichia coli cells are able to deal with these adverse events via DNA repair mechanisms, which enable them to recover their genome integrity. These include base excision repair (BER), nucleotide excision repair (NER) and recombinational repair. Other important defense mechanisms present in Escherichia coli are OxyR and SosRS anti-oxidant inducible pathways, which are elicited by cells to avoid the introduction of oxidative lesions by hydrogen peroxide. This review summarizes the phenomena of lethal synergism between UV irradiation (254 nm) and H 2 O 2 , the cross-adaptive

Increasing evidence demonstrates that redox states are critical for the regulation of PD-mediated transport. Our findings have now unambigiously established a direct genetic link between a hydrogen peroxide-producing type III peroxidase and the regulation of small RNA-mediated silencing mobility. Manipulation of hydrogen peroxide levels in vivo and in vitro altered silencing movement in two independent systems: our root-to-shoot systemic silencing system; RtSS, and the cell-to-cell short distance silencing system; and AtSuc2-PDS. These results strongly support the conclusion that hydrogen peroxide plays a role in the control of silencing signal movement. Considering the role of ROS in regulating the movement of other signals, we can reasonably envisage that this mechanism may be more widespread than previously thought, extending beyond the role of H 2 O 2 in stress

Os experimentos de contagem bacteriana foram realizados com o objetivo de examinar a carga microbiana nas amostras de água sem adição de biocidas e quando tratadas com cloro [r]