High Concentrations Of H2O2 Research Articles

Study of Electrical Stimulation with Different Electric-Field Intensities in the Regulation of the Differentiation of PC12 Cells.

The strategy of using electrical stimulation (ES) to promote the neural differentiation and regeneration of injured nerves is proven feasible. Study of the possible molecular mechanisms in relation to this ES promotion effect should be helpful for understanding the phenomenon. In this study, it was identified that the neuronal differentiation of PC12 cells was enhanced when the electric field intensity was in the range of 30-80 mV/mm, and a lower or higher electric-field intensity displayed inferior effects. Under ES, however, levels of intracellular reactive oxygen species (ROS), intracellular Ca2+ dynamics, and expression of TREK-1 were measured as being gradually increasing alongside higher electric-field intensity. In trying to understand the relationship between the ES enhancement on differentiation and these variations in cell activities, parallel experiments were conducted by introducing exogeneous H2O2 into culture systems at different concentrations. Similarly, the effects of H2O2 concentration on the neuronal differentiation of PC12 cells, intracellular ROS and Ca2+ levels, and TREK-1 expression were systematically characterized. In comparative studies, it was found in two cases that ES of 50 mV/mm for 2 h/day and H2O2 of 5 μM in culture medium shared comparable results for intracellular ROS and Ca2+ levels and TREK-1 expression. Higher H2O2 concentrations (e.g., 10 and 20 μM) demonstrated adverse effects on cell differentiation and caused DNA damage. A stronger ES (e.g., 100 mV/mm), being associated with a higher intracellular ROS level, also resulted in weaker enhancement of the neuronal differentiation of PC12 cells. These facts suggested that the intracellular ROS generated under ES might be an intermediate signal transducer involved in cascade reactions relative to cell differentiation.

Oxidative stress as an indicator of niche-width preference of mangrove Rhizophora stylosa

Inundation, elevation gradient and salinity fluctuations are considered the major abiotic drivers that influence the growth and distribution of mangroves. In certain conditions, these environmental stressors trigger excessive generation of reactive oxygen species (ROS), affecting mangrove physiology and homeostasis, leading to oxidative stress and mortality if the condition remains exacerbated. As a natural defense to quench the deleterious effects of ROS, mangroves have developed an antioxidant system to scavenge the toxic effects of excessive ROS. This study investigated environmental stress due to salinity, inundation, and elevation gradient using the biochemical responses in the leaves of Rhizophora stylosa as an oxidative stress indicator in greenhouse experiments and field conditions. From the variations of biochemical responses and levels of oxidative stress, the niche-width preference was extrapolated. The results of the study showed that the observed environmental factors significantly induced the generation of high H2O2 concentrations in the leaves of R. stylosa, which in return activated the antioxidant defense system. Inundation of the whole plant imposed a higher-order oxidative stress compared with the effect of salinity in the greenhouse condition, as shown by the significant increase in H2O2, and even caused sublethal damage, as manifested by the chlorotic leaves when prolonged. In the field, rare inundation and high elevation are also considered stressful to R. stylosa, as shown by the significantly higher H2O2 levels compared with those in the frequently inundated (but plants not submerged) areas. The long-term negative effects of high H2O2 at the plant and community levels were manifested in the reduction of growth rate in plants cultured in the greenhouse and the reduction of height in the 30-year-old R. stylosa plantation. Integrating the levels of oxidative stress induced by salinity, inundation and elevation from both greenhouse experiments and field conditions, it appears that relatively low oxidative stress results in a preference of the niche-width of R. stylosa in inundated areas as long as the leaves remain emerged, even during the spring tide. Thus, this species typically dominates middle intertidal areas. These findings could have valuable implications for the selection of areas appropriate for mangrove rehabilitation.

Effect of different oxidative stress degrees generated by hydrogen peroxide on motility and DNA fragmentation of zebrafish (Danio rerio) spermatozoa.

An increase in reactive oxygen species (ROS) or decrease in antioxidant barriers can provoke lipid peroxidation of the membranes or DNA damage of the spermatozoa. The aim of this work is to study the effect of the different degrees of oxidative stress generated by H2 O2 incubation on total motility, kinetics, and DNA fragmentation of zebrafish (Danio rerio) spermatozoa. For this process, experimental groups were incubated in 50µM (Low; L) and 200µM (High; H) H2 O2 , respectively, for 20min at 4ºC. Sperm motility parameters were obtained with a computer-assisted sperm analysis (CASA) system. Sperm DNA fragmentation (SDF) was assessed using the sperm chromatin dispersion test. Both low and high H2 O2 concentration groups showed lower motility than control groups. Progressive motility of spermatozoa incubated in the H group dropped rapidly in comparison with other groups. Regarding SDF, the control and L groups had significantly lower values than the H group (25.0% and 31.6% vs. 48.1% fragmented sperm for C, L, and H groups, respectively; p<0.05). Sperm motility, mostly progressive motility, decreased as H2 O2 concentration increased, mainly when time after sperm activation increased. SDF increased as the H2 O2 concentration increased. However, measurements of the halo area did not agree with the subjective SDF rate.

Chronic exposure of the RAW246.7 macrophage cell line to H2O2 leads to increased catalase expression

Altered cellular redox states have been associated with a variety of chronic diseases, especially those correlated with inflammation. One of the primary oxidants generated during the inflammatory response is hydrogen peroxide (H2O2). Macrophages in particular are thought to produce large amounts of H2O2, however they must somehow protect themselves from the potentially lethal concentrations they produce. To investigate how immune cells protect themselves from H2O2 observed in chronic inflammatory diseases, we established an adapted population of macrophages in culture by gradually increasing sub-lethal concentrations of H2O2 in the media to typically lethal concentrations over the course of more than a month. The resulting cells were tolerant to very high concentrations of H2O2. Further investigation revealed that the cells were able to rapidly neutralize the H2O2 added to their culture media due to a dramatic upregulation of catalase. Interestingly, T cells, which are also implicated in chronic inflammation, were unable to adapt to H2O2 under the same procedure, however when T cells were cultured in media from adapted macrophages, they were able to survive typically lethal concentrations of H2O2. These data support the hypothesis that macrophages are able to protect themselves and neighboring cells during states of chronic inflammation from the oxidizing environment they create.

Characterisation of a monooxygenase in Shiraia bambusicola.

A monooxygenase-encoding gene (Mono) is located in the hypocrellin gene cluster of Shiraia sp. SUPER-H168 and was targeted by a clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system. The ΔMono mutant abolished hypocrellin production, whereas the ΔMono complement mutant restored hypocrellin production. Relative expression levels of the Mono and its adjacent genes were abolished in the ΔMono mutant compared with the wild-type strain. These results indicate the essential role of Mono in hypocrellin biosynthesis. The Mono gene of Shiraia bambusicola was further expressed in Pichia pastoris and salicylate monooxygenase activity was detected, which suggested that this monooxygenase has the ability to catalyse decarboxylative hydroxylation. The relative growth ratio of the ΔMono mutant was significantly improved compared with the wild-type strain. In contrast to the wild-type strain, the ΔMono mutant also represented excellent oxidative stress tolerance after exposure to high concentrations of H2O2 (16 mM) based on the increasing activities of superoxide dismutase, catalase, and glutathione peroxidase. These results suggest that ΔMono mutants could be used as microbial cell factories to produce metabolites that will cause oxidative stress. This study also enhances our understanding of hypocrellin biosynthesis and opens an avenue for decoding the hypocrellin pathway.

Oxidative degradation of polyamines by serum supplement causes cytotoxicity on cultured cells

Serum is a common supplement for cell culture due to it containing the essential active components for the growth and maintenance of cells. However, the knowledges of the active components in serum are incomplete. Apart from the direct influence of serum components on cultured cells, the reaction of serum components with tested drugs cannot be ignored, which usually results in the false conclusion on the activity of the tested drugs. Here we report the toxicity effect of polyamines (spermidine and spermine) on cultured cells, especially on drug-resistant cancer cell lines, which resulted from the oxidative degradation of polyamines by amine oxidases in serum supplement. Upon adding spermidine or spermine, high concentration of H2O2, an enzyme oxidation product of polyamines, was generated in culture media containing ruminant serum, such as fetal bovine serum (FBS), calf serum, bovine serum, goat serum or horse serum, but not in the media containing human serum. Drug-resistant cancer cell lines showed much higher sensitivity to the oxidation products of polyamines (H2O2 and acrolein) than their wild cell lines, which was due to their low antioxidative capacity.

Determination of the expression level of stress-related genes in Cicer arietinum root cell under Cd stress and the relationship to H2O2 concentrations.

In this study, stress-related gene expression levels and the concentrations of malondialdehyde (MDA) and hydrogen peroxide (H2O2), which are oxidative stress markers, were investigated in the chickpea (Cicer arietinum) plant's roots that are exposed to cadmium (Cd). MDA and H2O2 concentrations showed a linear increase. It was found that metallothionein-like gene (MT2) stress genes had a high level of expression at the 12-h application, while the kinetics of expression levels of glutathione reductase (GR1) and superoxide dismutase (Cu-Zn/SOD) genes increased until 24 h of application with a decrease in expression levels by 48 h of application. It has been observed that catalase (CAT) continues to be expressed at 24 and 48 h of Cd exposure. This study found that the expression of stress-related genes can be related to the oxidative status of the cell and the H2O2 concentration in the mechanism of signalization. This may up-regulate the expression of the stress genes until a certain concentration degree, while a higher concentration of H2O2 may down-regulate the gene expressions. The findings of this study may contribute to further oxidative signalling studies.

Debridement of Bacterial Biofilms with TiO2/H2O2 Solutions and Visible Light Irradiation.

Objectives The aim of the study was to explore the debridement efficacy of different solutions of H2O2 and rutile particles against Staphylococcus epidermidis and Pseudomonas aeruginosa biofilms attached to titanium surfaces when exposed to visible light. Materials and Methods Titanium discs cultivated with biofilms of Staphylococcus epidermidis or Pseudomonas aeruginosa were subjected for 1 min to suspensions consisting of rutile particles mixed with high (950 mM) or low (2 mM) concentrations of H2O2 under visible light irradiation (405 nm; 2.1 mW/cm2). Discs were rinsed and the degree of debridement was determined through scanning electron microscopy and viability assessment of the remaining bacteria using luminescence measurements and/or a metabolic activity assay. Results Cleaning mixtures containing the higher concentration of H2O2 showed a significantly improved debridement compared to the negative control in all experiments. The addition of rutile particles was shown to have a statistically significant effect in one test with S. epidermidis. Limited evidence of the catalytic effect of visible light irradiation was seen, but effects were relatively small and statistically insignificant. Conclusions H2O2 at a concentration of 950 mM proved to be the strongest contribution to the debridement and bactericidal effect of the cleaning techniques tested in this study.

The multiple roles of peroxiredoxins in tick blood feeding.

Hydrogen peroxide (H2O2) and hydroxyl radicals (HO·) are generated through partial reduction of oxygen. The HO· are the most reactive and have a shorter half-life than H2O2, they are produced from comparatively stable H2O2 through Fenton reaction. Although controlling HO· is important and biologically advantageous for organisms, it may be difficult. Ticks are obligate hematophagous arthropods that need blood feeding for development. Ticks feed on vertebrate blood containing high levels of iron. Ticks also concentrate iron-containing host blood, leading to high levels of iron in ticks. Host-derived iron may react with oxygen in the tick body, resulting in high concentrations of H2O2. On the other hand, ticks have antioxidant enzymes, such as peroxiredoxins (Prxs), to scavenge H2O2. Gene silencing of Prxs in ticks affects their blood feeding, oviposition, and H2O2 concentration. Therefore, Prxs could play important roles in ticks' blood feeding and oviposition through the regulation of the H2O2 concentration. This review discusses the current knowledge of Prxs in hard ticks. Tick Prxs are also multifunctional molecules related to antioxidants and immunity like other organisms. In addition, tick Prxs play a role in regulating the host immune response for ticks' survival in the host body. Tick Prx also can induce Th2 immune response in the host. Thus, this review would contribute to the further understanding of the tick's antioxidant responses during blood feeding and the search for a candidate target for tick control.

Effect of solution plasma process with hydrogen peroxide on the degradation of water-soluble polysaccharide from Auricularia auricula. II: Solution conformation and antioxidant activities in vitro

Synergistic degradation of water-soluble Auricularia auricula polysaccharide (AAP) by solution plasma process (SPP) in the presence of hydrogen peroxide (H2O2) was investigated. The effects of H2O2 concentration, AAP concentration and the distance between the electrodes on the degradation of AAP were evaluated. The results showed that higher H2O2 concentration, lower AAP concentration and narrower distance between the electrodes were favorable for the degradation effect. Particle size, congo red (CR), scanning electron micrographs (SEM) and atomic force microscopy (AFM) results confirmed that SPP irradiation with H2O2 improved significantly the flexibility of the conformation. The degraded AAPs exhibited greater metal chelating effects and DPPH radical scavenging effect than the original AAP. It concluded that the combined SPP/ H2O2 method could be used for preparation of low-molecular-weight AAP.

Construction of glucose and H2O2 dual stimuli-responsive polymeric vesicles and their application in controlled drug delivery

Herein, glucose and H2O2 stimuli-responsive vesicles are constructed based on host–guest interaction between a diblock copolymer, poly(ethylene glycol)-b-poly[3-acrylamidophenylboronic acid-co-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl acrylate], (PEG-b-P(PBA-co-PBEM), BCP for short) and α-cyclodextrin. In the presence of glucose, the vesicles are transformed to giant swollen spherical micelles because of the formation of a negatively charged tetravalent form between phenylboronic acid and glucose. On the other hand, the vesicles are totally disassembled when they are exposed to H2O2, which is due to the H2O2-mediated degradation of the pendant phenylboronic acid pinacol ester. The glucose and H2O2 stimuli-responsive vesicles are then applied in the controlled release of water-soluble anticancer drug, doxorubicin hydrochloride (DOX). Upon external stimuli, the DOX displays a faster release rate than that without stimuli. Moreover, the polymeric vesicles show an excellent cytocompatibility toward MCF-7 cells, and the drug-loaded vesicles exhibit a lower cytotoxicity than free drug toward cancer cells. The drug-loaded vesicles can be taken up by MCF-7 cells and further release the DOX in cancer cells due to the high glucose and H2O2 concentration in tumor cells, while they have negligible effect on normal cells, which may be important for applications in the therapy of cancers as a controlled-release drug carrier.

Determination of Concentrated Hydrogen Peroxide Free from Oxygen Interference at Stainless Steel Electrode

H2O2 is frequently used at high concentrations in various applications. It is very challenging to detect high concentrations of H2O2 and to eliminate oxygen interference for H2O2 detection through electrochemical reduction. In the present investigation, the electrochemistry of H2O2 at stainless steel electrode has been carried out for the first time. A cathodic peak for H2O2 reduction was observed at about -0.40 V, and no cathodic peak for dissolved oxygen reduction was observed on type 304 stainless steel electrode. Amperometric determination of H2O2 on type 304 stainless steel electrode displayed a linear range from 0.05 up to 733 mM with a detection limit of 0.02 mM (S/N = 3) and a sensitivity of 16.7 μA mM-1 cm-2. The type 304 stainless steel electrode not only shows much higher upper limit than other reported electrodes for the detection of concentrated H2O2 but also is free from oxygen interference, which is of great importance for practical applications. This method could detect H2O2 in wound wash and lake water with excellent recoveries. Moreover, we successfully applied the stainless steel electrode to determine glucose using glucose oxidase to catalyze the oxidation of glucose to generate hydrogen peroxide. The linear range for glucose is between 0.5 and 25 mM, which covers clinically important blood glucose concentrations well.

Effect of oxidation induced by hydroxyl radical‐mediated model on molecular structural and physical character of egg white powder

SummaryThe objective of this study was to determine structure and functional properties changes of oxidised egg white protein derived from hydrogen peroxide (H2O2)/ferric chloride (FeCl3) /ascorbic acid hydroxyl radical‐generating systems at room temperature, including carbonyls, sulfhydryl and total sulfhydryl groups, dityrosine, free amino, surface hydrophobicity, particle size distribution, intermolecular forces, and foamability and emulsibility. Protein carbonyl and dityrosine content of egg white protein were increased (P &lt; 0.05) with increasing the concentrations of H2O2. Oxidation decreased free sulfhydryl, total sulfhydryl groups and surface of hydrophobicity comparing with nonoxidised egg white protein. Oxidation also reduced its free amino content (P &lt; 0.05). The low concentration of H2O2 contributing the average particle size of egg white protein was smaller than the control group. However, the high concentrations of H2O2 caused that egg white protein aggregated and the average particle size became larger. To sum up, oxidation made EWP denaturation and aggregation.

Homogeneous surface oxidation and triangle patterning of monolayer MoS2 by hydrogen peroxide

Atomically thin monolayer molybdenum disulfides (MoS2) with tunable electronic structure has promising applications in opto-electronic devices and sensors. In this work, unique nano-patterning and surface oxidation of monolayer MoS2 was achieved based on hydrogen peroxide (H2O2) treatment. It was found that the exfoliated monolayer MoS2 can be uniformly oxidized when exposed to low-concentration H2O2, forming an intermediate phase composed of MoSxOy. In addition, patterned triangular pits with well-defined edges can be formed under high-concentration H2O2 condition. The band gap of monolayer MoS2 could be effectively modulated by H2O2 treatment as verified by photoluminescence spectra. This work shows that simple H2O2 treatment can be an alternative approach for both surface functionalization and band gap modulation of MoS2 flake, and it also provides an alternatively simple way to obtain patterned MoS2 nanostructures without complicated standard lithography processes.

Coumarin/BODIPY Hybridisation for Ratiometric Sensing of Intracellular Polarity Oscillation.

With different polarity responses, coumarin and 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) were hybridised to construct polarity fluorescent sensors, CBDP and iso-CBDP, to overcome the disadvantages of solvatochromic sensors in ratiometric polarity sensing. Only CBDP displayed an emission ratio (ICou /IBDP , coumarin to BODIPY emissions) that increased with an exponential dependence on medium relative permittivity over a wide polarity range (ϵr <57.9). This sensing ability of CBDP was not affected by medium pH; viscosity; and most intracellular species, especially reactive oxygen, nitrogen, and sulfur species. Apart from local cytoplasmic polarity quantification through lambda imaging, CBDP enables real-time ratiometric imaging for intracellular polarity oscillation induced by oxidative stimulation. Ratiometric polarity flow cytometry was developed, for the first time, with CBDP, which demonstrated that a high concentration H2 O2 induced cytoplasmic polarity enhancement, whereas pre-incubation with N-acetyl-l-cysteine inhibited this effect.

Selective flotation of chalcopyrite and molybdenite using H2O2 oxidation method with the addition of ferrous sulfate

Hydrogen peroxide (H2O2) has been used as an oxidizing agent in the selective flotation of chalcopyrite and molybdenite. However, this method required relatively high concentration of H2O2 to deliver flotation results (i.e., mineral grades and recoveries) comparable to those obtained by the conventional copper-molybdenum (Cu-Mo) ores flotation using sodium hydrosulfide (NaHS). Therefore, further improvements are needed to reduce the consumption of H2O2 reagent. In this study, ferrous sulfate (FeSO4) was used to enhance the oxidation performance of H2O2 through Fenton-like reactions. Flotation results showed that the consumption of H2O2 reagent could be reduced by the addition of FeSO4 without losing the flotation selectivity. The reason might be caused by increasing of oxidation performance as indicated by the increasing concentration of dissolved oxygen after the addition of FeSO4 into the H2O2 aqueous solution. Surface analysis using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) images showed that the surface of chalcopyrite was covered by more hydrophilic precipitates after the oxidation treatment using H2O2 aqueous solution with the addition of FeSO4, thus more hydrophilic surface and lower floatability. On the other hand, the surface of molybdenite was slightly oxidized and its surface remained hydrophobic as confirmed from contact angle results. Flotation tests using Cu-Mo bulk concentrate demonstrated that selective flotation might be possible using a mixture of FeSO4 and H2O2 aqueous solution. Moreover, this new method could be used as an alternative to copper depressant in Cu-Mo selective flotation, replacing the NaHS reagent.

Optimization of photo-Fenton process for the treatment of prednisolone

Prednisolone is a widely prescribed synthetic glucocorticoid and stated to be toxic to a number of non-target aquatic organisms. Its extensive consumption generates environmental concern due to its detection in wastewater samples at concentrations ranged from ng/L to μg/L that requests the application of suitable degradation processes. Regarding the actual treatment options, advanced oxidation processes (AOPs) are presented as a viable alternative. In this work, the comparison in terms of pollutant removal and energetic efficiencies, between different AOPs such as Fenton (F), photo-Fenton (UV/F), photolysis (UV), and hydrogen peroxide/photolysis (UV/H2O2), was carried out. Light diode emission (LED) was the selected source to provide the UV radiation. The UV/F process revealed the best performance, reaching high levels of both degradation and mineralization with low energy consumption. Its optimization was conducted and the operational parameters were iron and H2O2 concentrations and the working volume. Using the response surface methodology with the Box-Behnken design, the effect of independent variables and their interactions on the process response were effectively evaluated. Different responses were analyzed taking into account the prednisolone removal (TOC and drug abatements) and the energy consumptions associated. The obtained model showed an improvement of the UV/F process when treating smaller volumes and when adding high concentrations of H2O2 and Fe2+. The validation of this model was successfully carried out, having only 5% of discrepancy between the model and the experimental results. Finally, the performance of the process when having a real wastewater matrix was also tested, achieving complete mineralization and detoxification after 8h. In addition, prednisolone degradation products were identified. Finally, the obtained low energy permitted to confirm the viability of the process.

Peroxiredoxins are important for the regulation of hydrogen peroxide concentrations in ticks and tick cell line

Ticks are obligate hematophagous ectoparasites, as they need to feed blood from vertebrate hosts for development. Host blood contains high levels of iron. Host-derived iron may lead to high levels of reactive oxygen species (ROS), including hydrogen peroxide (H2O2). Since a high concentration of H2O2 causes serious damage to organisms, this molecule is known to be a harmful chemical compound for aerobic organisms. On the other hand, the transparent method is compatible with chemical fluorescent probes. Therefore, we tried to establish the visualizing method for H2O2 in unfed tick tissues. The combination method of a chemical fluorescent probe (BES-H2O2-Ac) with the transparent method, Scale, demonstrated in unfed tick tissues that H2O2 and paraquat could induce oxidative stress in the tissues, such as the midgut and ovary. In addition, an H2O2 detection method using BES-H2O2-Ac was established in Ixodes scapularis embryo-derived cell line (ISE6) in vitro to evaluate the antioxidant activity of peroxiredoxins (PRXs), H2O2 scavenging enzymes, against H2O2 in the cells. The effects of paraquat in ISE6 cells were also observed in the PRXs gene-silenced ISE6 cells. A high intensity of H2O2 fluorescence induced by paraquat was observed in the PRX gene-knockdowned cells. These results suggest that H2O2 and paraquat act as an H2O2 inducer, and PRX genes are important for the regulation of the H2O2 concentration in unfed ticks and ISE6 cells. Therefore, this study contributes to the search for H2O2 visualization in ticks and tick cell line and furthers understanding of the tick’s oxidative stress induced by H2O2.

Hydrogen Peroxide-Induced Oxidative Stress in Sugarcane and Response Expression Pattern of Stress-Responsive Genes Through Quantitative RT-PCR

Economic production of sugarcane is highly affected by oxidative stress due to biotic and abiotic stress factors. The main objective of this study was to determine which concentration of hydrogen peroxide can induce the oxidative stress conditions in sugarcane and determine whether several key gene expression responses reported in other species are triggered in sugarcane. Sixty-day-old sugarcane plants were sprayed with 30% H2O2 (300, 500 and 1000 ppm) for three consecutive days. Controls were maintained by spraying with water. Quantitative RT-PCR was performed to quantify the gene expression levels. The PCR products were cloned and sequenced to confirm the identity of the gene amplified. The representative sequences of the stress-responsive genes were deposited in GenBank (Acc. No KX828698 for HSP gene, KX828699 for APX gene, KX828700 for NAC transcription factor and KX828701 for ERF transcription factor). The expression pattern of stress-responsive key genes (HSP, NAC, ERF, GST, MYBAS and CAT) showed higher expression levels within 48 h of H2O2 treatment at 500 and 1000 ppm concentration. However, MYBAS transcription factor and catalase genes showed higher expression levels at a higher concentration of H2O2 (1000 ppm) of H2O2 at 48 h of treatment. Ascorbate peroxidase gene was up-regulated at 1000 ppm of H2O2 at 72 h of treatment. NAC transcription factor, heat shock proteins, ethylene-responsive factor and glutathione S-transferase showed a significant increase in expression at 500 ppm concentration of H2O2 at 48 h. Based on the expression pattern levels, 500 ppm of hydrogen peroxide at 48 h can induce the oxidative stress in sugarcane. The expression levels indicated that HSP, NAC, ERF, GST and MYBAS genes might play a role in signal transduction pathways, and APX and CAT are involved in scavenging reactive oxygen species.

Can dimedone be used to study selenoproteins? An investigation into the reactivity of dimedone toward oxidized forms of selenocysteine.

Dimedone is a widely used reagent to assess the redox state of cysteine-containing proteins as it will alkylate sulfenic acid residues, but not sulfinic acid residues. While it has been reported that dimedone can label selenenic acid residues in selenoproteins, we investigated the stability, and reversibility of this label in a model peptide system. We also wondered whether dimedone could be used to detect seleninic acid residues. We used benzenesulfinic acid, benzeneseleninic acid, and model selenocysteine-containing peptides to investigate possible reactions with dimedone. These peptides were incubated with H2 O2 in the presence of dimedone and then the reactions were followed by liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS). The native peptide, H-PTVTGCUG-OH (corresponding to the native amino acid sequence of the C-terminus of mammalian thioredoxin reductase), could not be alkylated by dimedone, but could be carboxymethylated with iodoacetic acid. However the "mutant peptide," H-PTVTGAUG-OH, could be labeled with dimedone at low concentrations of H2 O2 , but the reaction was reversible by addition of thiol. Due to the reversible nature of this alkylation, we conclude that dimedone is not a good reagent for detecting selenenic acids in selenoproteins. At high concentrations of H2 O2 , selenium was eliminated from the peptide and a dimeric form of dimedone could be detected using LCMS and 1 H NMR. The dimeric dimedone product forms as a result of a seleno-Pummerer reaction with Sec-seleninic acid. Overall our results show that the reaction of dimedone with oxidized cysteine residues is quite different from the same reaction with oxidized selenocysteine residues.