Low Concentrations Of Hydrogen Peroxide Research Articles

A clinical, randomized study on the influence of dental whitening on Streptococcus mutans population.

Dental whitening with peroxides has been popularized through the at-home technique, which employs low concentrations of peroxide applied in individual trays. However, there are few clinical trials reporting the effects of its continuous use on oral microbiota. Thus, the purpose of the present clinical, randomized study was to evaluate the influence of at-home whitening treatment on Streptococcus mutans in saliva, buccal mucosa, and subgingival and supragingival plaque. Thirty volunteers were randomly divided into two study groups (N=15) according to the whitening therapy: G CP, whitening using 10% carbamide peroxide 4h daily for 21days; and G HP, whitening using 6% hydrogen peroxide 1.5h daily for 21days. Samples from the predetermined locations were collected at three evaluation periods: T1, before; T2, immediately after; and T3, 30days after the beginning of the treatment. The microbiological evaluation was made using conventional and molecular methods. Student's t-test demonstrated a statistically significant decrease in S.mutans population in the subgingival and supragingival plaque for HP samples between T1 and T2 no difference was found between T1 and T3 regardless of the location and the whitening product used (α=0.05). Although HP reduced S.mutans during treatment, the levels returned to baseline when assessed 30days after the treatment.

Nanobubble Water's Promotion Effect of Barley (Hordeum vulgare L.) Sprouts Supported by RNA-Seq Analysis.

The physiological promotion effect of nanobubble (NB) water on living organisms is still a poorly understood phenomenon which was discovered 1 decade ago. Here, we analyzed the barley (Hordeum vulgare L.) embryo transcriptome following the exposure to NB water and low-concentration hydrogen peroxide (H2O2) using RNA-Seq. We found that 349 genes were differentially expressed after 24 h exposure to NB water and 97 genes were differentially expressed after exposure to H2O2 solution. Gene ontology enrichment and cluster analyses revealed that NB water induced expression of genes related to cell division and cell wall loosening. RNA-Seq, quantitative real-time polymerase chain reaction, and enzyme activity measurements all pointed to gene-encoding peroxidases as a major factor responsible for the effects of physiological enhancement due to NB water. The exogenous hydroxyl radical (•OH) produced by NB water significantly increased the expression of genes related to peroxidase and NADPH, thus leading to an increased endogenous superoxide anion (O2•-) inside the barley seed. Appropriately, low concentrations of exogenously added reactive oxygen species (ROS) and endogenous ROS played important roles in plant growth and development. When ROS levels were low, the endogenous ROS was eliminated by ascorbate peroxidase and other peroxidases instead of activating the catalase and superoxidase dismutase. This data set will serve as the foundation for a system biology approach to understand physiological promotion effects of NB water on living organisms.

Inconclusive evidence about the comparative effectiveness of a low concentration hydrogen peroxide bleaching agent catalyzed by titanium dioxide nanoparticles with a high concentration peroxide control

Inconclusive evidence about the comparative effectiveness of a low concentration hydrogen peroxide bleaching agent catalyzed by titanium dioxide nanoparticles with a high concentration peroxide control

Jab1/Csn5-Thioredoxin Signaling in Relapsed Acute Monocytic Leukemia under Oxidative Stress.

Purpose: High levels of ROS and ineffective antioxidant systems contribute to oxidative stress, which affects the function of hematopoietic cells in acute myeloid leukemia (AML); however, the mechanisms by which ROS lead to malignant transformation in relapsed AML-M5 are not completely understood. We hypothesized that alterations in intracellular ROS would trigger AML-M5 relapse by activating the intrinsic pathway.Experimental Design: We studied ROS levels and conducted c-Jun activation domain-binding protein-1 (JAB1/COPS5) and thioredoxin (TRX) gene expression analyses with blood samples obtained from 60 matched AML-M5 patients at diagnosis and relapse and conducted mechanism studies of Jab1's regulation of Trx in leukemia cell lines.Results: Our data showed that increased production of ROS and a low capacity of antioxidant enzymes were characteristics of AML-M5, both at diagnosis and at relapse. Consistently, increased gene expression levels of TRX and JAB1/COPS5 were associated with low overall survival rates in patients with AML-M5. In addition, stimulating AML-M5 cells with low concentrations of hydrogen peroxide led to increased Jab1 and Trx expression. Consistently, transfection of ectopic Jab1 into leukemia cells increased Trx expression, whereas silencing of Jab1 in leukemia cells reduced Trx expression. Mechanistically, Jab1 interacted with Trx and stabilized Trx protein. Moreover, Jab1 transcriptionally regulated Trx. Furthermore, depletion of Jab1 inhibited leukemia cell growth both in vitro and in vivoConclusions: We identified a novel Jab1-Trx axis that is a key cellular process in the pathobiologic characteristics of AML-M5. Targeting the ROS/Jab1/Trx pathway could be beneficial in the treatment of AML-M5. Clin Cancer Res; 23(15); 4450-61. ©2017 AACR.

Screening and Selection of Twenty Iranian Wheatgrass Genotypes for Tolerance to Salinity Stress during Seed Germination and Seedling Growth Stage

Desert wheatgrass (Agropyron desertorum L.), tall wheatgrass (Agropyron elongatum L.), and crested wheatgrass (Agropyron cristatum L.) are native cool-season grass species that exhibit potential as a low-input turfgrass. An increased understanding of the biochemical and physiological responses of wheatgrass species and genotypes to salt stress conditions is important for developing genotypes with enhanced tolerance to salinity. The objective of this study was to characterize the physiological and antioxidative properties in 20 Iranian wheatgrass genotypes and to observe their responses to salinity stress during seed germination and seedling growth stage. A completely randomized factorial design was used with two types of factors, four levels of salinity (0, 50, 100, and 150 mm of NaCl), wheatgrass genotypes, and three replicates. In this experiment, the results demonstrated that salinity limits the germination of Iranian wheatgrass genotype seeds. The result of this study showed that among the wheatgrass genotypes, ‘AD1’, ‘AD3,’ ‘AC6’, and ‘FA’ took the shortest average time to germinate. Higher levels of final germination percentage (FGP) were observed in ‘AD2’, ‘AD3’, and ‘AE5’ under salinity stress than other genotypes throughout the experiment. During a prolonged period of study, ‘AD1’ had greater rate of germination (GR) than other genotypes. Out of the 21 genotypes, five genotypes (‘AD1’, ‘AD2’, ‘AD3’, ‘AE5’, and ‘FA’ genotypes) were in the range of “salinity tolerant genotypes” cluster. The ‘AD1’, ‘AD2’, ‘AD3’, ‘AE5’, and ‘FA’ genotypes generally performed better than other genotypes under salinity conditions, mainly through maintaining higher enzymatic activities such as superoxide dismutase (SOD) (EC 1.15.1.1), catalase (CAT) (EC 1.11.1.6), ascorbate peroxidase (APX) (EC 1.11.1.11) and peroxidase (POD) (EC 1.111.1.7), and nonenzymatic antioxidant activities by glutathione (GSH). The ‘AD1’, ‘AD2’, ‘AD3’, ‘AE5’, and ‘FA’ genotypes also had higher proline levels and more of total nonstructural carbohydrates (TNC) content, lower malondialdehyde (MDA) content, and lower hydrogen peroxide content (H2O2).

Quantitative analysis of hemin-induced neutrophil extracellular trap formation and effects of hydrogen peroxide on this phenomenon

Formation of neutrophil extracellular traps (NETs) can perpetuate sterile inflammation; thus, it is important to clarify their pathophysiological characteristics. Free heme, derived via hemolysis, is a major contributor to organ damage, and reportedly induces neutrophil activation as well as reactive oxygen species (ROS) production and NET formation. For this study, we examined hemin (Fe3+ -protoporphyrin IX)-induced NET formation quantitatively in vitro as well as the effects of oxidative stress.NETs formed in vitro from cultured neutrophils were quantitatively detected by using nuclease treatment and Sytox Green, a nucleic acid stain. Hemin-induced NET production was found to be in a dose-dependent manner, NADPH oxidase-dependent and toll-like receptor (TLR)-4 independent. Additionally, the iron molecule in the porphyrin ring was considered essential for the formation of NETs. In the presence of low concentrations of hydrogen peroxide, low concentrations of hemin-induced NETs were enhanced, unlike those of phorbol myristate acetate (PMA)-induced NETs.Quantitative analysis of NET formation may prove to be a useful tool for investigating NET physiology, and hemin could function as a possible therapeutic target for hemolysis-related events.

Teeth bleaching with low concentrations of hydrogen peroxide (6%) and catalyzed by LED blue (450 ± 10 nm) and laser infrared (808 ± 10 nm) light for in-office treatment: Randomized clinical trial 1-year follow-up.

The aim of this study was to evaluate color longevity after a year of in-office bleaching with gel (6% hydrogen peroxide HP, LED blue/laser infrared activation system) compared to a 35% control concentration in a split-mouth study model. Thirty-one patients were initially treated. The bleaching procedure with 6% or 35% gel HP was performed randomly in the upper half arcade of each patient. The color was measured at baseline and at 1 week, 1 month, and 1 year using the spectrophotometer Vita Easyshade, Vita Bleached, and Vita classical Shade guide organized by value. During the 1-year recall, the color was assessed before and after dental prophylaxis. Only 27 patients were assessed in the 1-year recall. There was a significant difference in the ΔE between the two groups at all times assessed (P < .011). The ΔL, Δa, and Δb showed significant difference between both groups at all assessed times (P < .038). There was no significant difference between the ΔSGU at all times (P > .05) except for the Vita bleachedguide postprophylaxis comparison (P < .05). The two compounds remained effective at 1year. When objectively evaluated, color difference between groups was found, not seen when subjectively determined. A low concentration hydrogen peroxide bleaching agent can reach good clinical results at 1year of follow-up.

Method for preparing caprolactam by using a microreactor under Lewis acid catalysis

We establish the fact that in a continuous-flow scalable photoreactor system employed for the homogeneous photolysis of H2O2 into .OH radicals, the quantum yield of photolytic conversion in aqueous solution cannot be regarded as a linear function of H2O2 initial concentration. We were successful in repeatedly producing high concentrations of .OH radical (between 40 and 90 mM) from relatively low concentrations of hydrogen peroxide (between 0.1 M − 5 M) in aqueous solution in a scalable manner using our serially connected photoreactor system. Our investigation demonstrates that merely selecting a very high initial concentration of H2O2 will not necessarily result in the highest conversion into .OH radical. We also developed a simple and in-situ acid-base titrimetric method for quantitation of .OH radicals and demonstrated an accuracy of our method within ~±6.6% of a 31P NMR method. Hence, our proposed scalable .OH radical production method via continuous-flow photoreactors can be regarded as a safe, simple, accurate and cost-effective technique for various industrial processes, particularly in aquaculture and swimming pool disinfection, as a replacement of high concentrations of hazardous oxidisers.

Crucial roles of reactive chemical species in modification of respiratory syncytial virus by nitrogen gas plasma

The exact mechanisms by which nanoparticles, especially those composed of soft materials, are modified by gas plasma remain unclear. Here, we used respiratory syncytial virus (RSV), which has a diameter of 80–350nm, as a model system to identify important factors for gas plasma modification of nanoparticles composed of soft materials. Nitrogen gas plasma, generated by applying a short high-voltage pulse using a static induction (SI) thyristor power supply produced reactive chemical species (RCS) and caused virus inactivation. The plasma treatment altered the viral genomic RNA, while treatment with a relatively low concentration of hydrogen peroxide, which is a neutral chemical species among RCS, effectively inactivated the virus. Furthermore, a zero dimensional kinetic global model of the reaction scheme during gas plasma generation identified the production of various RCS, including neutral chemical species. Our findings suggest the nitrogen gas plasma generates RCS, including neutral species that damage the viral genomic RNA, leading to virus inactivation. Thus, RCS generated by gas plasma appears to be crucial for virus inactivation, suggesting this may constitute an important factor in terms of the efficient modification of nanoparticles composed of soft materials.

Fabrication of Protein Films from Genetically Engineered Silk-Elastin-Like Proteins by Controlled Cross-Linking.

Protein films are an important class of materials for applications in biomedicine and biotechnology. The rational design of protein polymer sequence and selection of customized cross-linking offers unique opportunities to engineer desirable functionalities into these materials. Here we report the fabrication of a series of films with tunable physiochemical properties from genetically engineered silk-elastin-like proteins (SELPs). The SELPs were recombinantly biosynthesized with different ratios of silk-to-elastin blocks and periodic cysteine residues incorporated in the elastin blocks. A disulfide cross-linking method was developed for the preparation of the SELP films under mild oxidative conditions with a low concentration of hydrogen peroxide, in comparison with the physical cross-linking method used with the organic solvent methanol. Film properties were characterized for solubility, water absorption, hydrophilicity, surface roughness, and cyto-compatibility. The results indicated that customized cross-linking supported the fabrication of films from the SELP proteins with tunable features, including smooth, water stable film materials with cyto-compatibility. Interestingly, hydrogen peroxide oxidation was a preferred cross-linking method for the cysteine-containing SELPs with a low ratio of the silk-to-elastin blocks, whereas methanol treatment was suitable for fabricating films from the SELPs with a high ratio of silk-to-elastin blocks into stable films with rougher surfaces. We anticipate that an appropriate combination of polymer design and cross-linking might be a useful strategy for the preparation of protein films for diverse applications.

Effect of residence time on micropollutant removal in WWTP secondary effluents by continuous solar photo-Fenton process in raceway pond reactors

The removal of micropollutants (MPs) in wastewater treatment plants (WWTPs) secondary effluents by solar photo-Fenton is commonly carried out with low concentrations of iron and hydrogen peroxide due to the low pollutant concentration (ngL−1). This led to two main consequences being observed: short treatment times (tens of minutes) and excess of photons when using 5cm-diameter tubular reactors. To make better use of most of the photons reaching the reactor surface, the use of raceway pond reactors (RPRs) with longer light path length was implemented successfully. However, little attention was paid to the treatment time itself and the photo-Fenton process was applied in batch mode despite filling and emptying stages being much longer than reaction time. This paper deals with the performance of the solar photo-Fenton process in RPRs operated in continuous mode to remove MPs in WWTP secondary effluents. In this regard, first the continuous degradation of a model emerging contaminant, the pesticide Acetamiprid (ACTM), was studied in a synthetic secondary effluent at pH 2.8. Next, real secondary effluents were treated at two liquid depths, 5 and 15cm and three hydraulic residence times (HRTs), 80, 40 and 20min. Reactant concentrations were 5.5mgL−1 Fe2+ and 30mgL−1 H2O2 giving rise to a treated wastewater volume of 450Lm−2day−1 for a 5cm-deep RPR operated in continuous mode at 40min HRT for 6h a day in winter, with 84% MP removal and 66% hydrogen peroxide conversion. As far as the authors know, this is the first report on the solar photo-Fenton process operated in continuous mode displaying its advantages with regard to the batch operation.

Cluster of Differentiation 36 Deficiency Aggravates Macrophage Infiltration and Hepatic Inflammation by Upregulating Monocyte Chemotactic Protein-1 Expression of Hepatocytes Through Histone Deacetylase 2-Dependent Pathway.

Cluster of differentiation 36 (CD36) is involved in the development of nonalcoholic steatohepatitis (NASH). Excess CD36 facilitates liver cells taking fatty acid and activates inflammatory signals to promote hepatic steatosis and inflammation. However, CD36 deficiency paradoxically promotes nonalcoholic fatty liver disease by unknown mechanisms. We explored the probable molecular mechanism of hepatic inflammation induced by CD36 deficiency. CD36 deletion in mice (CD36-/- mice) specifically increased monocyte chemotactic protein-1 (MCP-1) in hepatocytes, promoted macrophage migration to the liver, and aggravated hepatic inflammatory response and fibrosis. The nuclear expression of histone deacetylase 2 (HDAC2), which highly expresses in wild-type hepatocytes and has an inhibitory effect on acetyl histone 3 (H3), was reduced in CD36-deficient hepatocytes. Consequently, the level of acetyl H3 binding to MCP-1 promoters was increased in CD36-deficient hepatocytes, causing hepatic-specific MCP-1 transcriptional activation. Reduction of nuclear HDAC2 in both CD36-/- mice liver and cultured hepatocytes was due to reduction of intracellular reactive oxygen species (ROS) level, while supplement of low-concentration hydrogen peroxide (H2O2) overcame the suppression of HDAC2 caused by CD36 deficiency, decreasing MCP-1 gene transcription and microphage migration. Our results provide first evidence that decreased ROS production by CD36 deletion was also harmful for livers. The fine balance of CD36 plays an important role in maintaining balances of hepatic ROS and nuclear HDAC2, which could be a potential new therapeutic strategy for the prevention of NASH development. CD36 deficiency promoted the development of NASH by facilitating the transcription of MCP-1 in hepatocytes due to the reduction of ROS and nuclear HDAC2. Antioxid. Redox Signal. 00, 000-000.

Effect of Annealing on Nano crystalline ZnO Thin Film Developed by Electro deposition Method

ZnO is a II–VI compound semiconductor with wide bang gap and hexagonal wurtzite structure. Zinc oxide films were deposited by electrodeposition technique, containing very low concentrations of sodium citrate and hydrogen peroxide. Ammonium hydroxide were added to control the reaction. The as deposited films were annealed in air at 400°C The analysis were initially studied with X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM) and Optical properties. The average grain size is measured to be 48nm.The grains are spherical, well connected and uniformly distributed. The energy band gap is found to be 3.35 eV in as deposited case and 3.23 eV in annealed case.

56 - Novel Redox-Dependent Esterase Activity for DJ-1: Implications for Parkinson's Disease

Mutations in human DJ-1 (hDJ-1) are associated with early- onset autosomal recessive forms of Parkinson’s disease (PD). hDJ-1 is a multi-functional protein that functions as an oxidative sensor, transcription factor, protease, deglycase and glyoxalase. hDJ-1 contains a conserved cysteine protease domain. Given that cysteine proteases can act on both amide and ester substrates, we surmised that hDJ-1 possesses cysteine- mediated esterase activity. To test this hypothesis, hDJ-1 was overexpressed, purified and tested for esterase activity towards p- nitrophenyl-acetate (pNPA). hDJ-1 showed esterase activity (Vmax= 235.10 ± 12.00), with a sigmoidal fit (S 0.5 = 0.55 ±0.040 mM) and positive cooperativity (Hill-coefficient of 2.05 ± 0.28). A PD-associated mutant of DJ-1 (M26I) lacked activity. Unlike its protease activity which is inactivated by reactive oxygen species (ROS), esterase activity of hDJ-1 is enhanced upon exposure to low concentrations of hydrogen peroxide ( 100 µM) suggesting that its activity is resistant to oxidative stress. Esterase activity of DJ-1 requires the oxidation of catalytic cysteines, as chemically protecting cysteines blocks its activity whereas an oxido-mimetic mutant of DJ-1 (C106D) exhibited robust esterase activity. Redox-dependent activation of esterase activity is specific for DJ-1 as treating porcine pancreatic lipase, a serine protease, did not show enhanced esterase activity when treated with hydrogen peroxide. Finally, molecular docking studies suggested that C106 and L126 within the catalytic site of hDJ-1 interact with esterase substrates. Ongoing cell culture studies will elucidate the extent by which the esterase activity of DJ-1 plays a cytoprotective role in primary neurons treated with ROS (hydrogen peroxide). This study is the first to report intrinsic redox-sensitive esterase activity for hDJ-1. Overall, our results suggest that the esterase activity of DJ-1 plays a role in conferring cytoprotection during oxidative stress.

Problems and Solutions in Click Chemistry Applied to Drug Probes.

Small-molecule fluorescent probes have been widely used in target identification, but this method has many disadvantages. For example, the identified proteins are usually complex, and additional biochemical studies are needed to distinguish real targets from interference results. To address this problem, we propose a series of strategies for improving the efficiency of target identification. First, pretreatment with a lower concentration of hydrogen peroxide can shield against thiol interference. Second, the use of benzophenone as a photo-affinity group is not appropriate, and diazirines are preferred. Third, if cytoskeleton proteins or stress proteins are captured, the interference must be carefully eliminated. The specificity of target identification can be improved by optimizing these three strategies. In this paper, we discuss the problems associated with the use of the click reaction in living cells and provide important complementary techniques for photo-affinity probes based on the click chemistry reaction.

Rationally Designed Redox-Sensitive Protein Hydrogels with Tunable Mechanical Properties.

Protein hydrogels are an important class of materials for applications in biotechnology and medicine. The fine-tuning of their sequence, molecular weight, and stereochemistry offers unique opportunities to engineer biofunctionality, biocompatibility, and biodegradability into these materials. Here we report a new family of redox-sensitive protein hydrogels with controllable mechanical properties composed of recombinant silk-elastin-like protein polymers (SELPs). The SELPs were designed and synthesized with different ratios of silk-to-elastin blocks that incorporated periodic cysteine residues. The cysteine-containing SELPs were thermally responsive in solution and rapidly formed hydrogels at body temperature under physiologically relevant, mild oxidative conditions. Upon addition of a low concentration of hydrogen peroxide at 0.05% (w/v), gelation occurred within minutes for the SELPs with a protein concentration of approximately 4% (w/v). The gelation time and mechanical properties of the hydrogels were dependent on the ratio of silk to elastin. These polymer designs also significantly affected redox-sensitive release of a highly polar model drug from the hydrogels in vitro. Furthermore, oxidative gelation was performed at other physiologically relevant temperatures, and this resulted in hydrogels with tunable mechanical properties, thus, providing a secondary level of control over hydrogel stiffness. These newly developed injectable SELP hydrogels with redox-sensitive features and tunable mechanical properties may be potentially useful as biomaterials with broad applications in controlled drug delivery and tissue engineering.

Low-concentration hydrogen peroxide can upregulate keratinocyte intracellular calcium and PAR-2 expression in a human keratinocyte-melanocyte co-culture system.

Hydrogen peroxide (H2O2) may have a biphasic effect on melanin synthesis and melanosome transfer. High H2O2 concentrations are involved in impaired melanosome transfer in vitiligo. However, low H2O2 concentration promotes the beneficial proliferation and migration of melanocytes. The aim of this study was to explore low H2O2 and its mechanism in melanosome transfer, protease-activated receptor-2 (PAR-2) expression and calcium balance. Melanosomes were fluorescein-labeled for clear visualization of their transfer. The expression of protease-activated receptor-2 (PAR-2) in keratinocytes was determined by western blot analysis. Flow cytometry was employed to evaluate the effects of H2O2 on calcium levels in keratinocytes. Fluorescence microscopy showed the upregulation of melanosome transfer into keratinocytes following 0.3mM H2O2 treatment in the co-cultures rather than in the untreated control groups, which was associated with higher expression of PAR-2 protein and increased calcium concentration. The addition of a PAR-2 antagonist inhibited the positive activity of H2O2 and calcium flow in keratinocytes. When calcium flow was blocked by a calcium chelator, the addition of H2O2 did not increase the PAR-2 expression level in keratinocytes, therefore, inhibiting dendrite formation and melanosome transfer. Low H2O2 concentration promotes melanosome transfer with increased PAR-2 expression level and calcium concentration in keratinocytes. In addition, the interaction between melanocytes and keratinocytes is more beneficial to enhance calcium levels in keratinocytes which mediate melanin transfer. Moreover, low H2O2 concentration promotes dendrite formation, in which extracellular calcium and Par-2 were involved.

A reactive extrusion process with the aid of ultrasound for preparing cross-linked polypropylene

Introducing the cross-linked structure in polypropylene (PP) was highly desired to meet the requirement of high melt strength, which was a key for the application of PP in thermoforming, blow molding and foaming where elongation flows dominated. In this work, the power ultrasound was introduced into the reactive extrusion at the exit die of an extruder for preparing cross-linked PP. The main target was to maintain the highly cross-linked structure during reactive extrusion process in case of low peroxide concentration. The results of the dynamic rheological properties, melt flow index, and extensional viscosity measurement showed that the content of PP gel and the melt strength of PP increased obviously with the employment of a 300 W ultrasound while the contents of functional monomers and peroxide were constant. Fourier transform-infrared spectroscopy analysis, differential scanning calorimeter characterization, and gel permeation chromatograph measurement proved that the increases of content of PP gel and melt strength of PP were caused by that the ultrasonic waves could induce the chain scission and recombination reaction when the PP melts flowed through the exit die assembled with a ultrasonic probe. POLYM. ENG. SCI., 2016. © 2016 Society of Plastics Engineers

Longevity, Esthetic Perception, and Psychosocial Impact of Teeth Bleaching by Low (6%) Hydrogen Peroxide Concentration for In-office Treatment: A Randomized Clinical Trial.

The aim was to evaluate the color longevity after nine months of in-office bleaching with gel (6% hydrogen peroxide), to compare this to a control concentration of 35% in a split-mouth study model, and to assess the dental confidence and psychosocial impact on patients. Twenty-seven patients were assessed at the nine-month recall. The bleaching procedure with 6% or 35% hydrogen peroxide gel was performed randomly in the upper hemi-arch of each patient. The color was measured at baseline and at one week, one month, and nine months after the procedure, using the Vita Easyshade spectrophotometer, the Vita classical shade guide organized by value, and Vita Bleach Guide 3DMaster. Moreover, two surveys, OHIP-Esthetics and PIDAQ, were used to assess the esthetic self-perception and psychosocial impact of the bleaching procedure. During the nine-month recall, the color was assessed before and after dental prophylaxis. Twenty-seven patients participated in the nine-month recall. There was a significant difference in ΔE between the two groups at all times assessed (p<0.011). The ΔL, Δa, and Δb showed a difference between the two groups at all times assessed (p<0.038), except for ΔL from the baseline vs nine-month after prophylaxis value (p>0.20). There was no significant difference in ΔSGU at all times (p>0.05). There was a significant difference in OHIP-Esthetics and PIDAQ sums compared with baseline scores (p<0.03). The two compounds remained effective at nine months, with a slight rebound of color, and maintained their objective color difference but not the subjective color difference. Patients were satisfied with the bleaching procedure, and this had a positive impact on esthetic perception and a positive psychosocial impact at the nine-month recall.

Novel Redox-Dependent Esterase Activity (EC 3.1.1.2) for DJ-1: Implications for Parkinson's Disease.

Mutations the in human DJ-1 (hDJ-1) gene are associated with early-onset autosomal recessive forms of Parkinson’s disease (PD). hDJ-1/parkinsonism associated deglycase (PARK7) is a cytoprotective multi-functional protein that contains a conserved cysteine-protease domain. Given that cysteine-proteases can act on both amide and ester substrates, we surmised that hDJ-1 possessed cysteine-mediated esterase activity. To test this hypothesis, hDJ-1 was overexpressed, purified and tested for activity towards 4-nitrophenyl acetate (pNPA) as µmol of pNPA hydrolyzed/min/mg·protein (U/mg protein). hDJ-1 showed maximum reaction velocity esterase activity (Vmax = 235.10 ± 12.00 U/mg protein), with a sigmoidal fit (S0.5 = 0.55 ± 0.040 mM) and apparent positive cooperativity (Hill coefficient of 2.05 ± 0.28). A PD-associated mutant of DJ-1 (M26I) lacked activity. Unlike its protease activity which is inactivated by reactive oxygen species (ROS), esterase activity of hDJ-1 is enhanced upon exposure to low concentrations of hydrogen peroxide (<10 µM) and plateaus at elevated concentrations (>100 µM) suggesting that its activity is resistant to oxidative stress. Esterase activity of DJ-1 requires oxidation of catalytic cysteines, as chemically protecting cysteines blocked its activity whereas an oxido-mimetic mutant of DJ-1 (C106D) exhibited robust esterase activity. Molecular docking studies suggest that C106 and L126 within its catalytic site interact with esterase substrates. Overall, our data show that hDJ-1 contains intrinsic redox-sensitive esterase activity that is abolished in a PD-associated mutant form of the hDJ-1 protein.