Lichen metabolites modulate hydrogen peroxide and nitric oxide in mouse macrophages

The activities of perlatolic acid (1), atranorin (2), and lecanoric acid (3) and their derivatives, such as orsellinates and β-methyl orsellinates obtained by alcoholysis, were assessed for stimulation of the release of hydrogen peroxide and nitric oxide in cultures of peritoneal macrophage cells from mice. The hydrogen peroxide production was estimated by oxidation of phenol red, while the Griess reagent was used to determine the nitric oxide production. 1 and 4-methoxy-ethyl orsellinate (XVII) were the compounds that induced the greatest release of H 2O 2, whereas n-pentyl orsellinate (IV), iso-propyl orsellinate (V), sec-butyl orsellinate (VI), and XVII induced a small release of NO. These results indicate that lichen products and their derivatives have potential immune-modulating activities. © 2009 Verlag der Zeitschrift für Naturforschung, Tübingen.

Indirect cytotoxicity of a 35% hydrogen peroxide bleaching gel on cultured odontoblast-like cells

The aim of this study was to evaluate the trans-enamel and trans-dentinal effects of a 35% hydrogen peroxide (H2O2) bleaching gel on odontoblast-like cells. Enamel/dentin discs obtained from bovine incisors were mounted in artificial pulp chambers (APCs). Three groups were formed: G1- 35% H2O2; G2- 35% H2O2 + halogen light application; G3- control. The treatments were repeated 5 times and the APCs were incubated for 12 h. Then, the extract was collected and applied for 24 h on the cells. Cell metabolism, total protein dosage and cell morphology were evaluated. Cell metabolism decreased by 62.09% and 61.83% in G1 and G2, respectively. The depression of cell metabolism was statistically significant when G1 and G2 were compared to G3. Total protein dosage decreased by 93.13% and 91.80% in G1 and G2, respectively. The cells in G1 and G2 exhibited significant morphological alterations after contact with the extracts. Regardless of halogen light application, the extracts caused significantly more intense cytopathic effects compared to the control group. After 5 consecutive applications of a 35% H2O2 bleaching agent, either catalyzed or not by halogen light, products of gel degradation were capable to diffuse through enamel and dentin causing toxic effects to the cells.

An in vitro thermal analysis during different light-activated hydrogen peroxide bleaching

This study measured the critical temperature reaching time and also the variation of temperature in the surface of the cervical region and within the pulp chamber of human teeth submitted to dental bleaching using 35% hydrogen peroxide gel activated by three different light sources. The samples were randomly divided into 3 groups (n = 15), according to the catalyst light source: Halogen Light (HL), High Intensity Diode Laser (DL), and Light Emmited Diode (LED). The results of temperature variation were submitted to the analysis of variance and Tukey test with p < 0.05. The temperature increase (mean value and standard deviation) inside the pulp chamber for the HL group was 6.8 ± 2.8°C; for the DL group was 15.3 ± 8.8°C; and for the LED group was 1.9 ± 1.0°C for. The temperature variation (mean value and standard deviation) on the tooth surface, for the group irradiated with HL was 9.1 ± 2.2°C; for the group irradiated with DL were 25.7 ± 18.9°C; and for the group irradiated with LED were 2.6 ± 1.4°C. The mean temperature increase values were significantly higher for the group irradiated with DL when compared with groups irradiated with HL and LED (p < 0.05). When applying the inferior limits of the interval of confidence of 95%, an application time of 38.7 s was found for HL group, and 4.4 s for DL group. The LED group did not achieve the critical temperatures for pulp or the periodontal, even when irradiated for 360 s. The HL and DL light sources may be used for dental bleaching for a short period of time. The LED source did not heat the target tissues significantly within the parameters used in this study. © 2010 Pleiades Publishing, Ltd.

Effect of photochemical activation of hydrogen peroxide bleaching gel with and without TiO2 and different wavelengths

Aim: To evaluate the effect of photochemical activation of hydrogen peroxide (H2O2) bleaching gel with different wavelengths. Methods: In the study, 80 bovine incisors were used, which were stained in 25% soluble coffee and divided in 4 groups. The initial color was measured with the Easy Shade spectrophotometer by CIE Lab. An experimental 35% H2O2 bleaching gel was used, either with or without the presence of titanium dioxide (TiO2) pigment, associated with two light sources: G1 - Transparent Gel (TG) and no activation; G2 - Gel with TiO2 and activation with blue LED (l=470nm)\laser (Easy Bleach) appliance; G3 - Gel with TiO2 and activation with ultraviolet (l=345nm - UV); G4 - TG and activation with UV. Three applications of the gels were made for 10 min, and in each, 3 activations of 3 min, with interval of 30 s between them. The coloration was evaluated again and the variation in color perception (DE) was calculated. The data were submitted to one-way ANOVA and Tukey's test at 5% significance level. Results: There were significant differences between G1 and G4. The greatest E value was observed in G4 (13.37). There was no statistically significant difference (p>0.05) between the groups 2, 3 and 4. Conclusions: The presence of TiO2 particules in the bleaching gel did not interfere at the bleaching results.

Analysis of agonist and antagonist effects on thyroid hormone receptor conformation by hydrogen/deuterium exchange

Thyroid hormone receptors (TRs) are ligand-gated transcription factors with critical roles in development and metabolism. Although x-ray structures of TR ligand-binding domains (LBDs) with agonists are available, comparable structures without ligand (apo-TR) or with antagonists are not. It remains important to understand apo-LBD conformation and the way that it rearranges with ligands to develop better TR pharmaceuticals. In this study, we conducted hydrogen/deuterium exchange on TR LBDs with or without agonist (T 3) or antagonist (NH3). Both ligands reduce deuterium incorporation into LBD amide hydrogens, implying tighter overall folding of the domain. As predicted, mass spectroscopic analysis of individual proteolytic peptides after hydrogen/ deuterium exchange reveals that ligand increases the degree of solvent protection of regions close to the buried ligand-binding pocket. However, there is also extensive ligand protection of other regions, including the dimer surface at H10-H11, providing evidence for allosteric communication between the ligand-binding pocket and distant interaction surfaces. Surprisingly, Cterminal activation helix H12, which is known to alter position with ligand, remains relatively protected from solvent in all conditions suggesting that it is packed against the LBD irrespective of the presence or type of ligand. T 3, but not NH3, increases accessibility of the upper part of H3-H5 to solvent, and we propose that TR H12 interacts with this region in apo-TR and that this interaction is blocked by T 3 but not NH3.Wepresent data from site-directed mutagenesis experiments and molecular dynamics simulations that lend support to this structural model of apo-TR and its ligand-dependent conformational changes. (Molecular Endocrinology 25: 15-31, 2011). Copyright © 2011 by The Endocrine Society.

Anaerobic effluent disinfected with ozone/hydrogen peroxide efluente anaeróbio desinfetado com ozônio/peróxido de hidrogênio

This research aimed at studying the oxidation process, to verify the effectiveness of coliform inactivation and to evaluate the formation of ozonation disinfection byproducts (DBP) in anoxic sanitary wastewater treated with ozone/hydrogen peroxide applied at doses of 2.6 mg O3 L-1 and 2.0 mg H2O2 L-1 with contact time of 10 min and 8.1 mg O3 L-1 and 8.0 mg H2O2 L-1 with contact time of 20 min. The mean chemical oxygen demand (COD) reductions were 7.50 and 9.40% for applied dosages of 2.5-2.8 and 6.4-9.4 mg O3 L-1 + 2.0 and 8.0 mg H2O2.L-1, respectively. The Escherichia coli (E. coli) inactivation range was 2.98-4.04 log10 and the total coliform inactivation range was 2.77-4.01 log10. The aldehydes investigated were formaldehyde, acetaldehyde, glyoxal and methylglyoxal. It was observed only the formation of acetaldehyde that ranged 5.53 to 29.68 μg L-1.

Antioxidant enzyme activity and hydrogen peroxide content during the drying of Arabica coffee beans

The development of the germination process and drought stress during the drying of coffee can generate reactive oxygen species, which can be neutralized by way of antioxidant mechanisms. No studies related to antioxidant enzymes during the drying of coffee were found in the literature, and considering their importance, the enzymatic activities of superoxide dismutase (SOD), guaiacol peroxidase (GPOX) and glutathione reductase (GR), and also the hydrogen peroxide content were evaluated during the drying of two types of coffee bean, one processed as natural coffee and the other as pulped natural coffee. The results showed a reduction in the SOD, GPOX and GR enzymatic activities of the natural coffee as compared to the pulped natural coffee during the drying period. Moreover, the hydrogen peroxide content of the natural coffee was greater than that of the pulped natural coffee. These results suggest the development of oxidative stress during the coffee drying process, controlled more efficiently in pulped natural coffee by the early action of GPOX during the drying process. Nevertheless, differential responses by SOD isoenzymes and possibly the role of other peroxidases also appear to be involved in the responses observed. © 2013 Springer-Verlag Berlin Heidelberg.

Hydrogen oxidation on ordered intermetallic phases of platinum and tin - A combined experimental and theoretical study

Hydrogen oxidation on the surfaces of the intermetallic compounds Pt 3Sn, PtSn and PtSn2 has been studied by the rotating disc electrode technique. Pt3Sn and PtSn were found to be good catalysts, about as good as Pt, while PtSn2 was inactive over the investigated range of potentials. Underpotential deposition of hydrogen is observed only on Pt3Sn. These results are explained by theoretical calculations based on a theory developed within our own group, and by density functional theory. © 2012 Elsevier B.V.

Toward pH-controllable bioelectrocatalysis for hydrogen peroxide based on polymer brushes

In the present work, a biosensor was built with smart material based on polymer brushes. The biosensor demonstrated a pH-sensitive on-off property, and it was further used to control or modulate the electrochemical responses of the biosensor. This property could be used to realize pH-controlled electrochemical reaction of hydrogen peroxide and HRP immobilized on polymer brushes. The composite film also showed excellent amperometric i-t response toward hydrogen peroxide in the concentration range of 0-13 μM. In future, this platform might be used for self-regulating targeted diagnostic, drug delivery and biofuel cell based on controllable bioelectrocatalysis. © 2013 Elsevier B.V.

Hydrogen bonding donation of N-methylformamide with dimethylsulfoxide and water

20% N-methylformamide (NMF) mixtures with water and with dimethylsulfoxide (DMSO) have been studied. A comparison between the hydrogen bonding (H-bond) donation of N-methylformamide with both solvents in the mixtures is presented. Results of radial distribution functions, pair distribution energies, molecular dipole moment correlation, and geometry of the H-bonded species in each case are shown. The results indicate that the NMF-solvent H-bond is significantly stronger with DMSO than with water. The solvation shell is best organized in the DMSO mixture than in the aqueous one. © 2013 Elsevier B.V. All rights reserved.

Hydrogen production by biogas steam reforming: A technical, economic and ecological analysis

Fuel cells are electrochemical energy conversion devices that convert fuel and oxidant electrochemically into electrical energy, water and heat. Compared to traditional electricity generation technologies that use combustion processes to convert fuel into heat, and then into mechanical energy, fuel cells convert the hydrogen and oxygen chemical energy into electrical energy, without intermediate conversion processes, and with higher efficiency. In order to make the fuel cells an achievable and useful technology, it is firstly necessary to develop an economic and efficient way for hydrogen production. Molecular hydrogen is always found combined with other chemical compounds in nature, so it must be isolated. In this paper, the technical, economical and ecological aspects of hydrogen production by biogas steam reforming are presented. The economic feasibility calculation was performed to evaluate how interesting the process is by analyzing the investment, operation and maintenance costs of the biogas steam reformer and the hydrogen production cost achieved the value of 0.27 US$/kWh with a payback period of 8 years. An ecological efficiency of 94.95%, which is a good ecological value, was obtained. The results obtained by these analyses showed that this type of hydrogen production is an environmentally attractive route. © 2013 Elsevier Ltd.

Photoelectrochemical Hydrogen Generation and Concomitant Organic Dye Oxidation under TiO2 Nanotube

The present work describes the photoelectrochemical hydrogen generation during a photodegradation of an organic compound. For this, it was chosen the reactive black 5 dye as a model of organic pollutant and its oxidation under TiO2 nanotube in a two compartment cell. The photoelectrocatalysis is conducted in 0.1 mol L-1 Na2SO4 pH 6 medium under photoanode biased at +1.0 V (SCE) and activated by UV and visible light using 150W Xe-Arc lamp (Oriel) and 125 W Hg lamp (Osram). The concomitant hydrogen production was monitored at cathodic compartment using a Pt cathode. Using optimized condition of Na2SO4 0.1 mol L-1 pH 6 as supporting electrolyte, applied potential of +1.0V it was verified 100% of discoloration and 72% of TOC removal of 1.0 x 10(-5) mol L-1 Reactive Black 5 dye after 120 min of treatment (rate constant of 10.6 x10(-2) min(-1)). The concomitant hydrogen generation was 44% in this condition.

Transenamel and Transdentinal Penetration of Hydrogen Peroxide Applied to Cracked or Microabrasioned Enamel

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Some properties of intermetallic compounds of Sn with noble metals relevant for hydrogen electrocatalysis

Using density functional theory and a model developed in our own group, we have investigated the suitability of three intermetallic compounds - AuSn, PdSn, and PtSn - as electrode materials for hydrogen oxidation in fuel cells, focusing on their CO tolerance and their catalytic properties. All three metals were found to have lower susceptibility to be poisoned by CO compared to platinum, but only PtSn promises to be a good catalyst for hydrogen oxidation. (C) 2013 Elsevier Ltd. All rights reserved.