Programmed cell death (PCD) is a universal event experienced by all eukaryotes and is an essential process for the maintenance of regular homeostasis. The careful regulation of PCD pathways is beneficial to all organisms and a better understanding of various PCD components and their interactions may enhance overall quality of life and increase longevity of defective organisms. Since a boom of interest was shown towards the study of PCD approximately thirty years prior, a comprehensive understanding of the underlying mechanisms of apoptosis currently exists. Many of the key features involved in PCD have been shown to be conserved across the animal and plant kingdoms and although the overall process of cell death appears to occur in a similar manner in both plants and animals, subtle variations have been identified between these two kingdoms regarding various mechanisms of apoptosis. The major component of cell death in plants and animals appears to be the mitochondria where most of the PCD points of control converge. Heat shock proteins (Hsps) play a vital role in the regulation of PCD and act at an array of points along the PCD pathway. One of the crucial events of PCD is the release of cytochrome c from the mitochondria which proceeds to activate the protease cascade. Hsp70 has been shown to attenuate apoptosis by specifically preventing cytochrome c release into the cytosol of animal cells. A similar correlation between increases of Hsp70 and decreased PCD has been identified in plants, the mechanism of which remains unclear. The objective of this study was to investigate the interaction between increased Hsp70 accumulation and decreased PCD, as indicated by reduced cytochrome c translocation and DNA laddering. The major observations of this study proceeded to show that an increased expression of Hsp70, induced by a mild heat shock, was able to protect tobacco cells against H2O2-mediated cell death. This protection appeared to commence at a mitochondrial level as cytochrome c translocation was clearly inhibited and was confirmed by the absence of downstream DNA laddering. The major findings obtained from this study provided a clearer picture of the mechanisms surrounding the cytoprotective properties of thermotolerant cells, the implications of which are beneficial to post harvest industries, as the ability to postpone PCD provides an advantage enables prolonged shelf lives of various crops. / Dr. Marianne J. Cronjé

>Magister Scientiae - MSc / Drought stress is a major contributor to reduced soybean crop yield and quality, this can however be mitigated by the plant’s antioxidant defence mechanisms. One group of antioxidant enzymes that are active in these defence mechanisms are glutathione peroxidases (GPXs). GPXs are antioxidant proteins which are able to reduce H2O2, a toxic reactive oxygen species which accumulates under stress conditions. This study aims at isolating the protein encoded by Glyma01g42840 and determining if it has Phospholipid hydroperoxidase glutathione peroxidase (PHGPX) and/or Thioredoxin dependent peroxidase (TRX-PX) activity as well as assaying the effect of Drought stress on the expression of this putative GPX . This will be accomplished by molecular cloning, sequencing as well as the expression of the isolated protein to assay it enzymatic activity. It was found that the enzyme encoded by Glyma01g42840 is able to use glutathione and thioredoxin as electron donors for the detoxification peroxides, however enzymatic activity is more efficient when using glutathione as an electron donor. In conclusion it was found that glyma01g42840 encodes an enzyme which is able to utilise more than one electron donor and as glutathione produces the greatest amount of enzymatic activity it can be said that glyma01g42840 encodes a GPX.

Orientador: Elisa Maria Aparecida Giro / Resumo: O peróxido de hidrogênio (H2O2) é considerado uma das principais fontes endógenas de estresse oxidativo para bactérias orais. Contudo, o seu papel no processo de desenvolvimento da cárie dentária ainda não está completamente elucidado. O objetivo deste estudo in vitro foi gerar uma cepa de Streptococcus mutans tolerante ao H2O2, e avaliar a habilidade do H2O2 em afetar a formação e a virulência de biofilmes de S. mutans. Para gerar a cepa tolerante ao H2O2, a cepa de S. mutans UA159, foi reativada em placas de agar BHI e incubadas (48 horas, a 37°C e 5% de CO2). Duas a cinco colônias foram transferidas para tubos falcon contendo 2 mL de caldo BHI suplementado com 1% de glicose e incubadas por 18 horas, sob as mesmas condições. As culturas foram diluídas 1:20 em meio de cultura fresco, incubadas até atingirem a fase exponencial de crescimento, centrifugadas, lavadas, ressuspensas em glicina, e submetidas a tratamento com 80 mM de H2O2. Esses procedimentos foram repetidos por oito vezes, e as colônias sobreviventes foram consideradas tolerantes. Em seguida, para o crescimento do biofilme, foi usado um modelo de aderência ativa. Lamínulas de vidro estéreis, jateadas com óxido de alumínio, foram imersas em saliva filtrada para a formação da película adquirida. Posteriormente, foram imersas verticalmente em 2,8 mL de caldo BHI com 1% de sacarose (n=12 por grupo) inoculado com 106 UFC/mL da cepa controle (grupo GC) ou da cepa tolerante ao H2O2. Para a cepa tolerante ao H2O2, em um ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Hydrogen peroxide (H2O2) is one of the main endogenous sources of oxidative stress for oral bacteria. However, its role in the dental caries development has not been fully elucidated. The objective of this in vitro study was to generate a strain of S. mutans tolerant to H2O2, and to evaluate the ability of H2O2 to affect the biofilm formation and virulence of S. mutans. To generate the H2O2 tolerant strain, S. mutans UA159 was reactivated on BHI agar plates, and incubated (48 hours at 37 oC and 5% CO2). Two to five colonies of the microorganism were transferred to falcon tubes containing 2 mL of BHI broth supplemented with 0.8% glucose and incubated under the same conditions for 18 hours. The culture was diluted 1:20 in fresh culture medium, incubated again until reaching the mind-log growth phase, centrifuged, washed, suspended in glycine, and treated with 80 mM H2O2. These procedures were repeated for eight times, and then the surviving colonies were considered tolerant. Next, the biofilm were grown on glass slides using an active adherence model. First, sterile glass slides, sandblasted with aluminum oxide, were immersed in filtered saliva to form the acquired pellicle. After that, the slides were immersed vertically in 2.8 mL of BHI broth with 1% sucrose (n = 12 per group) and inoculated with 106 CFU/mL of the control strain (GC Group) or H2O2 tolerant strain. For the H2O2 tolerant strain, in a group (GTcPH group) 80 mM H2O2 were added in the culture medium and in the oth... (Complete abstract click electronic access below) / Mestre

Magister Scientiae Dentium - MSc(Dent) / Aim and Objectives: To assess the effect of bleaching on the marginal integrity of Class V composite resin restorations. To determine the effect of a 6% hydrogen peroxide over the counter and a 38% hydrogen peroxide in-office vital bleaching treatment products on the microleakage of Class V composite restorations. / South Africa

Do competitivo mercado de produção de açúcar demanda-se um produto detentor de maior qualidade e menor custo. A qualidade do açúcar relaciona-se com o estudo das propriedades físico-químicas da sacarose durante o processo de clarificação. Na produção de açúcar branco utiliza-se o dióxido de enxofre em operação unitária de clarificação. No entanto, o uso desse reagente encontra restrições na indústria alimentícia e nos sistemas agroindustriais, em consequência de suas emissões na atmosfera, assim como, de reações alergênicas possivelmente relacionadas à exposição de resíduos de dióxido de enxofre em alimentos, em indivíduos sensíveis. Tecnologias alternativas, como o uso de peróxido de hidrogênio e de ozônio têm sido propostas. Do uso do peróxido de hidrogênio, de acordo com a literatura consultada, tem-se a diminuição de viscosidade, em conjunto com o aumento de pureza do xarope, pela remoção de compostos não açúcares. Dessa forma, o peróxido de hidrogênio é um eficiente agente oxidante de moléculas produtoras de cor, levando-as a parcial ou total degradação, com destruição permanente de substâncias corantes. A aplicação de peróxido de hidrogênio, no tratamento do caldo de cana-de-açúcar, foi considerada, no presente estudo, em três cenários distintos - com peróxido de hidrogênio na proporção 0,6 gH2O2/kgcaldo, na proporção de 1 gH2O2/kgcaldo e na proporção de 5 gH2O2/kgcaldo em substituição ao dióxido de enxofre - utilizado em método corrente, nas usinas. O escopo deste estudo, pois, constitui a análise de viabilidade econômico-financeira do peróxido de hidrogênio como agente de redução de cor de caldo, em operação unitária de clarificação, em substituição total ao uso de dióxido de enxofre. De fato, foram considerados os valores de investimento da proposta com uso de peróxido de hidrogênio em relação à estrutura padrão, com os insumos relativos a cada situação, pois a adequação da etapa de clarificação pode ser utilizada em lugar da implantação de uma nova unidade produtiva. Os valores encontrados para a clarificação de açúcar, com uso de peróxido de hidrogênio em substituição à sulfitação, considerando a descrição operacional com ganhos técnicos e insumos necessários, foram maiores, pois o investimento imobilizado em equipamentos foi maior, assim como o preço dos insumos. Das situações consideradas, houve aumento de R$ 0,16/saca50kg açúcar, em relação ao peróxido de hidrogênio utilizado em proporção 0,6 gH2O2/kgcaldo; de R$ 0,30 /saca50kg açúcar, em relação ao peroxido de hidrogênio na proporção de 1 gH2O2/kgcaldo e R$ 1,66 / saca50kg açúcar, em relação ao peroxido de hidrogênio na proporção de 5 gH2O2/kgcaldo. Percebe-se, dessa forma, a possibilidade de substituição do reagente majoritariamente utilizado, pelo proposto; considerando, ainda, a parceria entre setores privado e público, em consequência de demanda da sociedade por produtos alimentícios isentos de resíduos de enxofre, e do repasse de custos não demasiadamente oneroso para as usinas açucareiras. Todavia, fatores outros, concernentes à qualidade do produto final, como a tendência de degradação de sacarose, as questões ambientais e de saúde pública, assim como os ganhos energéticos devem ser analisados. / The competitive market of sugar production demands a better product with higher quality and lower cost. Sugar quality involves the physical-chemical properties of sucrose during the clarifying process. In white sugar production, sulfur dioxide is used in the clarifying process. However, this reagent has restrictions in food industry and agribusiness systems due to, sulfur dioxide emissions to the atmosphere, as well as its potentially allergenic reactions, concerning exposure to sulfur dioxide residues in foods, in sensitive individuals. Alternative technologies, using hydrogen peroxide and ozone have been proposed. The use of hydrogen peroxide, according to literature, promotes viscosity reduction and syrup purity increase, through the removal of non-sugar compounds. Therefore, hydrogen peroxide is a powerful oxidizing agent that causes partial or total color molecules degradation, causing permanent destruction. The application of hydrogen peroxide, in sugarcane juice, considered in this study has three distinct situations: 0.6 gH2O2/kgsugarcane juice proportion, 1 gH2O2/kgsugarcane juice proportion and 5 gH2O2/kgsugarcane juice proportion, replacing sulfur dioxide - used in the current method. This study scope is the economic viability of hydrogen peroxide, replacing sulfur dioxide in clarifying operation. The investment values using hydrogen peroxide in relation to standard structure were considered rather than the implementation of a new production unit. The hydrogen peroxide values, in clarifying process were higher, considering operational description by technical profits and necessary inputs, because the investment in equipment and input prices were higher. There was an increase of R$ 0.16 bag 50kg sugar using 0.6 gH2O2/kgsyrup; R$ 0.30 /bag 50kg sugar when the proportion was 1 gH2O2/kgsyrup and R$ 1.66/ bag 50kg sugar when the proportion was 5 gH2O2/kgsyrup. Therefore, there is a great possibility of replacing the main reagent used as alternative, including the partnership between private and public sectors the society demands for food products free of sulfur residue presenting production costs less expensive for the sugar industry. However, other factors, related to final product quality, such as sucrose degradation tendency, environmental and public health issues, as well as the energy gains should be analized.

Neste estudo apresenta-se a síntese de duas amostras de nanopartículas de ferrita de níquel, denominadas C-NiFe2O4 e NiFe2O4, através de um método simples, de baixo custo e ambientalmente amigável. Estudos morfológicos, estruturais, eletrônicos, ópticos e magnéticos foram realizados com o intuito de caracterizar as propriedades desses materiais para que possibilitassem, além de maior grau de conhecimento, sua aplicação como sensores colorimétricos para detecção de ácido ascórbico e peróxido de hidrogênio. Mediante a análise térmica dos precursores, foi possível determinar os intervalos de temperatura de decomposição, assim como a temperatura ótima de formação das nanopartículas. A amostra NiFe2O4 é ferromagnética e corresponde a uma fase cúbica de espinélio inverso. Os dados de difração de raios X, espectroscopia Mössbauer e o modelo iônico sugerem a presença de um certo grau de substituição, possuindo em sua estrutura um cátion divalente como agente dopante. As nanopartículas de C-NiFe2O4 foram utilizadas como catalisador na oxidação do 3,3',5,5'-tetrametilbenzidina (TMB) em meio ácido para formar uma solução azul sem adição de outro reagente. Como resultado foi utilizado como sensor colorimétrico para detecção de ácido ascórbico, visto que este reduz o complexo de transferência de carga, TMBOX, novamente para TMB. A calibração analítica apresentou uma faixa linear entre 1-20 μM para a concentração de ácido ascórbico, com limite de detecção (3/m) de 0,93 μM. A determinação em suplementos de vitamina C através do método de adição de padrão mostrou a eficiência do sensor para detectar ácido ascórbico em amostras reais. Já a amostra de NiFe2O4 demonstrou atividade catalítica semelhante as peroxidases naturais, oxidando o TMB na presença de H2O2 para formar TMBOX, que dá coloração azul a solução. Dessa forma, NiFe2O4 foi utilizado em um sensor colorimétrico para detecção de H2O2 e a calibração analítica revelou duas faixas lineares, uma entre 2,28 - 28,60 μM e a outra entre 28,60 μM - 114,20 μM. O limite de detecção (3/m) foi de 1,94 μM. Ambos os métodos apresentaram boa repetibilidade, com coeficiente de variação de 3,5% e 4% respectivamente. / This study presents the synthesis of two samples of nickel ferrite nanoparticles, termed C-NiFe2O4 and NiFe2O4, through a simple, low cost and environmentally friendly method. Morphological, structural, electronic, optical and magnetic studies were carried out with the aim of characterizing the properties of these materials, which allowed the application of colorimetric sensors for the detection of ascorbic acid and hydrogen peroxide. Through the thermal analysis of the precursors, it was possible to determine the decomposition temperature ranges, as well as the optimum temperature of formation of the nanoparticles. The sample NiFe2O4 is ferromagnetic and corresponds to a cubic phase of inverse spinel. The X-ray diffraction data, Mössbauer spectroscopy and the ionic model suggest the presence of a certain degree of substitution, having in its structure a divalent cation as a doping agent. The C-NiFe2O4 nanoparticles were used as catalysts in the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in acidic medium to form a blue solution without addition of another reagent. As a result, it was used as a colorimetric sensor for the detection of ascorbic acid, as it reduces the charge transfer complex, TMBOX, again to TMB. The analytical calibration showed a linear range between 1-20 μM for the concentration of ascorbic acid, with a detection limit (3 /m) of 0.93 μM. The determination of vitamin C supplements using the standard addition method showed the efficiency of the sensor to detect ascorbic acid in actual samples. Already NiFe2O4 sample demonstrated catalytic activity similar to natural peroxidases, oxidizing the TMB in the presence of H2O2 to form TMBOX, which gives blue coloration to the solution. Thus, NiFe2O4 was used in a colorimetric sensor to detect H2O2, and the analytical calibration revealed two linear ranges, one between 2.28 - 28.60 μM and the other between 28.60 μM - 114.20 μM. The detection limit (3 /m) was 1.94 μM. Both methods presented good repeatability, with a coefficient of variation of 3.5% and 4% respectively.

Objectives: To compare two in-office bleaching methods with respect to tooth color change and level of hydrogen peroxide penetration into the pulp cavity, and evaluate relationships between penetration level and color change. Methods: 80 extracted canines were sectioned above the CEJ and pulp tissue removed. Tooth thickness was measured from the outer labial surface to the outer boundary of the pulp cavity at the cross-sectioned root 3mm below the CEJ using a digital caliper. Baseline color was measured spectrophotometrically; acetate buffer was added into the cavity. Teeth were mounted and exposed to two different bleaching regimens (conventional versus sealed bleaching technique). After exposure to 38% hydrogen peroxide gel for one hour, buffer was removed from the cavity and placed into a volumetric flask. Hydrogen peroxide amount was estimated spectrophotometrically using leucocrystal violet and horseradish peroxidase. Specimen color was re-measured 2 hours post-bleaching. Color change was measured per Commission Internationale de l'Eclairage methodology. Linear regression was used to evaluate factors affecting color change, including bleaching technique. Results: The conventional and sealed bleaching groups showed no difference at baseline with respect to tooth thickness or any of the L*a*b color measures (p>0.51); however there was significantly greater hydrogen peroxide penetration in the conventional bleaching group (p<0.0001). Linear modeling of the change in lightness (ΔL) showed that the increase in lightness tended to be greater for teeth with lower initial L* values (r=-0.32, p=0.004). After adjustment for initial L*, there was no evidence that ΔL differed with hydrogen penetration levels (p=0.53) or bleaching technique (mean group difference in ΔL= 0.36; p=0.27). Conclusion: Both groups showed significant increases in lightness exceeding 2 units and therefore discernible to the naked eye (p<0.0001); however, mean ΔL did not differ significantly with bleaching method or hydrogen peroxide penetration.

M. Tech (Department of Chemistry, Faculty of Applied and Computer Sciences) Vaal University of Technology. / Agricultural waste such as Macadamia nutshells are currently receiving more attention for removal of hexavalent chromium (Cr(VI)). However, they have low adsorption capabilities when used in their raw form. In this study, the efficiency of using Macadamia nutshell powder modified with different concentrations of hydrogen peroxide, grafted with 1,5’-diphenylcarbizide (DPC) for the removal of hexavalent chromium from aqueous solution was explored. The effects of various parameters controlling adsorption of Cr(VI) onto Macadamia adsorbents such as initial concentration, contact time, adsorbent concentration and pH were investigated. The optimal operating parameters for Macadamia nutshells treated with hydrogen peroxide (MHP) adsorbents were determined to be 75 mg/L, 3 h, 0.1 g and pH 1. The optimal operating parameters for Macadamia nutshells treated with hydrogen peroxide and grafted with 1,5’-diphenylcarbizide (MHPD) were determined to be 150 mg/L, 1 h, 0.1 g and pH 3. Fourier transform infrared (FTIR) spectroscopy of the adsorbents revealed that treated MHP showed amino groups attached to the adsorbents. Thermogravimetric analysis (TGA) revealed that the grafted material lowered the thermal stability from 180◦C to 300◦C due to volatile nature of DPC. The surface of the MHPD materials was rough due to grafting. The results showed that the 1,5’-diphenylcarbazide treatment improved the removal efficiency of Cr(VI).

Content: The utilization of mink waste generated through the industrial process attracted both industry and academia interests. In this study, the use of hydrogen peroxide as an oxidizing agent onto collagen producing self-crosslinking which extracting from mink solid waste was studied by infrared spectrum, fluorescence spectrum and thermal properties. The effect of hydrogen peroxide dosage and reaction temperature on the degree of oxidative self-crosslinking of collagen was analyzed by the changes of molecular structure and thermal stability. It was found that, hydroxide groups on the collagen side-chains can be oxidized to aldehyde groups and carboxyl groups by hydrogen peroxide in alkaline environment. These oxidized groups can crosslink with functional groups on collagen by covalent bond and ionic bond, changing collagen molecular structure and improving thermal stability. When the dosage of hydrogen peroxide was 14.74% and reaction temperature was 40℃ ±, the oxidative self-crosslinking of collagen was the strongest. This study provided theoretical basis for the high-value utilization of mink wastes. Take-Away: 1. The oxidative self-crosslink of collagen extracted mink solid waste was studied. 2. Hydrogen peroxide was applied as environment friendly oxidant. 3. The change of functional groups and degree of crosslinks during the oxidation was studied via infrared, fluorescence spectrum and differential scanning calorimetry.

This thesis is focused on so-called diaphragm discharge, which is one kind of electric discharges in liquid, which belongs among so-called AOP´s techniques, still more used for water cleaning in the present. One of effectiveness and stability indicators of diaphragm discharge is generation of hydrogen peroxide. In theoretical part, detail principle description of electric discharge in liquid is situated. Further, properties of electrolyte are introduced and general spectrophotometric method of obtained sample determination is described. In experimental part, a full procedure of experiment is introduced. Next part containing results and discussions introduces particular results of individual measurements and their reasons. Final chapter is the end, which forms total summary and evaluation of all results. By the application of all chosen electrolytes in solution at diaphragm discharge formation of hydrogen peroxide has appeared. Inorganic and organic electrolytes were used. As inorganic electrolytes following salts were selected – solutions of halogenides, next sodium nitrate as a representative of nitrates, potassium dihydrogenphosphate as a representative of phosphates, etc. Representative of organic electrolytes was citric acid. The value of initial conductivity of electrolytes had the main influence on hydrogen peroxide formation. Electrolytes potassium dihydrogenphosphate and sodium sulphate the great influence on effectiveness and stability of the diaphragm discharge. Their rate constants reached maximum value by the application of solution with initial conductivity of approximately 400 mikrosiemens, particularly 0.0492 mmol/l.min and 0.048 mmol/l.min. On the contrary, low values of rate constant were achieved in electrolyte ammonium chloride at around the same initial conductivity – 0.0269 mmol/l.min. During experiments stainless steel and platinum electrodes were used. It was found that kind of electrode material hadn’t influence on generation of hydrogen peroxide. Hydrogen peroxide was formed only in the cathode space.