Supply Of Hydrogen Peroxide Research Articles

Directing the Oligomer Size Distribution of Peroxidase-Mediated Cross-Linked Bovine α-Lactalbumin

Enzymatic protein cross-linking is a powerful tool to change protein functionality. For optimal functionality in gel formation, the size of the cross-linked proteins needs to be controlled, prior to heating. In the current study, we addressed the optimization of the horseradish peroxidase-mediated cross-linking of calcium-depleted bovine alpha-lactalbumin. To characterize the formed products, the molecular weight distribution of the cross-linked protein was determined by size exclusion chromatography. At low ionic strength, more dimers of alpha-lactalbumin are formed than at high ionic strength, while the same conversion of monomers is observed. Similarly, at pH 5.9 more higher oligomers are formed than at pH 6.8. This is proposed to be caused by local changes in apo alpha-lactalbumin conformation as indicated by circular dichroism spectroscopy. A gradual supply of hydrogen peroxide improves the yield of cross-linked products and increases the proportion of higher oligomers. In conclusion, this study shows that the size distribution of peroxidase-mediated cross-linked alpha-lactalbumin can be directed toward the protein oligomers desired.

Photo or Solar Ferrioxalate Disinfection Technology without External Hydrogen Peroxide Supply

The Fenton reaction, which refers to the reaction between ferrous ions and hydrogen peroxide to produce the OH radical, has not been widely applied to the disinfection of microorganisms despite being economic and environmentally friendly. Cho et al. have previously proposed the neutral photo ferrioxalate system as a solution to the problems posed by the Fenton reaction in acidic conditions, 1) but this system still requires an external hydrogen peroxide supply. In the present study, we developed a simple disinfection technology using the photo or solar ferrioxalate reaction without the need for an external hydrogen peroxide supply. E. coli was employed as the indicating microorganism. The study results demonstrated the effectiveness of the photo ferrioxalate system in inactivating E. coli without any external hydrogen peroxide supply, as long as dissolved oxygen is supplied. Furthermore, the solar ferrioxalate system achieved faster inactivation of E. coli than an artificial light source at similar irradiance.

Advanced Fenton processing of aqueous phenol solutions: A continuous system study including sonication effects

Our previous report based on a batch reactor system for the Advanced Fenton Process (AFP) showed that pH, hydrogen peroxide and the organic substances treated are among the most important factors affecting the oxidation efficiency. As an extended study towards its potential commercialisation, this paper reports the effects of the main process parameters including those relating to a new laboratory scale AFP flow-through system. In order to systemise and correlate the results, the Taguchi experimental design method was used. Total organic carbon (TOC) removal was utilised as the measure of the oxidation efficiency and it was found that the removal of phenol from aqueous solution at pH 2.0 and 2.5 was very similar but hydrogen peroxide supply significantly affected the TOC removal with the change of flow rate from 14.4 ml/h to 60 ml/h. Also, the initial concentration of phenol was a highly significant factor, with higher concentrations resulting in a lower TOC removal rate. The temperature effects in the range of 14–42 °C were investigated and it was found that there was accelerated oxidation of phenol in the early stages but after 90 min there was no significant difference between the results. Sonication with a bath type sonicator resulted in relatively small enhancements of TOC removal but further studies with cup-horn sonication showed that TOC removal increased with higher intensity of sonication.

Structural and functional characterization of the two human ThOX/Duox genes and their 5′-flanking regions

A crucial step in thyroid hormone synthesis is the oxidative coupling of iodide to thyroglobulin that is catalyzed by thyroperoxidase. The limiting factor of this reaction is the supply of hydrogen peroxide. The generation of hydrogen peroxide has been linked to an enzymatic system located at the apical pole of thyrocytes. This enzymatic activity is assumed to be exerted by NADPH oxidases encoded by two recently cloned genes h ThOX1 and h ThOX2. Both genes are expressed at high levels in thyrocytes. In this study we report the chromosomal organization of these two genes and the functional characterization of their respective promoter regions. The two human ThOX genes are arranged in a head to head configuration and are separated by a 16 kb-long region. Human ThOX1 and ThOX2 genes span 75 kb and are composed of 35 and 34 exons, respectively. The promoters of both genes do not resemble each other and differ from promoters of other known thyroid-specific genes. No TATA box is present in either ThOX gene promoter. Functional studies confirm that both promoters display significant transcriptional activities after transfection in differentiated thyroid cell lines. However, in contrast to that of thyroglobulin or Na +/I − symporter gene promoter, hThOX promoter activity is not restricted to thyroid cells. Additionally, functional studies show that both hThOX promoters are not positively controlled by cAMP.

Efficiency of H 2O 2 and O 2 in supercritical water oxidation of 2,4-dichlorophenol and acetic acid

The efficiencies of hydrogen peroxide and oxygen as oxidants for the destruction of acetic acid and 2,4-dichlorophenol were compared under supercritical water conditions using a batch reactor system. The effects of temperature, water density, and oxidant concentration on the destruction of both compounds were studied. Diluted oxygen (21% O 2 and 79% N 2) and premixed hydrogen peroxide (32 % aqueous solution) were used as the oxidants. The reaction temperatures were 400, 450, and 500°C. Water densities were fixed at 0.15 g/mL and 0.35 g/mL. The destruction efficiency of hydrogen peroxide was significantly higher than that of oxygen. For acetic acid, the highest conversion of 97.7% was achieved with hydrogen peroxide at 500°C for a reaction time of 10 min. while 64.3% conversion was achieved with oxygen at the same temperature but for a reaction time of 30 min. For 2,4-dichlorophenol, conversions higher than 99.995% were obtained with hydrogen peroxide at 450°C for a reaction time of 2 min as compared to 87.6% conversion with oxygen at 500°C for the same reaction time. The change in supercritical water density from 0.15 g/mL to 0.35 g/mL at 400°C only slightly increased the conversion of both compounds. The conversion of acetic acid was enhanced by 10% at 450°C as hydrogen peroxide supply was increased from 100 to 200% of stoichiometric demand. However, concentration of hydrogen peroxide higher than 300% of stoichiometric demand did not yield higher conversions of acetic acid. The effect of excess oxygen was not conclusive.

Myeloperoxidase-mediated iodination in granulocytes.

The kinetics of the granulocyte iodination of phagocytized yeast cells was studied. The data obtained fitted an enzymatic reaction and the inhibition with specific antiserum indicated that the granulocyte iodination was mediated by the action of myeloperoxidase. Purified myeloperoxidase from the cytoplasmic granules of leukaemic myeloid cells was obtained by gel chromatography and ion exchange chromatography of the granule extract. Electrophoresis after treatment of the protein with dodecyl sulfate indicated a subunit structure. The myeloperoxidase formed spectrally characteristic complexes with hydrogen peroxide and also with iodide and it was shown to catalyze the iodination of yeast cells when a continous supply of hydrogen peroxide was formed by the addition of glucose oxidase. Since the myeloperoxidase mediated iodination of microorganisms in granulocytes is dependent on prior uptake of the microorganism, formation of the phagocytic vacuole, degranulation, hydrogen peroxide formation and finally oxidation of the iodide by the myeloperoxidase‐H2O2 complex it should be useful for detection of defects in the phagocytosis process.

Ground Handling and Launching Procedures for an Alcohol-Oxygen Rocket Missile

The problem of handling and launching a large liquidfueled missile is indeed complex. Some of the complexities of the problem are illustrated in this paper which treats the equipment and procedures used by the General Electric Co. in test programs involving several types of missiles using turbo-pumped feed systems. In the program described, missiles were shipped in reusable steel shipping containers with the missile suspended inside by an arrangement of rubber shear mounts. Assembly equipment included a lifting beam and several adjustable dollies. For field transportation and erection, a modified German Meillerwagon was used. The launching stand was a tubular steel framework on which a turntable for azimuth adjustment was mounted. The missile was supported on the turntable by four support arms which retracted at take-off. Electrical connections and gas, water, and liquid oxygen disconnects to the missile were supported from a ring on the turntable. Servicing equipment included a movable access platform, an alcohol supply truck, remotely controlled oxygen supply and gas pressurizing supply systems, and a hydrogen peroxide supply system. The use of this equipment is described in a typical cycle which follows a missile from the factory through the field test, assembly, erection, preparation, and launching.