• Molecules and Cells
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• v.22 no.2
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• pp.220-227
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• 2006

Oxidative alteration of mitochondrial cytochrome c has been linked to disease and is one of the causes of proapoptotic events. We have investigated the modification of cytochrome c by $H_2O_2$. When cytochrome c was incubated with $H_2O_2$, oligomerization of the protein increased and the formation of carbonyl derivatives and dityrosine was stimulated. Radical scavengers prevented these effects suggesting that free radicals are implicated in the $H_2O_2$-mediated oligomerization. Oligomerization was significantly inhibited by the iron chelator, deferoxamine. During incubation of deoxyribose with cytochrome c and $H_2O_2$, damage to the deoxyribose occurred in parallel with the release of iron from cytochrome c. When cytochrome c that had been exposed to $H_2O_2$ was analyzed by amino acid analysis, the tyrosine, histidine and methionine residues proved to be particularly sensitive. These results suggest that $H_2O_2$-mediated cytochrome c oligomerization is due to oxidative damage resulting from free radicals generated by a combination of the peroxidase activity of cytochrome c and the Fenton reaction of free iron released from the oxidatively-damaged protein.

• Proceedings of the Korean Society of Food Hygiene and Safety Conference
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• 2002.05a
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• pp.138-138
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• 2002

Oxidative stress has been associated with a number of diseases in human. Among the sources that can generate oxidative stress, it has been reported that iron can generate reactive oxygen species (ROS)with thiol. In iron overload state, increased thiol levels in plasma appeared to be associated with human mortality. In this study we examined whether iron could interact with thiols in plasma, generating ROS. In human plasma, unlike with Fe(III), Fe(II) increased lucigenin-enhanced chemiluminescence in concentration-dependent manner, and this was inhibited by SOD. Boiling of plasma did not affect chemiluminescence induced by Fe(II). Hovever, thiol depletion in plasma by pretreatment with N-ethylmaleimide (NEM)decreased Fe(II)-induced chemiluminescence significantly, suggesting that Fe(II) generated superoxide anion by the nonenzymatic reaction with plasma thiol. Consistent with this findings, albumin, the major thiol contributor in plasma, also generated ROS with Fe(II) and this generation was inhibited by pretreatment with NEM. Treatment with Fe(II) to plasma resulted un significant reduction of oxygen radical absorbance capacity (ORAC) value, suggest that total antioxidant capacity could diminished in iron overload state. In conclusion, In iron overload state, plasma may be affected by oxidative stress mediated by nonenzymatic reaction of Fe (II)with plasma thiol.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.11
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• pp.1054-1062
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• 2010

Oxidative coupling reactions of humic substances (HS) can be catalyzed by a variety of natural extracellular enzymes and metal oxides. In this study, property changes of HS induced by a natural enzyme, horseradish peroxidase (HRP), and the effect of it to microfiltration (MF) were investigated. PAHA was transformed by oxidative coupling reaction with HRP and hydrogen peroxide ($H_2O_2$), verifying the catalytic effects of the HRP. Size exclusion chromatography (SEC) revealed that weight-average molecular weight (MWw) of PAHA was proportionally increased with the dosages of HRP and $H_2O_2$, indicating the transform action of HS into larger and complex molecules. An increase in the conformational stability of HS was achieved through the promotion of intermolecular covalent bondings between heterogeneous humic molecules. Spectroscopic analysis (fluorescence and infrared spectroscopy) proved that functional groups were transformed by the reaction. Additionally, HS and transformed products were undergone microfiltration (MF) to examine the treatment potential of them in a water treatment facility. Original HS could not be removed by MF but larger molecules of transformed products could be removed. Meanwhile, transformed products caused more fouling on the filtration than original HS. This results proved that natural organic matter (NOM) can be removed by MF after its increase in molecular size by oxidative coupling reaction.

• Proceedings of the Korean Biophysical Society Conference
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• 2001.06a
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• pp.41-41
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• 2001

Ascorbate peroxidase catalyze the oxidation of ascorbic acid through the reaction with hydrogen peroxide. Ascorbic acid are utilized as a substrate in oxidative stress. In Candida albieans, ascorbic acid is used as antioxidants, so called D-erythroascorbic acid (EASe). Oxidative stress change concentrations of EASC resulting in interaction with alternative oxidase (AOX).(omitted)

• The Journal of Natural Sciences
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• v.5 no.2
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• pp.3-11
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• 1992

As concentration of ADP was increased, the rate of phosphocreatine formation by respiring heart mitochondria was increased. The value of apparent Km of the phosphocreatine-forming mitochondria for ADP was estimated to be 0.0185 mM. This value was much lower than that of Km for ATP (0.31 mM) which was determined from the reaction of the soluble form of mitochondrial creatine kinase. The concentration of ATP remained constant during the respiring in the presence of ADP. The rate of accumulation of oxidative-phosphorylated ATP in the mitochondrial respiration medium was continuously monitored as a function of ADP concentration with the firefly luciferase-coupled assay. In that case, exogenous creatine did not affect the rate of accumulation of ATP, indicating that phosphocreatine-forming (i.e.,respiring) mitochondria in the presence of ADP did not use the ATP in the medium as a substrate.These results suggest that the heart mitochondrial creatine kinase bound to the inner membrane functionally tight-coupled to the oxidative phosphorylating system with respect to the respired ATP.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.43-46
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• 2004

Explosive chemicals have been major soil and groundwater contaminants especially in the nations with active military activities. Of these explosives, 2,4,6-trinitrotoluene (TNT) is the most refractory one due to its structural characteristics. Although its efficient reduction by Fe(0) is well-known, the reduction products - mainly aminotoluenes - still possess toxicities to terrestrial biota, and are resistant to biological degradation. In this study, therefore, abiotic transformation of TNT reduction products via oxidative-coupling reaction was evaluated using Mn oxide which is ubiquitous in natural soils. The transformation efficiency is increased with the number of amino groups. Considering the very efficient reduction rate of TNT by Fe(0), Mn oxide can be successfully used for the removal of TNT reduction products.

• BMB Reports
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• v.43 no.10
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• pp.683-687
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• 2010

Previous studies have shown that one of the primary causes of increased iron content in the brain may be the release of excess iron from intracellular iron storage molecules such as ferritin. Free iron generates ROS that cause oxidative cell damage. Carnosine and related compounds such as endogenous histidine dipetides have antioxidant activities. We have investigated the protective effects of carnosine and homocarnosine against oxidative damage of DNA induced by reaction of ferritin with $H_2O_2$. The results show that carnosine and homocarnosine prevented ferritin/$H_2O_2$-mediated DNA strand breakage. These compounds effectively inhibited ferritin/$H_2O_2$-mediated hydroxyl radical generation and decreased the mutagenicity of DNA induced by the ferritin/$H_2O_2$ reaction. Our results suggest that carnosine and related compounds might have antioxidant effects on DNA under pathophysiological conditions leading to degenerative damage such as neurodegenerative disorders.

• Bulletin of the Korean Chemical Society
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• v.23 no.6
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• pp.817-824
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• 2002

Granular activated carbon(GAC) is highly effective in removing organic compounds which are resistant to biological disintegration in wastewater treatment. However, GAC has reached its full adsorptive capacity, GAC needs to be regenerated before it can be used for a further adsorption cycle. Countercurrent oxidative reaction (COR) technique has been developed and evaluated for the regeneration of spent GAC. Various parameters such as flame temperature, the loss of carbon, destruction and removal efficiency (DRE) of organic compounds, surface area, surface structure, adsorptive capacity, etc. were examined to determine the performance of COR. The results of these tests showed that adosorptive capacity of regenerated GAC was completely recovered, the loss of carbon was controllable, flame temperature was high enough to insure complete destruction and removal $(\geq99.9999%)$ of specific organics of interest, polychlorinated biphenyls (PCBs), that are thermally stable, and on formation of toxic byproducts such as polychlorinated dibenzo-p-dioxins (PCDDs) or polychlorinated dibenzofurans (PCDFs) were detected during the regeneration process. The COR technique is environmentally benign, easy to use and less copital intensive than other available regeneration technologies.

• Bulletin of the Korean Chemical Society
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• v.10 no.5
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• pp.443-447
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• 1989

The mechanism on the oxidative addition reaction of $(TBA)_2\;Pt(CN)_4$ with $Cl_2$ has been studied by means of extended Huckel calculations. Among two possible mechanisms, computational calculations demonstrated that the linear approach of $Cl_2$ to a $Pt(CN)_4$ moiety is more favourable than three-centered transition state. From our calculations, the most stable process is that a $Pt(CN)_4$ moiety interacts with $Cl_2$ in the linear transition state and the cleavage of Cl-Cl bond in a coordinated halogen occurred spontaneously, giving rise to a trans product by back-attacking a $Pt(CN)_4Cl$ moiety by Cl. The process consists of the comparison in the stability of each intermediate with use of bonding and potential energy.

• Bulletin of the Korean Chemical Society
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• v.19 no.10
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• pp.1084-1090
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• 1998

The oxidation of triphenylphosphine by [(tpy)(phen)RuⅣ(O)]2+ and [(bpy)(p-tert-butylpy)RuⅣ(0)]2+ (tpy is 2,2': 6',2"-terpyridine, phen is 1,10-phenanthroline, bpy is 2,2'-bipyridine, and p-tert-butylpy is para-tertbutylpyridine) in CH3CN has been studied. Experiments using 18O-labeled complex show the oxyl group transfer from [RuⅣ=O]2+ to triphenylphosphine occured quantitatively within experimental error. Kinetic data were fit to a second-order for [RuⅣ=O]2+ and [PPh3]. The initial product, [RuⅡ-OPPh3]2+, was formed as an observable intermediate and then underwent slow solvolysis. The reaction proceeded as endothermic in activation enthalpy and a decrease in activation entropy. The oxidative reactivity of four representative ruthenium mono-oxo oxidants against triphenylphosphine was compared. These systems have been utilized as electrochemical oxidative catalysts.