• Journal of Microbiology and Biotechnology
• /
• v.18 no.7
• /
• pp.1298-1307
• /
• 2008

In this study, we investigated the inhibition effects of single and mixed heavy metal ions ($Zn^{2+},\;Ni^{2+},\;Cu^{2+},\;and\;Cd^{2+}$) on iron oxidation by Acidithiobacillus ferrooxidans. Effects of metals on the iron oxidation activity of A. ferrooxidans are categorized into four types of patterns according to its oxidation behavior. The results indicated that the inhibition effects of the metals on the iron oxidation activity were noncompetitive inhibitions. We proposed a reduced inhibition model, along with the reduced inhibition constant ($\alpha_i$), which was derived from the inhibition constant ($K_I$) of individual metals and represented the tolerance of a given inhibitor relative to that of a reference inhibitor. This model was used to evaluate the toxicity effect (inhibition effect) of metals on the iron oxidation activity of A. ferrooxidans. The model revealed that the iron oxidation behavior of the metals, regardless of metal systems (single, binary, ternary, or quaternary), is closely matched to that of any reference inhibitor at the same reduced inhibition concentration, $[I]_{reduced}$, which defines the ratio of the inhibitor concentration to the reduced inhibition constant. The model demonstrated that single metal systems and mixed metal systems with the same reduced inhibitor concentrations have similar toxic effects on microbial activity.

• Archives of Pharmacal Research
• /
• v.14 no.2
• /
• pp.130-136
• /
• 1991

Nicotine (100 .mu. M) was incubated with microsomes (1 mg/ml) prepared from New Zealand White rabbits. On the basis of microsomal weight, the rate of nicotine oxidation were calculated on the basis of cytochrome P-450 concentration, the specific activity of the metabolic oxidation catalyzed by lung was approximately 4 times greater than liver (6.4 vs 1, 65 nmoles nicotine oxidized. nmole cytochrome $P-450^{-1}\;min{-1})$. These studies employed several methods of altering activities of specific isozymes present in pulmonary microsomes, including the use of the isozyme2 and 6 specific inhibitor $\alpha$-methylbenzyl ABT, metabolite inhibitors, norbenzphetamine and N-hydroxyamphetamine. TCDD induction and Arochlor 1260 pretreatment. These results support the conclusion that nicotine metabolism by rabbit lung microsomes is mediated primarily by cytochrome P-450 isozyme 2.

• Journal of the Korean Applied Science and Technology
• /
• v.29 no.1
• /
• pp.88-94
• /
• 2012

In this study, the current-voltage curves for metals were measured using cyclic voltammetry. The relationship between the electrochemical properties and surface states of metals were investigated by Scanning Electron Microscope (SEM). In cyclic voltammetry, we used a 3-electrode system for the electrochemical measurements. The measurement was conducted at the condition that consists of the first reduction from the initial potential to -1350 mV, continuous oxidation to 1650 mV, and last reduction to the initial potential. The scan rates were 50, 100, 150 and 250 mV/s. The results show the C-V characteristics of metals to be for an irreversible process, which was caused by the oxidation current from cyclic voltammogram, when monoethanolamine (MEA) was used as a corrosion inhibitor. When we used MEA as a corrosion inhibitor, the diffusion coefficient was decreased as the concentration of electrolyte was increased. In the SEM images of copper, we observed an increase of surface corrosion at the increased electrolyte concentration. Addition of $1.0{\times}10^{-3}M$ corrosion inhibitor MEA reduced the effect of corrosion prevention due to the relatively large diffusion coefficient at the electrolyte concentration of 0.1N.

• Biomolecules & Therapeutics
• /
• v.12 no.2
• /
• pp.92-100
• /
• 2004

Effect of the depletion or oxidation of GSH on mitomycin c (MMC)-induced mitochondrial damage and cell death was assessed in small cell lung cancer (SCLC) cells. MMC induced cell death and the decrease in the GSH contents in SCLC cells, which were inhibited by z-LEHD.fmk (a cell permeable inhibitor of caspase-9), z-DQMD.fmk (a cell permeable inhibitor of caspase-3) and thiol compound, N-acetylcysteine. MMC caused nuclear damage, release of cytochrome c and activation of caspase-3, which were reduced by N-acetylcysteine. The depletion of GSH due to L-butionine-sulfoximine enhanced the MMC-induced cell death and formation of reactive oxygen species in SCLC cells, whereas the oxidation of GSH due to diamide or $NH_2Cl$ did not affect cytotoxicity of MMC. The results show that MMC may cause cell death in SCLC cells by inducing mitochondrial dysfunction, leading to activation of caspase-9 and -3. The MMC-induced change in the mitochondrial membrane permeability, followed by cell death, in SCLC cells may be significantly enhanced by the depletion of GSH. In contrast, the oxidation of GSH may not affect cytotoxicity of MMC.

• Polymer(Korea)
• /
• v.24 no.2
• /
• pp.237-244
• /
• 2000

Phenolic resin used as a precursor of carbonized matrix for carbon-carbon composites was modified by addition of molybdenum disilicide (MoSi$_2$) in various concentrations of 0, 4, 12 and 20% by weight to improve the anti-oxidation properties of the composites. The green body was manufactured by a prepreg method and was submitted to carbonization up to 110$0^{\circ}C$. In this work, the oxidation behavior of carbon-carbon composites with MoSi$_2$ as an oxidation inhibitor was investigated at the temperature range of 600-100$0^{\circ}C$ in an air environment. The carbon-carbon composites with MoSi$_2$ showed a significantly improved oxidation resistance due to both the reduction of the porosity formation and the formation of mobile diffusion barrier for oxygen when compared to those without MoSi$_2$. Carbon active sites should be blocked, decreasing the oxidation rate of carbon. This is probably due to the effect of the inherent MoSi$_2$ properties, resulted from a formation of the protective layer against oxygen attack in the composites studied.

• Environmental Mutagens and Carcinogens
• /
• v.9 no.2
• /
• pp.87-96
• /
• 1989

Studies on the biodisposition of beta-nicotyrine by lung and liver microsomes was examined in order to provide a better understanding of its fate in this tissue. beta-nicotyrine (100$\mu$M) was incubated with microsomes (1 mg/ml) prepared from New Zealand White rabbits. The rate of oxidation observed in lung microsomal incubations was 1.7 nmoles $\beta$-nicotyrine oxidized mg$^{-1}$ min$^{-1}$ compared with 2.7 nmoles $\beta$-nicotyrine oxidized mg$^{-1}$ min$^{-1}$ by the liver microsomal preparation. However, when these rates were expressed as a function of cytochrome P-450 content, the specific activity of the metabolic oxidation catalyzed by lung (8.3 nmoles $\beta$-nicotyrine oxidized nmole cytochrome P-450$^{-1}$ min$^{-1}$) was approxiamtely 4 times greater than liver microsomes (2.3 nmoles $\beta$-nicotyrine oxidized nmole cytochrome P-450$^{-1}$ min$^{-1}$). Isozyme studies on the oxidation of $\beta$-nicotyrine employed several methods of altering activities of specific isozymes present in pulmonary microsomes, including the use of the isozyme 2 and 6 specific inhibitor $\alpa$-methyl ABT, metabolic inhibitor(MI) complex formation. The results of this inhibition study would appear to indicate the $\beta$-nicotyrine is metabolized predominantly by pulmonary isozyme 5.

• Bulletin of the Korean Chemical Society
• /
• v.16 no.9
• /
• pp.896-898
• /
• 1995

• Polymer(Korea)
• /
• v.25 no.3
• /
• pp.435-440
• /
• 2001

The objective of this study was to examine the effect of oxidation inhibitor contents on the work of adhesion, fracture toughness, and impact strength of the unidirectional carbon-carbon composites (C/C composites). The molybdenum disilicide ($MoSi_2$) used as an oxidation inhibitor was impregnated with phenolic resins to improve the anti-oxidation properties of the composites in different concentrations of 4, 12 and 20 wt%. Based on Wilhelmy equation, the work of adhesion of C/C composites was calculated by contact angle methods. Fracture toughness and impact strength were pressured by three-point bending test for the critical intensity factor ($K_IC$) and Izod test method, respectively. As a result, the composites made with $MoSi_2$ resulted in an increasing of both fracture toughness and impact strength. Especially, the composites made with 12 wt% $MoSi_2$ content showed the highest value of London dispersive component, $W_A\;^L$, in work of adhesion, resulting from improving the interfacial adhesion force among fibers, filler, and matrix in this system.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 1999.11a
• /
• pp.198-203
• /
• 1999

2D carbon/carbon composites have been prepared with and without addition of 1, 3 and 5wt% of oxidation inhibitor boron and then heat teated up to 1700, 2000, 2300, 2600 each. This paper presents the effects of boron on the mechanical properties of 2D C/C composites in terms of the acceleration of graphitization and also discussed about the retardation of air oxidation.

• Tribology and Lubricants
• /
• v.18 no.6
• /
• pp.396-401
• /
• 2002

ln this paper, the fuction of molybdenum dialkyl dithiophosphate (MoDTP) as an oxidation inhibitor of mineral oils was investigated and compared with 2,6-Di-tert-Butyl-4-Methylphenol (DBMP). Oxidation tests were conducted using an oxygen absorption apparatus. MoDTP showed anti-oxidation property, and length of induction time prolonged by increasing MoDTP concentration. However the induction time of DBMP was longer than those of MoDTP. The anti-oxidation property of MoDTP was found to be inferior to that of DBMP The capability of hydroperoxide decomposition ability with MoDTP was much greater than that with DBMP. However the rate constant of radical scavenging with MoDTP was much better than that with DBMP. It was found that the performance of MoDTP is exellent with respect to hydroperoxide decomposition but it is susceptible to chemical decomposition. From the fact that formation of phenol was observed when MoDTP was added to hexane solution of cumene hydroperoxide (CHPO), it is indicated that the decomposition of hydroperoxide with MoDTP occurs by means of ionic mechanism.