• Bulletin of the Korean Chemical Society
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• v.24 no.8
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• pp.1188-1192
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• 2003

In order to study the role of residue in the active site of glutathione S-transferase (GST), Tyr 108 residue in human GST P1-1 was replaced with alanine, phenylalanine and tryptophan by site-directed mutagenesis to obtain mutants Y108A, Y108F and Y108W. These three mutant enzymes were expressed in Escherichia coli and purified to electrophoretic homogeneity by affinity chromatography on immobilized GSH. The substitutions of Tyr108 significantly affected $K_m^{CDNB}$ and $K_m^{ETA}$, whereas scarcely affected $K_m^{GSH}$. The substitutions of Tyr108 also significantly affected $I_{50}$ of ETA, an electrophilic substrate-like compound. The effect of these substitutions on kinetic parameters and the response to inhibition suggests that tyrosine 108 in hGST P1-1 contributes to the binding of the electrophilic substrate and a major determinant in the binding of CDNB is the aromatic ring of Tyr108, not its hydroxyl group.

• Molecular & Cellular Toxicology
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• v.1 no.3
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• pp.157-163
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• 2005

Because of their widespread occurrence and substantial biological activity, halogenated aromatic hydrocarbons are one of the important classes of contaminants in the environment. We have performed comparative molecular field analysis (CoMFA) on structurally diverse ligands of Ah (dioxin) receptor to explore the physico-chemical requirements for binding. All CoMFA models have given $q^{2}$ value of more than 0.5 and $r^{2}$ value of more than 0.83. The predictive ability of the models was validated by an external test set, which gave satisfactory predictive $r^{2}$ values. Best predictions were obtained with CoMFA model of combined modified training set ($q^{2}=0.631,\;r^{2}=0.900$), giving predictive residual value = 0.002 log unit for the test compound. We have suggested a model comprises of four structurally different compounds, which offers a good predictability for various ligands. Our QSAR model is consistent with all previously established QSAR models with less structurally diverse ligands. The implications of the CoMFA/QSAR model presented herein are explored with respect to quantitative hazard identification of potential toxicants.

• Journal of the Korean Ceramic Society
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• v.34 no.9
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• pp.963-968
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• 1997

Coal tar pitch was used to study the effect of the pyrolysis conditions to produce mesophase pitch used as a matrix precursor for carbon/carbon composites. The pyrolysis conditions were presented in all cases that the total pressure was 1 atm and the first stage temperature was changed from 25$0^{\circ}C$ to 34$0^{\circ}C$ to remove the low molecular weight compounds in the pitch, and then, heated to 40$0^{\circ}C$ to form anisotropic mesophase as the second stage temperature. The first stage temperature was very affected to form resulting anisotropic mesophase pitch. The resulting mesophase pitches show a significantly increased anisotropic contents upto 30$0^{\circ}C$. However, the contents of mesophase were decreased above 30$0^{\circ}C$. It was the reason that the first stage temperature had been control the number of free radicals to react the aromatic compounds in the pitch to form high molecular weight compound. Therefore, the two stage pyrolysis method could be very effectively used to control various contents of anisotropic polyaromatic mesophase compared to continuous to continuous heating method.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.247-250
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• 2008

Biomass gasification is a promising technology for producing a fuel gas which is useful for power generation systems. In biomass gasification processes, tar formation often causes some problems such as pipeline plugging. Thus, proper tar treatment is necessary. So far, nickel (Ni)-based catalysts have been intensively studied for the catalytic tar removal. However, the deactivation of Ni-based catalysts takes place because of coke deposition and sintering of Ni metal particles. To overcome these problems, we have been using ruthenium (Ru)-based catalyst for tar removal. It is reported by Okada et al., that a Ru/$Al_2O_3$ catalyst is very effective for preventing the carbon deposition during the steam reforming of hydrocarbons. Also, this catalyst is more active than the Ni-based catalyst at a low steam to carbon ratio (S/C). Benzene was used for the tar model compound because it is the main constituent of biomass tar and also because it represents a stable aromatic structure apparent in tar formed in biomass gasification processes. The steam reforming process transforms hydrocarbons into gaseous mixtures constituted of carbon dioxide ($CO_2$), carbon monoxide (CO), methane ($CH_4$) and hydrogen ($H_2$).

• Membrane Journal
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• v.17 no.1
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• pp.1-13
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• 2007

Pervaporation process using membrane is newly emerging energy saying and cost effect process instead of distillation process. Especially, in pertrochemical industry, pervaporation process is a strong candidate to substitute the conventional energy consuming processes because that petrochemical industry has much energy consuming separation processes, many azeotrope mixtures to separate and needs to compact space to install new process units. Aromatic/aliphatic separation including benzene/cyclohexane mixture, olefin/paraffin separation, xylene isomer separation, reactive monomer recovery and sulfur compound removal from gasoline have been inversitigated for the application of pervaporation membrane process by many researchers and are under commercializing.

• Mass Spectrometry Letters
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• v.4 no.1
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• pp.18-20
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• 2013

Headspace solid phase micro-extraction gas chromatography/flame ionization detection (HS-SPME-GC/FID) method was compared with headspace gas chromatography/mass selective detection (HS-GC/MS). Organic solvent-spiked urine as well as urine samples from workspace was analyzed under optimal condition of each method. Detection limit of each compound by HS-SPME-GC/FID was $3.4-9.5{\mu}g/L$, which enabled trace analysis of organic solvents in urine. Linear range of each organic solvent was $10-400{\mu}g/L$, with fair correlation coefficient between 0.992 and 0.999. The detection sensitivity was 4 times better than HS-GC/MS in selected ion monitoring (SIM) mode. Accuracy and precision was confirmed using commercial reference material, with accuracy around 90% and precision less than 4.6% of coefficient of variance. Among 48 urine samples from workplace, toluene was detected from 45 samples in the range of $20-324{\mu}g/L$, but no other solvents were found. As a method for trace analysis, SPME HS GC/FID showed high sensitivity for biological monitoring of organic solvent in urine.

• Microbiology and Biotechnology Letters
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• v.16 no.3
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• pp.199-204
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• 1988

A strain capable of growth on naphthalene minimal medium was isolated from soil by selective enrichment culture and identified as Pseudomonas putida N3 according to its morphological and physiological characteristics. The optimum pH and temperature for growth of the isolate were 7.0 and 3$0^{\circ}C$, respectively. This strain was resistant to ampicillin, chloramphenicol, kanamycin and streptomycin but. sensitive to tetracycline and rifampicin. Of the naphthalene related compounds, 1, 5-dihydroxynaphthalene was more easily utilized than naphthalene due to its solubility. And catechol was degraded through meta-cleavage pathway. A 110 Kb plasmid which encodes for a single set of enzymes responsible for the degradation of naphthalene was obtained.

• Journal of Environmental Science International
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• v.18 no.2
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• pp.215-219
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• 2009

Micropollutants, which can be caused by imperfect combustion, are toxic chemical compound that flows into the river system after being contained in road runoff, a non-point source pollutant and accumulates in the body. The micropollutants that have characteristics such as toxicity, persistence, bio-accumulation, long-range transportation behave so similarly to micro particles that they can be removed by means of filtration or absorption. This study has examined the kinds and concentrations of micropollutants contained in deposited road particles. It has revealed that the kinds of micropollutants contained in the clarified supernatant liquid of deposited road particles are heavy metals and polycyclic aromatic hydrocarbons(PAHs) composed of two or three benzene rings, including naphthalene and acenaphthalene. Their concentrations have been shown to be low, with 0.418 mg/L, 0.058 mg/L, 0.104 mg/L, 0.014 mg/L, 0.00075 mg/L for Zn, Pb, Cu, Cr, Cd, respectively and 0.00156 mg/L and 0.00184 mg/L for naphthalene and acenaphthalene.

• Journal of the Korean Chemical Society
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• v.34 no.4
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• pp.360-369
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• 1990

Borosilicate, HZSM-5 zeolite and iron-substituted borosilicate and HZSM-5 zeolite were prepared and their catalytic properties in methanol conversion were studied. The effects of strength and amount of acid site determined from TPD spectra of ammonia on the product distribution was examined. Selectivity to propylene was high over borosilicate with small amount of strong acid site, but selectivity to aromatic compound was high over HZSM-5 zeolite with large amount of the strong acid site. The participation of weak acid site on the conversion did not confirmed, and the product distribution could be explained in terms of the amount of the strong acid site. Although the amount of the weak acid site was increased by substitution of iron, there was no meaningful change in the product distribution.

• YAKHAK HOEJI
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• v.40 no.6
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• pp.632-639
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• 1996

Most stable conformers of some antiinflammatory fenamates were obtained by conformational free energy change calculations. Conformational energies for the molecules as unhydrate d state were estimated first, and those as hydrated state were calculated then to simulate the molecules in aqueous solution using a hydration shell model. The initial geometries of the molecules were obtained either from X-ray crystallographic data or from homologous molecular fragments. The bond lengths and angles were not varied, but all the torsion angles were varied step by step during the conformational free energy surface searching. The results show that there are several feasible conformations for a compound. And the molecules are somewhat stabilized by hydration (-${\delta}G_{hyd}{\cong}$13 to 16kcal/mole), but the conformations were not changed significantly by the hydration itself. There seems to be a strong tendency of intramolecular hydrogen bonding between imino hydrogen and carboxyl oxygen of the compounds. As a result, the carboxyl group cannot be rotated freely, and the rotation of the second aromatic ring is the main reason for the conformational variations of the compounds. The ECEPP force fields via the program CONBIO were used throughout this study.