• Journal of Microbiology and Biotechnology
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• v.18 no.10
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• pp.1701-1708
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• 2008

Previous investigations showed that three classes of haloaromatic compounds (HACs; chlorobenzoates, chlorophenols, and chlorobenzenes) enhanced the reductive dechlorination of Aroclor 1248, judging from the overall extent of reduction in CI atoms on the biphenyl. In the present study, we further investigated the kind of polychlorinated biphenyl (PCB) congeners involved in the enhanced dechlorination by four isomers belonging to each class (2,3-, 2,5-, 2,3,5-, and 2,4,6-chlorobenzoates; 2,3-, 3,4-, 2,5-, and 2,3,6-chlorophenols; and 1,2-, 1,2,3-, 1,2,4-, and penta-chlorobenzenes). Although the PCB congeners involved in the enhanced dechlorination varied with the HACs, the enhancement primarily involved para-dechlorination of the same congeners (2,3,4'-, 2,3,4,2'-plus 2,3,6,4'-, 2,5,3',4'- plus 2,4,5,2',6'-, and 2,3,6,2',4'-chlorobiphenyls), regardless of the HACs. These congeners are known to have low threshold concentrations for dechlorination. To a lesser extent, the enhancement also involved meta dechlorination of certain congeners with high threshold concentrations. There was no or less accumulation of 2,4,4'- and 2,5,4'-chlorobiphenyls as final products under HAC amendment. Although the dechlorination products varied, the accumulation of ortho-substituted congeners, 2-, 2,2'-, and 2,6-chlorobiphenyls, was significantly higher with the HACs, indicating a more complete dechlorination of the highly chlorinated congeners. Therefore, the present results suggest that the enhanced dechlorination under HAC enrichment is carried out through multiple pathways, some of which may be universal, regardless of the kind of HACs, whereas others may be HAC-specific.

• Biomolecules & Therapeutics
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• v.3 no.2
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• pp.132-135
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• 1995

Several clofibrate congeners (bezafibrate, gemfibrozil and fenofibrate) were investigated the relationship between effects on the aggregation induced by aggregating agents (thrombin, arachidonic acid, ADP and collagen) and arachidonic acid metabolism in rabbit homogenized platelet. In platelet aggregation study, all drugs produced no significant inhibition (data not shown) in arachidonic acid and thrombin. Also platelet aggregation by ADP was not changed in bezafibrate and Inhibited dose dependently in fenofibrate and gemfibrozil. Platelet aggregation by collagen was inhibited dose dependently and significantly (from p<0.5 to p<0.001) by gemfibrozil and fenofibrate at concentrations between 20 and 400 $\mu$M. In arachidonic acid metabolism study, synthesis of thromboxane $B_2$ was not changed in rabbit platelet membranes and that of prostaglandin $E_2$ and $F_{2{\alpha}}$ was slightly increased by all drugs. It was concluded that clofibrate congeners inhibited ADP and collagen induced rabbit platelet aggregation and inhibition of collagen induced aggregation was probably mediated through some mechanism (pathway) other than arachidonic acid metabolism, judging from arachidonic acid metabolites (thromboxane $B_2$, prostaglandin $E_2$and $F_{ 2{\alpha}}$) synthesis in rabbit homogenized Platelet.

• Journal of Environmental Health Sciences
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• v.32 no.2 s.89
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• pp.111-117
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• 2006

Polybrominated diphenyl ethers (PBDEs) in pine needles and soil samples from rural area were analyzed in this study. Concentrations of PBDE congeners were ranged between 0.2 and 3104 pg/g DW(dry weight) in pine needles and between 2.4 and 1997 pg/g DW in soil samples. The most abundant congener both in pine needles and soil samples was BDE-209, which was related to importation and production of deca-BDE technical mixtures in Korean industry. And BDE-99, BDE-47, BDE-100 deposited in pine needles and soil samples were closely matched with the major constituents of the penta-BDE technical mixture. Those can be interpreted as an evidence that transfer of the congeners in deca-BDE and penta-BDE technical mixtures from source to pine needle and soil occurs with broadly similar efficiency. Correlation coefficient(r) of PBDE congeners deposited in pine needles and soil samples is very significant because it implies th at there has been little weathering/degradation/alteration of the congeners generated from sources during atmospheric transport or within pine needles and soil themselves.

• Bulletin of the Korean Chemical Society
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• v.24 no.6
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• pp.792-796
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• 2003

Polychlorinated dibenzo-p-dioxins (PCDDs) are extremely toxic and persistent environmental pollutants. Their chemical reactivities and other physicochemical/biological properties show a strong dependence on the chlorination pattern. With increasing the number of chlorines, dioxin congeners become more electronegative and gain higher electron affinities. The vertical electron affinities (VEA) are related with the LUMO energies of neutral molecules. LUMO energies of all PCDD congeners were calculated at the B3LYP/6-31G** level and those of some selected congeners at the level of B3LYP/6-311G**//B3LYP/6-31G** and B3LYP/cc-pvtz/ /B3LYP/6-31G**. The total energies of neutral and anionic species for dibenzo-p-dioxins (DD), 1469-TCDD, 2378-TCDD, and OCDD were calculated at the level of B3LYP/6-31G**, B3LYP/aug-cc-pvdz, and B3LYP/ aug-cc-pvtz//B3LYP/6-31G**. By using the four congeners with D2h symmetry as reference molecules, we could estimate VEA (B3LYP/aug-cc-pvdz) of 75 PCDD congeners based on the linear correlations between LUMO energy and VEA (B3LYP/6-31G**) and between VEA (B3LYP/6-31G**) and VEA (B3LYP/aug-ccpvtz// B3LYP/6-31G**). Results show that all PCDDs with the number of Cl ≥ 3 have positive electron affinities. The PCDD electron affinity values provided in this work can be a useful data set in understanding the congener-specific reactivities of dioxins in various environmental media.

• Analytical Science and Technology
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• v.17 no.4
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• pp.347-354
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• 2004

We collected crucians (Carassius auratus) and leopard frogs(Rana pipiens) along the Nakdong River and the basin area at five locations from Koomi to Nakdong-estuary. The muscular tissue were separated and a GC-MSD system was used for quantification of PCBs. The 62 PCB congeners which represent total PCB levels were selected as analytes. We determined concentrations of PCBs and studied distribution characteristics by individual congeners and homologs. In the crucian, 24 congeners were detected and total PCB levels ranged from 0.74 to 5.41 ng/g wet weight. In the leopard frog, however, only 2 congeners were detected from Nakdong estuary only. The PCB level was 0.24 ng/g wet weight, around 22 times lower than the crucians. The PCB 153 showed the highest concentrations in the congeners and penta- and hexa-CBs showed the strong predominance which accounted for 78% of the total PCBs.

• Analytical Science and Technology
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• v.16 no.4
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• pp.309-319
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• 2003

This study was performed to describe analysis method of 209 PCB congeners in ambient air samples. The samples were collected by high volume air sampler in Chonju city. Extracted samples were cleaned by silicagel cleanup modified with sulfuric acid and activated carbon cleanup processing. The cleaned samples were analyzed by high resolution gas chromatography and high resolution mass spectrometry (HRGC/HRMS) with DB-5 column (60 m, 0.25 mm i.d., 0.25 m film thickness) to analyze the 209 kinds of PCB congeners. PCBs levels of air samples were detected to the range between 0.003 and $0.163pg-TEQ/m^3$. The PCBs congener of 162 kinds were detected in samples analysed using DB-5 column and 37 kinds peaks were overlapped with congeners more than one. It is difficult to isolate PCB 118/106 and PCB 105/127 in coplanar PCB, so it is likely to overestimate the concentration.. The distribution of coplanar-PCB congeners in origin source samples (Kanechlor and exhaust gas from incinerator) was compared with that in air samples, and PCB 81, PCB 77, PCB 126, and PCB 169 were higher in incinerator samples.

• Animal cells and systems
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• v.1 no.2
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• pp.297-304
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• 1997

Two new harpacticoid species of family Thalestridae are described on the basis of the specimens collected from the shallow sublittoral sand bottom or seagrasses of rocky shore in South Korea. Dactylopusia pauciarticulata n. sp. is discernible from its 19 congeners by the 6-articulated antennule. Paradactylopodia koreana n. sp. most resembles P. striata Kunz, 1973 of its seven congeners, but obviously distinguished from it by the shape of male leg 2 endopod.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 1999.10a
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• pp.225-228
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• 1999

The formation of dioxin (term used here to refer to both polychlorinated dibenzo-p-dioxins, PCDDS, and dibenzofurans, PCBFs) in combustion processes is of concern because of the extreme toxicities of some of these compounds and because of their resistance to degradation in the environment. The number and location of chlorine substituents differentiate dioxin homologues and isomers, respectively. There are a total of 75 PCDD congeners and 135 PCDF congeners.(omitted)

• Animal Systematics, Evolution and Diversity
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• v.33 no.1
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• pp.33-36
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• 2017

Two new Hydropsychidae (Insecta: Trichoptera) species from the Philippines are described. Hydropsyche philippinensis, n. sp., differs from other congeners in the structure of the phallic apparatus. Diplectrona lagunensis, n. sp., can be distinguished from other congeners by its distinct white band pattern in the forewings and by the structure of the phallus. Both new species were collected from a high mountain stream in the northern part of the Philippines. Paratype materials were barcoded to make the sequences readily available in the GenBank.

• Journal of Microbiology and Biotechnology
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• v.18 no.9
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• pp.1564-1571
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• 2008

We investigated whether the threshold concentration for polychlorinated biphenyl (PCB) dechlorination may be lower in biosurfactant-amended sediments compared with biosurfactant-free samples. At PCB concentrations of 40, 60, and 120 ppm, the surfactant amendment enhanced the PCB dechlorination rate at all concentrations and the rate was also faster at higher concentrations. On a congener group basis, dechlorination proceeded largely with group A (congeners with low threshold) in both surfactant-free and -amended sediments, accumulating mainly group C (residual products of dechlorination) congeners, and surfactant enhanced the dechlorination rate of group A congeners. Since the PCB threshold concentration for the inoculum in the experiment was lower than 40 ppm, we carried out another experiment using sediments with lower PCB concentrations, 10, 20, and 30 ppm. Sediments with 100 ppm were also performed to measure dechlorination at a PCB saturation concentration. Comparison between the plateaus exhibited that the extent of dechlorination below 40 ppm PCBs was much lower than that at a saturation concentration of 100 ppm. There was no significant difference in the extent of dechlorination between surfactant-free and -amended sediments. Moreover, surfactant did not change the congener specificity or broaden the congener spectrum for dechlorination at PCB concentrations below 40 ppm. Taken together, it seems that at a given PCB concentration, dechlorination characteristics of dechlorinating populations may be determined by not only the congener specificity of the microorganisms but also the affinity of dechlorinating enzyme(s) to individual PCB congeners.