• Bulletin of the Korean Chemical Society
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• v.20 no.10
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• pp.1172-1176
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• 1999

Nucleophilic substitution reaction of Y-benzyl bromide with X-pyridines are investigated in DMSO at 45.0℃. Biphasic rate dependence is observed on varying the substituents in the substrate (Y) as well as in the nucleophile (X). The two well-defined straight lines in the Hammett (ρy) and Bronsted ( βx) plots are interpreted to indicate the changes in transition-state structure, a decrease in bond cleavage as the substituent on the substrate is changed from electron-donors ( ρy < 0) to electron-acceptors ( ρy > 0), and an increase in the extent of bond formation with the corresponding changes of the substituent on the pyridine. A Jencks' type analysis of separate polar (ρ) and resonance (ρr) effects can also be accounted for by the change of the transition-state structure, not by the variable combination of polar and resonance effects.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2016.05a
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• pp.130-131
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• 2016

Although many metals contaminated sediment from coastal area contain both anionic and cationic heavy metals, the current remediation technologies are not effective for stabilize heavy metals of both anionic and cationic elements from contaminated coastal region. the present work investigated the efficiency and mechanism of immobilization of Fe, Zn, Cr, Cu, Pb and Cd metal solutions in modified zeolite based biostimulant ball. Biostimulant ball containing acetate, nitrate and sulphate which are enhance the activity of marine microorganisms and it can act as electron donors and electron acceptors. Modified zeolite and chelating agent is greatly enhance the metal stabilization due to increased immobility of the analysed metals. The XRD, FT-IR and SEM of modified zeolite which cheating agents containing heavy metals were investigated. The results indicated that heavy metals could be effectively immobilized in modified zeolite and chelating agents in BSB added sediment. The immobilization of heavy metals in modified zeolite and chelating agents along with BSB could be due to stabilize of heavy metal cations. Immobilization of heavy metals using BSB with modified zeolite and chelating agent has lower cost effect and enhance the sediment quality.

• Rapid Communication in Photoscience
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• v.2 no.3
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• pp.79-81
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• 2013

A novel method of fabricating polythiophene-gold nanoparticle composite film electrodes for photoelectric conversion is demonstrated. The method includes electrodeposition of gold and electropolymerization of 2,2'-bithiophene onto an indium-tin-oxide (ITO) electrode. First, electrodeposition of gold onto the ITO electrode was carried out with various repetition times of pulsed applied potential (0.25 s at -2.0 V vs. Ag/AgCl) in an aqueous solution of $HAuCl_4$. Significant progress of the number density of deposited gold nanoparticles was confirmed from scanning electron micrographs, from 4 (1 time) to 25% (15 times). Next, electropolymerization of 2,2'-bithiophene onto the above ITO electrode was performed under controlled charge condition (+1.4 V vs. Ag wire, 15 $mC/cm^2$). Structural characterization of as-fabricated films were carried out by spectroscopic and electron micrographic methods. Photocurrent responses from the sample film electrodes were investigated in the presence of electron acceptors (methyl viologen and oxygen). Photocurrent intensities increased with increasing the density of deposited gold nanoparticles up to ~10%, and tended to decrease above it. It suggests that the surplus gold nanoparticles exhibit quenching effects rather than enhancement effects based on localized electric fields induced by surface plasmon resonance of the deposited gold nanoparticles.

• Korean Journal of Environmental Agriculture
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• v.26 no.2
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• pp.131-140
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• 2007

Phospho-gypsum a primary waste by-product in phosphate fertilizer manufacturing industry and a potential source of electron acceptors, such as mainly of sulfate and a trace amount of iron and manganese oxides, was selected as soil amendment for reducing methane $(CH_4)$ emissions during rice cultivation. The selected amendment was added into potted soils at the rate of 0, 2, 10, and 20 Mg $ha^{-1}$ before rice transplanting. $CH_4$ flux from the potted soil with rice plant was measured along with soil Eh and floodwater pH during the rice cultivation period. $CH_4$ emission rates measured by closed chamber method decreased with increasing levels of phospho-gypsum application, but rice yield markedly increased up to 10 Mg $ha^{-1}$ of the amendment. At this amendment level, total $CH_4$ emissions were reduced by 24% along with 15% rice grain yield increment over the control. The decrease in total $CH_4$ emission may be attributed due to shifting of electron flow from methanogenesis to sulfate reduction under anaerobic soil conditions.

• 한국환경농학회:학술대회논문집
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• 2011.07a
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• pp.128-135
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• 2011

Consortia demonstrated the high capacities of anaerobic degradation of various aromatic compounds, which were successfully enriched from gley paddy soils under different conditions. Phenol and cresol was decomposed anaerobically using nitrate, ferric oxide or sulfate as electron acceptors. Biphenyl was degraded to $CO_2$, especially without addition of external electron acceptor. Alkylphenols with middle length of alkyl chain, were co-metaboliocally degraded with the presence of hydroxylbenzoate as the co-substrate under nitrate reducing conditions. The microorganisms responsible for the anaerobic co-metabolism was Thauera sp. Reductive dechlorination activity was also observed for polychlorophenols, fthalide, polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins with the presence of lactate, formate or $H_2$ as electron donor. The fthalide dechlorinator was classified as Dehalobacter sp. Coupling of two physiologically-distinct anaerobic consortia, aromatic ring degrader and reductive dechlorinator, resulted in the mineralization of pentachlorophenol under anaerobic conditions. These results suggested that gley paddy soils harbored anaerobic microbial community with versatile capacity degrading aromatic compounds under anaerobic conditions.

• Journal of Ginseng Research
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• v.14 no.1
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• pp.57-62
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• 1990

In order to Investigate the mechanism of the leaf-burning disease of ginseng (Panax ginseng C.A. Meyer), studies on the generation of singlet oxygen (1O2) and the photooxidation of the pigments were carried out in comparison with the ones of soybean (G1ycine max L). The studies were mainly focalized on the effects of light intensity, light intensity, inhibitor and electron donor/acceptor of the Photosynthetic electron transport system. When we measured the amounts of 1O2 generated in the thylakoids of ginseng and soybean by the irradiation of light (300 w/m2) as a function its time. It was identified that a higher amount of 1O2 was formed in the ginseng thylakoid than the case of soybean. A generation ratio of lO2 between ginseng and soybean sltbstantially identical in the range of light intensities 50∼150w/m2 However much higher amount of 1O2 was generated in ginseng by irradiation of strong intensity of light (200 500w/m2). Wave length dependency on the generation of 1O2 and the pigment photooxidation was observed on ginseng thylakoids; red light (600-700 nm) gave a maximum effect in the contrast with blur green light (400-60 nm). When the ginseng thylalioid was treated with the electron donor (Mn2+) and acceptors (DCPIP, FeCy) of the photosynthetic electron transport system. a drastic inhibition of 1O2 generation was observed. However, treatment with its inhibitors (DCMU, KCW) activated 1O2 generation. An interesting fact that an electron donor or acceptor of the photosystem II(P680) Inhibited 1O2 generation, suggests an intimate relationship between 1O2 generation and photosystem II.

• Korean Journal of Microbiology
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• v.50 no.3
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• pp.254-260
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• 2014

Sulfur compound includes major electron acceptors for anaerobic respiration. In this study, cultivation-based study on sulfate- and sulfur-reducing bacteria of various wetlands of Korea was attempted. To isolate sulfate- and sulfur-reducing bacteria, anaerobic roll tube method was used to obtain typical black colonies of sulfate- and sulfur-reducing bacteria. Total 11 strains obtained were tentatively identified based on comparative 16S rDNA similarity and physiological property analysis. All sulfate-reducing bacteria (8 strains) belonged to genus Desulfovibrio with >99% 16S rDNA similarities. Three sulfur reducing bacteria were also isolated: two and one isolates were affiliated with Sulfurospirillum and Desulfitobacterium, respectively. These sulfate- and sulfur-reducing bacteria were able to utilize lactate and pyruvate and sulfite and thiosulfate as common electron donors and electron acceptors, respectively. This case study will provide fundamental information for obtaining useful indigenous sulfate- and sulfur-reducing bacteria from Korean wetlands employing various combinations of cultivation conditions.

• Microbiology and Biotechnology Letters
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• v.38 no.4
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• pp.448-454
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• 2010

This study investigated the effect of PCE and TCE as electron acceptors on the bacterial composition of dechlorinating communities. The enrichment cultures reductively dechlorinating PCE and TCE were developed from three environment samples using acetate as electron donor. The cultures were prepared by sequential enrichment, which was seeded with sediment and dredged soil. Denatured gradient gel electrophresis (DGGE) of 16S rRNA gene fragment was used to compare the microbial communities of these three enrichment cultures. After incubation for 4 weeks, the removal efficiencies of PCE and TCE were highest from Yeocheon site (87.37% and 84.46%, respectively). PCE and TCE as electron acceptors affected the bacterial diversity and community profiles in the enrichment cultures. DGGE analysis showed that the dominant bacteria in PCE and TCE enrichment were belonged to Clostridium sp., Desulfotomaculum sp., and uncultured bacteria.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.2
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• pp.210-224
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• 2003

Sulfate reduction is a microbiological process which occurs ubiquitously in anaerobic marine environment. Sulfate reducing bacteria play a significant role in anaerobic decomposition of organic matter and regeneration of inorganic nutrients which supports the primary production in the water column (i.e., benthic-pelagic coupling) and, in special case, could be responsible for the harmful algal bloom in the coastal marine environment. Summary of the sulfate reduction rates reported in various marine sedimentary environments revealed that supply of organic substrates and presence of various electron acceptors (i.e., $O_2$, NO$_{3}$$^{[-10]}$ , Fe(III) and Mn(IV), etc.) for other aerobic and anaerobic respiration directly affect the sulfate reduction rate and relative significance of sulfate reduction in organic matter mineralization. Significance of temperature, macrophytes and bioturbation is discussed as factors controlling supply of organic substrates and distribution of electron acceptors. Finally, we suggest studies on the anaerobic microbiological processes associated with biogeochemical element cycles in the coastal environments of Korea where massive operation of organic enriched fish cage farm, frequent occurrence of toxic algal bloom and hypoxia and conservation of tidal flat are of major environmental issues.

• Applied Biological Chemistry
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• v.21 no.2
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• pp.112-118
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• 1978

Xanthine oxidase from bovine thyroid glands was purified to apparent homogeneity when judged by analytical disc gel electrophoresis. The purification procedures include pancreatin digestion, butanol extraction, ammonium sulfate precipitation, calcium phosphate gel adsorption, ultrafiltration, calcium phosphate gel-cellulose column chromatography, gel filtration, preparative Sephadex G-25 column electrophoresis, and preparative polyacrylamide gel electrophoresis. The enzyme was enriched 1,000-fold. However, its specific activity was markedly low as compared with highly purified milk enzyme. Thyroidal xanthine oxidase exhibited a low specificity for substrates and electron acceptors. The kinetic properties of thyroid xanthine oxidase were found to be similar to those of the milk enzyme on the basis of Michaelis constants for common substrates.