• Bulletin of the Korean Chemical Society
• /
• 제20권10호
• /
• pp.1172-1176
• /
• 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.

• 한국항해항만학회:학술대회논문집
• /
• 한국항해항만학회 2016년도 춘계학술대회
• /
• pp.130-131
• /
• 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
• /
• 제2권3호
• /
• pp.79-81
• /
• 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.

• 한국환경농학회지
• /
• 제26권2호
• /
• pp.131-140
• /
• 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
• /
• 한국환경농학회 2011년도 30주년 정기총회 및 국제심포지엄
• /
• pp.128-135
• /
• 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
• /
• 제14권1호
• /
• pp.57-62
• /
• 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.

• 미생물학회지
• /
• 제50권3호
• /
• pp.254-260
• /
• 2014

황화합물은 혐기성환경에서 혐기성호흡을 위한 매우 중요한 전자수용체이다. 본 연구를 통하여 한국의 다양한 습지에서 배양을 통한 황산염/황-환원세균의 특성연구를 실시하였다. 이를 분리하기 위하여 혐기성 roll tube법을 통해 총 11개의 순수 배양체를 확보하였다. 16S rDNA를 이용한 계통분석 및 상동성 분석을 실시하여 Desulfovibrio 속의 세균 8종, Sulfurospirillum 속의 세균 2종, Desulfitobacterium 속의 세균 1종을 얻을 수 있었다. 이들 황산염/황-환원세균은 모두 lactate와 pyruvate를 전자공여체로 이용하였으며, sulfite and thiosulfate를 전자수용체로 이용할 수 있었다. 앞으로, 다양한 전자공여체와 배양조건을 통하여 유용한 절대혐기성 황산염/황-환원세균의 생물자원 확보에 기여할 것으로 기대된다.

• 한국미생물·생명공학회지
• /
• 제38권4호
• /
• pp.448-454
• /
• 2010

광양, 하남, 여천지역의 토양, 하천 및 해양 퇴적물 등을 이용하여, 난분해성 염소화합물인 PCE (perchloroethylene) 및 TCE(trichloroethylene)의 혐기성 탈염소화에 관련하는 미생물을 탐색하고 이들의 탈염소화 효율을 조사하였다. 혐기성 상호대사에 의한 탈염소화 효율을 조사하기위해 전자 공여체로 아세테이트를 사용하여 혐기성 회분식 실험을 실시 하였으며, 미생물 군집을 분석하기 위해, 분자생물학적인 기법인 16S rDNA의 DGGE 기법을 이용하였다. 그 결과, 4주간 집적배양을 통해 광양, 하남, 여천시료는 PCE와 TCE를 PCE 75% 이상, TCE 81% 이상 탈염소화하는 것으로 나타내며, 여천시료가 우수한 PCE/TCE탈염소화율을 보이고 있다(PCE 87.37%, TCE 84.46%). 또한, 전자 수용체에 따른 탈염소화 배양액의 미생물 다양성은 DGGE로 분석하였으며, 우점하는 미생물은 Clostridium sp., Desulfotomaculum sp.와 unculutured bacteria로 나타났다.

• 한국해양학회지:바다
• /
• 제8권2호
• /
• pp.210-224
• /
• 2003

황산염 환원은 혐기성 해양환경에서 황산염 환원 박테리아가 진행시키는 미생물 반응이다. 황산염 환원 반응은 저층으로 공급되는 유기물 분해의 상당 부분을 담당하며, 이때 발생되는 황화가스의 독성 및 주변 금속과의 높은 반응성, 그리고 유기물 분해시 유리되는 무기 영양염들의 수층 용출 등으로 인해 연안생태계 내의 생물 다양성 및 생지화학적 물질의 순환경로에서 중요한 역할을 한다 여러 해양환경의 퇴적토에서 보고 된 황산염 환원율과 이에 영향을 미치는 주요한 환경요인들에 대해 정리한 결과, 공급되는 유기물과 여러 전자수용체들(산소, 질산염, 산화 철, 망간 등)의 분포가 황산염 환원율 및 유기물 분해시 황산염 환원의 상대적 중요성에 직접 영향을 미치는 것으로 나타났다 아울러 전자수용체의 분포와 유기물의 양과 질을 조절하는 요인으로서 온도, 식생의 유무, 생물교란의 영향에 대해 토의하였다. 끝으로, 우리나라와 같이 갯벌이 발달되고, 유기물 부하가 높은 인공양식장의 가동, 부영양화 등으로 인해 혐기성 환경과 적조의 발생빈도가 점증하는 상황에서 유기(오염)물 분해과정과 영양염 순환 경로를 보다 잘 이해하기 위해서 황산염 환원을 중심으로 한 다양한 혐기성 미생물 생태연구가 중요함을 제안한다.

• Applied Biological Chemistry
• /
• 제21권2호
• /
• pp.112-118
• /
• 1978

소의 갑상선에서 추출한 Xanthine oxidase를 disc gel eleectrophoresis로서 정제도(Purity)를 측정하여 Xanthine oxidase 이외의 다른 불순 단백질이 나타나지 않을 때까지 정제하였다. 그 정제 과정은 Pancreatin digestion, butanol 추출, ammonium sulfate 단백질 침전, calcium phosphate gel-cellulose column chromatography, gel filtration, preparative Sephadex G-25 column electrophoresis와 Preparative polyacrylamide gel electrophoresis 등을 포함하고 있다. 이러한 과정을 통하여 갑상선 Xanthine oxidase는 1,000배 정도 정제되었다. 그러나 효소의 비활성도(Specific activity)는 우유에서 추출한 이 효소에 상응하는 정도로 정제된 효소의 비활성도와 비교 되었을 때 지극히 낮았다. 갑상선 Xanthine oxidase도 효소 반응에 필요한 기질과 electron acceptor의 특수성(Specificity)이 어느 특수한 한 기질에 한정되지 않았음을 보였고 Kinetic 성질도 우유에서 추출된 Xanthine oxidase와 비교하였을 때 가장 일반적인 Xanthine oxidase 기질에 대한 Michaelis 상수(Km)가 약간의 예외도 있었으나 상당히 비슷하였다.