• Korean Journal of Environmental Agriculture
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• v.15 no.2
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• pp.246-261
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• 1996

Organophosphorus pesticides, which are an important part of synthetic pesticides in current use contain sulfur atom in their molecules and can be activated or detoxified by environmental and/or biological metabolism. Among the related metabolic reactions, oxidative processes are particularly important with their final products and the study on the reactive intermediates formed in those reactions is essential to elucidate the metabolic pathways and mechanisms and to understand the toxicological properties. This review dealt with the reactive intermediates formed in various reactions from the structural and mechanistic point of view for organophosphorus pesticides and related compounds.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1994.04a
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• pp.271-271
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• 1994

NADPH-dependent succinic semialdehyde reductase를 소의 뇌조직으로부터 여러가지 크로마토그래픽 방법을 이용하여 순수 분리 정제하였다. 효소는 분자량 34kDa을 가진 monomeric 단백질이며 substrate specificity. 분자량, 최적 pH, 아미노산 조성 등을 다른 sources의 효소들과 비교하였다. 이 비교 결과들로부터 본 연구에서 정제한 효소는 다른 sources와 다른 효소로 밝혀졌다. 반응의 산물이나 유사 기질 등을 저해제로 사용하였을때의 반응기작은 intermediate ternary complex를 형성하고 NADPH가 먼저 효소에 binding하는 ordered Sequencial mechanism을 보인다는 사실을 관찰할 수 있었다.

• Korean Journal of Microbiology
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• v.32 no.3
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• pp.222-231
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• 1994

Kinetic analysis was done to elucidate the reaction mechanism of purine nucleoside phosphorylase (PNP) in Saccharomyces cerevisiae. The binary complexes of PNP${\cdot}$phosphate and PNP${\cdot}$ribose 1-phosphate were involved in the reaction mechanism. The initial velocity and product inhibition studies demonstrated were consistent with the predominant mechanism of the reaction being an ordered bi, bi reaction. The phosphate bound to the enzyme first, followed by nucleoside and base were the first product to leave, followed by ribose 1-phosphate. The kinetically suggested mechanism of PNP in S. cerevisiae was in agreement with the results of protection studies against the inactivation of the enzyme by sulfhydryl reagents, p-chloromercuribenzoate (PCMB) and 5,5'-dithiobisnitrobenzoate (DTNB). PNP was protected by ribose 1-phosphate and phosphate, but not by nucleoside or base, supporting the reaction order of ordered bi, bi mechanism. PCMB or DTNB-inactivated PNP was totally reactivated by dithiothreitol (DTT) and the activity was returned to the level of 77% by 2-mercaptoethanol, indicating that inactivation was reversible. The kinetic behavior of the PCMB-inactivated enzyme had been changed with higher $K_m$ value of inosine and lower $V_m$, and was restored by DTT. Inactivation of enzyme by DTNB showed similar pattern of K sub(m) value with that by PCMB, but had not changed the $V_m$ value, significantly. Negative cooperativity was not found with PCMB or DTNB treated PNP at high concentration of phosphate.

• Applied Biological Chemistry
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• v.37 no.3
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• pp.210-215
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• 1994

${\underline{O}},{\underline{O}}-Diethyl-{\underline{S}}-phenyl\;phosphorothiolate-^{18}O$ and other related compounds were prepared and oxidized with m-chloroperbenzoic acid (MCPBA). Each reaction was followed by $^{31}P$ NMR and the products were analyzed by GC-MS. ${\underline{O}},{\underline{O}}-Diethyl-{\underline{S}}-phenyl\;phosphorothiolate-^{18}O$ was converted to diethyl methyl phosphate in methanol by MCPBA and it was confirmed to contain $^{18}O$, which proved that the originally proposed mechanism of Segall and Casida operates in the oxidative reaction.

• Journal of Life Science
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• v.31 no.8
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• pp.771-777
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• 2021

Human endogenous retroviruses (HERVs) were inserted into the human genome millions of years ago but they are currently inactive and non-infectious due to recombinations, deletions, and mutations after insertion into the host genome. Nonetheless, recent studies have shown that HERV-derived elements are actually involved in physiological phenomena and certain diseases including cancers. Among the various physiological phenomena related to HERV-derived elements, it is necessary to focus on inflammatory response. HERV-derived elements have been reported to be directly involved in various inflammatory diseases, including autoimmune diseases such as rheumatoid arthritis, multiple sclerosis, amyotrophic lateral sclerosis, and Sjogren's syndrome. As a mechanism for regulating inflammation through HERV-derived elements, the possibility that HERV-derived elements may cause nonspecific innate immune processes and that HERV-derived RNA or proteins may cause selective signaling mechanisms through specific receptors can be considered. However, the mechanism through which HERV-derived elements regulate inflammatory response, such as how silent HERV elements are activated in inflammatory response and what factors and signaling mechanisms are involved in HERV-derived elements, have not been identified to date, making it difficult to study the onset of HERV-related inflammatory disease. In this review, we introduce HERV-related autoimmune diseases and propose the mechanisms of HERV-derived elements at the molecular level of HERV in inflammatory response.

• KSBB Journal
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• v.9 no.1
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• pp.1-7
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• 1994

A qualitative study was made on the mechanism of dextran synthesis by dextransucrase. Enzymatic synthesis of dextran was experimentally studied with initial sucrose concentration from 50g/$\ell$ to 150g/$\ell$. The molecular weight distribution of synthesized dextran was measured by using on-line gel Permeation chromatographic system Sucrose was observed not to work as a primer within the range of concentration tested. At the initial sucrose concentration of 50g/$\ell$, dextran with molecular weight of medium range ($10^4-2{\times}10^6$) was synthesized due to the mass transfer limitation of sucrose. The amount of the dextran of medium range decreased with the initial sucrose concentration. Dextran was likely to be synthesized by radical chain polymerization mechanism since the dextran of medium range was not produced at higher sucrose concentrations.

• Korean Journal of Soil Science and Fertilizer
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• v.39 no.3
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• pp.157-162
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• 2006

Objective of this research was to evaluate optimal conditions of arsenic adsorption in water by zero-valent iron (ZVI). Batch experiment showed that adsorption of arsenic by ZVI followed a Langmuir isotherm model. The masses of As(V) adsorbed onto ZVI were increased as decreasing pH of the reacting solution (pH 3: 2.05, pH 5: 1.82, pH 7: 1.24, pH 9: 1.03 mg As/g $Fe^0$) and as increasing the temperature ($15^{\circ}C$ : 1.59, $25^{\circ}C$ : 1.81, 35 : $1.93^{\circ}C$ mg As/g $Fe^0$). The SEM and EDS (energy dispersive X-ray spectrometer) analysis of morphology and structure of ZVI before and after reacting with arsenic in water revealed that a relatively smooth and large surface of ZVI was transformed into a coarse and small surface particle after the reaction. The EDS spectra on the chemical composition of ZVI demonstrated that arsenic was incorporated into ZVI by adsorption mechanism. The XRD analysis also identified that the only peak for $Fe^0$ in the ZVI before the reaction and confirmed that $Fe^0$ was transformed into $Fe_2O_3$ and FeOOH, and As into $FeAsO_4{\cdot}2H_2O$.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 1999.10a
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• pp.135-136
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• 1999

대기 침적은 대기중으로 방출된 오염물질의 제거기작으로 널리 알려져 있으며, 대기로부터 자연계의 표면에 침적되는 대기중의 유해물질들이 환경계에 미치는 영향과 그들의 이동을 조절하는 중요한 기작의 하나이다. 그러나 건식 침적의 경우 공간 및 시간적 변화가 크고 침적되는 표면과 대기 사이의 상호 반응이 침적되는 물질의 양에 커다란 영향을 미칠수 있기 때문에 그 측정이 상당히 어렵고 또한 시료 채취시 세심한 주의와 축적된 경험을 요구한다.(중략)

• Proceedings of the Korea Air Pollution Research Association Conference
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• 1999.10a
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• pp.191-193
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• 1999

닫힌 반응기 내부에 부유하는 에어로졸 입자들의 크기분포는 응집, 응축, 확산에 의한 침착, 중력침강 및 누출과 같은 여러 기작들에 의해 변화한다. 특히 확산 및 중력침강에 의해 일어나는 입자의 침착(deposition)은 에어로졸 측정기기의 오차분석, 호흡기내부의 미세입자 침착, 건물내부의 입자상 물질의 농도 및 크기분포 변화 등 여러 응용분야에 관련되는 중요한 기작이다.(중략)

• The Microorganisms and Industry
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• v.17 no.2
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• pp.2-10
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• 1991

식물체에서 일어나는 유전자 발현의 광조절 현상은 매우 복잡하다. 이는 각 유전자들이 조직에 따라 질적, 양적, 시간적 측면에서 빛에 대한 반응에 커다란 차이점을 보이고 있기 때문이다. 따라서 식물체를 대상으로 광조절 기작을 연구하는 데는 현상의 복합성과 실험과정의 기술적, 시간적, 경제적 제약이 많기 때문에 이에 관한 연구가 아직 초보적 수준에 머물고 있다. 광합성 세균 중에서 purple bacteria나 green bacteria와는 달리 식물성 광합성을 하며, 식물체보다 세포구조가 훨씬 간단한 cyanobacteria는 유전자 발현의 광조절 기작을 연구하는데 간단, 명료한 'model'로서 기대되는 바 크다. 따라서 이 글에서는 cyanobacteria의 광계와 광합성 색소인 chlorophyll의 생합성 과정을 중심으로 광조절 현상에 대한 최근 연구 동향과 전망을 살펴보고자 한다.