• 한국미생물생명공학회:학술대회논문집
• /
• 한국미생물생명공학회 2001년도 Proceedings of 2001 International Symposium
• /
• pp.179-182
• /
• 2001

Two intracellular enzymes, cellobiose phosphorylase (CBP) and cellodextrin phosphorylase (CDP) are involved in the phosphorolytic pathway in cellulose degradation. Those enzymes are considered to be useful in syntheses of oligosaccharides because the reactions are reversible. CBP from Cellvibrio gilvus and CDP from Clostridium thermocellum YM-4 were cloned and over-expressed in Escharichia coli. Both the enzyme reactions showed ordered bi bi mechanism. Acceptor specificity of CBP in the reverse reaction was determined. Several $\beta$-l,4-glucosyl disaccharides were synthesized by using the reaction. A new substrate inhibition pattern, competitive substrate inhibition, was also found in the reverse reaction of CBP Cellobiose was produced from sucrose at a high yield by a combined action of three enzymes including CBP

• Archives of Pharmacal Research
• /
• 제23권3호
• /
• pp.202-205
• /
• 2000

A convenient pathway for synthesis of trans-metanicotine analogues was developed. trans-Metanicotine, a subtype(${\alpha}4{\beta}2$)-selective ligand for neuronal nicotinic acetylcholine receptor, is under clinical phase for Alzheimer's disease. Zn-mediated allylation of allyl bromide and acetaldehyde followed by Heck reaction with 3-bromopyridine gave 5-pyridin-3-yl-pent-4-en-3-ol (2). Tosylation of 5-pyridin-3-yl-pent-4-en-3-ol followed by substitution reaction with methylamine in sealed tube gave methyl-(1-methyl-4-pyridin-3-yl-but-3-enyl)-amine (4) in good yields. Thus, trans-metanicotine analogues modified at the $\alpha$-position of the methylamino group with various functional groups can be obtained in 4 steps.

• Bulletin of the Korean Chemical Society
• /
• 제16권4호
• /
• pp.310-315
• /
• 1995

The heterobimetallic anion, (OC)5CrMn(CO)5-M+ (M+=Na+, PPN+), which has a donor-acceptor metal-metal bond1, was reacted with allyl bromide to yield BrCr(CO)5- and Mn(CO)5(CH2CHCH2). The reaction mechanism has been proposed in terms of the consecutive reaction pathway in which Cr(CO)5(THF) is an important intermediate leading to the corresponding product. Counterion effect on this reaction was also evaluated and the results were compared with those of the corresponding reaction of the mononuclear carbonyl anion, Mn(CO)5-.

• Bulletin of the Korean Chemical Society
• /
• 제28권12호
• /
• pp.2324-2328
• /
• 2007

Organic fluorine chemistry produces many useful products. This paper elucidates the reaction of ethyl-4,4- difluoro-2-iodo-5-oxo-5-phenylpentanoate (2) with primary amines in a one-pot scheme. The reaction produced a series of β-fluoropyrrole derivatives at ambient temperatures. In this reaction, the less bulky the primary amine the higher was the resultant yield. When (2) and aqueous methylamine (40%) were allowed to react below 0 oC, 5-(ethoxycarboxyl)-1-methyl-3,3-difluoro-2-hydroxy-2-phenylpyrrolidine, an intermediate molecule for 2-ethyl-4-flouro-1-methyl-5-phenylpyrrole-2-carboxylate (5), was isolated first. Then, (5) reacted with hydroperchloric acid and acetic anhydride to form 5-(ethoxycarboxyl)-1-methyl-3,3-difluoro-2- phenylpyrrolinium perchlorate (6), which was converted to 2-ethyl-4-flouro-1-methyl-5-phenylpyrrole-2- carboxylate gradually in the presence of a base. Our experiments demonstrate that the formation of 2-ethyl-4- flouro-1-methyl-5-phenylpyrrole-2-carboxylate occurs via both one-pot schemes and stepwise pathways, depending on the reaction conditions. The isolation and characterization of the isolated intermediate (6) suggest an anionic pathway for this reaction.

• Biotechnology and Bioprocess Engineering:BBE
• /
• 제9권6호
• /
• pp.506-513
• /
• 2004

Spirulina produces $\gamma$-linolenic acid (GLA), an important pharmaceutical substance, in a relatively low level compared with fungi and plants, prompting more research to improve its GLA yield. In this study, metabolic flux analysis was applied to determine the cellular metabolic flux distributions in the GLA synthetic pathways of two Spiru/ina strains, wild type BP and a high­GLA producing mutant Z19/2. Simplified pathways involving the GLA synthesis of S. platensis formulated comprise of photosynthesis, gluconeogenesis, the pentose phosphate pathway, the anaplerotic pathway, the tricarboxylic cycle, the GLA synthesis pathway, and the biomass syn­thesis pathway. A stoichiometric model reflecting these pathways contains 17 intermediates and 22 reactions. Three fluxes - the bicarbonate (C-source) uptake rate, the specific growth rate, and the GLA synthesis rate - were measured and the remaining fluxes were calculated using lin­ear optimization. The calculation showed that the flux through the reaction converting acetyl­CoA into malonyl-CoA in the mutant strain was nearly three times higher than that in the wild­type strain. This finding implies that this reaction is rate controlling. This suggestion was sup­ported by experiments, in which the stimulating factors for this reaction $(NADPH\;and\;MgCl_{2})$ were added into the culture medium, resulting in an increased GLA-synthesis rate in the wild type strain.

• Bulletin of the Korean Chemical Society
• /
• 제23권2호
• /
• pp.205-214
• /
• 2002

The reaction of gas-phase atomic hydrogen with hydrogen atoms chemisorbed on a silicon surface is studied by use of the classical trajectory approach. Especially, we have focused on the mechanism changes with the hydrogen surface coverage difference. On the sparsely covered surface, the gas atom interacts with the preadsorbed hydrogen atom and adjacent bare surface sites. In this case, it is shown that the chemisorption of H(g) is of major importance. Nearly all of the chemisorption events accompany the desorption of H(ad), i.e., adisplacement reaction. Although much less important than the displacement reaction, the formation of $H_2(g)$ is the second most significant reaction pathway. At gas temperature of 1800 K and surface temperature of 300 K, the probabilities of these two reactions are 0.750 and 0.065, respectively. The adsorption of H(g) without dissociating H(ad) is found to be negligible. In the reaction pathway forming $H_2$, most of the reaction energy is carried by $H_2(g)$. Although the majority of $H_2(g)$ molecules are produced in sub-picosecond, direct-mode collisions, there is a small amount of $H_2(g)$ produced in multiple impact collisions, which is characteristic of complex-mode collisions. On the fully covered surface, it has been shown that the formation of $H_2(g)$ is of major importance. All reactive events occur on a subpicosecond scale, following the Eley-Rideal mechanism. At gas temperature of 1800 K and surface temperature of 300 K, the probability of the $H_2(g)$ formation reaction is 0.082. In this case, neither the gas atom trapping nor the displacement reaction has been found.

• 대한화학회지
• /
• 제62권5호
• /
• pp.344-351
• /
• 2018

이 연구에서는 기체 상태 페난트렌, 페난트렌올, 페난트레닐 라디칼, 하이드록실 페난트렌 라디칼에 대한 IR 스펙트럼을 BLYP/6-311++G(d,p)법을 사용하여 얻었다. 이 스펙트럼들을 비교함으로써 ${\cdot}OH$에 의한 페난트렌의 분해 반응 경로를 동정하는데 IR 스펙트럼 측정이 유용하게 사용될 수 있음을 볼 수 있었다. IR 스펙트럼에서 H 원자 제거 과정은 CH의 out-of-plane 굽힘 진동 영역인 $650{\sim}850cm^{-1}$, ${\cdot}OH$ 첨가 과정은 CH 신축 및 굽힘 진동 영역에서 용이하게 확인 할 수 있음을 알 수 있었다. 또한 5종의 페난트렌-n-올 (n = 1, 2, 3, 4, 9) 모두에 대하여 얻어진 IR 스펙트럼 역시 여기에 주어졌다.

• 해양환경안전학회지
• /
• 제23권6호
• /
• pp.661-668
• /
• 2017

본 연구의 목적은 혼산 화물의 폭발사고에 대한 화학반응 경로를 분석하는데 있다. 분석에는 사건-가지분석기법을 적용한 구조적인 시나리오를 이용하였다. 구조적인 시나리오는 재결서에 기록된 혼산 화물 사고의 내용에서 다양한 화학반응 경로를 추정하여 구축하였다. 분석에는 화학 이론에 의거한 정성적 분석과 화학 반응식을 이용한 정량적 분석 및 설문조사를 통한 확률적 분석 등 세 가지 방법을 혼합 적용하였다. 분석결과, 사고 발생의 주요 경로는 진한 황산과 물이 반응하여 폭발하는 경로, 혼산과 금속이 반응하여 폭발하는 경로, 특수한 물질과 합성하여 폭발하는 경로 등 세 가지로 나타났다. 이 결과는 재결서에 기록된 경로와 유사함을 알았고, 이를 통해서 본 연구에서 제안한 화학물질의 경로분석 기법이 타당함을 알았다. 본 연구에서 제안한 방법은 다양한 화학물질 사고의 화학반응 경로 추정에 적용 가능할 것으로 기대된다.

• 농촌계획
• /
• 제15권1호
• /
• pp.73-87
• /
• 2009

This study analyzed the characteristics of diverse information adoption pathways per pathway of information composition category including 'information perception', 'information assessment', and 'information adoption' and examined information adoption characteristics per pattern. In addition, differences among agricultural researchers and farmers per information adoption stage were analyzed. According to these analyses, as for farmers' information adoption pathways, while the formal extension type and the situational reaction diffusion type used the direct pathway of 'information perception ${\rightarrow}$ information adoption,'the agriculturist connection type and the systematic approach type did not use the direct pathway of 'information perception ${\rightarrow}$ information adoption' but, instead, adopted information by moving from the 'information perception ${\rightarrow}$ information assessment' pathway to the 'information assessment ${\rightarrow}$ information adoption' pathway, with information assessment as the intermediation. In the case of farmers, information adoption was the highest in comparison with information assessment and information perception in all patterns whereas, in the case of agricultural researchers, the results were exactly opposite those of farmers. By suggesting an information adoption pathway appropriate to each pattern, this study sought to enhance information adoption.

• 한국생물공학회:학술대회논문집
• /
• 한국생물공학회 2001년도 추계학술발표대회
• /
• pp.70-73
• /
• 2001

Isopentenyl diphosphate (IPP) is the common, five-carbon building block in the biosynthesis of all isoprenoids. IPP in Escherichia coli is synthesized through the non-mevalonate pathway. The first reaction of IPP biosynthesis in E. coli is the formation of 1-deoxy-D-xylulose-5-phosphate(DXP), catalyzed by DXP synthase and encoded by dxs. The second reaction in the pathway is the reduction of DXP to 2-C-methyl-D-erythritol-4-phosphate, catalyzed by DXP reductoismerase and encoded by dxr. To determine if one of more of the reactions in the non-mevalonate pathway controlled flux to IPP, dxs and dxr were placed on several expression vectors under the control of three different promoters and transformed into three E. coli strains ($DH5{\alpha}$, XL1-Blue, and JM101) that had been engineered to produce lycopene, a kind of isoprenoids. Lycopene production was improved significantly in strains transformed with the dex expression vectors. At arabinose concentrations between 0 and 1.33 mM, cells expressiong both dxs and from $P_{BAD}$ on a midium-copy plasmid produced 1.4 -2.0 times more lycopene than cells expressing dxs only. However, at higher arabinose concentrations lycopene production in cell expressing both dxs and dxr was lower than in cells expression dxs only. A comparison of the three E. coli strains trasfomed with the arabinose-inducible dxs on a medium-copy plasmid revealed that lycopene production was highest in XL1-Blue.