• Bulletin of the Korean Chemical Society
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• 제29권6호
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• pp.1137-1140
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• 2008

M1 RNA, the catalytic subunit of Escherichia coli RNase P, is an essential ribozyme that processes the 5' leader sequence of tRNA precursors (ptRNAs). Using KS2003, an E. coli strain generating only low levels of M1 RNA, which showed growth defects, we examined whether M1 RNA is involved in polycistronic mRNA processing or degradation. Microarray analysis of total RNA from KS2003 revealed six polycistronic operon mRNAs (acpP-fabF, cysDNC, flgAMN, lepAB, phoPQ, and puuCBE) showing large differences in expression between the adjacent genes in the same mRNA transcript compared with the KS2001 wild type strain. Model substrates spanning an adjacent pair of genes for each polycistronic mRNA were tested for RNase P cleavage in vitro. Five model RNAs (cysNC, flgMN, lepAB, phoPQ, and puuBE) were cleaved by RNase P holoenzyme but not by M1 RNA alone. However, the cleavages occurred at non-ptRNA-like cleavage sites, with much less efficiency than the cleavage of ptRNA. Since cleavage products generated by RNase P from a polycistronic mRNA can have different in vivo stabilities, our results suggest that RNase P cleavage may lead to differential expression of each cistron.

• Bulletin of the Korean Chemical Society
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• 제17권4호
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• pp.353-357
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• 1996

Second-order rate constants have been measured spectrophotometrically for the reaction of 2,4-dinitrophenyl X-substituted benzenesulfonates with Z-substituted phenoxides in absolute ethanol at 25.0±0.1 ℃. The nucleophilic substitution reaction gives both S-O bond and C-O bond cleavage products. The extent of S-O bond cleavage increases significantly with increasing electron withdrawing ability of the sulfonyl substitutent X, while that of the C-O bond cleavage is independent on the electronic effect of the substituent. On the contratry, the effect of the substituent Z in the nucleophilic phenoxide is more significant for the C-O bond cleavage than for the S-O bond cleavage. Aminolyses of 2,4-dinitrophenyl benzenesulfonate (1) with various 1°, 2° and 3°amines have revealed that steric effect is little important. The extent of S-O bond cleavage increases with increasing the basicity of the amines, but decreases with increasing the basicity of the nucleophilic aryloxides, indicating that the HSAB principle is not always operative. Besides, reactant and solvent polarizability effect has also been found to be an important factor in some cases but not always to influence the reaction site.

• Bulletin of the Korean Chemical Society
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• 제15권9호
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• pp.729-732
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• 1994

The acid-promoted cleavage of the E-and Z-isomers of 1-phenyl-6-neopentyl-1,3,4-trimethyl-1-silacyclohe x-3-ene(II) under various conditions gave clean and nearly quantitative formation of the ring-opened 2,3,7,7-tetramethyl-5-(X)silyl-1-octene products (X=OMe, Cl, OH). The possible mechanism for the formation of the ring-opened products was suggested that the initial protonation of II at C-4 would give a carbocation oriented so that they are ${\beta}$ to the silicon atom, and the subsequent nucleophilic attack at silicon would give rise to the observed products (VI, VII, VIII).

• BMB Reports
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• 제46권4호
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• pp.225-229
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• 2013

Methylglyoxal (MG) is an endogenous metabolite which is present in increased concentrations in diabetics and reacts with amino acids to form advanced glycation end products. In this study, we investigated whether ferritin enhances DNA cleavage by the reaction of MG with lysine. When plasmid DNA was incubated with MG and lysine in the presence of ferritin, DNA strand breakage was increased in a dose-dependent manner. The ferritin/MG/lysine system-mediated DNA cleavage was significantly inhibited by reactive oxygen species (ROS) scavengers. These results indicated that ROS might participate in the ferritin/MG/lysine system-mediated DNA cleavage. Incubation of ferritin with MG and lysine resulted in a time-dependent release of iron ions from the protein molecules. Our data suggest that DNA cleavage caused by the ferritin/MG/lysine system via the generation of ROS by the Fenton-like reaction of free iron ions released from oxidatively damaged ferritin.

• 한국식품영양과학회지
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• 제33권5호
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• pp.847-851
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• 2004

미역의 부위별 fucoxantin함량은 미역엽 87.6 mg/100g, 미역줄기에 62.4 mg/100 g그리고 미역귀에 127.7 mg/100 g를 나타내어 미역귀에 함유되어 있는 fucoxanthin함량이 미역엽에 비해 1.4배, 미역줄기에 비해 2.0배 더 함유되어 있는 것으로 나타났다. Fucoxanthin은 444 nm에서 최대흡수극대를 나타내는 전형적인 carotenoids의 분광학적 특성을 나타냈다. 미역에 존재하는 fucoxanthin은 용매 분획, silica gel column chromatography와 HPLC를 이용하여 분리 정제하고, 얻어진 fucoxanthin을 인공생체막인 인지질에서의 자동산화에 이용하였다 인지질에서 50 $\mu$M fucoxanthin을 37$^{\circ}C$에서 72시간 자동산화시킨 결과, 5개의 산화물이 생성되었다. 이러한 산화물은 in uitro상의 산화적 조건하에서 fucoxanthin자동산화에 의해 생성된 산화개열산물로 생각되었다.

• 대한화학회지
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• 제32권1호
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• pp.71-78
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• 1988

20,21,24,25-Tetranitrodibenzo-18-crown-6에 알코올성 염기를 가하여 친핵성 치환반응을 유도하면 crown ether 화합물을 이루는 polyether 고리가 끊어져서 주생성물로 2,4,5-trialkoxynitrobenzene 유도체, 4,5-dialkoxy-1,2-dinitrobenzene 유도체 그리고 crown ether 고리가 부분적으로 끊어져 생긴 bis[(alkoxynitrophenoxy)ethyl]ether 유도체가 부생성물로 얻어졌다. 이가 알코올성 염기에서는 polyether 고리가 끊어진 생성물과 분자내 치환반응이 다시 진행되어 고리축소 현상이 일어나 12-crown-4의 유도체를 얻게 되거나 출발물질이 도로 생성되었다. 이상의 실험은 다양한 알코올의 농도에서 염기의 종류를 달리하여 그 선택성을 알아보았다.

• Journal of Forest and Environmental Science
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• 제6권1호
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• pp.45-60
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• 1989

리그닌 생분해의 분해경로 및 매카니즘에 관한 연구가 최근 Kirk와 Higuchi 등에 의하여 활발히 연구되고 있다. 특히, Phanerochaete chrysosporium이 생산해내는 Lignlnase를 이용하여 매우 가치있는 연구 결과를 얻고 있다. 본 총설에서는 Kirk와 Higuchi의 허가를 얻어서 그들의 논문을 중심으로 리그닌의 중요한 결합 양식 별로 즉, ${\beta}$-O-4, ${\beta}$-5, ${\beta}$-1, ${\beta}$-6, 5-5 등의 결합 모델 화합물들의 분해경로 및 매카니즘에 관하여 조사 정리하였다.

• Journal of the Korean Wood Science and Technology
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• 제45권2호
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• pp.168-181
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• 2017

Whole cell of Phanerochaete chrysosporium with reducing agent was applied to verify the degradation mechanism of aromatic compounds derived from lignin precisely. Unlike the free-reducing agent experiment, various degraded products of aromatic compounds were detected under the fungal treatment. Our results suggested that demethoxylation, $C_{\alpha}$ oxidation and ring cleavage of aromatic compounds occurred under the catabolic system of P. chrysosporium. After that, degraded products stimulated the primary metabolism of fungus, so succinic acid was ultimately main degradation product of lignin derived-aromatic compounds. Especially, hydroquinone was detected as final intermediate in the degradation of aromatics and production of succinic acid. In conclusions, P. chrysosporium has an unique catabolic metabolism related to the production of succinic acid from lignin derived-aromatic compounds, which was meaningful in terms of lignin valorization.

• Journal of the Korean Wood Science and Technology
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• 제31권3호
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• pp.11-16
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• 2003

On nitrobenzene oxidation of aspen, spruce, and knauf wood meals gave rise to vanilline, syrigaldehyde, p-hydroxybenzoaldehyde, vanillic acid, and other minor oxidation products. The phenolic aldehydes (p-hydroxybenzaldehyde, vanilline, and syringaldehyde) are derived from oxidative degradation of the corresponding 4-hydroxyphenylpropane units and their ethers. The lignin content of knauf wood meals was different as the concentration of NaOH solution and cooking temperature. The lignin contents of aspen, spruce, and knauf wood meals were decreased as laccase treatment. The laccase caused C-oxidation, demethylation, cleavage in phenolic groups and C-C cleavage in syrigyl structures.

• Journal of Photoscience
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• 제11권2호
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• pp.75-76
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• 2004

${\alpha}$,${\alpha}$-Dibromovalerophenone and ${\alpha}$,${\alpha}$-dichlorovalerophenone were prepared and their photochemical behaviors were investigated. The former gives C-Br cleavage products and the latter gives mainly the Yang photocyclization products upon irradiation. The reactivity of the chlorine substituted ketone turned out to be quite different from that of ${\alpha}$,${\alpha}$-difluorovalerophenone which gives both the cyclization and elimination products from the 1,4-biradical intermediate.