• Bulletin of the Korean Chemical Society
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• 제18권1호
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• pp.18-23
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• 1997

Data from structure/activity studies in vir gene induction system have led to evaluate the working hypothesis of interaction between phenolic inducers and phenol binding proteins. The primary specificity in the association of a phenolic inducer with its receptor in our system is hypothesized to be the hydrogen bonding interactions through the ortho methoxy substituents as well as the proton transfer between the inducer and the binding protein. In this paper the proposed working model for phenol-mediating signal transduction was evaluated in several ways. The importance of the general acid-base catalysis was first addressed by the presence of an acidic residue and a basic residue in the phenol binding protein. Series of compounds were tested for vir gene expression activity to confirm the generation of a strong nucleophile by an acidic residue and an involvement of a basic residue as a proton acceptor. An attempt was made to correlate the pKa values of the phenolic compounds with vir gene induction activities as inducers to further support the proposed proton transfer mechanism. Finally, it was also observed that the regioselectively attached methoxy group on phenol compounds is required as the proper hydrogen bond acceptor.

• Bulletin of the Korean Chemical Society
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• 제19권9호
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• pp.923-926
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• 1998

Spectral diffusion following direct triplet excitation from the ground state in glassy Methylbenzophenone as a function of transition energy has been studied. The concentrations of donor and acceptor have been determined for different transition energies. The geometrical distribution was determined by a computer simulation. The cluster size increases gradually with concentration and cluster percolation is observed at 0.31 mole fraction for a three dimensional system. The average distance between a donor and an acceptor also has been determined for different concentrations. The energy transfer efficiency changes abruptly at a critical concentration of 0.054, corresponding to a critical distance of 9.8 Å. The γvalue was evaluated to be 1.17.

• 대한화학회지
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• 제60권5호
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• pp.374-377
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• 2016

• 한국어업기술학회:학술대회논문집
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• 한국어업기술학회 1998년도 수산관련공동학술대회발표요지집
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• pp.302.2-303
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• 1998

• Bulletin of the Korean Chemical Society
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• 제22권3호
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• pp.257-258
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• 2001

• Bulletin of the Korean Chemical Society
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• 제27권9호
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• pp.1297-1304
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• 2006

A systematic study of the structure, energetics and spectral characteristics of substituted aminoketenes $R(NH_2)$C=C=O (R = H, $CH_3$, $NH_2$, OH, $OCH_3$, CH=$CH_2$, C$\equiv$CH, CN, CHO, NO, $NO_2$) which are highly reactive and transient intermediates in synthesis has been conducted by ab initio calculations at the MP2/6- 31G*//MP2/6-31G* level. Twenty four stable isomers of the eleven substituted aminoketenes having dihedral angles $\phi NH_2\sim120{^{\circ}}$ and $60^{\circ}$ have been identified and their optimized geometries and energies obtained. Electrostatic and steric effects on the molecular geometries have been analyzed. While the $\pi$-acceptor groups lead to planar conformations, the electron-donor groups give rise to non-planar conformations. Isodesmic substituent stabilization energies relative to alkenes have been calculated and correlation with group electronegativities established. Role of induction effect by the substituent groups and resonance effects in charge distribution in the molecules has been analyzed. An analysis of the asymmetric stretching frequencies and intensities of the C=C=O group shows that affect of non-$\pi$ acceptor substituents on the frequency is determined by the field effect (F) and resonance effect (R) parameters, the calculated intensities I (km/mol.) are correlated to group electronegativities $x$ of the substituents by the relationship I = 640.2–100.1 $x$ (r = 0.92). The $\pi$-acceptor substituents increase the intensity which may be explained in terms of their delocalizing effect on the negative charge at the $C_{\beta}$ atom.

• KSBB Journal
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• 제19권5호
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• pp.363-367
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• 2004

Leuconostoc mesenteroides NRRL B-1149 produces various glucoseyltransferases for the synthesis of dextran, levan and glucose-1-phosphate using sucrose as a substrate. A sucrose phosphorylase (1149SPase) was purified from L. mesenteroides NRRL B-1149 culture by using hollow fiber filtration (30 kDa cut off), Toyopearl DEAE 650 M column chromatography and following two times of DEAE-Sepharose column chromatographies. The specific activity of the purified 1149SPase was 25.7 (U/mg) with $16\%$ yield. The 1149SPase showed a molecular size of 56 kDa on denatured $10\%$ SDS-PAGE. The N-terminal amino acid sequence of the enzyme was MEIQNKAM. The optimum pH and temperature of this enzyme were 6.2~6.5 and 37^{circ}C, respectively. It had an apparent K_{m} of 6.0 mM and K_{cat} of 1.62/s for sucrose. 1149SPase crystal was formed by hanging drop diffusion technique using 20 mM calcium chloride dihydrate, 100 mM sodium acetate trihydrate pH 4.6 and $30\%$ 2-methyl-2,4-pentanediol as vaporizing and reservation solution. The 1149SPase catalyzes transferring of glucose from isomaltose or sucrose to salicin and salicyl alcohol by disproportionation reaction or acceptor reaction and synthesized two acceptor products, respectively.

• Journal of Microbiology and Biotechnology
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• 제17권3호
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• pp.428-437
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• 2007

The potential for humic substances to serve as terminal electron acceptors in microbial respiration and the effects of humic substances on microbial azoreduction were investigated. The dissimilatory azoreducing microorganism Shewanella decolorationis S12 was able to conserve energy to support growth from electron transport to humics coupled to the oxidation of various organic substances or $H_2$. Batch experiments suggested that when the concentration of anthraquinone-2-sulfonate (AQS), a humics analog, was lower than 3 mmol/l, azoreduction of strain S12 was accelerated under anaerobic condition. However, there was obvious inhibition to azoreduction when the concentration of the AQS was higher than 5 mmol/l. Another humics analog, anthraquinone-2-sulfonate (AQDS), could still prominently accelerate azoreduction, even when the concentration was up to 12 mmol/l, but the rate of acceleration gradually decreased with the increasing concentration of the AQDS. Toxic experiments revealed that AQS can inhibit growth of strain S12 if the concentration past a critical one, but AQDS had no effect on the metabolism and growth of strain S12 although the concentration was up to 20 mmol/l. These results demonstrated that a low concentration of humic substances not only could serve as the terminal electron acceptors for conserving energy for growth, but also act as redox mediator shuttling electrons for the anaerobic azoreduction by S. decolorationis S12. However, a high concentration of humic substances could inhibit the bacterial azoreduction, resulting on the one hand from the toxic effect on cell metabolism and growth, and on the other hand from competion with azo dyes for electrons as electron acceptor.

• Journal of Microbiology and Biotechnology
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• 제12권1호
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• pp.46-52
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• 2002

As a functional additive for intestinal microflora, panose ($6^2-{\alpha}$-D-glucopyranosylmaltose) was synthesized during kimchi fermentation using the glucose transferring reaction of glucansucrase from Leuconostoc mesenteroides. For the glucose transferring reaction, sucrose and maltose were added ($2\%$ each, w/v) to dongchimi-kimchi as the glucosyl donor and acceptor molecule, respectively. After five days of incubation at $10^{\circ}C$, referring to the initial phase for the production of lactic acid in kimchi, over $60\%$ (w/v) of the total sugars were converted into panose and other branched oligosaccharides. Thereafter, the kimchi was stored at $4^{\circ}C$ and the amount of panose remained at a constant level for three weeks, thereby indicating the stability of panose to microbial degradation during the period of kimchi consumption. The use of maltose as the acceptor molecule in the kimchi also facilitated a lower viscosity in the kimchi-juice by preventing the synthesis of a dextran-like polymer which caused an unfavorable taste. Accordingly, the application of this new method of simultaneous biocatalytic synthesis of oligosaccharides during lactate fermentation should facilitate the extensive development of new function-added lactate foods.

• 멤브레인
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• 제25권1호
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• pp.1-6
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• 2015

기존의 올레핀 운반체로 알려진 은 나노입자는 입자 표면에서 프로필렌 기체와 상호작용을 하여 올레핀 촉진수송이 이루어진다고 알려졌다. 그러나 은 나노입자가 공기 중에 쉽게 산화되어 표면에 생성된 산화은(AgO 또는 $Ag_2O$)의 효과일 것으로 예상되었다. 산화은의 효과를 규명하기 위해, 고분자 PVP에 AgO 또는 $Ag_2O$를 5 wt%로 넣고 분산시킨 후 전자수용체 TCNQ 또는 p-BQ를 0.005~0.02%까지 넣어 분리막을 제조하였다. 전자수용체가 첨가되면 산화은의 표면에 양극성화도 분산 정도가 향상될 것으로 기대하였고, 이는 기체투과 성능과 XPS 그리고 TEM에 의해 분리막의 특성이 확인되었다.