• Bulletin of the Korean Chemical Society
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• 제11권6호
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• pp.557-560
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• 1990

The transition from one stable steady state branch to another stable steady state branch in a simple metabolic system with positive feedback is discussed with the aid of the bimodal Gaussian probability distribution method. Fluctuations lead to transitions from one stable steady state branch to the other, so that the bimodal Gaussian evolves to a new distribution. We also obtain the fractional occupancies in the two stable steady states in terms of a parameter characterizing conditions of the system.

• Bulletin of the Korean Chemical Society
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• 제9권4호
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• pp.236-240
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• 1988

A thioamide, N-5-trifluoromethyl-6-methoxy-1-thionaphthoyl-N-m ethylglycine, undergoes trans${\rightleftharpoons}$cis photoisomerization around C-N bound in solution. Azulene quenching studies showed the photoisomerization to proceed via both singlet and triplet excited states.The total quantum yield of the trans${\rightarrow}$cis photoisomerization is about 0.26, 0.14 from the singlet excited state and 0.12 from the triplet excited state. Intersystem crossing and internal conversion quantum yields were calculated from sensitized photostationary state and a plausible mechanism is proposed.

• 대한화학회지
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• 제68권1호
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• pp.20-24
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• 2024

This article presents the advantages of utilizing gossypol and its derivatives as reagents for iron (III) (Fe (III)) ions. A novel spectrophotometric method has been developed for the determination of Fe (III) using gossypol derivatives in the presence of a universal buffer solution. Optimal conditions have been identified, and the composition and stability constants of the Fe (III) complex with gossypolacetic acid have been determined.

• Journal of Microbiology and Biotechnology
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• 제24권12호
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• pp.1664-1672
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• 2014

In this study, a fibrous bed bioreactor (FBB) was used for $\small{D}$-lactic acid ($\small{D}$-LA) production by Sporolactobacillus inulinus Y2-8. Corn flour hydrolyzed with ${\alpha}$-amylase and saccharifying enzyme was used as a cost-efficient and nutrient-rich substrate for $\small{D}$-LA production. A maximal starch conversion rate of 93.78% was obtained. The optimum pH for $\small{D}$-LA production was determined to be 6.5. Ammonia water was determined to be an ideal neutralizing agent, which improved the $\small{D}$-LA production and purification processes. Batch fermentation and fed-batch fermentation, with both free cells and immobilized cells, were compared to highlight the advantages of FBB fermentation. In batch mode, the $\small{D}$-LA production rate of FBB fermentation was 1.62 g/l/h, which was 37.29% higher than that of free-cell fermentation, and the $\small{D}$-LA optical purities of the two fermentation methods were above 99.00%. In fe$\small{D}$-batch mode, the maximum $\small{D}$-LA concentration attained by FBB fermentation was 218.8 g/l, which was 37.67% higher than that of free-cell fermentation. Repeate$\small{D}$-batch fermentation was performed to determine the long-term performance of the FBB system, and the data indicated that the average $\small{D}$-LA production rate was 1.62 g/l/h and the average yield was 0.98 g/g. Thus, hydrolyzed corn flour fermented by S. inulinus Y2-8 in a FBB may be used for improving $\small{D}$-LA fermentation by using ammonia water as the neutralizing agent.

• Korean Chemical Engineering Research
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• 제53권2호
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• pp.193-198
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• 2015

Polycaprolactone, Dichloromethane, 이산화탄소로 구성된 3성분계 고압 시스템의 상거동 측정 실험은 가변 부피 셀 장치를 이용해서 측정했다. 실험의 온도범위는 313.15 K에서 353.15 K, 압력은 약 300 bar까지 측정했으며 실험결과는 Polycaprolactone의 질량 분율이 1.0%, 2.0%, 3.0%일 때 온도와 이산화탄소/Dichloromethane의 질량 분율로 정리했다. 또한 실험 결과는 hybrid 상태방정식 (Peng-Robinson 상태방정식과 SAFT 상태방정식의 혼합형태) 을 이용하여 열역학적으로 검증하였으며, 혼합규칙은 반데르 발스의 단일 유체 혼합규칙을 사용했다. 이 다성분계 시스템에서 이원 상호 작용 파라미터 등, 각종 파라미터는 심플렉스 알고리즘을 통해 최적화했다.

• Korean Journal of Chemical Engineering
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• 제35권11호
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• pp.2172-2184
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• 2018

The production of isophthalic acid (IPA) from the oxidation of m-xylene (MX) by air is catalyzed by $H_3PW_{12}O_{40}$ (HPW) loaded on carbon and cobalt. We used $H_2O_2$ solution to oxidize the carbon to improve the catalytic activity of HPW@C catalyst. Experiments reveal that the best carbon sample is obtained by calcining the carbon at $700^{\circ}C$ for 4 h after being impregnated in the 3.75% $H_2O_2$ solution at $40^{\circ}C$ for 7 h. The surface characterization displays that the $H_2O_2$ modification leads to an increase in the acidic groups and a reduction in the basic groups on the carbon surface. The catalytic capability of the HPW@C catalyst depends on its surface chemical characteristics and physical property. The acidic groups play a more important part than the physical property. The MX conversion after 180 min reaction acquired by the HPW@C catalysts prepared from the activated carbon modified in the best condition is 3.81% over that obtained by the HPW@C catalysts prepared from the original carbon. The IPA produced by the former is 46.2% over that produced by the latter.

• Bulletin of the Korean Chemical Society
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• 제27권3호
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• pp.386-388
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• 2006

Membrane proteins in highly oriented lipid bilayer samples are useful for membrane protein structure determination. We used in the past planar lipid bilayers which were aligned and supported on the glass slide. These samples were mechanically aligned in a magnetic field. However, these stacks of glass slides with planar lipid bilayers are not well suited for use with a commercial solid-state NMR probe with a round coil. Therefore, a homebuilt solid-state NMR probe was built and used with a stack of thin glass plates wherein the RF coil was wrapped directly around the flat square sample. Recently, we began to use magnetically aligned bicelles that are suitable for the structure determination of membrane proteins by solid-state NMR spectroscopy without any effort to build a flat square coil probe. These bicelle samples are well suited for use with a commercial solidstate NMR probe with a round coil, are very easy to prepare and are very stable, so that they can be kept for more than a year. In this paper, we present the solid-state NMR spectra of optimized and magnetically oriented bicelle samples of membrane proteins.

• Bulletin of the Korean Chemical Society
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• 제34권7호
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• pp.1961-1966
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• 2013

Theoretical investigations have been performed for the ground state ($S_0$) and the first excited state ($S_1$) of the hydrogen bonded green fluorescent protein (GFP) model. The potential energy surface (PESs) of $S_0$ was obtained by B3LYP method and that of $S_1$ was obtained by CIS method. Based on the relative stabilities of species and the energy barriers for the proton transfer, it was found that proton transfer could take place both under the ground state and the first excited state. As determined by the proton motions along the reaction coordinate, both the ground state proton transfer (GSPT) and the excited state proton transfer (ESPT) are considered as a concerted and asynchronous process.

• Bulletin of the Korean Chemical Society
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• 제31권11호
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• pp.3301-3303
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• 2010

Two new diterpenoid alkaloids, N(19)-en-denudatine (1) and N(4)-butanone-flavaconitine (2), were isolated from Aconitum brachypodum Diels.. Their structures were elucidated by comprehensive spectroscopic analyses including UV, IR, MS, 1D- and 2D-NMR.

• Bulletin of the Korean Chemical Society
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• 제25권8호
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• pp.1241-1243
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• 2004