• Journal of the Korean Chemical Society
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• v.37 no.1
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• pp.105-111
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• 1993

The stability constants for lanthanides complexes with optically active L-proline (1 : 1) were determined in aqueous solution in the ionic medium of 0.1 M $NaClO_4$ at 25$^{\circ}C$ using a pH titration method. The results show called "gadolinium break" between lighter and heavier lanthanides. The linear relation between the stability constant (log$\beta$1) and the pKa values of ligands indicates that L-proline acts as a bidentate ligand in the complexation. The thermodynamic parameters (${\Delta}H$ and ${\Delta}S$) were also determined using an enthalpy titration method at the same condition. The positive endothermic enthalpy change and positive entropy change clearly indicate that the driving force for the complexation is an entropy effect. The comparison of the thermodynamic parameters of L-proline complexes with anthranilate complexes supports the conclusion that the heterocyclic nitrogen atom and carboxylate of L-proline are involved in the chleate formation. The enthalpy values for L-proline are more positive than the ones for anthranilate complex. The difference in enthalpy change for the complex formation between L-proline complex and anthranilate complex is explained in terms of the basicity of the nitrogen donor atom in the ligand. The relatively large entropy change may be described by the extra dehydration related to the rigidity of L-proline ring.

• Journal of the Korean Chemical Society
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• v.36 no.3
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• pp.446-452
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• 1992

The rates of hydrolysis of aryl phenylacetates have been measured in the presence of piperidine in 80% acetonitrile-20% water(v/v). For the electron withdrawing substituents of leaving group, the hydrolysis is catalyzed by a general base and the Hammett $\rho_{LG}$ and Bronsted value $\beta$ are 5.28 and -2.72 at $30^{\circ}C$, respectively. These high senstivities of Hammett and Bronsted values are $E1_{C}B$ mechanism. But in the electron donating ones, the hydrolysis is catalyzed by a specific base and $B_{AC}2 mechanism is predominated. $pK_{SH}'s of phenylacetic acid ester and rate constants of hydrolysis $k_1$, $k_{-1)$, $k_2$ were calculated.

• Analytical Science and Technology
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• v.8 no.1
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• pp.33-40
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• 1995

Only trace amounts of hydroxide ion can be extracted from aqueous phase into organic phase by Tetra-n-Butyl Ammonium Chloride(TBAC). Addition of small amounts of primary alcohols, particularly certain dials, dramatically changes the behavior of Phase Transfer Catalysis systems, and surprising amounts of base can be found in the organic phase. Quantitative measurements were carried out for the extraction amounts of primary alkoxides, secondary alkoxides, and diol anions into organic phase. On the other hand, the selectivity constants for extraction of primary alcohols and benzylalcohol could be separated to the equilibrium constants of the ion pairs such as $Q^+RO^-$ and $Q^+Cl^-$ in the aqueous and organic phases and this distribution coefficients between phases on anions respectively. In a word, the colligated property for the selectivity of $Q^+RO^-$ in which $Q^+$ is quaternary cation and $RO^-$ alkoxide ion could be discussed in more detail by using of the corresponding free energies to the various constants mentioned.

• Applied Chemistry for Engineering
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• v.25 no.2
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• pp.167-173
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• 2014

The adsorption characteristics of the pellet-type adsorbent prepared from water treatment sludge for trimethylamine and ammonia were studied. The surface area and pore volume of the pellet-type adsorbent increased during calcination at $500^{\circ}C$. It was confirmed that the adsorbent prepared from water treatment sludge contained Br$\ddot{o}$nsted and Lewis acid sites. The breakthrough time of the adsorbent for both trimethylamine and ammonia was measured at different adsorbent weights and linear velocities while maintaining constant amounts of trimethylamine and ammonia. The kinetic saturation capacity and the adsorption rate constant for trimethylamine and ammonia were determined at different linear velocities by using the Wheeler equation. It was found that the kinetic saturation capacity and the adsorption rate constant were dependent on the linear velocity. An experimental equation could be derived to predict the breakthrough time of the adsorbent prepared from water treatment sludge for trimethylamine and ammonia at different adsorption conditions.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.377-380
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• 2003

An Analytic breakdown voltage model of LDMOS with internal field ring is proposed. The model is a simple analytic formula which has variables such as the dimension of drift retion, the position and doping concentration of the internal field ring, the thickness and permittivity of oxide. By comparing the results from two dimensional TCAD simulation, the proposed model explains the breakdown phenomena fairly well.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04b
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• pp.160-162
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• 2002

SNP는 개인과 개인간의 DNA에 존재하는 한 염기 쌍의 차이(single base-pair variation)이다. SNP를 이용하면 사람마다 다른 유전병의 형태 등을 규명할 수 있다. 본 논문에서는 한국생명공학연구원의 유전체 사업단에서 개발해 오고 있는 웹기반 SNP데이터 검색 시스템의 설계와 구현에 대해서 설명한다. 본 시스템은 일반 속성(attribute)을 저장하고 검색하기 위해 PostgreSQL DBMS를 사용하고, DNA 시퀸스 검색을 위해 BLAST검색엔진을 사용한 약결합 아키텍쳐(loosely-coupled architecture)를 채택하고 있다. 즉, 일반 속성으로 저장될 수 있는 데이터들은 데이터베이스의 테이블들의 컬럼 값으로 저장하고 SQL 언어를 통해 검색할 수 있도록 하였으며, DNA 시퀸스 검색을 위해서는 BLAST에서 제공하는 인덱스를 구축하고 BLAST 명령어를 사용하여 검색할 수 있도록 하였다. 또한, 결과 분석 모듈을 구현하여 검색 결과들이 다른 웹 사이트의 데이터를 가리키도록 하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10a
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• pp.43-45
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• 2001

NCBI 의 GenBank 데이터베이스는 전세계에서 수집된 염기 서열 데이터들의 집합이며, 그 중 특허로 등록되어 있는 데이터들을 GenBank 특허 데이터라 부른다. 본 논문에서는 한국생명공학연구원의 유전체 사업단에서 개발해 오고 있는 웹기반 GenBank 특허 데이터 검색 시스템의 설계와 구현에 대해서 설명한다. 본 시스템은 일반 속성(attribute)을 저장하고 검색하기 위해 DBMS 를 사용하고, DNA 시퀸스 검색을 위해 BLAST를 사용한 약결합 아키텍쳐(loosely-coupled architecture)를 채택하고 있다. 즉, 일반 속성으로 저장될 수 있는 데이터들은 데이터베이스의 테이블들의 컬럼 값으로 저장하고 SQL 언어를 통해 검색할 수 있도록 하였으며, DNA 시퀸스 검색을 위해서는 BLAST 에서 제공하는 인덱스를 구축하고 BLAST 명령어를 사용하여 검색할 수 있도록 하였다. 또한, 검색 결과들이 기존의 외부 특허 시스템과 연동하도록 하기 위해, 결과 분석 모듈을 구현하여 검색 결과들이 다른 웹 사이트의 데이터를 가리키도록 하였다. 마지막으로, 이러한 DNA 검색 시스템을 구현할 때에 고려해 되야 되는 이슈들을 설명한다.

• Journal of the Korean Chemical Society
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• v.55 no.3
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• pp.346-353
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• 2011

Base hydrolysis of 7-hydroxy-2H-chromen-2-one (HC) and 7-hydroxy-2H-chromen-2-one-4-acetic acid (HCA) in aqueous-methanol and aqueous-acetone mixtures were studied kinetically at temperature range from 283 to 313 K. The activation parameters of the reactions were evaluated and discussed. Moreover, the change in the activation energy barrier of the investigated compounds from water to water-methanol and water-acetone mixtures was estimated from the kinetic data. It is observed that the change in activation barriers is more or less the same for the hydrolysis of HC and HCA. Base hydrolysis of HC and HCA follows a rate law with $k_{obs}=k_2[OH^-]$. The decrease in the rate constants of HC and HCA as the proportion of methanol or acetone increases is due to the destabilization of $OH^-$ ion. The high negative values of entropy of activation support the proposal mechanism, i.e. the investigated reaction takes place via the formation of an intermediate complex. Moreover, these values refer to the rigidity and stability of the intermediate complex. Thus, the ring opening of the intermediate complex would be the rate controlling step.

• Journal of Food Hygiene and Safety
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• v.15 no.2
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• pp.144-150
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• 2000

The present study was peformed to determine the hydrolysis rate constants and degradation products of phosphamidon and proffnofos by the OECD method. Hydrolysis rate constants of phosphamidon in pH 4, pH 7, and pH 9 buffer solutions at 25 and 40$^{\circ}$C were 0.0020, 0.0022, 0.0049 and 0.0040, 0.0050, 0.0150, respectively. Hydrolysis rate of phosphamidon was accelerated by temprerature change under same pH conditions, and half-life of phosphamidon in pH 9 at 40。C was 3 times faster than that at 25。C. Hydrolysis rate of phosphamidon in alkaline solution(pH 9) was 2~4 times faster than that in acidic solution(pH 4) and neutral solution(pH 7) under same temperature. Hydrolysis rate constants of profenofos in pH 4, pH 7, and pH 9 buffer solutions at 25 and 40。C were 0.0022, 0.0047, 0.0860 and 0.0035, 0.0086, 0.1245, respectively. Hydrolysis rate of profenofos was accelerated by temprerature change under same pH conditions. Hydrolysis rate of profenofos in alkaline solution(pH 9) was 15~40 times faster than in acidic solution(pH 4) and neutral solution(pH 7) under same temperature condition, and half-life of profenofos was very fast within 8 hours. The hydrolysis rate of profenofos was faster than that of phosphamidon. In order to identify hydrolysis products, the extracts of degradation products were analyzed by GC/MS. The mass spectra of hydrolysis products of phosphamidon were at m/z 153 and 149, those of the profenofos were at m/z 208 and 240, respectively. The hydrolysis products of phosphamidon were O, O-dimethyl phosphate(DMP) and N, N-diethylchloroacetamide, and those of profenofos were 4-bromo-2-chlorophenol and O-ethyl-S-propyl phosphate.

• Journal of the Korean Chemical Society
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• v.54 no.5
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• pp.515-522
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• 2010

A relation between antimicrobial activities and the formation constants of solid complexes of Cu(II), Ni(II), Co(II), Mn(II) and Fe(III) with tridentate Schiff base ligand, 4-hydroxy-3(1-{2-(benzylideneamino)-phenylimino}-ethyl)-6-methyl-2Hpyran-2-one (HL) derived from o-phenylene diamines, dehydroacetic acid (DHA) and p-chloro benzaldehyde have been studied. The ligand and metal complexes were characterized by elemental analysis, conductivity, magnetic susceptibility, thermal analysis, X-ray diffraction, IR, $^1H$-NMR, UV-vis and mass spectra. From the analytical data, the stiochiometry of the complexes was found to be 1:2 (metal:ligand) with octahedral geometry. The molar conductance values suggest the nonelectrolytic nature of metal complexes. The X-ray diffraction data suggests monoclinic crystal system for Ni(II) and orthorhombic crystal system for Cu(II) and Co(II) complexes. The IR spectral data suggest that the ligand behaves as tridentate ligand with ONN donor atoms sequence towards central metal ion. Thermal behavior (TG/DTA) and kinetic parameters calculated by Coats-Redfern method suggests more ordered activated state in complex formation. The protonation constants of the complexes were determined potentiometrically in THF:water (60:40) medium at $25^{\circ}C$ and ionic strength ${\mu}=0.1\;M$ ($NaClO_4$). Antibacterial activities in vitro were performed against Staphylococcus aureu and Escherichia coli. Antifungal activities were studied against Aspergillus Niger and Trichoderma. The effect of the metal ions and stabilities of complexes on antimicrobial activities are discussed.