• Bulletin of the Korean Chemical Society
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• 제32권9호
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• pp.3411-3420
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• 2011

Kinetic and structural studies have been carried out on the effects of meso-tetrakis(4-sulfonatophenyl)-porphyrin ($H_2TPPS_4$) as an anionic and meso-tetrakis(3-N-methyl-pyridyl)porphyrin ($H_2TMPYP$) as a cationic porphyrin with adenosine deaminase (ADA) in 25 mM citrate/phosphate buffer, pH = 4-8, at $37^{\circ}C$ using UVvis spectrophotometry, circular dichroism (CD), fluorescence spectrophotometry as well as molecular dynamics (MD) and molecular docking. Kinetic results showed that the two porphyrins are non-competitive inhibitors. Increasing pH, increases $K_I$ and cationic porphyrin has a higher $K_I$ and lower binding constant ($K_b$) at all pH ranges. Analyzing the secondary structure revealed that both ligands decrease the secondary structure and that the anionic porphyrin is more effective.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1095-1096
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• 2006

When $Y_2O_3$ was added to Ti-excess $BaTiO_3$ ((Ba+Y)/Ti =1), the area occupied by $Y^{3+}$ ion was confirmed by its microstructure development, electrical conductivity behavior and lattice constant. Grain growth inhibition was observed when the content of donor dopant exceeded a critical value ($x{\approx}.0.01$) in $BaTiO_3+x(0.5Y_2O_3+TiO_2)$ system. A donor-doped behavior was observed at various Y contents ($0.2\sim3.0$ mol% Y) when $Y_2O_3$ was added to $TiO_2$-excess $BaTiO_3$. As Y content was increased, (002) and (200) peaks shifted to higher angles and the lattice constant (a and c axis) decreased gradually.

• Journal of Microbiology and Biotechnology
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• 제19권5호
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• pp.447-454
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• 2009

The transport of spermidine into a cyanobacterium, Synechocystis sp. pec 6803, was characterized by measuring the uptake of $^{14}C$-spermidine. Spermidine transport was shown to be saturable with an apparent affinity constant ($K_m$) value of $67{\mu}M$ and a maximal velocity ($V_{max}$) value of 0.45 nmol/min/mg protein. Spermidine uptake was pH-dependent with the pH optimum being 8.0. The competition experiment showed strong inhibition of spermidine uptake by putrescine and spermine, whereas amino acids were hardly inhibitory. The inhibition kinetics of spermidine transport by putrescine and spermine was found to be noncompetitive with $K_i$ values of 292 and $432{\mu}M$, respectively. The inhibition of spermidine transport by various metabolic inhibitors and ionophores suggests that spermidine uptake is energy-dependent. The diminution of cell growth was observed in cells grown at a high concentration of NaCl. Addition of a low concentration of spermidine at 0.5 mM relieved growth inhibition by salt stress. Upshift of the external osmolality generated by either NaCl or sorbitol caused an increased spermidine transport with about 30-40% increase at 10 mosmol/kg upshift.

• The Korean Journal of Physiology
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• 제11권1호
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• pp.1-9
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• 1977

Action of anthraquinone on the sodium plus potassium activated ATPase activity in the rabbit red cell membrane has been investigated and the experiments were also designed to determine the mechanism of action of anthraquinone on the ATPase activity. The following results were obtained 1. The activity of the NaK ATPase from red cell membrane is inhibited by anthraquinone and the concentration of anthraquinone for maximal inhibition is about 5mM. 2. The ratio of inhibition of NaK ATPase by anthraquinone, with a giving concentration of sodium in the medium, is increased by raising the potassium concentration. 3. The ratio of inhibition of NaK ATPase by anthraquinone, with a given concentration of potassium in the medium, is increased by raising the sodium concentration. 4. The action of anthraquinone on the NaK ATPase activity is inhibited by calcium ions and the ratio of inhibition is increased by small amounts of calcium but almost constant by larger amounts. 5. The inhibitory action of anthraquinone on the NaK ATPase activity was not related to the amino group of lysine, the hydroxyl group of threonine or the imidazole group of histidine. 6. The inhibitory action of anthraquinone on the ATPase activity is due to sulfhydryl group or the carboxyl group of the enzyme of NaK ATPase.

• Bulletin of the Korean Chemical Society
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• 제11권5호
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• pp.391-395
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• 1990

The kinetics of thermnal cis-trans isomerization reaction of 1-bromopropene(1-BP) was studied at temperatures from 620.8 to 753.15 K over the pressure range 0.17-50.3 Torr. Both the inhibition effect by cyclohexene or propene and the catalytic effect by HBr showed a radical process as the main mechanism of the isomerization. In the suppression of the radical process by the inhibitors, the molecular process also contributed to overall reaction rate. The reactions demonstrated the first order kinetics under both uninhibited and inhibited conditions and could be represented by the expressions (R = 1.987 cal/mol/K) $k_{un}/s^{-1} = (3.45{\pm}1.50){\times}10^{11}$exp$[(- 48100{\pm}2000)/RT]\;k_{ink}/s^{-1} = (2.98{\pm}1.40){\times}10^{12}$exp$[(- 55800{\pm}1800)/RT]$> where $k_{un}$ is the observed rate constant of cis-1-bromopropene(1-B$P_c$) to trans-1-bromopropene(1-B$P_t$) under uninhibited condition at initial pressure of 50 Torr and $k_{ink}$ is the rate constant under maximal inhibition by cyclohexene. The ratio of rate constants for bromine atom elimination from the allylic hydrogen of reactant(1-BP) and from the inhibitors, propene and cyclohexene, were measured from the observed rates of the uninhibited and inhibited reactions. The inhibition efficiencies of cyclohexene and propene were compared kinetically from the rate constants and shown to give good agreement with the previous results reported from other alkyl bromide pyrolyses.

• Bulletin of the Korean Chemical Society
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• 제28권5호
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• pp.758-762
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• 2007

A new alkyldithiocarbonate (xanthate), as sodium salts, C2H5OCS2Na, was synthesized by the reaction between CS2 with ethyl alcohol in the presence of NaOH. The new xanthate was characterized by 1H NMR, IR and elemental analysis. Then, the new synthesized compound was examined for functional study of cresolase activity of Mushroom Tyrosinase (MT) from a commercial source of Agricus bisporus in 10 mM phosphate buffer pH 6.8, at three temperatures of 10, 20 and 33℃ using UV spectrophotemetry. 4-[(4-methylphenyl)- azo]-phenol (MePAPh) was used as a synthetic substrate for the enzyme for cresolase reaction. The results show that ethyl xanthate can activate or inhibit the cresolase activity of mushroom tyrosinase depending to the concentration of ethyl xanthate. It was concluded that the enzyme has two distinct sites for ethyl xanthate. The first one is a high-affinity activation site and the other is a low-affinity inhibition site. Activation of the enzyme in the low concentration of ethyl xanthate arises from increasing the affinity of binding for the substrate as well as increasing the enzyme catalytic constant. The affinity of ligand binding in the activation site is decreased by increasing of the temperature, which is the opposite result for the inhibition site. Hence, the nature of the interaction of ethyl xanthate is different in two distinct sites. The binding process for cresolase inhibition is only entropy driven, meanwhile the binding process for cresolase activation is not only entropy driven but also enthalpy driven means that hydrophobic interaction is more important in the inhibition site.

• Journal of Microbiology and Biotechnology
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• 제22권12호
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• pp.1758-1766
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• 2012

An extensive investigation was carried out to describe the kinetics of cell growth, substrate consumption, and product formation in the batch fermentation using starch as substrate. Evaluation of intrinsic kinetic parameters was carried out using a best-fit unstructured model. A nonlinear regression technique was applied for computational purpose. The Andrew's model showed a comparatively better $R^2$ value among all tested models. The values of specific growth rate (${\mu}_{max}$), saturation constant ($K_S$), inhibition constant ($K_I$), and $Y_{X/S}$ were found to be 0.109 $h^{-1}$, 11.1 g/l, 0.012 g/l, and 1.003, respectively. The Leudeking-Piret model was used to study the product formation kinetics and the process was found to be growth-associated. The growth-associated constant (${\alpha}$) for protease production was sensitive to substrate concentration. Its value was fairly constant up to a substrate concentration of 30.8 g/l, and then decreased.

• KSBB Journal
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• 제8권4호
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• pp.341-350
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• 1993

본 연구에서는 sMMO를 갖는 메탄 자화균인 M. triclwsporium OB3b를 이용하여 메탄올 생산을 위한 기초실험을 수행하였다. 중요한 결과를 요약하면 다음과 같다(Table 2). 1. 세포 내 NADH의 재생을 위해 개미산을 첨가 할 때 whole-cell의 sMMO 활성은 pH 7.0 및 $30^{\circ}C$ 에서 최대값을 보이며 propylene을 기질로 할 경우 약 130nmol/mg cell min 정도이다. 2. 인산은 MMO와 MDH 활성을 모두 저해하나 M MDH에 대한 저해 정도가 훨씬 크므로 메탄올 합성 에 사용이 가능하다. Noncompetitive mode를 가정 할 때 저해상수는 각각 185mM(MMO) 및 42mM ( (MDH)이었다. 3. 메탄올은 MMO 활성을 저해하며 noncompeti­t tive mode를 가정할 때 propylene기질의 경우 2 21mM 이었다. 4. 균체 내 sMMO 활성은 성장이 멈춰진 상태에 셔 비교적 때}른 속도로 감소하며 고농도 인산용액에 서 그 속도가 더 빨라진다. 5. 인산농도 91mM에서 메탄은 메탄올로 산화되 어 축적되며 4.5시간 동안 에탄올의 생성속도는 평 균 79nmol/mg min이었다.

• KSBB Journal
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• 제11권3호
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• pp.276-287
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• 1996

하이브리도마 세포의 성장과 사망, 모노클론 항체의 생산, 포도당과 글루타민의 소비, 그리고 유산과 암모늄 이옹의 생산에 미치는 클루타민의 영 향을 조사하기 위해 초기 글루타민 농도를 변화시키면서 하이브리도마 세포의 회분식 현탁배양을 실시하였다. 실험 결과에 기초하여 세포의 성장속도, 영양물(포도당과 글루타민) 소비속도, 그리고 모노클론 항체 및 대사 부산물(유산과 암모늄이온)의 생산 속도를 예측할 수 있는 수학적 모델이 제시되었다. 포도당과 글루타민에 대해서는 중첩 적인 Monod 형식이며 암모늄 이옹과 유산에 대해 서는 Non-copmetitive inhibition 관계로 표시되는 세포의 비성장 속도에 관한 방정식이 개발되었다. 유산에 대한 억제 상수는 유산농도에 반바례하였다. 세포의 비사망 속도는 포도당, 글루타민, 암모 늄 이온과 유산 농도의 함수로 유도되었다.

• Journal of Microbiology
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• 제40권1호
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• pp.33-37
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• 2002

An enzymatic reaction for the production of D-alanine from D-aspartic acid and pyruvate as substrates by a thermostable D-amino acid aminotransferase (D-AAT) was investigated at various conditions In the temperature range of 40-70$\^{C}$ and pH range of 6.0-9.5. The D-AAT was produced with recombinant E. coli BL21, which hosted the chimeric plasmid pTLK2 harboring the D-AAT from the novel thermophilic Bacillus sp. LK-2. The enzyme reaction was shown to follow the Ping Pong Bi Bi mechanism. The K$\_$m/ values for D-aspartic acid and pyruvate were 4.38 mar and 0.72 mM, respectively. It was observed that competitive inhibition by D-alanine, the product of this reaction, was evident with the inhibition constant K$\_$i/ value of 0.1 mM. A unique feature of this reaction scheme is that the decorboxylation of oxaloacetic acid, one of the products, spontaneously produces pyruvate. Therefore, only a catalytic amount of pyruvate is necessary for the enzyme conversion reaction to proceed. A typical time-course kinetic study skewed that D-alanine up to 88 mM could be produced from 100 mM of D-aspartic acid with a molar yield of 1.0.