• Bulletin of the Korean Chemical Society
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• 제22권1호
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• pp.84-86
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• 2001

• Journal of Electrochemical Science and Technology
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• 제11권3호
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• pp.248-256
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• 2020

In this study, pyrocatechol violet (Pcv) is proposed for the first time as an efficient electrocatalyst for oxidation of sulfide and flow injection analysis (FIA) of sulfide. A graphite pencil electrode (GPE) was modified with Pcv via immersion of the GPE into 0.01 M Pcv solution for 15 min. Cyclic voltammograms (CVs) demonstrated that Pcv/GPE exhibits a good electrocatalytic performance due to shift in the potential from +400 at bare GPE to +70 mV at Pcv/GPE and obtaining an enhancement in the peak current compared with the bare GPE. A linear range between 0.25 and 250 μM sulfide with a detection limit of 0.07 μM was obtained from the recorded current-time curves in Flow Injection Analysis (FIA) of sulfide. Sulfide in water samples was also successfully determined using the proposed FI amperometric methods.

• 생약학회지
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• 제15권2호
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• pp.78-84
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• 1984

Polyphenol oxidase was purified from acetone powder extract of the root of Ixeris sonchifolia. The enzyme obtained by ammonium sulfate fractionation and sephadex G-200 gelfiltration gave 51-fold purification over the crude extract. The purified enzyme showed activity toward chlorogenic acid, caffeic acid and pyrocatechol. The kinetics of thermal inactivation of the enzyme followed first-order reaction. Potassium cyanide and cysteine were potent inhibitors.

• 한국미생물·생명공학회지
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• 제24권2호
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• pp.222-226
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• 1996

The enzymatic synthesis of 3, 4-dihydroxyphenyl-L-alanine (L-DOPA) was examined for the effects of the reaction additives such as sodium borate, alcohol, and organic solvents. The enzyme used was tyrosine phenol-lyase of Citrobacter freundii KCTC 2006 produced in Escherichia coli. The amounts of tyrosine phenol-lyase and pyridoxal-5-phosphate were optimized to 2.0 units/ml and 0.1 mM, respectively, for the synthetic reaction. Sodium borate, a substance that forms a complex with pyrocatechol, reduced the enzyme deactivation by pyrocatechol although it seriously inhibited the enzyme activity. Among the organic solvents tested, dimethylsulfoxide, dimethylformamide, and alcohol increased the productivity of the L-DOPA synthesis. In a reaction system with 5% methanol, L-DOPA concentration increased up to 210 mM after 24 hours, and 77.1% of which was separated as precipitates. The L-DOPA was purified to 99.96% by solubilizing and recrystallyzing the precipitates.

• Journal of Microbiology and Biotechnology
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• 제6권2호
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• pp.98-102
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• 1996

A thermostable tyrosine phenol-lyase gene of a thermophilic Symbiobacterium species was cloned and overexpressed in Escherichia coli in order to produce the biocatalyst for the synthesis of 3, 4-dihy-droxyphenyl-L-alanine (L-DOPA). The substrates used for the synthetic reaction were pyrocatechol, so-dium pyruvate, and ammonium chloride. The enzyme was stable up to $60^{\circ}C$, and the optimal temperature for the synthesis of L-DOPA was $37^{\circ}C$ . The optimal pH of the reaction was about 8.3. Enzyme activity was highly dependent on the amount of ammonium chloride and the optimal concentration was estimated to be 0.6 M. In the case of pyrocatechol, an inactivation of enzyme activity was observed at con-centrations higher than 0.1 M. Enzyme activity was increased by the presence of ethanol. Under op-timized conditions, L-DOPA production was carried out adding pyrocatechol and sodium pyruvate to the reaction solution intermittently to avoid substrate depletion during the reaction. The concentration of L-DOPA reached 29.8 g/l after 6 h, but the concentration didn t increase further because of the formation of byproducts by a non-enzymatic reaction between L-DOPA and pyruvate.

• 한국미생물·생명공학회지
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• 제24권1호
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• pp.44-49
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• 1996

By using the ${\beta}$-tyrosinase of Citrobacter freundii KCT2006, which was cloned and overexpressed in Escherichia coli, 3,4-dihydroxy phenyl-L-alanine (L-DOPA) was synthesized efficiently from pyrocatechol, sodium pyruvate, and ammonium acetate. Optimal temperature and pH for the reaction were determined to be about 18$^{\circ}C$ and 8.5, respectively. The effects of substrate concentrations were also examined at different concentrations of ammonium acetate, sodium pyruvate, and pyrocatechol. Ammoniumacetate and sodium pyruvate increased the reaction rate until the concentrations reached to 300mM and 50mM, respectively. Although pyrocatechol showed the optimal concentration at 20mM, it was controlled between 20mM and 50mM to avoid the depletion of substrate during the enzymatic synthesis. Meanwhile the synthetic rate was improved about 20% when ethanol was included in the reaction solution. Based on above results, a reaction medium for the productin of L-DOPA was prepared and incubated with 1 unit/ml of ${\beta}$-tyrosinase. Pyrocatechol and sodium pyruvate was added to the reaction solutin intermittently to avoid the substrate depletion during the enzymatic reaction. After 24 hour of reaction, 31.6g/l of L-DOPA was accumulated in the reaction solution as soluble and precipitated ones and the conversion yield was about 85.2%.

• 약학회지
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• 제48권6호
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• pp.384-390
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• 2004

Polyphenol oxidase-catalyzed oxidation of substrates (t-butylcatechol, 4-methylcatechol, chlorogenic acid, caffeic acid and pyrocatechol) were performed in the Ph range 4~8. Co ncentrations of substrate's major oxidation products were monitored by high performance liquid chromatograph. The nature and amounts of products formed were highly pH dependent. They also were ifluenced by kinds of substrates. Major oxidation product of 4-methylcatechol appeared the maxium value at pH 5, them of chlorogenic acid, caffeic acid and pyrocatechol at pH 6.0 and that of t-butylcatechol at pH 5~7. Time-dependent PPO activity was determined at $4^{\circ}C\;and\;30^{\circ}C$. PPO extracted by phosphate buffer containing triton X-114 (t-PPO) was more stable than PPO by phosphate buffer (b-PPO). The result of electrophoresis, at first PPO was showed only a band at 48 kd. After 1~3 days a partial degrade band was appeared in b-PPO and three partial degrade bands in t-PPO. No activity band was appeared in PPOs at $30^{\circ}C$ and b-PPO at $4^{\circ}C$ after 4 days. And a band (37 kDa) in t-PPO was remained finally and disappered. PPO from Perillae leaves has two activity bands at 48 and 37 kDa in previous paper. It was supposed that PPO in the leaves of Perilla frutescens was a protein having one molecular weight as 48 kDa. And 37 kDa protein, relatively proteolysis-resistant, was a proteolyzed form of a major form.

• 한국진공학회지
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• 제2권2호
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• pp.181-187
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• 1993

Si 이방성 에칭 용액인 EPW(Ethylenediamine, Pyrocatechol, Water) 용액내에서 potentiostat를 이용한 cyclic polarization 방법으로 양극 산화막의 연구를 수행하였다. p-Si 및 n-Si에서 양극 산화막의 breakdown potential은 동일한 값을 보였으며, $p^+$-Si의 경우에는 양극 산화막의 breakdown이 일어나지 않았다. 산화막의 XPS 분석결과 n-Si과 p-Si의 경우 Si 2p photopeak의 chemical shift는 각각 ${\Delta}$3.62eV, ${\Delta}$3.55eV였으며, $p^+$-Si의 경우에는 ${\Delta}$4.25eV였다. 따라서 $p^+$-Si의 양극 산화막이 light doping의 경우와 비교하여 커다란 에칭 저항성을 보이는 것은 산화막의 화학적 조성차이에 기인하는 것이라 생각된다. $p^+$-Si이 에칭 용액내에서 anodic bias 상태에 농이게 되면 boron이 표면으로 diffuse-out되는 것을 SIMS 분석을 통해 알 수 있었는데, 그 원인은 아직 분명하지는 않지만, 이것은 실제 etch-stop이 일어나는 임계 boron 농도가 일반적으로 알려진 값보다 훨씬 높을 것이라는 것을 시사한다.

• Bulletin of the Korean Chemical Society
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• 제27권4호
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• pp.563-567
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• 2006

The application of a synergistic solvent extraction by the formation of ternary complex with pyrocatechol violet (PV) and benzalkonium chloride (BC) was studied for determination of trace Zn(II) in water samples. The pH of sample solution and the amount of PV and BC added were optimized for the formation of the stable complex, a proper solvent was selected for the effective extraction, and the concentration of nitric acid was fixed for the back extraction of the complex from the solvent. After the ionic strength of 100 mL sample solution was adjusted to 0.1 M by adding NaCl and the pH was fixed at 9 with a carbonate buffer, 1.0 mL of 2% PV solution was added to form Zn(II)-PV complex then the Zn(II)-PV/BC ternary complex was made by adding 1.0 mL of 10% BC solution. The ternary complex was extracted into 10 mL of MIBK. And the ternary complex was back-extracted with 10 mL of 1.0 mol/L nitric acid to determine Zn(II) by a flame atomic absorption spectrophotometer (flame-AAS). The interference of concomitant ions on the extraction of Zn(II) was investigated. This procedure was applied to the analysis of three real samples such as Dalbang-dam water, laboratory tap water and Jungnajin seawater. The recoveries of Zn(II) in spiked samples were 86.58-104.1%.

• 한국인쇄학회지
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• 제16권1호
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• pp.25-38
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• 1998

The developing agent is the materials which first acts on silver grain and make it into metallic silver by reducing reaction. There are several types in developing agent, and according to Lumiere-Andresen principle, substitution product which has amino or hydroxyl group in benzen nucleus has a developing power, but all reduing substances are not in used. In the developing effect, not only the role of developing agent but also that of assistant materials are important. But in this work, we have studied effect, change by lith developing agent which require high contrast image. We made an developing experiment after having manufactured developing solution used hydroquinone and another developing agents like chlorohydroquinone, pyrocatechol and pyrogallol as developing agent. And we added that did in addition of diethanolamine and ascorbic acid, and then we examined the possibility of use.