• Journal of the Korean Chemical Society
• /
• v.49 no.4
• /
• pp.377-380
• /
• 2005

• Journal of the Korean Chemical Society
• /
• v.47 no.6
• /
• pp.663-666
• /
• 2003

• Bulletin of the Korean Chemical Society
• /
• v.34 no.1
• /
• pp.243-245
• /
• 2013

Rate equations are exactly solved for the reversible consecutive reaction of the first-order and the time-dependence of concentrations is analytically determined for species in the reaction. With the assumption of pseudo first-order reaction, the calculation applies and determines the concentration of product accurately and explicitly as a function of time in the unimolecular decomposition of Lindemann and in the enzyme catalysis of Michaelis-Menten whose rate laws have been approximated in terms of reactant concentrations by the steady-state approximation.

• Macromolecular Research
• /
• v.14 no.2
• /
• pp.230-234
• /
• 2006

• Korean Chemical Engineering Research
• /
• v.43 no.1
• /
• pp.98-102
• /
• 2005

This article describes a study of chemical vapor deposition (CVD) of copper thin films on TiN substrates using (HFAC)Cu(DMB) as a precursor. The surface morphology and conformality of the Cu films as functions of substrate temperature and the presence or absence of iodine have been investigated. The surface roughness was increased significantly along with decrement of the step coverage by increasing the deposition temperature. The highest conformal films with the lowest surface roughness were obtained using the process of copper CVD, where iodine vapor were discretely introduced into the reactor during the growth of copper.

• Journal of Microbiology and Biotechnology
• /
• v.26 no.10
• /
• pp.1701-1707
• /
• 2016

Lipoxygenase (LOX) is an industrial enzyme with wide applications in food and pharmaceutical industries. The available structure information indicates that eukaryotic LOXs consist of N terminus β-barrel and C terminus catalytic domains. However, the latest crystal structure of Pseudomonas aeruginosa LOX shows it is significantly different from those of eukaryotic LOXs, including the N-terminal helix domain. In this paper, the functions of this N-terminal helix domain in the soluble expression and catalysis of P. aeruginosa LOX were analyzed. Genetic truncation of this helix domain resulted in an insoluble P. aeruginosa LOX mutant. The active C-terminal domain was obtained by dispase digestion of the P. aeruginosa LOX derivative containing the genetically introduced dispase recognition sites. This functional C-terminal domain showed raised substrate affinity but reduced catalytic activity and thermostability. Crystal structure analyses demonstrate that the broken polar contacts connecting the two domains and the exposed hydrophobic substrate binding pocket may contribute to the insoluble expression of the C terminus domain and the changes in the enzyme properties. Our data suggest that the N terminus domain of P. aeruginosa LOX is required for its soluble expression in E. coli, which is different from that of the eukaryotic LOXs. Besides this, this N-terminal domain is not necessary for catalysis but shows positive effects on the enzyme properties. The results presented here provide new and valuable information on the functions of the N terminus helix domain of P. aeruginosa LOX and further improvement of its enzyme properties by molecular modification.

• Environmental Engineering Research
• /
• v.25 no.4
• /
• pp.571-578
• /
• 2020

In this work, a detailed study on the electrochemical degradation of an azo dye, Orange G is performed using a platinum electrode. Indeed, the influence of the dye concentration (50-150 mg/L), the pH of the medium and the density of the electric current is studied on the rate of discoloration, the rate of mineralization, the efficiency of the electric current and the energy consumption. The UV-visible spectra of OG plotted against the degradation time show the decrease of the intensity of the characteristic dye peaks. In an environment rich in chlorides, all peaks disappear after 15 min of degradation. However, the peaks at wavelengths of 200 and 290 nm appeared after one hour of treatment. In K₂SO₄, the eliminated percentages are respectively 46, 54 and 61% for wavelengths of 245, 330 and 480 nm. This suggests that the degradation mechanisms in K₂SO₄ and KCl environments are not the same. In the middle rich in chlorides, the eliminated percentage of OG did not seem to be affected by the concentrations increase. These results confirm the hypothesis that electrochemical oxidation process is very favorable for concentrated pollutants discharge.

• The Korean Journal of Pesticide Science
• /
• v.8 no.4
• /
• pp.265-271
• /
• 2004

Hydrolytic reactivities of N-phenylphthalimid herbicide flumioxazine (S) were disccused using molecular orbital (MO) theoretical method. It is revealed that below pH 5.0, the protonation $(SH^+)$ to carbonyl oxygens atom $(O_{21})$ of 1,2-dicarboximino group by general acid catalysis $(k_A)$ with hydronium ion $(H_3O^+)$ proceeds via charge controled reaction. Whereas, the specific base catalysis $(k_{OH})$ with hydroxide anion via orbital controled reaction occurs above pH 8.0. We may concluded that in the range of pH $5.0\sim8.0$, the hydrolysis proceeds through nucleophilic addition elimination $(Ad_{N-E})$ reaction, these two reactions occur competitively.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.198-198
• /
• 2011

Organocatalysis is a relatively new and popular area within the field of chiral molecule synthesis. It is one of the main branches of enantioselective synthesis with enzymatic and organometallic catalysis. In recent years, immense high quality studies on catalysis by chiral secondary amines were reported. These progresses instantly led to different organocatalytic activation concepts, so thousands of researchers from academia and the chemical industry are currently involved in this field and new ideas, new approaches, and creative thinking have been rapidly emerged. Organocatalysts, some of which are natural products, appear to solve the problems of metal catalysts. Compared to metal-based catalysis, they have many advantages including savings in cost, time, and energy, easier experimental procedure, and reduction of chemical waste. These benefits originate from the following factors. First, organocatalysts are generally stable in oxygen and water in the atmosphere, there is no need for special equipments or experimental techniques to operate under anhydrous or anaerobic conditions. Second, organic reagents are naturally available from biological materials as single enantiomers that they are easy and cheap to prepare which makes them suitable for small-scale to industrial-scale reactions. Third, in terms of safety related catalysis, small organic molecules are non-toxic and environmentally friendly. Therefore, the purpose of this research is to develop novel synthetic methods and design for various organocatalyst. Furthermore, it is expected that these organocatalysts can be applied to a variety of asymmetric reactions and study the transition state of these reactions using a metal sulface. Here, we report the synthesis of unprecedented organocatalysts, proline and pyrrolidine derivatives with quaternary carbon center.

• Journal of the Korean Chemical Society
• /
• v.20 no.6
• /
• pp.525-532
• /
• 1976

Anionic polymerization of 2-pyrrolidone and ${\varepsilon}$-Caprolactam via $CO_2/KOH catalysis was attempted in order to find reaction condition and physical properties of polymers. In case of polymerization of 2-pyrrolidone, the yield of conversion was increased when the concentration of potassium hydroxide was reached above 8 mole percent. The optimum of CO_2/KOH$ mole ratio was 0.45. It was also found that the polymerization was taking place at moderate temperature which was around $50^{\circ}C$. With regard to polymerization of-caprolactam, the yield of conversion was relatively low at $80^{\circ}C$ to $90^{\circ}C$and higher yield of conversion was obtained at higher temperature between $150^{\circ}C$ to $180^{\circ}C$ regardless of $CO_2/KOH mole ratio. The inherent viscosity of nylon 4 and nylon 6 which was made via CO_2/KOH$ catalysis was measured. The observed inherent viscosity was between 2.0 to 5.0.