• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.30 no.2
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• pp.24-29
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• 1998

This study was carried out in order to elucidate the deterioration mechanism of paper according to various sizing chemicals. No additive paper and four kinds of papers containing rosin-alum, alum only, alkylketene dimer(AKD)-cation polymer and cation polymer only were treated by UV light to study changes of water-resistant, optical and mechanical properties from the view points of natural deterioration of paper. Since rosin chemicals have UV absorption at the relatively long wavelength region, rosins are degraded to form hydrophilic groups such as carboxylic acid from their double bonds by UV treatments. These phenomena caused the decreasing of sizing degree and wetting time in case of rosin-sized paper, while the UV treatments brought about the slight increase of wetting time in rosin-free papers such as no additive, alum and kymene only paper owing to the auto-sizing effect. Optical properties were primarily influenced by sizing chemicals. Rosin-sized paper showed lower brightness after UV and near UV treatment because of its UV instability.

• Applied Biological Chemistry
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• v.36 no.1
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• pp.33-37
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• 1993

Oxidations products of ${\alpha}-tocopherol$, ${\gamma}-tocopherol$ and ${\gamma}-tocotrienol$ in lipophilic reaction media were studied. ${\alpha}-Tocopherylquinone$, ${\gamma}-tocopherylquinone$ and ${\gamma}-tocotrienylquinone$ were fractionated using micro column, isolated and identified by HPLC and MS.

• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1621-1627
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• 2010

The investigation of the catalytic activity of supported rhodium(I) complex [Rh(P-S)$(CO)_2$] (P-S; polymer anchored salicylic acid) toward the reductive carbonylation of nitrobenzene in DMF medium has been reported. Use of basic cocatalysts in the reaction medium enhanced the percentage of more useful phenyl carbamates. Spectroscopic studies indicate that the reaction proceeds through a dimer species [Rh(HS)(CO)(C(O)$OCH_3$)(${\mu}-OCH_3)]_2$ and phenyl isocyanate is formed as an intermediate. A plausible reaction mechanism based on the identification of reactive intermediates from the soluble rhodium variety has been proposed for the carbonylation process.

• Bulletin of the Korean Chemical Society
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• v.34 no.2
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• pp.565-568
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• 2013

Acetyl-CoA carboxylases (ACCs) play critical roles in fatty acid synthesis and oxidation by the catalytic activity of the carboxylation of acetyl-CoA to malonyl-CoA. It is known that ACCs are inactivated through reversible phosphorylation by AMP-activated protein kinase (AMPK) and allosterically activated by citrate. Here, we determined the crystal structures of biotin carboxylase (BC) domain of human ACC2 phosphorylated by AMPK in the presence of citrate in order to elucidate the activation mechanism by citrate. This structure shows that phosphorylated Ser222 is released from the dimer interface, and thereby facilitating the dimerization or oligomerization of the BC domain allosterically. This structural explanation is coincident with the experimental result that the phosphorylated Ser222 was dephosphorylated more easily by protein phosphatase 2A (PP2A) as the citrate concentration increases.

• Journal of the Korean Chemical Society
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• v.29 no.5
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• pp.510-515
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• 1985

Color of $MoO_{(aq)}^{3+}$ in concentrated methanesulfonic acid (∼10M) changes dark green due to the formation of $Mo_2O_2(OH)_{2(aq)}^{4+}$ dimer. This color is similar to that shown by addition of water to that shown by addition of water to green $MoO_{(aq)}^{3+}$ solution in 15-16M methanesulfonic acid. The molar extinction coefficient of monomer in 15M methanesulfonic acid is about 20 at 415nm. Rate constants are independent on the aquomolybdenum (V) and hydrogen ion concentration under the condition of this experment. Bridging hydroxides of $Mo_2O_2(OH)_{2(aq)}^{4+}$ are dehydrogenated at the less concentration of ∼6 M for HPTS and ∼10M for $CH_3SO_3H$. The structure of both the yl-oxygens and the bridging oxygens of final product is identified to (*image)unit.

• Korean Journal of Food Science and Technology
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• v.5 no.1
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• pp.36-41
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• 1973

Chemical changes with time of frying-fats during the frying process (beef tallow with 0.01% BHA and 0.01% BHT, turnover rate 9%/hr and $140{\pm}10^{\circ}C$ temperature) of Ramyon on a commercial scale were studied. No significant changes of carbonyl value and peroxide value were noted up to 120 hrs. However, small increases in acid value, color and dimeric fatty acid were noted. Small decreases in iodine value and the content of unsaturated fatty acids were also observed. Under the experimental storage condition, when the stability of fats heated were compared to fresh fat, minor differences in carbonyl value and weight gain were noted. All of these demonstrated that frying-fats commercially used in Ramyon frying system were maintained in good quality during the frying process.

• Microbiology and Biotechnology Letters
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• v.47 no.1
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• pp.54-63
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• 2019

Rubus coreanus Miquel (RCM), also known as Korean blackberry or bokbunja, is used as a South Korean traditional medicine to treat acne and inflammatory skin conditions. The antimicrobial activity of RCM root and its active compounds remain unclear. In this study, we prepared a 50% ethanol fraction, ethyl acetate fraction, and acid-treated ethyl acetate fraction (aglycone fraction) of RCM root, and evaluated antibacterial activities against the skin pathogens Staphylococcus aureus, Pseudomonas acnes, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa. In a paper disc assay, all fractions of RCM root showed antimicrobial activities against the five skin pathogens. The ethyl acetate fraction displayed 6-, 12-, and 2-fold higher minimal inhibitory concentration (MIC) than the 50% ethanol fraction against S. aureus, E. coli, and P. acnes, respectively. The aglycone fraction displayed 2-fold higher MIC than methyl paraben against P. acnes, S. aureus, E. coli, and P. aeruginosa. The ethyl acetate fraction displayed a minimal bactericidal concentration (MBC) similar to that of methyl paraben, and the aglycone fraction showed 2- to 4-fold higher MBCs than those of methyl paraben. In particular, the ethyl acetate fraction was not cytotoxic and showed thermal stability after incubation at high temperatures ($60-121^{\circ}C$). Finally, the ethyl acetate fraction was separated and four components were identified: procyanidin C, propelagonidin dimer, ellagic acid, and methyl ellagic acid acetyl pentose. The compounds showed high antibacterial activities. These results suggest that RCM root is potentially applicable as a natural preservative in cosmetics.

• BMB Reports
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• v.33 no.4
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• pp.326-331
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• 2000

Acidic chitinases from the gizzards of a broiler were purified to homogeneity, using precipitation with $(NH_{4})_{2}SO_{4}$, ion exchanger chromatography, gel filtration, chromatofocusing and hydrophobic interaction chromatography. The enzymes, GAC1 and GAC2, were purified 180- and 194- folds with a recovery of 4.9% and 2.7%, respectively. The molecular mass of GAC1 and GAC2 were 48.2 kDa and 57.8 kDa, respectively. Chromatofocusing resulted in a pI of 3.1 for both enzymes. The purified enzymes were endochitinases that were devoid of ${\beta}-N-acetylglucosaminidase$ and lysozyme activity. Kinetic studies using $[^3H]chitin$ indicate that GAC1 has a $K_m$ and $V_{max}$ of 1.97 mg/ml and 185 mg/mg protein/h, respectively. The GAC2 has a $K_m$ and $V_{max}$ of 0.42 mg/ml and 92.3 mg/mg protein/h, respectively at optimal pH and temperature (pH 5.0 and $60^{\circ}C$). When the pentamer and hexamer of N-acetylglucosamine (GlcNAc) were used as a substrate, the major product by GAC1 was the dimer of GlcNAc with a differential accumulation of the monomer and trimer, depending upon the substrate. However, the GAC2 produced the dimer and trimer in an equal quantity, regardless of the substrate used. The first 9 $NH_2-terminal$ amino acid residues of the purified gizzard chitinase GAC1 and GAC2 shared a 100% homology. The first 25 $NH_2-terminal$ amino acid residues of GAC1 also shared 55-60% homology with animal chitinases and some animal proteins, such as whey protein and oviduct-specific proteins. However, little homology was found with either microbial and plant chitinases, or egg white lysozyme.

• Microbiology and Biotechnology Letters
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• v.17 no.6
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• pp.580-586
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• 1989

Penicillium sp. CB-20 was selected for strong polygalacturonase activity among various strains of molds found in soil. The optimum pH for the enzyme activity was 5.0 and optimum temperature was 4$0^{\circ}C$. The enzyme was relatively stable in acidic condition and unstable by heat treatment. The activation energy, Km and V$_{max}$ for the polygalacturonase were 2.499 Kcal/mol, 2.13$\times$10$^{-2}$mol/l, and 104.17 $\mu$mol/min. The activity of polygalacturonase was inhibited by Ag$^{+}$, Cu$^{++}$, Pb$^{++}$, Fe$^{+++}$, $Ca^{++}$, Na$^+$, Mn$^{++}$. The enzyme can be inactivated by the treatment ethylenediamintetra acetic acid, 2,4-dinitrophenol and $H_2O$$_2$. The results indicate the possible involvement of histidine, chelate and terminal amino group as active site. The enzyme was endo-type polygalacturonase.

• Applied Chemistry for Engineering
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• v.28 no.1
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• pp.23-28
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• 2017

Pyrolysis characteristics of waste plastic films were investigated by using a thermogravimetric analysis and pyrolyzer-gas chromatography/mass spectrometry. Thermogravimetric analysis results revealed that the pyrolysis of waste plastic films can be divided into two distinct reactions; (1) the decomposition reaction of starch at between 200 and $370^{\circ}C$ and (2) that of other plastic polymers such as PS, PP, PE at between 370 and $510^{\circ}C$. The kinetic analysis results obtained by using the revised Ozawa method indicated that the apparent activation energy of the pyrolysis reaction of waste plastic films was also changed dramatically according to the different decomposition reactions of two major waste plastic film components. Py-GC/MS results also revealed that the typical pyrolyzates of each polymer in waste plastic films were levoglucosan (starch), terephthalic acid (PET), styrene monomer, dimer, and trimer (PS), methylated alkenes (PP), and triplet peaks (PE) composed of alkadiene/alkene/alkane. The phthalate, used as a polymer additive, was also detected on the pyrogram of waste plastic films mixture.