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高玉鉉,姜馨龍,李敦日,金永洙,白采善,金京洙 조선대학교 약학연구소 1990 藥學硏究誌 Vol.12 No.1
In order to synthesize Methotraxate(MTX) analogues, author synthesized 3-〔〔〔2-(N-Ethyl-N-tosyl-p-aminobenzenecarboxamido)ethyl〕thio〕methyl〕-2-methylimidazo-〔1,2-a〕pyridine(15), 2-(N-Ethyl-N-toyl-p-aminobenzoyl)-5-phenyl-2H-tetrazole(16),2-(N-Ethyl-N-tosyl-p-aminobenzoyl)-5-(nitrobenzyl)-2H-tetrazole(17), 3-〔〔〔2-(N-Ethyl-p-aminobenzenecarboxamido〕ethyl〕thio〕methyl〕-2-methylimidazo〔1,2-a〕pyridine(18), 2-(N-E-thyl-p-aminobenzoyl)-5-phenyl-2H-tetrazole(19), 2-(N-Ethyl-p-aminobenzoyl)-5-(4-nitro-benzyl)-2H-tetrazole(20), 2-Amino-3-cyano-5-〔3-〔〔〔2-(N-ethyl-p-aminobenzenecarboxa-mido)ethyl〕thio〕methyl〕-2-methylimidazo〔1,2-a〕pyridino〕methyl pyrazine(21), 2-Amino-3-cyano-5-〔2-N-ethyl-p-aminobenzol)-5-phenyl-2H-tetrazol-2-yl〕methylpyrazine(22), 3-A-mino-3-cyano-5-〔2-N-ethyl-p-aminobenzol)-5-(4-nitrobenzyl)-2H-tetrazol-2-yl〕methylp-yrazine(23), 2,4-Diamino-6-〔3-〔〔〔2-(N-ethyl-p-aminobenzenecarboxamido)ethyl〕thio〕methyl〕-2-methylimidazo〔1,2-a〕pyridino〕 methylpteridine(24), 2,4-Diamino-6-〔2-(N-ethyl-p-aminobenzoyl)-5-phenyl-2H-tetrazol-2-yl〕methylpteridine(25), and 2,4-Diamino-6-〔2-(N-ethyl-p-aminobenzol)-5-(4-nitrobenzyl)-2H-tetrazol-2-yl〕methylpteridine(26), respectively.
Silk Fibroin/Chitosan Conjugate Crosslinked by Tyrosinase
Kang, Gyung-Don,Lee, Ki-Hoon,Ki, Chang-Seok,Nahm, Joong-Hee,Park, Young-Hwan The Polymer Society of Korea 2004 Macromolecular Research Vol.12 No.5
Two biopolymers, silk fibroin (SF) and chitosan, were conjugated by tyrosinase (EC 1.14.18.1), a polyphenolic oxidase, to improve their physicochemical properties, such as their thermal properties and morphological stabilities in organic solvents. The crosslinking between SF and chitosan took place mainly through Michael addition reactions. A main reaction between the amino groups in chitosan and o-quinone, the oxidation product of the tyrosyl residue in SF, was confirmed by UV spectroscopy. Measurements of viscosity and light scattering indicated that the crosslinked SF/chitosan conjugate was compact: it had a smaller particle size because of tight bonding forces between the SF and chitosan molecular chains. Thermal decomposition of SF/chitosan conjugates crosslinked by tyrosinase occurred at higher temperatures. The adhesiveness of the SF/chitosan conjugates decreased steadily as the crosslinking reaction progressed. We propose that this new crosslinking method be used for the preparation of silk fibroin/chitosan conjugates using tyrosinase. We expect that SF/chitosan conjugates crosslinked by tyrosinase can be used preferentially in biomedical applications because of its unique properties and non-toxicity.
Crosslinking Reaction of Phenolic Side Chains in Silk Fibroin by Tyrosinase
Kang, Gyung-Don,Lee, Ki-Hoon,Ki, Chang-Seok,Park, Young-Hwan The Korean Fiber Society 2004 Fibers and polymers Vol.5 No.3
Tyrosinase oxidizes the tyrosyl residues in silk fibroin (SF) with oxygen, resulting in the production of ο-quinone residues. Subsequently, the inter-or intramolecular crosslinks are formed by reaction with amino groups in through nonenzymatic process. The measurement of oxygen consumption proved that the tyrosyl residues in SF were mostly oxidized to quinone residues by tyrosinase. The reaction mechanisms were proposed in this study and the crosslinking reaction of ο-quinone residues and the enzymatic oxidation of tyrosyl residues could be confirmed by the measurements of UV, $^1$H-NMR and GFC.
Effect of Low Molecular Weight Silk Fibroin on the Inhibition of Tyrosinase Activity
Kang, Gyung Don,Lee, Ki Hoon,Shin, Bong Seob,Nahm, Joong Hee,Park, Young Hwan Korean Society of Sericultural Science 2004 International Journal of Industrial Entomology Vol.9 No.1
Low molecular weight silk fibroin (LMSF), which was prepared by hydrolysis of silk fibroin using high-temperature and high-pressure method, was found to inhibit the oxidation of L-3,4,-dihydroxyphenylalanine (L-DOPA) catalyzed by mushroom tyrosinase (EC 1.14.18.1). LMSF contained mostly free amino acids such as L-glycine, L-alanine, and L-serine and oligopeptides, mainly glycine-alanine dimer. As a result of analyzing the inhibition kinetics from Lineweaver-Burk plots, L-glycine and glycine-alanine dimer showed noncompetitive behavior while uncompetitive behavior was observed in L-alanine, and L-serine. When weight percent concentration of ${ID_50}$ was compared, L-glycine was most effective on the inhibition and LMSF was also good enough for the inhibition effect of tyrosinase activity. LMSF showed a mixed-type inhibition and the inhibitory mechanism of LMSF might be caused by free amino acids and oligopeptides. As a result of spectroscopic observation with time, initial rate of increase of DOPAchrome decreased remarkably and the time to reach maximum absorbance increased as an increase of the concentration of L-glycine, meaning that L-glycine made itself mainly responsible for the formation of chelate with ${Cu^2+}$ in tyrosinase. However, in case of L-alanine, L-serine, and especially glycine-alanine dimmer, the production of DOPAchrome after an arrival at maximum absorbance decreased, indicating the production of adducts through the reaction with DOPAquinone.
Controlling the Thermosensitive Gelation Properties of Poly(organophosphazenes) by Blending
Kang, Gyung Don,Heo, Jeong-Yun,Jung, Sung Bum,Song, Soo-Chang WILEY-VCH Verlag 2005 Macromolecular Rapid Communications Vol.26 No.20
<P>Summary: After synthesizing both hard poly(organophosphazenes), which acted as strong hydrogels at a temperature below 37 °C, and soft poly(organophosphazenes), which displayed the opposite properties, we blended the polymers. When these polymers were blended at an appropriate ratio, the blended aqueous solution changed into a transparent hydrogel with improved mechanical properties at a temperature of 37 °C. According to DSC and IR measurements, the two polymers blended homogeneously and exhibited a behavior characteristic of a completely different copolymer.</P><P> <img src='wiley_img/10221336-2005-26-20-MARC200500472-gra001.gif' alt='wiley_img/10221336-2005-26-20-MARC200500472-gra001'> Graphic An aqueous poly(organophosphazene) solution at room temperature (left) is reversibly and rapidly transformed into a transparent hydrogel at body temperature (right) when a hard poly(organophosphazene) is blended with a soft one at an appropriate ratio. </P>
Kang, Gyung-Don,Lee, Ki-Hoon,Do, Sun-Gil,Kim, Chung-Sub,Suh, Jun-Gyo,Oh, Yang-Seok,Nahm, Joong-Hee Korean Society of Sericultural Science 2001 International Journal of Industrial Entomology Vol.2 No.1
Silk fibroin (SF) derided from the domestic silk worm, bombyx mori, is the natural protein and widely used as bio-functional materials as well as apparels. We studied the livers protective effect of SF from alcohol-induced hepatotoxicity in the alcohol preference mouse. To increase more absorption of SF in experimental animals, molecular weight of SF was lowered by 2N of HCI aqueous solution at 10$0^{\circ}C$ for 48 hrs. SF was added to liquid diet with alcohol and fed to the alcohol preference mice for 4 weeks. To assess the liver function, the concentration of alanine aminotransferase (AlT), aspartate aminotransferase (AST) and cholesterol present in either blood or liver tissue were measured. As compared with non-SF treated groups the SF-treated showed significantly low concentrations of ALT, AST, cholesterol and triacylglycerol values, respectively. Histopathological examination revealed that the extent of hepatocyte injury in the SF-treated group was reduced when it was compared with non SF-treated group. These results suggest that SF may have liver protective effects against alcohol-induced hepatotoxicity.
Study on a Partial Discharge Test for Low-Voltage Electronic Components
Gyung-Suk Kil,Dong-sik Kang,Don-ha Hwang,Jae-man Song,Jae-yong Song,Yong-ju Kim 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.III
This paper deals with a partial discharge (PD) test on low-voltage electronic components, which is increasingly being accepted as a non-destructive and effective dielectric test. A comparative experiment, combined with the withstand voltage test (WVT) specified in IEC standards, was carried out on low-voltage insulation transformers. The results show that the insulation degradation of the sample progresses during the WVT. However, if an apparent charge of below 1 pC is detected, the PD test can be performed within the range of 30 . 50 % of the test voltage specified in the WVT. Therefore, the PD test can be applied successfully in place of the WVT as a non-destructive test on low-voltage electronic components.e6