• Macromolecular Research
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• v.17 no.12
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• pp.1021-1024
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• 2009

We successfully prepared high-flow polycarbonate (PC) by blending commercial PC with a low molecular weight PC oligomer. The oligomer was synthesized by the addition of a large quantity of mono functional phenol groups, and the chain end group was reacted with p-tertiary butyl phenol (PTBP) to block the reactivity. The viscosity average molecular weight ($M_v$) for the oligomer was about 4,000-5,000 g/mol, compared to ~19,000 g/mol for the PC blend obtained by blending 10 wt% of the prepared oligomer with the commercial grade PC ($M_v$ of 21,000 g/mol). The blended PC had a melt flow index of 45, which is 2.5 times higher, and a processing temperature that was $20^{\circ}C$ lower, than that of commercial grade PC having a similar $M_v$.

• Journal of the Korean Ceramic Society
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• v.31 no.2
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• pp.220-226
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• 1994

The hydrolysis and condensation reactions in the mixed alkoxide solutions of Si(OC2H5)4 and Zr(O-nC3H7)4 with various water contents (1, 2, 4, and 8 in molar ratio to alkoxide, r) and catalysts were examined by rheological measurements and the number average molecular weight in order to explain the shape of the polymer in the mixed alkoxide solutions. It was found that fibers could be drawn in the viscosity range of 1∼100P from the acid-catalyzed solutions with lower water contents of the mole ratio H2O/alkoxide, r 2. On the other hand, crack free bulk gel was formed from the acid-catalyzed solutions including a large amount of water (r 4), and the base-catalyzed solutions. The relation between the intrinsic viscosity [{{{{ eta }}] and the number average molecular weight n, namely [{{{{ eta }}]=Knα, has shown that the acid-catalyzed spinnable solutions (r=1 and 2) have linear polymers and the exponent α's are about 0.56 and 0.81, whereas non-spinnable solutions (r=4 and 8) have three dimensional network polymers or spherical particles and the exponent α's are 0.41∼0.51 and 0.35.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.352-355
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• 2000

Production of pullulan by Aureobasidium pullulans HP-2001 with agro-industrial byproducts was investigated. Agro-industrial byproducts from the rice processing industry for the traditional Korean food (AIB-A), apple juice production (AIB-B), and soybean sauce production (AIB-C) were used for carbon and nitrogen source for production of pullulan. Major components of AIB-A were glucose, maltose, maltotriose, and dextran. AIB-A and B were found to be good substitute to glucose as carbon source. Productivity of pullulan with AIB-A and B as carbon source was similar to that glucose. Molecular weight of pullulan produced with AIB-A and B was higher than that with glucose. Major components of AIB-B and C were carbohydrate, protein, fat and ash. AIB-C was also a good substitute to yeast extract as nitrogen source. Some of physiological conditions were examined for the large scale production of pullulan.

• Journal of the Korean Ceramic Society
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• v.24 no.6
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• pp.561-571
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• 1987

In case of glass ceramics and powder preparation from the metalakoxide solutions, metalakoxide solutions with a various species of alkoxy groups have unique characteristics. Therefore, in this study, the mixing ability of homogeneous sol, gel morphology and physical properties of gels were investigated by the changes in terms of the different four alkoxy groups, CH3-, C2H5-, i-C3H7-n-C4H9-, along with the catalyst for the purpose of the observation about the homogenous transition range from sol to gel. As a result, when the fixed condition was mol ratio of H2O/Si(OR)4=2.0 and variables were batch composition and addition amount of catalyst, the characteristics of Tetra-normal-Butoxysilane and Tetra-iso-propoxysilane systems had very narrow sol-gel conversion region than Tetramethoxysilane and Tetraethoxysilane system. And silicon-alkoxide, systems having narrow sol-gel conversion region were enlarged by addition of catalyst. In viewpoint of the weight loss of gel produced by hydrolysis of silicon alkoxide systems with different four alkoxy groups, the amounts of weight loss of gel containing large molecular alkoxy groups were much more than those of small molecular alkoxy group.

• Textile Coloration and Finishing
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• v.13 no.1
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• pp.38-44
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• 2001

The adsorption ability of dyes on chitin, a natural polymer was investigated for decolorization of dye wastewater. Chitin was manufactured in lab by decalcification in dilute aqueous hydrochloric acid solution and deproteination in dilute aqueous sodium hydroxide solution with shrimp shells. Absorbance of residue solution of dyebaths after dye adsorptions of chtin were measured in varieties of dye concentration and dipping periods. Three kinds of Direct dyes -C.I. Direct Red 81 (red 81), C.I. Direct Brown l(brown 1) and C.I. Direct Green 26(green 26) - were used. Red 81 and brown 1 have smaller molecular weight than green 26. The results from experimentals were of]tamed as follows: 1) Adsorption of green 26 was improved in dyebath by addition of salt, but red 81 and brown 1 were not found any improvements. 2) Smaller size of chitin particles could be absorbed much more speedy. In this experiments, the smallest range of chitin particle size was $250\mu{m}$ and less. 3) The most efficient amount of chitin for 20m1 of dyebath was 0.2g, 4) Both of red 81 and brown 1 showed good and speedy adsorption abilities as dyestuffs of over 90 percent in just one minute in dyebath of 0.01% dye concentration. But green 26 was absorbed slowly because of its large molecular weight. It took 40minutes to absorb dyestuffs of over 90 percent in dyebath of 0.01% dye concentration.

• Journal of Microbiology and Biotechnology
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• v.9 no.6
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• pp.854-860
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• 1999

Superoxide dismutase (SOD) was purified to homogeneity from fruiting bodies of edible mushroom, Lentinus edodes, by ammonium sulfate precipitation, diethylaminoethyl (DEAE)-Sepharose FF ion-exchange chromatography, Sephacryl S-200 gel filtration chromatography, and preparative PAGE. The molecular weight of the purified enzyme was estimated to be approximately 54 kDa by gel filtration chromatography, and the enzyme was shown to be consisted of two identical subunits of molecular weight 27 kDa by SDS-PAGE. The isoelectric point of the enzyme was 4.9 as determined by isoelectric focusing. The enzyme had optimal pH and temperature of pH 8.0 and $20^{\circ}C$, respectively. The activity of the enzyme was inhibited by hydrogen peroxide, but inhibited less by cyanide and azide. The native enzyme was found to contain 0.89g-atom of iron, 0.75g-atom of zinc, and 0.46g-atom of copper per mol of enzyme. Analysis of amino acids composition revealed that the SOD from L. edodes contained a relatively large amount of glutamic acid/glutamine, proline, cysteine, isoleucine, and leucine, but only a small amount of aspartic acid/asparagine, tyrosine, and tryptophan when compared to the other iron-containing SODs.

• Food Science and Biotechnology
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• v.15 no.3
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• pp.424-430
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• 2006

Low molecular weight polyphenols were isolated from hot water extracts of radiata pine (Pinus radiata) bark using a Sephadex LH-20 column and characterized by $^1H$ and $^{13}C$ NMR, UV, FT-IR, and GC-MS analyses. Major compounds isolated and identified were protocatechuic acid, trans-taxifolin, and quercetin. Trans-taxifolin, an important intermediate in biosynthetic route of proanthocyanidin (PA), was isolated in large quantities and indicates that PA is a major component of radiata pine bark. Small amounts of polyphenols were identified by GC-MS analysis. The presence of p-hydroxybenzoic acid, vanillic acid, protocatechuic acid, cis- and trans-feruic acid, p-coumaric acid, trans-caffeic acid, (-)-epicatechin, (+)-catechin, trans- and cis-taxifolin, (+)-gallocatechin, and quercetin was confirmed by comparison of mass fragmentation patterns and retention times (RT) with authentic samples. In addition, the presence of astringenin, astringenin glycoside, trans- and cis-leucodelphinidin was strongly assumed from characteristic mass fragment ions due to their conjugated structure and retro Diels-Alder reaction, and also from biosynthetic route of PA. GC-MS analysis allowed us to detect small amounts of phenolic acids and flavonoids and eventually discriminate trans- and cis-configuration in the identified polyphenols.

• Journal of Microbiology and Biotechnology
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• v.4 no.4
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• pp.256-263
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• 1994

The aceB gene, encoding for malate synthase, one of the key enzymes of glyoxylate bypass, was isolated from a pMT1-based Corynebacterium glutamicum gene library via complementation of an Escherichia coli aceB mutant on an acetate minimal medium. The aceB gene was closely linked to aceA, separated by 598 base pairs, and transcribed in divergent direction. The aceB expressed a protein product of Mr 83, 000 in Corynebacterium glutamicum which was unusually large compared with those of other malate synthases. A DNA-sequence analysis of the cloned DNA identified an open-reading frame of 2, 217 base pairs which encodes a protein with the molecular weight of 82, 311 comprising 739 aminoo acids. The putative protein product showed only limited amino acid-sequence homology to its counteliparts in other organisms. The N-terminal region of the protein, which shows no apparent homology with the known sequences of other malate synthases, appeared to be responsible for the protein s unusually large size. A potential calciumbinding domain of EF-hand structure found among eukaryotes was detected in the N-terminal region of the deduced protein.

• Composites Research
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• v.34 no.1
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• pp.1-7
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• 2021

Fiber-reinforced thermoplastic composites are applied to transport industries to lightweight of body, and applications will be expanded gradually. In this study, the impregnation and mechanical properties of continuous glass fiber (GF) reinforced polycarbonate (PC) composites were evaluated with different molecular weights of PC. The continuous GF reinforced PC composite were prepared by using GF fabric and PC film via continuous compression molding method. The melting flow index and tensile strength of PC matrix were evaluated with different molecular weights. Mechanical properties (tensile, flexural, and compressive) and pore rate of GF/PC composite were evaluated with different molecular weights of PC. The fracture behavior was analyzed to fracture surface of GF/PC composite using FE-SEM images. As these results, it was condition of representing the best mechanical property that the GF/PC composite was prepared by using PC of 20,000 g/mol as matrix.

• Applied Chemistry for Engineering
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• v.18 no.6
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• pp.607-611
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• 2007

To improve transfection efficiency, we prepared histidine-low molecular weight water-soluble chitosan (LMWSC) having the potential to form complex with DNA as a cationic polymer. Histidine-LMWSC was synthesized by the esterification reaction and removing phthaloyl group. The histidine-LMWSC was characterized using FT-IR, $^1H$ NMR spectra. Histidine-LMWSC was complexed with plasmid DNA (pDNA) in various polymer/DNA (N/P) weight ratios, and the complex was identified using gel retardation assay. The particle sizes of the hisitidine-LMWSC/DNA complexes were measured on a DLS instrument by fixing the histidine-LMWSC/DNA weight ratio of 10/1. Owing to the utilization of a large excess amount of cationic LMWSC against anionic DNA, the particle size of histidine-LMWSC/DNA complexes was in the range of 100~200 nm. Therefore, histidine-LMWSC will be useful in the development of gene carriers.