• BMB Reports
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• v.33 no.2
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• pp.133-137
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• 2000

To elucidate the effect of oxygen radicals on the molecular properties of proteins, the secondary and tertiary structure and molecular weight size of BSA and ${\beta}$-lactoglobulin were examined after irradiation of proteins at various doses. Gamma-irradiation of protein solutions caused the disruption of the ordered structure of protein molecules as well as degradation, cross-linking, and aggregation of the polypeptide chains. As a model system, BSA and ${\beta}$-lactoglobulin were used as a typical ${\alpha}$-helical and a ${\beta}$-sheet structure protein, respectively. A circular dichroism study showed that the increase of radiation decreased the ordered structure of proteins with a concurrent increase of aperiodic structure content. Fluorescence spectroscopy indicated that irradiation quenched the emission intensity excited at 280 nm. SDS-PAGE and a gel permeation chromatography study indicated that radiation caused initial fragmentation of proteins resulting in a subsequent aggregation due to cross-linking of protein molecules.

• Journal of Aquaculture
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• v.19 no.1
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• pp.40-46
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• 2006

Bacillus subtilis strain with highly active chitosanase was isolated from the intestine of Sebastiscus marmoratus (scorpion fish). It was named as Bacillus subtilis CH1 by morphological, biochemical and 165 rRNA gene analysis. The optimal conditions for chitosanase production were investigated. The optimum carbon and nitrogen sources for Bacillus stibtilis CH1 were 2% starch and 1% yeast extract respectively. Unlike other chitosanases, the expression of this chitosanase was not induced or slightly induced with chitosan. The chitosanase secreted into the medium were concentrated with ammonium sulfate precipitation and purified by gel permeation chromatography. The molecular weight of purified chitosanase was 30 kDa. The optimum pH and temperature of purified chitosanase were 5.5 and $60^{\circ}C$ respectively. The purified chitosanase was continuously thermostable at $40^{\circ}C$ and showed stable activity between pH 6.0 and 8.0. Chitosanase activity of Bacillus subtilis CH1 under optimum condition was 4.1 units/ml.

• Journal of Microbiology and Biotechnology
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• v.17 no.10
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• pp.1695-1699
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• 2007

Ferritin is an iron storage protein found in most living organisms as a natural assembled macromolecule. For studying the functional ability of the ferritin assembly, human H- and L-ferritins were expressed and purified from Pichia pastoris strain GS115. The recombinant H- and L-ferritins showed a globular form with transmission electron microscopy. The rate of iron uptake for H-ferritin was significantly faster than that for the L-ferritin in vitro. By gel permeation chromatography analysis, recombinant ferritins were confirmed as multimeric subunits with high molecular weight and it was indicated that assembled subunits were able to store iron in vivo.

• Journal of Applied Biological Chemistry
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• v.48 no.2
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• pp.75-78
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• 2005

Halotolerant protease produced by Halomonas marisflava KCCM 10457 was partially purified through ammonium sulfate precipitation and Sephacryl S-200HR gel permeation chromatography. Optimal pH and temperature of protease were 11.0 and $45^{\circ}C$, respectively. Enzyme activity was inhibited by $Cu^{2+}$, $Hg^{2+}$, $Fe^{2+}$, and $Fe^{3+}$, and selectively inhibited by p-chloromercuribenzoic acid (PCMB), suggesting this enzyme is cysteine protease. The enzyme is halotolerant, because it retained 77% of original activity in presence of 3.33 M NaCl. The protease showed broad substrate specificity to various natural proteins; BSA, casein, egg albumin, gelatin, and hemoglobin.

• Journal of Microbiology and Biotechnology
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• v.16 no.6
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• pp.961-964
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• 2006

GDP-mannosyltransferase (GMT) is an enzyme responsible for the addition of a mannose to glucose ($\alpha$[1$\rightarrow$3]) during biosynthesis of the water-soluble branched polysaccharide acetan in Acefobacter species. In an effort to obtain a cellulose-overproducing bacterium, a mutant defective in GMT of Acetobacter xylinum KCCM 10100 was constructed by single crossover homologous recombination using part of the aceA gene encoding GMT amplified by polymerase chain reaction. The GMT-disrupted mutant produced 23% more cellulose, but 16% less water-soluble polysaccharide than those of the wild-type strain. Analysis of the sugar composition by gel permeation chromatography revealed that water-soluble polysaccharides produced by the GMT-defective mutant contained no mannose molecule.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.266-266
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• 2006

The cell spheroid (multicellular mass) is enhanced cell functions because of the cell-cell interaction compared with the individual cell. The objective of this study is synthesis, characterization and evaluation of novel crosslinkers to form spheroid in a short time. Our approach to bridge cells is based on the crosslinking of the cell membrane via the hydrophobic interaction. The crosslinker was prepared by the reaction between ethylenediamine and poly(ethylene glycol) (PEG) derivative with oleyl group as hydrophobic group at the terminal group. The product was characterized with gel permeation chromatography (GPC) and FT-IR. Furthermore, cell culture experiment was also performed to confirm spheroid formation. The function of prepared spheroids was evaluated.

• Biotechnology and Bioprocess Engineering:BBE
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• v.9 no.5
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• pp.379-382
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• 2004

Entomopathogenic nematodes are used for insect control. Herein, an extracellular protease was partially purified from a culture supernatant of Xenorhabdus nematophilus, a symbiotic bacterium of an entomopathogenic nematode, Steinernema glaseri: using precipitation with $80\%$ v/v isopropyl alcohol followed by gel permeation chromatography with a packed Sephacryl S-300 HR media. The partially purified protease exhibited maximal activity at pH 7 in the presence of 1 mM $CaCl_2$. The protease was identified as a metallo-protease based on the inhibition of its activity by the metal chelating agent, EDTA.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.237-240
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• 2002

Amino terminated polyetherimide(ATPEI) has been synthesized by bisphthalic anhydride arid m-phenylenediamine, after that characterized by differential scanning calorimetry(DSC), thermogravimetric analyzer(TGA). Fourier transform (FT-IR) spectroscopy and gel permeation chromatography(GPC). ATPEI was blend to improve the toughness of bisphenol-A type epoxy resin which was cured by nadic methyl anhydride(NMA). The fracture toughness and the molphology of the toughened epoxy resin was evaluated. The toughness of ATPEI modified epoxy resin was higher than that of the PEI modified epoxy resin. In addtion, carbon fiber/ATPEI modified epoxy resin composites were fabricated and the mechanical properties of the resulted composites were investigated.

• 한국생물공학회:학술대회논문집
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• 2002.04a
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• pp.500-503
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• 2002

In order to improve the physical properties of food such as texture and food self-life. Transglutaminase(mTG) from Streptoverticillum morbarense was prepared. In the preliminary experiments, presence of proteases in the crude enzyme did not improve the texture of dough, which mean the inteference of mTG reaction by the proteases. Among the cation exchange resins tested for the removal of proteases, Monoplus S 100(Bayer, Germany) was the most efficient resin with 20 fold increase in the mTG/protease activity ratio. By further purification steps with a quaternary ammonia salt resin and a gel permeation chromatography, proteases were effectively removed from the preparation. Therefore, the improvement of flour texture was shown by adding the protease-free mTG.

• Journal of Applied Biological Chemistry
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• v.50 no.4
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• pp.221-226
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• 2007

The high molecular-weight mucilage extracted and purified from cactus fruit of Opuntia ficus-indica var. Saboten was degraded by the cell-free culture filtrate of a fungus isolated from soil. TLC analysis of the polymeric mucilage after incubation with the fungal culture filtrate confirmed its degradation. When the degradation products were tested for their qualitative reactions with ninhydrin and phenol-sulfuric acid, only phenol-sulfuric acid gave positive development, and ninhydrin did not show any observable color reaction. This coloring reaction suggested the presence of a carbohydrate without an amino group within the mucilage. Analyses by HPLC and liquid gel permeation chromatography on sephadex G-100 also provided additional information on degradation of the mucilage by the fungal culture filtrate. The sequences of ITS-5.8S rDNA from the fungal isolate that was cultivated for the preparation of mucilage-degrading enzyme showed 99% similarity to those of Pestalotiopsis aquatica.