• Journal of Microbiology and Biotechnology
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• v.1 no.1
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• pp.54-62
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• 1991

Cyclodextrin glucanotransferase(CGTase) derived from Bacillus macerans was immobilized by (1) covalent linkage on chitosan and chitin with glutaraldehyde, (2) adsorption on DEAE-cellulose and Amberite IRA 900 after succinylation, and (3) entrapment on alginate and polyacrylamide by cross linking. Adsorption on Amberite IRA 900 and covalent linking on chitosan were identified to be the most suitable immobilization methods considering the yield of activity and stability of immobilized CGTase. The enzymatic properties of immobilized CGTase were investigated and compared with those of the soluble CGTase. Thermal stability of CGTase immobilized on chitosan was increased from 50 to $55^{\circ}C$, and the optimum temperature of CGTase immobilized on Amberite IRA 900 was shifted from 55 to $50^{\circ}C$. The effect of molecular size of soluble starch (substrate) on immobilized CGTase investigated using partially liquefied substrates with different dextrose equivalent(DE). Cyclodextrin(CD) conversion yield augmented according to the increase of DE level for immobilized CGTase on Amberite IRA 900. CD conversion yield of partially cyclized starch with soluble CGTase was higher compared with liquefied one with ${\alpha}-amylase$.

• Bulletin of the Korean Chemical Society
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• v.35 no.12
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• pp.3571-3575
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• 2014

Proteasome, a multicatalytic protease complex, has been validated as a promising therapeutic target in oncology. Carfilzomib (Kyprolis$^{(R)}$), a tetrapeptide epoxyketone, irreversibly inhibits the chymotrypsin-like (CT-L) activity of the proteasome and has been recently approved for multiple myeloma treatment by FDA. A chemistry effort was initiated to discover the compounds that are reversibly inhibit the proteasome by replacing the epoxyketone moiety of carfilzomib with a variety of ketones as reversible and covalent warheads at the C-terminus. The newly synthesized compounds exhibited significant inhibitory activity against CT-L activity of the human 20S proteasome. When the compounds were tested for cancer cell viability, 14-8 was found to be most potent in inhibiting Molt-4 acute lymphoblastic leukemia cell line with a $GI_{50}$ of $4.4{\mu}M$. Cytotoxic effects of 14-8 were further evaluated by cell cycle analysis and Western blotting, demonstrating activation of apoptotic pathways.

• Toxicological Research
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• v.16 no.3
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• pp.221-227
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• 2000

A 6-sulfooxymethylbenzo[a]pyrene (SMBP), the ultimate metabolite of methyl-substituted benzo[a]pyrene (BP), has been found to be carcinogenic in mice. These properties may be attributable to its strong reactivity with cellular macromolecules such as DNA. However, serum and its major constituent albumin attenuated significantly the cytotoxicity and mutagenicity of 5MBP in bacterial and mammalian cell systems. This inhibitory activity of serum against 5MBP-induced cytotoxicity and mutagenicity in Chinese hamster V79 cells appears to be caused by the reduced macromolecular adducts such as DNA and proteins, but serum failed to reduce 5MBP binding to naked calf thymus DNA. A number of proteins in the serum could act as nucleophiles that are able to intercept reactive chemicals through covalent binding. Albumin present in the plasma seems to be one of major components responsible for direct binding with 5MBp, thereby reducing its reactivity to genetic materials. We here determined which fraction is preferential for 5MBP binding through fractionation of 5MBP-treated serum with ammonium sulfate. The albumin-containing fraction had slightly more affinity for 5MBP than the immunoglobulin-containing fraction. Our results indicate that the covalent modification of plasma proteins may reduce 5MBP-induced damage.

• Journal of the Korean Ceramic Society
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• v.43 no.12 s.295
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• pp.839-845
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• 2006

Graphite has hexagonal closed packing structure with two bonding characteristics; (1) van der waals bonding between c axis, and (2) covalent bonding in the a and b axis. The weak van der waals bonds cause self-lubricant property, and the strong covalent bonds cause excellent electric and thermal conductivity. Furthermore, graphite is chemically very inert because of the material composed of only carbon elements. Thus, graphite is very useful for mechanical sealing materials. However, Graphite have porous microstructure because starting materials of graphite produce many volatile during the manufacturing processes. This causes low density of graphite, which is unsuitable for the mechanical sealing materials. Thus, further impregnation process is generally needed to enhance the graphite density. In this work, high density graphite is prepared with the principle of densification when coke and pitch binder, prepared from thermal treatment of coal tar pitch, become dehydrogenation during graphitization or carbonization.

• KSBB Journal
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• v.8 no.4
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• pp.320-327
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• 1993

Latex microspheres of styrene/acryl copolymer with acrylamide functional group were used for the stable covalent immobilization of an enzyme applicable for enzymatic synthesis of glycoside. The latex microspheres were coated with polyethyleneimine to establish structural and functional properties relevant to the covalent Immobilization with a high retention of activity. Polythyleneimine-coated microspheres satisfactorily immobilized the invertase for methyl fructoside synthesis, and model reaction were formed into alginate-enclosed microspheres biocatalyst. Using the alginate-enclosed microspheres biocatalyst, the yield of model glycoside was obtained as high as 52.2% at concentration of aqueous 30%(v/v) methanol and 0.291mo1/1 sucrose solution with 2U/ml of activity. The present study showed that the latex microspheres were successfully applied to enzymatic synthesis of glycoside.

• Bulletin of the Korean Chemical Society
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• v.33 no.7
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• pp.2181-2186
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• 2012

Dendrimers are a novel class of nonlinear polymers and due to their extensive applications in different fields, called versatile polymers. Polyamidoamine (PAMAM) dendrimers are one of the most important dendrimers that have many applications in nanobiotechnology and industry. Generally aldehyde terminated dendrimers are prepared by activation of amine terminated dendrimers by glutaraldehyde which has two problems, toxicity and possibility of crosslink formation. In this study, novel aldehyde-terminated PAMAM dendrimer was prepared and used for covalent immobilization of trypsin by the aim of finding a special reagent which can prevent crosslinking and deactivation of the enzyme. For this purpose aminoacetaldehydedimethylacetal (AADA) was used as spacer group between aldehyde-terminated PAMAM and trypsin.The findings of this study showed that immobilization of trypsin not only resulted higher optimal temperature, but also increased the thermal stability of the immobilized enzyme in comparison to the free enzyme.

• Journal of Environmental Science International
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• v.11 no.7
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• pp.729-735
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• 2002

In order to examine the inhibition effect of other heavy metal ions on the removal of heavy metal ions by crab shell in aqueous solution, 10 heavy metal ions $(Cr^{3+},\;Cd^{2+},\;Ni^{2+},\;Zn^{2+},\;Hg^{2+},\;Cu^{2+},\;Mn^{2+],\;Fe^{2+},\;Fe^{3+},\;Pb^{2+})$ were used as single heavy metal ions and mixed heavy metal ions, respectively. In single heavy metal ions, $Pb^{2+},\;Cr^{3+},\;Cu^{2+}$ were well removed by crab shell, however, $Cd^{2+},\;Ni^{2+},\;Zn^{2+},\;Mn^{2+}$ were not. The heavy metal removal increased as the increase of covalent index (Xm$^2$r), and the relationship classified heavy metal ions as 2 heavy metal groups $(Fe^{3+},\;Fe^{2+},\;Cu^{2+},\; Cr^{3+},\;Mn^{2+},\;Ni^{2+},\;Zn^{2+}\;group\;and\;Pb^{2+},\;Hg^{2+},\;Cd^{2+}\;group)$. In mixed heavy metal ions, the removals of $Fe^{2+},\;Fe^{3+},\;Pb^{2+},\;Cu^{2+}$ as 0.49 m㏖/g, regardless of the existence of other heavy metal ions, were similar to the result of single heavy metal ions experiment. The removals of $Mn^{2+},\;Cd^{2+},\;Ni^{2+}$ decreased as the existence of other heavy metal ions, however, the removal of $Zn^{2+},\;Cr^{3+},\;Hg^{2+}$ increased.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1935-1937
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• 2003

최근 콜레스테롤 센서는 전극 상에 효소를 고정화 하는 방식을 이용하여 센서의 집적도를 높이는 시도가 이루어지고 있다. 이러한 전극 상의 효소고정화 방식으로 entrapment, cross liking, covalently binding 등이 있다. 본 논문에서는 이러한 효소 고정화 방식-전도성 고분자인 P3MT를 사용하여 entrap시키는 방법과 silanization을 이용한 covalent bonding 시키는 방법-에 따른 전기화학 센서의 감도 특성에 관한 연구를 수행하였다. 전도성 고분자를 사용한 고정화 방법은 cyclic voltammograms으로 scan rate 10 mA/s, potential 0.5-1.3V의 조건하에서 P3MT를 Polymerization하고, 효소 고정화를 위해 chromoampermeter로 potential 0.6V에서 900초 동안 수행하였다. silanization을 이용한 covalent bonding 시키는 방법은 nitric acid로 Pt 전극표면을 산화시키고, APTER로 silanization 공정을 시행하였다. 효소 고정화를 위해 전해질로는 0.1M Phosphate buffer solution을 사용하여 cyclic voltammograms으로 scan rate 50 mA/s 전위 0.0-0.7V의 조건 하에서 수행하였다. 이 결과 전도성 고분자를 이용한 고정화 방법에서의 senstivity가 0.89 ${\mu}A/mM{\cdot}cm^2$이고, silanization을 이용한 효소 고정화 방법에서는 1.51 ${\mu}A/mM{\cdot}cm^2$였다. 이처럼 후자의 방법에서 더 좋은 감도 특성이 나타났다. 따라서, silanization을 이용한 고정화 방법이 센서 제작 방식으로 더 적합하다고 사료된다.

• Journal of Microbiology and Biotechnology
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• v.29 no.4
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• pp.607-616
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• 2019

In this study, functionalized poplar powder (FPP) was used as a support material for the immobilization of enoate reductase (ER) and glucose-6-phosphate dehydrogenase (GDH) by covalent binding. Under optimal conditions, the immobilization efficiency of ER-FPP and GDH-FPP was 95.1% and 84.7%, and the activity recovery of ER and GDH was 47.5% and 37.8%, respectively. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis indicated that FPP was a suitable carrier for enzyme immobilization. ER-FPP and GDH-FPP exhibit excellent thermal stabilities and superior reusability. Especially, ER-FPP and GDH-FPP enable the continuous conversion of 4-(4-Methoxyphenyl)-3-buten-2-one with $NAD^+$ recycling. While the immobilization strategies established here were simple and inexpensive, they exploited a new method for the immobilization and application of ER and its cofactor recycling system.

• Journal of Microbiology and Biotechnology
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• v.31 no.8
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• pp.1183-1189
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• 2021

Autodisplay of a multimeric protein complex on a cell surface is limited by intrinsic factors such as the types and orientations of anchor modules. Moreover, improper folding of proteins to be displayed often hinders functional cell surface display. While overcoming these drawbacks, we ultimately extended the applicability of the autodisplay platform to the display of a protein complex. We designed and constructed a cell surface attachment (CSA) system that uses a non-covalent protein-protein interaction. We employed the high-affinity interaction mediated by an orthogonal cohesin-dockerin (Coh-Doc) pair from Archaeoglobus fulgidus to build the CSA system. Then, we validated the orthogonal Coh-Doc binding by attaching a monomeric red fluorescent protein to the cell surface. In addition, we evaluated the functional anchoring of proteins fused with the Doc module to the autodisplayed Coh module on the surface of Escherichia coli. The designed CSA system was applied to create a functional attachment of dimeric α-neoagarobiose hydrolase to the surface of E. coli cells.