• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.243-249
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• 2014

Three single crystals of fully dehydrated $Co^{2+}$-exchanged zeolite Y (Si/Al = 1.56) were prepared by the exchange of $Na_{75}$-Y ($|Na_{75}|[Si_{117}Al_{75}O_{384}]$-FAU) with aqueous streams 0.05 M in $Co(NO_3)_2$, pH = 5.1, at 294 K for 6 h, 12 h, and 18 h, respectively, followed by vacuum dehydration at 673 K. Their single-crystal structures were determined by synchrotron X-ray diffraction techniques in the cubic space group Fd3m at 100(1) K. They were refined to the final error indices $R_1/wR_2$ = 0.0437/0.1165, 0.0450/0.1228, and 0.0469/0.1278, respectively. Their unit-cell formulas are $|Co_{29.1}Na_{11.8}H_{5.0}|[Si_{117}Al_{75}O_{384}]$-FAU, $|Co_{29.8}Na_{11.0}H_{4.4}|[Si_{117}Al_{75}O_{384}]$-FAU, and $|Co_{30.3}Na_{9.5}H_{4.9}|[Si_{117}Al_{75}O_{384}]$-FAU, respectively. In all three crystals, $Co^{2+}$ ions occupy sites I, I' and II; $Na^+$ ions are also at site II. The tendency of $Co^{2+}$ exchange slightly increases with increasing contact time as $Na^+$ content and the unit cell constant of the zeolite framework decrease.

• Journal of Applied Biological Chemistry
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• v.52 no.3
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• pp.109-115
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• 2009

The gene encoding a putative aspartate aminotransferase in Xanthomonas oryzae pv. oryzae (Xoo) was cloned using PCR technique. The gene was ligated with pET-21(a) vector containing His6 tag and expressed in E. coli BL21(DE3). Affinity purification of the recombinant aspartate aminotransferase with Ni-NTA resin resulted in one band by SDS-PAGE analysis. The purified enzyme showed a molecular weight of 43 kDa, as expected. The enzyme was the most active toward L-aspartate as an amino donor, indicating that the purified enzyme is one of aspartate aminotrans-ferases exist in Xoo. Optimal activity of the enzyme was observed at around pH 7.5 and stability was much higher at alkaline pH rather than acidic pH values. The enzyme was considerably activated by the presence of manganese ion, showing about 157% of control activity at 1.0 mM.

• Bulletin of the Korean Chemical Society
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• v.34 no.12
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• pp.3835-3839
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• 2013

A new synthesis route for Pt nanoparticles by direct electrochemical reduction of a solid-state Pt ion precursor ($K_2PtCl_6$) is demonstrated. Solid $K_2PtCl_6$-supported polyethyleneimine (PEI) coatings on the surface of glassy carbon electrode were prepared by simple mixing of solid $K_2PtCl_6$ into a 1.0% PEI solution. The potential cycling or a constant potential in a PBS (pH 7.4) medium were applied to reduce the solid $K_2PtCl_6$ precursor. The reduction of Pt(IV) began at around -0.2 V and the reduction potential was ca. -0.4 V. A steady state current was achieved after 10 potential cycling scans, indicating that continuous formation of Pt nanoparticles by electrochemical reduction occurred for up to 10 cycles. After applying the reduction potential of -0.6 V for 300 s, Pt nanoparticles with diameters ranging from $0.02-0.5{\mu}m$ were observed, with an even distribution over the entire glassy carbon electrode surface. Characteristics of the Pt nanoparticles, including their performance in electrochemical reduction of $H_2O_2$ are examined. A distinct reduction peak observed at about -0.20 V was due to the electrocatalytic reduction of $H_2O_2$ by Pt nanoparticles. From the calibration plot, the linear range for $H_2O_2$ detection was 0.1-2.0 mM and the detection limit for $H_2O_2$ was found to be 0.05 mM.

• Korean Journal of Agricultural Science
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• v.39 no.2
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• pp.255-261
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• 2012

A bacterium AB-55, isolated from waste mushroom bed of Agaricus bisporus in Sukseong-myeon, Buyeo-gun, Chungcheongnam-do, Korea, was screened onto xylan agar congo-red plate by the xylanolysis method and was used to produce an xylanase in shaker buffle flask cultures containing oat spelt xylans. The phylogenetic analysis using 16S rRNA gene sequence data showed that the strain AB-55 had the highest homology (99.0%) with Bacillus subtilis and it was named as Bacillus subtilis AB-55. A xylanase was purified by ammonium sulfate precipitation (50~80%), gel filtration on sephacryl S-300, and ion exchange chromatography on DEAE sepharose FF. The molecular weight of the xylanase was estimated as 44 kDa by SDS-PAGE. Optimal pH and temperature for the xylanase activity was pH 7 and $50^{\circ}C$, respectively. N-terminal amino acid sequence of the enzyme was identified as Ser-Ala-Val-Lys-His-Gly-Ala-Ile-Val-Phe. The substrate specificity of the enzyme exhibited that it hydrolyzed efficiently oat spelt xylan as well as beechwood xylan, but showed no activity against Avicel and carboxymethyl clellulose (CMC). The enzyme activity was enhanced by $Fe^{2+}$ and $Mn^{2+}$ whereas was entirely inhibited by $Hg^+$.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1994.04a
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• pp.279-279
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• 1994

Fibrinolytic proteases, piscivorase I (PI) and piscivorase II (PII), were isolated from Agkistrodon piscivorus piscivorus (eastern cotonmouth moccasin) venom using gel filtration on Bio-Gel P100 and ion-exchange chromatography on CM-Sepharose. The molecular welghts of two proteases were approximately 23400 and 29000. Their isoelectric points 6.6 and 8.5, respectively. The partial amino acid sequences of PI were characterized by tryptic digestion. PI readily cleaves the A${\alpha}$-and B${\beta}$-chaln of fibronogen, but PII rapidly cleaves A${\alpha}$-chain and more slowly the B${\beta}$-chain, They were activated by Ca$\^$2+/, Mg$\^$2+/ and Ba$\^$2+/, but inhibited by Zn$\^$2+/, Cu$\^$2+/ and Mn$\^$2+/. Two enzymes were also inhibited by cysten, ${\beta}$-mercapto -ethanol, and by metal chelators such as EDTA and EGTA, but not by benzamidine, PMSF, soybean trypsin inhibitor and aprotinin. They did not act like thrombin, plasmin and kallikrein, using specific chromogenllc substrates. Two protease did not induce platelet aggregation. PI showed low hemorrhagic activity at dosage of 50 $\mu\textrm{g}$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.6
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• pp.444-448
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• 2010

Based on first-principles calculations, we study the magnetic properties of Co, Ni, Fe, V, and Mn impurities in ZnO. The stabilities of the ferromagnetic state and the magnetic moment of each impurity largely depend on the amount of doped electron or hole. For lightly doped n-type ZnO, it is found that the doping of Ni ions is the most effective for inducing ferromagnetism, while Fe ions show the most stable ferromagnetic couplings for heavily doped n-type samples. The characteristics of the magnetic interactions of Co ions are similar with those of Fe ions, but Co ions require much larger amount of doped electron than Fe ions to show the ferromagnetic couplings. The ferromagnetic coupling between Mn and V ions is unstable in n-type conditions.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.528-528
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• 2012

Recently, atmospheric pressure plasmas attract lots of interests for the useful applications such as surface modification and bio-medical treatment. In this study, a particle-in-cell Monte Carlo collision (PIC-MCC) simulation was adopted to investigate the discharge characteristics of a planar micro dielectric barrier discharge (DBD) with a driving frequency from 13.56 MHz to 162.72 MHz and with a gap distance of 80 micrometers. The variation of frequency, in the change in the electron energy probability function (EEPF). Through the relation between the ion trajectories and the frequency, results in the change of EEPFs is achievable with the turning point of frequency mode. Therefore, it is possible to categorize the efficient operation range of DBDs for its applications by controlling the interactions between plasmas and neutral gas for the generation of preferable radicals.

• Microbiology and Biotechnology Letters
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• v.23 no.4
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• pp.411-415
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• 1995

The dextranase (EC 3.2.1.11) produced by Aspergillus ustus GR-98 was purified by the following sequential methods; salting-out and dialysis, gel filtration on BIO-GEL P-100, ion exchange chromatography on DEAH-cellulose, affinity chromatography on hydroxyapatite, and preparative electrophoresis. Three active fractions, dextranases 1, 11 and 111, were isolated in electrophoretically pure states, and specific activities of the dextranases were 1,276, 1,154 and 1,125 units/mg, the degrees of yield were 9.0, 3.6 and 2.2%, having 145, 131.1 and 127.8 times as those of culture filtrate in degree of purification, respectively. The enzyme purity was confirmed by the PAGE, SDS-PAGE and get permeation-HPLC.

• Journal of Microbiology
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• v.41 no.4
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• pp.345-348
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• 2003

The bio-mediated production of calcite crystals by calcinogenic bacteria has great applicable value for the restoration of deteriorated calcareous monuments, because of its high purity and coherency. An investigation of the conditions for calcite production by an alkalophilic Bacillus amyloliquefaciens CMB01 strain was made. Optimal calcite precipitation occurred when the bacterium was cultured at pH 8.0 and 30$^{\circ}C$, and in B4 medium that consisted of 0.4% yeast extract, 0.5% glucose, and 1.5% calcium acetate. Calcium ion of the bacterially induced calcite was analyzed by an inductively coupled plasma (ICP) spectrophotometer. Optical and scanning electron microscopy (SEM) of the calcite revealed a typical rombohedral polycrystalline structure.

• The Korean Journal of Food And Nutrition
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• v.7 no.2
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• pp.128-136
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• 1994

Mackerel muscle protein hydrolysates, which were prepared from defatted mackerel meal by proteases such as complex enzyme, alcalase, bromelain, pancrease, pepsin, w-chymotrypsin, trypsin and papain, were tested for the antioxidative action against linoleic acid. Among proteases tested, the hydrolysates obtained from the treatment of complex enzyme, bromelain and alcalase showed higher antioxidative effects. Also, the hydrolysates showed the synergistic effects with o-tocopherol and the inhibitory effects for peroxidation of metal ions(Fe3+, Cua+) From the profiles of fractionation of the hydrolysates with Bio-gel P-2 column, the most active fractions, part I(complex enzyme-derived) and part e(bromelain-derived), had below MW 1,400 and the antioxidative effects were closely related to the binding capacity with metal ion(Cua+). Amno acid composition of the part I was abundant in histidine, arginine, phenylalanine and lysine, and the part e was abundant in lysine, glutamic acid and leucine.