• Korean Journal of Materials Research
• /
• v.32 no.2
• /
• pp.57-65
• /
• 2022

Herein a rich, Se-nanoparticle modified Mo-W₁₈O₄₉ nanocomposite as efficient hydrogen evolution reaction catalyst is reported via hydrothermal synthesized process. In this work, Na₂SeSO₃ solution and selenium powder are used as Se precursor material. The structure and composition of the nanocomposites are characterized by X-ray diffraction (XRD), high-resolution field emission scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), EDX spectrum analysis and the corresponding element mapping. The improved electrochemical properties are studied by current density, and EIS analysis. The as-prepared Se modified Mo-W₁₈O₄₉ synthesized via Na₂SeSO₃ is investigated by FE-SEM analysis and found to exhibit spherical particles combined with nanosheets. This special morphology effectively improves the charge separation and transfer efficiency, resulting in enhanced photoelectric behavior compared with that of pure Mo-W₁₈O₄₉. The nanomaterial obtained via Na₂SeSO₃ solution demonstrates a high HER activity and low overpotential of -0.34 V, allowing it to deliver a current density of 10 mA cm^-2.

• Korean Journal of Food Science and Technology
• /
• v.32 no.1
• /
• pp.161-167
• /
• 2000

The protease produced by a newly isolated Aspergillus wentti from Korean traditional Meju was purified and characterized. The optimal medium composition and culture conditions for maximum protease production were ; bran :1% glucose solution =1 : 1, pH 9.0, $30^{\circ}C$, and 4 days of fermentation. Protease was purified by QAE-Sephadex, SP-Sephadex ion exchange chromatography and Sephadex G-100 chromatography. The specific activity and the purification fold of the purified enzyme were 213 unit/mg protein and 27.3, respectively. The molecular weight of purified protease was found to be 32 kDa by SDS-PAGE. Km and Vmax value's for hammastein milk casein were $3.049{\times}10^{-4}\;M\;and\;151.1\;{\mu}g/min$, respectively. Kinetic parameters showed that the enzyme has higher affinity to casein than isolated soybean protein, hemoglobin and bovine serum albumin. Optimal pH and temperature for reaction of the purified enzyme were 9.0 and $50^{\circ}C$, respectively. The enzyme was stable at pH 4.0-11.0, below $40^{\circ}C$, and the activity was not stimulated by metal ions. 1mM phenylmethylsulfonyl fluoride inhibited the enzyme activity by 98.5%. It means that the enzyme is one of serine protease.

• Journal of Microbiology and Biotechnology
• /
• v.19 no.9
• /
• pp.987-996
• /
• 2009

Aspergillus niger GH1 previously isolated and identified by our group as a wild tannase producer was grown under solid-state (SSC) and submerged culture (SmC) conditions to select the enzyme production system. For tannase purification, extracellular tannase was produced under SSC using polyurethane foam as the inert support. Tannase was purified to apparent homogeneity by ultrafiltration, anion-exchange chromatography, and gel filtration that led to a purified enzyme with a specific activity of 238.14 IU/mg protein with a final yield of 0.3% and a purification fold of 46. Three bands were found on the SDS-PAG with molecular masses of 50, 75, and 100 kDa. PI of 3.5 and 7.1% N-glycosylation were noted. Temperature and pH optima were 600e and 6.0 [methyl 3,4,5-trihydroxybenzoate (MTB) as substrate], respectively. Tannase was found with a $K_M$ value of $0.41{\times}10^{-4}M$ and the value of $V_{max}$ was $11.03{\mu}$moL/min at $60^{\circ}C$ for MTB. Effects of several metal salts, solvents, surfactants, and typical enzyme inhibitors on tannase activity were evaluated to establish the novelty of the enzyme. Finally, the tannase from A. niger GH1 was significantly inhibited by PMSF (phenylmethylsulfonyl fluoride), and therefore, it is possible to consider the presence of a serine or cysteine residue in the catalytic site.

• Korean Journal of Food Science and Technology
• /
• v.52 no.1
• /
• pp.103-108
• /
• 2020

Shiga toxin-producing Escherichia coli (STEC) is an important pathogenic bacteria and can cause severe foodborne disease. For STEC detection, conventional culture methods have disadvantages in the fact that conventional culture takes a long time to detect and PCR can also detect dead bacteria. To overcome these problems, we suggest a bacteriophage amplification assay, which utilizes the ability of bacteriophages to infect living cells and their high specificity. We used a combination of six bacteriophages infecting E. coli to make the bacteriophage cocktail and added ferrous ammonium sulfate as a virucidal agent to remove free-bacteriophages. When cherry tomato and paprika were artificially inoculated with the cocktail at a final concentration of around 3 log CFU/mL and were enriched for at least 5 h in mTSB broth with Novobiocin, approximately 2-3 log PFU/mL were detected through the bacteriophage amplification assay. Therefore, bacteriophage amplification assay might be convenient and a useful method to detect STEC in a short period of time.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.133.1-133.1
• /
• 2014

이 발표에서 우리는 수백 나노미터 크기인 두 개의 나노 금속 원반 또는 나노 블록이 백 나노미터 이하의 간격으로 결합된 초미세 이중 금속 플라즈몬 광공진기를 제안하고 그 응용을 살펴본다. 원반구조 경우, 반지름이 476 nm인 나노원반 두 개가 100 nm 두께의 유전체 원반의 양쪽에 위치하여 1550 nm 공진파장을 가진 표면 플라즈몬 whispering-gallery-mode (WGM)을 유전체 내에 형성한다. 유전체의 두께를 일정하게 유지할 경우, WGM의 공진파장은 원반의 반지름에 따라 줄어든다. 반면, 반지름이 일정할 때에는 두 금속 원반 사이의 유전체 두께가 줄어듦에 따라 두 금속 원반 사이에 작용하는 표면 플라즈몬의 결합이 강해져서 공진파장이 길어진다. 따라서, 일반적으로 공진기의 크기가 줄어듦에 따라 공진파장이 짧아지는 것과 달리, 제안된 원반구조에서 발생하는 WGM는 원반의 반지름과 유전체의 두께를 함께 줄여도 공진파장이 동일하게 유지되는 차별화된 특성을 가지고 있다. 최종적으로 같은 공진파장을 가지는 WGM를 반지름 88 m, 유전체 두께 10 nm의 공진기에서도 여기시킬 수 있음으로, 모드부피(V)를 1/160으로 줄일 수 있다. 이에 비해, 공진모드의 품위값(Q)은 증가된 금속의 흡수손실에 의해 1/3정도 줄어듦으로써, 공진기와 물질의 상호작용 정도를 보여주는 Q/V값은 크기가 줄어든 공진기에서 오히려 50배 가량 증가함을 확인할 수 있다. 이 같은 초미세 플라즈몬 공진기는 매우 작은 굴절율 센서로서 응용을 가지고 있으며, 1160 nm/(단위 굴절율 변화)의 높은 민감도를 보인다. 한편, $200{\times}150{\times}100nm3$의 크기를 가진 두 개의 금속 나노블록이 10 nm의 공기 간격을 가지고 결합된 나노 공진기는, 공기 간격 내에 강하게 집적된 838 nm의 공진파장을 가진 플라즈몬 공진기 모드를 여기시킨다. 제안된 공진모드는 공기간격이 줄어듦에 따라 공진파장이 급격하게 증가하는 특성을 가지므로 옹스토롬 정도의 분해능을 가진 두께 변화 센서로 응용할 수 있다. 예를 들어, 공기간격 2 nm에서는 1A 두께 변화에 대해 공진파장 변화는 약 40 nm로 매우 민감하게 변화한다.

• Biomolecules & Therapeutics
• /
• v.19 no.1
• /
• pp.126-133
• /
• 2011

The fruit of Actinidia arguta (AA) has been used mainly for the treatment of skin diseases, diuresis, diabetes mellitus and osteoporosis in Korean traditional medicine. It is known that AA (hardy kiwi) fruit extract has an effect on 2-chloro-1,3,5-trinitrobenzene-induced atopic dermatitis-like skin lesions in NC/Nga mice. Mode of action for it is associated with the modulation of biphasic Th1/Th2 cytokines. Furthermore, DA9102 containing AA is a herbal medicine currently under phase II clinical trial for atopic dermatitis in Korea. However, no active principles of AA on the decrease of Th2 cytokines including IL-4 and IL-10 have been identified. In this study, bioactivity-guided fractionation of an alcohol extract from the dried fruits of AA using ELISA assay for IL-4 production led to the isolation of $\alpha$-linolenic acid (I), linoleic acid (II), ethyl linolenate (III), ethyl linoleate (IV) and ethyl stearate (V) as the major active components. These compounds showed the down-regulatory effects of IL-4 production in A23187-stimulated RBL-2H3 cells without cytotoxicity.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
• /
• 2001.04a
• /
• pp.18-25
• /
• 2001

A new wood-degrading fungus Trichophyton rubrum LKY-7 secretes a high level of laccase in a glucose-peptone liquid medium. The production of laccase by the fungus was barely induced by 2,5-xylidine. The laccase has been purified to homogeneity through three chromatography steps in an overall yield of 40%. The molecular mass of the purified laccase was about 65 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The purified laccase had the distinct blue color and had basic spectroscopic features of a typical blue laccase: two absorption maxima at 278 and 610 nm and a shoulder at 338 nm. The N-terminus of the laccase has been sequenced, revealing high homology to laccases from wood-degrading white-rot fungi such as Ceriporiopsis subvermispora. The enzyme had a "low" redox potential (0.5 V vs normal hydrogen electrode), yet it was one of the most active laccases in oxidizing a series of representative substrates/mediators. Compared with other fungal laccases, the laccase has a very low Km value with ABTS [2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid] as a substrate and a very high Km value with violuric acid as a substrate. The laccase has the isoelectric point of 4.0. The laccase had very acidic optimal pH values (pH 3-4) while it was more stable at neutral pH than at acidic pH. The laccase oxidized hydroquinone faster than catechol and pyrogallol. The oxidation of tyrosine by the laccase was not detectable under the reaction conditions. The laccase was strongly inhibited by sodium azide and sodium fluoride. fluoride.

• YAKHAK HOEJI
• /
• v.41 no.5
• /
• pp.615-621
• /
• 1997

Dehydropeptidase-I (DHP-I) was solubilized from porcine kidney by treatment with n-butanol and partially purified 19.25 fold by $(NH_4)_2SO_4$ precipitation, DEAE-Sepharose CL-6B ion exchange chromatography and Sephacryl S-300 HR chromatography with an overall yield of 19.16. DHP-I showed its optimal activity at pH 7.5 and 25$^{\circ}C$. Its activity was stable under neutral and alkaline conditions, but was disappeared under acidic condition. And DHP-I was heat-labile and its activity remained at 45$^{\circ}C$ for 3hrs. The enzyme was not inhibited by dicationic ions, while its activity was increased by $Co^{2+}$(1mM) and $Zn^{2+}$ (0.1mM). The enzyme was inhibited by EDTA and N-ethylmaleimide. The relative molecular mass of DHP-I was estimated to be approximately 100kDa by gel filtration chromatography. The $K_m$ value of DHP-I for glycyldehydrophenylalanine (GDHP) was 1.98mM. DWP20418 [(1R, 5S, 6S)-6-[1-(R)-Hydroxyethyl]-1-methyl-2-[(2S, 4S)-2-(piperazinylcarbonyl)-1-(R)-hydroxyethyl)pyrrolidine-4-thio]carbapen-2-em-3-carboxylic acid], compared with meropenem (MEPM), was rather easily hydrolized by DHP-I, while it was four times more resistant than imipenem (IPM) to DHP-I.

• Journal of Microbiology and Biotechnology
• /
• v.21 no.3
• /
• pp.256-262
• /
• 2011

A 20.9-kDa metalloprotease was isolated from dried fruiting bodies of the wild basidiomycete mushroom Lepista nuda. The N-terminal amino acid sequence of the protease was seen to be ATFVLTAATNTLFTA, thus displaying no similarity with the sequences of previously reported metalloproteases. The protease was purified using a procedure that entailed ion-exchange chromatography on CM-Cellulose, Q-Sepharose, and Mono S, and FPLC-gel filtration on Superdex 75. The protease functioned at an optimum pH of 7.0 and an optimum temperature of $50^{\circ}C$. It was also noted that the protease demonstrated a proteolytic activity of 1,756 U/mg toward casein. The $K_m$ of the purified protease toward casein was 6.36 mg/ml at a pH of 7.0 and with a temperature of $37^{\circ}C$, whereas the $V_{max}$ was 9.11 ${\mu}g\;ml^{-1}\;min^{-1}$. The activity of the protease was adversely affected by EDTA-2Na, suggesting that it is a metalloprotease. PMSF, EGTA, aprotinin, and leupeptin exerted no striking inhibitory effect. The activity of the protease was enhanced by $Fe^{2+}$, but was curtailed by $Cd^{2+}$, $Cu^{2+}$, $Hg^{2+}$, $Pb^{2+}$, $Zn^{2+}$, and $Fe^{2+}$ ions. The protease also exhibited inhibitory activity against HIV-1 reverse transcriptase with an $IC_{50}$ value of 4.00 ${\mu}M$. The $IC_{50}$ values toward hepatoma Hep G2 and leukemia L1210 cells in vitro were 4.99 ${\mu}M$ and 3.67 ${\mu}M$, respectively.

• Journal of Microbiology and Biotechnology
• /
• v.21 no.7
• /
• pp.734-738
• /
• 2011

Streptococcus pneumoniae is a major cause of invasive infection in young infants and older adults. There are currently 90 capsular serotypes identified and 23 serotypes (1, 2, 3, 4, 5, 6B, 7F, 8, 9N, 9V, 10A, 11A, 12F, 14, 15B, 17F, 18C, 19F, 19A, 20, 22F, 23F, and 33F) are responsible for about 90% of invasive disease. Among the more than 90 different S. pneumoniae serotypes, serotype 19A is globally very prevalent. A simplified purification procedure including adjustment of cell lysate pH to 4.5, fractionation with 50. 80% ethanol, and dialysis rendered capsular polysaccharide (CPS) in a yield of $31.32{\pm}3.11$ mg from 1 l culture (75% recovery after lyses). The product contained only 69.6 ${\mu}g$ of protein (99.78% purity) and 0.8mg (sum of the precipitants from 50~60%, 60~70%, and 70~80%) of nucleic acid (97.45% purity). The purified CPS was conjugated with bovine serum albumin; the product size ranged from 100 to 180 kDa.