• Title/Summary/Keyword: structural reaction

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Overproduction, Purification, and Characterization of Heat Stable Aldolase from Methanococcus jannaschii, a Hyperthermophic Archaea

  • Choi, In-Geol;Cho, Chun-Seok;Cho, Yun-Je;Yu, Yeon-Gyu
    • BMB Reports
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    • v.31 no.2
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    • pp.130-134
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    • 1998
  • An aldolase gene has been cloned from Methanococcus jannaschii. The coding region of the gene has been expressed in E. coli using a pET system to a level of 30% of total cellular proteins. The protein was purified to more than 95 % homogeneity by heat treatment and ion exchange chromatography. The protein performed an aldol condensation reaction with glyceraldehyde as substrate and dihydroxyacetone phosphate as a carboxyl donor. The protein was determined to be a type II aldolase which requires the $Zn^{2+}$ ion as a metal cofactor. This enzyme has a broad range of optimum pH (7-9) and temperature ($50-80^{\circ}C$). It shows strong stability against heat, chemical denaturants, as well as a high percentage' of organic solvents. The half-life of this enzyme at $85^{\circ}C$ is more than 24 h and it maintains more than 90% of aldolase activity in the presence of 6 M urea, 50% acetonitrile, or 15% isopropyl alcohol.

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Three Common Subunits in Editing Domains of Class Ia tRNA Synthetases

  • Lee, Keun-Woo;Kwon, Yong-Jung;Briggs, James M.
    • Bulletin of the Korean Chemical Society
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    • v.28 no.2
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    • pp.207-210
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    • 2007
  • To identify structural or functional common subunit(s) in the CP1 (editing) domains of class Ia tRNA synthetases, five available structures were compared and analyzed. Through the sequence alignments and structural overlapping of the CP1 domains, three conserved regions were identified near the amino acid binding site in the editing domain. Structural overlapping of the three subunits clearly showed the existence of three common structural subunits in all of the five editing RS structures. Based on the established experimental results and our modeling results, it is proposed that subunits 1 and 3 accommodate the incoming amino acid binding, while subunit 2 contributes to the interactions with the adenosine ring of the A76 to stabilize the overall tRNA binding. Since these subunits are critical for the editing reaction, we expect that these key structures should be conserved through the most class Ia editing RSs.

Mechanical Properties and Reaction Products of Activated Slag System Depending on Gypsum Presence and Calcium Carbonate Addition (석고 존재 및 탄산칼슘 첨가에 따른 활성 슬래그의 역학적 성능 및 반응생성물)

  • Jeong, Yeonung;Lim, Gwi Hwan;Park, Su Hyeon;Kim, Joo Hyung;Kim, Tae-Sang
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.24 no.4
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    • pp.55-63
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    • 2020
  • This study investigates the mechanical properties and reaction products of activated slag pastes depending on gypsum presence and calcium carbonate addition in terms of compressive strength tests and synchrotron X-ray diffraction. The chemicals of CaO and NaOH are used as activators with different two dosages. The reaction of CaO-activated slag without gypsum just accelerated by addition of calcium carbonate at early ages, but no improvement was observed at later ages. On the other hand, the mechanical properties of CaO-activated slag pastes with gypsum were improved with calcium carbonate, enhancing the stability of ettringite. The variation of mechanical properties of NaOH-activated slag pastes was negligible depending on calcium carbonate addition in case of no gypsum. The addition of calcium carbonate into NaOH-activated slag pastes with gypsum deteriorated its mechanical properties due to the ion competition between CO32- ions and SO32- ions, decreasing crystallinity of reaction products.

Effect of Crystal Structural Environment of Pr3+ on Photoluminescence Characteristics of Double Tungstates

  • Lee, Kyoung-Ho;Chae, Ki-Woong;Cheon, Chae-Il;Kim, Jeong-Seog
    • Journal of the Korean Ceramic Society
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    • v.48 no.2
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    • pp.183-188
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    • 2011
  • In this article, the effect of the crystal structural environment of $Pr^{3+}$ ions on the photoluminescence (PL) characteristics of double tungstates, such as $A(M_{1-X}Pr_X)W_2O_8$ (A=Li, Cs, M = In, Y, Sc, La; $0.007{\leq}x{\leq}0.1$) and $La_{1.96}Pr_{0.04}W_3O_{12}$ are characterized. By varying the ion radius in A and M sites, the structural environment of $Pr^{3+}$ ions were modified. The structural criteria, that is, the point charge electrostatic potentials V around the $Pr^{3+}$ activator, were calculated using the crystal structural parameters. The point charge potential V can be a valid criterion for $^3P_o$ quenching in various double tungstates. When the calculated V values are large (> 6.0), the luminescence from the $^3P_0$ level becomes dominant. When the calculated V values are about 3.8, the $^1D_2$ line appears weakly but $^3P_0$-level luminescence is absent. When the calculated V values are small (< 2.0), the luminescence from the $^1D_2$ level becomes dominant and $^3P_0$-level luminescence is absent. At 2.0$^3P_o$ quenching to $^1D_2$ level occurs substantially in accordance with the structural criterion of the point charge potential model.

A Study on the Effect of Soil Properties on Structural Behavior of Fixed Jacket Type Offshore Structure (고정식 자켓형 해양구조물의 지반 물성치에 따른 구조 응답에 관한 연구)

  • Han, Sangwoong;Lee, Kangsu;Jang, Beom-Seon;Choi, Junhwan
    • Journal of the Society of Naval Architects of Korea
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    • v.55 no.5
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    • pp.438-447
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    • 2018
  • For a fixed jacket type offshore structure directly supported by the seabed, the structural behavior of offshore structure depends on the soil properties. Soil properties affect on the stiffness of the piles and the boundary condition in the structural analysis. The structural analysis is performed using PSI (Pile-Soil Interaction) suggested in the code and design rule. PSI analysis of the jacket structure is carried out after various soil types are selected according to the soil properties like internal friction angle, undrained shear strength, unit weight and so on. Three types of soil are selected by varying strength for a clay and sand, respectively. The structural analysis of the jacket structure is performed using these soils. The results about axial and lateral reaction force and the stress and displacement on the structure are compared. As a results, the structural response is smaller as the soil becomes more stiff. In conclusion, it is confirmed that the structural response of fixed jacket type offshore platform supported by seabed is sensitive to the change of soil properties.

Effects of W Contents in Co Matrix of the Thermal Sprayed WC-Co on the Corrosion Behavior in Molten Zinc

  • Seong, Byeong-Geun;Hwang, Sun-Young;Kim, Kyoo-Young;Lee, Kee-Ahn
    • Corrosion Science and Technology
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    • v.6 no.4
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    • pp.147-153
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    • 2007
  • This study sought to investigate the reaction of Co-binder containing tungsten with molten zinc. Four kinds of Co-W alloys (pure, 10%W, 20%W, 30%W) were prepared using the powder metallurgy method. The specimens were immersion-tested in molten pure zinc baths at $460^{\circ}C$. To evaluate the corrosion property in molten zinc, the weight loss of the specimen was measured after the immersion tests at different immersion times (10~300 min.). Co-10%W alloys, compared with pure cobalt, showed no effect of tungsten addition on the reaction rate in molten zinc. The relationship between the weight loss and the square root of immersion period represents a straight line in both pure cobalt and Co-10%W alloy. The Co-Zn reaction layer in Co- 1O%W alloy consists of $\gamma2$, $\gamma1$, $\gamma$ and ($\beta1$ phases. The rate of weight loss significantly increases and the weight loss behavior is not well accord with the linear relationship as the tungsten content in the Co-W alloy increases. The $\beta1$ layer was not formed on the Co-20%W alloy and neither was a stable Co-Zn intermetallic compound layer found on the Co-30%W alloy. The main cause of increase in reaction rate with increasing tungsten content is related with the instability of the Co-Zn reaction phases as seen on micro-structural analysis.

The Effct of SHS Reaction Heat Control on the Microstructure of TiAl (고온 자전 합성시 반응열 제어가 TiAl 미세 조직에 미치는 영향에 관한 연구)

  • Mun, Jong-Tae;Yeom, Jong-Taek;Sin, Bong-Mun;Kim, Yong-Seok;Lee, Yong-Ho
    • Korean Journal of Materials Research
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    • v.5 no.7
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    • pp.869-879
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    • 1995
  • TiAi intermetallic compound has been extensively studied for possible high temperature structural applications because of its high specific strength at high temperature, high creep resistance, and good oxidation resistance at elevated temperatures. In addition to its good properties, an economic manufacturing routes should be developed for this material to be used more extensively. One of the promising route in manufacturing TiAl intermetallics is the Self-propagating High-temperature Synthesis (SHS) method. Thus in this study, an attempt was made to study the mechanism of the SHS process in TiAl synthesis. The composition of the sample was Ti-(45, 50, 53)at% Al and the microstuctures of the products were analyzed using optical microscope and scanning electron microscope. When the phases formed at the main SHS reaction of whicyh combustion temperature is higher than the melting temperature of aluminum were identified as TiAl and Ti$_3$Al ; Ti$_3$Al cores surrounded by TiAl phase. In order to increase the combustion temperature, carbon was added 5 and 10at.%. When the carbon content was 10at.%, the heat of the reaction was large enough to melt the phase formed and that is consistent with the theoretical calculation results of the adiabatic temperature. The combution temperatue, which was measured by a computer data acquisition system, increased with the carbon content. The phases formed from the reaction involving the carbon added were indentified as TiAl and Ti$_2$AlC using XRD. The vickers hardness of the reaction product increased with the carbon content.

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Structural and Thermal Characteristics of Synthesized SiC by Carbothermal Reaction and Sol-gel Method (Carbothermal 반응법과 졸-겔법에 의해 합성된 SiC의 구조적 특성과 열역학적 특성)

  • Oh, Won-Chun;Kim, Bum-Soo
    • Analytical Science and Technology
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    • v.11 no.3
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    • pp.156-160
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    • 1998
  • SiC is synthesized by sol-gel and carbothermal reaction method from various carbon sources and Si source and characterized through the results of DSC and XRD. More SiC has been formed in carbothermal reaction than sol-gel method. From the XRD results, the degree of formation of SiC increases in the order of petroleum cokes, activated carbon, artificial graphite all in two introduced methods. Based on the DSC data, the enthalpy values for the exothermic reaction decrease in the order of activated carbon, petroleum cokes, artificial graphite in carbothermal reaction methods, while those for the endothermic reactions increase in the reverse order. But, the enthalpy values for the exothermic reactions decrease in the order of petroleum cokes, activated carbon, artificial graphite in sol-gel methods.

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Structural Characteristics of Novel Branched Oligosaccharides Syntesized by a Maltose Acceptor Reaction with Dextransucrase from Leuconostoc mesenteroides M-12 (Leuconostoc mesenteroides M-12 덱스트란수크라제의 말토스 억셉터 반응으로 합성된 새로운 분지 올리고당의 구조 특성)

  • 서현창
    • The Korean Journal of Food And Nutrition
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    • v.10 no.1
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    • pp.102-109
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    • 1997
  • The structures of novel branched oligosaccharides synthesized by the acceptor reaction with dextransucrase from Leuconostoc mesenteriodes M-12 were proposed in accordance with the results obtained from enzymatic hydrolyses and a partial acid hydrolysis. The structure of branched oligosaccharide B4 was shown to be 62-O-$\alpha$-D-kojibiosylmaltose. Branched oligosaccharide B5 was shown to be 63-O-$\alpha$-D-kojibiosylpanose. By reacting the acceptor reaction products with endodextranase a novel branched oligosaccharide (D4) could be produced. D4 was derived from the result of endodextranase hydrolysis of oligosaccarides synthesized by the second acceptor reaction with dextransucrase and was resistant to endodextranase and glucoamylase. The proposed structure of D4 was 62-O-$\alpha$-D-kojibiosylisomaltose. Formation pattern of the acceptor reaction products smaller than d.p. 6 with linear or branched linkage was also shown.

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The Effects of Servicescape, Brand Reputation and Experiences on Brand Attitude and Loyalty in Korean Restaurants (한식레스토랑의 서비스스케이프, 브랜드명성 및 체험유형이 브랜드태도와 충성도에 미치는 영향)

  • Lee, Na-Rae;Ha, Dong-Hyun
    • Culinary science and hospitality research
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    • v.19 no.3
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    • pp.173-193
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    • 2013
  • This study was conducted to investigate the effects of servicescape factors(space, convenience, aesthetics, comfortableness, cleanliness), brand reputation and experiences factors(feel, think, act, relate) on emotional and cognitive reactions of visitors to Korean restaurants. It also investigated the relationship between emotional and cognitive reactions and brand loyalty. A total of 353 questionnaires were analyzed using the factor analysis, a reliability test, and structural equation modeling analysis. The results revealed that space, aesthetics and comfortableness were positively related to emotional reaction, and convenience and cleanliness were related to cognitive reaction. This study also found that brand reputation was positively related to emotional and cognitive reactions. Moreover, it was found that think was positively related to emotional reaction, and feel, think, act and relate were positively related to cognitive reaction. Finally, cognitive reaction was positively related to loyalty. Therefore, Korean restaurant marketers should introduce or strengthen servicescape, brand reputation and experiences, which increases brand attitude or loyalty.

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