• Title/Summary/Keyword: $C_5$-precursor

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Biosynthesis of Chondroitin in Engineered Corynebacterium glutamicum

  • Cheng, Fangyu;Luozhong, Sijin;Yu, Huimin;Guo, Zhigang
    • Journal of Microbiology and Biotechnology
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    • v.29 no.3
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    • pp.392-400
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    • 2019
  • Chondroitin, the precursor of chondroitin sulfate, which is an important polysaccharide, has drawn significant attention due to its applications in many fields. In the present study, a heterologous biosynthesis pathway of chondroitin was designed in a GRAS (generally recognized as safe) strain C. glutamicum. CgkfoC and CgkfoA genes with host codon preference were synthesized and driven by promoter Ptac, which was confirmed as a strong promoter via GFPuv reporter assessment. In a lactate dehydrogenase (ldh) deficient host, intracellular chondroitin titer increased from 0.25 to 0.88 g/l compared with that in a wild-type host. Moreover, precursor enhancement via overexpressing precursor synthesizing gene ugdA further improved chondroitin titers to 1.09 g/l. Chondroitin production reached 1.91 g/l with the engineered strain C. glutamicum ${\Delta}L-CgCAU$ in a 5-L fed-batch fermentation with a single distribution $M_w$ of 186 kDa. This work provides an alternative, safe and novel means of producing chondroitin for industrial applications.

A study on the preparation and analysis of cordierite by sol-gel method (졸-겔법에 의한 코디어라이트 제조와 분석에 관한 연구)

  • Chun, Kyung Soo;Lee, Young Hwan
    • Analytical Science and Technology
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    • v.21 no.2
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    • pp.123-128
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    • 2008
  • The golden turbid solution of cordierite precursor was obtained by using magnesium ethoxide in sol-gel method, while the clear solution of cordierite precursor was obtained when 5%-$Zr(OC_3H_7)_4$ solution was used in the sol-gel reaction. $SiO_2$ component was confirmed by infrared spectra showing $1045cm^{-1}$ and the stretching vibration of gelish $SiO_4$ showed $1140cm^{-1}$ and $940cm^{-1}$. The component of $Al_2O_3$ showed at $580cm^{-1}$ and network structure of $Al_2O_6$ showed at $680cm^{-1}$. The component of MgO was confirmed at $575cm^{-1}$ as the stretching vibration. X-ray diffraction analysis showed ${\mu}$-cordierite crystal was showed up at temperature above $1000^{\circ}C$ at the mole ratio of cordierite precursor and water (1:5). ${\mu}$-Cordierite and ${\alpha}$-cordierite were coexisted at $1050^{\circ}C$ for the mole ratio of cordierite precursor and ammonia (1:5) while ${\alpha}$-cordierite was only existed at $1100^{\circ}C$ for the same mole ratio as mentioned above.

Multi-coated YBa2Cu3O7-x Films Fabricated by a Fluorine-Free Sol-Gel Process

  • Cho, E.A.;Jang, G.E.;Hyun, O.B.
    • Journal of Magnetics
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    • v.16 no.2
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    • pp.186-191
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    • 2011
  • [ $YBa_2C_3O_{7-x}$ ]films were fabricated on a $SrTiO_3$ (100) substrate using a trimethylaceate propionic acid (TMAP)-based MOD process by controlling the precursor solution viscosity, firing temperature, and by using various coatings. The viscosity of the precursor solution was controlled by the addition of Xylenes. The films were heat treated with different temperatures from 750 to $800^{\circ}C$. c-axis oriented films were obtained. After adding 9 ml of Xylene into the precursor solution, the $T_c$ of the YBCO film, which was coated 2 times and heat treated at $800^{\circ}C$, was 86 K and the measured $J_c$ was above 2.5 MA/$cm^2$ at 77 K in a zero-field.

Fabrication and NOx Gas Sensing Properties of LaMeO3 (Me = Cr, Co) by Polymeric Precursor Method (Polymeric Precursor법에 의한 LaMeO3 (Me = Cr, Co)의 제조 및 NOx 가스 검지 특성)

  • Lee, Young-Sung;Shimizu, Y.;Song, Jeong-Hwan
    • Korean Journal of Materials Research
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    • v.21 no.8
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    • pp.468-475
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    • 2011
  • [ $LaMeO_3$ ](Me = Cr, Co) powders were prepared using the polymeric precursor method. The effects of the chelating agent and the polymeric additive on the synthesis of the $LaMeO_3$ perovskite were studied. The samples were synthesized using ethylene glycol (EG) as the solvent, acetyl acetone (AcAc) as the chelating agent, and polyvinylpyrrolidone (PVP) as the polymer additive. The thermal decomposition behavior of the precursor powder was characterized using a thermal analysis (TG-DTA). The crystallization and particle sizes of the $LaMeO_3$ powders were investigated via powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and particle size analyzer, respectively. The as-prepared precursor primarily has $LaMeO_3$ at the optimum condition, i.e. for a molar ratio of both metal-source (a : a) : EG (80a : 80a) : AcAc (8a) inclusive of 1 wt% PVP. When the as-prepared precursor was calcined at $700^{\circ}C$, only a single phase was observed to correspond with the orthorhombic structure of $LaCrO_3$ and the rhombohedral structure of $LaCoO_3$. A solid-electrolyte impedance-metric sensor device composed of $Li_{1.5}Al_{0.5}Ti_{1.5}(PO_4)_3$ as a transducer and $LaMeO_3$ as a receptor has been systematically investigated for the detection of NOx in the range of 20 to 250 ppm at $400^{\circ}C$. The sensor responses were able to divide the component between resistance and capacitance. The impedance-metric sensor for the NO showed higher sensitivity compared with $NO_2$. The responses of the impedance-metric sensor device showed dependence on each value of the NOx concentration.

Growth and Characterization of GaN on Sapphire and Porous SWCNT Using Single Molecular Precursor

  • Sekar, P.V. Chandra;Lim, Hyun-Chul;Kim, Chang-Gyoun;Kim, Do-Jin
    • Korean Journal of Materials Research
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    • v.21 no.5
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    • pp.268-272
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    • 2011
  • Due to their novel properties, GaN based semiconductors and their nanostructures are promising components in a wide range of nanoscale device applications. In this work, the gallium nitride is deposited on c-axis oriented sapphire and porous SWCNT substrates by molecular beam epitaxy using a novel single source precursor of $Me_2Ga(N_3)NH_2C(CH_3)_3$ with ammonia as an additional source of nitrogen. The advantage of using a single molecular precursor is possible deposition at low substrate temperature with good crystal quality. The deposition is carried out in a substrate temperature range of 600-750$^{\circ}C$. The microstructural, structural, and optical properties of the samples were analyzed by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and photoluminescence. The results show that substrate oriented columnar-like morphology is obtained on the sapphire substrate while sword-like GaN nanorods are obtained on porous SWCNT substrates with rough facets. The crystallinity and surface morphology of the deposited GaN were influenced significantly by deposition temperature and the nature of the substrate used. The growth mechanism of GaN on sapphire as well as porous SWCNT substrates is discussed briefly.

Polarization Resistance of (Ba0.5Sr0.5)0.99Co0.8Fe0.2O3-δ Air Electrode Synthesized by Glycine-Nitrate Process (Glycine-Nitrate 법으로 제조한 (Ba0.5Sr0.5)0.99Co0.8Fe0.2O3-δ 공기극의 분극저항)

  • Moon, Ji-Woong;Lim, Yong-Ho;Oh, You-Keun;Lee, Mi-Jai;Choi, Byung-Hyun;Hwang, Hae-Jin
    • Journal of the Korean Ceramic Society
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    • v.42 no.12 s.283
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    • pp.800-807
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    • 2005
  • Cathode material, $(Ba_{0.5}Sr_{0.5})_{0.99}Co_{0.8}Fe_{0.2}O_{3-\delta}$, for low temperature SOFC was prepared by the Glycine-Nitrate synthesis Process (GNP). Characteristics of the synthesized powders were studied with controlling the pH of a precursor solution. Highly acidic precursor solution increased a perovskite forming temperature. It is considered that Ba and Sr cannot complex by carboxylic acid group of glycine, because under highly acidic condition the caboxylic group mainly combined with H+ insead of alkaline earth cations. A lack of bond between cations and glycine resulted in selective precipitation of the elements during evaporation of the precursor solution. In case of using precursor solution with pH %2\~3$, a single perovskite phase was obtained at $1000^{\circ}C$. Polarization resistance of $(Ba_{0.5}Sr_{0.5})_{0.99}Co_{0.8}Fe_{0.2}O_{3-\delta}$ was measured by AC impedance spectroscopy from the two electrode symmetric cell. Area specific resistance of the $(Ba_{0.5}Sr_{0.5})_{0.99}Co_{0.8}Fe_{0.2}O_{3-\delta}$ air electrode at $500^{\circ}C\;and\;600^{\circ}C$ were $0.96{\Omega}{\cdot}cm^2\;and\;0.16{\Omega}{\cdot}cm^2$, respectively.

Synthesis of Polycarbosilane for SiC Precursor (II) (SiC의 Precursor Polycarbosilane의 합성 (II))

  • Han, Chul;Lee, Hyung-Bock;Chung, Yun-Joong
    • Journal of the Korean Ceramic Society
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    • v.25 no.5
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    • pp.518-522
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    • 1988
  • Polycarbosilane was synthesized from polydimethylsilane at 42$0^{\circ}C$, pyrolysis temperature with various times And IR, NMR, UV, and GPC were detected. Average molecular weight Mn was increased proportionally with the reaction time. Average molecular weight of polycarbosilane was about 700(n=20), which has chain structure and the product yield was 72%.

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Synthesis of Perforated Polygonal Cobalt Oxides using a Carbon Nanofiber Template (탄소나노섬유 모형을 이용한 천공된 다각형 코발트 산화물 합성)

  • Sin, Dong-Yo;An, Geon-Hyoung;Ahn, Hyo-Jin
    • Journal of Powder Materials
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    • v.22 no.5
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    • pp.350-355
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    • 2015
  • Perforated polygonal cobalt oxide ($Co_3O_4$) is synthesized using electrospinning and a hydrothermal method followed by the removal of a carbon nanofiber (CNF) template. To investigate their formation mechanism, thermogravimetric analysis, field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy are examined. To obtain the optimum condition of perforated polygonal $Co_3O_4$, we prepare three different weight ratios of the Co precursor and the CNF template: sample A (Co precursor:CNF template- 10:1), sample B (Co precursor:CNF template-3.2:1), and sample C (Co precursor:CNF template-2:1). Among them, sample A exhibits the perforated polygonal $Co_3O_4$ with a thin carbon layer (5.7-6.2 nm) owing to the removal of CNF template. However, sample B and sample C synthesized perforated round $Co_3O_4$ and destroyed $Co_3O_4$ powders, respectively, due to a decreased amount of Co precursor. The increased amount of the CNF template prevents the formation of polygonal $Co_3O_4$. For sample A, the optimized weight ratio of the Co precursor and CNF template may be related to the successful formation of perforated polygonal $Co_3O_4$. Thus, perforated polygonal $Co_3O_4$ can be applied to electrode materials of energy storage devices such as lithium ion batteries, supercapacitors, and fuel cells.

Effects of Metallic Silicon on the Synthsis of β-SiC Powders by a Carbothermal Reduction Using SiO2-C Hybrid Precursor Fabricated by a Sol-gel Process (솔-젤 공정으로 제조된 SiO2-C 복합 전구체를 사용하여 열탄소환원법에 의한 β-SiC 분말 합성에 금속 Si 첨가가 미치는 영향)

  • Jo, Yung-Chul;Youm, Mi-Rae;Yun, Sung-Il;Cho, Gyoung-Sun;Park, Sang-Whan
    • Journal of the Korean Ceramic Society
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    • v.50 no.6
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    • pp.402-409
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    • 2013
  • The objective of this study was to develop a synthesis process for ${\beta}$-SiC powders to reduce the synthesis temperature and to control the particle size and to prevent particle agglomeration of the synthesized ${\beta}$-SiC powders. A phenol resin and TEOS were used as the starting materials for the carbon and Si sources, respectively. $SiO_2$-C hybrid precursors with various C/Si mole ratios were fabricated using a conventional sol-gel process. ${\beta}$-SiC powders were synthesized by a carbothermal reduction process using $SiO_2$-C hybrid precursors with various C/Si mole ratios (1.6 ~ 2.5) fabricated using a sol-gel process. In this study, the effects of excess carbon and the addition of Si powders to the $SiO_2$-C hybrid precursor on the synthesis temperature and particle size of ${\beta}$-SiC were examined. It was found that the addition of metallic Si powders to the $SiO_2$/C hybrid precursor with excess carbon reduced the synthesis temperature of the ${\beta}$-SiC powders to as low as $1300^{\circ}C$. The synthesis temperature for ${\beta}$-SiC appeared to be reduced with an increase of the C/Si mole ratio in the $SiO_2$-C hybrid precursor by a direct carburization reaction between Si and excess carbon.

A Study on the Automation and Optimization of 9-(4-[$^{18}F$] Fluoro-3-hydroxymethylbutyl) Guanine Synthesis (9-(4-[$^{18}F$] Fluoro-3-hydroxymethylbutyl) guanine 합성의 자동화와 최적화에 관한 연구)

  • An, Jae-Seok;Hong, Sung-Tack;Kang, Se-Hun;Won, Woo-Jae
    • The Korean Journal of Nuclear Medicine Technology
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    • v.15 no.2
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    • pp.72-75
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    • 2011
  • Purpose: The HSV1-tk reporter gene system is the most widely used system because of its advantage is that it is possible to monitor directly without the introduction of a separate reporter gene in case of HSV1-tk suicide gene therapy. This study was performed to automate 9-(4-[$^{18}F$] Fluoro-3-hydroxymethylbutyl) guanine ([$^{18}F$] FHBG) that are widely used as substrate for the HSV1-tk reporter gene in living organisms with positron emission tomography (PET) and find the optimized conditions of synthesis. Materials and Methods: Fully automated synthesis of [$^{18}F$] FHBG was performed using Explora-RN (CTI, USA) module. We have changed of reaction time (3, 5, 10 min) and temperature (110, 120, $130^{\circ}C$) for the optimized conditions of synthesis. Also we experimented to find the optimal concentration of precursor (5, 7, 10 mg). Results: [$^{18}F$] FHBG was purified by HPLC system and collected at around 10-12 min. Synthesis using Explora-RN module showed a $32.0{\pm}1.2%$ yield of radiochemical (decay corrected), the purity was greater than 98%. And the entire synthesis time was less than 48 min. Temperature of the highest synthesis yield was $130^{\circ}C$, reaction time was 5 minutes and concentration of precursor was 10 mg (recommended volume in manual) (n=36). In contrast to radiochemical yield of precursor 10 mg ($32{\pm}1.2%$), yield of 5 and 7 mg precursor was unstable. Conclusion: Automation of [$^{18}F$] FHBG synthesis at Explora-RN module has been completed. In addition, we were able to obtain optimized reaction time, temperature and concentration of precursor. Therefore this study would be provided more rapid synthesis and higher radiochemical yield.

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