Substrate specificity of a recombinant <small>D</small>-lyxose isomerase from <i>Serratia proteamaculans</i> that produces <small>D</small>-lyxose and <small>D</small>-mannose

Park, C.-S.,Yeom, S.-J.,Lim, Y.-R.,Kim, Y.-S.,Oh, D.-K. Blackwell Publishing Ltd 2010 Letters in applied microbiology Vol.51 No.3

<P>Abstract</P><P>Aims: </P><P>Characterization of substrate specificity of a <SMALL>D</SMALL>-lyxose isomerase from <I>Serratia proteamaculans</I> and application of the enzyme in the production of <SMALL>D</SMALL>-lyxose and <SMALL>D</SMALL>-mannose.</P><P>Methods and Results: </P><P>The concentrations of monosaccharides were determined using a Bio-LC system. The activity of the recombinant protein from <I>Ser. proteamaculans</I> was the highest for <SMALL>D</SMALL>-lyxose among aldoses, indicating that it is a <SMALL>D-</SMALL>lyxose isomerase. The native recombinant enzyme existed as a 54-kDa dimer, and the maximal activity for <SMALL>D-</SMALL>lyxose isomerization was observed at pH 7·5 and 40°C in the presence of 1 mmol l<SUP>−1</SUP> Mn<SUP>2+</SUP>. The <I>K</I><SUB>m</SUB> values for <SMALL>D</SMALL>-lyxose, <SMALL>D</SMALL>-mannose, <SMALL>D</SMALL>-xylulose, and <SMALL>D</SMALL>-fructose were 13·3, 32·2, 3·83, and 19·4 mmol l<SUP>−1</SUP>, respectively. In 2 ml of reaction volume at pH 7·5 and 35°C, <SMALL>D</SMALL>-lyxose was produced at 35% (w/v) from 50% (w/v) <SMALL>D</SMALL>-xylulose by the <SMALL>D-</SMALL>lyxose isomerase in 3 h, while <SMALL>D</SMALL>-mannose were produced at 10% (w/v) from 50% (w/v) <SMALL>D</SMALL>-fructose in 5 h.</P><P>Conclusions: </P><P>We identified the putative sugar isomerase from <I>Ser. proteamaculans</I> as a <SMALL>D</SMALL>-lyxose isomerase. The enzyme exhibited isomerization activity for aldose substrates with the C2 and C3 hydroxyl groups in the left-hand configuration. High production rates of <SMALL>D-</SMALL>lyxose and <SMALL>D</SMALL>-mannose by the enzyme were obtained.</P><P>Significance and Impact of the Study: </P><P>A new <SMALL>D-</SMALL>lyxose isomerase was found, and this enzyme had higher activity for <SMALL>D</SMALL>-lyxose and <SMALL>D</SMALL>-mannose than previously reported enzymes. Thus, the enzyme can be applied in industrial production of <SMALL>D</SMALL>-lyxose and <SMALL>D</SMALL>-mannose.</P>

T_c and J_c distribution in in situ processed MgB₂ bulk superconductors with/without C doping

Kim, C.J.,Kim, Y.J.,Lim, C.Y.,Jun, B.H.,Park, S.D.,Choo, K.N. The Korea Institute of Applied Superconductivity a 2014 한국초전도저온공학회논문지 Vol.16 No.2

Temperature dependence of magnetic moment (m-T) and the magnetization (M-H) at 5 K and 20 K of the in situ processed $MgB_2$ bulk pellets with/without carbon (C) doping were examined. The superconducting critical temperature ($T_c$), the superconducting transition width (${\delta}T$) and the critical current density ($J_c$) were estimated for ten test samples taken from the $MgB_2$ bulk pellets. The reliable m-T characteristics associated with the uniform $MgB_2$ formation were obtained for both $MgB_2$ pellets. The $T_cs$ and ${\delta}Ts$ of all test samples of the undoped $MgB_2$ were the same each other as 37.5 K and 1.5 K, respectively. The $T_cs$ and ${\delta}Ts$ of the C-doped $MgB_2$ were 36.5 K and 2.5 K, respectively. Unlike the m-T characteristics, there existed the difference among the M-H curves of the test samples, which might be caused by the microstructure variation. In spite of the slight $T_c$ decrease, the C doping was effective in enhancing the $J_c$ at 5 K.

Holocene environmental change at the southern coast of Korea based on organic carbon isotope (δ¹³C) and C/S ratios

Lim, J.,Lee, J.Y.,Kim, J.C.,Hong, S.S.,Yang, D.Y. Pergamon Press 2015 QUATERNARY INTERNATIONAL Vol.384 No.-

<P>To trace the environmental change that occurred at a coastal area during the Holocene, we performed radiocarbon dating and geochemical analyses using sedimentary cores recovered from the Beolgyo tidal flats on the south coast of Korea. The delta C-13 values of total organic carbon (TOC), which represent relative inputs of terrestrial (or freshwater) and marine organic sources, revealed a long-term increasing trend from -27.5 to -21.7 parts per thousand during the period between 10,000 and 3000 cal BP, suggesting an evolutionary series of fluvial-dominant to marine-dominant environments, coupled with weakened summer monsoon intensity. From 3000 cal BP to the present, the delta C-13(TOC) decreased gradually from -21.7 to -24 parts per thousand, indicating enhancement of freshwater input during this time. The observed long-term environmental change was divided into six stages based on the averages of the total sulfur content (TS%) and the organic carbon to sulfur ratio (C/S), proxies for paleosalinity. On multi-centennial to millennial timescales, higher C/S ratios and lower TS% were linked to higher delta C-13(TOC) values, indicating strong freshwater input at Stage 2 (similar to 8300-7400 cal BP), Stage 4 (similar to 4500-3300 cal BP), and Stage 6 (similar to 1100 cal BP to present). Strong freshwater discharge events synchronously occurred at 4300 cal BP and 3600 cal BP along the south coast of Korea. Further testing should be carried out in other East Asian coastal areas. This study suggests that sedimentary delta C-13(TOC) values and C/S ratios can be used in Asian coastal regions to trace past freshwater input events and summer monsoon intensity during relatively stable sea level periods (e.g., the middle to late Holocene). (C) 2015 Elsevier Ltd and INQUA. All rights reserved.</P>

O-free polyacrylonitrile doping to improve the J_c(B) and H_c2 of MgB₂ wires

Hwang, S.M.,Sung, K.,Choi, J.H.,Kim, W.,Joo, J.,Lim, J.H.,Kim, C.J.,Park, Y.S.,Kim, D.H. North-Holland 2010 Physica. C, Superconductivity Vol.470 No.20

We selected polyacrylonitrile (PAN, -[C<SUB>3</SUB>H<SUB>3</SUB>N]-) as an O-free organic dopant and fabricated C-doped MgB<SUB>2</SUB> wires by in situ and powder-in-tube techniques. 0-5 wt.% PAN powders were uniformly mixed with B powder using a liquid mixing method. The precursor powders were mixed with Mg powder, filled into Fe tubes, and then drawn into wires. Sintering was performed at 900<SUP>o</SUP>C for 1h in a flowing Ar gas. The PAN doping decreased the critical temperature (T<SUB>c</SUB>) and a-axis lattice parameter, but significantly improved the critical current density (J<SUB>c</SUB>) in high fields, upper critical field (H<SUB>c2</SUB>), and irreversibility field (H<SUB>irr</SUB>) performances. These results are attributed to the replacement of B sites with C by the PAN doping. Furthermore, as expected, the MgO amount did not increase as the doping content increased. The J<SUB>c</SUB> of the PAN-doped MgB<SUB>2</SUB> wires was more than one order of magnitude higher than that of the undoped MgB<SUB>2</SUB> wire at 5K and 6.6T (1.46-3.82kA/cm<SUP>2</SUP> vs. 0.11kA/cm<SUP>2</SUP>).

Highly selective iron-based Fischer-Tropsch catalysts activated by CO₂-containing syngas

Chun, D.H.,Park, J.C.,Hong, S.Y.,Lim, J.T.,Kim, C.S.,Lee, H.T.,Yang, J.I.,Hong, S.,Jung, H. Academic Press 2014 Journal of catalysis Vol.317 No.-

Fischer-Tropsch synthesis (FTS) was carried out over precipitated iron-based catalysts activated by syngas (H<SUB>2</SUB>+CO) with different amounts of CO<SUB>2</SUB> (0%, 20%, 33%, and 50%). The activation using CO<SUB>2</SUB>-containing syngas significantly suppressed the production of undesired products, CH<SUB>4</SUB> and C<SUB>2</SUB>-C<SUB>4</SUB> hydrocarbons, but facilitated the production of valuable products, C<SUB>5+</SUB> hydrocarbons. In particular, in the case of C<SUB>19+</SUB> hydrocarbons, the target products of low-temperature FTS (≤280<SUP>o</SUP>C), both selectivity and productivity showed a great increase with an increased inlet CO<SUB>2</SUB> content during activation. We attribute the advantageous performance of the catalysts activated by CO<SUB>2</SUB>-containing syngas to the improvement in the effective performance of active iron carbides, possibly induced by an increased ratio of ε'-carbide (Fe<SUB>2.2</SUB>C) to χ-carbide (Fe<SUB>2.5</SUB>C) and a decreased fraction of inactive bulk carbons.

Genomic characterization and expression analysis of complement component 9 in rock bream (Oplegnathus fasciatus)

Wickramaarachchi, W.D.N.,Wan, Q.,Lee, Y.,Lim, B.S.,De Zoysa, M.,Oh, M.J.,Jung, S.J.,Kim, H.C.,Whang, I.,Lee, J. Academic Press 2012 Fish & Shellfish Immunology Vol.33 No.4

The complement component 9 (C9) is a single-chain glycoprotein that mediates formation of the membrane attack complex (MAC) on the surface of target cells. Full-length C9 sequence was identified from a cDNA library of rock bream (Oplegnathus fasciatus), and its genomic sequence was obtained by screening and sequencing of a bacterial artificial chromosome (BAC) genomic DNA library of rock bream. The rock bream complement component 9 (Rb-C9) gene contains 11 exons and 10 introns and is composed of a 1782 bp complete open reading frame (ORF) that encodes a polypeptide of 593 amino acids. Sequence analysis revealed that the Rb-C9 protein contains two thrombospondin type-1domains, a low-density lipoprotein receptor domain class A, a membrane attack complex & perforin (MACPF) domain, and an epidermal growth factor (EGF)-like domain. Important putative transcription factor binding sites, including those for NF-κB, SP-1, C/EBP, AP-1 and OCT-1, were found in the 5' flanking region. Phylogenetic analysis revealed a close proximity of Rb-C9 with the orthologues in puffer fish, and Japanese flounder. Quantitative real-time RT-PCR analysis confirmed that Rb-C9 was constitutively expressed in all the examined tissues isolated from healthy rock bream, with highest expression occurring in liver. Pathogen challenge, including Edwardsiella tarda, Streptococcus iniae, lipopolysaccharide endotoxin and rock bream iridovirus led to up-regulation of Rb-C9 in liver but no change in peripheral blood cells. The observed response to bacterial and viral challenges and high degree of evolutionary relationship to respective orthologues, confirmed that Rb-C9 is an important immune gene, likely involved in the complement system lytic pathway of rock bream.

Characterization of Insertional Variation of Porcine Endogenous Retroviruses in Six Different Pig Breeds

Jung, W.Y.,Yu, S.L.,Seo, D.W.,Jung, K.C.,Cho, I.C.,Lim, H.T.,Jin, D.I.,Lee, Jun-Heon Asian Australasian Association of Animal Productio 2012 Animal Bioscience Vol.25 No.10

Pigs may need to be exploited as xenotransplantation donors due to the shortage of human organs, tissues and cells. Porcine endogenous retroviruses (PERVs) are a significant obstacle to xenotransplantation because they can infect human cells in vitro and have the potential for transmission of unexpected pathogens to humans. In this research, 101 pigs, including four commercial breeds (23 Berkshire, 13 Duroc, 22 Landrace and 14 Yorkshire pigs), one native breed (19 Korean native pigs) and one miniature breed (10 NIH miniature pigs) were used to investigate insertional variations for 11 PERV loci (three PERV-A, six PERV-B and two PERV-C). Over 60% of the pigs harbored one PERV-A (907F8) integration and five PERV-B (B3-3G, B3-7G, 742H1, 1155D9 and 465D1) integrations. However, two PERV-A loci (A1-6C and 1347C1) and one PERV-B locus (B3-7F) were absent in Duroc pigs. Moreover, two PERV-C loci (C2-6C and C4-2G) only existed in Korean native pigs and NIH miniature pigs. The results suggest that PERV insertional variations differ among pig breeds as well as among individuals within a breed. Also, the results presented here can be used for the selection of animals that do not have specific PERV integration for xenotransplantation research.

Comparison of Live Performance and Meat Quality Parameter of Cross Bred (Korean Native Black Pig and Landrace) Pigs with Different Coat Colors

Hur, S.J.,Jeong, T.C.,Kim, G.D.,Jeong, J.Y.,Cho, I.C.,Lim, H.T.,Kim, B.W.,Joo, S.T. Asian Australasian Association of Animal Productio 2013 Animal Bioscience Vol.26 No.7

Five hundred and forty crossbred (Korean native black pig${\times}$Landrace) F2 were selected at a commercial pig farm and then divided into six different coat color groups: (A: Black, B: White, C: Red, D: White spot in black, E: Black spot in white, F: Black spot in red). Birth weight, 21st d weight, 140th d weight and carcass weight varied among the different coat color groups. D group (white spot in black coat) showed a significantly higher body weight at each weigh (birth weight, 140th d weight and carcass weight) than did the other groups, whereas the C group (red coat color) showed a significantly lower body weight at finishing stage (140th d weight and carcass weight) compared to other groups. Meat quality characteristics, shear force, cooking loss and meat color were not significantly different among the different coat color groups, whereas drip loss was significantly higher in F than in other groups. Most blood characteristics were not significantly different among the different groups, except for the red blood cells.

Electrocatalytic activity of chemically deposited Cu_xS thin film for counter electrode in quantum dots-sensitized solar cells

Lim, I.,Lee, D.Y.,Patil, S.A.,Shrestha, N.K.,Kang, S.H.,Nah, Y.C.,Lee, W.,Han, S.H. Elsevier Science Publishers 2014 Materials chemistry and physics Vol.148 No.3

The compact (c-Cu<SUB>x</SUB>S) and the porous (p-Cu<SUB>x</SUB>S) with particle decorated films of coppers-ulfidearesynthesized using a chemical bath deposition technique, and the films are characterized using electrochemical techniques. In addition, the chemically deposited Cu<SUB>x</SUB>S films are investigated as a counter electrode in quantum dots-sensitized solar cells (QSSCs). The available redox active reaction sites of the p-Cu<SUB>x</SUB>S film are found to be 57.9% higher than those available in the c-Cu<SUB>x</SUB>S film. From the electrochemical impedance spectroscopy, the effective diffusion coefficients of the polysulfide electrolyte in the c-Cu<SUB>x</SUB>S and p-Cu<SUB>x</SUB>S films are estimated to be 3.67 x 10<SUP>-5</SUP> and 6.35 x 10<SUP>-5</SUP> cm<SUP>2</SUP> s<SUP>-1</SUP>, respectively. These results can be ascribed to the improvement in the available redox active reaction sites and the electrocatalytic activity of the Cu<SUB>x</SUB>S counter electrode. As compared to the c-Cu<SUB>x</SUB>S film, the p-Cu<SUB>x</SUB>S film as a counter electrode exhibits an enhanced photovoltaic performance of the QSSCs with the power conversion efficiency of 3.17%, short-circuit current of 11.89 mA c<SUP>-</SUP>m<SUP>2</SUP>, open-circuit voltage of 0.50 V, and fill factor of 53.29. The improved performance of the QSSCs is ascribed to the improvements on the available redox active reaction sites, electrocatalytic activity and the diffusion coefficients, which are directly related to the surface morphology of the sulfide films.

Hydrolytic properties of a thermostable &agr;-<small>L</small>-arabinofuranosidase from <i>Caldicellulosiruptor saccharolyticus</i>

Lim, Y.-R.,Yoon, R.-Y.,Seo, E.-S.,Kim, Y.-S.,Park, C.-S.,Oh, D.-K. Blackwell Publishing Ltd 2010 Journal of Applied Microbiology Vol.109 No.4

<P>Abstract</P><P>Aims: </P><P>To characterize of a thermostable recombinant &agr;-<SMALL>L</SMALL>-arabinofuranosidase from <I>Caldicellulosiruptor saccharolyticus</I> for the hydrolysis of arabino-oligosaccharides to <SMALL>L</SMALL>-arabinose.</P><P>Methods and Results: </P><P>A recombinant &agr;-<SMALL>L</SMALL>-arabinofuranosidase from <I>C. saccharolyticus</I> was purified by heat treatment and Hi-Trap anion exchange chromatography with a specific activity of 28·2 U mg<SUP>−1</SUP>. The native enzyme was a 58-kDa octamer with a molecular mass of 460 kDa, as measured by gel filtration. The catalytic residues and consensus sequences of the glycoside hydrolase 51 family of &agr;-<SMALL>L</SMALL>-arabinofuranosidases were completely conserved in &agr;-<SMALL>L</SMALL>-arabinofuranosidase from <I>C. saccharolyticus</I>. The maximum enzyme activity was observed at pH 5·5 and 80°C with a half-life of 49 h at 75°C. Among aryl-glycoside substrates, the enzyme displayed activity only for <I>p</I>-nitrophenyl-&agr;-<SMALL>L</SMALL>-arabinofuranoside [maximum <I>k</I><SUB>cat</SUB>/<I>K</I><SUB>m</SUB> of 220 m(mol l<SUP>−1</SUP>)<SUP>−1</SUP> s<SUP>−1</SUP>] and <I>p</I>-nitrophenyl-&agr;-<SMALL>L</SMALL>-arabinopyranoside. This substrate specificity differs from those of other &agr;-<SMALL>L</SMALL>-arabinofuranosidases. In a 1 mmol l<SUP>−1</SUP> solution of each sugar, arabino-oligosaccharides with 2–5 monomer units were completely hydrolysed to <SMALL>L</SMALL>-arabinose within 13 h in the presence of 30 U ml<SUP>−1</SUP> of enzyme at 75°C.</P><P>Conclusions: </P><P>The novel substrate specificity and hydrolytic properties for arabino-oligosaccharides of &agr;-<SMALL>L</SMALL>-arabinofuranosidase from <I>C. saccharolyticus</I> demonstrate the potential in the commercial production of <SMALL>L</SMALL>-arabinose in concert with endoarabinanase and/or xylanase.</P><P>Significance and Impact of the Study: </P><P>The findings of this work contribute to the knowledge of hydrolytic properties for arabino-oligosaccharides performed by thermostable &agr;-<SMALL>L</SMALL>-arabinofuranosidase.</P>