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Biochemical Properties of a Novel Cysteine Protease of <i>Plasmodium vivax</i> , Vivapain-4
Na, Byoung-Kuk,Bae, Young-An,Zo, Young-Gun,Choe, Youngchool,Kim, Seon-Hee,Desai, Prashant V.,Avery, Mitchell A.,Craik, Charles S.,Kim, Tong-Soo,Rosenthal, Philip J.,Kong, Yoon Public Library of Science 2010 PLoS neglected tropical diseases Vol.4 No.10
<▼1><P><B>Background</B></P><P>Multiple cysteine proteases of malaria parasites are required for maintenance of parasite metabolic homeostasis and egress from the host erythrocyte. In <I>Plasmodium falciparum</I> these proteases appear to mediate the processing of hemoglobin and aspartic proteases (plasmepsins) in the acidic food vacuole and the hydrolysis of erythrocyte structural proteins at neutral pH. Two cysteine proteases, vivapain (VX)-2 and VX-3 have been characterized in <I>P. vivax</I>, but comprehensive studies of <I>P. vivax</I> cysteine proteases remain elusive.</P><P><B>Findings</B></P><P>We characterized a novel cysteine protease of <I>P. vivax</I>, VX-4, of which orthologs appears to have evolved differentially in primate plasmodia with strong cladistic affinity toward those of rodent <I>Plasmodium</I>. Recombinant VX-4 demonstrated dual substrate specificity depending on the surrounding micro-environmental pH. Its hydrolyzing activity against benzyloxycarbonyl-Leu-Arg-4-methyl-coumaryl-7-amide (Z-Leu-Arg-MCA) and Z-Phe-Arg-MCA was highest at acidic pH (5.5), whereas that against Z-Arg-Arg-MCA was maximal at neutral pH (6.5–7.5). VX-4 preferred positively charged amino acids and Gln at the P1 position, with less strict specificity at P3 and P4. P2 preferences depended on pH (Leu at pH 5.5 and Arg at pH 7.5). Three amino acids that delineate the S2 pocket were substituted in VX-4 compared to VX-2 and VX-3 (Ala90, Gly157 and Glu180). Replacement of Glu180 abolished activity against Z-Arg-Arg-MCA at neutral pH, indicating the importance of this amino acid in the pH-dependent substrate preference. VX-4 was localized in the food vacuoles and cytoplasm of the erythrocytic stage of <I>P. vivax</I>. VX-4 showed maximal activity against actin at neutral pH, and that against <I>P. vivax</I> plasmepsin 4 and hemoglobin was detected at neutral/acidic and acidic pH, respectively.</P><P><B>Conclusion</B></P><P>VX-4 demonstrates pH-dependent substrate switching, which might offer an efficient mechanism for the specific cleavage of different substrates in different intracellular environments. VX-4 might function as a hemoglobinase in the acidic parasite food vacuole, a maturase of <I>P. vivax</I> plasmepsin 4 at neutral or acidic pH, and a cytoskeleton-degrading protease in the neutral erythrocyte cytosol.</P></▼1><▼2><P><B>Author Summary</B></P><P><I>Plasmodium vivax</I> affects hundreds of millions each year and results in severe morbidity and mortality. Plasmodial cysteine proteases (CPs) play crucial roles during the progression of malaria since inhibition of these molecules impairs parasite growth. These CPs might be targeted for new antimalarial drugs. We characterized a novel <I>P. vivax</I> CP, vivapain-4 (VX-4), which appeared to evolve differentially among primate <I>Plasmodium</I> species. VX-4 showed highly unique substrate preference depending on surrounding micro-environmental pH. It effectively hydrolyzed benzyloxycarbonyl-Leu-Arg-4-methyl-coumaryl-7-amide (Z-Leu-Arg-MCA) and Z-Phe-Arg-MCA at acidic pH and Z-Arg-Arg-MCA at neutral pH. Three amino acids (Ala90, Gly157 and Glu180) that delineate the S2 pocket were found to be substituted in VX-4. Alteration of Glu180 abolished hydrolytic activity against Z-Arg-Arg-MCA at neutral pH, indicating Glu180 is intimately involved in the pH-dependent substrate preference. VX-4 hydrolyzed actin at neutral pH and hemoglobin at acidic pH, and participated in plasmepsin 4 activation at neutral/acidic pH. VX-4 was localized in the food vacuoles and cytoplasm of the erythrocytic stage of <I>P. vivax</I>. The differential substrate preferences depending on pH suggested a highly efficient mechanism to enlarge biological implications of VX-4, including hemoglobin degradation, maturation of plasmepsin, and remodeling of the parasite architecture during growth and development of <I>P. vivax</I>.</P></▼2>
함티탄자철광의 제련에 관한 연구 : 선철과 티탄광재의 제조 및 티탄광재의 염화반응성에 대하여
윤동석,백영현,김재수 대한금속재료학회(대한금속학회) 1974 대한금속·재료학회지 Vol.12 No.3
소연평도산 함티탄자철광으로 부터 선철 및 티탄광재의 제조성에 대한 기초조사가 되었다. 65 mesh 이하의 광석에 대하여 Na₂O 8.7%에 해당하는 sodium 용제(Na₂CO₃나 NaOH) 및 탄소 15%를 사용하여 1,530℃∼1,560℃에서 용해시킴으로서 약 Fe 95%의 선철과 TiO₂56% 이상의 티탄광재를 생산할 수 있다. 이 티탄광재는 산처리에 의하여 용이하게 1% 미만의 철분을 포함하는 TiO₂77% 이상의 고티탄광재를 제조할 수 있다. 고티탄광재는 또한 염화반응성이 우수하여 탄소 20%, 700℃에서 60분이내에 93%의 TiO₂를 TiCl₄로 전환시킬 수 있고 반응속도는 함티탄자철광이나 티탄철광보다 높다. The amenability of titaniferous magnetite from Soyonpyong-do to iron and titania slag was determined in a laboratory scale. The effects of grain size of the ore, amounts of sodium flux and carbon, and temperature on the smelting were studied. An attempt was also made to upgrade the titanic slag by leaching with sulfuric acid solution. Chlorination behaviours of titanic slag, titaniferous magnetite, and ilmenite were respectively investigated by a batch-boat technique. Optimum conditions for chlorination of titanic slag were compaired with those of other two titanium bearing substances.
Systematic Risks in the Options Market: Evidence from S&P 500 Index Options
Jaewon Park,Tong S. Kim 한국재무학회 2009 한국재무학회 학술대회 Vol.2009 No.05
The assumption of dynamic replication in no-arbitrage option pricing models does not hold in practice due to discreteness of trading hours as well as trading costs, which suggests the potential presence of preference-driven risk premiums. In this paper, we empirically show that discretely hedged S&P 500 index option portfolios are exposed to covariance and coskewness risk with the market portfolio. Using the three-moment CAPM of Kraus and Litzenberger (1976), we find that the rate of return of the portfolio significantly loads on the two risk factors, and their risk premiums are significantly positive. The equilibrium model complements the prevailing approach of the no-arbitrage framework, and reveals that the volatility smile is linked to investors’ preference on the unhedged market risks.
Phase Diagram of Physisorbed Argon Monolayer on Graphite
BYUNG IL CHOI,H. S. Nham,H. S. Youn,J. C. Kim,S. Y. Kwon,Tong Kun Lim 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.III
Studies on adsorption isotherms with sharp step-wised layer condensation help us better understanding on two-dimensional systems. We have presented vapor-pressure adsorption isotherm studies of argon films on highly oriented pyrolytic graphite in the monolayer region, by using a phase-modulated ellipsometric technique. The successive gas-liquid-solid phase transition observed during build up of a monolayer in Kr/graphite and Xe/graphite isotherms is not observed in any argon monolayer isotherms. The critical temperature, determined from the width in the chemical potential of the layer condensation step, is about 55.6 K, which is close to Migone’s capacity result. However if the background, known to come from the inhomogeneous nature of the graphite substrate, is considered, it is about 58 K. From our work and Migone’s heat-capacity results, we were able to complete a phase diagram of argon on graphite in the monolayer region. <
Park, Y.K.,Park, E.S.,Kim, D.H.,Ahn, S.H.,Park, S.H.,Lee, A.R.,Park, S.,Kang, H.S.,Lee, J.H.,Kim, J.M.,Lee, S.K.,Lim, K.H.,Isorce, N.,Tong, S.,Zoulim, F.,Kim, K.H. Elsevier Science Publishers 2016 Journal of hepatology Vol. No.
<P>Background & Aims: Cytokines are key molecules implicated in the defense against virus infection. Tumor necrosis factor-alpha (TNF-alpha) is well known to block the replication of hepatitis B virus (HBV). However, the molecular mechanism and the downstream effector molecules remain largely unknown. Methods: In this study, we investigated the antiviral effect and mechanism of p22-FLIP (FLICE-inhibitory protein) by ectopic expression in vitro and in vivo. In addition, to provide the biological relevance of our study, we examined that the p22-FLIP is involved in TNF-alpha-mediated suppression of HBV in primary human hepatocytes. Results: We found that p22-FLIP, a newly discovered c-FLIP cleavage product, inhibited HBV replication at the transcriptional level in both hepatoma cells and primary human hepatocytes, and that c-FLIP conversion to p22-FLIP was stimulated by the TNF-alpha/NF-kappa B pathway. p22-FLIP inhibited HBV replication through the upregulation of HNF3 beta but downregulation of HNF4 alpha, thus inhibiting both HBV enhancer elements. Finally, p22-FLIP potently inhibited HBV DNA replication in a mouse model of HBV replication. Conclusions: Taken together, these findings suggest that the anti-apoptotic p22-FLIP serves a novel function of inhibiting HBV transcription, and mediates the antiviral effect of TNF-a against HBV replication. (C) 2015 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.</P>