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Cofactor‐Free, Direct Photoactivation of Enoate Reductases for the Asymmetric Reduction of C=C Bonds
Lee, Sahng Ha,Choi, Da Som,Pesic, Milja,Lee, Yang Woo,Paul, Caroline E.,Hollmann, Frank,Park, Chan Beum VCH Verlagsgesellschaft mbH 2017 Angewandte Chemie Vol.56 No.30
<P><B>Abstract</B></P><P>Enoate reductases from the family of old yellow enzymes (OYEs) can catalyze stereoselective <I>trans</I>‐hydrogenation of activated C=C bonds. Their application is limited by the necessity for a continuous supply of redox equivalents such as nicotinamide cofactors [NAD(P)H]. Visible light‐driven activation of OYEs through NAD(P)H‐free, direct transfer of photoexcited electrons from xanthene dyes to the prosthetic flavin moiety is reported. Spectroscopic and electrochemical analyses verified spontaneous association of rose bengal and its derivatives with OYEs. Illumination of a white light‐emitting‐diode triggered photoreduction of OYEs by xanthene dyes, which facilitated the enantioselective reduction of C=C bonds in the absence of NADH. The photoenzymatic conversion of 2‐methylcyclohexenone resulted in enantiopure (<I>ee</I>>99 %) (<I>R</I>)‐2‐methylcyclohexanone with conversion yields as high as 80–90 %. The turnover frequency was significantly affected by the substitution of halogen atoms in xanthene dyes.</P>
Park, Chiyoung,Oh, Kyoungho,Lee, Sang ,Cheon,Kim, Chulhee VCH Verlagsgesellschaft mbH 2007 Angewandte Chemie Vol.46 No.9
<B>Graphic Abstract</B> <P>Stringing them along: The pores of a mesoporous silica particle were filled with guest molecules and then blocked by threading cyclodextrin molecules (CDs) onto the surface-grafted polyethylenimine (PEI) chains at pH 11. At pH 5.5, the guest molecules can be released from the pores of the particle by reversible dethreading of the CDs from the PEI chains. <img src='wiley_img/14337851-2007-46-9-ANIE200603404-content.gif' alt='wiley_img/14337851-2007-46-9-ANIE200603404-content'> </P>
Kim, Soo ,Min,Park, Ji ,Hoon,Choi, Soo ,Young,Chung, Young ,Keun VCH Verlagsgesellschaft mbH 2007 Angewandte Chemie Vol.46 No.32
<B>Graphic Abstract</B> <P>Biscyclopropanation: Dienynes containing a cyclohexadienyl unit can be converted into tetracyclo[3.3.0.0<SUP>2,8</SUP>.0<SUP>4,6</SUP>]octanes by treatment with an (N-heterocyclic carbene)gold catalyst. When the dienynes bear an open-chain diene instead of cyclohexadiene, open-cage compounds, with two sides missing from the cage, are obtained. <img src='wiley_img/14337851-2007-46-32-ANIE200702028-content.gif' alt='wiley_img/14337851-2007-46-32-ANIE200702028-content'> </P>
Chung, Yeonseok,Chang, Jae-Hoon,Kim, Byung-Seok,Lee, Jung-Mi,Kim, Ho-Youn,Kang, Chang-Yuil VCH Verlagsgesellschaft mbH, etc 2007 European journal of immunology Vol. No.
<P>In the spleen, exogenous antigen is preferentially presented by CD8&agr;<SUP>+</SUP>CD11b<SUP>–</SUP> DC to CD8 T cells and by CD8&agr;<SUP>–</SUP>CD11b<SUP>+</SUP> DC to CD4 T cells. However, it is not yet clear whether the same rule applies to other secondary lymphoid organs. To address this issue, we first classified secondary lymphoid tissues into three categories based on the expression pattern of CD8&agr; and CD11b in C57BL/6 and BALB/c mice: (a) spleen, (b) mesenteric lymph node (MLN) and (c) other peripheral lymph nodes (PLN). We then analyzed the OVA-specific T cell-stimulating capacity of each DC subset after intravenous injection with soluble OVA. Our results show that, regardless of tissue origin, CD8&agr;<SUP>–</SUP>CD11b<SUP>+</SUP> DC generally present OVA to CD4 T cells, a finding that held true as well for CD8&agr;<SUP>+</SUP>CD11b<SUP>+</SUP> DC in PLN. In striking contrast, CD8&agr;<SUP>+</SUP>CD11b<SUP>–</SUP> DC in spleen, CD8&agr;<SUP>–</SUP>CD11b<SUP>+</SUP> DC in MLN and CD8&agr;<SUP>+</SUP>CD11b<SUP>+</SUP> DC in PLN mainly cross-present OVA to CD8 T cells in their respective tissues. Of note, CD8&agr;<SUP>–</SUP>CD11b<SUP>+</SUP> DC in MLN and CD8&agr;<SUP>+</SUP>CD11b<SUP>+</SUP> DC in PLN present OVA to both CD4 T and CD8 T cells. Therefore, the antigen-presenting capacity of each distinct DC subset is determined by its anatomic environment in combination with its surface phenotype.</P>