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Browsing by Author "Wu, C. Y."

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    RmpA Regulation of Capsular Polysaccharide Biosynthesis in Klebsiella pneumoniae CG43
    (2010-06-01)
    Cheng, H. Y.
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    Chen, Y. S.
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    Wu, C. Y.
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    Chang, H. Y.
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    Lai, Y. C.
    Sequence analysis of the large virulence plasmid pLVPK in Klebsiella pneumoniae CG43 revealed the presence of another mucoid factor encoding gene rmpA besides rmpA2. Promoter activity measurement indicated that the deletion of rmpA reduced K2 capsular polysaccharide (CPS) biosynthesis, resulting in decreased colony mucoidy and virulence in mice. Introduction of a multicopy plasmid carrying rmpA restored CPS production in the rmpA or rmpA2 mutant but not in the rcsB mutant. Transformation of the rmpA deletion mutant with an rcsB-carrying plasmid also failed to enhance CPS production, suggesting that a cooperation of RmpA with RcsB is required for regulatory activity. This was further corroborated by the demonstration of in vivo interaction between RmpA and RcsB using two-hybrid analysis and coimmunoprecipitation analysis. A putative Fur binding box was only found at the 5' noncoding region of rmpA. The promoter activity analysis indicated that the deletion of fur increased the rmpA promoter activity. Using electrophoretic mobility shift assay, we further demonstrated that Fur exerts its regulatory activity by binding directly to the promoter. As a result, the fur deletion mutant exhibited an increase in colony mucoidy, CPS production, and virulence in mice. In summary, our results suggested that RmpA activates CPS biosynthesis in K. pneumoniae CG43 via an RcsB-dependent manner. The expression of rmpA is regulated by the availability of iron and is negatively controlled by Fur.
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    The Photocatalytic Activity and Compact Layer Characteristics of TiO2 Films Prepared Using Radio Frequency Magnetron Sputtering
    (2014)
    Chang, H. C.
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    Huang, H. H.
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    Wu, C. Y.
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    Hsu, R. Q.
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    Hsu, C. Y.
    TiO2 compact layers are used in dye-sensitized solar cells (DSSCs) to prevent charge recombination between the electrolyte and the transparent conductive substrate (indium tin oxide, ITO; fluorine-doped tin oxide, FTO). Thin TiO2 compact layers are deposited onto ITO/glass by means of radio frequency (rf) magnetron sputtering, using deposition parameters that ensure greater photocatalytic activity and increased DSSC conversion efficiency. The photoinduced decomposition of methylene blue (MB) and the photoinduced hydrophilicity of the TiO2 thin films are also investigated. The photocatalytic performance characteristics for the deposition of TiO2 films are improved by using the Grey-Taguchi method. The average transmittance in the visible region exceeds 85% for all samples. The XRD patterns of the TiO2 films, for sol-gel with spin coating of porous TiO2 /TiO2 compact/ITO/glass, show a good crystalline structure. In contrast, without the TiO2 compact layer (only porous TiO2), the peak intensity of the anatase (101) plane in the XRD patterns for the TiO2 film has a lower value, which demonstrates inferior crystalline quality. With a TiO2 compact layer to prevent charge recombination, a higher short-circuit current density is obtained. The DSSC with the FTO/glass and Pt counter electrode demonstrates the energy conversion efficiency increased.
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