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    ABSTRACT: The crystal structure of the title compound, CHBrO·CHCl, prepared in six steps from diosgenin, confirmed that the configurations of the stereogenic centers, positions 20 and 25, remain unchanged during the reaction. The six-membered , and rings have chair conformations. The five-membered ring has an envelope conformation (with the methyl-substituted C atom fused to ring as the flap) and the six-membered dihydro-pyran ring adopts a twist-boat conformation. In the crystal, mol-ecules are linked C-H⋯O and C-H⋯Cl hydrogen bonds, the latter involving the dichloro-methane solvent mol-ecule, forming a three-dimensional supra-molecular network.
    Acta Crystallographica Section E Structure Reports Online 12/2012; 68(Pt 12):o3260-1. DOI:10.1107/S1600536812043590
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    ABSTRACT: The relationship between accumulation of Pb2+ and changes in GSH biosynthesis was analyzed in both leaves and roots of the Pb2+-hyperaccumulator aquatic fern Salvinia minima, after exposure to 40 μM Pb(NO3)2. Lead accumulation in both tissues increased the accumulation of GSH, increased the enzymatic activity of glutathione synthase (GS), and caused changes in the expression levels of SmGS genes in both tissues. The damage caused by Pb on plant performance, was evaluated by the changes in the content of pigments, particularly on the carotenoids content. Lead accumulation caused more damage in roots than in leaves as indicated by the decrease on their carotenoids content. It is interesting that in leaves, the concentration of GSH, the activity of GS and the expression levels of SmGS gene were all higher than in roots. These results, together with our previous finding that roots accumulated more phytochelatins than did leaves of S. minima plants exposed to similar concentrations of lead (Estrella et al., 2009), suggest that the Pb-hyperaccumulator aquatic fern, S. minima, displays a coordinated and differential response to Pb2+ at leaves and roots, where GSH may play an important role in protecting leaves from the detrimental effects of lead, perhaps by counteracting the effect of free radicals.
    Environmental and Experimental Botany 01/2012; 75:188–194. DOI:10.1016/j.envexpbot.2011.09.001
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    ABSTRACT: Pectin lyases cleave the internal glycosidic bonds of pectin by β-elimination, producing non-saturated galacturonic oligomers. Genetic improvement of pectin lyase-overproducing strains is still necessary to improve industrial processes based on this enzyme. In the present study hybrids were obtained by protoplast fusion between mutant pectinolytic Aspergillus flavipes and Aspergillus niveus CH-Y-1043 strains. Prototrophic segregants showed different isoenzymatic profiles and produced increased levels of pectin lyase in cultures containing lemon peel as a sole carbon source. Hybrid HZ showed an increase of 450% and 1300% in pectin lyase production compared with that of A. niveus CH-Y-1043 and A. flavipes, respectively. Pectin lyase produced by the hybrid HZ was partially purified and used for the hydrolysis of orange peel. Pectin lyase was able to hydrolyze 56% of orange peel biomass. However, addition of 2 RFU and 20 U of endo- and exo-polygalacturonase, respectively, induced the hydrolysis of 92% of orange peel solids. In conclusion HZ is a pectin lyase-overproducing hybrid with potential applications in the pectin industry.
    Enzyme and Microbial Technology 03/2009; DOI:10.1016/j.enzmictec.2008.11.003


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    Mérida, Mexico
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