The Magic-Size Nanocluster (CdSe)₃₄ as a Low-Temperature Nucleant for Cadmium Selenide Nanocrystals; Room-Temperature Growth of Crystalline Quantum Platelets

Reaction of Cd­(OAc)₂·2H₂O and selenourea in primary-amine/secondary-amine cosolvent mixtures affords crystalline CdSe quantum platelets at room temperature. Their crystallinity is established by X-ray diffraction analysis (XRD), high-resolution transmission electron microscopy (TEM), and their sharp extinction and photoluminescence spectra. Reaction monitoring establishes the magic-size nanocluster (CdSe)₃₄ to be a key intermediate in the growth process, which converts to CdSe quantum platelets by first-order kinetics with no induction period. The results are interpreted to indicate that the critical crystal-nucleus size for CdSe under these conditions is in the range of (CdSe)₃₄ to (CdSe)₆₈. The nanocluster is obtained in isolated form as [(CdSe)₃₄(<i>n</i>-octylamine)₁₆(di-<i>n</i>-pentylamine)₂], which is proposed to function as crystal nuclei that may be stored in a bottle

Cupric Yersiniabactin Is a Virulence-Associated Superoxide Dismutase Mimic

Many Gram-negative bacteria interact with extracellular metal ions by expressing one or more siderophore types. Among these, the virulence-associated siderophore yersiniabactin (Ybt) is an avid copper chelator, forming stable cupric (Cu­(II)-Ybt) complexes that are detectable in infected patients. Here we show that Ybt-expressing <i>E. coli</i> are protected from intracellular killing within copper-replete phagocytic cells. This survival advantage is highly dependent upon the phagocyte respiratory burst, during which superoxide is generated by the NADPH oxidase complex. Chemical fractionation links this phenotype to a previously unappreciated superoxide dismutase (SOD)-like activity of Cu­(II)-Ybt. Unlike previously described synthetic copper-salicylate (Cu­(II)-SA) SOD mimics, the salicylate-based natural product Cu­(II)-Ybt retains catalytic activity at physiologically plausible protein concentrations. These results reveal a new virulence-associated adaptation based upon spontaneous assembly of a non-protein catalyst

Improving euricic acid content in rapeseed through biotechnology: what can the Arabidopsis FAE1 and the Yeast SLC1-1 genes contribute

The main goal of our research is to produce, by genetic manipulation, Brassica napus L. cultivars with higher amounts of 22:1 in their seed oil than in present Canadian high erucic acid rapeseed (HEAR) cultivars developed through traditional breeding, ideally with proportions of 22:1 approaching 80 mol% (828 g kg\u207b\ub9). To probe some rate-limiting steps in the accumulation of triacylglycerols containing very long chain fatty acids (VLCFAs), particularly erucic acid (22:1), we have taken a transgenic approach, studying the effect of expressing two target genes in HEAR B. napus cv. Hero. To study the role of the elongase complex, involved in elongation of C18 fatty acid moieties to produce VLCFAs, we expressed the Arabidopsis thaliana L., fatty acid elongase 1 (FAE1) gene under the control of a seed-specific promoter (napin), in Hero. This resulted in increased proportions of 22:1 in the seed oil, rising from 430 g kg\u207b\ub9 in non-transformed controls to 480 to 530 g kg\u207b\ub9 22:1 in FAE1 transgenic Hero lines. The FAE1 lines exhibited higher elongase activity in vitro compared to control lines. These data suggest that the level of active condensing enzyme in the native elongase complex is somewhat rate limiting for synthesis of erucic acid and other VLCFAs in HEAR. In small scale field trials, the VLCFA and 22:1 content of FAE1 transgenic lines were superior to field-grown control lines. We report that in field plot trials, the progeny of our best T4 B. napus cv. Hero SLC1-1 transgenic lines clearly out-performed controls in terms of 22:1, oil content, and yield.Peer reviewed: YesNRC publication: Ye