Browsing by Author "Lee, GSH"

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    A DNA-based assay for toxic chemicals in wastewater
    (Wiley-Blackwell, 2011-08-01) Foreman, AL; Philips, L; Kanellis, VG; Hammoudeh, D; Naumann, C; Wong, HKY; Chisari, R; Hibbert, DB; Lee, GSH; Patra, R; Julli, M; Chapman, J; Cooke, AR; dos Remedios, CG
    Chemical toxicants, particularly metal ions, are a major contaminant in global waterways. Live-organism bioassays used to monitor chemical toxicants commonly involve measurements of activity or survival of a freshwater cladoceran (Ceriodaphnia dubia) or light emitted by the marine bacterium Vibrio fischeri, used in the commercial Microtox (R) bioassay. Here we describe a novel molecule-based assay system employing DNA as the chemical biosensor. Metals bind to DNA, causing structural changes that expel a bound (intercalated) fluorescent reporter dye. Analyses of test data using 48 wastewater samples potentially contaminated by metal ions show that the DNA-dye assay results correlate with those from C. dubia and Microtox bioassays. All three assays exhibit additive, antagonistic, and synergistic responses that cannot be predicted by knowing individual metal concentrations. Analyses of metals in these samples imply the presence of chemical toxicants other than metal ions. The DNA-dye assay is robust, has a 12-month shelf life, and is only slightly affected by sample pH in the range 4 to 9. The assay is completed in a matter of minutes, and its portability makes it well suited as a screening assay for use in the field. We conclude that the DNA-dye test is a surrogate bioassay suitable for screening chemical toxicity. Environ. Toxicol. Chem. 2011;30:1810-1818. (C) 2011 SETAC
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    Polymer nanoscale morphology in Chara australis Brown cell walls studied by advanced solid state techniques
    (National Museum of Natural History, 2006-11) Garvey, CJ; Keckes, J; Parker, IH; Beilby, M; Lee, GSH
    The cell wall of the green algae Chara australis Brown (Charophyta, Algae) has been examined with solid state techniques (suitable for characterising the nanoscale arrangement of polymers) and solid state chemistry. The chemical composition of a bulk dried sample of Chara australis was examined using cross-polarisation magic angle spinning (CP-MAS) C-13 nuclear magnetic resonance (NMR). The presence of phenyl-propane subunits typical of the cross linked polymer, lignin, is not revealed. The arrangement of cellulose in the cell wall was probed by examining the wide angle diffraction pattern of a single fibre oriented with respect to an x-ray beam. The pattern produced was typical of a textured crystalline lattice embedded in an amorphous matrix. The x-ray reflections are much broader than most found in higher plants and it is difficult to resolve texture. Polarised Raman scattering from a similar sample provided clearer evidence of a textured cellulose matrix embedded in an amorphous matrix. It is found that the charophyte cell wall has many similarities in chemical composition and nanoscale arrangement of cell wall polymers to that of the higher plant, including the presence and arrangement, of cellulose and various polysaccharides. © 2006, Elsevier Ltd.