Browsing by Author "Hammerton, KM"

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    Accumulation of radionuclide and metal contaminants in flesh and osteoderms of estuarine crocodiles (crocodylus porosus): pathways and histories of catchment-specific exposure
    (EDP Sciences, 2002-02) Jeffree, RA; Markich, SJ; Hammerton, KM; Russell, RA
    Flesh and osteoderms of estuarine crocodiles (C. porosus) from Kakadu National Park, Northern Australia, were analysed for a range of metals, including uranium, to assess their capability for accumulation, in relation to their catchment-specific exposure to i) uranium mine effluents and mineralisation and ii) lead shot ammunition through their consumption of fauna shot by the traditional owners of the Park. Uranium in osteoderms was significantly (P<0.05) elevated in the East Alligator River catchment, that contains the Ranger and Jabiluka uranium mine sites, relative to two other adjacent catchments. The mean concentrations of other elements in flesh and osteoderms were also significantly (P<0.05) different between catchments. Linear discriminant analysis was used to demonstrate that multi-element signatures in both flesh and osteoderms could be used to classify individual crocodiles to their respective catchments. This approach may be useful for the identification of source catchments of itinerant 'nuisance crocodiles' that find their way into Darwin Harbour, close to dense human habitation. Lead concentrations were significantly (P<0.05) enhanced in flesh and osteoderms of crocodiles sampled within two areas hunted with guns using Pb ammunition. Enhanced ratios of Pb:Ca in the annual laminations of their osteoderms are consistent with their history of continual exposure to elevated anthropogenic Pb sources. Subsequent experimental studies have demonstrated the ability of the crocodilian stomach to retain ingested Pb shot, that is readily solubilised and absorbed into the blood and then archived in the contemporary osteodermal lamination. © EDP Sciences, 2002
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    Crocodile bones as archives of pollution exposure: lead contamination in Kakadu National Park, and what's in Sweetheart's Osteoderms?
    (Australian Nuclear Science and Technology Organisation, 2001-08-23) Jeffree, RA; Markich, SJ; Hammerton, KM; Russell, RA
    Experimental findings made it then possible to evaluate the hypothesis that the estuarine crocodile osteodermal laminations would record enhanced blood lead concentrations resulting from the ingestion of lead shot. At about 140 days following lead shot ingestion, two osteoderms were removed from each exposed and control animal. SIMS analysis of Pb-208 and Ca-42 signal intensities was then performed on sections that were prepared and analysed using similar methods previously used on field-collected specimens (Twining et al., 1999). These initial findings are consistent with the hypothesis that incremental laminations of the osteoderm will archive a lead signal that responds to enhanced levels of lead in the animal's blood during its life. SEM analysis identified the laminated structure of the osteoderm, however microprobe analysis did not detect appreciable amounts of even Ca and P, although the organic matrix was obviously present. It is proposed that this anomalous result is due to the preparatory tanning of the skin, in acid solution, that could be expected to leach elements from the organic matrix. An analogy is drawn with the decalcified skeletons in the bodies of the Druid sacrifices due their deposition in acid swamp waters in the UK. The challenge is now to sample osteoderms from large crocodiles in the Finniss River, preferably in close proximity to the Rum Jungle mine site, where any archived pollution signal would be more intense, and then repeat this analytical investigation of the osteodermal history of contaminant loadings. © 2002 Commonwealth of Australia
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    In vivo deuteration strategies for neutron scattering analysis of bacterial polyhydroxyoctanoate
    (Springer Nature, 2008-05-15) Russell, RA; Holden, PJ; Wilde, KL; Garvey, CJ; Hammerton, KM; Foster, LJR
    The cultivation of microorganisms on deuterated substrates has allowed us to control deuterium incorporation into biopolymer systems which is important for characterisation using neutron scattering techniques. Bacterial polyhydroxyoctanoate (PHO) is a polyester formed within inclusions inside bacterial cells and was deuterated in vivo under various conditions to characterise the formation of these inclusions by neutron scattering. Manipulation of deuterated media during microbial growth and PHO production phases resulted in polymer with partial or complete substitution of hydrogen by deuterium, as shown by gas chromatography. Sequential feeding of hydrogenated and deuterated forms of the same precursor was used to demonstrate that neutron scattering analysis could be used to differentiate between chemically similar phases in these polymer inclusions. © 2008 Crown Copyright
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    Interactions of cationic dendrigraft polymers with oligonucleotides and morphology of the resulting complexes.
    (American Chemical Society, 2008-04-06) Yun, SI; Hammerton, KM; Gauthier, M
    The high density of negatively charged phosphate groups on ONs allows the formation of stable complexes with synthetic cationic polyelectrolytes (PEs). Even though DNA complexes with quaternized poly-vinylpyridine linear chains were previously reported to increase the efficiency of cell transformation, no report has been made for DNA complexes with dendrigraft PEs. For the current investigation, cationic dendrigraft polymers with pH-independent fully charged quaternized amine groups were synthesized. The structure of dendrigraft PEs and their complexes with ONs in solution was investigated by small-angle neutron scattering (SANS).
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    Investigation of the phase morphology of bacterial PHA inclusion bodies by contrast variation SANS
    (Elsevier, 2006-11-15) Russell, RA; Holden, PJ; Garvey, CJ; Wilde, KL; Hammerton, KM; Foster, LJR
    Under growth-limiting conditions, many bacteria are able to metabolise excess organic acids into polyhydroxyalkanoates (PHA) and store these polymers as intracellular inclusions until the return of favourable conditions. Various models have been proposed for the macromolecular organisation of the boundary layer Surrounding the polymer, and contrast-variation small-angle neutron scattering (SANS) was used to study its organisation. Inclusions formed by Pseudomonas oleovorans under hydrogenating conditions showed lowest scattering intensity at ca. 20% D2O. The inclusions consist of protein and membrane lipids in the boundary layer and polyhydroxyoctanoate (lipid) in the inclusion body. At 20% D2O the contributions of lipids were contrast matched with the solvent, indicating that lipids contributed the bulk of the scattering intensity observed at other D2O/H2O ratios. These results are inconsistent with a model of the boundary layer which proposed outer and inner layers of crystalline protein lattice sandwiching a membrane lipid membrane layer [E.S. Stuart, R.W. Lenz, R.C. Fuller, Can J Microbiol 41(Suppl 1) (1995) 84 93], and is more consistent with a model consisting of a lipid monolayer containing embedded proteins [U. Pieper-furst, M.H. Madkour, F. Mayer, A. Steinbuchel, J. Bacteriol. 176 (1994) 4328-4337.] By altering the H/D content of the precursors, we were able to collect SANS data from preparations of both deuterated and H/D copolymer inclusions, where initial PHA produced was hydrogenated followed by deuteration. Deuterated inclusions showed minimum intensity above 90% D2O/H2O whereas the sequentially produced copolymer (assumed to be in a core/shell arrangement) displayed minimum scattering some 20% lower, which is consistent with the increased hydrogenation of the boundary layer expected from its synthesis during supply of hydrogenated followed by deuterated precursors. © 2006, Elsevier Ltd
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    Production and use of deuterated polyhydroxyoctanoate in structural studies of PHO inclusions
    (Elsevier, 2007-11-01) Russell, RA; Holden, PJ; Wilde, KL; Hammerton, KM; Foster, LJR
    This work reports on the biosynthesis of polyhydroxyalkanoates with medium chain length alkyl substituents in the side chain by Pseudomonas oleovorans using hydrogenated and deuterated substrates. These investigations aimed to obtain polyhydroxyalkanoates with varying degrees of deuterium substitution, and establish whether they are suitable analogues for structural investigation. In order to understand the formation and structure of inclusions in their native state, whole inclusions were isolated from microbial cells and were analysed using Small Angle Neutron Scattering. A contrast variation study was conducted on hydrogenated and deuterated inclusions of polyhydroxyoctanoate, as well as inclusions resulting from co-feeding or sequentially feeding different precursors. The data indicated a core/shell structure resulting from feeding hydrogenated followed by perdeuterated PHO precursor, and demonstrated the utility of this analysis for characterising chemically similar systems. © 2007, Elsevier Ltd.