Browsing by Author "McColl, G"

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    Simultaneously localising biometals within the high resolution ultrastructure of whole C. elegans
    (Australian Microscopy and Microanalysis Society, 2016-02-04) Jones, MWM; McColl, G; van Riessen, GA; Phillips, NW; Vine, D; Abbey, B; de Jonge, MD
    Ptychography is a coherent diffraction imaging method where multiple overlapping diffraction frames are combined, providing high resolution images of the electron density of extended objects. Recently, X-ray ptychography has seen many efficiency improvements that allow large areas to be imaged rapidly, making simultaneous X-ray ptychography and fluorescence microscopy experimentally viable. Here we use simultaneous X-ray fluorescence microscopy and ptychography to image entire C. elegans, with sub-micron and sub 100 nm elemental and ultrastructure resolutions respectively. Rapid data collection allowed the entire 1 mm long animal to be imaged in only a few hours. With the information from both techniques, the elemental maps can be viewed in the context of the high resolution ultrastructure, allowing further insights into the localisation of the fluorescent signal.
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    Studying biological coordination chemistry: a useful role for low latency, energy-dispersive photon counting XRF detectors
    (Australian Microscopy and Microanalysis Society, 2016-02-04) James, S; de Jonge, MD; McColl, G; Burke, R; Paterson, DJ; Howard, DL; Hare, D
    Day to day cellular function is fundamentally dependent on electron transfer reactions mediated by transition metals, often iron and/or copper. The biological consequences of this metal-catalysed redox chemistry arise from biochemical context generated via the multi-scale organisation of biological systems, i.e. the local concentration of metal → the nature of the donor atoms and bonding environment within the ligand → the location and abundance of the ligand within the cell → the suite of metal-ligand complexes comprising a cell’s metallome → the differences between one cell’s instance of it’s metallome compared to another within and between tissues. Biochemical insight must be anchored to the structural biology of the cell. In this view, understanding metallobiology requires us to interrogate the coordination environment of biological metal-ligand complexes in situ, and the lack of suitable probes limits our appreciation for the role metallobiology plays in health and disease. Ideally, such probes must exhibit extremely high specificity, sensitivity, and spatial resolution; requirements met by scanning X-ray fluorescence microscopy (XFM) and X-ray Emission Near Edge Structure (XENES). Advances in energy-dispersive detector technology have enormously enhanced the efficiency and speed of data acquisition when performing XFM and XENES measurements. When using the Maia detector system installed at the Australian Synchrotron XFM beamline the distribution of biometals can be mapped at rates in excess of 3 M pix / hr. This speed reduces imaging dose whilst maintaining counting statistics. Exploiting these technical advances we have undertaken a multi-pronged assault on characterising elemental distribution and speciation in a variety of whole- organism biological systems, including Caenorhabditis elegans and Drosophila melanogaster. We have utilised projective elemental mapping and 3D visualisations of elemental distributions to assess the distribution of chemical speciation through XENES imaging and tomography. The complementarity of these studies demonstrates that volumetric chemical speciation is achievable with the right instrumentation and approach to measurement but projective imaging can still provide a window into fundamental biological processes. Opportunities and challenges associated with visualizing in situ biometal speciation will be discussed.