2 results for Adams, Julian James, Doctoral

  • Studies in protein structure : the structure and properties of the iron superoxide dismutase from Methanobacterium thermoautotrophicum : the structures of [beta]-lactoglobulin in two new crystal forms : a dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Institute of Fundamental Sciences at Massey University

    Adams, Julian James (2002)

    Doctoral thesis
    Massey University

    The crystal structure of Methanobacterium thermoautotrophicum iron superoxide dismutase (Mt-FeSOD) has been determined by X-ray diffraction to a resolution of 2.6 Å. The crystals were grown from PEG 6000 at a pH of 5.5, and the structure was solved by molecular replacement. The structure, in concert with structural and functional data from other Fe and Mn SODs, provides insights into aspects of metal specificity, reactivity of superoxide dismutase towards toward the inhibitor azide and deactivator hydrogen peroxide, and how the primary structure is involved in subtle tuning of these properties. The structure reveals how the protein is designed for thermal and chemical stability, yet retains moderate superoxide dismutase activity at ambient temperature. Bovine β-lactoglobulin (BLG) has been studied for many decades; numerous X-ray and NMR structures are available. Here we present two new X-ray structures, one from a crystal grown at very low ionic strength, and at the lowest pH (~5.2) of any X-ray structure. This structure provides validation of the other, high ionic strength X-ray structures. The core elements of BLG, an eight-stranded β-barrel, a three-turn α-helix external to the barrel, and an external β-strand (that forms the dimeric interface), are almost invariant across all structures. Four flexible loops have a variety of positions in the known structures and this represents a set of snapshots of the in vivo states of BLG. These flexible loops play an important role in the entropic stabilization of the β-barrel.

    View record details
  • A C₂-symmetric analogue of dppf : synthesis and characterization of indenyl-phosphines, phosphino-ferroindacenes and their coordination compounds

    Adams, Julian James (1998)

    Doctoral thesis
    University of Canterbury Library

    The synthesis, isolation and characterisation of a series of indenyl phosphines: 3-diphenylphosphinoindene (ppinH), 1,3- bis(diphenylphosphino)indene (dppinH), bis(3-indenyl)phenylphosphine (pdinH₂) and tris(3-indenyl)phosphine (ptinH₃) is reported. Until now these compounds have been either uncharacterized or poorly characterized in the literature. The reactions of ppin-, dppin- and pdin²- with ferrous chloride were investigated. Fe(ppin)₂ exists in two isomeric forms: a racemic isomer with C₂ symmetry and a meso form with C₂ symmetry, these are analogues of dppf. Crystallographic investigations of the coordination compounds of Fe(ppin)₂ allowed isolation of both isomers of the Fe(ppin)₂Mo(CO)₄ complex, and the meso isomer of the Fe(ppin)₂PdCb complex. Solution NMR investigations of Fe(ppin)₂PdCl₂ and Fe(ppin)2PtCl₂ show two compounds in solution in each case, suggesting a dynamic process. The electrochemistry of the complexed and uncomplexed ferroindacene show reversible oxidation processes in dry dichloromethane at E½ = -140 mV (Fe(ppin)₂), +60 mV (Fe(ppin)₂Mo(CO)₄) and +260 mV (Fe(ppin)₂PdCl₂) vs. Fe/Fc+. The investigation of the tetraphosphinoferroindacene Fe(dppin)₂ showed it only to be stable in dilute solution and that the major decomposition product is Fe(ppin)₂. The decomposition mechanism is unknown. The synthesis of diferrocenobis(phenylphosphino)cyclophane, an eight membered diferrocenlycyclophane characterized by mass spec and NMR, is described and the investigation of the indenyl analogue of diferrocenobis(phenylphosphino)cyclophane Fe₂(pdin)₂ which proved to be very unstable, is also described.

    View record details