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The object of the research described in this thesis is to provide, by means of laboratory experiments, data required to understand the atmospheric chemistry of the nitrate radical, from both a mechanistic and kinetic point of view. The low pressure discharge-flow kinetic technique coupled detection of the NO₃ radical by optical absorption was used to measure the temperature-dependent rate coefficients for the reaction of NO₃ with 1-butene, 1-chloro-l-butene, 2-chloro-2-butene, 3-chloro-l-butene, 1-chloro-2-butene, 2-chloro-2-butene, 1-chloromethylpropene, 3-chloromethylpropene, 3-bromo-1-butene, 4-bromo-l-butene and 2-bromo-2-butene. The atmospheric implications for the reaction of NO₃ with these compounds are discussed. In order to understand the patterns of reactivity towards NO₃ exhibited by these compounds, a number of approaches were adopted. First, a non-quantitative approach employing the simple ideas of inductive and mesomeric effects. Secondly the observed reactivity of NO₃ towards these compounds was discussed, quantitatively, in terms of the relative energies of the interacting orbitals. This quantitative analysis required an extensive set of molecular orbital calculations were undertaken at various levels of sophistication. A good correlation was found, for compounds not containing vinylic halogen atoms, between -E(HOMO) and the measured rate constant; the data were used also to calculate "group-reactivity factors". In an extension to this work a new empirical correlation is presented that takes account of the contribution, in terms of the atomic orbital coefficients, of vinylic halogen atoms to the observed rate constant. To provide support for these calculations, work was undertaken using photoelectron spectroscopy to characterise experimentally the individual molecular orbitals. A correlation between the inverse of the molecular polarisability and the activation energy of the reaction is also described. Complementary work was undertaken in a unconventional flash-photolysis system to look at the kinetics of the reaction NO₃ + NO₃ andlongrightarrow; 2 NO₂ + O₂ over a pressure range of 2 to 100 Torr in helium. The measured rate coefficient was found to be pressure independent and to have a value of (2.2±1.0) x 10^-16 cm₃ molecule^-1 s^-1. The experimental work on the nitrate radical was extended to look at the laser-induced fluorescence (LIF) spectrum and at the quenching of the excited state of the nitrate radical.

The channel flow method has established the net dissolution kinetics of calcite single crystals at high pH (7.7-9.7) and varying bulk Ca²⁺ concentrations (0-10 mM), using wide ranges of solution flow rates (10^-3-0.3 cm³ s^-1). Literature rate equations were in poor agreement with experiment. Modelling with the following mechanism, where Ca²⁺ and CO₃^2- undergo Langmuirian adsorption: Ca²⁺_(aq) ⇄ Ca²⁺_(ads) CO^2-</sub>3 (aq)</sub> ⇄ CO^2-_{3 (ads)} Ca(sup>2+</sup></sub>(ads)</sub> + CO^2-_{3 (ads)} ⇄ CaCO_{3 (ads)} CaCo_{3 (ads)} → CaCo_{3 (lattice)} and the consequent rate law J_net/mol cm<sup>-2</sub>s^-1 = k_pK_CaK_CO₃ {K_sp - [Ca²⁺]_o[CO^2-₃]_o (1 + K_Ca[Ca²⁺]_o)(1 + K<sub>CO₃[CO^2-₃]_o) gave excellent agreement with experiment under all conditions studied. This mechanism is shown to explain all literature streaming potential, electrophoresis and kinetic salt effect data. Dissolution of calcite under the above conditions was strongly inhibited by Mg²⁺ and fully deprotonated forms of succinic acid, 2-sulphobutanedioic acid, phthalic acid and maleic acid. Mechanisms were established; for the maleate dianion, the inhibition was due to the blocking of the dissolution sites at which CaCO₃ units are incorporated into the crystal lattice. For the other ions, inhibition arose from competitive Langmuirian adsorption either between CO₃<sup>2-<sup> and the anions, or between Ca²⁺ and Mg²⁺. A new method to quantify the inhibited dissolution of particulate CaCO₃ (=10 μm) via enhanced mass transport of solution to the rotating disc electrode, due to the rotation of the particles in the diffusion layer, has been established. Good agreement was found with that measured independently using the channel flow cell. A.c. impedance spectroscopy has been used to characterise scaled (CaCO₃) steel tubes. Results provide scope for (i) monitoring scale growth, and (ii) use in safety control devices for alerting to the scaling of pipe-work.

Ascorbic acid has been found to promote nitrosothiol decomposition via two pathways. In the first, ascorbic acid acts as a reducing agent for added or adventitious copper (II), producing copper (I). This reacts with the nitrosothiol, giving nitric oxide and disulfide as the ultimate products. The reaction requires only small quantities of ascorbic acid, and is catalytic in copper. The second pathway requires higher concentrations of ascorbic acid, the stoichiometry being one mole of ascorbic acid to two moles of nitrosothiol. The products are nitric oxide and thiol, and the reaction has been interpreted in terms of rate limiting nucleophihc attack by ascorbate at the nitroso nitrogen, followed by decomposition of the 0-nitroso ascorbate formed to nitric oxide and dehydroascorbic acid. The rate equation is first order in both the nitrosothiol and ascorbic acid, and the entropy of activation is significantly negative. pH - rate profiles reveal the ascorbate dianion is much more reactive than the monoanion, and that the neutral form has negligible reactivity. Nitrosation of thione-containing nitrogen heterocycles by nitrous acid leads to the equilibrium formation of =SNO(^+) species; large equilibrium constants are observed. The reactions exhibit many of the features generally observed in nitrosation, including catalysis by halides and thiocyanate, and some participation by dinitrogen trioxide as a nitrosating agent. The nitrosation rate constants are large, approaching values representing the encounter-controlled limit. The =SNO(^+) species are generally unstable, decomposing under acidic conditions to nitric oxide and a disulfide. Decomposition of S-nitrosated 4-thiopyridine showed hydrolysis occurs at pH 7.4, re-forming the thione. The nitroso species reacts rapidly with ascorbate, forming nitric oxide and thione.

The main objective of this research is to advance our understanding of the biochemical properties and the structure-function relationships of the chloroplast glycerol-3-phosphate acyltransferases in plants. De novo synthesised fatty acyl chains are diverted into the prokaryotic pathway of plant lipid biosynthesis by a soluble glycerol-3-phosphate acyltransferase (GPAT [EC. 2.3.1.15]) in the chloroplast. GPAT catalyses acylation at the sn- 1 position of sn-glycerol-3-phosphate to form lysophosphatidic acid. Recombinant GPAT from squash and Arabidopsis were overproduced in Escherichia coli, purified to about 23- fold and 90% pure enzyme using a procedure developed in this study. Antibodies were raised in rabbits against these denatured recombinant GPAT preparations and four peptide antigens, and preliminary experiments were performed to test their suitability for use in Western blotting. In collaboration with the University of Sheffield, squash GPAT was successfully crystallised, isomorphous heavy metal derivatives prepared and the complete 3-dimensional structure of the protein at 2.3 Angstrom resolution determined. The cloning, functional expression and characterisation of a novel GPAT from oil palm, 'domainswap' chimeric recombinant proteins of Arabidopsis and squash GPAT, and spinach and squash GPAT respectively, and the influence of the N-terminal domain and amino acid substitutions in the C-terminal domain of the squash GPAT, was described. By determining the apparent kinetic constants for acyl-ACP substrates of most of the enzymes and by in vitro assays using mixtures of two acyl-ACP substrates under physiologically relevant conditions, it was found that their substrate selectivities could be dramatically altered. The development of ribozyme- technology as a molecular tool to down-regulate the gene expression of one out of multiple GPATs, was initiated. The strategy would allow for a phenotypic indication of ribozyme- efficacy in vivo and may help further contribute to the role of glycerol-3-phosphate acyltransferase in processes determining the phenomenon of chilling-sensitivity of plants.

Under the assumption of mass-action kinetics, systems of chemical reactions can give rise to a wide variety of dynamical behaviour, including stability of a unique equilibrium concentration, multistability, periodic behaviour, chaotic behaviour, switching behaviour, and many others. In their canonical papers, M. Feinberg, F. Horn and R. Jackson developed so-called Chemical Reaction Network theory which drew a strong connection between the topological structure of the reaction graph and the dynamical behaviour of mass-action systems. A significant amount of work since that time has been conducted expanding upon this connection and fleshing out the theoretical underpinnings of the theory. In this thesis, I focus on three topics within the scope of Chemical Reaction Network theory. 1. Linearization: It is known that complex balanced systems possess within each invariant space of the system a unique positive equilibrium concentration and that that concentration is locally asymptotically stable. F. Horn and R. Jackson determined this through the use of an entropy-like Lyapunov function. In Chapter 4, I approach this problem through the alternative approach of linearizing the mass-action system about its equilibrium points. I show that this approach reproduces the results of F. Horn and R. Jackson and has the advantage of being able to give explicit exponential bounds on the convergence near equilibria. 2. Persistence: A well-known limitation of the theory is that the stabilities of the positive equilibrium concentrations guaranteed are locally limited. The conjecture that the equilibrium concentrations of complex balanced systems are global attractors of their respective invariant spaces has become known as the Global Attractor Conjecture and has received significant attention recently. This theory has been significantly aided by the realization that trajectories not tending toward the set of positive equilibria must tend toward the boundary of the positive orthant; consequently, persistence is a sufficient condition to affirm the conjecture. In Chapter 5, I present my contributions to this problem. 3. Linear Conjugacy: It is known that under the mass-action assumption two reaction networks with disparate topological structure may give rise to the same set of differential equations and therefore exhibit the same qualitative dynamical behaviour. In Chapter 6, I expand the scope of networks which exhibit the same behaviour to include ones which are related by a non-trivial linear mapping. I have called this theory Linear Conjugacy theory. I also show how networks exhibiting a linear conjugacy can be found using the mixed integer linear programming (MILP) framework introduced by G. Szederkenyi.

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Bibliography: leaves 178-210. / xiii, 230 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis examines the effects of endurance exercise training on whole body blood lactate removal, and the production and removal of blood lactate by skeletal muscle. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physiology, 1997?

Includes bibliographical references / 125 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physical and Inorganic Chemistry, 1969

Typewritten / Includes bibliographical references / 232 leaves ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physical and Inorganic Chemistry, 1964