Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references (leaves 96-103). Also available in electronic version.

Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

Quinolinate phosphoribosyltransferase (QPRTase, E.C. 2.4.2.19) is considered to be a unique enzyme in that it is thought to catalyse two distinct chemical reactions. Both the transfer of a phosphoribosyl group from 5-phosphoribosyl-1- pyrophosphate onto the nitrogen of quinolinic acid and the subsequent decarboxylation of the intermediate to form nicotinic acid mononucleotide are thought to be catalysed by the QPRTase system. Analogues of quinolinic acid were designed as potential inhibitors of QPRTase. These contain acidic groups at the 2- and 3- positions but are unable to decarboxylate. However, such compounds may be able to undergo the phosphoribosyl transfer reaction, potentially increasing their inhibitory potency. These compounds may be useful as "biological tools" allowing the neurological effects of an increase in quinolinic acid levels to be investigated. The compounds may show anti-fungal activity blocking the kynurenine pathway for NAD production. 2-Sulfonicotinic acid was synthesised by the oxidation of 2-mercaptonicotinic acid by either basic potassium permanganate, or iodine, with the structure was confirmed by X-ray crystallography. In biological testing the acid was shown to be neither an agonist nor antagonist of the NMDA receptor, or to be neurotoxic. A number of synthetic routes towards 2-phosphononicotinic acid, an alternative quinolinic acid analogue, were attempted though none were successful. These included orthometallation strategies and palladium coupling reactions to incorporate the phosphonic acid group at the 2- position. Nucleophilic addition routes, methods of building up the pyridine ring and including non-selective phosphonic acid addition were also examined. However, a related derivative, 2-(phosphonomethyl)nicotinic acid, was successfully synthesised. The non-enzymic decarboxylation of N-alkyl quinolinic acids was investigated, for comparison with the decarboxylation reaction catalysed by QPRTase. Both N- methyl and N-ethylquinolinic acid were synthesised, and the pH versus rate profiles measured. The rate maximum for both compounds was at pH 1.5, with the rate decreasing both above and below the maximum. N-Methylquinolinic acid was 10 times faster than quinolinic acid itself, demonstrating the effect of the nitrogen substituent. The N-ethyl derivative decarboxylated a further 1.5 times faster, showing the effect of increasing the size of the substituent. An Arrhenius plot was also carried out, giving an activation energy for the reaction of 153 kJ mol-1. Attempts to prepare the N-propyl derivative were unsuccessful, as decarboxylation occurred very readily to give N- propylnicotinic acid.

published_or_final_version / Paediatrics / Doctoral / Doctor of Philosophy

published_or_final_version / Medicine / Doctoral / Doctor of Philosophy

No description available.

"Research conducted at the Department of Haematology, Hanson Centre for Cancer Research, Institute of Medical and Veterinary Science."--T.p. Includes bibliographical references (leaves 170-214). Elevated levels of receptor tyrosine kinases have been implicated in carcinogenesis. It is possible that high expression of c-Kit by the leukaemic cell provides them with a growth advantage over their normal counterparts in the bone marrow microenvironment. Thus, a means of inhibiting the interaction of c-Kit on these cells with ligand Steel Factor may remove proliferation and survival signals. Main aim of the study was to produce a biological inhibitor of this interaction and evaluate its ability to prevent ligand Steel Factor from binding to c-Kit on live cells.

Copy of author's previously published work inserted. Includes bibliographical references (leaves 160-182). Concentrates mainly on the characterisation of the molecular mechanism of action of the tec protein tyrosine kinase using biochemical and genetic approaches.

Bibliography: leaves 139-165.

Bibliography: leaves 139-165. / ix, 183 leaves : ill. (some col.) ; 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 Biochemistry, 2001