No description available.

No description available.

No description available.

No description available.

No description available.

Australian marsupials are unique fauna that have evolved and adapted to unique environments and thus it is likely that their detoxification systems differ considerably from those of well studied eutherian mammals. This poses a problem in applying data from metabolic studies with eutherians to marsupials. Knowledge of these processes in marsupials is therefore vital to understanding the consequences of exposure to xenobiotics. As a result, there is a clear need for improved understanding of the metabolic capabilities of Australian marsupials, particularly at the molecular level. The current PhD candidature therefore focused on characterising the important xenobiotic-metabolising enzyme superfamily, cytochrome P450, with particular emphasis on the CYP3A subfamily, in Australian marsupials, namely koala (Phascolarctos cinereus), tammar wallaby (Macropus eugenii), Eastern grey kangaroo (Macropus giganteus) and the Southern hairy-nosed wombat (Lasiorhinus latifrons). / Expression of CYP3A-like protein using hepatic microsomes was detected by western blot analysis in all four marsupial species studied. Female koalas were observed to express higher levels of CYP3A-like protein than male koalas. CYP3A activity for each marsupial species was determined in hepatic microsomes using erythromycin, a known human CYP3A4 substrate. Erythromycin N-demethylation activity was detected in all marsupial hepatic microsomes, with highest activity observed in koala. Koalas displayed gender differences in activity with female koalas showing a significant 2-fold increase. Inhibition studies with troleandomycin showed decreased erythromycin activity in both female and male koalas. Erythromycin activity in wallaby and kangaroo microsomes was notably lower than observed in koala. No gender differentiation was noted in wallaby or kangaroo. This observed difference in CYP3A activity between species may be indicative of the koala's eucalyptus diet. / Full-length CYP3A cDNAs were isolated from both koala and Eastern grey kangaroo. These clones are the first CYP3A sequences to be cloned from any marsupial species. Given the significant role that CYP3A enzymes play in the metabolism of both endogenous and exogenous compounds, these clones provide an important step in elucidating the metabolic capacity of marsupials. / The CYP2C subfamily was also investigated in koala using two previously cloned CYP2C members, CYP2C47 and CYP2C48. Site-directed mutagenesis was used to engineer the CYP2C48 cDNA into a suitable form for expression. Stable cell lines were generated for both CYP2C and CYP3A full-length cDNAs using a mammalian expression system. These cell lines were used to determine catalytic activity of the marsupial CYPs. / Multiple protein alignments were used to identify substrate recognition sites and critical residues involved in the metabolism of a variety of substrates. Sequence analysis of the deduced amino acid sequence of the CYP3A clones has highlighted important species-specific features, for example a Thr residue at position 119 which has only been found in a limited number of species, including koala, and has been shown to influence steroid metabolism. / Modelling of all marsupial CYP2C and CYP3A full-length cDNAs and phylogenetic analysis of all known marsupial cDNA sequences was performed. These studies highlight the need for inclusion of marsupial information when assessing mammalian evolution. / Collectively, the work presented here provides valuable insights into the marsupial CYP2C and CYP3A subfamilies and highlights the significance of species differences in xenobiotic metabolism. / Thesis (PhDPharmacy)--University of South Australia, 2005.

This thesis reports the synthesis and copper coordination chemistry of covalently-linked aryl-imidazole derivatives designed as models for the crosslinked imidazole-phenol sidechains of the His-Tyr cofactor in the CcO. Three new imidazole- (HL1 - HL3) and three new indole- (HL4 - H2L6) containing tripodal ligands were synthesised. The conjugate addition of an imidazole to activated quinone derivatives was developed as a new route to organic models for the Tyr His cofactor. Two monodentate imidazole-aryl, Im-hq(OH)2 and Im-ArOH, and an imidazole-quinone, Im bq were obtained using this route. The X-ray crystal structure of Im-hq(OH)2.EtOH was determined. The route was also used to give new chelating ligands, H2L10 and HL12, containing a cross-linked imidazole-phenol surrogate for the Tyr244-His240 cofactor. Copper complexes of Im-hq(OH)2, Im-bq, Im-ArOH, H2L10-HL12, and HL1-H2L6 were prepared, and the X-ray crystal structures of [Cu(terpy)(Im-bq)][BF4]2 and five other copper complexes were determined. The physiochemical properties of the copper complexes were characterized by FT-IR, UV-Vis-NIR, EPR and (spectro)electrochemical studies. Key results include: the oxidation of Im-ArO- anion affords the semiquinone radical, Im-sq(4OH)(1O??????), in a hydrous solvent. However, the oxidations of neutral Im-ArOH and [Cu(tpa)(Im-ArOH)]2+ produce the corresponding phenoxy radical species that rapidly and reversibly dimerise to give quinol cyclohexadienone, QCHD, dimers. Significantly [Cu(tpa)(Im-sq(4OH)(1O??????))]2+ was EPR silent, perhaps due to antiferromagnetic coupling between the Cu(II) (S=1/2) and semiquinonyl radical (S=1/2) centres. Deprotonation of the hydroquinone in [Cu(tpa)(Im-hq(OH)2]2+ produces the hydroquinone dianion which reduces the Cu(II) centre. The semiquinone radical is coordinatively labile and dissociates from the Cu(I) centre. The biological implications of these results are mentioned.

Thesis (M.S.)--University of Texas at Dallas, 2007. / Includes vita. Includes bibliographical references (leaves 62-64)

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 9 uppsatser.