Thesis (Ph. D.)--University of Missouri-Columbia, 2005. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Vita. Includes bibliographical references.

The viability of multicellular aerobic organisms requires the binding and transport of molecular oxygen from the atmosphere to sites of metabolism. In the earthworm, Lumbricus terrestris, erythrocruorins are freely dissolved multi-subunit protein complexes that serve the same functions as red blood cells The aims of this study were to 1) determine the overall arrangement of hemoglobin chains and non-hemoglobin chains in Lumbricus erythrocruorin, 2) determine the stereochemical determinants specifying erythrocruorin's hierarchical symmetry, and 3) investigate the molecular and chemical basis for the remarkable cooperative binding of ligands to earthworm hemoglobin. Erythrocruorin is a highly cooperative oxygen-carrying protein with Hill coefficients measured at some pH's as high as n = 7.9. Crystallographic analysis of the whole erythrocruorin molecule structure to 5.5 Å resolution reveals a hierarchical organization of 144 oxygen-binding polypeptides and 36 non-hemoglobin linker polypeptide chains. The hemoglobin chains are arranged in a novel dodecameric substructure at the periphery of the complex, whereas 36 linker chains comprise the inner core and projected triple-stranded, helical coiled-coil spokes towards the center of the complex. Interdigitation of these spokes appears crucial for stabilizing the complex. Crystallographic analysis of crystals from isolated hemoglobin chains provides greater detail (resolution = 2.6 Å) and complete atomic models for the hemoglobin polypeptides. Comparison of these models with other hemoglobins reveal unique features in the distal heme pocket, including large aromatic residues at the B10 position in three of the four hemoglobin chains. Aromatic residues at this position have been implicated in other hemoglobins to confer resistance to oxidation. Molecular interactions across each subunit include pH-dependent interactions that are consistent with the observed Bohr effect on oxygen binding. Specifically a π-cation interaction between an arginine of one subunit to a histidine of the opposing subunit is likely an important molecular switch in the allosteric transition from a low to high affInity ligand-binding state.

The crystal structures of Co₃(AsO₄)₂, Co₂₄ٜ₂As₉O₄₈, Co₂As₂O₇ and Co₇As₃ٜ₆O₁₆ have been determined by x-ray diffraction methods. The crystal structure of Mg₃(VO₄)₂ have been refined using single crystal x-ray diffraction data. General structural relations between M₃(XO₄)₂ type compounds where M refers to a divalent cation with radius comparable to that of cobalt, and x = As or V, are discussed. The deviations from ideality in cation polyhedral groups in crystal structures are analysed. / Thesis / Doctor of Philosophy (PhD)

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 6 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 4 uppsatser.

Diss. (sammanfattning) Umeå : Umeå universitet, 2010.

Biotin Protein Ligase (BPL) is an essential enzyme responsible for the covalent attachment of biotin to a specific lysine residue of biotin-dependent carboxylases, transcarboxylases and decarboxylases. Due to the fundamental processes that these enzymes are involved in such as lipogenesis, amino acid catabolism and gluconeogenesis, much research has been conducted on these enzymes. Studies encompassing structural, mutational and catalytic functions of these enzymes have lead to novel drug developments for the treatment of obesity, diabetes, metabolic syndrome, bacterial and fungal infections. As BPL is required for activation of these enzymes by biotinylation, it is believed that it too could be targeted in a similar way to produce novel therapeutics. To date, the most characterised BPLs are from the Gramnegative bacteria Escherichia coli and the archea Pyrococcus hirokoshii. However minimal information is known about other forms of clinically important bacterial species or eukaryotic forms of this important enzyme. Through my candidature I have compiled a thorough literature review summarised as chapter 1: Introduction. Furthering this literature analysis, a human BPL model was generated with aid of BPL structural co-ordinates already deposited in the protein data bank (PDB), thus allowing focus on human BPL mutations that cause multiple carboxylase deficiency (chapter 2). I have solved the structure of BPL from the clinically important pathogenic bacteria Staphylococcus aureus. This was performed in several ligand-bound and non-bound states (chapters 3 and 4). A novel high-throughput assay was developed to test BPL activity. This assay allow testing of compounds that could potentially inhibit the BPL from Candida albicans (a species responsible for invasive fungal infections) (chapter 5). Large amounts of highly purified BPL from Saccharomyces cerevisiae allowed for the first structural analysis of a eukaryotic BPL (Chapter 6). The work has been summarised by a general discussion and future directions for the project (Chapter 7). / Thesis (Ph.D.) -- University of Adelaide, School of Molecular and Biomedical Science, 2009

Thesis (Ph. D.)--University of Virginia, 2008. / Title from title page. Includes bibliographical references. Also available online through Digital Dissertations.

This thesis describes the synthesis and characterisation of metal complexes that contain chemically reduced bipyridyl ligands. The crystal structures of twenty-six novel complexes are reported alongside detailed discussions on the electronic and spectroscopic effects and trends associated with the different oxidation states within these species. Chapter One introduces the isomers of bipyridine and their redox chemistry, the concept of non-innocent ligands and the spectroscopic techniques that are currently used in determining ligand oxidation states. Subsequently, examples of main group, transition metal, lanthanide and actinide species that contain or may contain reduced forms of the ligand are discussed. Chapter Two details the synthesis and structural characterisation of alkali metal salts of singly and doubly reduced forms of the three commercially available bipyridine isomers. The effects of this reduction are investigated with the aim of developing diagnostic fingerprints for each of the ligand oxidation states. Chapter Three discusses the synthesis of an homologous series of compounds of the form [M(2,2'-bipy)(mes)₂]^n– where M = Cr, Mn, Fe, Co, Ni and n = 0, 1. Trends in magnetism, bonding and electronic structure are investigated with reference to theoretical calculations and the diagnostic fingerprints identified in the previous chapter. Chapter Four describes the synthesis and characterisation of three compounds containing the isostructural motif [Zn₂(4,4'-bipy)(mes)₄]^n– where n = 0, 1, 2. Structural and spectroscopic changes are discussed and com- pared to theoretical calculations. Chapter Five contains descriptions of the spectroscopic techniques employed in the above research and synthesis routes to all compounds featured in this thesis.

Hygromycin A (HygA) binds to the large ribosomal subunit and inhibits its peptidyl transferase (PT) activity. The presented structural and biochemical data indicate that HygA does not interfere with the initial binding of aminoacyl-tRNA to the A site, but prevents its subsequent adjustment such that it fails to act as a substrate in the PT reaction. Structurally we demonstrate that HygA binds within the peptidyl transferase center (PTC) and induces a unique conformation. Specifically in its ribosomal binding site HygA would overlap and clash with aminoacyl-A76 ribose moiety and, therefore, its primary mode of action involves sterically restricting access of the incoming aminoacyl-tRNA to the PTC. / Bizkaia:Talent and the European Union's Seventh Framework Program (Marie Curie Actions; COFUND; to S.C., A.S., T.K.); Marie Curie Actions Career Integration Grant (PCIG14-GA-2013-632072 to P.F.); Ministerio de Economía Y Competitividad (CTQ2014-55907-R to P.F., S.C.); FIRB Futuro in Ricerca from the Italian Ministero dell'Istruzione, dell'Universitá e della Ricerca (RBFR130VS5_001 to A.F.); Peruvian Programa Nacional de Innovación para la Competitividad y Productividad (382-PNICP-PIBA-2014 (to P.M. and A.F.)). Funding for open access charge: Institutional funding. / Revisión por pares