Thesis (M.Med.Sc.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 30-31). Also available in print.

Thesis--Virginia Polytechnic Institute and State University. / Vita. Abstract. Includes bibliographical references (leaves 113-116). Also available via the Internet.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Sydney, 2008. / Includes graphs and tables. Title from title screen (viewed November 28, 2008) Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the School of Chemistry, Faculty of Science. Includes bibliographical references. Also available in print form.

Theoretical methods for studying molecules of biological importance are reviewed, both ab initio and semi-empirical. The Group Function Approach is developed in detail in its strong orthogonal form and corrections to the energy are added for taking into account non-orthogonality effects, depending on the overlaps of the group functions. Approximations are introduced and tested so that this method can be applied to large molecules. In particular, a system (or a relevant fragment of it) is built up from localized two-electron groups, each one described by a two-electron group function (geminal). Each group function is optimized by using an SCF method with an effective hamiltonian consisting of the two-electron hamiltonian of the group together with the effective potential due to the presence of the other electron groups (and to the external environment, eventually). The wavefunction for the whole molecule is an antisymmetrized product of geminals. The energy is computed as a sum of group contributions. Corrections, depending on up to the second power of the overlaps of two groups at a time, are particularly important in conformational studies. The approximations introduced are based on the consideration that distant groups consisting of two positive and two negative charges see each other as neutral entities and thus do not contribute appreciably in the definition of the effective hamiltonian: the computing effort is greatly reduced in this way, the error introduced is small and can be estimated easily. The theoretical method presented in this thesis offers a powerful tool for making qualitative predictions of the changes resulting from localized effects, such as twisting around a bond, and it can be usefully applied to conformational studies and geometry optimizations. The other properties which can be calculated axe for the most part directly related to the electron density; this determines, for example, the electrostatic potential outside a molecule and hence the position of attack by approaching ions or polar species. Chemical reactions, which involve breaking or re-arrangement of bonds, provide another vast field of application. Such processes usually involve only localized regions in a molecule and the admission of intragroup CI ensures that the study of bond breaking remains valid throughout the whole process. All necessary computer programmes have been developed and numerical applications have been made to a range of molecules, including hydrocarbons, small molecules containing double bonds and lone pairs, and the amino acid glycine.

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No description available.

Binary (e,2e) spectroscopy is an intermediate energy electron scattering coincidence technique measuring the binding energy and spherically-averaged momentum distributions of individual valence electrons in small gaseous molecules. Momentum space chemistry is a term used to refer to the study of the attributes of molecular orbitals in the momentum space representation, rather than the usual position space representation. The relation between the two spaces is the Fourier Transform. This thesis discusses experimental measurements and theoretical calculation of the binding energy spectra and/or momentum distributions of. H₂S, COS, C0₂, NO and 0₂ in detail. It also attempts to bring into the ken of ordinary chemistry concepts and principles for dealing with momentum-space molecular orbital density functions, which are essential to the understanding of the nature of momentum distributions. In order to illustrate this, specific examples of theoretical momentum and charge density maps for several molecules are discussed. Significant new understanding of the electronic structure of these molecules is attained. The design, construction, and preliminary testing of a new binary (e,2e) spectrometer incorporating a multi-channel plate detector for improved data collection efficiency is presented. Finally, some propositions for future directions of study are put forward. / Science, Faculty of / Chemistry, Department of / Graduate

No description available.

<p>The classical approach to gene discovery has been to culture micro-organisms demonstrating a specific enzyme activity and then to recover the gene of interest through shotgun cloning. The realization that these standard microbiological methods provide limited access to the true microbial biodiversity and therefore the available microbial genetic diversity (collectively termed the Metagenome) has resulted in the development of environmental nucleic acid extraction technologies designed to access this wealth of genetic information, thereby avoiding the limitations of culture dependent genetic exploitation. In this work several gene discovery technologies was employed in an attempt to recover novel bacterial laccase genes (EC 1.10.3.2), a group of enzymes in which considerable biotechnological interest has been expressed. Metagenomic DNA extracted from two organic rich environmental samples was used as the source material for the construction of two genomic DNA libraries. The small insert plasmid based library derived from compost DNA consisted of approximately 106 clones at an average insert size of 2.7Kbp, equivalent to 2.6 Gbp of cloned environmental DNA. A Fosmid based large insert library derived from grape waste DNA consisted of approximately 44000 cfu at an average insert size of 25Kbp (1.1 Gbp cloned DNA). Both libraries were screened for laccase activity but failed to produce novel laccase genes. As an alternative approach, a multicopper oxidase specific PCR detection assay was developed using a laccase positive Streptomyces strain as a model organism. The newly designed primers were used to detect the presence of bacterial multicopper oxidases in environmental samples. This resulted in the identification of nine novel gene fragments showing identity ranging from 37 to 94% to published putative bacterial multicopper oxidase gene sequences. Three clones pMCO6, pMCO8 and pMCO9 were significantly smaller than those typically reported for bacterial laccases and were assigned to a recently described clade of Streptomyces bacterial multicopper oxidases.</p> <p><br /> Two PCR based techniques were employed to attempt the recovery of flanking regions for two of these genes (pMCO7 and pMCO8). The use of TAIL-PCR resulted in the recovery of 90% of the pMCO7 ORF. As an alternative approach the Vectorette&trade / system was employed to recover the 3&rsquo / downstream region of pMCO8. The complexity of the DNA sample proved to be a considerable technical challenge for the implementation of both these techniques. The feasibility of both these approaches were however demonstrated in principle. Finally, in an attempt to expedite the recovery of fulllength copies of these genes a subtractive hybridization magnetic bead capture technique was adapted and employed to recover a full &ndash / length putative multicopper oxidase gene from a Streptomyces strain in a proof of concept experiment. The StrepA06pMCO gene fragment was used as a &lsquo / driver&rsquo / against fragmented Streptomyces genomic DNA (&lsquo / tester&rsquo / ) and resulted in the recovery of a 1215 bp open reading frame. Unexpectedly, this ORF showed only 80% identity to the StrepA06pMCO gene sequence at nucleotide level, and 48% amino acid identity to a putative mco gene derived from a Norcardioides sp JS614.</p>