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Title page, table of contents and summary only. The complete thesis in print form is available from the University of Adelaide Library. / Assimilable nitrogen, which is typically lacking in grape juice, is an important nutritional requirement of Saccharomyces cerevisiae. As such, fermentations frequently become protracted, terminate prematurely or develop undesirable aroma profiles. Amino acids and ammonium are the main sources of assimilable nitrogen in grape juice. The amino acid proline often predominates. Proline uptake is mediated by a high affinity, proline-specific permease, Put4p, and a low affinity general amino acid permease, Gap1p. The expression and activity of these transporters is subject to nitrogen catabolite repression (NCR) and nitrogen catabolite inactivation (NCI). That is, in the presence of a preferred nitrogen source, the expression of PUT4 and GAP1 is repressed and the permeases are inactivated. For yeast to fully exploit proline, its transport must be derepressed by depletion of other (preferred) amino acids and molecular oxygen must be present to allow proline catabolism by proline oxidase. Consequently, as oxygen is typically depleted well before the other amino acids in grape juice are reduced to non-repressive concentrations, proline is largely un-utilised by yeast during oenological fermentation. This study aims to overcome these metabolic restrictions on proline utilisation. A preliminary study was conducted to determine the potential for proline transport-capable strains to utilise proline during the initial stages of fermentation when oxygen may be present, particularly in red grape must. Initially, the transcriptional regulation of the PUT4 gene was targeted to generate strains capable of proline transport under normally repressive conditions. In the first case, the URE2 gene, encoding a negative regulator involved in nitrogen discrimination, was deleted. In the second case, PUT4 was expressed from the constitutive TEF2 promoter. It was observed that both strains express PUT4 in the presence of a preferred nitrogen source. This expression led to Put4p activity during the initial stages of growth and fermentation, with Put4p activity declining over the course of the growth phase. Proline removal from the media, however, was limited to the initial stages of fermentation while oxygen was available. It seems that the rapid depletion of oxygen limits the amount of proline transported into the yeast cell. The two proline transport-capable mutants were analysed for growth and fermentation characteristics. It was found that the deletion of the URE2 gene led to a slow initial growth and the formation of a larger biomass. The ure2 delete strain also utilised significantly more nitrogen during fermentation than the wild type. Consequently, a ure2 delete strain would not be suitable for industrial use. The expression of PUT4 from a constitutive promoter did lead to an increase in nitrogen assimilation during fermentation when compared with the wild type. However, this observed increase was significantly less than that observed in the ure2 delete strain. In an effort to produce a proline transport-capable strain with potential industrial benefit, strains constitutive for PUT4 specifically were isolated using random, in vitro mutagenesis of the PUT4 promoter region. Four point mutations were identified that, when introduced singly into the PUT4 promoter, led to expression of PUT4 in the presence of a preferred nitrogen source. The rapid depletion of oxygen observed in the preliminary study will limit the potential usefulness of strains capable of proline transport. Micro-oxygenation is rapidly becoming an accepted practice during oenological fermentation. The potential benefit of the controlled addition of oxygen during fermentation is restricted by the timing of any oxygen addition. Oxygen additions made at the onset of the stationary phase are the most beneficial. During the preliminary study, it was noted that Put4p activity decreased during the growth phase to low levels at the onset of the stationary phase. To ensure that sufficient active Put4p is present at the onset of the stationary phase, the post-translational control of the Put4p was investigated. Site-directed mutagenesis was used to target residues in the carboxy-terminal region of Put4p that are potentially involved in the ammonia-induced down-regulation of the permease. The substitution, S605A, lead to the amelioration of ammonia-induced down-regulation of Put4p. The activity of the Put4p S605A variant decreased over the course of the growth phase, but not to the same extent observed in the wild type. Furthermore, a recovery seen after down-regulation restored a greater percentage of the original activity compared with the wild type. To determine whether such a strain proved better able to ferment media in the presence of micro-oxygenation, the fermentation kinetics of a strain constitutively expressing PUT4(S605A) were compared with the wild type. Micro-oxygenation of ferments did not result in an increase in fermentation rate nor a decrease in fermentation time in the mutant. However, the cell viability of the strain capable of proline transport was increased in comparison with the wild type, suggesting a role for proline in stress responses within the yeast cell. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1048932 / Thesis (Ph.D.) -- University of Adelaide, Dept. of Horticulture, Viticulture and Oenology, 2002

This thesis reports a study of polydentate amino acid complexes of cobalt(III). The complexes prepared during this project have been characterized by a range of techniques, including ¹³C{¹H} and ¹H NMR spectroscopy, UV-visible spectroscopy, infra-red spectroscopy, elemental analysis and single crystal X-ray structure determination. A total of seven single crystal X-ray structure determinations have been performed during these studies. The imino acid polydentate complex, [Co(Aim₂trien)]₂[ZnCl₄], was reduced to the corresponding amino acid complex, [Co(A₂trien)]Cl, where as many as ten diastereoisomers could be formed due to the formation of new stereogenic centres. The crude product of these reactions was a mixture of isomers, according to ¹³C{¹H} NMR data. These isomers were separated using ion-exchange chromatography. The major isomer (I1), a minor isomer (I2a) and a half reduced complex (I4a) from the [Co(A₂trien)]Cl reduction and separation experiment were characterised. The predominant isomers produced were found to have had the proton on the α-carbon atoms positioned on the amine face of each amino acid ligand fragment. To investigate the ratio of the isomers formed by the initial borohydride reduction, an isomerisation study of the major isomer of the [Co(A₂trien)]⁺ complex (I1) was performed. This study hoped to establish the degree to which the distribution of isomers was a result of dynamic equilibrium. Experiments on a small scale showed the initial isomer distribution to be similar to that obtained from the borohydride reduction reaction. However, prolonged exposure to the carbonate buffer (≈ two weeks) resulted in isomers not previously seen. Experiments on a large scale were performed to establish whether the results were consistent. The materials from both the two hour and two week experiments were mixtures of isomers by ¹³C{¹H} NMR spectroscopy and were separated using ion-exchange chromatography. ¹H NMR data of the two hour experiment showed only epimerisation of the amine proton adjacent to the α-carbon atom. Therefore the isomers produced from the isomerisation of I1 have the same configuration of the proton on the α-carbon atoms, which is on the amine face of each amino acid chelate ring. ¹H NMR data from the two week experiment resulted in new isomers not previously seen as both the amine proton and the proton on the α-carbon atom have been epimerised. The polyamine wrapping around the central metal ion may also have changed in some cases. It would appear, from the ¹H NMR data that the methyl group signals of these isomers fall in two distinct clusters; a cluster at δ 1.50-1.65 ppm and a cluster at δ 1.40-1.49 ppm. From these results, and the results of Chapter Two, it has been calculated that there is at least 92% facial selectivity for the amine face of the molecule during the initial borohydride reduction reactions. This may be due to a di-hydrogen bonding interaction between an adjacent amine proton and a hydride of the borohydride, which directs the attack. Following on from this study, a new range of imino and amino acid complexes were synthesised using different tetraamine and pentaamine cobalt(III) complexes. X-ray quality crystals of [Co(Aim₂2,2,3-tet)][ClO₄] and [Co(Aim₂2,3,2-tet)][ClO₄] were obtained and solved with assistance from Dr. Chris Fitchett and Dr. Jennifer Burgess. Borohydride reductions were performed on the [Co(Aim₂2,2,3-tet)]⁺ and [Co(Aim₂2,3,2-tet)]⁺ systems. The products were a mixture of isomers according to 1H and ¹³C{¹H} NMR spectroscopy. The results from the ¹H NMR experiments showed similarity between the [Co(A₂2,3,2-tet)]⁺ and [Co(A₂trien)]⁺ systems, where three major stereoisomers were present in solution. Analogous results for the asymmetric [Co(A₂2,2,3-tet)]⁺ system were also observed. Preliminary attempts have been made to separate these isomers using ion-exchange chromatography.

Thesis (Ph. D.)--University of Montana, 2008. / Title from title screen. Description based on contents viewed May 6, 2009. Includes bibliographical references (p. 76-86).

Thesis (Ph. D.)--Washington State University, May 2008. / Includes bibliographical references (p. 88-98).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1965. / Vita. Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph.D.)--Biology, Georgia Institute of Technology, 2008. / Committee Chair: Jordan, I. King; Committee Member: Borodovsky, Mark; Committee Member: Bunimovich, Leonid; Committee Member: Choi, Jung; Committee Member: McDonald, John.

Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Yucel Altunbasak; Committee Co-Chair: Mark Borodovsky; Committee Member: Brani Vidakovic; Committee Member: Ghassan Alregib; Committee Member: James McClellan; Committee Member: Russel Mersereau. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Vita. Includes bibliographical references (leaves 63-65). Also available on the Internet.