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Thesis (Ph.D.) -- McMaster University, 1998. / Includes bibliographical references (leaves 149-166). Also available via World Wide Web.

Thesis (Ph.D.) -- University of Newcastle, 2003. / School of Mathematical and Physical Sciences. Includes bibliographical references (p. 161-162). "Also available online".

Thesis (Ph.D. in Information Sciences)--Naval Postgraduate School, September 2007. / Dissertation Advisor(s): Nissen, Mark ; Arquilla, John "September 2007." Includes bibliographical references (p. 239-277). Also available via the Internet.

Diss. (sammanfattning) Uppsala : Univ., 2002. / Härtill 3 uppsatser.

Thesis (M.Sc.) - Carleton University, 2005. / Includes bibliographical references (p. 61-63). Also available in electronic format on the Internet.

Thesis--PlanB (M.S.)--University of Wisconsin--Stout, 1999. / Field project. Includes bibliographical references.

Thesis (M.S.)--Rochester Institute of Technology, 1994. / Typescript. Includes bibliographical references (leaves 77-80).

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Galactooligosaccharides are produced by the transglycosylation activity of β-galactosidases (β-gal, EC 3.2.1.23) when utilising lactose as a substrate. They have emerged as important constituents used in the food and pharmaceutical industries owing to their prebiotic properties. Although transglycosylation was discovered in 1951 (Wallenfels 1951), and a number of β-gals have had their transglycosylation activity characterised, the activities of these enzymes are not optimal for industrial use. Their tendency to favour the hydrolytic reaction over the transglycosylation reaction, coupled with the production of shorter chain oligosaccharides has driven scientists to investigate altering protein structure both to increase chain lengths and the amount of oligosaccharide produced at lower substrate concentrations. In an attempt to alter the amount of oligosaccharide produced by a metagenomically derived β-gal belonging to the glycosyl hydrolase 2 family, random and site-directed mutagenesis were used. A randomly mutagenised library was screened on SOB agar plates containing 5% (w/v) lactose which should select for clones that synthesise oligosaccharides at relatively low concentrations. No such activity was detected. Site-directed mutagenesis was also utilised to alter protein structure. It was confirmed that the β-gal utilised in this study belonged to the glycosyl hydrolase 2 family through mutation of the predicted catalytic acid/base glutamic acid to a non-catalytic residue, thus removing activity. Another mutation was utilised to investigate if it was possible to increase the degree of polymerisation of oligosaccharides produced by the β-gal. This mutation was successful in increasing the degree of polymerisation. Biochemical characterisation of the β-gal revealed that it exhibited optimal activity at pH 8.0, with a temperature optimum of 30°C. The β-gal exhibited a Km and Vmax of 54.23 mM and 2.26 μmol/minute-1/mg protein-1 respectively, similar to kinetic parameters that have been determined for a number of previously characterised enzymes. / AFRIKAANSE OPSOMMING: Galaktooligosakkariede word geproduseer deur die transglikosileering aktiwiteit van β-galaktosidase (β-gal, EG 3.2.1.23) wanneer hulle laktose as 'n substraat gebruik. Hierdie oligosakkariede het na vore gekom as 'n belangrike bestandeel vir gebruik in die voedsel en farmaseutiese bedryf as gevolg van hulle prebiotiese eienskappe. Alhoewel transglycosylation al in 1951 ontdek is (Wallenfels 1951) en 'n aantal β-gals se transglycosylation aktiwiteit gekenmerk is, is hierdie ensieme nie ideaal vir industriële toepassings nie. Die geneigdheid om die hidrolitiese reaksie oor die transglycosylation reaksie bevoordeel, tesame met die produksie van korter oligosakkariede het wetenskaplikes ondersoek genoop om die proteïenstruktuur te verander om ketting-lengte en die kwantiteit van oligosakkaried geproduseer teen laer substraat konsentrasies te verhoog. In 'n poging om die opbrengs van die oligosakkaried wat deur 'n metagenomiese β-gal wat aan die glycosyl hidrolase 2 familie behoort te verander, is lukraak en terrein gerigte-mutagenese gebruik. Die mutagenese biblioteek is op SOB agarplate met 5% (w/v) lactose gekeur, om klone wat die fenotipe wat verband hou met die produksie oligosakkaried teen relatiewe lae konsentrasies te selekteer. Geen aktiwiteit is opgemerk nie. Terrein gerigte-mutagenese is ook gebruik om die proteïenstruktuur te verander. Deur ‘n bioinformatiese voorspelling, is dit bevestig dat die β-gal wat in hiedie studie gebruik word tot die glycosyl hidrolase 2 familie behoort. Dit is gedoen deur mutasie van die voorspelde katalitiese suur/basis glutamiensuur na 'n nie-katalitiese oorskot, dus die verwydering van aktiwiteit. Nog ‘n mutasie is gebruik om te ondersoek of dit moontlik was om die ketting-lengte van die oligosakkaried wat deur die β-gal geproduseer is te verhoog. Die mutasie was suksesvol in die verhoging van die oligosakkaried wat geproduseer was. Biochemiese karakterisering van die β-gal het getoon dat hierdie β-gal optimale aktiwiteit het by pH 8.0, met 'n optimum temperatuur van 30°C. Die β-gal het 'n Km en Vmax van 54.23 mM en 2.26 μmol/minute-1/mg proteïen-1 onderskeidelik, soortgelyk aan kinetiese parameters wat bepaal word vir ensieme wat voorheen gekenmerk is.

γ-aminobutyric acid is the major inhibitory neurotransmitter in the adult mammalian central nervous system (CNS) and may also play a neurotrophic role during CNS development. Diversification of GABA_A receptor mediated responses are in part a result ofvariation in subunit composition in the receptor complex. This variation arises both from the number of different subtypes of GABA_A receptor subunits (α1-6, β1-4, γ1-3, δ1, ρ1-3, ε, ρ), as well as from post-transcriptional processes such as RNA splicing. In this thesis, I have investigated the developmental onset of GABA_A receptor gene expression and the distribution and temporal expression of GABA_A receptor subunit mRNAs and 12 splice variants within the developing and adult murine CNS. Preliminary studies using S 1 nuclease protection analysis demonstrated that α1, β3 and γ2 were the predominant subtypes of GABA_A receptor subunits expressed at embryonic day 14 and in the adult murine CNS. In situ hybridisation analysis demonstrated overlapping but distinct spatial and temporal patterns of GABA_A subunit mRNA expression during postnatal development and in the adult murine CNS. Analysis of γ2 mRNA splice variants demonstrated that the γ2S transcript is the predominant γ2 mRNA expressed during latter stages of embryo genesis, while the γ2L transcript is the predominant γ2 isoform present inthe adult CNS. Since there is a 29 to 47 percent amino acid identity among the various GABA_A receptor subunits, I have also demonstrated through site-directed mutagenesis studies, that changes in a conserved amino acid in the cysteine loop of the bovine a 1 GABA_A receptor subunit resulted in a loss of agonist and antagonist binding (DI49N), while a change in a conserved amino acid in the M1 transmembrane domain of the bovine α1 GABA_A receptor subunit resulted in loss of agonist binding and reduction in the B_max and K_d for antagonist binding (P243A). 'These results are in contrast to the effect of identical mutations in the bovine β1 subunit and suggest that if the pentameric GABA_A receptor assembly is composed of (α1)2(β1)1(γ2)2, then changes in highly conserved amino acids in the α1 receptor subunit would have a greater distortion on the structure of the receptor complex.