Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 96-113).

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Thèse de doctorat : Biochimie : Lille 1 : 2000. / Textes en français et en anglais (publications). Résumé en français et en anglais. Bibliogr. p. 266-290. Notes bibliogr.

The effect of the time of application of Gibberellic Acid (GA3) and Lipo-Chitin Oligosaccharides (LCOs) on annual production of globe artichoke (Cynara scolymus L.) cultivars 'Imperial Star' and 'Green Globe' was studied in 2000 and 2001. In order for flowering to occur plants must undergo a period of vernalization. In 2000, plants received 54 chilling (vernalizing) hours, an amount sufficient to induce flowering in 100% of the Imperial star and 25% of the Green Globe control plants. Applications of 25ppm GA3 at the 6 and 10-leaf stage reduced the time to flowering by 11 days, increased uniformity of flower bud production, and also increased yield of Imperial Star. GA3 had no significant effect on Green Globe plants. LCO fraction C (an identified and collected nod factor peak in retention time of 32.56 minutes) had minimal effect on growth and development for both cultivars in 2000. In 2001 plants received no vernalizing temperatures and in addition were exposed to 89 hours of temperatures greater than 32°C which could devernalize the plants. (Abstract shortened by UMI.)

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Extremozymes are enzymes produced by microorganisms that live in extreme habitats. Due to their higher stability, extremozymes is attracting interest as biocatalysts in various industrial processes. In this context, carbohydrate-active extremozymes can be used in various processes relevant to the paper, food and feed industry. In this thesis, the crystal structure, biochemical characterization and the capacity to synthesize prebiotic galacto-oligosaccharides (GOS) were investigated for a β-glucosidase (HoBGLA) from the halothermophilic bacterium Halothermothrix orenii. The wild-type enzyme displays favorable characteristics for lactose hydrolysis and produces a range of prebiotic GOS, of which β-D-Galp-(1→6)-D-Lac and β-D-Galp-(1→3)-D-Lac are the major products (Paper I). To further improve GOS synthesis by HoBGLA, rational enzyme engineering was performed (Paper II). Six enzyme variants were generated by replacing strategically positioned active-site residues. Two HoBGLA variants were identified as potentially interesting, F417S and F417Y. The former appears to synthesize one particular GOS product in higher yield, whereas the latter produces a higher yield of total GOS. In Paper III, the high-resolution crystal structure and biochemical characterization of a hemicellulase (HoAraf43) from  H. orenii is presented. HoAraf43 folds as a five-bladed β-propeller and displays α-Larabinofuranosidase activity. The melting temperature of  HoAraf43 increases significantly in the presence of high salt and divalent cations, which is consistent with H. orenii being a halophile. Furthermore, the crystal structures of a thermostable tetrameric pyranose 2-oxidase from Phanerochaete chrysosporium (PcP2O) were determined to investigate the structural determinants of thermostability (Paper IV). PcP2O has an increased number of salt links between subunits, which may provide a mechanism for increased stability. The structures also imply that the N-terminal region acts as an intramolecular chaperone during homotetramer assembly. / <p>QC 20150429</p>

This thesis is concerned with structural aspects of the recognition and effector functions of antibody molecules. The recognition process is investigated in the dinitrophenyl (DNP) binding mouse IgA produced by the myeloma MOPC 315. The studies on effector functions utilize a DNP binding mouse hybridoma IgG2a to examine the role of N-glycosylation in IgG. The combining site of protein 315. The involvement of tyrosyl residues in the combining site of protein 315 was examined by preparing specifically nitrated NO₂-Tyr-33_H and NO₂-Tyr-34_L derivatives of the Fv fragment of this protein. The ionizations of tnese derivatives were studied in the presence and absence of various DNP-ligands. Perturbations to the nitrotyrosine ionizations were found to be caused by the side chains of certain of these ligands, allowing an indication of the distance of these tyrosines from the bound hapten. On examination of the compatibility of these data with the model of the combining site of protein 315 proposed by Dower <en>et al. (1977) (Biochem. J. 165, 207-225) it was found that while the location of Tyr-33_H is consistent with this model, the position of Tyr-34_L is not. A remodelled combining site using the modified ring-current treatment of Perkins and Dwek (1980) (Biochemistry 19, 245-258) is presented. This allows a better rationalization of the nitration data and of previous experimental observations on protein 315. The role of the conserved C 2 domain oligosaccharide of IgG. This was examined by a functional comparison of native IgG with an aglycosylated IgG preparation. Aglycosylation was acheived by cell culture of the hybridoma cells in the presence of the glycosylation inhibitor tunicamycin. The conditions for preparation and purification of this aglycosyl IgG are described. Aglycosylated IgG is found to be correctly assembled as an H₂L₂ unit. It retains the antigen binding and Staphylococcal protein A binding abilities of the native glycosylated molecule. Using an assay system designed specifically to overcome certain problems in comparing Clq binding to different preparations of IgG it was found that the aglycosylated preparation showed only slightly reduced affinity for Clq. In addition the aglycosylated IgG is able to activate bound Cl. The above results are consistent with the structure of the Fc region being only minimally altered in the absence of oligosaccharide. The structural integrity of the aglycosylated molecule may be compromised however, as its ability to bind to monocyte Fc receptor is significantly reduced. In addition the aglycosylated molecule becomes much more susceptible to proteolytic digestion. A computational model-building analysis of the quaternary structure of Fc allows an explanation of at least some of the effects of aglycosylation in terms of reduced conformational stability of the C_H2 domains.

Thesis (Ph.D.)--Tufts University, 1999. / Adviser: Marc d'Alarcao. Submitted to the Dept. of Chemistry. Includes bibliographical references (leaves 123-128). Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Diss. (sammanfattning) Göteborg : Univ., 2007. / Härtill 5 uppsatser.