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Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / 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. Title from title screen of research.pdf file (viewed on February 14, 2008) Vita. Includes bibliographical references.

Thesis (Ph.D.)--Ohio University, March, 2007. / Includes bibliographical references (leaves 190-200)

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographic references (leaves [144]-153).

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 175-196).

The molecular chaperone process of assisted protein folding, characteristic of members of the Heat Shock Protein 70 kDa (Hsp70) and Heat Shock Protein 40kDa (Hsp40) families, is essential for cytoprotection in stressful cellular conditions. Examples of such conditions are heat shock or invasion by pathogens. The Hsp70/Hsp40 process of assisted protein folding is dependent on ATP (governed by the intrinsic ATPase activity of Hsp70) and the ability of molecular chaperones to recognise and bind non-native protein conformations. Here, we analyse and attempt to characterise the molecular chaperone activity of an inducible, cytoplasmic Hsp70 (TcHsp70) from Trypanosoma cruzi and its interactions with its potential partner Hsp40s, Tcj 1, Tcj2, Tcj3 and Tcj4. A bioinformatic analyses of the primary sequences of the trypanosomal proteins revealed that they all contained the canonical domains that define other members of the Hsp70 and Hsp40 family. Tcj2 and Tcj4 showed deviations from the consensus sequence in their substrate binding regions, which may have implications for their substrate binding specificities. TcHsp70, Tcj 1, Tcj2, Tcj3 and Tcj4 were over-expressed recombinantly as 6xHis-tag fusion proteins in Escherichia coli. His-TcHsp70, Tcjl-His and His-Tcj2 were successfully purified by Nickel-affinity chromatography for functional analyses to assess the molecular chaperone activity of His-TcHsp70 in terms of its ATPase activity and substrate binding ability. The basal ATPase activity of His-TcHsp70 was determined as 40 nmol Pi/min/mg, significantly higher than that reported for other Hsp70s. This basal ATPase activity was stimulated to a maximal level of 60 nmol Pi/min/mg in the presence of His-Tcj2 and a model non-native substrate, reduced carboxymethylated αx-lactalbumin (RCMLA). Using native polyacrylamide gel electrophoresis and Western analysis, His-TcHsp70 was shown to form discrete complexes when in the presence of Tcj 1- His, His-Tcj2 and/or RCMLA. These complexes potentially represent His-TcHsp70 - RCMLA or His-TcHsp70 - Tcj interactions, that may be indicative of chaperone activity. In vivo complementation assays showed that Tcj2, but not Tcj3, was able to overcome the temperature sensitivity of the ydjJ mutant Saccharomyces cerevisiae strain JJ160, suggesting that Tcj2 may be functionally equivalent to the yeast Hsp40 Ydj1.

Thesis (M.Sc.(Chemistry)) -- University of Limpopo, 2016 / Imidazolyl-salicylaldemine Schiff base ligands were prepared by the condensation of different substituted salicylaldehydes with histamine dihydrochloride: 2,4-di-tert-butyl-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol L1; 4-methoxy-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol L2; 2-ethoxy-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl]-phenol L3; 2-methyl-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol L4; 3-methyl-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol L5; 4-methyl-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol L6; 5-methyl-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol L7; 2-tert-butyl-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol L8; 3-methoxy-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol L9; 4-tert-butyl-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol L10. The ligands were characterised by 1H, 13C and 15N NMR, FT-IR, UV-vis spectroscopic methods, mass spectroscopy and elemental analysis where possible. Reactions of L1-L9 with MnCl2 and CuCl2 yielded complexes C1–C18 all in a ratio of (1:1). C1 – C18 here, i.e. C18 2-methyl-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol Cu(II) chloride. The complexes that are paramagnetic were mainly characterised by FT-IR spectroscopy, UV-vis spectroscopy, mass spectroscopy and elemental analysis. Reaction of L9 with ZnCl2 yielded 2-methyl-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol Zn(II) chloride, C19 which is diamagnetic and was characterised by 1H, 13C NMR spectroscopy Mass spectroscopy and Elemental analysis. Condensation of o-phenylenediamine and glyoxylic acid yielded 2-quinoxalinone Q1, reaction of 2-quinoxalinone and benzenesulfonyl chloride yielded 2-benzenesulfonyloxyquinoxaline Q2, and the reaction of 2-benzenesulfonyloxyquinoxaline with ethynyltrimethylsilane yielded 2-ethynyltrimethylsilanequinoxaline Q3. Quinoxaline and its preceding starting compounds were characterised by 1H, 13C NMR spectroscopy. Attempts to cross couple Schiff base complex C19 and Q3 via Sonogashira cross coupling mechanism method was not successful after two attempts from following two different reaction routes and conditions. The trans-metalation route yielded quinoxaline derivative QA in good yield after the reaction of Q3 with ZnCl2 and, C19 in the presence of Et2NH which were characterised by NMR (1H, 13C and HMBC), Mass spectroscopy (HRMS) and Elemental analysis. iv These reactions showed hydroamination instead of coordination in yield of (90%) using ZnCl2 as catalyst and 60% using C19 as catalyst. Biological activity studies were done by quantitative antibacterial activity by assay of minimum inhibition concentration (MIC). Bacterial cells used as pathogenic microorganisms were gram negative: Escherichia coli and Pseudomonas aeruginosa, gram positive: Staphylococcus aureus and Enterococcus faecalis. Compound used for testing : L9, C19, C18, C9, Q3 and QA. All compounds were found to be active against bacterial cells of E. coli and E. faecalis with a minimum inhibition concentration of 0.004 mg/ml average and total activity of 500 mg/ml average. For all compounds used for testing bacterial activity against cells of P. aeruginosa and S. aureus, the lowest concentration was 0.063 mg/ml average and total activity of 266 mg/ml average for C18. P. aeruginosa and S. aureus were found to be less active compared to bioactive standards used for E. coli and E. faecalis.

Thesis (M.Sc. (Chemistry)) -- University of Limpopo, 2016 / Imidazolyl-salicylaldemine Schiff base ligands were prepared by the condensation of different substituted salicylaldehydes with histamine dihydrochloride: 2,4-di-tert-butyl-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol L1; 4-methoxy-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol L2; 2-ethoxy-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl]-phenol L3; 2-methyl-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol L4; 3-methyl-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol L5; 4-methyl-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol L6; 5-methyl-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol L7; 2-tert-butyl-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol L8; 3-methoxy-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol L9; 4-tert-butyl-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol L10. The ligands were characterised by 1H, 13C and 15N NMR, FT-IR, UV-vis spectroscopic methods, mass spectroscopy and elemental analysis where possible. Reactions of L1-L9 with MnCl2 and CuCl2 yielded complexes C1–C18 all in a ratio of (1:1). C1 – C18 here, i.e. C18 2-methyl-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol Cu(II) chloride. The complexes that are paramagnetic were mainly characterised by FT-IR spectroscopy, UV-vis spectroscopy, mass spectroscopy and elemental analysis. Reaction of L9 with ZnCl2 yielded 2-methyl-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol Zn(II) chloride, C19 which is diamagnetic and was characterised by 1H, 13C NMR spectroscopy Mass spectroscopy and Elemental analysis. Condensation of o-phenylenediamine and glyoxylic acid yielded 2-quinoxalinone Q1, reaction of 2-quinoxalinone and benzenesulfonyl chloride yielded 2-benzenesulfonyloxyquinoxaline Q2, and the reaction of 2-benzenesulfonyloxyquinoxaline with ethynyltrimethylsilane yielded 2-ethynyltrimethylsilanequinoxaline Q3. Quinoxaline and its preceding starting compounds were characterised by 1H, 13C NMR spectroscopy. Attempts to cross couple Schiff base complex C19 and Q3 via Sonogashira cross coupling mechanism method was not successful after two attempts from following two different reaction routes and conditions. The trans-metalation route yielded quinoxaline derivative QA in good yield after the reaction of Q3 with ZnCl2 and, C19 in the presence of Et2NH which were characterised by NMR (1H, 13C and HMBC), Mass spectroscopy (HRMS) and Elemental analysis. iv These reactions showed hydroamination instead of coordination in yield of (90%) using ZnCl2 as catalyst and 60% using C19 as catalyst. Biological activity studies were done by quantitative antibacterial activity by assay of minimum inhibition concentration (MIC). Bacterial cells used as pathogenic microorganisms were gram negative: Escherichia coli and Pseudomonas aeruginosa, gram positive: Staphylococcus aureus and Enterococcus faecalis. Compound used for testing : L9, C19, C18, C9, Q3 and QA. All compounds were found to be active against bacterial cells of E. coli and E. faecalis with a minimum inhibition concentration of 0.004 mg/ml average and total activity of 500 mg/ml average. For all compounds used for testing bacterial activity against cells of P. aeruginosa and S. aureus, the lowest concentration was 0.063 mg/ml average and total activity of 266 mg/ml average for C18. P. aeruginosa and S. aureus were found to be less active compared to bioactive standards used for E. coli and E. faecalis.

Investigation on the synthesis of the C-13 side chain of taxol was carried out in order to prepare modified taxol derivatives by coupling of the side chain acid chloride to a suitably protected baccatin III. The side chain was prepared by the Darzens condensation. Acylation of baccatin III was performed with simple acylating agents and extensive studies of the ¹H NMR and ¹³C NMR spectra of various acylbaccatins III were carried out aided by homonuclear and heteronuclear COSY experiments. This work led to the unambiguous assignment of the ¹H NMR and ¹³C NMR spectra of these compounds. Coupling of more bulky side chains to 7-(2,2,2-trichloroethyloxycarbonyl) baccatin III was difficult and yields were poor. Conventional methods, using triethylamine or pyridine with 4-dimethylaminopyridine in the coupling reaction of 3- phenylpropanoyl chloride and 7-(2,2,2-trichloroethyloxycarbonyl) baccatin III led to the desired coupled product in low yield together with two coupled compounds possessing more than one phenylpropanoyl group on the C-13 side chain. When the coupling reaction was performed in the presence of silver cyanide in refluxing toluene, only 13-(3-phenylpropanoyl) baccatin III was obtained. However, these two methods were not successful in the coupling reaction of 2-acetyl-3- phenyllactyl chlorlde with 7-(2,2,2-trichloroethyloxycarbonyl) baccatin III. Preliminary studies on the cleavage of the N-acyl group at the C-3' position of taxol and cephalomannine were performed. Taxol reacted with zinc bromide in chloroform-methanol solution to produce 10- deacetyl-7-epitaxol and 10-deacetyltaxol. No cleavage of the N-acyl group was detected in this case and in other reactions in which taxol was treated with various selective reagents. Other attempts involved the conversion of cephalomannine to its ozonolysis products with a pyruvyl group at the 3’-NH group. A method of cleavage of the N-pyruvyl group has not yet been found, however. / Ph. D. / incomplete_metadata

No description available.