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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Ring a modification of miltirone: synthesis of nitrogen containing compounds.

January 1990 (has links)
by Yee-kwan Lau. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1990. / Bibliography: leaves 65-67. / Chapter I. --- Acknowledgements --- p.1 / Chapter II. --- List of Nomenclature --- p.2 / Chapter III. --- Abstract --- p.10 / Chapter IV. --- Introduction --- p.11 / Chapter V. --- Results and Discussion: / Chapter i. --- Synthesis of ortho-quinonoid compounds related to miltirone ( / ) --- p.17 / Chapter ii. --- Pharmacological profile of synthetic compounds --- p.37 / Chapter VI. --- Conclusion --- p.33 / Chapter VII. --- Experimental Section --- p.39 / Chapter VIII. --- References and Notes --- p.55 / Chapter IX. --- Spectra --- p.68
2

New approaches to nitrogen ligands bearing electron withdrawing groups and their role in coordination chemistry

Shukla, Piyush, 1977- 27 July 2011 (has links)
Not available / text
3

Engineering homoaromatic substrate specificity into aliphatic-specific Geobacillus pallidus RAPc8 nitrile hydratase

Parikshant Kowlessur January 2007 (has links)
<p>Geobacillus pallidus RAPc8 is a thermophilic nitrile-degrading isolate, obtained from thermal sediment samples of a New Zealand hot spring. The G. pallidus RAPc8 NHase gene has been cloned and expressed in E. coli. The recombinant NHase exhibits nitrile-degrading activity at 50 &deg / C, capable of degrading branched, linear and cyclic heteroaromatic nitrile substrates. However, no activity was found on homoaromatic nitrile substrates such as benzonitrile. In the present study, high levels of activity on benzonitrile were detected with a double mutant &beta / F52G&beta / F55L. Kinetic analysis on the mutant enzyme showed an 8-fold decrease in KM with benzonitrile (0.3mM) compared to acrylonitrile (2.6mM). Specificity constants (kcat/KM) of 5900 and 450 s-1.mM-1 were obtained for the double mutant on benzonitrile and acrylonitrile respectively. The amino acid residues lining the substrate channel were identified and the geometric dimensions measured. Cavity calculations revealed a 29% increase in volume and a 13% increase in inner surface area for the substrate channel of the double mutant when compared to the wild type. Surface representation of the wild type structure revealed two extended, curved channels, which are accessible to the bulk solvent from two locations in the heterodimer. The removal of the &beta / F52 may have contributed to the presence of a single channel with two opposing openings across the dimers with no internal blockage. Normal Mode Analysis calculations also indicate a higher intrinsic flexibility of the mutant relative tothe wild type enzyme. The increased flexibility within the mutant NHase could have introduced a functionally relevant aromatic substrate recognition conformation</p>
4

Screening for subtate tolerant Geobacillus pallidus RAPc8 nitrile hydratase

Mketsu, Moses Clive Masisange January 2009 (has links)
<p>In this study G. pallidus RAPc8 NHase mutants were screened for reduced substrate inhibition compared to the wild type enzyme. Wild type and mutant enzymes were expressed and purified using hydrophobic interaction chromatography. Amidase coupled enzyme stop assays were conducted using 3-cyanopyridine as a substrate, whereas continuous enzyme kinetics were conducted using acrylonitrile as a substrate.</p>
5

Screening for subtate tolerant Geobacillus pallidus RAPc8 nitrile hydratase

Mketsu, Moses Clive Masisange January 2009 (has links)
<p>In this study G. pallidus RAPc8 NHase mutants were screened for reduced substrate inhibition compared to the wild type enzyme. Wild type and mutant enzymes were expressed and purified using hydrophobic interaction chromatography. Amidase coupled enzyme stop assays were conducted using 3-cyanopyridine as a substrate, whereas continuous enzyme kinetics were conducted using acrylonitrile as a substrate.</p>
6

Engineering homoaromatic substrate specificity into aliphatic-specific Geobacillus pallidus RAPc8 nitrile hydratase

Parikshant Kowlessur January 2007 (has links)
<p>Geobacillus pallidus RAPc8 is a thermophilic nitrile-degrading isolate, obtained from thermal sediment samples of a New Zealand hot spring. The G. pallidus RAPc8 NHase gene has been cloned and expressed in E. coli. The recombinant NHase exhibits nitrile-degrading activity at 50 &deg / C, capable of degrading branched, linear and cyclic heteroaromatic nitrile substrates. However, no activity was found on homoaromatic nitrile substrates such as benzonitrile. In the present study, high levels of activity on benzonitrile were detected with a double mutant &beta / F52G&beta / F55L. Kinetic analysis on the mutant enzyme showed an 8-fold decrease in KM with benzonitrile (0.3mM) compared to acrylonitrile (2.6mM). Specificity constants (kcat/KM) of 5900 and 450 s-1.mM-1 were obtained for the double mutant on benzonitrile and acrylonitrile respectively. The amino acid residues lining the substrate channel were identified and the geometric dimensions measured. Cavity calculations revealed a 29% increase in volume and a 13% increase in inner surface area for the substrate channel of the double mutant when compared to the wild type. Surface representation of the wild type structure revealed two extended, curved channels, which are accessible to the bulk solvent from two locations in the heterodimer. The removal of the &beta / F52 may have contributed to the presence of a single channel with two opposing openings across the dimers with no internal blockage. Normal Mode Analysis calculations also indicate a higher intrinsic flexibility of the mutant relative tothe wild type enzyme. The increased flexibility within the mutant NHase could have introduced a functionally relevant aromatic substrate recognition conformation</p>
7

Engineering homoaromatic substrate specificity into aliphatic-specific Geobacillus pallidus RAPc8 nitrile hydratase

Kowlessur, Parikshant January 2007 (has links)
Magister Scientiae - MSc / Geobacillus pallidus RAPc8 is a thermophilic nitrile-degrading isolate, obtained from thermal sediment samples of a New Zealand hot spring. The G. pallidus RAPc8 NHase gene has been cloned and expressed in E. coli. The recombinant NHase exhibits nitrile-degrading activity at 50 °C, capable of degrading branched, linear and cyclic heteroaromatic nitrile substrates. However, no activity was found on homoaromatic nitrile substrates such as benzonitrile. In the present study, high levels of activity on benzonitrile were detected with a double mutant βF52GβF55L. Kinetic analysis on the mutant enzyme showed an 8-fold decrease in KM with benzonitrile (0.3mM) compared to acrylonitrile (2.6mM). Specificity constants (kcat/KM) of 5900 and 450 s-1.mM-1 were obtained for the double mutant on benzonitrile and acrylonitrile respectively. The amino acid residues lining the substrate channel were identified and the geometric dimensions measured. Cavity calculations revealed a 29% increase in volume and a 13% increase in inner surface area for the substrate channel of the double mutant when compared to the wild type. Surface representation of the wild type structure revealed two extended, curved channels, which are accessible to the bulk solvent from two locations in the heterodimer. The removal of the βF52may have contributed to the presence of a single channel with two opposing openings across the dimers with no internal blockage. Normal Mode Analysis calculations also indicate a higher intrinsic flexibility of the mutant relative tothe wild type enzyme. The increased flexibility within the mutant NHase could have introduced a functionally relevant aromatic substrate recognition conformation. / South Africa
8

Screening for subtate tolerant Geobacillus pallidus RAPc8 nitrile hydratase

Mketsu, Moses Clive Masisange January 2009 (has links)
Magister Scientiae - MSc / In this study G. pallidus RAPc8 NHase mutants were screened for reduced substrate inhibition compared to the wild type enzyme. Wild type and mutant enzymes were expressed and purified using hydrophobic interaction chromatography. Amidase coupled enzyme stop assays were conducted using 3-cyanopyridine as a substrate, whereas continuous enzyme kinetics were conducted using acrylonitrile as a substrate. / South Africa
9

A chromatograhic investigation of the alcohol-soluble nitrogenous constituents of Verticillium albo-atrum R. and B. isolates

Pepin, Herbert Spencer January 1956 (has links)
Verticillium albo-atrum R. and B. isolates were separated into four strain groups based on morphological type. All isolates were tested for pathogenicity toward tomato, and an attempt was made to relate pathogenicity to morphological type. Since structural and functional differences in plants and animals are believed to be invariably associated with chemical differences, a survey of the nitrogenous constituents of the isolates was made in an attempt to relate any differences to morphological or pathologic strains. The alcohol-soluble extract from the mycelium of each isolate was investigated chromatographically for amino acids, amines, amides and peptides. The amino acids found were the same for all isolates. These were aspartic acid, glutamic acid, lysine, histidine, isoleucine, serine, valine, proline, methionine, ∝ alanine, tyrosine, threonine, glycine and one unidentified neutral compound, A. No amines, amides or peptides were detected. The amino acids, amines, amides and peptides of the ∝, β and Ȣ strains of Colletotricum lindemuthianum (Sacc. and Magn. ) Bri. and Gav. were isolated and identified using the techniques of paper chromatography for the purpose of comparison with Verticillium albo-atrum. The three Colletotricum strains contained the same amino acids as the Verticillium isolates with the exception of unknown A which was replaced by another unknown, B, common to all three Colletotricum strains indicating a definite species difference. Strain differences apparently do not occur in these two organisms in the groups of compounds studied. The effect of aeration, age of mycelium, pH of medium and carbon source on the qualitative amino acid content of isolate V3 were studied. These environmental conditions had no qualitative effect on the amino acids of the isolate. The free nucleotides of the acid-soluble extract of six representative isolates were studied using the technique of anion-exchange chromatography. Nucleotides isolated from all isolates and tentatively identified were guanosine monophosphate, guanosine diphosphate, guanosine triphosphate, cyt-idine diphosphate, uridine monophosphate, uridine diphosphate, uridine triphosphate and adenosine diphosphate. No other nucleotides were isolated. The above results indicated that if chemical dif-ferences do exist between strains, as postulated, they do not occur, In these two organisms, among the nitrogenous compounds studied, but must occur In some other class of compounds not studied in this investigation. / Science, Faculty of / Botany, Department of / Zoology, Department of / Graduate
10

The chemistry of azasulfonium salts /

Gruetzmacher, Gordon January 1974 (has links)
No description available.

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