No description available.

Cyanide is a well known toxicant that arises in the environment from both biological and industrial sources. Bacteria have evolved novel coping mechanisms for cyanide and function as principal agents in the biosphere for cyanide recycling. Some bacteria exhibit the unusual ability of growing on cyanide as the sole nitrogen source. One such organism is Pseudomonas fluorescens NCIMB 11764 (Pf11764) which employs a novel oxidative mechanism for detoxifying and assimilating cyanide. A unique complex of enzymes referred to as cyanide oxygenase (CNO) is responsible for this ability converting cyanide to ammonia which is then assimilated. Because one component of the four member CNO complex was previously shown to act on cyanide independent of the other members, its characterization was sought as a means of gaining a better understanding of the overall catalytic mechanism of the complex. Preliminary studies suggested that the enzyme belonged to a subset of nitrilase enzymes known as cyanide dihydratases (CynD), however, a cynD-like gene in Pf11764 could not be detected by PCR. Instead, a separate nitrilase (Nit) linked to cyanide metabolism was detected. The corresponding nit gene was shown to be one of a conserved set of nit genes traced to a unique cluster in bacteria known as Nit1C. To determine whether the previously described CynD enzyme was instead Nit, efforts were undertaken to isolate the enzyme. This was pursued by cloning and expressing the recombinant enzyme and by attempting to isolate the native enzyme. This thesis is concerned with the latter activity and describes the purification of a Nit-like cyanide-degrading nitrilase (NitCC) from Pf11764 to ~95% homogeneity. Purification was greatly facilitated by the discovery that fumaronitrile, as opposed to cyanide, was the preferred substrate for the enzyme (20 versus 1 U/mg protein, respectively). While cyanide was less effective as a substrate, the specificity for cyanide far outweighed that (10,000 fold) of the recombinant enzyme (NitPG) implying that the native NitCC protein purified in this work is different from that of the cloned recombinant. Further evidence of this was provided by molecular studies indicating that the two proteins differ in mass (34.5 and 38 kDa, respectively) and amino acid sequence. In summary, two different Nit enzymes are encoded by Pf11764. While the two share greater than 50% amino acid sequence identity, the results suggest that the native NitCC enzyme purified in this work functions better as a cyanide-degrading nitrilase and is one of four enzyme components comprising CNO required for Pf11764 cyanide assimilation.

The problem of the quadrupole interaction occurring in a vibrating-rotating C₃v symmetric top molecule has been studied in detail. The quadrupole interaction has been treated as another perturbation term to a general frequency expression accounting for the vibrating-rotating interaction of the molecule so that a complete frequency formula is obtained for both interactions, and from which hyperfine spectral components are predicted and measured. The hyperfine transitions in the ground, and v₈=1 and v₈=2 excited vibrational states of the ¹³C isotopes of methyl cyanide have been investigated in the frequency range 17-72 GHz, primarily in the low J transitions (0≤J≤3). The study of the ground state of isotope i3CH3i3CN, and the v₈=1, v₈=2 excited vibrational states for all the isotopes have been conducted here for the first time. A substantial perturbation has been discovered and discussed at the ΔJ=3→4 transitions within the Kl=1 sets in the v₈=1 mode for isotopes ¹³CH₃CN and CH₃¹³CN. A total of 716 hyperfine transitions have been assigned from measurements, only 7 of which have been measured previously. A total of 84 molecular constants have been reported; 70 of these constants are derived for the first time from microwave data.

Graduation date: 1998

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 161-175). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 161-175). Also available on the Internet.

The local information provided by nuclear magnetic resonance (NMR) makes it an ideal method for the structural investigations of materials lacking extended long-range ordering. This work focuses on investigations of two types of materials possessing very different types of disorder. The first section involves investigations of alkali borate glasses and the application of solid-state NMR techniques to probe short- and medium-range ordering in such glasses. Differences between the various alkali borates over a wide compositional range are probed using one and two-dimensional techniques. The use of double-resonance dipolar recoupling techniques to investigate cesium-boron distances is investigated. The second section probes a series of transition-metal cyanide coordination polymers. The bidentate nature of the cyanide ligand allows for the possibility of forming numerous isomers. Information about the isomer(s) present is gained via the various NMR parameters available, such as the chemical shifts, shift anisotropies and J-couplings. This is then extended to the characterization of paramagnetic transition-metal cyanides, where strong electron-nuclear interactions are shown to significantly increase spin-lattice relaxation rates allowing the acquisition of spectra without the need of typically employed enhancement techniques, yet often yielding spectra of better quality. Variable-temperature experiments allow a measure of the electron-nuclear interaction, which can be related to spatial proximity, and provide “diamagnetic” chemical shifts allowing comparison with other cyanides. J-couplings and chemical shift anisotropies are shown to be applicable in much the same fashion as with diamagnetic systems.

The local information provided by nuclear magnetic resonance (NMR) makes it an ideal method for the structural investigations of materials lacking extended long-range ordering. This work focuses on investigations of two types of materials possessing very different types of disorder. The first section involves investigations of alkali borate glasses and the application of solid-state NMR techniques to probe short- and medium-range ordering in such glasses. Differences between the various alkali borates over a wide compositional range are probed using one and two-dimensional techniques. The use of double-resonance dipolar recoupling techniques to investigate cesium-boron distances is investigated. The second section probes a series of transition-metal cyanide coordination polymers. The bidentate nature of the cyanide ligand allows for the possibility of forming numerous isomers. Information about the isomer(s) present is gained via the various NMR parameters available, such as the chemical shifts, shift anisotropies and J-couplings. This is then extended to the characterization of paramagnetic transition-metal cyanides, where strong electron-nuclear interactions are shown to significantly increase spin-lattice relaxation rates allowing the acquisition of spectra without the need of typically employed enhancement techniques, yet often yielding spectra of better quality. Variable-temperature experiments allow a measure of the electron-nuclear interaction, which can be related to spatial proximity, and provide “diamagnetic” chemical shifts allowing comparison with other cyanides. J-couplings and chemical shift anisotropies are shown to be applicable in much the same fashion as with diamagnetic systems.

No description available.

Thesis (DTech (Chemical Engineering))--Cape Peninsula University of Technology, 2017. / The high rate of industrialisation in most developing countries has brought about challenges of wastewater management especially in the mineral processing industry. Cyanide has been used in base metal extraction processes due to its lixiviant properties thus, its presence in wastewater generated is inevitable. Furthermore, partial and/or the use of unsuitable treatment methods for such wastewater is a potential hazard to both human and the environment. There are several reports on biotechnological treatments of cyanide containing wastewater but few mineral processing industries have adopted this approach. Hence, the thermodynamic study of biodegradation of cyanide containing wastewater was undertaken. The primary aim of this study was to explore the application of bioenergetic models and biological stoichiometry to determine the functionality and thermodynamic requirements for cyanide degrading isolate (Fusarium oxysporum EKT01/02), grown exclusively on Beta vulgaris, for a system designed for the bioremediation of cyanidation wastewater. Chapter 2 reviews some of the applicable thermodynamic parameters such as enthalpy, entropy, heat of combustion, heat capacity, Gibbs energy, including stoichiometry models in relation to their applicability for microbial proliferation in cyanidation wastewater. The chapter places emphasis on the application of agro-industrial waste as a suitable replacement for refined carbon sources for microbial proliferation in bioremediation systems because such systems are environmentally benign. The choice of using agro-industrial waste is due to organic waste properties, i.e. agro-industrial waste is rich in nutrients and is generated in large quantities. Chapter 3 presents the materials and various standardised methods used to address the research gaps identified in chapter 2. For an organism to degrade free cyanide in wastewater, it must be able to survive and perform its primary function in the presence of such a toxicant. Chapter 4 exemplifies both molecular and biochemical characteristics of Fusarium oxysporum EKT01/02 isolated from the rhizosphere of Zea mays contaminated with a cyanide based pesticide. The molecular analyses confirmed the fungal isolate to be Fusarium oxysporum EKT01/02 and the nucleotide sequence of the isolates were deposited with National Centre for Biotechnology Information (NCBI) with accession numbers KU985430 and KU985431. The biochemical analyses revealed a wide substrate utilisation mechanism of the isolate dominated by aminopeptidase including nitrate assimilation capabilities. A preliminary investigation showed free cyanide degradation efficiency of 77.6% (100 mg CN-/L) after 5 days by the isolate. The excess production of extracellular polymeric substance (EPS) was attributed to the isolates’ strive to protect itself from cyanide toxicity.