Nicotine, nornicotine, anabasine and anatabine are four major alkaloids in tobacco, of which nicotine is predominant. In many tobacco cultivars and also in other Nicotiana species, nicotine is converted to nornicotine, which in turn gives rise to potent carcinogen NNN. Nicotine to nornicotine conversion via nicotine-N-demethylation is mediated by the CYP82E family of P450 enzymes. Tobacco (Nicotiana tabacum) converts in senescing leaves, while its diploid progenitors N.tomentosiformis and N.sylvestris convert in both green and senescing and only in senescing leaves, respectively. Previously it has been shown that N.tomentosiformis has different active conversion loci in green and senescing leaves. The green leaf conversion enzyme CYP82E3 is inactivated in tobacco by a single amino acid substitution, while the senescing leaf converter enzyme CYP82E4 is active in tobacco, which gave tobacco a ‘senescing leaf converter’ phenotype. In nonconverter tobacco, CYP82E4 shows transcriptional silencing. The nicotine-N-demethylase gene NsylCYP82E2 involved in nicotine to nornicotine conversion in senesced leaves of N. sylvestris was isolated. NsylCYP82E2 is active in N. sylvestris, but it has become inactivated in tobacco through mutations causing two amino acid substitutions. The conversion factor from N.sylvestris was characterized and a model for the alkaloid profile evolution in the amphidiploid N.tabacum from its diploid progenitors was proposed. Regulation of conversion phenomenon was tested under different spatio-temporal conditions and various stresses. The promoter region for NtabCYP82E4 was isolated and promoter-reporter construct was used to determine that NtabCYP82E4 is specifically induced only during senescence. This pattern correlates with the nornicotine accumulation as measured by alkaloid profiling. Thus the regulatory regions of NtabCYP82E4 represent a senescence specific promoter. In another project functional characterization of tobacco EIN2 (NtabEIN2) was undertaken. EIN2 from tobacco and N.sylvestris were cloned, their genomic structure was deduced and NtabEIN2 was silenced using RNAi approach. Silenced plants showed significant delay in petal senescence and abscission; as well as anther dehiscence, pod maturation, pod size, seed yield and defense against tobacco hornworm. Mechanism of delayed petal senescence phenotype, including possible cross-talk with Auxin Response Factor 2 and potential involvement of tasiRNA3 were also investigated.

Currently, cancer is the second leading cause of death in the United States. Conventional cancer treatment includes chemotherapy, radiation, and surgical resection, but unfortunately, all of these methods have significant drawbacks. Hyperthermia, the heating of cancerous tissues to between 41 and 45°C, has been shown to improve the efficacy of cancer therapy when used in conjunction with irradiation and/or chemotherapy. In this work, a novel method for remotely administering heat is presented. This method involves heating of tumor tissue using hydrogel nanocomposites containing magnetic nanoparticles which can be remotely heated upon exposure to an external alternating magnetic field (AMF). The iron oxide nanoparticles contained in the hydrogel nanocomposites are able to heat via an AMF due to Brownian and Neel relaxation processes. The administration of hyperthermia via hydrogel nanocomposites allows for local delivery of heat to tumor tissue while also providing a drug depot to deliver chemotherapeutic agents. Both in vivo and in vitro studies have demonstrated that numerous chemotherapeutic agents, when used in conjunction with hyperthermia, show improved efficacy in treating cancer Various magnetic hydrogel nanocomposites were synthesized and characterized for this work including poly(ethylene glycol) (PEG)-based hydrogels, which were studied due to their inherent biocompatibility and “stealth” properties, as well as, poly(β-amino ester) (PBAE)-based hydrogels which have tailorable degradation properties. The PEG hydrogels were investigated for their temperature-responsiveness swelling, mechanical strength, heating capabilities, biocompatibility, ability to kill M059K glioblastoma cells via thermoablation, and the ability to deliver paclitaxel, a chemotherapeutic agent. PBAE hydrogels were also characterized for their degradation and swelling properties, ability to heat upon exposure to an AMF, biocompatibility, mechanical strength, and ability to deliver paclitaxel in a controlled fashion. Additionally, multiple cancer cell lines were exposed to a combination of paclitaxel and heat (at 42.5 °C) in vitro and it was shown that A539 lung carcinoma cells exhibit higher cytotoxicity when exposed to both heat and paclitaxel than either treatment alone. Overall, magnetic hydrogel nanocomposites are promising materials that can be utilized for the multi-modality treatment of cancer through the synergistic delivery of both heat and chemotherapeutic agents.

Protein PEGylation (covalent attachment of poly(ethylene glycol) or PEG to proteins) is an excellent example of a drug delivery system that improves pharmacokinetics and pharmacodynamic properties of therapeutics. However, although PEGylation is clinically proven and attracts both scientific and commercial interest, the technique is associated with many process constraints, in particular related to controlling the number of conjugated PEG chains. A novel, solid-phase PEGylation methodology was attempted to overcome the drawbacks of the commonly used solution-phase methods for preparing PEGylated products. The solid-phase PEGylation methodology involved conjugating protein onto a tethered PEG derivative attached onto a solid matrix, followed by hydrolytic cleavage of the PEG chain from the solid matrix under mild conditions to yield PEGylated protein in free solution. PEGs with molecular weights (MWs) 2000 and 4000 Da were used and a heterobifunctional PEG derivative, α-(β-alanine)-ω-carboxy PEG, with a cleavable β-alanine ester terminal was prepared for surface grafting and protein conjugation. The amine terminal of this PEG derivative was used for grafting PEG onto carboxy functionalized hydrophilic Sephadex and hydrophobic polystyrene derivatives. The free carboxyl terminal was used for protein conjugation via amine coupling. A kinetic study of PEG-surface grafting was performed to understand the influence of a number of parameters on the PEG surface concentration and its conformation, including temperature, reaction time, nature of the matrix, solvent and base, and MW of PEG. PEG grafted matrices were characterized using various surface characterization tools including Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Higher PEG grafting was observed with polystyrene matrices (up to 0.3 mmol/g) than either of the Sephadex derivatives (less than 0.15 mmol/g) using both molecular weights. Detailed surface characterization using XPS studies showed a layer thickness of 11.87 nm was achieved with polystyrene matrices using 4000 Da PEG derivatives after a grafting period of 72 hours at 40°C, indicating the presence of brush conformations for the grafted PEGs. In contrast, mushroom conformations were observed for PEG molecules grafted on both carboxymethyl and carboxypentyl Sephadex derivatives after the same reaction period, with a layer thickness of 2.62 nm and 4.14 nm respectively. Optimized PEG grafting and hydrolysis conditions were developed for solid-phase protein PEGylation using Cytochrome c as a model protein. The presence of PEGylated species were detected by size exclusion chromatography (SEC) from Sephadex derivatives but were absent when using polystyrene matrices. Both Sephadex derivatives gave mainly multi-PEGylated species with poor yields, in place of the expected mono-PEGylated products. A solution-phase PEGylation using the same PEG derivatives was performed successfully and various PEGylated species were identified and characterized using SEC and gel electrophoresis, based on their viscosity radius. An examination of the surface characteristics of the PEG-grafted was carried out by XPS, showing that protein conjugation was greatly influenced by surface force interactions, which depended on the PEG grafting densities and the nature of the solid matrices. Finally, fluorescent images obtained using confocal microscope with fluorescein isothiocyanate labelled Cytochrome c provided supporting evidence regarding the factors that constrained the solid-phase PEGylation process.

This thesis describes the development of new catalytic systems based upon iron complexes and their reactivity toward ethylene. First, we focused our interest on the synthesis of iron(III) precursors chelated by monoanionic ligand. Those complexes were obtained either by reaction of the monoanionic ligand with FeCl3 or through oxidation of the iron(II) complex. The second reaction led to binuclear complexes. Then, another aim of the thesis was to design new well-defined cocatalysts for the activation of iron complexes. The study of the reaction between an alcohol and the trimethylaluminum allowed us to reach this aim. Aluminum complexes adopted either a binuclear framework or a trinuclear one, depending on the nature of alcohol reagent. Besides this work, new iron(II) and nickel(II) complexes chelated by imino-imidazole ligands bearing a pendant donor function L were synthesized. All complexes have been evaluated for the oligomerization of ethylene in the presence of EtAlCl2 or MAO as cocatalyst. Only nickel complexes were active toward ethylene transformation.

Safripol is a South African polymer company producing mainly high density polyethylene and polypropylene for the South African market. Safripol used to be part of a global chemical company Dow Chemicals. Dow Chemical's divested in South Africa in 2006 and Safripol lost all the advantages of being part of a global corporate enterprise. The company is faced with a unique situation in that it is receiving monomer from Sasol, which is also its main competitor in the polymer market. The price of monomer and its low availability is putting pressure on Safripol's product margins, with a negative effect on the company's sustainability. The above was also defined as the research problem that threatens to undermine the company's competitive edge in the polymer market. It was clear from this research study that monomer and specifically propylene was the biggest burning point for Safripol regarding the price and availability thereof. Research into the South African polymer market has shown that Safripol will lose significant market share if the company is not showing additional growth in the market. The research problem is investigated through interviews, monomer availability investigations, plant capacity increasing and potential technology partner's discussions. A specific scenario planning process was also followed to help Safripol identify potential present and future scenarios that the company can investigate. The research problem was addressed by developing a strategy for Safripol to address the research objectives. Recommendations were done regarding the following: 1) Recommendations for additional propylene supply. 2) Recommendations to increase the polypropylene plant capacity. 3) Recommendations with regards to technology partners. 4) Recommendations regarding the scenario planning process. / Thesis (M.Ing. (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2011. (Mag eers in 2014 gepubliseer word)

Safripol is a South African polymer company producing mainly high density polyethylene and polypropylene for the South African market. Safripol used to be part of a global chemical company Dow Chemicals. Dow Chemical's divested in South Africa in 2006 and Safripol lost all the advantages of being part of a global corporate enterprise. The company is faced with a unique situation in that it is receiving monomer from Sasol, which is also its main competitor in the polymer market. The price of monomer and its low availability is putting pressure on Safripol's product margins, with a negative effect on the company's sustainability. The above was also defined as the research problem that threatens to undermine the company's competitive edge in the polymer market. It was clear from this research study that monomer and specifically propylene was the biggest burning point for Safripol regarding the price and availability thereof. Research into the South African polymer market has shown that Safripol will lose significant market share if the company is not showing additional growth in the market. The research problem is investigated through interviews, monomer availability investigations, plant capacity increasing and potential technology partner's discussions. A specific scenario planning process was also followed to help Safripol identify potential present and future scenarios that the company can investigate. The research problem was addressed by developing a strategy for Safripol to address the research objectives. Recommendations were done regarding the following: 1) Recommendations for additional propylene supply. 2) Recommendations to increase the polypropylene plant capacity. 3) Recommendations with regards to technology partners. 4) Recommendations regarding the scenario planning process. / Thesis (M.Ing. (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2011. (Mag eers in 2014 gepubliseer word)

The aim of this thesis is the study of protein resistant oligo(ethylene glycol) (OEG) self-assembled monolayers (SAMs) using in situ techniques, such as neutron reflectivity (NR), polarisation modulation infrared spectroscopy (PMIR) and small-angle x-ray scattering (SAXS). In order to elucidate the mechanisms that lead to the nonfouling properties of these SAMs, the SAM-water, protein-protein and protein-SAM interactions have been studied separately. NR measurements, focused on the solid-liquid interface between OEG SAMs and water, show clear evidence of an extended layer with reduced density water. The reduction in density is up to 10% compared to the bulk value, and extends up to 5 nm into the bulk. The effective area (density reduction x length) of this reduced density water layer did not significantly change when the temperature was reduced to 5°C. In a complementary study, the interaction of water with protein-resistant HS(CHV₂)₁₁(OCH₂CH₂)₃OMe monolayers was examined using in and ex situ PMIR. In particular, shifts in the position of the characteristic C-O-C stretching vibration were observed after the monolayers had been exposed to water. The shift in frequency increased when the SAM was observed in direct contact with a thin layer of water. It was found that the magnitude of the shift also depended on the surface coverage of the SAM. These results suggest a rather strong interaction of oligo(ethylene glycol) SAMs with water and indicate the penetration of water into the upper region of the monolayer. These findings indicate the presence of a tightly bound water layer at the SAM-water interface. Further NR studies of the interface between OEG SAMs and a highly concentrated protein solution revealed an oscillating protein density profile. A protein depleted region of about 4-5 nm close to the SAM was followed by a more densely populated region of 5-6 nm. These oscillations were then rapidly damped out until the bulk value was reached. The influence of temperature and salt concentration on the protein density profile was small, indicating a rather minor contribution of electrostatic interactions to the protein repulsive force. SAXS measurements of OEG coated gold colloids mixed with proteins in solution did also not show any pronounced salt concentration dependence of the colloid-protein interaction. The strong association of water with the SAM and the layer of tightly bound water, together with the lack of electrostatic repulsion, suggest that the adsorption of proteins is energetically hindered by the presence of a strongly bound hydration layer.

No description available.

The feasibility of highly dispersed gold nanocatalyst supported on yttria-stabilized zirconia (YSZ) for the model reactions of C2H4 and CO oxidation is demonstrated for the first time. Gold nanoparticles are synthesized on YSZ powder by chemical reduction of the precursor salt in the mixture of ethanol, water and polyvinylpyrrolidone (PVP). Resulting metal loading of the catalysts are 1 wt.% with average particle sizes ranging from 6 to 9 nm. Results of CO and C2H4 oxidation display catalytic activity at 65 0C and 25 0C for CO and C2H4 oxidation, respectively. The catalytic properties of the catalysts are different due to their average particle size. Electrochemical Promotion of Catalysis (EPOC) of C2H4 oxidation is demonstrated. Application of constant potential difference between two electrodes in the bipolar electrochemical cell led to increase in C2H4 conversion. A proposed mechanism explains the bipolar EPOC phenomenon through formation of O2- flux across the electrochemical cell, resulting in the change of Work Function of gold nanoparticles placed in between the electrodes and is electronically isolated.

Plants are exposed to a variety of environmental stresses, ranging from insects and phytopathogens known as biotic stressors, to edaphic stressors including drought and salinity - clustered under the group of abiotic stresses. Facing these pernicious risks, plants have adopted several strategies to survive in stressful environments. With contemporary advances in technology and scientific research, it is possible to insert a specific gene or trait into a plant in order to confer salt tolerance. For example, a thiol methyltransferase enzyme in cabbage converts Cl¯ and other halide ions into their corresponding methyl halides, which are released directly into the air. Cloning the TMT1 gene and functionally expressing this gene into tobacco plants conferred salt tolerance on these plants. Although increased salt tolerance is a favourable and beneficial trait for plant productivity, the emission of methyl halides into the atmosphere can be noxious for the environment. Indeed, methyl halides are some of the factors contributing to climate change, widely believed to be the foremost environmental problem of the twenty-first century. Climate change is affecting all forms of life on earth and its impacts are often severe and irreversible. For that reason, it has been placed at the forefront of the international political agenda. The present study focused on two main physiological traits of stress resistance in tobacco plants which have been genetically engineered with the cabbage TMT1 gene: The production of methyl halides, particularly methyl chloride, as a way to confer salt tolerance; and synthesis of the stress hormone, ethylene. Both pathways share a common metabolite, S-adenosyl-L-methionine (SAM), for the synthesis of the final products. SAM, derived from the amino acid methionine (Met), is a universal methyl group donor. It plays essential roles in plant metabolism, by acting as a precursor for ethylene, polyamines, and vitamin B1 synthesis, and as a source of atmospheric dimethylsulphides. Therefore, it is important that the plant maintains the SAM pool at a level sufficient to serve all the different metabolic pathways. The present work set out to determine whether addition of another SAM-dependent pathway through TMT insertion in tobacco plants would negatively affect ethylene synthesis by lessening the amount of SAM available for ethylene biosynthesis. Detailed experimental studies were conducted, including in vitro and in vivo experiments, to examine the potential effect of TMT gene insertion on SAM availability for ethylene synthesis in tobacco plants. Three series of in vitro tests, differing by the number of leaf discs used, the final headspace volume in each flask, the incubation period in the different solutions and the time of introducing salt solutions, were carried out. Data obtained from two series of in vitro experiments revealed a decrease in ethylene emission when salt solutions were added at the beginning of the experiment and when leaves where incubated overnight in the presence of 0.1 M NaBr, coupled with the production of methyl halides, whereas the other series of in vitro tests as well as the in vivo results showed no alteration in ethylene accumulation because of TMT insertion when tobacco leaves were exposed to salt treatments. According to the results presented in this study, the amounts of available SAM in transformed tobacco are likely sufficient to serve both ethylene and methyl halides biosynthetic pathways. Besides, in vivo results indicate that inserting the TMT1 gene that improves salt stress resistance in tobacco should not dramatically alter ethylene synthesis, and therefore, would be unlikely to affect any physiological trait associated with ethylene production if this gene is used to engineer salt tolerance in high-value crops. Although TMT insertion does not alter ethylene emission in transgenic plants and tends to be an efficient tool to confer salt tolerance in halo-intolerant crops, its environmental cost is of great concern and, therefore, should be taken into consideration to mitigate the amounts of methyl halides emitted into the atmosphere because of this insertion.