No description available.

No description available.

M.Sc. / It is the widely accepted view that the human immunodeficiency virus (HIV) is the causative agent of acquired immunodeficiency syndrome (AIDS) and that South Africa harbors mainly HIV type 1 subtype C (HIV-1 C). Extensively characterized biological isolates (especially of HIV-1 subtype C) for use in HIV/AIDS vaccine and drug development are not readily available. This study evaluated three different protocols for the expansion of virus from infected PBMC's of 68 HIV/AIDS patients (designated HJ1 — 22 and INN1 — 97). Factors influencing the success of a protocol for the expansion of HIV-1 were 1) the amount and time of addition of IL-2 and PHA to the culture media; 2) the fact that freshly isolated clean PBMC's (treated with PHA prior to co-cultivation) was necessary while infected PBMC's could be used fresh or frozen; 3) whether the absence or presence of polybrene as a tissue culture additive had any effect. The I-11V-status of patients could be confirmed with rapid tests and/or NASBA assays, while successful expansion of the virus could be confirmed or refuted by determining p24 levels of sera or culture supematant (with values ranging from <7.8pg/ml to about 280pg/ml). Less sensitive assays like the reverse transcriptase (RT) and gpl 20 ELISA's give much lower absorbance values when compared to the p24 ELISA. Using expanded virus to infect PBMC's and T-cell lines (PM1, U87.CD4-CCR5, U87.CD4-CXCR4 and CEM.NKR-CCR5) and then measuring p24 levels showed that the final protocol chosen was capable of producing high titre, biologically active virus. To further test the biological activity of the isolates, the virus was used in assays evaluating the potential inhibitory ability of natural products and neutralizing antibodies. PCR using universal primers (SK22/SK38/SK39) was not consistently successful in amplifying out the correct sized region of gag (for SK22/SK39 a fragment of 600bp and a 115bp fragment for SK38/SK39 was obtained but not for all the samples). Primers (Cgag189(+/-)) were designed during this project to specifically amplify an 189bp region of gag from subtype C, which proved (in some instances) to be more successful. PCR amplification of the proviral DNA fragments was confirmed by sequencing of selected PCR products. Virus titre was determined by calculating TCID50 (login: 1.054). By modifying expansion and detection protocols it is possible to standardize the process to suit a particular isolate and/or circumstance. This production of large volumes of high titre, biologically active isolates has filled a desperate need for reagents to aid HIV researchers in the development of an effective vaccine or other drug therapy.

The area of chemical research and synthesis increasingly recognises the need for improved technologies and methods, which involves chemical processes with less energy consumption, time savings, reduction and/or minimisation of waste, simple processes and an overall clean production. Microwave heating has been exploited in a variety of disciplines for many useful applications and organic synthesis is an area, which has benefited significantly over the past decade. The present study investigates organic reactions accelerated under microwave irradiations. In particular, the study involves use of recyclable Polymer and Inorganic Solid Supported Reagents for application in transfer hydrogenation. Reductions of electron deficient alkenes have been studied using polymer and inorganic solid supported formates. Microwave irradiations have been used to study transfer hydrogenations in presence of Wilkinson's catalyst [RhCl(PPh3)3]. The application of the Polymer Supported Reagents (PSR) has been investigated for studying transfer hydrogenation in N-benzyl deprotections. Microwave assisted synthesis of formamides from primary and secondary amines have been studied using supported formates. Microwave irradiations have also been applied in studying heterocycle synthesis by cycloaddition of nitrones with Pt (II) and Pd(II) bound organonitriles. The study broadly demonstrates a means of simplifying reaction procedures and purification along with reduction in waste of reagents and release of toxic residues. More importantly, use of microwave irradiations has been used to substantially improve the reaction yields and reduce reaction times, lower energy consumption and solvent volumes. The use of this methodology significantly benefits in the development of "Green Chemistry" and automated systems for chemical synthesis in many industrial sectors.

No description available.

Electrochemical methods, surface spectroscopy and flotation tests have been used to study the influence of the oxidation of arsenopyrite on its floatability with xahthate. Cyclic voltammetric studies indicated that the oxidation of arsenopyrite at pH greater than 7 results in the formation of ferric hydroxide deposits on the surface of the mineral. Arsenic is oxidized to arsenate and sulphur is oxidized to sulphate. The arsenate is incorporated in the ferric hydroxide deposits while sulphate diffuses into solution. Below pH=7, soluble iron species are formed and the surface becomes increasingly covered with elemental sulphur with decreasing pH. Increasing temperature has no influence on the quantity of hydroxide formed over the range 30° to 45°C but results in thick, porous films at temperature greater than 45°C. The oxidation of arsenopyrite was demonstrated to occur at lower oxidation potentials than for pyrite although this effect decreased with increasing temperature. Mixed potential studies indicated that the potentials required for arsenopyrite oxidation could be achieved with common oxidizing agents. Selective oxidation of arsenopyrite in a bulk pyrite-arsenopyrite concentrate was indicated to be possible. The formation of iron hydroxide deposits on the surface of arsenopyrite resulted in the inhibition of subsequent oxidation of xanthate to dixanthogen at the mineral's surface. ESCA studies confirmed the formation of oxidized iron layers at the surface of arsenopyrite and revealed that essentially all the arsenate which was formed was incorporated in these layers. Sulphur became oxidized at the pH studied and to a large extent went into solution. Flotation studies demonstrated the use of oxidation for arsenopyrite depression. In the presence of oxidation, increasing pH above pH=7 resulted in increased arsenopyrite depression while increasing temperature had little effect until a temperature of 40°C was exceeded. Previously activated arsenopyrite could be depressed through the use of oxidizing agents. Arsenopyrite could be selectively depressed from a bulk pyrite-arsenopyrite concentrate through the use of oxidizing agents. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

This thesis describes the preparation of 4-chloro-2-trimethyl-stannyl-1-butene (8̲4̲) and its conversion into a number of structurally interesting and synthetically useful donor-acceptor reagents. Thus, transmetalation of (8̲4̲) with methyllithium produced 4-chloro-2-lithio-1-butene (9̲5̲), which reacted smoothly at -78°C in tetrahydrofuran with aldehydes, ketones and α,β-unsaturated N,N',N'-trimethylcarboxhydrazides to provide the addition products (1̲0̲8̲)-(̲1̲1̲3̲) and (̲1̲2̲8̲)-(̲1̲3̲0̲). When the reaction mixtures were treated with hexamethylphosphoramide and were then allowed to warm to room temperature, the 3-methylenetetrahydro-furan derivatives (̲1̲1̲4̲)-(̲1̲1̲9̲) and the 3-methylenecyclopentanecarboxylic acid derivatives (̲1̲3̲1̲)-(̲1̲3̲3̲) were produced in good yields. Treatment of reagent (̲9̲5̲) with 1 equiv of phenylthiocopper or cuprous cyanide provided solutions of the corresponding cuprate reagents (̲1̲7̲9̲) and (̲1̲8̲0̲). Conjugate addition of the latter species to the cyclic enones (̲1̲8̲1̲)-(̲1̲8̲6̲) afforded very good yields of the ketones (̲1̲8̲7̲)-(̲1̲9̲2̲), which, when treated with potassium hydride in tetrahydrofuran, provided the methylenecyclopentane annulation products (̲1̲̲9̲3̲)-(̲1̲9̲8̲), respectively. This methylenecyclopentane annulation method served as a key process in the total synthesis of two structurally interesting triquinane sesquiterpenoids, (±)-Δ⁹⁽¹²⁾ -capnellene (̲2̲0̲5̲) and (±)-pentalenene (̲2̲5̲1̲). Thus, copper bromide - dimethylsulfide catalyzed addition of the Grignard reagent (̲2̲3̲3̲) to 2-methyl-2-cyclopenten-1-one (̲1̲8̲4̲), followed by intramolecular alkylation of the resultant chloro ketone (̲1̲9̲0̲), gave the annulation product (̲1̲9̲6̲). This material was converted into the enone (̲2̲3̲1̲) , which was subjected to an annulation sequence identical with that used in the conversion of (̲1̲8̲4̲) into (̲1̲9̲6̲). Removal of the carbonyl group from the resultant product (̲2̲3̲2̲) provided (±)-Δ⁹⁽¹²⁾ capnellene (̲2̲0̲5̲). Transformation of the readily available keto acetal (̲2̲8̲̲7̲) into the enone (̲2̲8̲4̲), followed by subjection of the latter substance to the methylenecyclopentane annulation sequence, gave the tetracyclic keto olefin (̲2̲8̲5̲). Treatment of an acetic acid solution of this material with hydrogen in the presence of platinum metal produced a mixture of the epimeric ketones (2̲9̲8̲) and (2̲9̲9̲), which was converted into a mixture of (±)-pentalenene (2̲5̲1̲) and (±)-9-e̲p̲i̲-pentalenene (2̲6̲9̲), respectively. [Formula Omitted] / Science, Faculty of / Chemistry, Department of / Graduate

No description available.

No description available.

No description available.