List of Titles

Quick View

Halogenated Aza-BODIPY dyes for photodynamic anticancer and antimicrobial activity studies

- Magwaza, Temlandvo Matshidiso

Authors: Magwaza, Temlandvo Matshidiso
Date: 2023-10-13
Subjects: Uncatalogued
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/424514 , vital:72160
Description: This thesis reports on the synthesis and characterisation of differently substituted aza-BODIPY dyes for use in photodynamic antimicrobial chemotherapy (PACT) and photodynamic therapy (PDT) activity studies. The aza-BODIPY dyes were synthesised by adding phenyl and naphthyl rings at the 3,5-positions of the aza-BODIPY core, with methylthiolphenyl (9a and 9b, respectively) or thien-2-yl rings (9c and 9d, respectively) at the 1,7-positions. 9a-c were iodinated at the 2-position to form 10a-c, respectively, while 9d was diiodinated at the 2,6-positions to form 10d. The methylthiolphenyl-substituted dyes (10a and 10b) were successfully conjugated to gold nanoparticles (AuNPs) to form nanoparticles conjugates (10a-AuNPs and 10b-AuNPs), while attempts to conjugate the thien-2-yl-substituted dyes were unsuccessful. The photophysicochemical properties of 9a-d, 10a-d and nanoconjugates 10a-AuNPs and 10b-AuNPs were investigated to determine their suitability for use in the applications. Adding heavy atoms such as iodine at the 2,6-positions of the aza-BODIPY led to enhanced singlet oxygen generation since these dyes displayed moderate to high singlet oxygen quantum yields. None of the dyes exhibited any fluorescence. The PACT activity studies for 9c-d, 10a-d, and the 10a-AuNPs and 10b-AuNPs were carried out against Staphylococcus aureus and Escherichia coli with a Thorlabs M660L3 light-emitting diode (LED) with an irradiance of 280 mW/cm2 for all dyes other than 10d. A Thorlabs M730L4 LED with an irradiance of 160 mW/cm2 was used for 10d. Time dependence studies were only carried out against Staphylococcus aureus, so very low log reductions were observed against Escherichia coli in initial concentration studies. The 10a-AuNP and 10b-AuNP nanoconjugates exhibited high antimicrobial activity with a log reduction of 9.41 and 0.00% viable colonies, while the iodinated aza-BODIPY had a log reduction of 8.94. The in vitro photodynamic therapy activities and dark cytotoxicity were investigated against human MCF-7 breast cancer cells for dyes 9c-d and 10c-d with a Thorlabs M660L3 LED (280 mW/cm2) for all dyes. The dark cytotoxicity was minimal in each case with IC50 > 50. Iodinated dyes 10c and 10d had IC50 values of 11.6 and 8.2 μM, respectively, and non-iodinated dyes 9c and 9d had IC50 values of 12.5 and 19.2 μM. The heavy atom effect associated with the iodine atoms increases the singlet oxygen quantum yield and enhances the suitability of the dyes for photodynamic therapy. , Thesis (MSc) -- Faculty of Science, Chemistry, 2023
Full Text:
Date Issued: 2023-10-13

Quick View

HI View of the Norma Galaxy Cluster with MeerKAT

- Mophahlane, Koketso Vincent

Authors: Mophahlane, Koketso Vincent
Date: 2023-10-13
Subjects: Uncatalogued
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/432530 , vital:72878
Description: Studies reveal that galaxies assemble into clusters as gas-rich, active star-forming disks and eventually settle in the virialized core as quenched early-type galaxies with depleted gas. To examine environmental effects responsible for the quenched population in the cluster core, we exploit the higher sensitivity of the MeerKAT telescope to probe Hi properties of galaxies in the Norma cluster. The Norma cluster is an ideal laboratory for this study since it is a rich and massive cluster of nearby galaxies. The Hi data cube used covers a velocity range of 483 − 11, 113 km/s, with a noise rms sensitivity of 0.09 mJy/beam and an angular resolution of ∼ 14.65′′ × 9.28′′. A total of 25 reliable Hi sources were detected over the entire velocity range. The Hi detections reveal two major galaxy overdensities located at vrad ∼ 2096 − 7646 km/s and vrad ∼ 10, 000 km/s. The first is associated with the Norma cluster gravitational potential and indicates a substructure in its velocity distribution; the other is a population of background galaxies. In this work, the Norma cluster has 13 cluster members detected in Hi and 130 galaxies from optical surveys. The spatial distribution of cluster members covers a field that is 2/3 × RA, where RA = 2.02 Mpc at cz = 4871 km/s. From the spatial distribution, optical galaxies are densely populated in the central regions, while most galaxies in Hi were detected on the outskirts. From the phase-space diagram, 6 galaxies detected in Hi are found in the virialised region, while the rest of the detections are infalling for the first time. Hi detections that are not yet virialised have asymmetrical morphologies, while virialised detections have truncated gas disks. Most cluster members that were found to have asymmetrical gas disks are also Hi deficient by 0.8 − 1.2 dex but show excess SFR efficiency for the amount of Hi detected. The results demonstrate that the initial phase of galaxy-ICM interactions might be responsible for morphological transformation and enhancement of star formation activity. , Thesis (MSc) -- Faculty of Science, Physics and Electronics, 2023
Full Text:
Date Issued: 2023-10-13

Quick View

High-resolution hydraulic modelling as an approach to planning rehabilitation interventions in unchanneled valley-bottom palmiet wetlands: a case study of the Kromme River

- Langner, Wiebke

Authors: Langner, Wiebke
Date: 2023-10-13
Subjects: Uncatalogued
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/424610 , vital:72168
Description: This study employs high-resolution hydraulic modelling techniques to inform the planning of rehabilitation interventions in unchanneled valley-bottom palmiet wetlands, using the upper Kromme River wetlands as a case study. It investigates the impact of geomorphic processes on the morphology of the valley, how changes in valley morphology affect the flow characteristics (velocity, stream power, depth) of the river, and how these changes affect the geomorphic dynamics of the wetlands. An aerial LiDAR survey was conducted for a 23km-long reach of the upper Kromme River where the wetlands are situated. A high-resolution (5 m) DTM was created from the LiDAR data to examine the valley morphology. Focusing on three major wetland basins, the relationship between valley morphology and geomorphic processes was examined using high-resolution imagery that accompanied the LiDAR survey and Google Satellite imagery. The hydraulic modelling software HEC-RAS was used to investigate the spatial variation in velocity, stream power, and water depth down the surveyed length of the river. The model outputs provide insight into the effect of valley morphology on flow characteristics. The river appears to have a graded longitudinal profile, such that there is a systematic reduction in slope down its length. Water flowing down the river works, through the processes of erosion and deposition, to control the longitudinal slope, channel planform, and geometry to create a valley with a gentle longitudinal slope (approximately 1%) and a broad, near-horizontal valley-bottom in the mountainous landscape of the Cape Fold Mountains. The overall form of the Kromme River valley and wetlands is primarily a consequence of repeated cycles of cutting and filling. Tributary alluvial fans control the initiation of gully erosion in the wetlands, but their effect is diminished in a downstream direction. Despite a 10-fold increase in discharge down the 23km length of river for a given flood magnitude, there is no significant increase in flow velocity, stream power, or depth in a downstream direction. Consequently, the kinetic energy of the water in the lower wetland basin is surprisingly low. These conditions favour the establishment of palmiet. Flows in eroded reaches are much higher than in non-eroded reaches where discharge is spread across a broad valley bottom. In terms of palmiet establishment and regeneration, this means that areas dominated by depositional processes are best suited to the establishment of palmiet. Based on this information, optimal sites to trial new wetland rehabilitation strategies that employ palmiet were selected. This work supports the importance of understanding the role of geomorphology in wetland structure and dynamics when approaching wetland rehabilitation and is likely to be more sympathetic to natural processes than current interventions. , Thesis (MSc) -- Faculty of Science, Geography, 2023
Full Text:
Date Issued: 2023-10-13

Quick View

Identification of novel Arf1 GTPase inhibitors for cancer target validation

- Mqwathi, Nomxolisi Vuyokasi

Authors: Mqwathi, Nomxolisi Vuyokasi
Date: 2023-10-13
Subjects: Uncatalogued
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/424666 , vital:72173
Description: The key regulators of both anterograde and retrograde vesicular traffic, adenosine diphosphate-ribosylation factors (Arfs), also coordinate various signalling pathways and regulate cellular processes required for cell survival and function. In addition to its role in mediating secretory trafficking in the Golgi apparatus, the involvement of Arf1 in signalling pathways that contribute to the formation and progression of cancer has become apparent, and the overexpression and deregulation of Arf1 activity has been associated with cancer cell invasion, proliferation and metastasis. As with other small GTPases, Arf1 must cycle back and forth between an inactive (GDP-bound) and active (GTP-bound) conformation to carry out its function. However, the cycle of Arf1 inactivation and activation is controlled by Arf GTPase activating proteins (Arf-GAPs) that stimulate Arf1 to hydrolyse the bound GTP to GDP and Arf guanine nucleotide exchange factors (Arf-GEFs) that facilitate GDP for GTP exchange on Arf1, respectively. The identification of Arf1 inhibitors that indirectly disrupt Arf1 function by blocking its interaction with Arf-GAPs or Arf-GEFs has generated interest in their use as possible anti-cancer agents. The suppression of Arf1 activation (by targeting Arf-GEFs) has been investigated as a potential cancer therapeutic target and resulted in inhibitor compounds that have micromolar-range activity against cancer cells and targets and promising results in mouse models, but experience problems with bioavailability when used in vivo. This motivates the search for novel Arf1 inhibitors for validation purposes to question whether Arf1 is a viable target for cancer therapy. The purpose of the study was to employ a recently developed colourimetric screening assay to identify inhibitors of Arf1 activation (Arf-GEF inhibitors) and deactivation (Arf-GAP inhibitors), with a focus on evaluating the potential of Arf1 deactivation as an entirely novel anti-cancer target. The proteins required for the assay (Arf1, Arf-GEF and -GAP domains and a reporter protein, GST-GGA3) were expressed in E. coli. and purified using affinity chromatography. The assay could detect the activation of Arf1 by the catalytic Sec7 domain of the three Arf-GEFs chosen for this study, but reproducibility was compromised by the occasional spontaneous activation of Arf1 in the absence of the Arf-GEFs. By contrast, the assay could reproducibly detect Arf1 deactivation by an Arf-GAP domain (Arf-GAP1GAP) and was subsequently used to screen a library of α-helix mimetics. Thirteen hit compounds with IC50 values ranging from 0.53 to 20.95 μM were found to inhibit Arf-GAP1GAP-mediated stimulation of GTP hydrolysis by Arf1-GTP in this assay format, however, they did not effectively suppress the proliferation of three tested cell lines (HeLa, MCF-7 and MCF-12A). Interestingly, the results obtained from fluorescence microscopy studies suggested that the compounds disrupt Golgi structure and Arf1 localisation, presumably by keeping Arf1 in its active conformation by blocking Arf-GAP1 function. This suggests that the compounds affect Arf1 function in cells, and may be used to explore the feasibility of targeting Arf1 deactivation for anti-cancer purposes in a wider range of cell lines and experiments. It has been reported that Arf-GAP1 inhibition is associated with the suppression of cell migration, and the potential of the compounds as metastasis inhibitors may also be explored. , Thesis (MSc) -- Faculty of Science, Biochemistry and Microbiology, 2023
Full Text:
Date Issued: 2023-10-13

Quick View

Implementing a sexual and reproductive citizenship intervention refinement instrument for youth sexuality education: a formative evaluation

- Mthethwa, Thobile

Authors: Mthethwa, Thobile
Date: 2023-10-13
Subjects: Uncatalogued
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/425008 , vital:72201
Description: While Out of School sexuality education (SE) programmes in South Africa have attempted to bridge the gap in the number of young people who receive SE, there is still a large number of youth between the age groups of 15 to 24 years who lack adequate sexual knowledge. The manner in which sex education is taught and its accessibility is accompanied by challenges, in particular in relation to empowerment. To better understand the effectiveness of sexual education programmes, evaluations of their content is needed. Therefore, the purpose of this study was to investigate whether and how an Out of school SE programme run by Partners in Sexual Health (PSH) promotes understandings of sexual and reproductive citizenship. A formative evaluation of their sexual and reproductive health and rights (SRHR) facilitator’s manual was conducted (owing to COVID the actual programme was not run in the year data for this thesis were collected). To help perform the formative evaluation, the feminist sexual and reproductive citizenship (SRC) framework as conceptualized by Macleod and Vincent (2014) was used. The SRC framework consists of five key principles that, it is suggested, need to be adopted for SE programmes to be inclusive, namely, citizenship as status and practice, differentiated citizenship, private and public interstice, and politics of recognition, redistribution and reparation. An additional principle of inclusive and process-based educational practices was added into the five key principles. To analyse data, template analysis was used which enabled the researcher to create a priori of themes using the Masizixhobise toolkit which is informed by the SRC framework. Findings from this study reveal the interconnectedness between the different citizenship principles. Moreover, while the PSH SRHR programme promotes principles of the SRC framework, there are aspects of the SRC that are lacking from the programme. Therefore, the SRHR manual needs to take into account a spectrum of issues which include but are not limited to the incorporation of sexually diverse differently-abled individuals' sexual experiences and challenges when it comes to accessing SE. This means for SE programmes to achieve inclusivity and to be empowering, they need to encourage individuals to be agentic beings, engage in informed decision-making and encourage young people to take up their rights. , Thesis (MA) -- Faculty of Humanities, Psychology, 2023
Full Text:
Date Issued: 2023-10-13

Quick View

In silico characterization of missense mutations in infectious diseases: case studies of tuberculosis and COVID-19

- Barozi, Victor

Authors: Barozi, Victor
Date: 2023-10-13
Subjects: Uncatalogued
Language: English
Type: Academic theses , Doctoral theses , text
Identifier: http://hdl.handle.net/10962/431626 , vital:72791 , DOI 10.21504/10962/431626
Description: One of the greatest challenges facing modern medicine and the global public health today is antimicrobial drug resistance (AMR). This “silent pandemic,” as coined by the world health organization (WHO), is steadily increasing with an estimated 4.95 million mortalities attributed to AMR in 2019, 1.27 million of which were directly linked to AMR. Some of the contributors to AMR include self-prescription, drug overuse, sub-optimal drug prescriptions by health workers, and inaccessibility to drugs, especially in remote areas, which leads to poor adherence. The situation is aggravated by the upsurge of new zoonotic infections like the coronavirus disease 2019, which present unique challenges and take the bulk of resources hence stunting the fight against AMR. Quite alarming still is our current antimicrobial arsenal, which hasn’t had any novel antimicrobial drug discovery/addition, of a new class, since the 1980s. This puts a burden on the existing broad-spectrum antimicrobial drugs which are already struggling against multi-drug resistant strains like multi-drug resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB). Besides the search for new antimicrobial agents, the other avenue for addressing AMR is studying drug resistance mechanisms, especially single nucleotide polymorphisms (SNPs), that change drug target characteristics. With the advancement of computational power and data storage resources, computational approaches can be applied in mutational studies to provide insight into the drug resistance mechanisms with an aim to inform future drug design and development. Therefore, in the first part of this thesis, we employ integrative in silico approaches, including 3D structure modeling, molecular dynamic (MD) simulations, comparative essential dynamics (ED), and protein network analysis approaches i.e., dynamic residue network (DRN) analysis to decipher drug resistance mechanisms in tuberculosis (TB). This involved an investigation of the drug resistance mutations in the catalase-peroxidase (KatG) and pyrazinamidase (MtPncA) enzymes which are responsible for activation of TB first-line drugs; Isoniazid (INH) and Pyrazinamide (PZA), respectively. In the case of KatG, eleven high confidence (HC) KatG mutations associated with a high prevalence of phenotypic INH resistance were identified and their 3D structures modeled before subjecting them to MD simulations. Global analysis showed an unstable KatG structure and active site environment in the mutants compared to the wildtype. Active site dynamics in the mutants compromised cofactor (heme) interactions resulting in less bonds/interactions compared to the wildtype. Given the importance of the heme, reduced interactions affect enzyme function. Trajectory analysis also showed asymmetric protomer behavior both in the wildtype and mutant systems. DRN analysis identified the KatG dimerization domain and C-terminal domain as functionally important and influential in the enzyme function as per betweenness centrality and eigenvector centrality distribution. In the case of the MtPncA enzyme, our main focus was on understanding the MtPncA binding ability of Nicotinamide (an analogue of PZA) in comparison to PZA, especially in the presence of 82 resistance conferring MtPncA mutations. Like in KatG, the mutant structures were modeled and subjected to MD simulations and analysis. Interestingly, more MtPncA mutants favored NAM interactions compared to PZA i.e., 34 MtPncA mutants steadily coordinated NAM compared to 21 in the case of PZA. Trajectory and ligand interaction analysis showed how increased active site lid loop dynamics affect the NAM binding, especially in the systems with the active site mutations i.e., H51Y, W68R, C72R, L82R, K96N, L159N, and L159R. This led to fewer protein-ligand interactions and eventually ligand ejection. Network analysis further identified the protein core, metal binding site (MBS), and substrate binding site as the most important regions of the enzyme. Furthermore, the degree of centrality analysis showed how specific MtPncA mutations i.e., C14H, F17D, and T412P, interrupt intra-protein communication from the MtPncA core to the MBS, affecting enzyme activity. The analysis of KatG and MtPncA enzyme mutations not only identified the effects of mutations on enzyme behaviour and communication, but also established a framework of computational approaches that can be used for mutational studies in any protein. Besides AMR, the continued encroachment of wildlife habitats due to population growth has exposed humans to wildlife pathogens leading to zoonotic diseases, a recent example being coronavirus disease 2019 (COVID-19). In the second part of the thesis, the established computational approaches in Part 1, were employed to investigate the changes in inter-protein interactions and communication patterns between the severe acute respiratory coronavirus 2 (SARS-CoV-2) with the human host receptor protein (ACE2: angiotensin-converting enzyme 2) consequent to mutations in the SARS-CoV-2 receptor binding domain (RBD). Here, the focus was on RBD mutations of the Omicron sub-lineages. We identified four Omicron-sub lineages with RBD mutations i.e., BA.1, BA.2, BA.3 and BA.4. Each sub-lineage mutations were modeled into RBD structure in complex with the hACE2. MD analysis of the RBD-hACE2 complex highlighted how the RBD mutations change the conformational flexibility of both the RBD and hACE2 compared to the wildtype (WT). Furthermore, DRN analysis identified novel allosteric paths composed of residues with high betweenness and eigenvector centralities linking the RBD to the hACE2 in both the wildtype and mutant systems. Interestingly, these paths were modified with the progression of Omicron sub-lineages, highlighting how the virus evolution affects protein interaction. Lastly, the effect of mutations on S RBD and hACE2 interaction was investigated from the hACE2 perspective by focusing on mutations in the hACE2 protein. Here, naturally occurring hACE2 polymorphisms in African populations i.e., S19P, K26R, M82I, K341R, N546D, and D597Q, were identified and their effects on RBD-hACE2 interactions investigated in presence of the Omicron BA.4/5 RBD mutations. The hACE2 polymorphisms subtly affected the complex dynamics; however, RBD-hACE2 interaction analysis showed that hACE2 mutations effect the complex formation and interaction. Here, the K26R mutation favored RBD-hACE2 interactions, whereas S19P resulted in fewer inter-protein interactions than the reference system. The M82I mutation resulted in a higher RBD-hACE2 binding energy compared to the wildtype meaning that the mutation might not favor RBD binding to the hACE2. On the other hand, K341R had the most RBD-hACE2 interactions suggesting that it probably favors RBD binding to the hACE2. N546D and D597Q had diminutive differences to the reference system. Interestingly, the network of high betweenness centrality residues linking the two proteins, as seen in the previous paragraph, were maintained/modified in presence of hACE2 mutations. HACE2 mutations also changed the enzyme network patterns resulting in a concentration of high eigenvector centrality residues around the zinc-binding and active site region, ultimately influencing the enzyme functionality. Altogether, the thesis highlights fundamental structural and network changes consequent to mutations both in TB and COVID-19 proteins of interest using in silico approaches. These approaches not only provide a new context on impact of mutations in TB and COVID target proteins, but also presents a framework that be implemented in other protein mutation studies. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2023
Full Text:
Date Issued: 2023-10-13

Quick View

In-silico investigation of the effects of genetic mutations on the structural dynamics of thiopurine s-methyltransferase and their implications on the metabolism of 6-mercaptopurine

- Mwaniki, Rehema Mukami

Authors: Mwaniki, Rehema Mukami
Date: 2023-10-13
Subjects: Uncatalogued
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/432553 , vital:72880
Description: Thiopurine S-methyltransferase (TPMT) is a cytosolic enzyme that catalyzes the S-methylation of aromatic and heterocyclic sulfhydryl compounds such as 6-mercaptopurine (6MP), 6-thioguanine (6TG) and azathioprine (AZA) which is first converted to 6MP through reduction by glutathione S- transferases (GST). The compounds, generally referred to as thiopurines, are immunosuppressants used to treat childhood acute lymphoblastic leukemia (ALL), autoimmune disorders and transplant rejection. Thiopurines are prodrugs which require metabolic activation to give thioguanine nucleotides that exert their cytotoxic effects by incorporation into DNA or inhibiting purine synthesis. The methylation reaction by TPMT utilizing S-adenosylmethionine (SAM) as the methyl donor prevents their conversion to these toxic compounds. The catalytic activity of TPMT in metabolising these compounds has been associated with occurrence of genetic variations. The variations that result to missense mutations cause amino-acid changes and in turn alter the polypeptide sequence of the protein. This could alter functionality and structural dynamics of the enzyme. This study sought to understand the underlying mechanism by which 7 specially selected mutations impede metabolic activity of the enzyme on 6-MP using in silico techniques. VAPOR and PredictSNP were used to predict the effects of single nucleotide polymorphisms (SNPs) on the stability and function of the enzyme. Of the 7 mutations, only H227Q was predicted to be functionally benign while the rest (L49S, L69V, A80P, R163H, R163C and R163P) were predicted to be deleterious or associated with disease. All the SNPs were predicted to destabilize the enzyme. Molecular dynamics (MD) simulations were preformed to mimic the behaviour of the apo, holo and drug-bound WT and mutant enzymes in vivo. This was followed by post-MD analysis to identify changes in the local and global motions of the protein in the presence of mutations and changes in intra-protein communication networks through contact map and centrality metrics calculations. RMSD and Rg analyses were performed to assess changes in global motions and compactness of the enzyme in the apo, holo and drug-bound states and in the presence of mutations. These revealed that binding of the ligand had a stabilizing effect on the WT enzyme evident from more steady trends from the analyses across trajectories in the holo and drug-bound enzymes compared to the apoenzyme. The occurrence of mutations had an effect on the global motions and compactness of the enzyme across the trajectories. Most mutations resulted in destabilized systems and less compact structures shown by unsteady RMSD and Rg across trajectories respectively. The drugbound systems appeared to be more stable in most of the systems meaning that the binding of 6MP stabilized the enzyme regardless of the presence of a mutation. RMSF analysis recorded local changes in residue flexibility due to the presence of mutations in all the systems. All the drug-bound mutant systems lost flexibility on the αAhelix which caps the active site. This could have an effect on drug binding and result to defective drug metabolism. The A80P mutation resulted to a more rigid structure from both global and local motions compared to the WT enzyme which could be associated with its nearly loss of function in vivo and in vitro. Dynamic cross correlation calculations were performed to assess how the atoms moved together. Correlated, anti-correlated and areas of no correlations were recorded in all the systems and in similar places when compared to each other. This meant that occurrence of mutations had no effect on how the atoms moved together. Contact map analysis showed that occurrence of mutations caused changes in interactions around the positions where the mutations occurred, which could have an effect on protein structural dynamics. The A80P substitution which occurred on the surface away from the binding site was identified as an allosteric mutation that resulted to changes in the catalytic site. Contact maps for the drug-cofactor complex in the mutant systems in comparison with the WT protein revealed changes that could suggest reorientation of the drug at the catalytic site. This could be an implication to altered drug metabolism. Eigenvector centrality (EC) and betweenness centrality (BC) for the most equilibrated portions of the trajectories were calculated for all the studied systems to identify residues connected to the most important residues and those that were spanned the most in shortest paths connecting other residues. Areas that scored highest in these metrics where mostly found in regions surrounding the catalytic site. Top 5% centrality hubs calculations showed loss of major hubs due to mutations with gaining of new ones. This means that mutations affected communication networks within the protein. The gained hubs were in areas close-by the lost ones which could have been an attempt of the protein to accommodate the mutations. Persistent top 5% BC hubs were identified at positions 90 and 151 while one persistent top 5% EC hub was identified at position 70. This positions play important roles in shaping the catalytic site and are in direct contact with the ligands. It was concluded that in silico techniques and analysis applied in this study revealed possible mechanisms in which genetic variations affected the structural dynamics of TMPT enzyme an affecte 6MP metabolism. , Thesis (MSc) -- Faculty of Science, Biochemistry and Microbiology, 2023
Full Text:
Date Issued: 2023-10-13

Quick View

International students’ experiences of othering in tertiary education in South Africa: an exploratory study

- Lobakeng, Tsholofelo

Authors: Lobakeng, Tsholofelo
Date: 2023-10-13
Subjects: Uncatalogued
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/424986 , vital:72199
Description: Despite rising cases of xenophobia in South Africa, international students remain committed to enrolling in its universities. Surprisingly, there is limited research looking into xenophobia in tertiary institutions. Therefore, the present study aimed to contribute to the scarcity of knowledge on the experiences of international students in South Africa. Thus, the study explored experiences of Othering among international students in tertiary education in South Africa and how they make sense of these experiences. Purposive and snowballing sampling techniques were employed to recruit international students (N=5) from Botswana, China, Zambia, and Zimbabwe. Data was collected through semi-structured, face-to-face online interviews. Participants reported experiencing a variety of non-violent forms of Othering, such as feeling excluded due to the intentional use of local languages in both classroom and social settings; being rejected by local students who refused to work with them; and being accused of stealing opportunities from local students. At an institutional level, participants reported systemic Othering rooted in unsupportive policies and practices that led to a negative and oppressive environment. The findings support previous research studies that purport the Othering of international students in higher education in South Africa mainly manifests through non-violent and covert forms. Moreover, participants attributed Othering of immigrants to racism, a perceived lack of exposure to diversity among locals, perceived lack of compassion for immigrants, and the tendency to scapegoat immigrants for the lack of employment opportunities in the country. The findings underscore the intricate nature of Othering and the need for further research to gain a greater understanding of this complex phenomenon. Furthermore, the findings highlight the importance of implementing effective strategies of inclusion and integration of international students at these institutions of higher learning. , Thesis (MA) -- Faculty of Humanities, Psychology, 2023
Full Text:
Date Issued: 2023-10-13

Quick View

Investigating pedagogical practices of English First Additional Language educators in Grade 12 short stories: a case study

- Jabe, Sizwe

Authors: Jabe, Sizwe
Date: 2023-10-13
Subjects: Uncatalogued
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/424052 , vital:72119
Description: The focus of this study was to investigate pedagogical practices of English First Additional Language educators in teaching Grade 12 short stories. An interpretive qualitative case study of three educators from three high schools in Chris Hani West district, in Eastern Cape were purposefully selected. Lesson observations, semi-structured interviews, and document analysis (lesson plans) with three English FAL educators were used to collect data. Shulman’s (1986) Pedagogical Content Knowledge was used as the theoretical framework and analytical tool for the study. Data revealed ineffective teaching strategies and on-the-surface subject matter knowledge that hampers the critical teaching of short stories. It also showed that educators have limited knowledge of learners’ learning difficulties and how to address them. The study recommends less teacher talk that was observed in many classes, to be replaced by extended discussions on the part of the learners. Educators should establish a variety of contemporary teaching strategies which put critical thinking and active learning before examination preparation. Lastly, educators, in their teaching of short stories, should consult various resources and attend content workshops to keep subject knowledge up to date. , Thesis (MEd) -- Faculty of Humanities, Study of Englishes of Africa, 2023
Full Text:
Date Issued: 2023-10-13

Quick View

Investigating teachers’ perceptions on translanguaging pedagogy in a multilingual intermediate ESL classroom: a comparative study of two primary schools in Namibia

- Rheeder, Veneza Memory

Authors: Rheeder, Veneza Memory
Date: 2023-10-13
Subjects: Translanguaging (Linguistics) , Second language acquisition , Multilingual education Namibia , Primary school teachers Attitudes , Native language and education Namibia , Primary school teaching Namibia
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/419760 , vital:71673
Description: International literature has tested the effectiveness of translanguaging as a pedagogic tool to enhance learning in a bilingual classroom; however, with the recent curriculum reform and education sector policy, there is no direct claim in the National policy frameworks on the prominence of translanguaging as an effective tool in classroom pedagogy in Namibian schools. This research attempted to investigate the role of translanguaging as a pedagogic tool to enhance learning in the multilingual intermediate English Second Language (ESL) phase as the Language of Learning and Teaching (LoLT) for the intermediate phase, Grades 4-7, in the Erongo Region, Namibia. The study is within the interpretive paradigm and adopts a qualitative methodology using a qualitative multi-case study approach of exploring and understanding differences and similarities between cases. Data collection consisted mainly of open-ended interviews and observations (purposive sampling) of the participating teachers. The research sites and study participants were purposely selected as both schools, diversely located in urban and rural contexts of the region, are enacting the National Language Policy as proposed. This entails using Mother Tongue Instruction (MTI) from Grades 0-3 and then transitioning to English-monolingual instruction from Grades 4 onwards. The study was designed to investigate the role of translanguaging pedagogy in enhancing learning in the Second Language (L2) classroom, without prejudice of social classes - the elite and marginalized communities. It investigated the extent to which teachers’ use of translanguaging pedagogy enhances ESL learning as the LoLT to intermediate phase learners transitioning from MTI to English-only instruction. The main theories underpinning this study are the Vygotskian and Translanguaging theories supported by Krashen and Cummins’ Cognitive Underlying Proficiency (CUP) Model. The outcomes of the study reveal that in both schools translanguaging was supported by content subject teachers and English LoLT teachers and that it positively contributed to improving learner understanding of important concepts in several subjects. However, Mother Tongue (MT) teachers did not support the use of translanguaging and believed that it slowed down the learning of English. , Thesis (MEd) -- Faculty of Education, Institute for the Study of Englishes in Africa, 2023
Full Text:
Date Issued: 2023-10-13

Quick View

Investigation into methods of recovering campylobacter spp. from river water samples

- Ngoni, Nandipha

Authors: Ngoni, Nandipha
Date: 2023-10-13
Subjects: Uncatalogued
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/424177 , vital:72130
Description: Campylobacter species are slender, gram-negative, rod-shaped, spiral- or curved-shaped with single or pairs of flagella. They are the leading cause of diarrheal disease globally, consumption of and contact with water contaminated by faeces is a major risk factor for transmission of these organisms to humans. Rivers used for recreation and domestic and agricultural activities represent all the risk factors for Campylobacter spp. pollution and human exposure. Campylobacter spp. However, effective methods to recover Campylobacter spp. from river water samples are lacking, indicating the need for the development of more efficient methods of detection and isolation of these organisms from environmental water samples. Campylobacter detection in a water sample is critical to ascertain potential risks to humans. The aim of this study was to determine a suitable method for the detection of Campylobacter spp. from river water samples and the objectives were to (i) to evaluate the performance of different methods used for the recovery of Campylobacter spp. from environmental water samples based on Campylobacter colony count and PCR identification results, (ii) isolate and enumerate Campylobacter cells from river water samples, and (iii) identify Campylobacter spp. in river water samples. The Bloukrans River was chosen for this study because it is suspected to be contaminated by faecal inputs from nearby informal settlements without adequate sanitation, as well as untreated/insufficiently treated effluents from nearby wastewater treatment plants. First, the physicochemical quality of the river water and the presence of faecal contamination were assessed to confirm suitability for Campylobacter spp. survival and presence. Then different approaches to sample, concentrate and recover Campylobacter spp. from river water samples were assessed. The different methods assessed were (i) direct enrichment of water samples without prior concentration, (ii) prior concentration of water samples by centrifugation followed by membrane filtration of supernatant, and after that, pooling the residue and pellet together for enrichment, (iii) sampling by the Moore Swab technique. For all three methods, enrichment in Bolton broth supplemented with Bolton antibiotics was conducted. This was followed by plating on modified cefoperazone charcoal deoxycholate agar (mCCDA) and incubation under a microaerophilic atmosphere at 42°C for 48 h. Colony morphology, Gram staining and polymerase chain reaction (PCR) were used to identify and characterize the microorganisms. The growth of blue colonies on the mFc agar surface confirmed presence and faecal pollution of the Bloukrans River. The physicochemical properties, based on the range of pH measured at different sites of the river (between acidic 3.45 to 6.42 and alkaline 7.2 to 8.74) indicate that Campylobacter spp. can thrive in the river. Based on the results from enumeration and sequencing of colonies recovered by each method, it was discovered that the most suitable method to recover Campylobacter spp. from river water samples is by prior centrifugation (14,000 × g for 30 minutes) followed by membrane filtration of the supernatant, and subsequent pooling of the residue and pellet. The pooled residue and pellet might have increased Campylobacter spp. concentrations aiding more growth during the enrichment of Campylobacter spp. from the river water samples. Results from enumerating Campylobacter spp. cells from river water samples indicate that Campylobacter spp. are present in Bloukrans River. The sequence obtained from the PCR product indicates that the species found were Campylobacter jejuni (96% homology as evaluated by BLAST). This study provided a procedure effective for obtaining a satisfactory quantitative recovery of Campylobacter spp. from environmental waters, a critical need for quantitative microbial risk assessment studies. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2023
Full Text:
Date Issued: 2023-10-13

Quick View

Investigation of brewery waste grains and microbial fuel cells as value-additive technologies improving solvent production yields in Clostridium acetobutylicum (ATCC 824) fermentation

- Du Toit, Ryan Guillaume

Authors: Du Toit, Ryan Guillaume
Date: 2023-10-13
Subjects: Uncatalogued
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/424643 , vital:72171
Description: The production of the solvent compounds acetone, ethanol and butanol through fermentation of organic feedstocks using Clostridia species could be a promising route for biofuel production. However, the cost of raw materials, low yields and the complexity of anaerobic fermentation continue to hinder this means of generating these compounds. The research presented in this Thesis investigated low-cost interventions that could decrease the costs of production and to direct the synthesis of fuel compounds using microbial fuel cells. Low-cost anaerobic chambers were designed and constructed for the propagation and manipulation of Clostridium acetobutylicum, selected as a low-risk microbial catalyst. Fermentation was monitored using in situ pH measurements and a combination of turbidity measurements, nutrient assays (especially total carbohydrates) and HPLC-RI detection as a means of monitoring the consumption of nutrients (glucose), production of precursor compounds (butyric acid) and the formation of solvent molecules (acetone/ethanol and butanol) during fermentation by this organism. Brewer’s spent grains were tested as a sustainable and low-cost feedstock for solvent production, comparing the effects of sterilising before fermentation, or allowing resident microflora to remain during Clostridium-catalysed solvent production. Sterilised spent grains significantly improved the production of solvent molecules (e.g. 12.97 ± 0.38 g/L of butanol yielded, compared to 0.40 ± 0.33 g/L for defined media sampled during the solventogenic phase); compared to these, the use of non-sterilised brewer’s grain decreased both the reproducibility and yields of fermentation (8.66 ± 1.6 g/L of butanol). Microbial fuel cells were studied as a possible means of altering electron transfer to/from electrode-attached Clostridia to control the metabolic shift in bacteria from acidogenesis to solventogenesis. The base line MFC (11.00 ± 4.69 g/L) fermentation experiment did produce higher acetone/ethanol than the baseline batch experiment MB (5.47 ± 4.48 g/L), indicating an improvement to solvent production in C. acetobutylicum (ATCC 824) in a MFC fermentation. In this study, MFC-1 demonstrated remarkable superiority over MB in terms of butyric acid production, yielding significantly higher concentrations while also improving acetone and ethanol production. However, the enhanced butyric acid production did not correspond to significantly increased butanol yields when compared to batch fermentation of chemically defined media. These findings highlight the potential of MFC-1 as an efficient approach for enhancing the fermentative production of valuable compounds, with a particular focus on butyric acid and acetone/ethanol. , Thesis (MSc) -- Faculty of Science, Biotechnology Innovation Centre, 2023
Full Text:
Date Issued: 2023-10-13

Quick View

InVisible freedom fighter: a critical analysis of portrayals of women in archival photographs, independence monuments and contemporary art in Zambia (Northern Rhodesia) and Zimbabwe (Southern Rhodesia)

- Kalichini, Gladys Melina

Authors: Kalichini, Gladys Melina
Date: 2023-10-13
Subjects: Uncatalogued
Language: English
Type: Academic theses , Doctoral theses , text
Identifier: http://hdl.handle.net/10962/432433 , vital:72870 , DOI 10.21504/10962/432433
Description: This doctoral dissertation in art history develops a notion of invisibility by critically analysing processes in which narratives about women are either concealed or uncovered in visual portrayals relating to the independence of Zambia (former Northern Rhodesia) and Zimbabwe (previously Southern Rhodesia). This study concentrates on three main visual categories that include archival photographs, national monuments, and visual art. It critically engages with concepts of memory and history through a framework of gender. The concept of invisibility developed in this thesis articulates a dynamic process in which independence narratives evolve over time, sometimes revealing memories associated with women and at other times rendering women invisible. National liberation in many African states is dominantly accredited to the political parties that were in power at the time of independence. In Zambia, the United National Independence Party (UNIP) is acknowledged for spearheading efforts to overthrow the colonial administration, while in Zimbabwe it is the Zimbabwe African National Union – Patriotic Front (ZANU – PF). Both political parties were headed by men, and the majority of their memberships was also comprised of men; as such, the dominant narratives largely illuminate the stories of men associated with these political parties. The overarching argument of this doctoral dissertation is that there is a gender bias inherent in dominant independence struggles narratives that are communicated through cultural heritage sites such as monuments and archives. In this study, art and art making inform theory as the methodological approach takes the direction in which selected artworks and visual materials are employed as a starting point of considering concepts that relate to the visibilities of stories about women. This approach cogitates the function of art, visual culture, and art history in the production of knowledges that foster in-depth understandings of concepts that explain social phenomena such as historical erasure. This doctoral dissertation in art history is divided into two parts, A and B, that conceptually complement each other. In section A which comprises of chapters one and two, the study develops an alternative visual archive that surveys the involvements of six specific women in the attainment of national independence in their respective countries, and critically analyses the Freedom Statue in Zambia and the National Heroes Acre in Zimbabwe as monuments dedicated to commemorating the independence struggle in the two countries. In Chapters three to five which form the second section of this dissertation, the emphasis of the discussion is on how selected visual artworks of three selected artists disrupt, counter or engage with dominant historical accounts that either exclude or marginalise narratives about women. The three artists include myself, Gladys Kalichini, and Zimbabwean born artists Kudzanai Chiurai and Gresham Tapiwa Nyaude. This thesis offers a culturally rich conversation about visual representations of social, political and cultural roles women performed in the colonial times in Northern and Southern Rhodesia and gives insight into the evolution of the luminosity of contemporary performances of women’s social collectives in Zambia and Zimbabwe. , Thesis (PhD) -- Faculty of Humanities, Fine Art, 2023
Full Text:
Date Issued: 2023-10-13

Quick View

It’s an African proverb: conceptualizing narratives through the use of African subject matter

- Chithambo, N'lamwai Luntha

Authors: Chithambo, N'lamwai Luntha
Date: 2023-10-13
Subjects: Proverbs, African , Oral tradition Africa , Biography in art , Myth in art , Storytelling in art , Comic books, strips, etc. Themes, motives , Mental illness in art
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/425311 , vital:72228
Description: The research by practice is made up of three points of interest that aim to incorporate storytelling into the work with reference to the comic book genre. These points of interest are: experiences of mental health issues from a young man’s perspective, a unique autobiographical experience unpacking the young man’s mental health struggle and African oral traditions. These three points of interest work towards the goal of using African subject matter to uncover and present a meaningful narrative of a young man dealing with mental health problems and his father figure’s ongoing sit-down conversation with him. This mini-thesis breaks down the different components of the research by practice and analyses each component while drawing from various theorists and artists. The mini-thesis also builds up to the idea of using original African subject matter (e.g. African oral traditions, specifically African objects, subjects, and locations) as a means of cultivating a locus of African identity in the comic book industry. The research by practice intersects with this mini-thesis in that it acts as an example of how I visualise African subject matter being used in the theorising and creation of comic books. , Thesis (MFA) -- Faculty of Humanities, Fine Art, 2023
Full Text:
Date Issued: 2023-10-13

Quick View

Jazz pedagogical strategies: an A/R/Tographic investigation into the implementation of the South African jazz CAPS syllabus

- Rungan, Natalie

Authors: Rungan, Natalie
Date: 2023-10-13
Subjects: Uncatalogued
Language: English
Type: Academic theses , Doctoral theses , text
Identifier: http://hdl.handle.net/10962/432488 , vital:72875 , DOI 10.21504/10962/432488
Description: The Jazz stream of the Curriculum and Assessment Policy Statement Further Education and Training music curriculum was introduced in South Africa in 2012 (DBE, 2011a). Despite the intentions of the government to promote diversity, social transformation, and inclusion, subject music is still weighted towards Western Art Music, perpetuating past biases of a Eurocentric model for music education. This study, which uses a mixed-method approach, seeks to create strategies to advance Jazz education in South Africa through an a/r/tographic analysis of the author’s Jazz pedagogical methods at Durban High School in KwaZulu Natal, South Africa. Key approaches include curriculum theory, currere, a/r/tography, among others. After reviewing Jazz pedagogy in the U.S.A. and South Africa as a starting point, using Pinar’s (1994) method of currere, the author demonstrates how past personal music educational processes have led to present Jazz pedagogical methods. Six original compositions were written that outline the influences that infused these methods and added to the creative output related to this research. Interviews were conducted with key stakeholders in the Jazz community to gain perspective about the current state of Jazz education, and with students to provide insight into their reactions to the Jazz stream of CAPS. This presents new information about the curriculum from a learners’ perspective. Ethical clearance for research with children was sought and received (Appendix A). Findings show that the ability of learners to recognise the value in, and identity relating to, their African culture through Jazz points to a pivotal departure from previous Eurocentric music education models. However, despite South Africa being positioned as one of the only countries offering Jazz as a subject choice to high school learners, the selection of Jazz in the subject of Music remains underutilised. This study concludes that for Jazz education to advance in South African high schools, there needs to be intentional engagement with Jazz professionals at the high school level. , Thesis (PhD) -- Faculty of Humanities, Music and Musicology, 2023
Full Text:
Date Issued: 2023-10-13

Quick View

Just stories?: Epistemic (in)justice and everyday resistance in the digital stories of family literacy practices by Grade 1-5 workers at a South African University

- Viedge, Jane Margaret

Authors: Viedge, Jane Margaret
Date: 2023-10-13
Subjects: Uncatalogued
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/432308 , vital:72860
Description: This thesis sets out to establish in what ways digital storytelling (DST) revealed instances of epistemic (in)justices inherent in the family literacy intervention experiences of four Black, working-class parents employed at a South African University1. Additionally, it explores how DST might be used by the participants (self-labelled the Storytelling Family Literacy - SFL Advocates) to correct any harm done. The context for the research is based on the deep-rooted harms of Bantu education in which Black South Africans were denied equal access to resources such as literacy practices. I investigated these aims by using the theories of DST, Communication for Social Change (C4SC) and epistemic (in)justice. As a participatory media practice supporting communications in marginalised communities, DST’s broad purpose is to assist these communities in telling stories of their lived experiences in ways that change dominant and, therefore, unchallenged views about them (Servaes & Malikhao 2014). In facilitating DST workshops with the SFL Advocates, I searched for evidence of epistemic (in)justice to enhance our (all stakeholders) understanding of their literacy experiences in ways that addressed their credibility status as ‘knowers’ (Fricker, 2007). Viewed through this lens, utilising DST provided a mechanism for understanding the impact of social interventions in a university setting that aimed to correct past injustices. The process involved online and face-to-face workshops with the participants during the Covid-19 Lockdown. The online format hampered data collection processes, and I resorted to face-to-face interactions for the workshops and interviews. These interactions were distinctly different from those I had experienced with participants in previous workshops, and they became a key focus in my analysis. Using narrative inquiry with critical realist and interpretive analysis techniques to interrogate the data, I discovered DST has both weaknesses and strengths as a C4SC communication tool. My findings revealed participants who, in the moment of leading their children and communities through the family literacy intervention, could claim to have redressed epistemic harms from the legacy of Apartheid education. However, by reflecting on this moment, the participants brought to light an epistemic harm that had been previously left unspoken: their sense of restored credibility as knowledge-bearers during the intervention was deeply shaken when the programme ended because they felt abandoned by the university. Therefore, the epistemic (in)justice lens unveiled hidden injustices that curtailed the participants’ ability to participate fully in the DST workshops. They described suffering the effects of pernicious and arbitrary acts of epistemic injustice at the hands of the University. Their participation in my workshops was erratic, and their stories were incomplete. As a result, I experienced difficulty analysing what I perceived as a lack of data. Moreover, despite my independent researcher status, my positionality as participant-observer was problematic as the participants may have perceived me as representative of the University and its institutional power. I responded to the problematic data by including a new theoretical framework in my analysis: the theory of everyday resistance (Vinthagen & Johansson, 2013). Combined with epistemic (in)justice theory and Vivienne’s ideas of using DST for everyday activism, I theorised how the participants negotiated their expressions of identity in epistemically unjust spaces. To put institutional epistemic injustice in perspective in the context of the University, I drew on Fricker’s three models of epistemic justice that enable fair and free conditions for marginalised workers to communicate for social change. , Thesis (MA) -- Faculty of Humanities, Journalism and Media Studies, 2023
Full Text:
Date Issued: 2023-10-13

Quick View

Kant and the experience of skepticism: rranscendental arguments, skepticism, and a version of the problem of the justification of foundational assumptions

- Grecia, Hadley

Authors: Grecia, Hadley
Date: 2023-10-13
Subjects: Uncatalogued
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/425078 , vital:72207
Description: Immanuel Kant is a key thinker in the History of Western Philosophy whose ideas continue to fascinate contemporary English-speaking academic philosophers. One such idea is Kant's conception of transcendental arguments. Although these arguments do not originate in Kant's philosophy, Kant's conception of them occupies a special place in the English-speaking literature on the topic. A growing trend in this literature is to claim that Kant's transcendental arguments are unique because they aim to achieve an anti-skeptical end through deductive means. I call the basic assumption behind readings of transcendental arguments like these the deductive/anti-skeptical assumption. This assumption claims that deduction is the best means to achieve an anti-skeptical end. In this thesis, I argue that accepting this assumption is one way to misinterpret transcendental arguments because—even though it seems compelling at first blush—it must be false. The resultant twist is that transcendental arguments cannot be deductive, which, in turn, means that understanding that Kant's transcendental arguments are not deductive in nature is itself no small detail for understanding the version of Kant's 'not-deductive' solution to skepticism developed here. , Thesis (MA) -- Faculty of Humanities, Philosophy, 2023
Full Text:
Date Issued: 2023-10-13

Showing items 181 - 200 of 634