Small steps to equal dignity: the work of the South African equality courts
- Authors: Krüger, Rósaan
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68920 , vital:29339 , http://www.equalrightstrust.org/ertdocumentbank/ERR7_kruger.pdf
- Description: Publisher version , Introduction: “The South African Constitution is primarily and emphatically an egalitarian constitution. The supreme laws of comparable constitutional states may underscore other principles and rights. But in the light of our own particular history, and our vision for the future, a constitution was written with equality at its centre. Equality is our Constitution’s focus and organising principle.” Given the foundational role of equality in the South African constitutional framework, the drafters of the South African Constitution (the Constitution) directed the South African Parliament (Parliament) to enact legislation to “prevent or prohibit unfair discrimination” between individuals within three years of the enactment of the Constitution.3 Under great pressure, Parliament finalised and passed the Promotion of Equality and Prevention of Unfair Discrimination Act (the Equality Act) within two days of the constitutional deadline.4 The Equality Act, as the title indicates, addresses the promotion of equality on the one hand, and provides for reactive measures where the equality right is breached, on the other. The reactive provisions include the prohibition of unfair discrimination and related infringements of the equality right. The Equality Act expressly provides for the enforcement of its provisions in specifically created equality courts. The majority of the reactive provisions of the Equality Act have been operational since 16 June 2003. More than a decade after the enactment of the legislation, the promotional aspects of the Equality Act are yet to come into operation. This article focuses on the reactive provisions of the Equality Act by providing a snapshot of the work of selected South African equality courts for the period from June 2003 to December 2007 insofar as complaints of racism are concerned. In order to contextualise the application of the Equality Act, the article provides a brief overview of the reactive provisions of the Equality Act and the mechanisms for its enforcement.
- Full Text: false
- Authors: Krüger, Rósaan
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68920 , vital:29339 , http://www.equalrightstrust.org/ertdocumentbank/ERR7_kruger.pdf
- Description: Publisher version , Introduction: “The South African Constitution is primarily and emphatically an egalitarian constitution. The supreme laws of comparable constitutional states may underscore other principles and rights. But in the light of our own particular history, and our vision for the future, a constitution was written with equality at its centre. Equality is our Constitution’s focus and organising principle.” Given the foundational role of equality in the South African constitutional framework, the drafters of the South African Constitution (the Constitution) directed the South African Parliament (Parliament) to enact legislation to “prevent or prohibit unfair discrimination” between individuals within three years of the enactment of the Constitution.3 Under great pressure, Parliament finalised and passed the Promotion of Equality and Prevention of Unfair Discrimination Act (the Equality Act) within two days of the constitutional deadline.4 The Equality Act, as the title indicates, addresses the promotion of equality on the one hand, and provides for reactive measures where the equality right is breached, on the other. The reactive provisions include the prohibition of unfair discrimination and related infringements of the equality right. The Equality Act expressly provides for the enforcement of its provisions in specifically created equality courts. The majority of the reactive provisions of the Equality Act have been operational since 16 June 2003. More than a decade after the enactment of the legislation, the promotional aspects of the Equality Act are yet to come into operation. This article focuses on the reactive provisions of the Equality Act by providing a snapshot of the work of selected South African equality courts for the period from June 2003 to December 2007 insofar as complaints of racism are concerned. In order to contextualise the application of the Equality Act, the article provides a brief overview of the reactive provisions of the Equality Act and the mechanisms for its enforcement.
- Full Text: false
SOA driven architectures for service creation through enablers in an IMS testbed
- Tsietsi, Mosiuoa, Terzoli, Alfredo, Wells,George C
- Authors: Tsietsi, Mosiuoa , Terzoli, Alfredo , Wells,George C
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430726 , vital:72711 , https://ieeexplore.ieee.org/abstract/document/6144230
- Description: Standards development organisations have long been in agreement that the most appropriate and cost effective way of developing services for the IP Multimedia Subsystem (IMS) is through the use - and re-use - of service capabilities, which are the building blocks for developing complex services. IMS specifications provide a theoretical framework for how service capabilities can be aggregated into large service appli-cations. However, there is little evidence that mainstream IMS service development is capability-based, and many services are still designed in a monolithic way, with no re-use of existing functionality. Telecom-munication networks are well positioned to stimulate the Internet ser-vices market by exposing these service enablers to third parties. In this paper, we marry the two issues by defining an extended IMS service layer (EISL) that provides a service broker that is the central agent in both service interaction management and the execution of external re-quests from third parties. A prototypical implementation of the service broker is described that was developed using a converged SIP servlet container, and a discussion is also provided that details how third party developers could use HTTP APIs to interact with a service broker in or-der to gain access to network capabilities.
- Full Text:
- Authors: Tsietsi, Mosiuoa , Terzoli, Alfredo , Wells,George C
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430726 , vital:72711 , https://ieeexplore.ieee.org/abstract/document/6144230
- Description: Standards development organisations have long been in agreement that the most appropriate and cost effective way of developing services for the IP Multimedia Subsystem (IMS) is through the use - and re-use - of service capabilities, which are the building blocks for developing complex services. IMS specifications provide a theoretical framework for how service capabilities can be aggregated into large service appli-cations. However, there is little evidence that mainstream IMS service development is capability-based, and many services are still designed in a monolithic way, with no re-use of existing functionality. Telecom-munication networks are well positioned to stimulate the Internet ser-vices market by exposing these service enablers to third parties. In this paper, we marry the two issues by defining an extended IMS service layer (EISL) that provides a service broker that is the central agent in both service interaction management and the execution of external re-quests from third parties. A prototypical implementation of the service broker is described that was developed using a converged SIP servlet container, and a discussion is also provided that details how third party developers could use HTTP APIs to interact with a service broker in or-der to gain access to network capabilities.
- Full Text:
Solid-phase extraction based sample preparation for the determination of drug and organic pollutant residue
- Authors: Pule, Bellah Oreeditse
- Date: 2011 , 2011-02-08
- Subjects: Food contamination , Drugs -- Analysis , Pharmaceutical chemistry , Extraction (Chemistry) , Sorbents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4406 , http://hdl.handle.net/10962/d1006711 , Food contamination , Drugs -- Analysis , Pharmaceutical chemistry , Extraction (Chemistry) , Sorbents
- Description: This thesis presents solid phase extraction (SPE) methodologies based on mixed-mode polymeric sorbents; a mixed mode strong anion exchanger (Agilent SampliQ SAX) and a mixed mode strong cation exchanger (Agilent SampliQ SCX). Furthermore, dispersive-SPE based on a quick, easy, cheap, effective, rugged and safe (QuEChERS) method was assessed for applicability in the determination of drug residues. The mixed-mode polymeric sorbents were evaluated for the simultaneous fractionation of drugs that exhibit diverse polarities with acidic, basic and neutral functionalities in biological matrices (plasma and urine). The polymeric skeleton of these sorbents entails an exchanger group and therefore provides two retention mechanisms, strong cation or anion exchange retention mechanisms with hydrophobic interactions. It was demonstrated that with a sequential elution protocol for sample clean-up analytes were fractionated into acidic, basic and neutral classes. The SAX was employed for analysis of ketoprofen, naproxen (acidic drugs), nortriptyline (basic) and secobarbital (neutral) from urine sample. The SCX was used for fractionating phenobarbital, p-toluamide (acidic), amphetamine, m-toluidine (basic) and acetaminophen (neutral drug) from plasma sample. QuEChERS method was employed for quantitative determination of 16 polycyclic aromatic hydrocarbons (PAHs) from fish fillets and soil; 9 sulfonamides (SAs) from chicken muscles and acrylamide (AA) in cooking oil. The analyte recoveries ranged from 79.6 - 109% with RSDs ranging from 0.06 - 1.9% at three different fortification levels. Good linearity (r2 > 0.9990) was attained for most analytes. The limits of detection and quantification ranged from 0.03 - 0.84 μg/ml and 0.81 - 1.89 μg/ml respectively for analytes in biological samples. LODs and LOQs for analytes in food and environmental samples ranged from 0.02 to 0.39 and 0.25 to 1.30 ng/g respectively.
- Full Text:
- Authors: Pule, Bellah Oreeditse
- Date: 2011 , 2011-02-08
- Subjects: Food contamination , Drugs -- Analysis , Pharmaceutical chemistry , Extraction (Chemistry) , Sorbents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4406 , http://hdl.handle.net/10962/d1006711 , Food contamination , Drugs -- Analysis , Pharmaceutical chemistry , Extraction (Chemistry) , Sorbents
- Description: This thesis presents solid phase extraction (SPE) methodologies based on mixed-mode polymeric sorbents; a mixed mode strong anion exchanger (Agilent SampliQ SAX) and a mixed mode strong cation exchanger (Agilent SampliQ SCX). Furthermore, dispersive-SPE based on a quick, easy, cheap, effective, rugged and safe (QuEChERS) method was assessed for applicability in the determination of drug residues. The mixed-mode polymeric sorbents were evaluated for the simultaneous fractionation of drugs that exhibit diverse polarities with acidic, basic and neutral functionalities in biological matrices (plasma and urine). The polymeric skeleton of these sorbents entails an exchanger group and therefore provides two retention mechanisms, strong cation or anion exchange retention mechanisms with hydrophobic interactions. It was demonstrated that with a sequential elution protocol for sample clean-up analytes were fractionated into acidic, basic and neutral classes. The SAX was employed for analysis of ketoprofen, naproxen (acidic drugs), nortriptyline (basic) and secobarbital (neutral) from urine sample. The SCX was used for fractionating phenobarbital, p-toluamide (acidic), amphetamine, m-toluidine (basic) and acetaminophen (neutral drug) from plasma sample. QuEChERS method was employed for quantitative determination of 16 polycyclic aromatic hydrocarbons (PAHs) from fish fillets and soil; 9 sulfonamides (SAs) from chicken muscles and acrylamide (AA) in cooking oil. The analyte recoveries ranged from 79.6 - 109% with RSDs ranging from 0.06 - 1.9% at three different fortification levels. Good linearity (r2 > 0.9990) was attained for most analytes. The limits of detection and quantification ranged from 0.03 - 0.84 μg/ml and 0.81 - 1.89 μg/ml respectively for analytes in biological samples. LODs and LOQs for analytes in food and environmental samples ranged from 0.02 to 0.39 and 0.25 to 1.30 ng/g respectively.
- Full Text:
Some considerations when comparing SABAP 1 with SABAP 2 data
- Authors: Bonnevie, Bo T
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/448327 , vital:74722 , https://doi.org/10.2989/00306525.2011.603486
- Description: Generally, one should be cautious when comparing data that have not been collected in the same manner. The data collection methods of the South African Bird Atlas Projects, SABAP 1 (Harrison et al. 1997) and SABAP 2 (in progress at the time of writing), differ both spatially and temporally. On the spatial scale SABAP 1 used predominantly quarter degree cells (15′ by 15′), whereas SABAP 2 uses pentads (5′ by 5′; one quarter-degree cell containing nine pentads). On a temporal scale SABAP 1 used one calendar month, whereas SABAP 2 is using one pentade (five days). Where possible, however, SABAP 1 used pentades post hoc for seasonality modelling (Harrison et al. 1997, pp lviii–lix). Because of, but possibly not limited to, this, caution will need to be exercised when comparing data between the two projects. It is naturally desirable to compare the data between these projects, particularly to seek long-term trends in population densities and in the potential changes in the distribution of species.
- Full Text:
- Authors: Bonnevie, Bo T
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/448327 , vital:74722 , https://doi.org/10.2989/00306525.2011.603486
- Description: Generally, one should be cautious when comparing data that have not been collected in the same manner. The data collection methods of the South African Bird Atlas Projects, SABAP 1 (Harrison et al. 1997) and SABAP 2 (in progress at the time of writing), differ both spatially and temporally. On the spatial scale SABAP 1 used predominantly quarter degree cells (15′ by 15′), whereas SABAP 2 uses pentads (5′ by 5′; one quarter-degree cell containing nine pentads). On a temporal scale SABAP 1 used one calendar month, whereas SABAP 2 is using one pentade (five days). Where possible, however, SABAP 1 used pentades post hoc for seasonality modelling (Harrison et al. 1997, pp lviii–lix). Because of, but possibly not limited to, this, caution will need to be exercised when comparing data between the two projects. It is naturally desirable to compare the data between these projects, particularly to seek long-term trends in population densities and in the potential changes in the distribution of species.
- Full Text:
South African money market volatility, asymmetry and retail interest pass-through
- Authors: Fadiran, Gideon Oluwatobi
- Date: 2011
- Subjects: Money market -- South Africa Interest rates -- South Africa Monetary policy -- South Africa Econometric models Banks and banking -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:993 , http://hdl.handle.net/10962/d1002728
- Description: The purpose of this paper is to examine the interest rate transmission mechanism for South Africa as an emerging economy in a pre-repo and repo system. It explains how the money market rate is transmitted to the retail interest rates both in the long-run and short-run and tests the symmetric and asymmetric interest rate pass-through using the Scholnick (1996) ECM and the Wang and Lee (2009) ECM-EGARCH (1, 1)-M methodology. This permitted the examination of the impact of interest rate volatility, along with the leverage effect. An incomplete pass-through is found in the short-run. From the entire sample period, a symmetric adjustment is found in the deposit rate, which had upward rigidity adjustment, while an asymmetric adjustment is found in the lending rate, with a downward rigidity adjustment. All the adjustments supported the collusive pricing arrangements. According to the conditional variance estimation of the ECM-EGARCH (1, 1), negative volatility impact and leverage effect are present and influential only in the deposit interest rate adjustment process in South Africa.
- Full Text:
- Authors: Fadiran, Gideon Oluwatobi
- Date: 2011
- Subjects: Money market -- South Africa Interest rates -- South Africa Monetary policy -- South Africa Econometric models Banks and banking -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:993 , http://hdl.handle.net/10962/d1002728
- Description: The purpose of this paper is to examine the interest rate transmission mechanism for South Africa as an emerging economy in a pre-repo and repo system. It explains how the money market rate is transmitted to the retail interest rates both in the long-run and short-run and tests the symmetric and asymmetric interest rate pass-through using the Scholnick (1996) ECM and the Wang and Lee (2009) ECM-EGARCH (1, 1)-M methodology. This permitted the examination of the impact of interest rate volatility, along with the leverage effect. An incomplete pass-through is found in the short-run. From the entire sample period, a symmetric adjustment is found in the deposit rate, which had upward rigidity adjustment, while an asymmetric adjustment is found in the lending rate, with a downward rigidity adjustment. All the adjustments supported the collusive pricing arrangements. According to the conditional variance estimation of the ECM-EGARCH (1, 1), negative volatility impact and leverage effect are present and influential only in the deposit interest rate adjustment process in South Africa.
- Full Text:
South Africa’s Abortion Values Clarification Workshops: an opportunity to deepen democratic communication missed
- Authors: Vincent, Louise
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/141981 , vital:38021 , DOI: 10.1177/0021909610396161
- Description: A rich literature exists on local democracy and participation in South Africa. While the importance of participation is routinely built into the rhetoric of government, debate has increasingly focused on the dysfunctionality of participatory mechanisms and institutions in post-apartheid South Africa. Processes aimed ostensibly at empowering citizens, act in practice as instruments of social control, disempowerment and cooptation. The present article contributes to these debates by way of a critique of the approach used by the South African state, in partnership with the non-governmental sector, in what are called abortion ‘values clarification’ (VC) workshops. This article examines the workshop materials, methodology and pedagogical tools employed in South African abortion VC workshops which emanate from the organization Ipas — a global body working to enhance women’s sexual and reproductive rights and to reduce abortion-related deaths and injuries. VC workshops represent an instance of a more general trend in which participation is seen as a tool for generating legitimacy and ‘buy-in’ for central state directives rather than as a means for genuinely deepening democratic communication.
- Full Text:
- Authors: Vincent, Louise
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/141981 , vital:38021 , DOI: 10.1177/0021909610396161
- Description: A rich literature exists on local democracy and participation in South Africa. While the importance of participation is routinely built into the rhetoric of government, debate has increasingly focused on the dysfunctionality of participatory mechanisms and institutions in post-apartheid South Africa. Processes aimed ostensibly at empowering citizens, act in practice as instruments of social control, disempowerment and cooptation. The present article contributes to these debates by way of a critique of the approach used by the South African state, in partnership with the non-governmental sector, in what are called abortion ‘values clarification’ (VC) workshops. This article examines the workshop materials, methodology and pedagogical tools employed in South African abortion VC workshops which emanate from the organization Ipas — a global body working to enhance women’s sexual and reproductive rights and to reduce abortion-related deaths and injuries. VC workshops represent an instance of a more general trend in which participation is seen as a tool for generating legitimacy and ‘buy-in’ for central state directives rather than as a means for genuinely deepening democratic communication.
- Full Text:
SphereZyme (TM) technology for enhanced enzyme immobilisation application in biosensors
- Authors: Molawa, Letshego Gloria
- Date: 2011
- Subjects: Immobilized enzymes , Hydrolases , Hydrolysis , SphereZyme , Biosensors , Proteolytic enzymes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3989 , http://hdl.handle.net/10962/d1004048 , Immobilized enzymes , Hydrolases , Hydrolysis , SphereZyme , Biosensors , Proteolytic enzymes
- Description: Self-immobilisation enzyme technologies, such as SphereZyme™, suffer from the lack of applicability to hydrolyse large substrates. Solid support immobilisation is usually a method of choice, to produce a stable biocatalyst for large substrates hydrolysis in the industry. In order to investigate this limitation, a commercial protease called Alcalase® was chosen as a model enzyme due to its natural activity (hydrolysis of large substrates-proteins). Prior to immobilising through the SphereZyme™ technology, Alcalase® was partially purified through dialysis followed by CM Sepharose™ FF cation exchanger. Sample contaminants, such as salts and stabilisers can inhibit protein crosslinking by reacting with glutaraldehyde. Alcalase® was successfully separated into 3 proteases with the major peak correlating to a positive control run on native PAGE, indicating that it was likely subtilisin Carlsberg. A 16% alkaline protease activity for azo-casein hydrolysis was retained when 5% v/v PEI: 25% v/v glutaraldehyde solution was used as a crosslinking agent in Alcalase® SphereZyme™ production. An increase in activity was also observed for monomeric substrates (PNPA) where the highest was 55%. The highest % activities maintained when 0.33 M EDA: 25% v/v glutaraldehyde solution was initially used as crosslinking agent were 4.5% and 1.6% for monomeric and polymeric substrates, respectively. PEI is a hydrophilic branched polymer with an abundance of amine groups compared to EDA. A comparison study of immobilisation efficiencies of SphereZyme™, Eupergit® and Dendrispheres was also performed for large substrate biocatalysis. The two latter technologies are solid-support immobilisation methods. Dendrispheres reached its maximum loading capacity in the first 5 minute of the one hour binding time. Twenty minutes was chosen as a maximum binding time since there was constant protein maintained on the solid support and no enzyme loss was observed during the 1 hour binding time. PEI at pH 11.5, its native pH, gave the highest immobilisation yield and specific activity over the PEI pH range of 11.5 to 7. SphereZyme™ had the highest ratio for azocasein hydrolysis followed by Dendrispheres and Eupergit®. The SphereZyme™ was also shown to be applicable to biosensors for phenol detection. Different modifications of glassy carbon electrode (GCE) were evaluated as a benchmark for the fabrication of SphereZyme™ modified phenol biosensor. GCE modified with laccase SphereZyme™ entrapped in cellulose membrane was the best modification due to the broad catechol range (<0.950 mM), high correlation coefficient (R2, 0.995) and relative high sensitivity factor (0.305 μA.mM-1). This type of biosensor was also shown to be electroactive at pH 7.0 for which its control, free laccase, lacked electroactivity. From the catalytic constants calculated, GCE modified with laccase SphereZyme™ entrapped in cellulose membrane also gave the highest effectiveness factor (Imax/Km app) of 1.84 μA.mM-1. The modified GCE with Alcalase® SphereZyme™ was relatively more sensitive than GCE modified with free Alcalase®.
- Full Text:
- Authors: Molawa, Letshego Gloria
- Date: 2011
- Subjects: Immobilized enzymes , Hydrolases , Hydrolysis , SphereZyme , Biosensors , Proteolytic enzymes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3989 , http://hdl.handle.net/10962/d1004048 , Immobilized enzymes , Hydrolases , Hydrolysis , SphereZyme , Biosensors , Proteolytic enzymes
- Description: Self-immobilisation enzyme technologies, such as SphereZyme™, suffer from the lack of applicability to hydrolyse large substrates. Solid support immobilisation is usually a method of choice, to produce a stable biocatalyst for large substrates hydrolysis in the industry. In order to investigate this limitation, a commercial protease called Alcalase® was chosen as a model enzyme due to its natural activity (hydrolysis of large substrates-proteins). Prior to immobilising through the SphereZyme™ technology, Alcalase® was partially purified through dialysis followed by CM Sepharose™ FF cation exchanger. Sample contaminants, such as salts and stabilisers can inhibit protein crosslinking by reacting with glutaraldehyde. Alcalase® was successfully separated into 3 proteases with the major peak correlating to a positive control run on native PAGE, indicating that it was likely subtilisin Carlsberg. A 16% alkaline protease activity for azo-casein hydrolysis was retained when 5% v/v PEI: 25% v/v glutaraldehyde solution was used as a crosslinking agent in Alcalase® SphereZyme™ production. An increase in activity was also observed for monomeric substrates (PNPA) where the highest was 55%. The highest % activities maintained when 0.33 M EDA: 25% v/v glutaraldehyde solution was initially used as crosslinking agent were 4.5% and 1.6% for monomeric and polymeric substrates, respectively. PEI is a hydrophilic branched polymer with an abundance of amine groups compared to EDA. A comparison study of immobilisation efficiencies of SphereZyme™, Eupergit® and Dendrispheres was also performed for large substrate biocatalysis. The two latter technologies are solid-support immobilisation methods. Dendrispheres reached its maximum loading capacity in the first 5 minute of the one hour binding time. Twenty minutes was chosen as a maximum binding time since there was constant protein maintained on the solid support and no enzyme loss was observed during the 1 hour binding time. PEI at pH 11.5, its native pH, gave the highest immobilisation yield and specific activity over the PEI pH range of 11.5 to 7. SphereZyme™ had the highest ratio for azocasein hydrolysis followed by Dendrispheres and Eupergit®. The SphereZyme™ was also shown to be applicable to biosensors for phenol detection. Different modifications of glassy carbon electrode (GCE) were evaluated as a benchmark for the fabrication of SphereZyme™ modified phenol biosensor. GCE modified with laccase SphereZyme™ entrapped in cellulose membrane was the best modification due to the broad catechol range (<0.950 mM), high correlation coefficient (R2, 0.995) and relative high sensitivity factor (0.305 μA.mM-1). This type of biosensor was also shown to be electroactive at pH 7.0 for which its control, free laccase, lacked electroactivity. From the catalytic constants calculated, GCE modified with laccase SphereZyme™ entrapped in cellulose membrane also gave the highest effectiveness factor (Imax/Km app) of 1.84 μA.mM-1. The modified GCE with Alcalase® SphereZyme™ was relatively more sensitive than GCE modified with free Alcalase®.
- Full Text:
Stable isotope methods: the effect of gut contents on isotopic ratios of zooplankton
- Hill, Jaclyn M, McQuaid, Christopher D
- Authors: Hill, Jaclyn M , McQuaid, Christopher D
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444623 , vital:74255 , https://doi.org/10.1016/j.ecss.2011.02.002
- Description: In the past decade there has been an increased awareness of the potential for methodological bias resulting from multiple pre-analytical procedures in foodweb interpretations based on stable isotope techniques. In the case of small organisms, this includes the effect of gut contents on whole body signatures. Although gut contents may not reflect actual assimilation, their carbon and nitrogen values will be isotopically lighter than after the same material has been assimilated. The potential skewing of isotopic ratios in whole organism samples is especially important for aquatic environments as many studies involve trophic relationships among small zooplankton. This is particularly important in pelagic waters, where herbivorous zooplankton comprise small taxa. Hence this study investigated the effect of gut contents on the δ13C and δ15N ratios of three size classes of zooplankton (1.0–2.0, 2.0–4.0 and >4.0mm) collected using bongo net tows in the tropical waters of the south-west Indian Ocean. Animals were collected at night, when they were likely to be feeding, sieved into size classes and separated into genera. We focused on Euphausia spp which dominated zooplankton biomass. Three treatment types were processed: bulk animals, bulk animals without guts and tail muscle from each size class at 10 bongo stations.
- Full Text:
- Authors: Hill, Jaclyn M , McQuaid, Christopher D
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444623 , vital:74255 , https://doi.org/10.1016/j.ecss.2011.02.002
- Description: In the past decade there has been an increased awareness of the potential for methodological bias resulting from multiple pre-analytical procedures in foodweb interpretations based on stable isotope techniques. In the case of small organisms, this includes the effect of gut contents on whole body signatures. Although gut contents may not reflect actual assimilation, their carbon and nitrogen values will be isotopically lighter than after the same material has been assimilated. The potential skewing of isotopic ratios in whole organism samples is especially important for aquatic environments as many studies involve trophic relationships among small zooplankton. This is particularly important in pelagic waters, where herbivorous zooplankton comprise small taxa. Hence this study investigated the effect of gut contents on the δ13C and δ15N ratios of three size classes of zooplankton (1.0–2.0, 2.0–4.0 and >4.0mm) collected using bongo net tows in the tropical waters of the south-west Indian Ocean. Animals were collected at night, when they were likely to be feeding, sieved into size classes and separated into genera. We focused on Euphausia spp which dominated zooplankton biomass. Three treatment types were processed: bulk animals, bulk animals without guts and tail muscle from each size class at 10 bongo stations.
- Full Text:
Staged authenticities an exploration of the representations of AmaXhosa culture within the main programme of the National Arts Festival, 2009
- Reeve, Zoë Rose Louise Patricia
- Authors: Reeve, Zoë Rose Louise Patricia
- Date: 2011
- Subjects: Standard Bank National Arts Festival Performing arts festivals -- South Africa -- Grahamstown Xhosa (African people) -- Music -- Social aspects Performing arts festivals -- Social aspects -- South Africa -- Grahamstown Cultural property -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2146 , http://hdl.handle.net/10962/d1002378
- Description: This thesis investigates the presentation of AmaXhosa traditional dancing and music on the stages of the National Arts Festival (NAF), Main Programme, of South Africa in 2009. Four productions featuring AmaXhosa traditional dancing and music, as well as a fine art exhibition, are analysed to determine how the AmaXhosa culture is being portrayed, what is considered authentic and how these productions may affect the memory of the AmaXhosa nation. In an attempt to understand the position of these productions within the NAF the South African cultural context as well as the NAF is examined. The post-apartheid, post-rainbow nation, South African cultural context is discussed and how the NAF could contribute towards creating a more unified South African identity. Incorporated and inscribed memory categories are related to how one could determine authenticity in traditional indigenous productions. A cautionary note on incorporated memory is linked to efficacy, while a loss of incorporated memory within the AmaXhosa society may result in ritual acts being orientated towards entertainment. If the private culture is consistently displayed in the public realm then it is inevitable that the ways in which the AmaXhosa recollect their history will be altered. The contribution of the transitional spaces of theatres and proscenium arch stages to the choreography and incorporated memory of the performers relates to the collective recollection of the AmaXhosa. Bearing this in mind, this thesis suggests that the NAF is playing a dual role in the evolution of the AmaXhosa. It is both positively contributing to the economic upliftment of a sector of the population and exposing people to this rich and multilayered culture. However, it is also impacting the efficacy of the private culture and fracturing the traditional knowledge of the AmaXhosa by assisting in the inscription of their performance forms. , This thesis consists of three parts (1 pdf document and two video mp4 files)
- Full Text:
- Authors: Reeve, Zoë Rose Louise Patricia
- Date: 2011
- Subjects: Standard Bank National Arts Festival Performing arts festivals -- South Africa -- Grahamstown Xhosa (African people) -- Music -- Social aspects Performing arts festivals -- Social aspects -- South Africa -- Grahamstown Cultural property -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2146 , http://hdl.handle.net/10962/d1002378
- Description: This thesis investigates the presentation of AmaXhosa traditional dancing and music on the stages of the National Arts Festival (NAF), Main Programme, of South Africa in 2009. Four productions featuring AmaXhosa traditional dancing and music, as well as a fine art exhibition, are analysed to determine how the AmaXhosa culture is being portrayed, what is considered authentic and how these productions may affect the memory of the AmaXhosa nation. In an attempt to understand the position of these productions within the NAF the South African cultural context as well as the NAF is examined. The post-apartheid, post-rainbow nation, South African cultural context is discussed and how the NAF could contribute towards creating a more unified South African identity. Incorporated and inscribed memory categories are related to how one could determine authenticity in traditional indigenous productions. A cautionary note on incorporated memory is linked to efficacy, while a loss of incorporated memory within the AmaXhosa society may result in ritual acts being orientated towards entertainment. If the private culture is consistently displayed in the public realm then it is inevitable that the ways in which the AmaXhosa recollect their history will be altered. The contribution of the transitional spaces of theatres and proscenium arch stages to the choreography and incorporated memory of the performers relates to the collective recollection of the AmaXhosa. Bearing this in mind, this thesis suggests that the NAF is playing a dual role in the evolution of the AmaXhosa. It is both positively contributing to the economic upliftment of a sector of the population and exposing people to this rich and multilayered culture. However, it is also impacting the efficacy of the private culture and fracturing the traditional knowledge of the AmaXhosa by assisting in the inscription of their performance forms. , This thesis consists of three parts (1 pdf document and two video mp4 files)
- Full Text:
Stewardship as an educational process of social learning and change: two case studies conducted in the Western Cape
- Authors: Walker, Clara Isabella
- Date: 2011
- Subjects: Environmental education -- South Africa -- Western Cape Conservation of natural resources -- South Africa -- Western Cape Natural resources -- South Africa -- Western Cape -- Management Social learning -- South Africa -- Western Cape Sustainable development -- South Africa -- Western Cape Cape Nature Stewardship Programme (South Africa) Biodiversity Stewardship Programme (South Africa)
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1772 , http://hdl.handle.net/10962/d1003657
- Description: Stewardship in South Africa, as it is being implemented within the framework of the Biodiversity Stewardship Programme (BSP), is an attempt by conservation agencies to engage landowners in the voluntary securing of parcels of biodiverse land, through signing a contract for a certain time period, not to develop the landscape in ways that will impact negatively on the biodiversity of the area in question. The focus of this study is the relationship between biodiversity stewardship and social learning, as I hope to ascertain how stewardship practices are helping to resolve the current problems of biodiversity loss in the Western Cape. The overall aim of this research is to gain an understanding of how, in its capacity as a conservation education process, the Cape Nature Stewardship Programme can foster social learning amongst the landowners involved in its implementation, by leading them to a better understanding of their environmental responsibilities. Data was generated through the use of interviews and informal discussions with participants together with document analysis, such as brochures, pamphlets and presentations. My approach to the analysis of my data was two-phased. In the first phase, I analysed the data generated from the interview process and from reviewing the documents the stewardship officials supplied me with. The second phase involved looking into the results of the two case studies, and formulating analytical statements which were then used to review the case evidence within a social learning perspective, derived from Wals (2007). In constructing an analytical framework for the interpretation of my data, I drew heavily on Wals' (2007) notion of social learning occurring in sequential activities. I used this insight as a lens through which to trace the educational effects of the implementation of the CNSP in the two case study areas.The research highlighted evidence that Stewardship initiatives should be based on the foundation of social learning and invest time and effort in building an environmental knowledge capital amongst the landowners involved. By equipping them with these necessary conservation skills, one creates a 'community of practice' where those individuals adopt a sustainability habitus contributing towards a change and environmental understanding and practises in field.
- Full Text:
- Authors: Walker, Clara Isabella
- Date: 2011
- Subjects: Environmental education -- South Africa -- Western Cape Conservation of natural resources -- South Africa -- Western Cape Natural resources -- South Africa -- Western Cape -- Management Social learning -- South Africa -- Western Cape Sustainable development -- South Africa -- Western Cape Cape Nature Stewardship Programme (South Africa) Biodiversity Stewardship Programme (South Africa)
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1772 , http://hdl.handle.net/10962/d1003657
- Description: Stewardship in South Africa, as it is being implemented within the framework of the Biodiversity Stewardship Programme (BSP), is an attempt by conservation agencies to engage landowners in the voluntary securing of parcels of biodiverse land, through signing a contract for a certain time period, not to develop the landscape in ways that will impact negatively on the biodiversity of the area in question. The focus of this study is the relationship between biodiversity stewardship and social learning, as I hope to ascertain how stewardship practices are helping to resolve the current problems of biodiversity loss in the Western Cape. The overall aim of this research is to gain an understanding of how, in its capacity as a conservation education process, the Cape Nature Stewardship Programme can foster social learning amongst the landowners involved in its implementation, by leading them to a better understanding of their environmental responsibilities. Data was generated through the use of interviews and informal discussions with participants together with document analysis, such as brochures, pamphlets and presentations. My approach to the analysis of my data was two-phased. In the first phase, I analysed the data generated from the interview process and from reviewing the documents the stewardship officials supplied me with. The second phase involved looking into the results of the two case studies, and formulating analytical statements which were then used to review the case evidence within a social learning perspective, derived from Wals (2007). In constructing an analytical framework for the interpretation of my data, I drew heavily on Wals' (2007) notion of social learning occurring in sequential activities. I used this insight as a lens through which to trace the educational effects of the implementation of the CNSP in the two case study areas.The research highlighted evidence that Stewardship initiatives should be based on the foundation of social learning and invest time and effort in building an environmental knowledge capital amongst the landowners involved. By equipping them with these necessary conservation skills, one creates a 'community of practice' where those individuals adopt a sustainability habitus contributing towards a change and environmental understanding and practises in field.
- Full Text:
Stories from forest, river and mountain : exploring children's cultural environmental narratives and their role in the transmission of cultural connection to and protection of biodiversity
- Authors: Alexander, Jamie Kim
- Date: 2011
- Subjects: Children and the environment -- South Africa -- Eastern Cape , Conservation of natural resources -- South Africa -- Eastern Cape -- Citizen participation , Environmental education -- South Africa -- Eastern Cape , Human ecology -- South Africa -- Eastern Cape , Oral tradition -- South Africa -- Eastern Cape , Social learning -- South Africa -- Eastern Cape , Traditional ecological knowledge -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:6061 , http://hdl.handle.net/10962/d1015267
- Description: Preservationist conservation created a legacy of national parks and protected areas that were surrounded by local people dispossessed of their land and denied the rights to use the resources they had previously relied upon. Although conservation is now shifting towards a more participatory approach, research gaps still exist in determining the meaning of 'the environment' and the role of local means of conservation in rural communities in South Africa. This study focused on children's cultural environmental narratives from two rural villages in the Eastern Cape, South Africa. Children from grades 4, 7 and 10 were involved in the study, and adult family members, local experts and village elders were included in the study to allow for comparison between children's and adult's narratives and to realise what Local Ecological Knowledge (LEK) was being passed on. This thesis considers children's use of the environment for play and their sense of place as key methods in ascertaining children's environmental narratives and perceptions. At both field sites, local experts and community elders possessed a wealth of cultural environmental narratives, but these narratives were not necessarily being passed on. Changing household structures and other socio-economic factors influence cultural environmental practices, which in turn have an impact on the cultural environmental narratives being passed down. In many cases, parents' safety fears strongly impacted upon children's access to the environment, resulting in gendered environmental knowledge. The study compared differing vegetation types and degrees of environmental access. The differing environments produced similar cultural environmental narratives, leading to new understandings in community environment relationships. Children living near the state administered forest had significantly less environmental knowledge, bringing about questions of sustainable bio-cultural diversity in the future. The recognition of cultural environmental values is especially important in the rural areas of South Africa, where unemployment and increased poverty levels have led to greater dependence on natural resources for social, economic and cultural purposes. It is proposed that local cultural environmental narratives and landscape perceptions be included into community conservation and environmental education policies and programmes to provide local solutions to the problem of biodiversity conservation in local contexts.
- Full Text:
- Authors: Alexander, Jamie Kim
- Date: 2011
- Subjects: Children and the environment -- South Africa -- Eastern Cape , Conservation of natural resources -- South Africa -- Eastern Cape -- Citizen participation , Environmental education -- South Africa -- Eastern Cape , Human ecology -- South Africa -- Eastern Cape , Oral tradition -- South Africa -- Eastern Cape , Social learning -- South Africa -- Eastern Cape , Traditional ecological knowledge -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:6061 , http://hdl.handle.net/10962/d1015267
- Description: Preservationist conservation created a legacy of national parks and protected areas that were surrounded by local people dispossessed of their land and denied the rights to use the resources they had previously relied upon. Although conservation is now shifting towards a more participatory approach, research gaps still exist in determining the meaning of 'the environment' and the role of local means of conservation in rural communities in South Africa. This study focused on children's cultural environmental narratives from two rural villages in the Eastern Cape, South Africa. Children from grades 4, 7 and 10 were involved in the study, and adult family members, local experts and village elders were included in the study to allow for comparison between children's and adult's narratives and to realise what Local Ecological Knowledge (LEK) was being passed on. This thesis considers children's use of the environment for play and their sense of place as key methods in ascertaining children's environmental narratives and perceptions. At both field sites, local experts and community elders possessed a wealth of cultural environmental narratives, but these narratives were not necessarily being passed on. Changing household structures and other socio-economic factors influence cultural environmental practices, which in turn have an impact on the cultural environmental narratives being passed down. In many cases, parents' safety fears strongly impacted upon children's access to the environment, resulting in gendered environmental knowledge. The study compared differing vegetation types and degrees of environmental access. The differing environments produced similar cultural environmental narratives, leading to new understandings in community environment relationships. Children living near the state administered forest had significantly less environmental knowledge, bringing about questions of sustainable bio-cultural diversity in the future. The recognition of cultural environmental values is especially important in the rural areas of South Africa, where unemployment and increased poverty levels have led to greater dependence on natural resources for social, economic and cultural purposes. It is proposed that local cultural environmental narratives and landscape perceptions be included into community conservation and environmental education policies and programmes to provide local solutions to the problem of biodiversity conservation in local contexts.
- Full Text:
Structural and functional characterisation of the protein inhibitor of activated STAT3 (PIAS3)
- Authors: Mautsa, Nicodemus
- Date: 2011
- Subjects: Cytokines Immune response Proteins Cancer cells -- Growth -- Regulation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3991 , http://hdl.handle.net/10962/d1004050
- Description: The signal transducer and activator of transcription (STAT) and protein inhibitor of STAT(PIAS) system represent an elegant regulatory mechanism of transcriptional control IN mammalian cytokine signalling. Abnormal activation of the system is associated with immune disorders and a large group of diverse tumours. PIAS3 is a multiple domain protein with distinct functions involved in regulation of cytokine-mediated gene activation pathways.Its over-expression significantly inhibits cell growth and renders cancer cells more sensitive to drugs. The objective of this study was to structurally and biochemically characterise the function of the PIAS3 protein using in silico, in vivo and in vitro analysis approaches.The conservation pattern of the PIAS protein family and critical conserved residues in the PINIT (Proline, Isoleucine, Asparagine, Isoleucine, Tyrosine) domain were identified. The PINIT domain model was generated based on the PINIT domain structure of yeast PIAS3 homologue Siz1 and structural determinants in the PIAS3-STAT3 interaction were evaluated.Guided by the in silico findings, in vivo analysis of the localisation of the PIAS3, mutantderivatives of PIAS3 (PIAS3-L97A, PIAS3-R99N, PIAS3-R99Q), PINIT and acidic domain was conducted. PIAS3 was completely localised in the nucleus while PIAS3 mutants appeared to exhibit diffuse cytoplasmic distribution. The PINIT domain was predominantly localised in the nucleus with some apparent perinuclear staining while the acidic domain exhibited a predominantly perinuclear staining pattern. Further analysis of the PINIT domain and the effect of the mutants on PIAS3-STAT3 interaction were assessed by in vitro analysis. Guided by in silico analysis, the PINIT domain and mutant derivatives of PINIT domain (PINIT-L97A, PINIT-R99N, and PINIT-R99Q) were heterologously expressed in Escherichia coli and subsequently purified using a combination of immobilized metal affinity and size exclusion based chromatography. The size and structural elements of the PINIT domain and its mutants were characterised. The 23 kDa PINIT domain was found to exist as a monomer in solution and its secondary structure was shown to consist of 66 % β-sheets by fourier transformed infrared spectroscopy consistent with the generated homology model.Using surface plasmonresonance spectroscopy (SPR) the PINIT domain was shown to bind to STAT3 in a specific concentration dependent manner. Recombinant PINIT-L97A,PINITR99N and PINIT-R99Q mutants, which exhibited similar structural integrity to the wildtype, were found to abrogate binding to STAT3. These findings suggest that these residues form part of a potential binding surface for stat3. In conclusion, this study has provided evidence that the PINIT domain is an important determinant of PIAS3 interaction with STAT3 and that the interaction is mediated by defined conserved residues directly involved in the PINITSTAT3 interaction.
- Full Text:
- Authors: Mautsa, Nicodemus
- Date: 2011
- Subjects: Cytokines Immune response Proteins Cancer cells -- Growth -- Regulation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3991 , http://hdl.handle.net/10962/d1004050
- Description: The signal transducer and activator of transcription (STAT) and protein inhibitor of STAT(PIAS) system represent an elegant regulatory mechanism of transcriptional control IN mammalian cytokine signalling. Abnormal activation of the system is associated with immune disorders and a large group of diverse tumours. PIAS3 is a multiple domain protein with distinct functions involved in regulation of cytokine-mediated gene activation pathways.Its over-expression significantly inhibits cell growth and renders cancer cells more sensitive to drugs. The objective of this study was to structurally and biochemically characterise the function of the PIAS3 protein using in silico, in vivo and in vitro analysis approaches.The conservation pattern of the PIAS protein family and critical conserved residues in the PINIT (Proline, Isoleucine, Asparagine, Isoleucine, Tyrosine) domain were identified. The PINIT domain model was generated based on the PINIT domain structure of yeast PIAS3 homologue Siz1 and structural determinants in the PIAS3-STAT3 interaction were evaluated.Guided by the in silico findings, in vivo analysis of the localisation of the PIAS3, mutantderivatives of PIAS3 (PIAS3-L97A, PIAS3-R99N, PIAS3-R99Q), PINIT and acidic domain was conducted. PIAS3 was completely localised in the nucleus while PIAS3 mutants appeared to exhibit diffuse cytoplasmic distribution. The PINIT domain was predominantly localised in the nucleus with some apparent perinuclear staining while the acidic domain exhibited a predominantly perinuclear staining pattern. Further analysis of the PINIT domain and the effect of the mutants on PIAS3-STAT3 interaction were assessed by in vitro analysis. Guided by in silico analysis, the PINIT domain and mutant derivatives of PINIT domain (PINIT-L97A, PINIT-R99N, and PINIT-R99Q) were heterologously expressed in Escherichia coli and subsequently purified using a combination of immobilized metal affinity and size exclusion based chromatography. The size and structural elements of the PINIT domain and its mutants were characterised. The 23 kDa PINIT domain was found to exist as a monomer in solution and its secondary structure was shown to consist of 66 % β-sheets by fourier transformed infrared spectroscopy consistent with the generated homology model.Using surface plasmonresonance spectroscopy (SPR) the PINIT domain was shown to bind to STAT3 in a specific concentration dependent manner. Recombinant PINIT-L97A,PINITR99N and PINIT-R99Q mutants, which exhibited similar structural integrity to the wildtype, were found to abrogate binding to STAT3. These findings suggest that these residues form part of a potential binding surface for stat3. In conclusion, this study has provided evidence that the PINIT domain is an important determinant of PIAS3 interaction with STAT3 and that the interaction is mediated by defined conserved residues directly involved in the PINITSTAT3 interaction.
- Full Text:
Studies in marine quinone chemistry
- Authors: Sunassee, Suthananda Naidu
- Date: 2011
- Subjects: Quinone Marine natural products Marine invertebrates Marine pharmacology Cancer -- Treatment
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4355 , http://hdl.handle.net/10962/d1005020
- Description: This thesis is divided into two parts and the rationale of the research conducted is based on the cytotoxicity of the prenylated quinones 1.24-1.29, isolated from the South African nudibranch Leminda millecra, against oesophageal cancer cells. The first part (Chapters 2 and 3) of the thesis initially documents the distribution of cytotoxic and antioxidant prenylated quinones and hydroquinones in the marine environment. We have been able to show, for the first time, that these compounds can be divided into eight structural classes closely related to their phyletic distribution. Secondly, we attempted to synthesize the two marine natural products 1.24 and 1.26 in an effort to contribute to an ongoing collaborative search with the Division of Medical Biochemistry at the University of Cape Town for new compounds with anti-oesophageal cancer activity. Accordingly, we followed the published synthetic procedure for 1.26 and, although we were unable to reproduce the reported results, we have generated five new prenylated quinone analogues 3.53-3.55, 3.63 and 3.71, which are a potentially viable addition to our ongoing structure-activity relationship (SAR) studies. Moreover, we embarked on a 7Li NMR mechanistic study for the synthesis of 3.2 from 3.1 which rewarded us with an improved and reproducible methodology for this crucial reaction that is detailed in Chapter 3. The second part of this thesis (Chapters 4 and 5) is concerned with a synthetic, structural, electrochemical and biological exploration of the 1,4-naphthoquinone nucleus as a primary pharmacophore in our search for new chemical entities which can induce apoptosis in oesophageal cancer cells, thus contributing to our overall ongoing SAR study in this class of compounds. Seven new naphthoquinone derivatves (4.19, 4.30, 4.31, 4.33 and 4.46-4.48) of the natural products 2-deoxylapachol (2.44), lapachol (4.1) and β-lapachone (5.2) were synthesized and 2-(1`-hydroxy-`-phenylmethyl)-1,4-naphthoquinone (4.29) was found to be the most cytotoxic (IC50 1.5 μM) against the oesophageal cancer cell line WHCO1, while 5.2, which is currently in phase II clinical trials as an anticancer drug, was found to be similarly active (IC50 1.6 μM). Electrochemical investigations of the redox properties of the benzylic alcohol derivatives 4.29-4.31 indicated a higher reduction potential compared to their oxidized counterparts 4.45-4.48, and this finding has been correlated to the increased activity of 4.29-4.31 against the WHCO1 cell line. Additionally, 4.29 is synthetically more accessible than either 1.26 or 5.2 and potentially a lead compound in our search for new and more effective chemotherapeutic agents against oesophageal cancer
- Full Text:
- Authors: Sunassee, Suthananda Naidu
- Date: 2011
- Subjects: Quinone Marine natural products Marine invertebrates Marine pharmacology Cancer -- Treatment
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4355 , http://hdl.handle.net/10962/d1005020
- Description: This thesis is divided into two parts and the rationale of the research conducted is based on the cytotoxicity of the prenylated quinones 1.24-1.29, isolated from the South African nudibranch Leminda millecra, against oesophageal cancer cells. The first part (Chapters 2 and 3) of the thesis initially documents the distribution of cytotoxic and antioxidant prenylated quinones and hydroquinones in the marine environment. We have been able to show, for the first time, that these compounds can be divided into eight structural classes closely related to their phyletic distribution. Secondly, we attempted to synthesize the two marine natural products 1.24 and 1.26 in an effort to contribute to an ongoing collaborative search with the Division of Medical Biochemistry at the University of Cape Town for new compounds with anti-oesophageal cancer activity. Accordingly, we followed the published synthetic procedure for 1.26 and, although we were unable to reproduce the reported results, we have generated five new prenylated quinone analogues 3.53-3.55, 3.63 and 3.71, which are a potentially viable addition to our ongoing structure-activity relationship (SAR) studies. Moreover, we embarked on a 7Li NMR mechanistic study for the synthesis of 3.2 from 3.1 which rewarded us with an improved and reproducible methodology for this crucial reaction that is detailed in Chapter 3. The second part of this thesis (Chapters 4 and 5) is concerned with a synthetic, structural, electrochemical and biological exploration of the 1,4-naphthoquinone nucleus as a primary pharmacophore in our search for new chemical entities which can induce apoptosis in oesophageal cancer cells, thus contributing to our overall ongoing SAR study in this class of compounds. Seven new naphthoquinone derivatves (4.19, 4.30, 4.31, 4.33 and 4.46-4.48) of the natural products 2-deoxylapachol (2.44), lapachol (4.1) and β-lapachone (5.2) were synthesized and 2-(1`-hydroxy-`-phenylmethyl)-1,4-naphthoquinone (4.29) was found to be the most cytotoxic (IC50 1.5 μM) against the oesophageal cancer cell line WHCO1, while 5.2, which is currently in phase II clinical trials as an anticancer drug, was found to be similarly active (IC50 1.6 μM). Electrochemical investigations of the redox properties of the benzylic alcohol derivatives 4.29-4.31 indicated a higher reduction potential compared to their oxidized counterparts 4.45-4.48, and this finding has been correlated to the increased activity of 4.29-4.31 against the WHCO1 cell line. Additionally, 4.29 is synthetically more accessible than either 1.26 or 5.2 and potentially a lead compound in our search for new and more effective chemotherapeutic agents against oesophageal cancer
- Full Text:
Studies in South African marine molluscan chemistry
- Authors: Bromley, Candice Leigh
- Date: 2011
- Subjects: Mollusks -- South Africa , Marine invertebrates -- South Africa , Marine metabolites -- South Africa , Chemical oceanography -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4356 , http://hdl.handle.net/10962/d1005021
- Description: This thesis investigates the variability occurring in the secondary metabolites produced by three South African marine molluscs. Chapter Two discusses the isolation and spectroscopic structure elucidation of the metabolites isolated from two Siphonaria species. The re-investigation of Siphonaria capensis yielded siphonarienfuranone (2.2) as the only common polypropionate isolated from both the 1998 and 2009 collections of S. capensis from the same areas suggesting possible seasonal or genetic variation in polypropionate production. The sterol cholest-7-en-3,5,7- triol (2.33) was also isolated form the 2009 collection of S. capensis and this is the first time this compound has been isolated from a Siphonaria species. The second species, Siphonaria oculus is closely related to S. capensis and the investigation into the former’s secondary metaboliteproduction revealed 2.2 as a major metabolite suggesting an inter-species overlap in polypropionate production. Three new polypropionate metabolites, 2.35, 2.36 and 2.37 were also isolated from S. oculus. An unsuccessful attempt was made to establish the absolute configuration of 2.37 using the modified Mosher’s method and the limited amount of 2.37 available prevented any further attempts at resolving the absolute configuration of this compound. The 1H NMR analysis of the defensive mucus collected directly from S. oculus revealed the presence of the acyclic polypropionate 2.37 as a minor metabolite. The absence of characteristic signals for the furanone containing compounds 2.2, 2.35 and 2.36, might suggest that these compounds cyclise from a hypothetical acyclic precursor (2.38) during standard work up of bulk acetone extracts of Siphonaria species. Chapter Three discusses the re-isolation and spectroscopic structure elucidation of the metabolites isolated from the nudibranch, Leminda millecra. Three known natural products, millecrone A (3.1), 8-hydroxycalamenene (3.6) and cubebenone (3.8) were re-isolated from our 2010 collection of L. millecra, as well as the new minor metabolite 8-acetoxycalamenene (3.16). The cytotoxic prenylated toluquinones and toluhydroquinones (3.9-3.15) initially isolated from the 1998 collection of L. millecra were not found in the 2010 collection supporting the hypothesis that these compounds may be of fungal origin. L. millecra clearly shows variability in the compounds sequestered by this species with millecrone A (3.1) being the only common metabolite in the three investigations of L. millecra to date. An unsuccessful attempt was made to establish the absolute configuration of 3.1, 3.6 and 3.8 through initial LAH reduction of the ketone moiety contained in 3.1 and 3.8 and esterification of the resultant diastereomeric alcohol mixtures and the phenol functionality in 3.6 with (1S)-camphanic chloride. Crystallisation of the (S)- camphanate esters of 3.6 and 3.8 for X-ray analysis were unsuccessful, while the unexpected conjugate addition of a hydride in 3.1 resulted in complex diastereomeric mixtures which could not be separated by HPLC.
- Full Text:
- Authors: Bromley, Candice Leigh
- Date: 2011
- Subjects: Mollusks -- South Africa , Marine invertebrates -- South Africa , Marine metabolites -- South Africa , Chemical oceanography -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4356 , http://hdl.handle.net/10962/d1005021
- Description: This thesis investigates the variability occurring in the secondary metabolites produced by three South African marine molluscs. Chapter Two discusses the isolation and spectroscopic structure elucidation of the metabolites isolated from two Siphonaria species. The re-investigation of Siphonaria capensis yielded siphonarienfuranone (2.2) as the only common polypropionate isolated from both the 1998 and 2009 collections of S. capensis from the same areas suggesting possible seasonal or genetic variation in polypropionate production. The sterol cholest-7-en-3,5,7- triol (2.33) was also isolated form the 2009 collection of S. capensis and this is the first time this compound has been isolated from a Siphonaria species. The second species, Siphonaria oculus is closely related to S. capensis and the investigation into the former’s secondary metaboliteproduction revealed 2.2 as a major metabolite suggesting an inter-species overlap in polypropionate production. Three new polypropionate metabolites, 2.35, 2.36 and 2.37 were also isolated from S. oculus. An unsuccessful attempt was made to establish the absolute configuration of 2.37 using the modified Mosher’s method and the limited amount of 2.37 available prevented any further attempts at resolving the absolute configuration of this compound. The 1H NMR analysis of the defensive mucus collected directly from S. oculus revealed the presence of the acyclic polypropionate 2.37 as a minor metabolite. The absence of characteristic signals for the furanone containing compounds 2.2, 2.35 and 2.36, might suggest that these compounds cyclise from a hypothetical acyclic precursor (2.38) during standard work up of bulk acetone extracts of Siphonaria species. Chapter Three discusses the re-isolation and spectroscopic structure elucidation of the metabolites isolated from the nudibranch, Leminda millecra. Three known natural products, millecrone A (3.1), 8-hydroxycalamenene (3.6) and cubebenone (3.8) were re-isolated from our 2010 collection of L. millecra, as well as the new minor metabolite 8-acetoxycalamenene (3.16). The cytotoxic prenylated toluquinones and toluhydroquinones (3.9-3.15) initially isolated from the 1998 collection of L. millecra were not found in the 2010 collection supporting the hypothesis that these compounds may be of fungal origin. L. millecra clearly shows variability in the compounds sequestered by this species with millecrone A (3.1) being the only common metabolite in the three investigations of L. millecra to date. An unsuccessful attempt was made to establish the absolute configuration of 3.1, 3.6 and 3.8 through initial LAH reduction of the ketone moiety contained in 3.1 and 3.8 and esterification of the resultant diastereomeric alcohol mixtures and the phenol functionality in 3.6 with (1S)-camphanic chloride. Crystallisation of the (S)- camphanate esters of 3.6 and 3.8 for X-ray analysis were unsuccessful, while the unexpected conjugate addition of a hydride in 3.1 resulted in complex diastereomeric mixtures which could not be separated by HPLC.
- Full Text:
Study of protein complexes via homology modeling, applied to cysteine proteases and their protein inhibitors:
- Tastan Bishop, Özlem, Kroon, Matthys
- Authors: Tastan Bishop, Özlem , Kroon, Matthys
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/148070 , vital:38707 , DOI: 10.1007/s00894-011-0990-y
- Description: This paper develops and evaluates large-scale calculation of 3D structures of protein complexes by homology modeling as a promising new approach for protein docking. The complexes investigated were papain-like cysteine proteases and their protein inhibitors, which play numerous roles in human and parasitic metabolisms. The structural modeling was performed in two parts. For the first part (evaluation set), nine crystal structure complexes were selected, 1325 homology models of known complexes were rebuilt by various templates including hybrids, allowing an analysis of the factors influencing the accuracy of the models. The important considerations for modeling the interface were protease coverage and inhibitor sequence identity. In the second part (study set), the findings of the evaluation set were used to select appropriate templates to model novel cysteine protease-inhibitor complexes from human and malaria parasites Plasmodium falciparum and Plasmodium vivax. The energy scores, considering the evaluation set, indicate that the models are of high accuracy.
- Full Text:
- Authors: Tastan Bishop, Özlem , Kroon, Matthys
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/148070 , vital:38707 , DOI: 10.1007/s00894-011-0990-y
- Description: This paper develops and evaluates large-scale calculation of 3D structures of protein complexes by homology modeling as a promising new approach for protein docking. The complexes investigated were papain-like cysteine proteases and their protein inhibitors, which play numerous roles in human and parasitic metabolisms. The structural modeling was performed in two parts. For the first part (evaluation set), nine crystal structure complexes were selected, 1325 homology models of known complexes were rebuilt by various templates including hybrids, allowing an analysis of the factors influencing the accuracy of the models. The important considerations for modeling the interface were protease coverage and inhibitor sequence identity. In the second part (study set), the findings of the evaluation set were used to select appropriate templates to model novel cysteine protease-inhibitor complexes from human and malaria parasites Plasmodium falciparum and Plasmodium vivax. The energy scores, considering the evaluation set, indicate that the models are of high accuracy.
- Full Text:
Study South Africa
- International Education Association of South Africa (IEASA), Jooste, Nico
- Authors: International Education Association of South Africa (IEASA) , Jooste, Nico
- Date: 2011
- Subjects: Education, Higher -- South Africa , Universities and colleges -- South Africa , Technical Institutes -- South Africa , Vocational guidance -- South Africa
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/64952 , vital:28639 , ISBN 9780620512244
- Description: [Extract from article by Ms Merle Hodges]: Over the past year there have been numerous conferences dealing with one general topic. How is it possible for higher education, globally, to produce the same quality in its graduates, research and community outreach when the financial resources entering into the system are radically declining? The conclusion is overwhelmingly despondent. ‘Universities have to do more with less, academics and academic research will increasingly be pressurised by lower salaries internally and career temptations from the corporate world – the impact of which is the greater commodification of universities, and the inevitable decline in academic freedom.’ This global negativity is predicated on inter–related factors. The first, the long tail of the economic recession, is continuing to bite all sectors and higher education is no exception. Secondly, higher education is a little like marketing – when the pressure is on government, sectors like higher education are de–prioritised. In light of this, the position of internationalisation in higher education might seem to fade into the background. Interestingly, the inverse is true. While the zeitgeist of higher education generally appears dismal, the prospects of internationalisation appear rosy in comparison. I believe this is true because of two overlapping issues. Firstly, students are not going to give up on university because of a lingering economic downturn. What they are doing, however, is deciding to travel and study at destinations that would have been perceived as implausible a few years ago. Venezuela, Chile, South Korea and South Africa are all drawing US students more than ever before. This is partly because, I sense, the quality of qualifications is achieving parity across the globe; and also, because students who are prepared to travel realise that cultural specificity – the ability to learn new and unique aspects of a different culture while gaining the same core ingredients of a degree – sets it apart from the degree gained locally. A one semester course in Russian anthropology might appear entirely redundant when applying for a job. However, the very interconnectedness of global business means not only that the course is never a waste of time, but that it might mean the difference between landing a contract and failing to do so. The international student has the benefit of developing in ways that traditional (home-grown) higher education may not yet fully understand. Secondly, development in South Africa at least, has an additional meaning. Our universities are not only focused on developing graduates for multicultural or global competitiveness. Over the past five or so years our universities have been focused on development of the country itself. As an emerging power, the impetus has been on creating universities that address the fundamental needs of the people. Poverty, HIV, sustainability and innovative solutions to global problems are the very sap of South African universities in the 21st Century. How to create a sustainable environment, how to preserve marine and wildlife, how to create jobs, reduce poverty, and maximise innovation – these are the concerns that are preoccupying the minds of the country’s best academics. , 11th Edition
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- Authors: International Education Association of South Africa (IEASA) , Jooste, Nico
- Date: 2011
- Subjects: Education, Higher -- South Africa , Universities and colleges -- South Africa , Technical Institutes -- South Africa , Vocational guidance -- South Africa
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/64952 , vital:28639 , ISBN 9780620512244
- Description: [Extract from article by Ms Merle Hodges]: Over the past year there have been numerous conferences dealing with one general topic. How is it possible for higher education, globally, to produce the same quality in its graduates, research and community outreach when the financial resources entering into the system are radically declining? The conclusion is overwhelmingly despondent. ‘Universities have to do more with less, academics and academic research will increasingly be pressurised by lower salaries internally and career temptations from the corporate world – the impact of which is the greater commodification of universities, and the inevitable decline in academic freedom.’ This global negativity is predicated on inter–related factors. The first, the long tail of the economic recession, is continuing to bite all sectors and higher education is no exception. Secondly, higher education is a little like marketing – when the pressure is on government, sectors like higher education are de–prioritised. In light of this, the position of internationalisation in higher education might seem to fade into the background. Interestingly, the inverse is true. While the zeitgeist of higher education generally appears dismal, the prospects of internationalisation appear rosy in comparison. I believe this is true because of two overlapping issues. Firstly, students are not going to give up on university because of a lingering economic downturn. What they are doing, however, is deciding to travel and study at destinations that would have been perceived as implausible a few years ago. Venezuela, Chile, South Korea and South Africa are all drawing US students more than ever before. This is partly because, I sense, the quality of qualifications is achieving parity across the globe; and also, because students who are prepared to travel realise that cultural specificity – the ability to learn new and unique aspects of a different culture while gaining the same core ingredients of a degree – sets it apart from the degree gained locally. A one semester course in Russian anthropology might appear entirely redundant when applying for a job. However, the very interconnectedness of global business means not only that the course is never a waste of time, but that it might mean the difference between landing a contract and failing to do so. The international student has the benefit of developing in ways that traditional (home-grown) higher education may not yet fully understand. Secondly, development in South Africa at least, has an additional meaning. Our universities are not only focused on developing graduates for multicultural or global competitiveness. Over the past five or so years our universities have been focused on development of the country itself. As an emerging power, the impetus has been on creating universities that address the fundamental needs of the people. Poverty, HIV, sustainability and innovative solutions to global problems are the very sap of South African universities in the 21st Century. How to create a sustainable environment, how to preserve marine and wildlife, how to create jobs, reduce poverty, and maximise innovation – these are the concerns that are preoccupying the minds of the country’s best academics. , 11th Edition
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Surface properties and electrocatalytic applications of metallophthalocyanines confined on electrode surfaces
- Authors: Akinbulu, Isaac Adebayo
- Date: 2011
- Subjects: Phthalocyanines Electrochemistry Electrocatalysis Pesticides
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4365 , http://hdl.handle.net/10962/d1005030
- Description: New cobalt (13, 16 19 and 22), manganese (14, 17, 20 and 23) and iron (15, 18, 21 and 24)phthalocyanine complexes were synthesized and characterized. The UV-Vis spectral properties of the complexes were typical of the nature of central metal and position of substituent on the Pc ligand. Their electrochemical behaviors were signatures of the central metals, with varying influences of the nature and position of substituents. Nanocomposite of complex 18 and single walled carbon nanotubes (SWCNTs) (SWCNT-18)was fabricated. Formation of this nano-composite was confirmed by infrared (IR)spectroscopy, X-ray diffraction (XRD) spectroscopy and transmission electron microscopy (TEM). Self-assembled monolayers (SAMs) of SWCNT-18, complexes 13-15, and 20 were electropolymerized on glassy carbon electrodes (GCE). Complex 14 was also electrodeposited on GCE. Surface properties of the SAMs were consistent with the molecular feature of the substituent and the nature of central metal in the adsorbed species, while those of the MnPc modified GCEs were dependent on point of substitution and number of substituent. The SAM-modified gold electrodes were used for the electrocatalytic oxidation of the carbamate insecticide, carbofuran. Amplification of the current signal of the insecticide, at more energetically feasible oxidation potentials, on the SAM-modified gold electrodes, relative to bare gold electrode,justified electrocatalysis. There was enhanced sensitivity (attributed to the presence of SWCNT) of the SWCNT-18-SAM-modified gold electrode towards carbofuran, relative to the signals observed on the other SAMs. Current response of the insecticide,bendiocarb, was also intensified, at more favorable oxidation potentials, on the MnPc (14 and 17) modified GCEs, relative to the response on bare GCE, substantiating electrocatalysis. Also, catalysis of the oxidation of the herbicide, bentazon, was observed on polymeric film of complex 20. The current response of the herbicide on this film was better than that observed on bare GCE. Electrocatalysis of the analytes, on the respective modified electrodes, occurred via closely related mechanisms.
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- Authors: Akinbulu, Isaac Adebayo
- Date: 2011
- Subjects: Phthalocyanines Electrochemistry Electrocatalysis Pesticides
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4365 , http://hdl.handle.net/10962/d1005030
- Description: New cobalt (13, 16 19 and 22), manganese (14, 17, 20 and 23) and iron (15, 18, 21 and 24)phthalocyanine complexes were synthesized and characterized. The UV-Vis spectral properties of the complexes were typical of the nature of central metal and position of substituent on the Pc ligand. Their electrochemical behaviors were signatures of the central metals, with varying influences of the nature and position of substituents. Nanocomposite of complex 18 and single walled carbon nanotubes (SWCNTs) (SWCNT-18)was fabricated. Formation of this nano-composite was confirmed by infrared (IR)spectroscopy, X-ray diffraction (XRD) spectroscopy and transmission electron microscopy (TEM). Self-assembled monolayers (SAMs) of SWCNT-18, complexes 13-15, and 20 were electropolymerized on glassy carbon electrodes (GCE). Complex 14 was also electrodeposited on GCE. Surface properties of the SAMs were consistent with the molecular feature of the substituent and the nature of central metal in the adsorbed species, while those of the MnPc modified GCEs were dependent on point of substitution and number of substituent. The SAM-modified gold electrodes were used for the electrocatalytic oxidation of the carbamate insecticide, carbofuran. Amplification of the current signal of the insecticide, at more energetically feasible oxidation potentials, on the SAM-modified gold electrodes, relative to bare gold electrode,justified electrocatalysis. There was enhanced sensitivity (attributed to the presence of SWCNT) of the SWCNT-18-SAM-modified gold electrode towards carbofuran, relative to the signals observed on the other SAMs. Current response of the insecticide,bendiocarb, was also intensified, at more favorable oxidation potentials, on the MnPc (14 and 17) modified GCEs, relative to the response on bare GCE, substantiating electrocatalysis. Also, catalysis of the oxidation of the herbicide, bentazon, was observed on polymeric film of complex 20. The current response of the herbicide on this film was better than that observed on bare GCE. Electrocatalysis of the analytes, on the respective modified electrodes, occurred via closely related mechanisms.
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Syntheses and electrochemical characterization of new water soluble octaarylthiosubstituted manganese phthalocyanines
- Booysen, Irvin N, Matemadombo, Fungisai, Durmus, Mahmut, Nyokong, Tebello
- Authors: Booysen, Irvin N , Matemadombo, Fungisai , Durmus, Mahmut , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247614 , vital:51600 , xlink:href="https://doi.org/10.1016/j.dyepig.2010.09.012"
- Description: This paper reports on the synthesis and characterization of new manganese phthalocyanine (MnPc) complexes: 2,3-octakis-[(2-mercaptopyridine) phthalocyaninato] acetato manganese (III) (1) and its quaternized (hence water soluble) derivative: 2,3-octakis-{[(N-methyl-2-mercaptopyridine) phthalocyaninato] acetato manganese (III)} sulphate (2). The complexes were used to form self assembled monolayers (SAMs). Voltammetry proved that both of the SAMs are well packed, strongly passivating and act as selective and efficient barriers to ion permeability. Furthermore, surface coverage studies confirmed that the MPc macrocycles adsorb onto the gold electrode as monolayers. Both MPc SAMs were successfully used as electrochemical sensors of nitrite.
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- Authors: Booysen, Irvin N , Matemadombo, Fungisai , Durmus, Mahmut , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247614 , vital:51600 , xlink:href="https://doi.org/10.1016/j.dyepig.2010.09.012"
- Description: This paper reports on the synthesis and characterization of new manganese phthalocyanine (MnPc) complexes: 2,3-octakis-[(2-mercaptopyridine) phthalocyaninato] acetato manganese (III) (1) and its quaternized (hence water soluble) derivative: 2,3-octakis-{[(N-methyl-2-mercaptopyridine) phthalocyaninato] acetato manganese (III)} sulphate (2). The complexes were used to form self assembled monolayers (SAMs). Voltammetry proved that both of the SAMs are well packed, strongly passivating and act as selective and efficient barriers to ion permeability. Furthermore, surface coverage studies confirmed that the MPc macrocycles adsorb onto the gold electrode as monolayers. Both MPc SAMs were successfully used as electrochemical sensors of nitrite.
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Syntheses, electrochemical and spectroelectrochemical properties of novel ball-type and mononuclear Co (II) phthalocyanines substituted at the peripheral and non-peripheral positions with binaphthol groups
- Canlıca, Mevlüde, Booysen, Irvin Noel, Nyokong, Tebello
- Authors: Canlıca, Mevlüde , Booysen, Irvin Noel , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247837 , vital:51622 , xlink:href="https://doi.org/10.1016/j.poly.2010.11.017"
- Description: Mononuclear cobalt phthalocyanine (CoPc) substituted at the non-peripheral 8 and peripheral positions 9 with 1,1′-binaphthyl-8,8′-diol and ball-type dinuclear Co2Pc2 substituted at the non-peripheral 10 and peripheral 11 positions with the same substituent are reported. The complexes with 1,1′-binaphthol-bridges were prepared from the corresponding phthalonitriles 4–7. The effects of the position of substituent on spectral, electrochemical and spectroelectrochemical properties of these complexes were also explored. The mononuclear complexes 8 and 9 exhibited one metal reduction, one ring reduction and one ring oxidation. The redox properties of the ball-type complexes 10 and 11 exhibited two reduction processes assigned to [(CoIPc−2)2]2−/[(CoIPc−3)2]4− (I), (CoIIPc−2)2/[(CoIPc−2)2]2− (II) and one oxidation process assigned to [(CoIIIPc−2)2]2+/CoIIPc−2)2 (III). The ball-type complexes are much easier to oxidize and more difficult to reduce than the corresponding monomers 8 and 9.
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- Authors: Canlıca, Mevlüde , Booysen, Irvin Noel , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247837 , vital:51622 , xlink:href="https://doi.org/10.1016/j.poly.2010.11.017"
- Description: Mononuclear cobalt phthalocyanine (CoPc) substituted at the non-peripheral 8 and peripheral positions 9 with 1,1′-binaphthyl-8,8′-diol and ball-type dinuclear Co2Pc2 substituted at the non-peripheral 10 and peripheral 11 positions with the same substituent are reported. The complexes with 1,1′-binaphthol-bridges were prepared from the corresponding phthalonitriles 4–7. The effects of the position of substituent on spectral, electrochemical and spectroelectrochemical properties of these complexes were also explored. The mononuclear complexes 8 and 9 exhibited one metal reduction, one ring reduction and one ring oxidation. The redox properties of the ball-type complexes 10 and 11 exhibited two reduction processes assigned to [(CoIPc−2)2]2−/[(CoIPc−3)2]4− (I), (CoIIPc−2)2/[(CoIPc−2)2]2− (II) and one oxidation process assigned to [(CoIIIPc−2)2]2+/CoIIPc−2)2 (III). The ball-type complexes are much easier to oxidize and more difficult to reduce than the corresponding monomers 8 and 9.
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Synthesis and electrocatalytic behavior of cobalt (II)-tris (benzyl-mercapto)-monoaminophthalocyanine–single walled carbon nanotube nanorods
- Mugadza, Tawanda, Nyokong, Tebello
- Authors: Mugadza, Tawanda , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247882 , vital:51626 , xlink:href="https://doi.org/10.1016/j.electacta.2010.11.016"
- Description: In this paper we report on synthesis and electrocatalytic behavior of cobalt (II)-tris(benzyl-mercapto)-monoaminophthalocyanine–single walled carbon nanotube nanorods towards the oxidation of amitrole. SWCNTs that were terminally functionalized with carboxylic acid groups were chemically linked to cobalt (II)-tris(benzyl-mercapto) monoaminophthalocyanine (CoMAPc) via an amide bond to form nanorods. UV–vis, FTIR, TEM, Raman and XRD spectroscopies were used in characterization of the nanorods (CoMAPc–SWCNT-linked), while cyclic voltammetry and chronoamperometry were used during the characterization of amitrole on the modified glassy carbon electrode. The linear dynamic range for the amitrole was from 1.0 × 10−6 M to 1.2 × 10−4 M, with a sensitivity of 6.76 A mol−1 L cm−2. The estimated limit of detection for amitrole was 0.10 μM, using the 3δ criterion. The catalytic rate constant was found to be 1.09 × 105 M−1 s−1.
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- Authors: Mugadza, Tawanda , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247882 , vital:51626 , xlink:href="https://doi.org/10.1016/j.electacta.2010.11.016"
- Description: In this paper we report on synthesis and electrocatalytic behavior of cobalt (II)-tris(benzyl-mercapto)-monoaminophthalocyanine–single walled carbon nanotube nanorods towards the oxidation of amitrole. SWCNTs that were terminally functionalized with carboxylic acid groups were chemically linked to cobalt (II)-tris(benzyl-mercapto) monoaminophthalocyanine (CoMAPc) via an amide bond to form nanorods. UV–vis, FTIR, TEM, Raman and XRD spectroscopies were used in characterization of the nanorods (CoMAPc–SWCNT-linked), while cyclic voltammetry and chronoamperometry were used during the characterization of amitrole on the modified glassy carbon electrode. The linear dynamic range for the amitrole was from 1.0 × 10−6 M to 1.2 × 10−4 M, with a sensitivity of 6.76 A mol−1 L cm−2. The estimated limit of detection for amitrole was 0.10 μM, using the 3δ criterion. The catalytic rate constant was found to be 1.09 × 105 M−1 s−1.
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