Meso-and axially-modified IrIIItriarylcorroles with tunable electrocatalytic properties
- Zhang, Xifeng, Wang, Yu, Zhu, Weihua, Mack, John, Soy, Rodah C, Nyokong, Tebello, Liang, Xu
- Authors: Zhang, Xifeng , Wang, Yu , Zhu, Weihua , Mack, John , Soy, Rodah C , Nyokong, Tebello , Liang, Xu
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190851 , vital:45034 , xlink:href="https://doi.org/10.1016/j.molstruc.2015.02.040"
- Description: The synthesis of three A2B type Ir(III)triarylcorroles with meso-aryl substituents that provide electron donating (push) and withdrawing (pull) properties and three A3 type IrIIItriphenylcorroles with differing pyridine axial ligands is reported, along with their structural characterization. An analysis of the structure-property relationships in the optical and redox properties has been carried out by comparing their optical spectroscopy and electrochemistry to trends predicted in DFT and TD-DFT calculations. The results demonstrate that A2B type IrIIItriarylcorroles are highly efficient electrocatalyzed oxygen reduction reactions (ORRs) and that their reactivity can be modulated by modulating the electronic structure by changing the nature of the meso-substituent at the B-positions, and even axial pyridine ligands.
- Full Text:
- Date Issued: 2015
- Authors: Zhang, Xifeng , Wang, Yu , Zhu, Weihua , Mack, John , Soy, Rodah C , Nyokong, Tebello , Liang, Xu
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190851 , vital:45034 , xlink:href="https://doi.org/10.1016/j.molstruc.2015.02.040"
- Description: The synthesis of three A2B type Ir(III)triarylcorroles with meso-aryl substituents that provide electron donating (push) and withdrawing (pull) properties and three A3 type IrIIItriphenylcorroles with differing pyridine axial ligands is reported, along with their structural characterization. An analysis of the structure-property relationships in the optical and redox properties has been carried out by comparing their optical spectroscopy and electrochemistry to trends predicted in DFT and TD-DFT calculations. The results demonstrate that A2B type IrIIItriarylcorroles are highly efficient electrocatalyzed oxygen reduction reactions (ORRs) and that their reactivity can be modulated by modulating the electronic structure by changing the nature of the meso-substituent at the B-positions, and even axial pyridine ligands.
- Full Text:
- Date Issued: 2015
Mitochondrial STAT3 and reactive oxygen species: a fulcrum of adipogenesis?
- Kramer, Adam H, Kadye, Rose, Houseman, Pascalene S, Prinsloo, Earl
- Authors: Kramer, Adam H , Kadye, Rose , Houseman, Pascalene S , Prinsloo, Earl
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431674 , vital:72795 , xlink:href="https://doi.org/10.1080/21623996.2015.1084084"
- Description: The balance between cellular lineages can be controlled by reactive oxygen species (ROS). Cellular differentiation into adipocytes is highly dependent on the production of ROS to initiate the process through activation of multiple interlinked factors that stimulate mitotic clonal expansion and cellular maturation. The signal transducer and activator of transcription family of signaling proteins have accepted roles in adipogenesis and associated lipogenesis. Non-canonical mitochondrial localization of STAT3 and other members of the STAT family however opens up new avenues for investigation of its role in the aforementioned processes. Following recent observations of differences in mitochondrially localized serine 727 phosphorylated STAT3 (mtSTAT3-pS727) in preadipocytes and adipocytes, here, we hypothesize and speculate further on the role of mitochondrial STAT3 in adipogenesis.
- Full Text:
- Date Issued: 2015
- Authors: Kramer, Adam H , Kadye, Rose , Houseman, Pascalene S , Prinsloo, Earl
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431674 , vital:72795 , xlink:href="https://doi.org/10.1080/21623996.2015.1084084"
- Description: The balance between cellular lineages can be controlled by reactive oxygen species (ROS). Cellular differentiation into adipocytes is highly dependent on the production of ROS to initiate the process through activation of multiple interlinked factors that stimulate mitotic clonal expansion and cellular maturation. The signal transducer and activator of transcription family of signaling proteins have accepted roles in adipogenesis and associated lipogenesis. Non-canonical mitochondrial localization of STAT3 and other members of the STAT family however opens up new avenues for investigation of its role in the aforementioned processes. Following recent observations of differences in mitochondrially localized serine 727 phosphorylated STAT3 (mtSTAT3-pS727) in preadipocytes and adipocytes, here, we hypothesize and speculate further on the role of mitochondrial STAT3 in adipogenesis.
- Full Text:
- Date Issued: 2015
Modelling stock return volatility dynamics in selected African markets
- Authors: King, Daniel , Botha, Ferdi
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/396104 , vital:69150 , xlink:href=" https://doi.org/10.1016/j.econmod.2014.11.008"
- Description: This paper examines whether accounting for structural changes in the conditional variance process, through the use of Markov-switching models, improves estimates and forecasts of stock return volatility over those of the more conventional single-state (G)ARCH models, within and across selected African markets for the period 2002–2012. In the univariate portion of the paper, the performances of various Markov-switching models are tested against a single-state benchmark model through the use of in-sample goodness-of-fit and predictive ability measures. In the multivariate context, the single-state and Markov-switching models are comparatively assessed according to their usefulness in constructing optimal stock portfolios. Accounting for structural breaks in the conditional variance process, conventional GARCH effects remain important in capturing heteroscedasticity. However, those univariate models including a GARCH term perform comparatively poorly when used for forecasting purposes. In the multivariate study, the use of Markov-switching variance–covariance estimates improves risk-adjusted portfolio returns relative to portfolios constructed using the more conventional single-state models. While there is evidence that some Markov-switching models can provide better forecasts and higher risk-adjusted returns than those models which include GARCH effects, the inability of the simpler Markov-switching models to fully capture heteroscedasticity in the data remains problematic.
- Full Text:
- Date Issued: 2015
- Authors: King, Daniel , Botha, Ferdi
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/396104 , vital:69150 , xlink:href=" https://doi.org/10.1016/j.econmod.2014.11.008"
- Description: This paper examines whether accounting for structural changes in the conditional variance process, through the use of Markov-switching models, improves estimates and forecasts of stock return volatility over those of the more conventional single-state (G)ARCH models, within and across selected African markets for the period 2002–2012. In the univariate portion of the paper, the performances of various Markov-switching models are tested against a single-state benchmark model through the use of in-sample goodness-of-fit and predictive ability measures. In the multivariate context, the single-state and Markov-switching models are comparatively assessed according to their usefulness in constructing optimal stock portfolios. Accounting for structural breaks in the conditional variance process, conventional GARCH effects remain important in capturing heteroscedasticity. However, those univariate models including a GARCH term perform comparatively poorly when used for forecasting purposes. In the multivariate study, the use of Markov-switching variance–covariance estimates improves risk-adjusted portfolio returns relative to portfolios constructed using the more conventional single-state models. While there is evidence that some Markov-switching models can provide better forecasts and higher risk-adjusted returns than those models which include GARCH effects, the inability of the simpler Markov-switching models to fully capture heteroscedasticity in the data remains problematic.
- Full Text:
- Date Issued: 2015
Multiple benefits and values of trees in urban landscapes in two towns in northern South Africa
- Shackleton, Sheona E, Chinyimba, Abby, Hebinck, Paul, Shackleton, Charlie M, Kaoma, Humphrey
- Authors: Shackleton, Sheona E , Chinyimba, Abby , Hebinck, Paul , Shackleton, Charlie M , Kaoma, Humphrey
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180874 , vital:43658 , xlink:href="https://doi.org/10.1016/j.landurbplan.2014.12.004"
- Description: Cities and towns can be conceptualised as complex social-ecological systems or landscapes that are composed of different spatial elements. Trees in urban landscapes provide a variety of tangible and intangible benefits (ecosystem services) that may be valued differently across diverse households and individuals. Here, we consider how the benefits and values of trees to urban residents vary across public and private spaces in three low income neighbourhoods in two medium-sized towns in northern South Africa. We find that the most asset poor residents in informal settlements derive significant benefits from the provisioning services offered by trees in natural green spaces on the ‘urban periphery’; in particular they value supplies of wood for energy, whilst also recognising the importance of regulating services such as shade. Trees in such spaces help these immigrants cope with a lack of infrastructure, services and disposable income after their move to the city. In new, low-cost housing neighbourhoods, the importance of trees in providing shade and shelter in gardens is emphasised due to the hot and dusty nature of these settlements, while residents in older township neighbourhoods make more mention of the aesthetic value of trees in private spaces as well as the fruits they provide. In all neighbourhoods, attitudes towards trees in public spaces were mixed because of their perceived association with crime, although low income households did make extensive use of tree products from natural areas. The relevance of the results for urban planning and greening in low income areas is discussed.
- Full Text:
- Date Issued: 2015
- Authors: Shackleton, Sheona E , Chinyimba, Abby , Hebinck, Paul , Shackleton, Charlie M , Kaoma, Humphrey
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180874 , vital:43658 , xlink:href="https://doi.org/10.1016/j.landurbplan.2014.12.004"
- Description: Cities and towns can be conceptualised as complex social-ecological systems or landscapes that are composed of different spatial elements. Trees in urban landscapes provide a variety of tangible and intangible benefits (ecosystem services) that may be valued differently across diverse households and individuals. Here, we consider how the benefits and values of trees to urban residents vary across public and private spaces in three low income neighbourhoods in two medium-sized towns in northern South Africa. We find that the most asset poor residents in informal settlements derive significant benefits from the provisioning services offered by trees in natural green spaces on the ‘urban periphery’; in particular they value supplies of wood for energy, whilst also recognising the importance of regulating services such as shade. Trees in such spaces help these immigrants cope with a lack of infrastructure, services and disposable income after their move to the city. In new, low-cost housing neighbourhoods, the importance of trees in providing shade and shelter in gardens is emphasised due to the hot and dusty nature of these settlements, while residents in older township neighbourhoods make more mention of the aesthetic value of trees in private spaces as well as the fruits they provide. In all neighbourhoods, attitudes towards trees in public spaces were mixed because of their perceived association with crime, although low income households did make extensive use of tree products from natural areas. The relevance of the results for urban planning and greening in low income areas is discussed.
- Full Text:
- Date Issued: 2015
Nanosecond nonlinear optical limiting properties of new trinuclear lanthanide phthalocyanines in solution and as thin films
- Sekhosana, Kutloana E, Amuhaya, Edith K, Nyokong, Tebello
- Authors: Sekhosana, Kutloana E , Amuhaya, Edith K , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189752 , vital:44928 , xlink:href="https://doi.org/10.1016/j.poly.2014.08.047"
- Description: 2,4,6-Tris[3-thio-9,10,16,17,23,24-hexa(4-tertbutylphenoxy) phthalocyaninato ytterbium (III) chloride]-s-triazin (3) and its lutetium counterpart (4) were synthesized. The nonlinear optical behavior of 3 and 4 were characterized in solution and when embedded in polymer as thin films. Thin films of complexes 3 and 4 in poly(bisphenol A carbonate) showed improved nonlinear optical properties when compared to solution. Complex 3 showed a lower threshold for optical limiting intensity (Ilim) than complex 4, and for phthalocyanines in general. Ilim values were even lower in films compared to solutions.
- Full Text:
- Date Issued: 2015
- Authors: Sekhosana, Kutloana E , Amuhaya, Edith K , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189752 , vital:44928 , xlink:href="https://doi.org/10.1016/j.poly.2014.08.047"
- Description: 2,4,6-Tris[3-thio-9,10,16,17,23,24-hexa(4-tertbutylphenoxy) phthalocyaninato ytterbium (III) chloride]-s-triazin (3) and its lutetium counterpart (4) were synthesized. The nonlinear optical behavior of 3 and 4 were characterized in solution and when embedded in polymer as thin films. Thin films of complexes 3 and 4 in poly(bisphenol A carbonate) showed improved nonlinear optical properties when compared to solution. Complex 3 showed a lower threshold for optical limiting intensity (Ilim) than complex 4, and for phthalocyanines in general. Ilim values were even lower in films compared to solutions.
- Full Text:
- Date Issued: 2015
Optical properties of water-soluble L-cysteine-capped alloyed CdSeS quantum dot passivated with ZnSeTe and ZnSeTe/ZnS shells
- Adegoke, Oluwasesan, Nyokong, Tebello, Forbes, Patricia B C
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B C
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193609 , vital:45352 , xlink:href="https://doi.org/10.1016/j.optmat.2015.05.024"
- Description: Alloyed quantum dots (QDs) passivated with shell materials have valuable optical characteristics suitable for a wide array of applications. In this work, alloyed ternary CdSeS QDs passivated with ZnSeTe and ZnSeTe/ZnS shells have been synthesized via a hot-injection method and a ligand exchange reaction employing L-cysteine as a thiol ligand has been used to obtain these water-soluble nanocrystals for the first time. The photoluminescence (PL) quantum yield (QY) of alloyed L-cysteine-capped CdSeS was 71.2% but decreased significantly to 5.2% upon passivation with a ZnSeTe shell. The red shift in PL emission of the CdSeS/ZnSeTe QDs was attributed to be strain-induced whilst a lattice-induced process likely created defect states in the core/shell interface hence contributing to the decline in the PL QY. Nonetheless, the fluorescence stability of CdSeS/ZnSeTe QDs in aqueous solution was unperturbed. Further passivation with a ZnS shell (CdSeS/ZnSeTe/ZnS) improved the PL QY to a value of 58.7% and thus indicates that the defect state in the QDs core/shell/shell structure was reduced. PL lifetime exciton measurements indicated that the rates of decay of the QDs influenced their photophysical properties.
- Full Text:
- Date Issued: 2015
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B C
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193609 , vital:45352 , xlink:href="https://doi.org/10.1016/j.optmat.2015.05.024"
- Description: Alloyed quantum dots (QDs) passivated with shell materials have valuable optical characteristics suitable for a wide array of applications. In this work, alloyed ternary CdSeS QDs passivated with ZnSeTe and ZnSeTe/ZnS shells have been synthesized via a hot-injection method and a ligand exchange reaction employing L-cysteine as a thiol ligand has been used to obtain these water-soluble nanocrystals for the first time. The photoluminescence (PL) quantum yield (QY) of alloyed L-cysteine-capped CdSeS was 71.2% but decreased significantly to 5.2% upon passivation with a ZnSeTe shell. The red shift in PL emission of the CdSeS/ZnSeTe QDs was attributed to be strain-induced whilst a lattice-induced process likely created defect states in the core/shell interface hence contributing to the decline in the PL QY. Nonetheless, the fluorescence stability of CdSeS/ZnSeTe QDs in aqueous solution was unperturbed. Further passivation with a ZnS shell (CdSeS/ZnSeTe/ZnS) improved the PL QY to a value of 58.7% and thus indicates that the defect state in the QDs core/shell/shell structure was reduced. PL lifetime exciton measurements indicated that the rates of decay of the QDs influenced their photophysical properties.
- Full Text:
- Date Issued: 2015
Optimisation of an electrochemical impedance spectroscopy aptasensor by exploiting quartz crystal microbalance with dissipation signals
- Formisanoa, Nello, Jolly, Pawan, Bhalla, Nikhil, Cromhout, Mary, Flanagan, Shane P, Fogel, Ronen, Limson, Janice L, Estrela, Pedro
- Authors: Formisanoa, Nello , Jolly, Pawan , Bhalla, Nikhil , Cromhout, Mary , Flanagan, Shane P , Fogel, Ronen , Limson, Janice L , Estrela, Pedro
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431699 , vital:72797 , xlink:href="https://doi.org/10.1016/j.snb.2015.05.049"
- Description: The response of an Electrochemical Impedance Spectroscopy (EIS) sensor using DNA aptamers is affected by many factors, such as DNA density, charge and conformational changes upon DNA-target binding, and buffer conditions. We report here for the first time on the optimisation of an EIS aptamer-based sensor by using Quartz Crystal Microbalance with Dissipation mode (QCM-D). As a case study, we employed a DNA aptamer against Prostate-Specific Antigen (PSA). PSA detection was achieved by functionalising the gold sensor surface via thiol chemistry with different ratios of thiolated-DNA aptamer and 6-mercapto-1-hexanol (MCH) used as spacer molecules. PSA binding efficiency can be monitored by measuring QCM-D signals which not only provide information about the mass of PSA bound on the sensor surface, but also crucial information about the aptamer conformation and layer hydration.
- Full Text:
- Date Issued: 2015
- Authors: Formisanoa, Nello , Jolly, Pawan , Bhalla, Nikhil , Cromhout, Mary , Flanagan, Shane P , Fogel, Ronen , Limson, Janice L , Estrela, Pedro
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431699 , vital:72797 , xlink:href="https://doi.org/10.1016/j.snb.2015.05.049"
- Description: The response of an Electrochemical Impedance Spectroscopy (EIS) sensor using DNA aptamers is affected by many factors, such as DNA density, charge and conformational changes upon DNA-target binding, and buffer conditions. We report here for the first time on the optimisation of an EIS aptamer-based sensor by using Quartz Crystal Microbalance with Dissipation mode (QCM-D). As a case study, we employed a DNA aptamer against Prostate-Specific Antigen (PSA). PSA detection was achieved by functionalising the gold sensor surface via thiol chemistry with different ratios of thiolated-DNA aptamer and 6-mercapto-1-hexanol (MCH) used as spacer molecules. PSA binding efficiency can be monitored by measuring QCM-D signals which not only provide information about the mass of PSA bound on the sensor surface, but also crucial information about the aptamer conformation and layer hydration.
- Full Text:
- Date Issued: 2015
Organosilicon compounds as fluorescent chemosensors for fluoride anion recognition
- Gai, Lizhi, Mack, John, Lu, Hua, Nyokong, Tebello, Li, Zhifang, Kobayashi, Nagao, Shen, Zhen
- Authors: Gai, Lizhi , Mack, John , Lu, Hua , Nyokong, Tebello , Li, Zhifang , Kobayashi, Nagao , Shen, Zhen
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241424 , vital:50938 , xlink:href="https://doi.org/10.1016/j.ccr.2014.10.009"
- Description: Recent developments in organosilicon-based chemosensors for F− recognition are reviewed. The design strategies for improving the photophysical properties of organosilicon-based chemosensors are elaborated, with an emphasis placed on their utility for biological applications. The photophysical properties and electronic structures are analyzed in depth with reference made to the results of molecular modeling calculation and possible future research directions are assessed.
- Full Text:
- Date Issued: 2015
- Authors: Gai, Lizhi , Mack, John , Lu, Hua , Nyokong, Tebello , Li, Zhifang , Kobayashi, Nagao , Shen, Zhen
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241424 , vital:50938 , xlink:href="https://doi.org/10.1016/j.ccr.2014.10.009"
- Description: Recent developments in organosilicon-based chemosensors for F− recognition are reviewed. The design strategies for improving the photophysical properties of organosilicon-based chemosensors are elaborated, with an emphasis placed on their utility for biological applications. The photophysical properties and electronic structures are analyzed in depth with reference made to the results of molecular modeling calculation and possible future research directions are assessed.
- Full Text:
- Date Issued: 2015
Overexpression, Purification and Characterisation of the Plasmodium falciparum Hsp70-z (PfHsp70-z) Protein
- Zininga, Tawanda, Achilonu, Ikechukwu, Hoppe, Heinrich C, Prinsloo, Earl, Dirr, Heinrich W, Shonhai, Addmore
- Authors: Zininga, Tawanda , Achilonu, Ikechukwu , Hoppe, Heinrich C , Prinsloo, Earl , Dirr, Heinrich W , Shonhai, Addmore
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431719 , vital:72799 , xlink:href="https://doi.org/10.1371/journal.pone.0129445"
- Description: Six Hsp70-like genes are represented on the genome of Plasmodium falciparum. Of these two occur in the cytosol: P. falciparum Hsp70-z (PfHsp70-z) and PfHsp70-1. PfHsp70-1 is a well characterised canonical Hsp70 that facilitates protein quality control and is crucial for the development of malaria parasites. There is very little known about PfHsp70-z. However, PfHsp70-z is known to be essential and is implicated in suppressing aggregation of asparagine-rich proteins of P. falciparum. In addition, its expression at the clinical stage of malaria correlates with disease prognosis. Based on structural evidence PfHsp70-z belongs to the Hsp110 family of proteins. Since Hsp110 proteins have been described as nucleotide exchange factors (NEFs) of their canonical Hsp70 counterparts, it has been speculated that PfHsp70-z may serve as a NEF of PfHsp70-1. In the current study, P. falciparum cells cultured in vitro were subjected to heat stress, triggering the enhanced expression of PfHsp70-z. Biochemical assays conducted using recombinant PfHsp70-z protein demonstrated that the protein is heat stable and possesses ATPase activity. Furthermore, we observed that PfHsp70-z is capable of self-association. The structural-functional features of PfHsp70-z provide further evidence for its role as a chaperone and possible nucleotide exchange factor of PfHsp70-1.
- Full Text:
- Date Issued: 2015
- Authors: Zininga, Tawanda , Achilonu, Ikechukwu , Hoppe, Heinrich C , Prinsloo, Earl , Dirr, Heinrich W , Shonhai, Addmore
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431719 , vital:72799 , xlink:href="https://doi.org/10.1371/journal.pone.0129445"
- Description: Six Hsp70-like genes are represented on the genome of Plasmodium falciparum. Of these two occur in the cytosol: P. falciparum Hsp70-z (PfHsp70-z) and PfHsp70-1. PfHsp70-1 is a well characterised canonical Hsp70 that facilitates protein quality control and is crucial for the development of malaria parasites. There is very little known about PfHsp70-z. However, PfHsp70-z is known to be essential and is implicated in suppressing aggregation of asparagine-rich proteins of P. falciparum. In addition, its expression at the clinical stage of malaria correlates with disease prognosis. Based on structural evidence PfHsp70-z belongs to the Hsp110 family of proteins. Since Hsp110 proteins have been described as nucleotide exchange factors (NEFs) of their canonical Hsp70 counterparts, it has been speculated that PfHsp70-z may serve as a NEF of PfHsp70-1. In the current study, P. falciparum cells cultured in vitro were subjected to heat stress, triggering the enhanced expression of PfHsp70-z. Biochemical assays conducted using recombinant PfHsp70-z protein demonstrated that the protein is heat stable and possesses ATPase activity. Furthermore, we observed that PfHsp70-z is capable of self-association. The structural-functional features of PfHsp70-z provide further evidence for its role as a chaperone and possible nucleotide exchange factor of PfHsp70-1.
- Full Text:
- Date Issued: 2015
PFB0595w is a Plasmodium falciparum J protein that co-localizes with PfHsp70-1 and can stimulate its in vitro ATP hydrolysis activity
- Njunge, James M, Mandal, Pradipta, Przyborski, Jude M, Boshoff, Aileen, Pesce, Eva-Rachele, Blatch, Gregory L
- Authors: Njunge, James M , Mandal, Pradipta , Przyborski, Jude M , Boshoff, Aileen , Pesce, Eva-Rachele , Blatch, Gregory L
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431739 , vital:72800 , xlink:href="https://doi.org/10.1016/j.biocel.2015.02.008"
- Description: Heat shock proteins, many of which function as molecular chaperones, play important roles in the lifecycle and pathogenesis of the malaria parasite, Plasmodium falciparum. The P. falciparum heat shock protein 70 (PfHsp70) family of chaperones is potentially regulated by a large complement of J proteins that localize to various intracellular compartments including the infected erythrocyte cytosol. While PfHsp70-1 has been shown to be an abundant cytosolic chaperone, its regulation by J proteins is poorly understood. In this study, we characterized the J protein PFB0595w, a homologue of the well-studied yeast cytosolic J protein, Sis1. PFB0595w, similarly to PfHsp70-1, was localized to the parasite cytosol and its expression was upregulated by heat shock. Additionally, recombinant PFB0595w was shown to be dimeric and to stimulate the in vitro ATPase activity of PfHsp70-1. Overall, the expression, localization and biochemical data for PFB0595w suggest that it may function as a cochaperone of PfHsp70-1, and advances current knowledge on the chaperone machinery of the parasite.
- Full Text:
- Date Issued: 2015
- Authors: Njunge, James M , Mandal, Pradipta , Przyborski, Jude M , Boshoff, Aileen , Pesce, Eva-Rachele , Blatch, Gregory L
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431739 , vital:72800 , xlink:href="https://doi.org/10.1016/j.biocel.2015.02.008"
- Description: Heat shock proteins, many of which function as molecular chaperones, play important roles in the lifecycle and pathogenesis of the malaria parasite, Plasmodium falciparum. The P. falciparum heat shock protein 70 (PfHsp70) family of chaperones is potentially regulated by a large complement of J proteins that localize to various intracellular compartments including the infected erythrocyte cytosol. While PfHsp70-1 has been shown to be an abundant cytosolic chaperone, its regulation by J proteins is poorly understood. In this study, we characterized the J protein PFB0595w, a homologue of the well-studied yeast cytosolic J protein, Sis1. PFB0595w, similarly to PfHsp70-1, was localized to the parasite cytosol and its expression was upregulated by heat shock. Additionally, recombinant PFB0595w was shown to be dimeric and to stimulate the in vitro ATPase activity of PfHsp70-1. Overall, the expression, localization and biochemical data for PFB0595w suggest that it may function as a cochaperone of PfHsp70-1, and advances current knowledge on the chaperone machinery of the parasite.
- Full Text:
- Date Issued: 2015
Photocatalytic behaviour of zinc tetraamino phthalocyanine-silver nanoparticles immobilized on chitosan beads
- Khoza, Phindile, Nyokong, Tebello
- Authors: Khoza, Phindile , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189468 , vital:44849 , xlink:href="https://doi.org/10.1016/j.molcata.2015.01.017"
- Description: Photocatalytic degradation of Rhodamine 6G using unconjugated zinc tetraamino phthalocyanine (ZnTAPc) or when conjugated to Ag nanoparticles (ZnTAPc–AgNPs) is reported. Upon conjugating ZnTAPc to silver nanoparticles, the singlet oxygen production of the phthalocyanine was slightly increased. ZnTAPc and ZnTAPc–AgNPs were immobilized onto chitosan beads for ease of recovery after photocatalysis. Chitosan beads were characterized by FTIR, XRD and TGA. The photodegradation of Rhodamine 6G was used to evaluate the efficiency of the immobilized photocatalysts. In the presence of AgNPs, the photodegradation of Rhodamine 6G was enhanced. The apparent rates (k) were found to be 8.51 × 10−8 and 1.61 × 10−7 mol L−1 min−1 for chitosan supported ZnTAPc or ZnTAPc–AgNPs, respectively. The observation of good photocatalytic activity of the ZnTAPc when immobilized on chitosan proves the uncompromised efficiency of the photocatalysts even when confined in beads, showing great potential for the functionalized beads as heterogeneous catalysts.
- Full Text:
- Date Issued: 2015
- Authors: Khoza, Phindile , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189468 , vital:44849 , xlink:href="https://doi.org/10.1016/j.molcata.2015.01.017"
- Description: Photocatalytic degradation of Rhodamine 6G using unconjugated zinc tetraamino phthalocyanine (ZnTAPc) or when conjugated to Ag nanoparticles (ZnTAPc–AgNPs) is reported. Upon conjugating ZnTAPc to silver nanoparticles, the singlet oxygen production of the phthalocyanine was slightly increased. ZnTAPc and ZnTAPc–AgNPs were immobilized onto chitosan beads for ease of recovery after photocatalysis. Chitosan beads were characterized by FTIR, XRD and TGA. The photodegradation of Rhodamine 6G was used to evaluate the efficiency of the immobilized photocatalysts. In the presence of AgNPs, the photodegradation of Rhodamine 6G was enhanced. The apparent rates (k) were found to be 8.51 × 10−8 and 1.61 × 10−7 mol L−1 min−1 for chitosan supported ZnTAPc or ZnTAPc–AgNPs, respectively. The observation of good photocatalytic activity of the ZnTAPc when immobilized on chitosan proves the uncompromised efficiency of the photocatalysts even when confined in beads, showing great potential for the functionalized beads as heterogeneous catalysts.
- Full Text:
- Date Issued: 2015
Photodynamic antimicrobial chemotherapy activity of (5, 10, 15, 20-tetrakis (4-(4-carboxyphenycarbonoimidoyl) phenyl) porphyrinato) chloro gallium (III)
- Managa, Muthumuni, Amuhaya, Edith K, Nyokong, Tebello
- Authors: Managa, Muthumuni , Amuhaya, Edith K , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189043 , vital:44811 , xlink:href="https://doi.org/10.1016/j.saa.2015.06.088"
- Description: (5,10,15,20-Tetrakis(4-(4-carboxyphenycarbonoimidoyl)phenyl)porphyrinato) chloro gallium(III) (complex 1) was conjugated to platinum nanoparticles (PtNPs) (represented as 1-PtNPs). The resulting conjugate showed 18 nm red shift in the Soret band when compared to 1 alone. Complex 1 and 1-PtNPs showed promising photodynamic antimicrobial chemotherapy (PACT) activity against Staphylococcus aureus, Escherichia coli and Candida albicans in solution where the log reductions obtained were 4.92, 3.76, and 3.95, respectively for 1-PtNPs. The singlet oxygen quantum yields obtained were higher at 0.56 for 1-PtNPs in DMF while that of 1 was 0.52 in the same solvent. This resulted in improved PACT activity for 1-PtNPs compared to 1 alone.
- Full Text:
- Date Issued: 2015
- Authors: Managa, Muthumuni , Amuhaya, Edith K , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189043 , vital:44811 , xlink:href="https://doi.org/10.1016/j.saa.2015.06.088"
- Description: (5,10,15,20-Tetrakis(4-(4-carboxyphenycarbonoimidoyl)phenyl)porphyrinato) chloro gallium(III) (complex 1) was conjugated to platinum nanoparticles (PtNPs) (represented as 1-PtNPs). The resulting conjugate showed 18 nm red shift in the Soret band when compared to 1 alone. Complex 1 and 1-PtNPs showed promising photodynamic antimicrobial chemotherapy (PACT) activity against Staphylococcus aureus, Escherichia coli and Candida albicans in solution where the log reductions obtained were 4.92, 3.76, and 3.95, respectively for 1-PtNPs. The singlet oxygen quantum yields obtained were higher at 0.56 for 1-PtNPs in DMF while that of 1 was 0.52 in the same solvent. This resulted in improved PACT activity for 1-PtNPs compared to 1 alone.
- Full Text:
- Date Issued: 2015
Photodynamic antimicrobial chemotherapy activity of gallium tetra-(4-carboxyphenyl) porphyrin when conjugated to differently shaped platinum nanoparticles
- Managa, Muthumuni, Nyokong, Tebello
- Authors: Managa, Muthumuni , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189088 , vital:44815 , xlink:href="https://doi.org/10.1016/j.molstruc.2015.06.077"
- Description: This work reports on the conjugation of differently shaped Pt nanoparticles (PtNPs) with ClGa(III) 5,10,15,20-tetrakis-(4-carboxyphenyl) porphyrin (ClGaTCPP). The resulting conjugates were used for photodynamic antimicrobial chemotherapy against Staphylococcus aureus. The degree of photoinactivation is dependent on concentration of the conjugates, light dose (fluence) and illumination time. The log reduction obtained for ClGaTCPP when conjugated to cubic PtNPs was 4.64 log (which indicate 99.99% of the bacteria have been killed), which is much higher than 3.94 log unit for ClGaTCPPHexagonal PtNPs and 3.31 log units for ClGaTCPP-Unshaped PtNPs. ClGaTCPP alone gave a log unit reduction of less than 3, showing the importance of conjugation to PtNPs.
- Full Text:
- Date Issued: 2015
- Authors: Managa, Muthumuni , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189088 , vital:44815 , xlink:href="https://doi.org/10.1016/j.molstruc.2015.06.077"
- Description: This work reports on the conjugation of differently shaped Pt nanoparticles (PtNPs) with ClGa(III) 5,10,15,20-tetrakis-(4-carboxyphenyl) porphyrin (ClGaTCPP). The resulting conjugates were used for photodynamic antimicrobial chemotherapy against Staphylococcus aureus. The degree of photoinactivation is dependent on concentration of the conjugates, light dose (fluence) and illumination time. The log reduction obtained for ClGaTCPP when conjugated to cubic PtNPs was 4.64 log (which indicate 99.99% of the bacteria have been killed), which is much higher than 3.94 log unit for ClGaTCPPHexagonal PtNPs and 3.31 log units for ClGaTCPP-Unshaped PtNPs. ClGaTCPP alone gave a log unit reduction of less than 3, showing the importance of conjugation to PtNPs.
- Full Text:
- Date Issued: 2015
Photodynamic therapy effect of zinc monoamino phthalocyanine–folic acid conjugate adsorbed on single walled carbon nanotubes on melanoma cells
- Ogbodu, Racheal O, Ndhundhuma, Ivy, Karstten, Aletta, Nyokong, Tebello
- Authors: Ogbodu, Racheal O , Ndhundhuma, Ivy , Karstten, Aletta , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241400 , vital:50936 , xlink:href="https://doi.org/10.1016/j.saa.2014.09.033"
- Description: This work reports on the photodynamic therapy effect of zinc monoamino phthalocyanine linked to folic acid represented as ZnMAPc-FA, which was further immobilized onto single walled carbon nanotube represented as ZnMAPc-FA-SWCNT on melanoma A375 cell line, the effect of SWCNT-FA (without ZnMAPc) was also examined. All the compounds were non-toxic to the melanoma A375 cell line in the absence of light. Upon irradiation of the melanoma A375 cell line with a 676 nm diode laser at a power density of 98 mW/cm2 at 5 J/cm2 about 60% and 63% cell death was observed in the presence of ZnMAPc-FA and ZnMAPc-FA-SWCNT respectively. SWCNT-FA had no significant photodynamic therapy or photothermal effect to the cell, only 23% of cell death was observed after irradiation.
- Full Text:
- Date Issued: 2015
- Authors: Ogbodu, Racheal O , Ndhundhuma, Ivy , Karstten, Aletta , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241400 , vital:50936 , xlink:href="https://doi.org/10.1016/j.saa.2014.09.033"
- Description: This work reports on the photodynamic therapy effect of zinc monoamino phthalocyanine linked to folic acid represented as ZnMAPc-FA, which was further immobilized onto single walled carbon nanotube represented as ZnMAPc-FA-SWCNT on melanoma A375 cell line, the effect of SWCNT-FA (without ZnMAPc) was also examined. All the compounds were non-toxic to the melanoma A375 cell line in the absence of light. Upon irradiation of the melanoma A375 cell line with a 676 nm diode laser at a power density of 98 mW/cm2 at 5 J/cm2 about 60% and 63% cell death was observed in the presence of ZnMAPc-FA and ZnMAPc-FA-SWCNT respectively. SWCNT-FA had no significant photodynamic therapy or photothermal effect to the cell, only 23% of cell death was observed after irradiation.
- Full Text:
- Date Issued: 2015
Photoinactivation of Candida albicans and Escherichia coli using aluminium phthalocyanine on gold nanoparticles
- Mthethwa, Thandekile, Nyokong, Tebello
- Authors: Mthethwa, Thandekile , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189854 , vital:44940 , xlink:href="https://doi.org/10.1039/C4PP00315B"
- Description: The conjugates of aluminium phthalocyanine (complex 1) with gold nanorods (complex 1–AuNRs) and bipyramids (complex 1–AuBPs) showed improved singlet oxygen quantum yields of 0.23 and 0.24, respectively, compared to that of complex 1 alone at 0.12. Complex 1 and its conjugates were used for the photoinactivation of fungi (C. albicans) and bacteria cells (E. coli). The Q band absorbances were the same for the Pc alone and when conjugated to AuNPs. The efficiency of these conjugates was evaluated by measuring the log reduction of the microorganisms (C. albicans and E. coli) after irradiation with visible light in the presence of photosensitizers. Aluminium phthalocyanine alone showed log 1.78 and log 2.51 reductions for C. albicans and E. coli respectively. However, the conjugates showed higher photosensitization with log 2.08 and log 3.34 for C. albicans and E. coli, respectively using 1–AuBPs. For complex 1–AuNRs log 2.53 and log 3.71 were achieved for C. albicans and E. coli respectively. The statistical analysis of the results showed that the enhanced photoinactivation observed in both microorganisms was irrespective of the shape of the nanoparticles conjugated. Photoinactivation of C. albicans was less than that of E. coli even though a higher concentration of complex 1 or its conjugates was used in C. albicans.
- Full Text:
- Date Issued: 2015
- Authors: Mthethwa, Thandekile , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189854 , vital:44940 , xlink:href="https://doi.org/10.1039/C4PP00315B"
- Description: The conjugates of aluminium phthalocyanine (complex 1) with gold nanorods (complex 1–AuNRs) and bipyramids (complex 1–AuBPs) showed improved singlet oxygen quantum yields of 0.23 and 0.24, respectively, compared to that of complex 1 alone at 0.12. Complex 1 and its conjugates were used for the photoinactivation of fungi (C. albicans) and bacteria cells (E. coli). The Q band absorbances were the same for the Pc alone and when conjugated to AuNPs. The efficiency of these conjugates was evaluated by measuring the log reduction of the microorganisms (C. albicans and E. coli) after irradiation with visible light in the presence of photosensitizers. Aluminium phthalocyanine alone showed log 1.78 and log 2.51 reductions for C. albicans and E. coli respectively. However, the conjugates showed higher photosensitization with log 2.08 and log 3.34 for C. albicans and E. coli, respectively using 1–AuBPs. For complex 1–AuNRs log 2.53 and log 3.71 were achieved for C. albicans and E. coli respectively. The statistical analysis of the results showed that the enhanced photoinactivation observed in both microorganisms was irrespective of the shape of the nanoparticles conjugated. Photoinactivation of C. albicans was less than that of E. coli even though a higher concentration of complex 1 or its conjugates was used in C. albicans.
- Full Text:
- Date Issued: 2015
Photophysical and nonlinear optical studies of tetraakynyl zincphthalocyanine and its “clicked” analogue
- Bankole, Owolabi M, Nyokong, Tebello
- Authors: Bankole, Owolabi M , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189325 , vital:44837 , xlink:href="https://doi.org/10.1016/j.molstruc.2015.01.048"
- Description: We report here for the first time on the photophysical and nonlinear optical behavior of tetra-substituted alkynyl zinc phthalocyanine and its “clicked” analogue (4 and 5). The compounds exhibited high triplet quantum yields in dimethylsulphoxide (DMSO). Nonlinear optical (NLO) properties were also evaluated for the two compounds at 532 nm and 10 ns in DMSO. We observed two-photon absorption (2PA) and strong reverse saturable absorption (RSA) as the dominant mechanisms at nanosecond laser excitation. The presence of electron acceptor groups fused with triazole linkers in the peripheral positions of 4 provide excellent coexistent features, such as enhanced triplet quantum yields and lifetimes compared to 5. Large third-order susceptibility (2.09 × 10−11 and 3.53 × 10−9 esu) and hyperpolarizability (1.09 × 10−30 and 9.13 × 10−29 esu) were estimated for complexs 4 and 5, respectively.
- Full Text:
- Date Issued: 2015
- Authors: Bankole, Owolabi M , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189325 , vital:44837 , xlink:href="https://doi.org/10.1016/j.molstruc.2015.01.048"
- Description: We report here for the first time on the photophysical and nonlinear optical behavior of tetra-substituted alkynyl zinc phthalocyanine and its “clicked” analogue (4 and 5). The compounds exhibited high triplet quantum yields in dimethylsulphoxide (DMSO). Nonlinear optical (NLO) properties were also evaluated for the two compounds at 532 nm and 10 ns in DMSO. We observed two-photon absorption (2PA) and strong reverse saturable absorption (RSA) as the dominant mechanisms at nanosecond laser excitation. The presence of electron acceptor groups fused with triazole linkers in the peripheral positions of 4 provide excellent coexistent features, such as enhanced triplet quantum yields and lifetimes compared to 5. Large third-order susceptibility (2.09 × 10−11 and 3.53 × 10−9 esu) and hyperpolarizability (1.09 × 10−30 and 9.13 × 10−29 esu) were estimated for complexs 4 and 5, respectively.
- Full Text:
- Date Issued: 2015
Photophysical properties and photodynamic therapy effect of zinc phthalocyanine-spermine-single walled carbon nanotube conjugate on MCF-7 breast cancer cell line
- Ogbodu, Rachael O, Limson, Janice L, Prinsloo, Earl, Nyokong, Tebello
- Authors: Ogbodu, Rachael O , Limson, Janice L , Prinsloo, Earl , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189493 , vital:44851 , xlink:href="https://doi.org/10.1016/j.synthmet.2015.03.011"
- Description: The present study shows improved photodynamic therapy (PDT) effect of zinc mono carboxy phenoxy phthalocyanine (ZnMCPPc (1)) upon conjugation to spermine (via amide bond) as a targeting molecule on MCF-7 breast cancer cells. The ZnMCPPc-spermine (2) conjugate was adsorbed onto single walled carbon nanotubes (represented as ZnMCPPc-spermine-SWCNT (3)). There was no change in the fluorescence quantum yield of complex 1 following formation of 2 or 3. Complexes 2 and 3 showed improved photophysical properties; with over 50% increases in triplet and singlet oxygen quantum yields compared to 1. Complexes 1, 2 and 3 were relatively not toxic to MCF-7 cancer cells when incubated with 5–40 μM of each complex for 24 h in the dark. The PDT results showed that at 40 μM complex 1 resulted in only 64% decrease in cell viability, while 2 and 3 improved the PDT effect of 1 to 97% and 95% decrease in cell viability at 40 μM respectively.
- Full Text:
- Date Issued: 2015
- Authors: Ogbodu, Rachael O , Limson, Janice L , Prinsloo, Earl , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189493 , vital:44851 , xlink:href="https://doi.org/10.1016/j.synthmet.2015.03.011"
- Description: The present study shows improved photodynamic therapy (PDT) effect of zinc mono carboxy phenoxy phthalocyanine (ZnMCPPc (1)) upon conjugation to spermine (via amide bond) as a targeting molecule on MCF-7 breast cancer cells. The ZnMCPPc-spermine (2) conjugate was adsorbed onto single walled carbon nanotubes (represented as ZnMCPPc-spermine-SWCNT (3)). There was no change in the fluorescence quantum yield of complex 1 following formation of 2 or 3. Complexes 2 and 3 showed improved photophysical properties; with over 50% increases in triplet and singlet oxygen quantum yields compared to 1. Complexes 1, 2 and 3 were relatively not toxic to MCF-7 cancer cells when incubated with 5–40 μM of each complex for 24 h in the dark. The PDT results showed that at 40 μM complex 1 resulted in only 64% decrease in cell viability, while 2 and 3 improved the PDT effect of 1 to 97% and 95% decrease in cell viability at 40 μM respectively.
- Full Text:
- Date Issued: 2015
Photophysical properties gallium octacarboxy phthalocyanines conjugated to CdSe@ ZnS quantum dots
- Tshangana, Charmaine, Nyokong, Tebello
- Authors: Tshangana, Charmaine , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189055 , vital:44812 , xlink:href="https://doi.org/10.1016/j.saa.2015.06.086"
- Description: L-Glutathione (GSH) capped core CdSe (2.3 nm) and core shell CdSe@ZnS quantum dots (QDs) (3.0 nm and 3.5 nm) were coordinated to gallium octacarboxy phthalocyanine (ClGaPc(COOH)8) to form ClGaPc(COOH)8–QDs conjugates. An efficient transfer of energy from the QDs to the Pcs was demonstrated through Förster resonance energy transfer (FRET), the FRET efficiencies in all cases was above 50%. The photophysical parameters (triplet state and fluorescence quantum yields and lifetimes) were also determined for the conjugates. There was a decrease in the fluorescence lifetimes of ClGaPc(COOH)8 in the presence of all the QDs, due to the heavy atom effect. The triplet quantum yields increased in the conjugates. The lifetimes also became longer for the conjugates compared to Pc alone.
- Full Text:
- Date Issued: 2015
- Authors: Tshangana, Charmaine , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189055 , vital:44812 , xlink:href="https://doi.org/10.1016/j.saa.2015.06.086"
- Description: L-Glutathione (GSH) capped core CdSe (2.3 nm) and core shell CdSe@ZnS quantum dots (QDs) (3.0 nm and 3.5 nm) were coordinated to gallium octacarboxy phthalocyanine (ClGaPc(COOH)8) to form ClGaPc(COOH)8–QDs conjugates. An efficient transfer of energy from the QDs to the Pcs was demonstrated through Förster resonance energy transfer (FRET), the FRET efficiencies in all cases was above 50%. The photophysical parameters (triplet state and fluorescence quantum yields and lifetimes) were also determined for the conjugates. There was a decrease in the fluorescence lifetimes of ClGaPc(COOH)8 in the presence of all the QDs, due to the heavy atom effect. The triplet quantum yields increased in the conjugates. The lifetimes also became longer for the conjugates compared to Pc alone.
- Full Text:
- Date Issued: 2015
Photophysical properties of zinc phthalocyanine–uridine single walled carbon nanotube–conjugates
- Ogbodu, Rachael O, Amuhaya, Edith K, Mashazi, Philani N, Nyokong, Tebello
- Authors: Ogbodu, Rachael O , Amuhaya, Edith K , Mashazi, Philani N , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193586 , vital:45350 , xlink:href="https://doi.org/10.1016/j.saa.2015.04.040"
- Description: The photophysical properties of the conjugate of uridine and zinc mono carboxy phenoxy phthalocyanine (ZnMCPPc–uridine, 4) are reported in this work. The conjugate was also adsorbed onto single walled carbon nanotubes (ZnMCPPc–uridine–SWCNT, 5). The X-ray photoelectron spectroscopy of 4 showed three N 1s peaks while that of 5 showed four N 1s peak, a new peak at 399.4 eV of 5 was assigned to pyrrolidonic nitrogen, due to the interaction of the pyrrolic nitrogen of 4 with the oxygen moiety of SWCNT–COOH in 5. The triplet lifetime, triplet and singlet oxygen quantum yields of the zinc mono carboxy phenoxy phthalocyanine increased by over 40% in the presence of uridine. SWCNTs resulted in only a small quenching of the triplet state parameters of 4.
- Full Text:
- Date Issued: 2015
- Authors: Ogbodu, Rachael O , Amuhaya, Edith K , Mashazi, Philani N , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193586 , vital:45350 , xlink:href="https://doi.org/10.1016/j.saa.2015.04.040"
- Description: The photophysical properties of the conjugate of uridine and zinc mono carboxy phenoxy phthalocyanine (ZnMCPPc–uridine, 4) are reported in this work. The conjugate was also adsorbed onto single walled carbon nanotubes (ZnMCPPc–uridine–SWCNT, 5). The X-ray photoelectron spectroscopy of 4 showed three N 1s peaks while that of 5 showed four N 1s peak, a new peak at 399.4 eV of 5 was assigned to pyrrolidonic nitrogen, due to the interaction of the pyrrolic nitrogen of 4 with the oxygen moiety of SWCNT–COOH in 5. The triplet lifetime, triplet and singlet oxygen quantum yields of the zinc mono carboxy phenoxy phthalocyanine increased by over 40% in the presence of uridine. SWCNTs resulted in only a small quenching of the triplet state parameters of 4.
- Full Text:
- Date Issued: 2015
Photophysical studies of newly derivatized mono substituted phthalocyanines grafted onto silica nanoparticles via click chemistry
- Fashina, Adedayo, Amuhaya, Edith K, Nyokong, Tebello
- Authors: Fashina, Adedayo , Amuhaya, Edith K , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189537 , vital:44855 , xlink:href="https://doi.org/10.1016/j.saa.2014.12.070"
- Description: This work reports on the synthesis, characterization and photophysical studies of newly derived phthalocyanine complexes and the phthalocyanine–silica nanoparticles conjugates. The derived phthalocyanine complexes have one terminal alkyne group. The derived phthalocyanine complexes showed improved photophysical properties (ФF, ФT, ΦΔ and τT) compared to the respective phthalocyanine complexes from which they were derived. The derived phthalocyanine complexes were conjugated to the surface of an azide functionalized silica nanoparticles via copper (1) catalyzed cyclo-addition reaction. All the conjugates showed lower triplet quantum yields ranging from 0.37 to 0.44 compared to the free phthalocyanine complexes. The triplet lifetimes ranged from 352 to 484 μs for the conjugates and from 341 to 366 μs for the free phthalocyanine complexes.
- Full Text:
- Date Issued: 2015
- Authors: Fashina, Adedayo , Amuhaya, Edith K , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189537 , vital:44855 , xlink:href="https://doi.org/10.1016/j.saa.2014.12.070"
- Description: This work reports on the synthesis, characterization and photophysical studies of newly derived phthalocyanine complexes and the phthalocyanine–silica nanoparticles conjugates. The derived phthalocyanine complexes have one terminal alkyne group. The derived phthalocyanine complexes showed improved photophysical properties (ФF, ФT, ΦΔ and τT) compared to the respective phthalocyanine complexes from which they were derived. The derived phthalocyanine complexes were conjugated to the surface of an azide functionalized silica nanoparticles via copper (1) catalyzed cyclo-addition reaction. All the conjugates showed lower triplet quantum yields ranging from 0.37 to 0.44 compared to the free phthalocyanine complexes. The triplet lifetimes ranged from 352 to 484 μs for the conjugates and from 341 to 366 μs for the free phthalocyanine complexes.
- Full Text:
- Date Issued: 2015