Optical nonlinearity of pentadecylphenoxyl substituted sandwich–type metallophthalocyanines in the presence of Ag–CdSeTe/ZnTeSe nanocrystals: Effects of conjugation and central metals
- Oluwole, David O, Nyokong, Tebello
- Authors: Oluwole, David O , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187899 , vital:44708 , xlink:href="https://doi.org/10.1016/j.dyepig.2018.01.009"
- Description: Novel pentadecylphenoxyl substituted homoleptic sandwich–type metallophthalocyanines: bis (complexes 2 and 4 containing Eu and Dy, respectively) and tris (complexes 3 and 5 containing Eu and Dy, respectively) 2,9,16,23–tetrakis–(3–pentadecylphenoxyl) phthalocyanines and cadmium based (Ag–CdSeTe/ZnTeSe) nanocrystals (NCs) were synthesized. The nonlinear optical (NLO) behavior of the metallophthalocyanines and their composites with NCs were investigated using the open aperture Z–scan technique at excitation wavelength of 532 nm with 10 ns pulse. All of the samples exhibited interesting NLO attributes: among all the sandwich–type complexes, complex 5 afforded the most efficient NLO features accounting for large nonlinear absorption coefficient (βeff) value of 3500 cm/GW and limiting threshold (Ilim) value of 0.43 J cm−2. Overall, the composites of the triple decker sandwich–type complexes with Ag–CdSeTe/ZnTeSe yielded the best NLO characteristics with 3 and 5 accounting for the largest βeff value of 5500 cm/GW and Ilim value of 0.09 J cm−2. The synthesized complexes and their composites with NCs could be viable and efficient NLO absorber due to their interesting NLO activities.
- Full Text:
- Date Issued: 2018
- Authors: Oluwole, David O , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187899 , vital:44708 , xlink:href="https://doi.org/10.1016/j.dyepig.2018.01.009"
- Description: Novel pentadecylphenoxyl substituted homoleptic sandwich–type metallophthalocyanines: bis (complexes 2 and 4 containing Eu and Dy, respectively) and tris (complexes 3 and 5 containing Eu and Dy, respectively) 2,9,16,23–tetrakis–(3–pentadecylphenoxyl) phthalocyanines and cadmium based (Ag–CdSeTe/ZnTeSe) nanocrystals (NCs) were synthesized. The nonlinear optical (NLO) behavior of the metallophthalocyanines and their composites with NCs were investigated using the open aperture Z–scan technique at excitation wavelength of 532 nm with 10 ns pulse. All of the samples exhibited interesting NLO attributes: among all the sandwich–type complexes, complex 5 afforded the most efficient NLO features accounting for large nonlinear absorption coefficient (βeff) value of 3500 cm/GW and limiting threshold (Ilim) value of 0.43 J cm−2. Overall, the composites of the triple decker sandwich–type complexes with Ag–CdSeTe/ZnTeSe yielded the best NLO characteristics with 3 and 5 accounting for the largest βeff value of 5500 cm/GW and Ilim value of 0.09 J cm−2. The synthesized complexes and their composites with NCs could be viable and efficient NLO absorber due to their interesting NLO activities.
- Full Text:
- Date Issued: 2018
Optimizing phthalocyanine based dye-sensitized solar cells: The role of reduced graphene oxide
- Chindeka, Francis, Mashazi, Philani N, Britton, Jonathan, Fomo, Gertrude, Oluwole, David O, Sindelo, Azole, Nyokong, Tebello
- Authors: Chindeka, Francis , Mashazi, Philani N , Britton, Jonathan , Fomo, Gertrude , Oluwole, David O , Sindelo, Azole , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187770 , vital:44695 , xlink:href="https://doi.org/10.1016/j.synthmet.2018.10.021"
- Description: Dye-sensitized solar cells (DSSC) were fabricated by incorporating graphene materials as catalysts at the counter electrode. Platinum was also used as a catalyst for comparison purposes. Different phthalocyanines: hydroxyl indium tetracarboxyphenoxy phthalocyanine (1), chloro indium octacarboxy phthalocyanine (2) and dibenzoic acid silicon phthalocyanine (3) were used as dyes. Complex 3 gave the highest power conversion efficiency (η) of 3.19% when using nitrogen doped reduced graphene oxide nanosheets (NrGONS) as a catalyst at the counter electrode, and TiO2 containing rGONS at the anode. The value is close to 3.8% obtained when using Pt catalyst instead of NrGONS at the cathode, thus confirming that NrGONS is a promising candidate to replace the more expensive Pt. The study also shows that placing rGONS on both the anode and cathode improves efficiency.
- Full Text:
- Date Issued: 2018
- Authors: Chindeka, Francis , Mashazi, Philani N , Britton, Jonathan , Fomo, Gertrude , Oluwole, David O , Sindelo, Azole , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187770 , vital:44695 , xlink:href="https://doi.org/10.1016/j.synthmet.2018.10.021"
- Description: Dye-sensitized solar cells (DSSC) were fabricated by incorporating graphene materials as catalysts at the counter electrode. Platinum was also used as a catalyst for comparison purposes. Different phthalocyanines: hydroxyl indium tetracarboxyphenoxy phthalocyanine (1), chloro indium octacarboxy phthalocyanine (2) and dibenzoic acid silicon phthalocyanine (3) were used as dyes. Complex 3 gave the highest power conversion efficiency (η) of 3.19% when using nitrogen doped reduced graphene oxide nanosheets (NrGONS) as a catalyst at the counter electrode, and TiO2 containing rGONS at the anode. The value is close to 3.8% obtained when using Pt catalyst instead of NrGONS at the cathode, thus confirming that NrGONS is a promising candidate to replace the more expensive Pt. The study also shows that placing rGONS on both the anode and cathode improves efficiency.
- Full Text:
- Date Issued: 2018
Photo-induced resonance energy transfer and nonlinear optical response in ball-type phthalocyanine conjugated to semiconductor and graphene quantum dots
- Nwaji, Njemuwa, Achadu, Ojodomo John, Nyokong, Tebello
- Authors: Nwaji, Njemuwa , Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187959 , vital:44713 , xlink:href="https://doi.org/10.1039/C7NJ05196D"
- Description: The synthesis of ball-type zinc and gallium phthalocyanines (complexes 2 and 3) and their covalent linkage to glutathione (GSH) and amine functionalized quantum dots QDs) are reported in this work. Furthermore, their photophysical, photo-induced resonance energy transfer and optical limiting responses were investigated. We observed a decrease in the fluorescence quantum yields with a corresponding increase in the triplet quantum yields of the nanoconjugates in comparison to the phthalocyanine complexes alone. The reverse saturable absorption was found to be dependent on the excited state absorption, and the observed limiting threshold ranged from 0.32 to 1.43 J cm−2. Enhanced triplet parameters and nonlinear optical performance were found when the complexes were covalently linked to semiconductor quantum dots compared to carbon based graphene quantum dots.
- Full Text:
- Date Issued: 2018
- Authors: Nwaji, Njemuwa , Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187959 , vital:44713 , xlink:href="https://doi.org/10.1039/C7NJ05196D"
- Description: The synthesis of ball-type zinc and gallium phthalocyanines (complexes 2 and 3) and their covalent linkage to glutathione (GSH) and amine functionalized quantum dots QDs) are reported in this work. Furthermore, their photophysical, photo-induced resonance energy transfer and optical limiting responses were investigated. We observed a decrease in the fluorescence quantum yields with a corresponding increase in the triplet quantum yields of the nanoconjugates in comparison to the phthalocyanine complexes alone. The reverse saturable absorption was found to be dependent on the excited state absorption, and the observed limiting threshold ranged from 0.32 to 1.43 J cm−2. Enhanced triplet parameters and nonlinear optical performance were found when the complexes were covalently linked to semiconductor quantum dots compared to carbon based graphene quantum dots.
- Full Text:
- Date Issued: 2018
Photodynamic therapy activity of zinc phthalocyanine linked to folic acid and magnetic nanoparticles
- Matlou, Gauta G, Oluwole, David O, Prinsloo, Earl, Nyokong, Tebello
- Authors: Matlou, Gauta G , Oluwole, David O , Prinsloo, Earl , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/234429 , vital:50195 , xlink:href="https://doi.org/10.1016/j.jphotobiol.2018.07.025"
- Description: In this work, the photodynamic therapy (PDT) activities (using human carcinoma adherent MCF-7 cells) of zinc phthalocyanine derivatives: complexes 1 (Zn mono cinnamic acid phthalocyanine) and 2 (zinc mono carboxyphenoxy phthalocyanine) when covalently linked to folic acid (FA) and amine functionalized magnetic nanoparticles (AMNPs) are reported. The covalent linkage of asymmetric zinc cinnamic acid Pc (1) to FA (1-FA) through an amide bond is reported for the first time. Complex 1 is insoluble in water, but upon linkage to FA, (to form 1-FA) the molecule become water soluble, hence the UV–Vis spectrum and singlet oxygen quantum yield for 1-FA were also done in water since water solubility is essential for biological applications. The reported 2-FA is also water soluble. Linking complexes 1 and 2 to FA and AMNPs decreased the dark toxicity of 1 and 2 on MCF-7 cells. Pc-FA (1-FA and 2-FA) conjugates had better singlet oxygen quantum yields (Φ∆) in DMSO as compared to Pc-AMNPs (1-AMNPs and 2-AMNPs). The water- soluble 1-FA and 2-FA also achieved a better photodynamic therapy (PDT) activity as compared to 1-AMNPs and 2-AMNPs. Folic acid targeting on the tumor cells may have also facilitated better bioavailability of 1-FA and 2-FA and improved PDT activity on MCF-7 cells over AMNPs carriers.
- Full Text:
- Date Issued: 2018
Photodynamic therapy activity of zinc phthalocyanine linked to folic acid and magnetic nanoparticles
- Authors: Matlou, Gauta G , Oluwole, David O , Prinsloo, Earl , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/234429 , vital:50195 , xlink:href="https://doi.org/10.1016/j.jphotobiol.2018.07.025"
- Description: In this work, the photodynamic therapy (PDT) activities (using human carcinoma adherent MCF-7 cells) of zinc phthalocyanine derivatives: complexes 1 (Zn mono cinnamic acid phthalocyanine) and 2 (zinc mono carboxyphenoxy phthalocyanine) when covalently linked to folic acid (FA) and amine functionalized magnetic nanoparticles (AMNPs) are reported. The covalent linkage of asymmetric zinc cinnamic acid Pc (1) to FA (1-FA) through an amide bond is reported for the first time. Complex 1 is insoluble in water, but upon linkage to FA, (to form 1-FA) the molecule become water soluble, hence the UV–Vis spectrum and singlet oxygen quantum yield for 1-FA were also done in water since water solubility is essential for biological applications. The reported 2-FA is also water soluble. Linking complexes 1 and 2 to FA and AMNPs decreased the dark toxicity of 1 and 2 on MCF-7 cells. Pc-FA (1-FA and 2-FA) conjugates had better singlet oxygen quantum yields (Φ∆) in DMSO as compared to Pc-AMNPs (1-AMNPs and 2-AMNPs). The water- soluble 1-FA and 2-FA also achieved a better photodynamic therapy (PDT) activity as compared to 1-AMNPs and 2-AMNPs. Folic acid targeting on the tumor cells may have also facilitated better bioavailability of 1-FA and 2-FA and improved PDT activity on MCF-7 cells over AMNPs carriers.
- Full Text:
- Date Issued: 2018
Photophysical and strong optical limiting properties of ball-type phthalocyanines dimers and their monomeric analogues
- Nwaji, Njemuwa, Mack, John, Nyokong, Tebello
- Authors: Nwaji, Njemuwa , Mack, John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187930 , vital:44711 , xlink:href="https://doi.org/10.1016/j.jphotochem.2017.10.045"
- Description: The nonlinear optical behaviors of ball-type phthalocyanine complexes: 1′,11,’15′,25′-tetrakis-[4,4′-((4-formyl-1,2-bisphenoxyl))bis(phthalocyaninato zinc (II)] (5), 1′,11,’15′,25′-tetrakis-[4,4′-((4-formyl-1,2-bisphenoxyl) bis(phthalocyaninato gallium (III) chloride)] (6), and 1′, 11,’15′,25′-tetrakis-4,4′-((4-formyl-1,2-phenoxyl)bis(phthalocyaninato indium (III) chloride)] (7) and the corresponding monomeric derivatives 8–10 were investigated using nanosecond pulse open aperture Z-scan technique at 532 nm. The nonlinear response showed strong reverse saturable absorption for all the complexes both in solution and when embedded in polymer matrix. The dimeric complexes showed better optical limiting properties compared to the monomeric derivatives. The βeff values for the dimeric complexes 5–7 were found to be 48.5, 55.2, and 60.1 cm/GW for 5, 6A, and 7 respectively, higher than the corresponding monomeric derivatives 8–10. Enhanced optical limiting properties were observed when the complexes were formulated in thin films. The second order hyperpolarizability values were in order of 10−28–10−26 esu in solution and 10−27–10−26 in films.
- Full Text:
- Date Issued: 2018
- Authors: Nwaji, Njemuwa , Mack, John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187930 , vital:44711 , xlink:href="https://doi.org/10.1016/j.jphotochem.2017.10.045"
- Description: The nonlinear optical behaviors of ball-type phthalocyanine complexes: 1′,11,’15′,25′-tetrakis-[4,4′-((4-formyl-1,2-bisphenoxyl))bis(phthalocyaninato zinc (II)] (5), 1′,11,’15′,25′-tetrakis-[4,4′-((4-formyl-1,2-bisphenoxyl) bis(phthalocyaninato gallium (III) chloride)] (6), and 1′, 11,’15′,25′-tetrakis-4,4′-((4-formyl-1,2-phenoxyl)bis(phthalocyaninato indium (III) chloride)] (7) and the corresponding monomeric derivatives 8–10 were investigated using nanosecond pulse open aperture Z-scan technique at 532 nm. The nonlinear response showed strong reverse saturable absorption for all the complexes both in solution and when embedded in polymer matrix. The dimeric complexes showed better optical limiting properties compared to the monomeric derivatives. The βeff values for the dimeric complexes 5–7 were found to be 48.5, 55.2, and 60.1 cm/GW for 5, 6A, and 7 respectively, higher than the corresponding monomeric derivatives 8–10. Enhanced optical limiting properties were observed when the complexes were formulated in thin films. The second order hyperpolarizability values were in order of 10−28–10−26 esu in solution and 10−27–10−26 in films.
- Full Text:
- Date Issued: 2018
Photophysical properties of a novel styryl-BODIPY with a fused crown ether moiety
- Stone, Justin, Mack, John, Nyokong, Tebello, Kimura, Mitsumi, Kobayashi, Nagao
- Authors: Stone, Justin , Mack, John , Nyokong, Tebello , Kimura, Mitsumi , Kobayashi, Nagao
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188227 , vital:44736 , xlink:href="https://doi.org/10.1142/S1088424617500699"
- Description: The synthesis and characterization of a crown-ether-substituted 3-styrylBODIPY dye with a 4-isopropylphenyl group at the meso-position is reported. The effect that the incorporation of Na++ ions into the crown ether moiety has on the photophysical properties is investigated.
- Full Text:
- Date Issued: 2018
- Authors: Stone, Justin , Mack, John , Nyokong, Tebello , Kimura, Mitsumi , Kobayashi, Nagao
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188227 , vital:44736 , xlink:href="https://doi.org/10.1142/S1088424617500699"
- Description: The synthesis and characterization of a crown-ether-substituted 3-styrylBODIPY dye with a 4-isopropylphenyl group at the meso-position is reported. The effect that the incorporation of Na++ ions into the crown ether moiety has on the photophysical properties is investigated.
- Full Text:
- Date Issued: 2018
Photophysical studies of graphene quantum dots-Pyrene-derivatized porphyrins conjugates when encapsulated within Pluronic F127 micelles
- Managa, Muthumuni, Achadu, Ojodomo John, Nyokong, Tebello
- Authors: Managa, Muthumuni , Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187971 , vital:44714 , xlink:href="https://doi.org/10.1016/j.dyepig.2017.09.031"
- Description: Pyrene-derivatized H2, GaCl, and Zn porphyrins were immobilized on graphene quantum dots (GQDs) to form (GQDs-H2TPrP, GQDs-GaClTPrP, and GQDs-ZnTPrP) conjugates through the π-π stacking interaction method followed by encapsulating into Pluronic F127 micelles to form (GQDs-H2TPrP + F127, GQDs-GaClTPrP + F127, and GQDs-ZnTPrP + F127). Spectroscopic evidence shows that the resultant conjugates were stable due to the strong π-π stacking interaction between the GQDs and the porphyrins. The fluorescence and singlet oxygen generating behaviour of the porphyrins were investigated following incorporation. GQDs-GaClTPrP + F127 showed highest values of the binding constant (Kb). The Stern-Volmer constant (Ksv) for GQDs-ZnTPrP + F127 were the highest compared to other porphyrins derivatives.
- Full Text:
- Date Issued: 2018
- Authors: Managa, Muthumuni , Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187971 , vital:44714 , xlink:href="https://doi.org/10.1016/j.dyepig.2017.09.031"
- Description: Pyrene-derivatized H2, GaCl, and Zn porphyrins were immobilized on graphene quantum dots (GQDs) to form (GQDs-H2TPrP, GQDs-GaClTPrP, and GQDs-ZnTPrP) conjugates through the π-π stacking interaction method followed by encapsulating into Pluronic F127 micelles to form (GQDs-H2TPrP + F127, GQDs-GaClTPrP + F127, and GQDs-ZnTPrP + F127). Spectroscopic evidence shows that the resultant conjugates were stable due to the strong π-π stacking interaction between the GQDs and the porphyrins. The fluorescence and singlet oxygen generating behaviour of the porphyrins were investigated following incorporation. GQDs-GaClTPrP + F127 showed highest values of the binding constant (Kb). The Stern-Volmer constant (Ksv) for GQDs-ZnTPrP + F127 were the highest compared to other porphyrins derivatives.
- Full Text:
- Date Issued: 2018
Photophysicochemical behaviour and antimicrobial properties of monocarboxy Mg (II) and Al (III) phthalocyanine-magnetite conjugates
- Idowu, Mopelola A I, Xego, Solami, Arslanoglu, Yasin, Mark, John, Antunes, Edith M, Nyokong, Tebello
- Authors: Idowu, Mopelola A I , Xego, Solami , Arslanoglu, Yasin , Mark, John , Antunes, Edith M , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188205 , vital:44734 , xlink:href="https://doi.org/10.1016/j.saa.2017.12.052"
- Description: Asymmetric Mg (II) or Al (III) phthalocyanine (containing a COOH group and 3-pyridylsulfanyl units) was conjugated via an amide bond to amino functionalized magnetic nanoparticle (AIMN) to form MgPc-AIMN or AlPc-AIMN conjugate, and characterized. The photophysicochemical behaviour of the phthalocyanine–AIMN conjugates was investigated and compared to the asymmetric Pcs and to the simple mixture of Pc with AIMNs without a chemical bond, (MPc-AIMN (mixed)). The directed covalent linkage of AIMNs to the asymmetrical metallopthalocyanines afforded improvements in the singlet oxygen (ФΔ) and triplet state quantum yield (ФT) as well as singlet oxygen lifetimes for the MPcs–AIMN-linked conjugates compared to MPc-AIMN (mixed) and MPcs alone. The asymmetric phthalocyanines and their conjugates showed effective antimicrobial activity against Escherichia coli bacteria under illumination.
- Full Text:
- Date Issued: 2018
- Authors: Idowu, Mopelola A I , Xego, Solami , Arslanoglu, Yasin , Mark, John , Antunes, Edith M , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188205 , vital:44734 , xlink:href="https://doi.org/10.1016/j.saa.2017.12.052"
- Description: Asymmetric Mg (II) or Al (III) phthalocyanine (containing a COOH group and 3-pyridylsulfanyl units) was conjugated via an amide bond to amino functionalized magnetic nanoparticle (AIMN) to form MgPc-AIMN or AlPc-AIMN conjugate, and characterized. The photophysicochemical behaviour of the phthalocyanine–AIMN conjugates was investigated and compared to the asymmetric Pcs and to the simple mixture of Pc with AIMNs without a chemical bond, (MPc-AIMN (mixed)). The directed covalent linkage of AIMNs to the asymmetrical metallopthalocyanines afforded improvements in the singlet oxygen (ФΔ) and triplet state quantum yield (ФT) as well as singlet oxygen lifetimes for the MPcs–AIMN-linked conjugates compared to MPc-AIMN (mixed) and MPcs alone. The asymmetric phthalocyanines and their conjugates showed effective antimicrobial activity against Escherichia coli bacteria under illumination.
- Full Text:
- Date Issued: 2018
Photophysicochemical properties and photodynamic therapy activity of highly water-soluble Zn (II) phthalocyanines
- Oluwole, David O, Sari, Fatma Aslihan, Prinsloo, Earl, Dube, Edith, Yuzer, Abdulcelil, Nyokong, Tebello, Ince, Mine
- Authors: Oluwole, David O , Sari, Fatma Aslihan , Prinsloo, Earl , Dube, Edith , Yuzer, Abdulcelil , Nyokong, Tebello , Ince, Mine
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/234507 , vital:50203 , xlink:href="https://doi.org/10.1016/j.saa.2018.05.090"
- Description: The syntheses of two zinc(II) phthalocyanines (ZnPcs) having either imidazole (ZnPc 1) or pyridiloxy (ZnPc 2) moieties as their macrocycle substituents are reported. Quaternization of the ZnPcs with methyl iodide afforded water soluble cationic phthalocyanines. The photophysical, photochemical properties and photodynamic therapy (PDT) activity of the ZnPcs were studied in solution. The fluorescence quantum yield and lifetime of ZnPc 1 were higher as compared to ZnPc 2. ZnPc 2 afforded higher triplet state (ΦT) and singlet oxygen quantum yields (ΦΔ) in comparison to ZnPc 1. The PDT activity of ZnPcs was investigated against human breast adenocarcinoma cells (MCF–7). The two compounds afforded a very minimal in vitro dark cytotoxicity with 85% viable cells at concentration ≤80 μM. On irradiation of the cells having the ZnPcs, ≥50% cell death was recorded for ZnPc 1 which was also evidenced by the cells photo–micrograph.
- Full Text:
- Date Issued: 2018
- Authors: Oluwole, David O , Sari, Fatma Aslihan , Prinsloo, Earl , Dube, Edith , Yuzer, Abdulcelil , Nyokong, Tebello , Ince, Mine
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/234507 , vital:50203 , xlink:href="https://doi.org/10.1016/j.saa.2018.05.090"
- Description: The syntheses of two zinc(II) phthalocyanines (ZnPcs) having either imidazole (ZnPc 1) or pyridiloxy (ZnPc 2) moieties as their macrocycle substituents are reported. Quaternization of the ZnPcs with methyl iodide afforded water soluble cationic phthalocyanines. The photophysical, photochemical properties and photodynamic therapy (PDT) activity of the ZnPcs were studied in solution. The fluorescence quantum yield and lifetime of ZnPc 1 were higher as compared to ZnPc 2. ZnPc 2 afforded higher triplet state (ΦT) and singlet oxygen quantum yields (ΦΔ) in comparison to ZnPc 1. The PDT activity of ZnPcs was investigated against human breast adenocarcinoma cells (MCF–7). The two compounds afforded a very minimal in vitro dark cytotoxicity with 85% viable cells at concentration ≤80 μM. On irradiation of the cells having the ZnPcs, ≥50% cell death was recorded for ZnPc 1 which was also evidenced by the cells photo–micrograph.
- Full Text:
- Date Issued: 2018
Photophysics and NLO properties of Ga (III) and In (III) phthalocyaninates bearing diethyleneglycol chains
- Managa, Muthumuni, Khene, Samson M, Britton, Jonathan, Martynov, Alexander G, Gorbunova, Yulia G, Tsivadze, Aslan Y, Nyokong, Tebello
- Authors: Managa, Muthumuni , Khene, Samson M , Britton, Jonathan , Martynov, Alexander G , Gorbunova, Yulia G , Tsivadze, Aslan Y , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/237822 , vital:50556 , xlink:href="https://doi.org/10.1142/S1088424618500128"
- Description: This work reports on synthesis and characterizations of Ga(III) and In(III) complexes, formed by 2,3-bis[2′′-(2′′′′-hydroxyethoxy)ethoxy]-9,10,16,17,23,24-hexa-nn-butoxy phthalocyanine (1H2) coordinating acetatoindium(III) (1InOAc) and hydroxogallium(III) (1GaOH) Photophysical properties of hydroxogallium(III) phthalocyaninate 1GaOH and acetatoindium(III) phthalocyaninate 1InOAc were studied by UV-vis, fluorescence spectroscopy and time-resolved methods. The nonlinear absorption of the complexes was studied using the Z-scan technique at 532 nm and 10 ns pulse in DMSO and in thin films formed by composite with poly(bisphenol A carbonate) — PBC. The magnitude of absorption coefficients and other nonlinear optical parameters estimated in this work showed that complex 1InOAc exhibited the strongest nonlinear optical behavior in comparison with 1GaOH in solution and a reverse tendency when embedded in PBC thin films. DFT calculations were used to rationalize these results.
- Full Text:
- Date Issued: 2018
- Authors: Managa, Muthumuni , Khene, Samson M , Britton, Jonathan , Martynov, Alexander G , Gorbunova, Yulia G , Tsivadze, Aslan Y , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/237822 , vital:50556 , xlink:href="https://doi.org/10.1142/S1088424618500128"
- Description: This work reports on synthesis and characterizations of Ga(III) and In(III) complexes, formed by 2,3-bis[2′′-(2′′′′-hydroxyethoxy)ethoxy]-9,10,16,17,23,24-hexa-nn-butoxy phthalocyanine (1H2) coordinating acetatoindium(III) (1InOAc) and hydroxogallium(III) (1GaOH) Photophysical properties of hydroxogallium(III) phthalocyaninate 1GaOH and acetatoindium(III) phthalocyaninate 1InOAc were studied by UV-vis, fluorescence spectroscopy and time-resolved methods. The nonlinear absorption of the complexes was studied using the Z-scan technique at 532 nm and 10 ns pulse in DMSO and in thin films formed by composite with poly(bisphenol A carbonate) — PBC. The magnitude of absorption coefficients and other nonlinear optical parameters estimated in this work showed that complex 1InOAc exhibited the strongest nonlinear optical behavior in comparison with 1GaOH in solution and a reverse tendency when embedded in PBC thin films. DFT calculations were used to rationalize these results.
- Full Text:
- Date Issued: 2018
Physicochemical properties of water soluble unsymmetrical phthalocyanine-folic acid conjugates
- Matlou, Gauta G, Kobayashi, Nagao, Kimura, Mutsumi, Nyokong, Tebello
- Authors: Matlou, Gauta G , Kobayashi, Nagao , Kimura, Mutsumi , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233240 , vital:50071 , xlink:href="https://doi.org/10.1016/j.dyepig.2017.10.030"
- Description: This work reports on the successful chemical linkage of folic acid (FA) to Zn mono carboxyphenoxy phthalocyanine (1) and Zn mono carboxyphenoxy tri–(tert–butyl) phthalocyanine (2). The amide bond linkage of FA to phthalocyanine (Pc) is achieved for the first time through the FA-NH2 and Pc-COOH and confirmed using FTIR, MS, elemental analysis and NMR. The linked conjugates were found to be water soluble compared to the physical mixtures of FA and Pc, which allowed for studies of singlet oxygen in water. The Pc-FA linked conjugates (1-FA and 2-FA) were found to be singlet oxygen generators with the following singlet oxygen quantum yields: 1-FA = 0.61 and 2-FA = 0.47 in DMSO and 1-FA = 0.17 and 2-FA = 0.12 in water.
- Full Text:
- Date Issued: 2018
- Authors: Matlou, Gauta G , Kobayashi, Nagao , Kimura, Mutsumi , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233240 , vital:50071 , xlink:href="https://doi.org/10.1016/j.dyepig.2017.10.030"
- Description: This work reports on the successful chemical linkage of folic acid (FA) to Zn mono carboxyphenoxy phthalocyanine (1) and Zn mono carboxyphenoxy tri–(tert–butyl) phthalocyanine (2). The amide bond linkage of FA to phthalocyanine (Pc) is achieved for the first time through the FA-NH2 and Pc-COOH and confirmed using FTIR, MS, elemental analysis and NMR. The linked conjugates were found to be water soluble compared to the physical mixtures of FA and Pc, which allowed for studies of singlet oxygen in water. The Pc-FA linked conjugates (1-FA and 2-FA) were found to be singlet oxygen generators with the following singlet oxygen quantum yields: 1-FA = 0.61 and 2-FA = 0.47 in DMSO and 1-FA = 0.17 and 2-FA = 0.12 in water.
- Full Text:
- Date Issued: 2018
Point-of-care and lung ultrasound incorporated in daily practice
- Neethling, E, Roodt, F, Beck, C, Swanevelder, J L C
- Authors: Neethling, E , Roodt, F , Beck, C , Swanevelder, J L C
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/5248 , vital:44424 , http://www.samj.org.za/index.php/samj/article/view/12293
- Description: Point-of-care ultrasound (POCUS) is a fast-growing clinical utility and is becoming an essential clinical skill for all practitioners attending to critically ill patients. Ultrasound equipment is now smaller, more affordable and readily available in clinical work areas. POCUS is performed by a non-cardiologist physician at the patient’s bedside as an adjunct to the physical examination. It is easily taught, non-invasive and allows for real-time clinical information. Bedside use of ultrasound imaging aids with rapid diagnosis of severe and life-threatening pathological conditions. It can be repeated, may change clinical management, and impact on patient outcome. POCUS has a broad clinical use, including, but not limited to, focused assessed transthoracic echocardiography (FATE), lung ultrasound imaging, extended focused assessment with sonography for trauma (e-FAST), vascular access and regional blocks. It may also be extended to detect endotracheal intubation and the estimation of intracranial pressure. Assessment of cardiac pathology by POCUS, performed by a novice examiner, has been shown to compare with the gold standard of an expert. Training is paramount. The physician should know his limitations and always relate the information back to the clinical scenario and context. By incorporating POCUS as part of our armamentarium and into our daily medical practice, we might see it reach its full clinical potential, optimising patient care and improving patient outcomes.
- Full Text:
- Date Issued: 2018
- Authors: Neethling, E , Roodt, F , Beck, C , Swanevelder, J L C
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/5248 , vital:44424 , http://www.samj.org.za/index.php/samj/article/view/12293
- Description: Point-of-care ultrasound (POCUS) is a fast-growing clinical utility and is becoming an essential clinical skill for all practitioners attending to critically ill patients. Ultrasound equipment is now smaller, more affordable and readily available in clinical work areas. POCUS is performed by a non-cardiologist physician at the patient’s bedside as an adjunct to the physical examination. It is easily taught, non-invasive and allows for real-time clinical information. Bedside use of ultrasound imaging aids with rapid diagnosis of severe and life-threatening pathological conditions. It can be repeated, may change clinical management, and impact on patient outcome. POCUS has a broad clinical use, including, but not limited to, focused assessed transthoracic echocardiography (FATE), lung ultrasound imaging, extended focused assessment with sonography for trauma (e-FAST), vascular access and regional blocks. It may also be extended to detect endotracheal intubation and the estimation of intracranial pressure. Assessment of cardiac pathology by POCUS, performed by a novice examiner, has been shown to compare with the gold standard of an expert. Training is paramount. The physician should know his limitations and always relate the information back to the clinical scenario and context. By incorporating POCUS as part of our armamentarium and into our daily medical practice, we might see it reach its full clinical potential, optimising patient care and improving patient outcomes.
- Full Text:
- Date Issued: 2018
Porphyrin dimers with a bridging chiral amide-bonded benzo-moiety
- Liang, Xu, Qin, Mingfeng, Zhou, Lin, Liu, Tingting, Li, Minzhi, Mack, John, Ndebele, Nobuhle, Nyokong, Tebello, Zhu, Weihua
- Authors: Liang, Xu , Qin, Mingfeng , Zhou, Lin , Liu, Tingting , Li, Minzhi , Mack, John , Ndebele, Nobuhle , Nyokong, Tebello , Zhu, Weihua
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233433 , vital:50090 , xlink:href="https://doi.org/10.1016/j.dyepig.2018.02.043"
- Description: The facile synthesis and characterization of four porphyrin dimers which introduced stereomeric centers with chiral amide-bonded para- and meta-disubstituted benzo-moiety is reported. Trends in the electronic structures and optical and redox properties are analyzed through a comparison with theoretical calculations to explore the effect of positional isomerism of the bridging benzene rings.
- Full Text:
- Date Issued: 2018
- Authors: Liang, Xu , Qin, Mingfeng , Zhou, Lin , Liu, Tingting , Li, Minzhi , Mack, John , Ndebele, Nobuhle , Nyokong, Tebello , Zhu, Weihua
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233433 , vital:50090 , xlink:href="https://doi.org/10.1016/j.dyepig.2018.02.043"
- Description: The facile synthesis and characterization of four porphyrin dimers which introduced stereomeric centers with chiral amide-bonded para- and meta-disubstituted benzo-moiety is reported. Trends in the electronic structures and optical and redox properties are analyzed through a comparison with theoretical calculations to explore the effect of positional isomerism of the bridging benzene rings.
- Full Text:
- Date Issued: 2018
Postgraduate writing groups as spaces of agency development
- Oluwole, David O, Achadu, A, Asfour, Fouad-Martin, Chakona, Gamuchirai, Mason, Paul, Mataruse, P, McKenna, Sioux
- Authors: Oluwole, David O , Achadu, A , Asfour, Fouad-Martin , Chakona, Gamuchirai , Mason, Paul , Mataruse, P , McKenna, Sioux
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187194 , vital:44578 , xlink:href="https://doi.org/10.20853/32-6-2963"
- Description: Academic writing is a peculiar phenomenon – it varies greatly from discipline to discipline and its requirements are rarely made overt. Taking on the writing practices of the academy has implications for identity and it is thus unsurprising that it is seen to be a risky endeavour. This article analyses the experiences of postgraduate scholars who have participated in writing groups that meet weekly to read each other’s work and provide supportive critique. Thirty-two people provided detailed, anonymous evaluations of their writing groups and these were studied using a discourse analysis. Three main findings are discussed here. Firstly, writing circles allowed for academic writing development to be engaged with as a social practice, where the disciplinary norms could be made more explicit through peer deliberation, and where they could also be challenged. Secondly, the lack of hierarchical power in the writing groups was key to making safe spaces for agency development, and also for providing positive peer pressure whereby participants were spurred on to work on their writing. Thirdly, the fact that the groups were interdisciplinary, within cognate disciplinary families, provided an interesting challenge in that the students had to consider what these non-specialist readers would or would not understand. This process assisted students in clarifying their writing. Participants’ evaluation of the writing groups revealed an overall sense that these contributed to postgraduate student wellbeing and were places of significant agential development.
- Full Text:
- Date Issued: 2018
- Authors: Oluwole, David O , Achadu, A , Asfour, Fouad-Martin , Chakona, Gamuchirai , Mason, Paul , Mataruse, P , McKenna, Sioux
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187194 , vital:44578 , xlink:href="https://doi.org/10.20853/32-6-2963"
- Description: Academic writing is a peculiar phenomenon – it varies greatly from discipline to discipline and its requirements are rarely made overt. Taking on the writing practices of the academy has implications for identity and it is thus unsurprising that it is seen to be a risky endeavour. This article analyses the experiences of postgraduate scholars who have participated in writing groups that meet weekly to read each other’s work and provide supportive critique. Thirty-two people provided detailed, anonymous evaluations of their writing groups and these were studied using a discourse analysis. Three main findings are discussed here. Firstly, writing circles allowed for academic writing development to be engaged with as a social practice, where the disciplinary norms could be made more explicit through peer deliberation, and where they could also be challenged. Secondly, the lack of hierarchical power in the writing groups was key to making safe spaces for agency development, and also for providing positive peer pressure whereby participants were spurred on to work on their writing. Thirdly, the fact that the groups were interdisciplinary, within cognate disciplinary families, provided an interesting challenge in that the students had to consider what these non-specialist readers would or would not understand. This process assisted students in clarifying their writing. Participants’ evaluation of the writing groups revealed an overall sense that these contributed to postgraduate student wellbeing and were places of significant agential development.
- Full Text:
- Date Issued: 2018
Potential latitudinal variation in orodigestive tract cancers in Africa
- Adeola, H A, Adefuye, A O, Jimoh, S A
- Authors: Adeola, H A , Adefuye, A O , Jimoh, S A
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/5280 , vital:44428 , http://www.samj.org.za/index.php/samj/article/view/12259
- Description: Background. Previous studies have alluded to a causal relationship between pathological entities and geographical variations, but there is a paucity of studies from Africa discussing the effect of latitudinal variation on orodigestive cancers in this region. It seems plausible that the burden of orodigestive cancer would differ as a result of variations in diet, cultural habits, climate and environmental conditions down the length of Africa. Objectives. To analyse regional variations in prevalence, incidence and mortality data in the global cancer statistics database (GLOBOCAN 2012) curated by the World Health Organization and the International Agency for Research on Cancer. Basic descriptive statistical tools were used to depict regional variations in cancer morbidity and mortality. Methods. Data on 13 African countries between longitude 20⁰ and 30⁰ east and latitude 35⁰ north and 35⁰ south were examined for variation in age-standardised orodigestive cancer prevalence, incidence and mortality. Possible regional causes for orodigestive tract cancer development were investigated. Data on lip and oral cavity, oesophageal, gastric, colorectal, liver, gallbladder and pancreatic cancers in the 13 countries were compared. Results. Our empirical findings from this preliminary study support the notion that the incidence and prevalence of orodigestive cancers vary within Africa. This effect may be due to environmental, economic, political and possibly genetic factors. Conclusions. Considering the heterogeneity of the above factors across Africa, disbursement of funding for cancer research and therapy in Africa should be focused in terms of regional variations to make best use of the fiscal allocation by African governments, non-governmental organisations and international agencies.
- Full Text:
- Date Issued: 2018
- Authors: Adeola, H A , Adefuye, A O , Jimoh, S A
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/5280 , vital:44428 , http://www.samj.org.za/index.php/samj/article/view/12259
- Description: Background. Previous studies have alluded to a causal relationship between pathological entities and geographical variations, but there is a paucity of studies from Africa discussing the effect of latitudinal variation on orodigestive cancers in this region. It seems plausible that the burden of orodigestive cancer would differ as a result of variations in diet, cultural habits, climate and environmental conditions down the length of Africa. Objectives. To analyse regional variations in prevalence, incidence and mortality data in the global cancer statistics database (GLOBOCAN 2012) curated by the World Health Organization and the International Agency for Research on Cancer. Basic descriptive statistical tools were used to depict regional variations in cancer morbidity and mortality. Methods. Data on 13 African countries between longitude 20⁰ and 30⁰ east and latitude 35⁰ north and 35⁰ south were examined for variation in age-standardised orodigestive cancer prevalence, incidence and mortality. Possible regional causes for orodigestive tract cancer development were investigated. Data on lip and oral cavity, oesophageal, gastric, colorectal, liver, gallbladder and pancreatic cancers in the 13 countries were compared. Results. Our empirical findings from this preliminary study support the notion that the incidence and prevalence of orodigestive cancers vary within Africa. This effect may be due to environmental, economic, political and possibly genetic factors. Conclusions. Considering the heterogeneity of the above factors across Africa, disbursement of funding for cancer research and therapy in Africa should be focused in terms of regional variations to make best use of the fiscal allocation by African governments, non-governmental organisations and international agencies.
- Full Text:
- Date Issued: 2018
Price determination of non-timber forest products in different areas of South Africa
- Mugido, Worship, Shackleton, Charlie M
- Authors: Mugido, Worship , Shackleton, Charlie M
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/179825 , vital:43192 , xlink:href="https://doi.org/10.1016/j.ecolecon.2017.12.010"
- Description: A wide variety of factors can influence the price determination of non-timber forest products (NTFPs) in individual markets. However, there is little understanding of differences across multiple markets within a uniform macro context, or how they might vary between different types of NTFPs. Therefore, this study sought to determine the factors and rationale behind the setting of prices for selected NTFPs in 15 different areas of South Africa. The results showed that the pricing factors considered by sellers when setting the prices of NTFP varied with the type of NTFP being sold, type of market (home markets or urban markets) and the method used by the seller to procure the stock. Overall, transport costs, stock price, profit margin, time taken to collect or produce the product and market price were the widely used factors to determine prices for NTFPs. The marked variation in both markets and products show that there was no formal or certain price setting mechanism that was used by NTFP sellers establish the market prices of NTFPs, with price discovery being the most widespread.
- Full Text:
- Date Issued: 2018
- Authors: Mugido, Worship , Shackleton, Charlie M
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/179825 , vital:43192 , xlink:href="https://doi.org/10.1016/j.ecolecon.2017.12.010"
- Description: A wide variety of factors can influence the price determination of non-timber forest products (NTFPs) in individual markets. However, there is little understanding of differences across multiple markets within a uniform macro context, or how they might vary between different types of NTFPs. Therefore, this study sought to determine the factors and rationale behind the setting of prices for selected NTFPs in 15 different areas of South Africa. The results showed that the pricing factors considered by sellers when setting the prices of NTFP varied with the type of NTFP being sold, type of market (home markets or urban markets) and the method used by the seller to procure the stock. Overall, transport costs, stock price, profit margin, time taken to collect or produce the product and market price were the widely used factors to determine prices for NTFPs. The marked variation in both markets and products show that there was no formal or certain price setting mechanism that was used by NTFP sellers establish the market prices of NTFPs, with price discovery being the most widespread.
- Full Text:
- Date Issued: 2018
Production, purification, and characterisation of proteases from an ericoid mycorrhizal fungus, Oidiodendron maius
- Authors: Manyumwa, Colleen Varaidzo
- Date: 2018
- Subjects: Ascomycetes , Mycorrhizal fungi , Ericaceae , Proteolytic enzymes , Silver Recycling
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/62833 , vital:28298
- Description: The aim of this study was to produce, purify and characterise proteases from the ericoid mycorrhizal fungus, Oidiodendron maius (CafRU082b/KP119480), as well as to explore their potential application in the recovery of silver from X-ray film. Firstly, the growth of the ericoid mycorrhizal fungus, Oidiodendron maius (CafRU082b), was studied, and its ability to produce proteolytic enzymes was investigated. O. maius proved to grow well in the dark, submerged in Modified Melin Norkran’s liquid medium at a pH of 5 and at 25°C. Pure cultures of the fungus were maintained on Potato Dextrose Agar (PDA). The fungus grew on PDA plates containing different substrates including haemoglobin, casein, gelatin as well as azocasein. Zones of clearance, however, were only observed on plates containing gelatin after treatment with mercuric chloride, HgCl2. Proteases were successfully produced after 14 days when gelatin was incorporated into the growth medium. After production of the proteases, purification and characterisation of the enzymes was performed. Purification of the enzymes was performed by acetone precipitation followed by ultrafiltration with 50 kDa and 30 kDa cut off membrane filters. A final purification fold of approximately 37.6 was achieved. Unusual yields of above 100% were observed after each purification step with the final yield achieved being 196% with a final specific activity of 2707 U/mg. SDS-PAGE revealed a protease band of 35 kDa which was also visible on the zymogram at approximately 36 kDa. The zymogram showed clear hydrolysis bands against a blue background after staining with Coomassie Brilliant Blue. Physico-chemical characterisation of the protease revealed its pH optimum to be pH 3.0 and its temperature optimum 68°C. Another peak was observed on the pH profile at pH 7.0. The protease exhibited high thermostability at temperatures 37°C, 80°C as well as 100°C with the enzyme retaining close to 50% of its initial activity after 4 h of exposure to all three temperatures. All ions tested for their effects on the proteases, except Ca2+, enhanced protease activity. Ca2+ did not exhibit any significant effect on the enzyme’s activity while Zn2+ had the highest effect, enhancing enzyme activity by 305%. The proteases, however, were not significantly inhibited by EDTA, a metal chelating agent and a known metalloprotease inhibitor. The enzyme was classified as an aspartic protease due to complete inhibition by 25 μM of pepstatin A, coupled to its low pH optimum of 3.0. Addition of trans-Epoxysuccinyl-L-leucylamido-(4-guanidino)butane (E-64), a cysteine protease inhibitor, and 2-mercaptoethanol increased protease activity. The proteases exhibited a narrow substrate specificity towards gelatin and no other substrate. Substrate kinetics values were plotted on a Michaelis-Menten Graph and showed that the enzyme had a Vmax of 55.25 U/ml and a Km of 2.7 mg/ml gelatin. A low Km indicated that the protease had a high affinity for gelatin. Silver recovery studies from X-ray film revealed the proteases’ capability to remove silver from X-ray film, leaving the film intact. The recovery of silver was perceived visually, by film observation, as well as by scan electron microscopy (SEM) images, where clearance of the film was observed after incubation with the enzyme. Energy dispersive X-ray spectroscopy (EDS) profiles also confirmed removal of silver from the film, with a Ag peak showing on the profile of the film before treatment with the proteases and no peak after treatment. The crude protease sample was, however, catalytically more efficient compared to the partially purified sample. , Thesis (MSc) -- Faculty of Science, Biochemistry and Microbiology, 2018
- Full Text:
- Date Issued: 2018
- Authors: Manyumwa, Colleen Varaidzo
- Date: 2018
- Subjects: Ascomycetes , Mycorrhizal fungi , Ericaceae , Proteolytic enzymes , Silver Recycling
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/62833 , vital:28298
- Description: The aim of this study was to produce, purify and characterise proteases from the ericoid mycorrhizal fungus, Oidiodendron maius (CafRU082b/KP119480), as well as to explore their potential application in the recovery of silver from X-ray film. Firstly, the growth of the ericoid mycorrhizal fungus, Oidiodendron maius (CafRU082b), was studied, and its ability to produce proteolytic enzymes was investigated. O. maius proved to grow well in the dark, submerged in Modified Melin Norkran’s liquid medium at a pH of 5 and at 25°C. Pure cultures of the fungus were maintained on Potato Dextrose Agar (PDA). The fungus grew on PDA plates containing different substrates including haemoglobin, casein, gelatin as well as azocasein. Zones of clearance, however, were only observed on plates containing gelatin after treatment with mercuric chloride, HgCl2. Proteases were successfully produced after 14 days when gelatin was incorporated into the growth medium. After production of the proteases, purification and characterisation of the enzymes was performed. Purification of the enzymes was performed by acetone precipitation followed by ultrafiltration with 50 kDa and 30 kDa cut off membrane filters. A final purification fold of approximately 37.6 was achieved. Unusual yields of above 100% were observed after each purification step with the final yield achieved being 196% with a final specific activity of 2707 U/mg. SDS-PAGE revealed a protease band of 35 kDa which was also visible on the zymogram at approximately 36 kDa. The zymogram showed clear hydrolysis bands against a blue background after staining with Coomassie Brilliant Blue. Physico-chemical characterisation of the protease revealed its pH optimum to be pH 3.0 and its temperature optimum 68°C. Another peak was observed on the pH profile at pH 7.0. The protease exhibited high thermostability at temperatures 37°C, 80°C as well as 100°C with the enzyme retaining close to 50% of its initial activity after 4 h of exposure to all three temperatures. All ions tested for their effects on the proteases, except Ca2+, enhanced protease activity. Ca2+ did not exhibit any significant effect on the enzyme’s activity while Zn2+ had the highest effect, enhancing enzyme activity by 305%. The proteases, however, were not significantly inhibited by EDTA, a metal chelating agent and a known metalloprotease inhibitor. The enzyme was classified as an aspartic protease due to complete inhibition by 25 μM of pepstatin A, coupled to its low pH optimum of 3.0. Addition of trans-Epoxysuccinyl-L-leucylamido-(4-guanidino)butane (E-64), a cysteine protease inhibitor, and 2-mercaptoethanol increased protease activity. The proteases exhibited a narrow substrate specificity towards gelatin and no other substrate. Substrate kinetics values were plotted on a Michaelis-Menten Graph and showed that the enzyme had a Vmax of 55.25 U/ml and a Km of 2.7 mg/ml gelatin. A low Km indicated that the protease had a high affinity for gelatin. Silver recovery studies from X-ray film revealed the proteases’ capability to remove silver from X-ray film, leaving the film intact. The recovery of silver was perceived visually, by film observation, as well as by scan electron microscopy (SEM) images, where clearance of the film was observed after incubation with the enzyme. Energy dispersive X-ray spectroscopy (EDS) profiles also confirmed removal of silver from the film, with a Ag peak showing on the profile of the film before treatment with the proteases and no peak after treatment. The crude protease sample was, however, catalytically more efficient compared to the partially purified sample. , Thesis (MSc) -- Faculty of Science, Biochemistry and Microbiology, 2018
- Full Text:
- Date Issued: 2018
Prospects for biological control of cactus weeds in Namibia
- Paterson, Iain D, Manheimmer, C A, Zimmermann, H C
- Authors: Paterson, Iain D , Manheimmer, C A , Zimmermann, H C
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417522 , vital:71460 , xlink:href="https://doi.org/10.1080/09583157.2018.1562040"
- Description: Australia and South Africa have a long history of sharing successful biocontrol agents for cactus weeds but other countries, such as Namibia, could also benefit. There are four biological control agents that are widely utilised in South Africa and/or Australia for the control of 10 invasive alien Cactaceae in Namibia.
- Full Text:
- Date Issued: 2018
- Authors: Paterson, Iain D , Manheimmer, C A , Zimmermann, H C
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417522 , vital:71460 , xlink:href="https://doi.org/10.1080/09583157.2018.1562040"
- Description: Australia and South Africa have a long history of sharing successful biocontrol agents for cactus weeds but other countries, such as Namibia, could also benefit. There are four biological control agents that are widely utilised in South Africa and/or Australia for the control of 10 invasive alien Cactaceae in Namibia.
- Full Text:
- Date Issued: 2018
Pyridone substituted phthalocyanines: Photophysico-chemical properties and TD-DFT calculations
- Abdurrahmanoğlu, Şaziye, Canlica, Mevlüde, Mack, John, Nyokong, Tebello
- Authors: Abdurrahmanoğlu, Şaziye , Canlica, Mevlüde , Mack, John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188216 , vital:44735 , xlink:href="https://doi.org/10.1142/S1088424617500730"
- Description: 4-(6-methyl-3-nitro-2-oxo-1,2-dihydropyridin-4-yloxy)phthalonitrile has been used to prepare a novel Zn(II) phthalocyanines with four peripheral pyridone substituents. The compound has been characterized by UV-visible absorption, FT-IR and 11H-NMR spectroscopy, elemental analysis and MALDI-TOF mass spectroscopy. The fluorescence, triplet quantum and singlet oxygen quantum yields have been determined and TD-DFT calculations have been used to identify trends in the electronic structure.
- Full Text:
- Date Issued: 2018
- Authors: Abdurrahmanoğlu, Şaziye , Canlica, Mevlüde , Mack, John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188216 , vital:44735 , xlink:href="https://doi.org/10.1142/S1088424617500730"
- Description: 4-(6-methyl-3-nitro-2-oxo-1,2-dihydropyridin-4-yloxy)phthalonitrile has been used to prepare a novel Zn(II) phthalocyanines with four peripheral pyridone substituents. The compound has been characterized by UV-visible absorption, FT-IR and 11H-NMR spectroscopy, elemental analysis and MALDI-TOF mass spectroscopy. The fluorescence, triplet quantum and singlet oxygen quantum yields have been determined and TD-DFT calculations have been used to identify trends in the electronic structure.
- Full Text:
- Date Issued: 2018
Quantitation of zolpidem in biological fluids by electro-driven microextraction combined with HPLC-UV analysis
- Yaripour, Saeid, Mohammadi, Ali, Esfanjani, Isa, Walker, Roderick B, Nojavan, Saeed
- Authors: Yaripour, Saeid , Mohammadi, Ali , Esfanjani, Isa , Walker, Roderick B , Nojavan, Saeed
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184723 , vital:44266 , xlink:href="http://dx.doi.org/10.17179/excli2018-1140"
- Description: In this study, for the first time, an electro-driven microextraction method named electromembrane extraction combined with a simple high performance liquid chromatography and ultraviolet detection was developed and validated for the quantitation of zolpidem in biological samples. Parameters influencing electromembrane extraction were evaluated and optimized. The membrane consisted of 2-ethylhexanol immobilized in the pores of a hollow fiber. As a driving force, a 150 V electric field was applied to facilitate the analyte migration from the sample matrix to an acceptor solution through a supported liquid membrane. The pHs of donor and acceptor solutions were optimized to 6.0 and 2.0, respectively. The enrichment factor was obtained >75 within 15 minutes. The effect of carbon nanotubes (as solid nano-sorbents) on the membrane performance and EME efficiency was evaluated. The method was linear over the range of 10-1000 ng/mL for zolpidem (R2 >0.9991) with repeatability (%RSD) between 0.3 % and 7.3 % (n = 3). The limits of detection and quantitation were 3 and 10 ng/mL, respectively. The sensitivity of HPLC-UV for the determination of zolpidem was enhanced by electromembrane extraction. Finally, the method was employed for the quantitation of zolpidem in biological samples with relative recoveries in the range of 60-79 %.
- Full Text:
- Date Issued: 2018
- Authors: Yaripour, Saeid , Mohammadi, Ali , Esfanjani, Isa , Walker, Roderick B , Nojavan, Saeed
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184723 , vital:44266 , xlink:href="http://dx.doi.org/10.17179/excli2018-1140"
- Description: In this study, for the first time, an electro-driven microextraction method named electromembrane extraction combined with a simple high performance liquid chromatography and ultraviolet detection was developed and validated for the quantitation of zolpidem in biological samples. Parameters influencing electromembrane extraction were evaluated and optimized. The membrane consisted of 2-ethylhexanol immobilized in the pores of a hollow fiber. As a driving force, a 150 V electric field was applied to facilitate the analyte migration from the sample matrix to an acceptor solution through a supported liquid membrane. The pHs of donor and acceptor solutions were optimized to 6.0 and 2.0, respectively. The enrichment factor was obtained >75 within 15 minutes. The effect of carbon nanotubes (as solid nano-sorbents) on the membrane performance and EME efficiency was evaluated. The method was linear over the range of 10-1000 ng/mL for zolpidem (R2 >0.9991) with repeatability (%RSD) between 0.3 % and 7.3 % (n = 3). The limits of detection and quantitation were 3 and 10 ng/mL, respectively. The sensitivity of HPLC-UV for the determination of zolpidem was enhanced by electromembrane extraction. Finally, the method was employed for the quantitation of zolpidem in biological samples with relative recoveries in the range of 60-79 %.
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- Date Issued: 2018