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Faculty of Applied Sciences

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    Interstitial Fe in MgO
    (AIP Publishing, 2014-01) Mølholt, Torben Esmann; Mantovan, R.; Gunnlaugsson, H.P.; Svane, A.; Masenda, Hilary; Naidoo, D.; Bharuth-Ram, Krish; Fanciulli, M.; Gíslason, H.P.; Johnston, K.; Langouche, G.; Ólafsson, S.; Sielemann, R.; Weyer, G.
    Isolated Fe-57 atoms were studied in MgO single-crystals by emission Mossbauer spectroscopy following implantation of Mn-57 decaying to Fe-57. Four Mossbauer spectral components were found corresponding to different Fe lattice positions and/or charge states. Two components represent Fe atoms substituting Mg as Fe2+ and Fe3+, respectively; a third component is due to Fe in a strongly implantation-induced disturbed region. The fourth component, which is the focus of this paper, can be assigned to Fe at an interstitial site. Comparison of its measured isomer shift with ab initio calculations suggests that the interstitial Fe is located on, or close to, the face of the rock-salt MgO structure. To harmonize such an assignment with the measured near-zero quadrupole interaction a local motion process (cage motion) of the Fe has to be stipulated. The relation of such a local motion as a starting point for long range diffusion is discussed.
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    Gunnera perpensa L.: A multi-use ethnomedicinal plant species in South Africa
    (Taylor and Fancis, 2016) Mammo, Fitsum K.; Mohanlall, Viresh; Shode, Francis O.
    Gunnera perpensa L. is a medicinal plant used in many parts of South Africa to treat several human ailments. G. perpensa is inherited from and linked to the Siswati, Changana, Sotho, Venda, Shona, Tsonga, and Zulu traditional healing systems, particularly in South African provinces where the plant species is still found in the wild. G. perpensa is declining considerably throughout its natural habitat due to over-exploitation of the plant for its medicinal uses. This review aims to gather the fragmented information on the past and present ethnomedicinal uses, phytochemistry and pharmacological properties of G. perpensa.
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    Sulfonic acid functionalized boron nitride nano materials as a microwave-assisted efficient and highly biologically active one-pot synthesis of piperazinyl-quinolinyl fused Benzo[c]acridine derivatives
    (Elsevier, 2017) Murugesan, Arul; Gengan, Robert Moonsamy; Anand, Krishnan
    Boron nitride nano material based solid acid catalyst was found to be an efficient and reusable sulfonic acid catalyst for the synthesis of one-pot Knoevenagel and Michael type reactions in 3, 3-dimethyl-9-(2-(4-methylpiperazin-1-yl) quinolin-3-yl)-3, 4, 9, 10-tetrahydroacridin-1(2H)-one derivatives under mi-crowave irradiation conditions. The catalyst was prepared by mixing boron nitrile and (3-mercaptopropyl) trimethoxysilane. This is simple and safe method for the preparation of solid acid catalysts. The morphological properties of catalyst determined by using FT-IR, XRD, TEM, SEM and Raman spectroscopy. The synthesised catalyst was employed in Knoevenagel and Michael type reactions to synthesise novel piperazinyl-quinolinyl based acridine derivatives. Furthermore the newly-synthesised compounds have been used for molecular docking in DNA binding studies. The method developed in this study has the advantages of good yield, simplicity coupled with safety and short reaction time. Most importantly it was found that the solid acid catalyst can be recycled with only 5% loss of activity.
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    Design, synthesis, anticancer, antimicrobial activities and molecular docking studies of novel quinoline bearing dihydropyridines
    (Elsevier, 2016) Nkosi, S'busiso Mfan'vele; Anand, Krishnan; Anandakumar, S.; Singh, Sanil; Chuturgoon, Anil A.; Gengan, Robert Moonsamy
    A new series of eight quinoline bearing dihydropyridine derivatives (A1–A8) were synthesized in high yield and in short reaction time by a four component reaction of 2-chloro-3-fomyl quinoline, malononitrile, arylamines and dimethyl acetylenedicarboxylate in the presence of a catalytic amount of triethylamine. The compounds were fully characterized by IR, NMR and GC–MS. These compounds were screened for potential biological activity in an A549 lung cancer cell line and were also evaluated for their antibacterial activities against Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 29213 whilst their molecular docking properties in an enzymatic system were also determined. Compounds A2, A3, A4 and A8 showed anti-proliferative activity; with A4 having the highest toxicity at 250 μg/mL and A8 has high toxicity at 125, 250 and 500 μg/mL, respectively. Antibacterial results indicated that A4 have significant activity against tested microorganisms at the minimum inhibitory concentration (MIC) values of 32 μg/mL against Pseudomonas aeruginosa and Escherichia coli,and 16μg/mL against Staphylococcus aureus. Docking of A1 with human mdm2 indicated the lowest binding energy (−6.111 Kcal/mol) thereby showing strong affinity of the ligand molecule with the receptor which has been stabilized by strong hydrogen bond interactions in the binding pocket. This confirms that A1 is a better inhibitor for E3 ubiquitin-protein ligase mdm2.
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    Influence of epoxy group in 2-pyrrolidonium ionic liquid interactions and thermo-physical properties with Ethanoic or Propanoic acid at various temperatures
    (ACS Publications, 2016) Vasanthakumar, Arumugam; Redhi, Gan G.; Gengan, Robert Moonsamy
    In this present study, the interaction between a carboxylic acid and ionic liquids, in terms of their binary mixtures and corresponding thermo-physical properties, was investigated. Here, the novel ionic liquid (IL) [EPMpyr]+[Cl]− was synthesized, and it has been mixed with ethanoic or propanoic acids. The influence of the epoxy group in this ionic liquid was more strongly affected with the acids, and their physicochemical properties at varied temperatures are discussed in term of density (ρ), viscosity (η), speed of sound (u), and refractive index (n) measurements. The density (ρ), speed of sound (u), viscosity (η), and refractive index (n) of the IL, ethanoic acid, propanoic acid, and their corresponding binary mixtures {[([EPMpyr]+[Cl]− (1) + ethanoic or propanoic acid (2)} have been measured at T = (293.15–313.15) K and at P = 0.1 MPa. The theoretical thermodynamic properties of excess molar volumes (VmE), isentropic compressibility (ks), deviation in isentropic compressibility (Δks), and intermolecular free length (Lf) are calculated using experimental density and speed of sound data. The VmE and Δks values for both binary mixtures were found to be negative over the entire mole fraction range of composition at all the investigated temperatures. These results suggest the existence of specific interactions between components in the molecules. The experimental data could be helpful to understand the molecular interactions between the IL and carboxylic acid combinations. The experimental data were fitted to the Redlich–Kister polynomial equation.
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    Cobalt boron nitride : a novel heterogeneous catalyst for the synthesis of medicinally important α-amino quinoline phosphonates
    (Taylor and Fancis, 2016) Sureshkumar, M; Anand, Krishnan; Muthu, T.; Gengan, Robert Moonsamy
    A novel cobalt supported on boron nitride (CoBNT) heterogeneous catalyst for the synthesis of α-amino quinoline phosphonates (AQPs) is reported in the present work. The CoBNT was synthesised by simply mix-ing boron nitride in a solution of cobalt acetate, under an inert atmosphere for 7 d followed by filtration; the yield was 94%. It exhibited excellent catalytic properties for the synthesis of 16 novel AQPs in a one pot mixture containing 2-methoxy 3-formyl quinoline, aniline derivatives and diethyl phosphite. Reactions were rapid, products were easily worked-up and were obtained in more than 90% yield. The CoBNT also exhibited higher catalytic activity than conventional catalysts and was re-used five times without significant decrease in catalytic activity.
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    Biosynthesis of palladium nanoparticles by using Moringa oleifera flower extract and their catalytic and biological properties
    (Elsevier, 2016) Anand, Krishnan; Tiloke, Charlette; Phulukdaree, Alisa; Ranjan, B.; Chuturgoon, Anil A.; Singh, S.; Gengan, Robert Moonsamy
    The biosynthesis of nanostructured biopalladium nanoparticles (PdNPs) from an aqueous solution of crystalline palladium acetate is reported. For the synthesised PdNPs in solution, an agroforest biomass waste petal of Moringa oleifera derived bis-phthalate was used as natural reducing and biocapping agents. Continuous absorp-tion in the UV region and subsequent brown colour change confirmed the formation of PdNPs. A strong surface plasmon peak for PdNPs occurred at 460 nm. PdNPs were characterized by SEM with EDX, FTIR, TEM and DLS. The chemical composition of the aqueous extract was determined by GC–MS coupled with FTIR and 1NMR. The cat-alytic degradation effect by PdNPs on industrial organic toxic effluents p-nitrophenol (PNP) and methylene blue dye was monitored by UV Spectroscopy. On the other hand PdNPs catalysed the base mediated suzuki coupling reaction for biphenyl synthesis, in water. Moreover, PdNPs were found to be reusable catalysts. Toxicity studies of PdNPs showed that the death of brine shrimp to be b50%. Therefore, PdNPs displayed potential for further anti-cancer studies via tumour cell lines. The in vitro cytotoxicity evaluation of the extract capped nanoparticles was carried out using human lung carcinoma cells (A549) and peripheral lymphocytes normal cells by MTT cell via-bility assay. Also, PdNPs showed antibacterial activity against Enterococcus faecalis among the different tested strains, including Bacillus cereus, Staphylococcus aureus, Esherichia coli and Candida albicans, Candida utilis.
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    Cervical cytology as a diagnostic tool for female genital schistosomiasis : correlation to cervical atypia and Schistosoma polymerase chain reaction
    (Cytopathology Foundation Inc with Wolters Kluwer, 2016-04-20) Pillay, Pavitra; van Lieshout, Lisette; Taylor, Myra; Sebitloane, Motshedisi; Zulu, Siphosenkosi Gift; Kleppa, Elisabeth; Roald, Borghild; Kjetland, Eyrun Floerecke
    Background: Female genital schistosomiasis (FGS) is a tissue reaction to lodged ova of Schistosoma haematobium in the genital mucosa. Lesions can make the mucosa friable and prone to bleeding and discharge. Women with FGS may have an increased risk of HIV acquisition, and FGS may act as a cofactor in the development of cervical cancer. Objectives: To explore cytology as a method for diagnosing FGS and to discuss the diagnostic challenges in low-resource rural areas. The correlation between FGS and squamous cell atypia (SCA) is also explored and discussed. Cytology results are compared to Schistosoma polymerase chain reaction (PCR) in vaginal lavage and urine and in urine microscopy. Materials and Methods: In a clinical study, 394 women aged between 16 and 23 years from rural high schools in KwaZulu-Natal, South Africa, underwent structured interviews and the following laboratory tests: Cytology Papanicolaou (Pap) smears for S. haematobium ova and cervical SCA, real-time PCR for Schistosoma-specific DNA in vaginal lavage and urine samples, and urine microscopy for the presence of S. haematobium ova. Results: In Pap smears, S. haematobium ova were detected in 8/394 (2.0%). SCA was found in 107/394 (27.1%), seven of these had high-grade squamous intraepithelial lesion (HSIL). Schistosoma specific DNA was detected in 38/394 (9.6%) of vaginal lavages and in 91/394 (23.0%) of urines. Ova were found microscopically in 78/394 (19.7%) of urines. Conclusion: Schistosoma PCR on lavage was a better way to diagnose FGS compared to cytology. There was a significant association between S. haematobium ova in Pap smears and the other diagnostic methods. In low-resource Schistosoma-endemic areas, it is important that cytology screeners are aware of diagnostic challenges in the identification of schistosomiasis in addition to the cytological diagnosis of SCA. Importantly, in this study, three of eight urines were negative but showed Schistosoma ova in their Pap smear, and one of them was also negative for Schistosoma DNA in urine. In this study, SCA was not significantly associated with schistosomiasis. HSIL detected in this young population might need future consideration.
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    Emission Mössbauer spectroscopy study of fluence dependence of paramagnetic relaxation in Mn/Feimplanted ZnO
    (Springer International Publishing Switzerland, 2016-02-22) Masenda, Hilary; Geburt, S.; Bharuth-Ram, Krish; Naidoo, D.; Gunnlaugsson, H. P.; Johnston, K.; Mantovan, R.; Mølholt, Torben Esmann; Ncube, M.; Shayestehaminzadeh, S.; Gíslason, H. P.; Langouche, G.; Ólafsson, S.; Ronning, C.
    Emission Mössbauer Spectroscopy following the implantation of radioactive precursor isotope 57Mn+ (T 1/2= 1.5 min) into ZnO single crystals at ISOLDE/CERN shows that a large fraction of 57Fe atoms produced in the 57Mn beta decay is created as paramagnetic Fe3+ with relatively long spin-lattice relaxation times. Here we report on ZnO pre-implanted with 56Fe to fluences of 2×1013, 5×10 13 and 8 × 1013 ions/cm2 in order to investigate the dependence of the paramagnetic relaxation rate of Fe3+ on fluence. The spectra are dominated by magnetic features displaying paramagnetic relaxation effects. The extracted spin-lattice relaxation rates show a slight increase with increasing ion fluence at corresponding temperatures and the area fraction of Fe3+ at room temperature reaches a maximum contribution of 80(3)% in the studied fluence range.
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    The effect of mutations near the T1 copper site on the biochemical characteristics of the small laccase from Streptomyces coelicolor A3(2)
    (Elsevier, 2015) Prins, Alaric; Kleinsmidt, L.; Khan, Nuraan; Kirby, Bronwyn; Kudanga, Tukayi; Vollmer, Jannik; Pleiss, Juergen; Burton, Stephanie; Le Roes-Hill, Marilize
    tBacterial laccases show low activities but can be of biotechnological interest due to industrially suit-able characteristics such as thermostability and tolerance to alkaline pH. In this study, three separatemutations (M298F, V290N and V290A) were introduced at or near the T1 copper site of the small lac-case (SLAC) from Streptomyces coelicolor A3(2) and biochemical properties were assessed in comparisonwith the native enzyme. The mutation, V290N showed approximately double the activity of SLAC whenABTS was used as substrate while the specific activity of SLAC-M298F was 4–5 times higher than that ofSLAC when the assays were performed at ≥70◦C. There was no significant difference in activity with 2,6-dimethoxyphenol (2,6-DMP); however, there was a significant shift in the optimal pH from pH 9.5 (SLAC)to 7.5 (SLAC-V290N). Optimal temperature for activity was not significantly altered but thermostabilitywas reduced in all three mutants. The substrate range of the mutant variants remained largely unchanged,with the exception of SLAC-M298F which was unable to oxidise veratryl alcohol. Interestingly, the “typ-ical” laccase inhibitor, sodium azide, had no significant inhibitory effect on the activity of SLAC-M298F,which also exhibited increased resistance to inhibition by sulfhydryl compounds. SLAC-V290N showedhigher catalytic efficiency for 2,6-DMP (kcat/Km= 2.226 mM−1s−1) and ABTS (kcat/Km= 1.874 mM−1s−1)compared to SLAC (kcat/Km= 1.615 mM−1s−1for 2,6-DMP and kcat/Km= 1.611 mM−1s−1for ABTS). Thisstudy has shown that three ligands that are closely associated with the T1 copper in SLAC play a key rolein maintaining enzymatic activity. Whilst the introduction of mutations at these sites negated favourablecharacteristics such as thermostability, several favourable effects were observed. This study has alsoextended the knowledge base on the biochemical characteristics of SLAC, and its suitability as a templatefor engineering with the aim of widening its potential range of industrial applications.