Faculty of Applied Sciences
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Item Interaction studies of nanomaterials with plasma protein using experimental and computational methods(2018) Sabela, Myalowenkosi Innocent; Bisetty, Krishna; Sagrado, Salvador; Mwakikunga, B.Nanomaterials have received considerable attention due to their unique physicochemical properties and various applications. The present study attempts to fill in the knowledge gaps by investigating the synthesis, stability, antimicrobial, and antioxidant properties, along with their sensing capabilities. For this purpose, chemical and green methods were used to synthesise silver nanoparticles, titanium dioxide nanomaterials and zinc oxide nanoparticles. For the chemical synthesis, bio-discrimination of macromolecules were investigated by calorimetric methods. Whereas for green synthesis, silver nanoparticles and zinc oxide nanoparticles were synthesized using plant extracts and tested for cytotoxicity and antioxidant properties followed by the electrochemical sensing of silymarin. The synthesized nanomaterials were analyzed by high-resolution transmission electron microscopy, X-ray diffraction, photoluminescence, fourier transform infrared spectroscopy, thermogravimetric analyzer, dynamic light scattering and zeta potential analyzer to better understand the morphology and capping. In addition, computational modelling techniques were implemented to assess the adsorption and interaction of nanomaterial with biomolecules through docking. The results arising from this work are presented in a case-study fashion ranging from colorimetry, protein- nanomaterial interactions through to biosynthesis. For the colorimetric discrimination an extensive literature survey revealed that silver nanoparticles and gold nanoparticles based colorimetric assays, are widely used for screening in biosciences and metal analysis. A detailed review of colorimetric-based assays and identification of the fundamental parameters that influences such strategies are presented in this work. Accordingly, colorimetric discrimination of bovine serum albumin, lysozyme, single-stranded deoxyribonucleic acid, double-stranded deoxyribonucleic acid, and polynucleotides using silver nanoparticles was performed. This work demonstrates the importance of the starting material for colorimetric measurements preferably, with particles that are active in a wider absorbance region. Furthermore, an in-depth statistical analysis of the colorimetric data using principal component analysis provided a framework for sensing of the selected proteins, deoxyribonucleic acid, and polynucleotides by simultaneously varying the concentration of a salt and biomacromolecules from 10 to 100 mM and from 0.1 to 10 µg mL-1 respectively. In the case of the protein-nanomaterial interaction, the bioconjugate formation was studied between human serum albumin and TiO2 nanostructures. The TiO2 nanostructures were prepared by microwave assisted calcination at 200, 400, 700, and 900 °C. The results revealed that calcination above 400 °C had a significant impact on the surface of the nanomaterial, resulting in a lower surface adsorption of the protein confirmed by characterization techniques mentioned above. To further elucidate interactions between human serum albumin and titanium dioxide nanostructures, computational molecular docking studies were performed, resulting in the characteristic shapes of TiO2 nanostructures correlating well with the experimental observations. The nanowires and nanotubes showed the much greater binding energy of –2.33 Kcal mol-1 and -2.85 Kcal mol-1, respectively. In contrast to the nanotubes, the docked conformation of the nanowires showed a greater number of interactions. In regard to the biosynthesis of silver nanoparticles prepared from aqueous plant extracts of Iboza riparia leaf and Ilex Mitis root bark, the formation of nanoparticles were due to the reduction of silver ions caused by electron transfer from the electron rich atoms of the extracts such as saponins and diterpenes. Therefore, relevant cytotoxicity studies were conducted with the MTT assay on HEK293T followed by an antioxidant activity with ABTS. Antimicrobial activity analysis depicted susceptibility of microorganisms in the order of nanoparticles by diterpenes (156 nm) followed by nanoparticles by saponins (50 nm). Another biosynthesis of zinc oxide nanoparticles was performed using the extracts from jacaranda mimosifolia flowers and the carica papaya seeds. The composition of both extracts was analyzed by gas chromatography–mass spectrometry. Oleic acid was found to be the major component in the extract of jacaranda mimosifolia flowers. The microwave assisted biosynthesis of nanoparticles was successfully completed within 5 min resulting in 2–4 nm particle size. Further characterization was performed using the aforementioned instruments. The zinc oxide nanoparticles from jacaranda mimosifolia flowers were used to test the viability of gram-negative Escherichia coli and gram-positive Enterococcus faecium bacteria, which was found to be 48% and 43% respectively. In order to better understand the influence of oleic acid on the size and shape of nanoparticles, its adsorption on the different facets was explored computationally. The preferential passivation of the (101) facet was evident from the concentration profiles with an average distance of 1.4 Å for oleic acid. On the other hand, facets (100) and (002) were located at varying distances of 4 and 9 Å respectively. Overall the results indicated that the presence of oleic acid could drive the preferential growth of zinc oxide nanomaterials to nanorod array and other structures. Furthermore, the composition of the zinc oxide nanoparticles from the carica papaya seed extracts was also identified using the aforementioned techniques. The results highlighted the role of oleic acid as a capping agent for these nanoparticles. In relation to their electrochemical applications, they were also tested for sensing activities of silymarin by incorporating them with multiwalled carbon nanotubes immobilized on the surface of a glassy carbon electrode. The electrochemical signals obtained from the modified electrode was 2-fold higher than that of a bare glassy carbon electrode. The electrode based on zinc oxide nanoparticle was able to detect silymarin in the commercial Milk Thistle tablet.Item Influence of growth locations on physicochemical properties of starch and flour from amadumbe (Colocasia esculenta) genotypes(2017) Mawoyo, Bruce; Amonsou, Eric Oscar; Gerrano, Abe S.Amadumbe commonly, known as taro is a traditionally underutilised tuber crop in Southern Africa. Nutritionally, amadumbe corms contain appreciable levels of carbohydrate mainly in the form of starch which is resistant to digestion. It also contains mucilage, a soluble fibre, which is good for the human digestive health. Thus, amadumbe starch and mucilage can be used as functional ingredients in food formulations. The aim of this research was to investigate the effects of genotypes and growth location on the physicochemical properties of amadumbe flour and starch. Eighteen (18) amadumbe genotypes grown in Roodeplaat, Gauteng and Umbumbulu, Kwazulu-Natal, South Africa, were studied. Roodeplaat received a lower annual average rainfall (514 mm) and high environmental temperature (24oC) compared to Umbumbulu (828 mm, 19oC) during the cropping season. Specifically, the influence of growth location and genotypes on the chemical composition (proximate composition and mineral contents) as well as the functional properties of amadumbe flours were investigated. Furthermore, starch was extracted and its physicochemical and functional properties were also studied. The carbohydrate contents (73-81%) of amadumbe flours were substantially high and varied with growth location. Mucilage contents (6-9%) were very low across genotypes in both locations. Water absorption and oil absorption capacities positively correlated to carbohydrates and mucilage in the flour irrespective of growth locations. Swelling power and solubility index was influenced by the amylose content of the flour. Genotype and growth location significantly affected the pasting properties of amadumbe flour. The pasting temperature was very high (approx. 90oC) across genotypes in both locations, while peak viscosity differed significantly (54-242 RVU) for genotypes grown in different environments. The amylose contents (0-14.4%) of amadumbe starches were low and varied significantly with growth location and among genotypes. Three genotypes, G2, G20, and G21 grown in Roodeplaat lacked amylose. Amadumbe starches showed reflective peaks at 2θ=15o and doublet at 17o, 18o and 24o typical of A-type starches. Amadumbe genotypes had small sized (1-5 µm) and polygonal starch granules. Functional properties including water absorption, swelling power, gelatinisation temperature and peak viscosity significantly positively correlated with amylose content. These findings further suggest that water availability could have a major effect on starch synthesis as the two locations received a different amount of rainfall during the growing season. Findings from this study are important for future improvement programmes and selection of appropriate genotypes for industrial production or food application of amadumbe flour and starch.Item Study of interaction between polyphenolic compounds and protein using computational and capillary electrophoresis techniques(2013-07-30) Sabela, Myalowenkosi Innocent; Bisetty, KrishnaThe present work involves the interaction studies of chiral compounds with the Human Serum Albumin (HSA) protein using computational and experimental methods. The HSA protein has multiple binding sites that forms the basis for its exceptional ability to interact with many organic and inorganic molecules, which makes this protein an important regulator of intercellular fluxes and the pharmacokinetic behaviour of many drugs. This study was undertaken to evaluate the related pharmacokinetic and enantioselective binding parameters of the racemic catechin enantiomers with the HSA. Accordingly, this work involved a method development for the chiral separation of a racemic compound, by capillary electrophoresis-electrokinetic chromatography (CE-EKC) with a highly sulphated beta-cyclodextrin (HS--CD) as a chiral selector. The experimental work was supported by two molecular docking studies. The first included the mimicking of the host-guest interactions between a chiral selector and an enantiomeric compound. The second study included the estimation of the pseudo enantioselective (ES) binding of catechin to HSA. Overall, it was found that CE-EKC is the preferred method for the(±)-catechin binding to HSA protein evaluation. Moreover, the technique used in this work is not restricted to HSA or polyphenols, but can also be applied to other proteins and ligands that possess chirality. Furthermore, the molecular docking approaches also proved to be very useful for the evaluation of chiral recognition systems and for elucidation of the ligand-protein interactions.Item Correlation and prediction of the physical and excess properties of the ionic liquid 1-butyl-3-methylimidazolium methyl sulphate with several alcohols at T= (298.15 to 313.15) K(2013-07-30) Singh, Sangeeta; Deenadayalu, NirmalaThe thermodynamic properties of binary liquid mixtures using an ionic liquid (IL) with alcohols were determined at different temperatures. The ionic liquid used was 1-butyl-3- methylimidazolium methylsulphate [BMIM]+[MeSO4]-. Densities, speed of sound, and refractive indices for the binary mixtures ([BMIM]+[MeSO4]- + methanol, or 1-propanol, or 2-propanol, or 1-butanol) were experimentally measured over the whole range of composition at T = (298.15, E 303.15, 308.15, and 313.15) K. From the experimental data, excess molar volumes, V m , E , deviations in refractive isentropic compressibilities, κ s , excess isentropic compressibilities, κ S indices, ∆n, and molar refractions, R, were calculated. The excess partial molar volumes were also calculated at T = 298.15 K. For the binary systems, ([BMIM]+[MeSO4]- + methanol, or 1-propanol, or 2-propanol, or E E E 1-butanol) V m and κ S are always negative and V m decrease slightly when the temperature increases. The refractive index deviation at T = (298.15, 303.15, 308.15, and 313.15) K is positive over the whole composition range. The measured negative values for excess molar volume of these mixtures ([BMIM]+[MeSO4]- + methanol, or 1-propanol, or 2-propanol, or 1-butanol) indicate strong ion-dipole interactions and packing between alcohols and IL are present. The Redlich-Kister smoothing polynomial equation was satisfactorily applied for the E E fitting of the V m , κ S , and ∆n data to give the fitting parameters and the root-mean-square deviations. The Lorentz-Lorenz (L-L) equation was also used to correlate the volumetric property and predict the density or refractive index of the binary mixtures of ionic liquid and the organic solvents. The Lorentz-Lorenz approximation gives a higher σ when used to correlate the iiiexcess molar volumes for the mixtures ([BMIM]+[MeSO4]- + methanol, or 1-propanol, or 2-propanol, or 1-butanol). The L-L equation gives good results for the prediction of density and refractive index. The results are discussed in terms of solute-solute, solute-solvent and solvent- solvent interactions.Item Excess molar volumes and partial molar volumes for (propionitrile + an alkanol) at T = 298.15 K and p = 0.1 MPa(Elsevier, 2006) Deenadayalu, Nirmala; Bhujrajh, P.The excess molar volumes and the partial molar volumes for (propionitrile + an alkanol) at T = 298.15 K and at atmospheric pressure are reported. The hydrogen bonding between the OH NC groups are discussed in terms of the chain length of the alkanol. The alkanols studied are (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 1-pentanol). The excess molar volume data was fitted to the Redlich–Kister equation The partial molar volumes were calculated from the Redlich–Kister coefficients.Item Ternary excess molar volumes of {methyltrioctylammonium bis(trifluoromethylsulfonyl)imide + ethanol + methyl acetate, or ethyl acetate} systems at T = (298.15, 303.15, and 313.15) K(Elsevier, 2010-01-28) Gwala, Nobuhle V.; Deenadayalu, Nirmala; Tumba, Kaniki; Ramjugernath, DereshThe activity coefficient at infinite dilution for 30 solutes: alkanes, alkenes, cycloalkanes, alkynes, ketones, alcohols, and aromatic compounds was determined from gas–liquid chromatography (glc) measurements at three temperatures (303.15, 313.15, and 323.15) K. The ionic liquid: trioctylmethylammonium bis(trifluoromethylsulfonyl)imide, was used as the stationary phase. For each temperature, values were determined using two columns with different mass percent packing of the ionic liquid. The selectivity value was calculated from the to determine the suitability of the solvent as a potential entrainer for extractive distillation in the separation of an hexane/benzene mixture, indicative of a typical industrial separation problem for benchmarking purposes.Item Application of the extended real associated solution theory to excess molar enthalpies and excess molar volumes of binary mixtures of (benzene or 1-alkanol + quinoline)(Elsevier, 2005-06-01) Deenadayalu, Nirmala; Letcher, Trevor M.Excess molar enthalpies and excess molar volumes of binary mixtures of (benzene or methanol or ethanol or 1-propanol or 1- butanol+quinoline) as a function of composition at a pressure of 1 atm and a temperature of 298.15 K have been used to test the Extended Real Solution Theory, ERAS, of nonelectrolyte solutions. The ERAS theory accounts for free volume effects according to the Flory–Patterson theory and for association effects: self and crossassociation between the molecules involved. The ERAS theory results for the binary mixtures (benzene or an alkanol+quinoline) indicates strong hydrogen bonding effects between unlike molecules given by the predicted hydrogen bonding energy between two dissimilar compounds. Comparison is also made between the chemical and physical contribution to the ERAS theory. The Extended Real Associated Solution theory describes the published Vm E data better than the published Hm E data.Item Cibulka correlation for ternary excess molar volumes for [MOA]⁺[Tf₂N]⁻ at different temperatures(2012-08-20) Tywabi, Zikhona; Deenadayalu, NirmalaIn this work, the binary and ternary excess molar volumes have been calculated from the density, ρ, measurements using an Anton Paar (DMA 38) vibrating tube digital densimeter. One component of the ternary systems studied was an ionic liquid. The ionic liquid used is methyl trioctylammonium bis(trifluoromethylsulfonyl)imide [MOA]+[Tf2N]-. Binary excess molar volumes were obtained for (1-butanol + ethyl acetate) and (2-butanol + ethyl acetate) systems at T = (298.15, 303.15, and 313.15) K. Ternary excess molar volumes were obtained for the mixtures {[MOA]+[Tf2N]- + 2-propanol or 1-butanol or 2-butanol + ethyl acetate} at T = (298.15, 303.15, and 313.15) K. The Redlich-Kister equation was fitted to the calculated binary excess molar volume data to obtain the fitting parameters which were used to calculate the partial molar volumes at infinite dilution. The calculated partial molar volume was used to better understand the intermolecular interactions of each component at infinite dilution. The Redlich-Kister parameters were also used in the Cibulka equation and the Cibulka equation was used to correlate the ternary excess molar volume data to give the fitting parameters. The binary excess molar volumes,VmE , for the (1-butanol + ethyl acetate) and (2-butanol + ethyl acetate) are positive at each temperature over the entire composition range. At high mole fractions of the alcohol for the binary systems (2-propanol or 1-butanol or 2-butanol + ethyl acetate), VmE is positive again, similar to the Cibulka ternary correlation. The positive V E m values are due to the breaking of intermolecular interactions in the pure components during the mixing process. The ternary excess molar volume,V E 123 , values are negative for all mole fractions. The negative values are due to a more efficient packing and/ or attractive intermolecular interactions in the mixtures than in the pure liquid. There is also a contraction in volume which can be attributed to electron-donor-acceptor type interactions between the ionic liquid and 2-propanol or 1-butanol or 2-butanol as well as ethyl acetate.Item Excess molar volume and isentropic compressibility for binary or ternary ionic liquid systems(2010) Bahadur, Indra; Deenadayalu, NirmalaThe thermodynamic properties of mixtures involving ionic liquids (ILs) with alcohols or alkyl acetate or nitromethane at different temperatures were determined. The ILs used were methyl trioctylammonium bis(trifluoromethylsulfonyl)imide ([MOA]+[Tf2N]-) and 1-butyl-3- methylimidazolium methyl sulphate [BMIM]+[MeSO4]-. The ternary excess molar volumes (�������� E ) for the mixtures {methyl trioctylammonium bis (trifluoromethylsulfonyl)imide + methanol or ethanol + methyl acetate or ethyl acetate}and (1-butyl-3-methylimidazolium methylsulfate + methanol or ethanol or 1-propanol + nitromethane) were calculated from experimental density values, at T = (298.15, 303.15 and 313.15) K and T = 298.15, respectively. The Cibulka equation was used to correlate the ternary excess molar volume data using binary data from literature. The �������� E values for both IL ternary systems were negative at each temperature. The negative contribution of �������� E values are due to the packing effect and/or strong intermolecular interactions (ion-dipole) between the different molecules. The density and speed of sound of the binary solutions ([MOA]+[Tf2N]- + methyl acetate or ethyl acetate or methanol or ethanol), (methanol + methyl acetate or ethyl acetate) and (ethanol + methyl acetate or ethyl acetate) were also measured at T = ( 298.15, 303.15, 308.15 and 313.15) K and at atmospheric pressure. The apparent molar volume, Vφ , and the apparent molar isentropic compressibility, κφ , were evaluated from the experimental density and speed of sound data. A Redlich-Mayer type equation was fitted to the apparent molar volume and apparent molar isentropic compressibility data. The results are discussed in terms of solute-solute, solute- solvent and solvent-solvent interactions. The apparent molar volume and apparent molar isentropic compressibility at infinite dilution, ��φ �� and κφ ��, respectively of the binary solutions have been calculated at each temperature. The ��φ �� values for the binary v systems ([MOA]+[Tf2N]- + methyl acetate or ethyl acetate or methanol or ethanol) and (methanol + methyl acetate or ethyl acetate) and (ethanol + methyl acetate or ethyl acetate) are positive and increase with an increase in temperature. For the (methanol + methyl acetate or ethyl acetate) systems ��φ �� values indicate that the (ion-solvent) interactions are weaker. The κφ �� is both positive and negative. Positive κφ ��, for ([MOA] + [Tf2N]- + ethyl acetate or ethanol), (methanol + ethyl acetate) and (ethanol + methyl acetate or ethyl acetate) can be attributed to the predominance of solvent intrinsic compressibility effect over the effect of penetration of ions of IL or methanol or ethanol. The positive κφ �� values can be interpreted in terms of increase in the compressibility of the solution compared to the pure solvent methyl acetate or ethyl acetate or ethanol. The κφ �� values increase with an increase in temperature. Negative κφ ��, for ([MOA] + [Tf2N]- + methyl acetate or methanol), and (methanol + methyl acetate) can be attributed to the predominance of penetration effect of solvent molecules into the intra-ionic free space of IL or methanol molecules over the effect of their solvent intrinsic compressibility. Negative κφ �� indicate that the solvent surrounding the IL or methanol would present greater resistance to compression than the bulk solvent. The φ �� values decrease with an increase in the temperature. The infinite dilution apparent molar expansibility, ��φ �� , values for the binary systems (IL + methyl acetate or ethyl acetate or methanol or ethanol) and (methanol + methyl acetate or ethyl acetate) and (ethanol + methyl acetate or ethyl acetate) are positive and decrease with an increase in temperature due to the solution volume increasing less rapidly than the pure solvent. For (IL + methyl acetate or ethyl acetate or methanol or ethanol) systems ��φ �� indicates that the interaction between (IL + methyl acetate) is stronger than that of the (IL + ethanol) or (IL + methanol) or (IL + ethyl acetate) solution. For the (methanol + methyl acetate or ethyl acetate) systems ��φ �� values vi indicate that the interactions are stronger than (ethanol + methyl acetate or ethyl acetate) systems.Item Excess molar volumes, partial molar volumes and isentropic compressibilities of binary systems (ionic liquid + alkanol)(2009) Sibiya, Precious N.; Deenadayalu, NirmalaThe thermodynamic properties of binary liquid mixtures involving ionic liquids (ILs) with alcohols were determined. ILs are an important class of solvents since they are being investigated as environmentally benign solvents, because of their negligible vapour pressure, and as potential replacement solvents for volatile organic compounds (VOCs) currently used in industries. Alcohols were chosen for this study because they have hydrogen bonding and their interaction with ILs will help in understanding the intermolecular interactions. Also, their thermodynamic properties are used for the development of specific chemical processes. The excess molar volumes of binary mixtures of {1-ethyl-3-methylimidazolium ethylsulfate + methanol or 1-propanol or 2-propanol}, {trioctylmethylammonium bis (trifluoromethyl-sulfonyl) imide + methanol or ethanol or 1-propanol}, {1-buty-3-methylimidazolium methylsulfate + methanol or ethanol or 1-propanol} were calculated from experimental density values, at T = (298.15, 303.15 and 313.15) K. The Redlich-Kister smoothing polynomial was fitted to the excess molar volume data. The partial molar volumes of the binary mixtures {1-ethyl-3-methylimidazolium ethylsulfate + methanol or 1-propanol or 2-propanol}, {trioctylmethylammonium bis (trifluoromethyl-sulfonyl) imide + methanol or ethanol or 1-propanol}, {1-buty-3-methylimidazolium methylsulfate + methanol or ethanol or 1-propanol} were calculated from the Redlich-Kister coefficients, at T = (298.15, 303.15 and 313.15) K. This information was used to better understand the intermolecular interactions with each solvent at infinite dilution. iii The isentropic compressibility of {trioctylmethylammonium bis (trifluoromethyl-sulfonyl) imide + methanol or ethanol or 1-propanol}, were calculated from the speed of sound data at T = 298.15 K.