Department of Chemical Sciences
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- ItemFocus on Glucose: A World of Sugar(Green Chemistry Network, 2008-03-23) Oyetunde, TemidayoExploring the diverse possibilities from sugar as a biomolecular platform
- Itema-Amylase Inhibition, Anti-glycation Property and Characterization of the Binding Interaction of Citric Acid with a-Amylase Using Multiple Spectroscopic, Kinetics and Molecular Docking Approaches(Elsevier, 2022-07-15) Oyetunde, TemidayoThe quest to suppress complications associated with diabetes mellitus is ever increasing, while food additives and preservatives are currently being considered to play additional roles besides their uses in food enhancement and preservation. In the present study, the protective prowess of a common food preservative (citric acid, CA) against advanced glycation end-products (AGEs) formation and its binding interaction mechanism with a-amylase (AMY), an enzyme linked with hyperglycemia management, were examined. Enzyme inhibition kinetics, intrinsic fluorescence, synchronous and 3D fluorescence spectroscopies, ultraviolet–visible (UV–Vis) absorption spectroscopy, Fourier transform-infrared (FT-IR) spectroscopy, thermodynamics, and molecular docking analyses were employed. Results obtained showed that citric acid decreased a-amylase activity via mixed inhibition (IC50 = 5.01 ± 0.87 mM, Kic = 2.42 mM, Kiu = 160.34 mM) and suppressed AGEs formation (IC50 = 0.795 ± 0.001 mM). The intrinsic fluorescence of free a-amylase was quenched via static mechanism with high bimolecular quenching constant (Kq) and binding constant (Ka) values. Analysis of thermodynamic properties revealed that AMY-CA complex was spontaneously formed (DG < 0), entropy driven (TDS > DH), with involvement of electrostatic forces. UV–Vis, FT-IR and 3D fluorescence spectroscopies affirmed alterations in aamylase native conformation due to CA binding interaction. CA interacted with His-101, Asp-197, His- 299, and Glu-233 within AMY active site. Our findings indicated that CA could impair formation of AGEs and interact with a-amylase to slow down starch hydrolysis; vital properties in management of type 2 diabetes complications.
- ItemPrecursor Engineering for the Synthesis of Mixed Anionic Metal (Cu, Mn) Chalcogenide Nanomaterials via Solvent-Less Synthesis(American Chemical Society (ACS), 2022-04-18) Oyetunde, TemidayoMetal−organic ligands with mixed chalcogenides are potential compounds for the preparation of mixed anionic metal chalcogenide alloys. However, only a few of such ligands are known, and their complexes are not well explored. We have prepared homo- and heterodichalcogenoimidodiphosphinate [(EE′PiPr2NH)] (E, E′ = Se, Se; S, S; S, Se) complexes of manganese and copper through metathetical reactions. The X-ray single crystal structure of [Mn{(SePiPr2)2N}2] 1 revealed a triclinic crystal system, with a MnSe4 core unit, whereas the crystal structure determination of [Mn{(SPiPr2)(SePiPr2)N}2] 2 indicated a triclinic crystal system with a Mn(S/Se)2 unit. Both metal centers are tetrahedral, with two deprotonated bidentate ligands forming the coordination sphere. The free ligand was found to exhibit a gauche configuration in the solid state. The energies of the various rotamers of dithio-analogue were studied by DFT calculations. The decomposition behavior of complexes with homo- and heterochalcogenides was investigated, and the complexes were employed as single-source precursors to generate manganese and copper chalcogenides through solvent-less melt reactions between 500 and 550 °C. The deposited powders were characterized by powder X-ray diffraction (p-XRD), scanning electron microscopy (SEM), energy dispersive analysis of X-ray (EDAX), transmission electron microscopy (TEM), and elemental mapping. MnS, MnSe2, and MnSSe phases were obtained from the decomposition of respective manganese complexes. In contrast, the decomposition of copper-based complexes yielded Cu2−xSe and the sulfur-doped Cu3Se2 phase from seleno- and mixed thio/selenocomplexes of Cu, respectively. The morphology ranged from random sheet-like structures to agglomerated platelets, while the selected area electron diffraction (SAED) revealed the crystalline nature of the materials. Depending on the nature of the complex and the temperature, different amounts of phosphorus were present as an impurity in the synthesized products.
- ItemPb/Ca Ion Exchange on Kaolinite Clay Modified with Phosphates(Journal of Soils and Sediments, 2010) Unuabonah, EmmanuelPollution of soils by heavy metal ions has attracted global concern because of the subsequent translocation into food chain which when taken up to a certain level can cause serious health problems. The influence of preadsorbed calcium by kaolinite clay modified with orthophosphate and tripolyphosphate reagents on the mobility of Pb2+ in kaolinitic soil system is studied. This is with the view to understand the fate of Pb2+ in phosphate-fertilized kaolinitic soils that are subsequently limed. Potassium dihydrogen phosphate (98%) and sodium tripolyphosphate (87%) were purchased from Aldrich and Merck, respectively. They were used to modify locally obtained kaolinite clay. These adsorbents were further pretreated with 0.1 M Ca(NO3)2. These phosphate-modified kaolinite clay adsorbents pretreated with Ca2+ were used in the adsorption of Pb2+ from aqueous solution in a batch mode. X-ray diffraction spectra of the various adsorbents indicated that modification of kaolinite clay with the reagents were effective on the surface of the clay mineral and not on the crystal structure of the clay mineral. Treatment with 0.1 M Ca(NO3)2 gave K–Ca (for unmodified kaolinite clay), K–O–Ca (for potassiumdihydrogen-phosphate-modified kaolinite clay), and K– TPP–Ca (for sodium-tripolyphosphate-modified Kaolinite clay) samples. The pHPZC of the adsorbents before pretreatment with Ca2+ decreased when compared with the unmodified kaolinite clay. Further pretreatment of these adsorbents with Ca2+ largely decreased the adsorption capacity of all three adsorbents for Pb2+ from aqueous solution due to the higher reactivity of Ca2+ compared with Pb2+. Data from all three adsorbents failed the nonlinear single Langmuir model fit while data from K–O–Ca adsorbent failed the competitive Langmuir model fit. ΔSo data were used to support the proposed structures of adsorbed Pb2+ on the various adsorbents. ΔHo for Pb/Ca exchange was endothermic in nature for K–O–Ca adsorbent and K–TPP–Ca adsorbents. However, it was exothermic for K–Ca adsorbent. ΔGo for Pb/Ca exchange on modified adsorbents was nonspontaneous but was spontaneous for K–Ca adsorbent. With increasing temperature, ΔGo for the ion exchange reaction became more spontaneous for all adsorbents. Pb/Ca ion exchange on phosphate-modified kaolinite clay adsorbents is endothermic in nature and nonspontaneous. However, with increase in temperature, spontaneity of the ion exchange reaction increased. This study suggests that liming of kaolinitic soils will decrease strongly the adsorption capacity of the soil for Pb2+, especially when they have initially adsorbed phosphates.
- ItemCompetitive Modeling for the Biosorptive Removal of Copper and Lead Ions from Aqueous Solution by Mansonia Wood Sawdust.(Elsevier, 2010) Unuabonah, EmmanuelMansonia wood sawdust is applied as a biosorbent for the removal of copper and lead ions from single and binary aqueous solution. The effect of solution pH, electrolyte, metal ion competition and temperature were examined to obtain insight of its application for industrial waste water treatment. The Langmuir isotherm provided a better fit to experimental data for lead ion sorption with a higher monolayer capacity, while copper ion sorption was best described by the Freundlich and BET isotherms. The combined effect of adsorbing one metal ion in the presence of the other metal ion reduced the adsorption capacity of either metal ion. In a binary solution, removal of lead ions in the presence of copper ions followed the Langmuir isotherm model while the removal of copper ions in presence of lead ions followed both the Langmuir and BET isotherm models.