24 research outputs found

    The Effect of Geometrical Isomerism of 3,5-Dicaffeoylquinic Acid on Its Binding Affinity to HIV-Integrase Enzyme: A Molecular Docking Study

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    A potent plant-derived HIV-1 inhibitor, 3,5-dicaffeoylquinic acid (diCQA), has been shown to undergo isomerisation upon UV exposure where the naturally occurring 3trans,5trans-diCQA isomer gives rise to the 3cis,5trans-diCQA, 3trans,5cis-diCQA, and 3cis,5cis-diCQA isomers. In this study, inhibition of HIV-1 INT by UV-induced isomers was investigated using molecular docking methods. Here, density functional theory (DFT) models were used for geometry optimization of the 3,5-diCQA isomers. The YASARA and Autodock VINA software packages were then used to determine the binding interactions between the HIV-1 INT catalytic domain and the 3,5-diCQA isomers and the Discovery Studio suite was used to visualise the interactions between the isomers and the protein. The geometrical isomers of 3,5-diCQA were all found to bind to the catalytic core domain of the INT enzyme. Moreover, the cis geometrical isomers were found to interact with the metal cofactor of HIV-1INT, a phenomenon which has been linked to antiviral potency. Furthermore, the 3trans,5cis-diCQA isomer was also found to interact with both LYS156 and LYS159 which are important residues for viral DNA integration. The differences in binding modes of these naturally coexisting isomers may allow wider synergistic activity which may be beneficial in comparison to the activities of each individual isomer

    Can Taxpayers Stand Discrimination?: Lack of Standing and the Religious Freedom Restoration Act Permits the Executive Branch to Fund Discrimination Within Religious Organizations

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    The Density Functional Theory (DFT) and ab initio (HF and MP2) calculations were performed on the quinoline molecule (QL) and its derivatives, namely quinaldine (QLD) and quinaldic acid (QLDA) to investigate their possible role as corrosion inhibitors for mild steel in acidic medium. Calculations were done for non-protonated and protonated forms in vacuo and in water. Some quantum chemical parameters were calculated and discussed in order to provide insight into the reactivity and selectivity of the molecules. The performance of the different calculation methods were also compared with available experimental data. The results show that DFT/B3LYP basis set is adequate in describing the geometry and quantum chemical parameters of the studied systems. Both experimental and theoretical results established that QLDA has the highest inhibition efficiency. A comparison in the trends of the quantum chemical parameters in water solution and in vacuo shows minimal influence of the solvent effects

    Antioxidant Activity of Rooperol Investigated through Cu (I and II) Chelation Ability and the Hydrogen Transfer Mechanism: A DFT Study

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    Rooperol is a norlignan derivative with numerous biological activities including immunomodulatory, antitumor, anticonvulsant, antibacterial, and antioxidant activities. Its antioxidant activity has been studied by means of experimental techniques, which have shown that it has the ability to scavenge radical species, inhibit lipid peroxidation, and reduce transition metal ions. However, its ability to scavenge radical species and chelate transition metal ions has not been previously studied by means of quantum chemical methods. In this study, density functional theory (DFT) is utilized to investigate the conformational preferences of rooperol, the ability of rooperol to scavenge radical species, and the rooperol路路路Cu interaction mechanism, which might assist in understanding the antioxidant and prooxidant activities of rooperol. The study was performed <i>in vacuo</i> and in selected solvents. The results suggest that lowest-energy conformers of neutral rooperol are stabilized by two intramolecular hydrogen bonds, while the radical species of rooperol are stabilized by both intramolecular hydrogen bonds and spin delocalization of the unpaired electron. The results in different solvents show that the stability of the conformers of rooperol increases with the increase in the solvent polarity, while the stability of radical species decreases with increase in solvent polarity. The stability of the rooperol路路路Cu complexes depends on the site on which the Cu ion binds, while the binding strength depends on both the nature of the cation and the nature of the binding site. The inclusion of solvent effects using the polarizable continuum model shows that the rooperol路路路Cu interaction energies are highly overestimated <i>in vacuo</i>. Finally, the results suggest that the antioxidant activity shown by rooperol corresponds to its interaction with closed-shell transition metal ions, while its prooxidant activity is a result of its interaction with open-shell transition metal ions

    Experimental and theoretical studies on the corrosion inhibition of mild steel by some sulphonamides in aqueous HCl

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    Corrosion inhibition studies of mild steel in aqueous HCl by some sulphonamides namely sulphamethazine (SMT), sulphachloropyridazine (SCP), sulphabenzamide (SBZ) and sulphaquinoxaline (SQX) has been investigated using experimental techniques (such as weight loss, potentiodynamic polarization (PDP), Electrochemical Impedance Spectroscopy (EIS), Fourier transform infrared spectroscopy (FTIR) and Scanning Electron Microscopy (SEM)) and theoretical methods (using the Density Functional Theory (DFT)). All the compounds effectively inhibited the corrosion process by becoming adsorbed on the metal surface following the Langmuir adsorption isotherm model. The electrochemical results showed that these inhibitors are mixed-type. The theoretical studies were undertaken to provide mechanistic insight into the roles of the different substituents on the corrosion inhibition and adsorption behaviour of the studied compounds. The calculated quantum chemical parameters include the highest occupied molecular orbital (HOMO), the energy of the HOMO, dipole moment and partial atomic charges, etc. The calculated molecular properties were compared across the structures of the four compounds in order to identify trends related to their reactivity and their corrosion inhibition ability. The results also show that the ability of the sulphonamides to inhibit metal corrosion is strongly dependent on the electron donating ability of the substituent group and that the preferred site for interaction with the metal surface, in all the sulphonamides, is the SO2 group

    Adsorption and Corrosion Inhibition Studies of Some Selected Dyes as Corrosion Inhibitors for Mild Steel in Acidic Medium: Gravimetric, Electrochemical, Quantum Chemical Studies and Synergistic Effect with Iodide Ions

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    The corrosion inhibition properties of some organic dyes, namely Sunset Yellow (SS), Amaranth (AM), Allura Red (AR), Tartrazine (TZ) and Fast Green (FG), for mild steel corrosion in 0.5 M HCl solution, were investigated using gravimetric, potentiodynamic polarization techniques and quantum chemical calculations. The results showed that the studied dyes are good corrosion inhibitors with enhanced inhibition efficiencies. The inhibition efficiency of all the studied dyes increases with increase in concentration, and decreases with increase in temperature. The results showed that the inhibition efficiency of the dyes increases in the presence of KI due to synergistic interactions of the dye molecules with iodide (I鈭) ions. Potentiodynamic polarization results revealed that the studied dyes are mixed-type inhibitors both in the absence and presence of KI. The adsorption of the studied dyes on mild steel surface, with and without KI, obeys the Langmuir adsorption isotherm and involves physical adsorption mechanism. Quantum chemical calculations revealed that the most likely sites in the dye molecules for interactions with mild steel are the S, O, and N heteroatoms

    Quantum Chemical Investigations on Quinoline Derivatives as Effective Corrosion Inhibitors for Mild Steel in Acidic Medium

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    WOS: 000305267400067The Density Functional Theory (DFT) and ab initio (HF and MP2) calculations were performed on the quinoline molecule (QL) and its derivatives, namely quinaldine (QLD) and quinaldic acid (QLDA) to investigate their possible role as corrosion inhibitors for mild steel in acidic medium. Calculations were done for non-protonated and protonated forms in vacuo and in water. Some quantum chemical parameters were calculated and discussed in order to provide insight into the reactivity and selectivity of the molecules. The performance of the different calculation methods were also compared with available experimental data. The results show that DFT/B3LYP basis set is adequate in describing the geometry and quantum chemical parameters of the studied systems. Both experimental and theoretical results established that QLDA has the highest inhibition efficiency. A comparison in the trends of the quantum chemical parameters in water solution and in vacuo shows minimal influence of the solvent effects.North-West University; National Research Foundation (NRF) of South AfricaM. M. Kabanda, A. K. Singh and S. K. Shukla are grateful to the North-West University for granting them Postdoctoral Fellowships enabling them to participate in this work. E. E. Ebenso thanks the National Research Foundation (NRF) of South Africa for funding
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