Energy Of The Lowest Unoccupied Molecular Orbital Research Articles

QSAR modeling, molecular docking and molecular dynamic simulation of phosphorus-substituted quinoline derivatives as topoisomerase I inhibitors

As they facilitate the cleavage of single and double stranded DNA to relax supercoils, unwind catenanes, and condense chromosomes in eukaryotic cells, Topoisomerase plays crucial roles in cellular reproduction and DNA organization. Because the unrepaired single and double stranded DNA breaks these complexes generate might result in apoptosis and cell death, they are cytotoxic agents.In this study, 28 compounds derived from phosphorus-substituted quinoline are subjected to a quantitative structure–activity relationship (QSAR) using partial least squares, principal component regression, and multiple linear regression. The Gaussian 09 software and the Molecular Operating Environment program were used to calculate molecular descriptors. The anti-proliferative activity was correlated with a variety of electronic and structural characteristics of the molecules, such as EHOMO (energy of the highest occupied molecular orbital) and ELUMO (energy of the lowest unoccupied molecular orbital), which provided evidence for the modeling. The B3LYP/6-31G (d, p) level of theory's Density Functional Theory (DFT) approach was used to compute these electronic properties, and Principal Component Analysis (PCA) was used to test for collinearity between the descriptors. In fact, three alternative prediction models were created using various 2D and 3D descriptor counts, and they were each assessed using the statistical metrics of coefficient of determination (R2) and root mean squared error (RMSE). A MLR model had the best predictive performance of all the constructed models, as indicated by R2 and RMSE of 0.865 and 0.316, respectively.Three proteins (6G77, 2NS2, and 5K47) for lung, ovarian, and kidney malignancies showed strong binding affinities via hydrophobic interactions and H-bonds with the pertinent chemicals by crystal structure modeling. Compounds C11, C19 and C26, respectively, showed the highest binding energy for ovarian, kidney and lung cancer. The outcomes of the molecular dynamic MD simulation diagram were produced to support the molecular docking findings from earlier research, which demonstrated thatinhibitors were stable in the active sites of the selectedproteins for 10 ns. This raises the possibility that these chemicals could serve as a valuable model for the development and synthesis of more effective anticancer prospects.

Multidimensional insight into the corrosion mitigation of clonazepam drug molecule on mild steel in chloride environment: Empirical and computer simulation explorations

In recent years, the use of drugs-based compounds to inhibit mild steel corrosion has grown significantly. Clonazepam stands out among other drug based compounds employed as potential corrosion inhibitors. This study investigates the experimental and computational properties of clonazepam drug molecule as mild steel corrosion inhibitor in chloride solution using weight loss, thermometric, electrochemical impedance spectroscopy, potentiodynamics polarization, surface imaging, Density Functional Theory, and molecular dynamic simulations. The findings demonstrate that as clonazepam drug concentration is increased, the inhibition efficiency increases, reaching a maximum of 90.1% for weight loss, 89.2% for thermometric investigations, 91.4% for electrochemical impedance spectroscopy, and 85.1% for (potentiodynamics polarization) techniques at 500 ppm. The clonazepam drug functions as a mixed-type corrosion inhibitor as demonstrated by the potentiodynamic polarization method. The clonazepam drug adsorption followed the Langmuir adsorption isotherm. The mild steel surface has a barrier layers covering it, as shown by the surface characterization studies via SEM and AFM. The highest occupied molecular orbital (EHOMO), the energy of the lowest unoccupied molecular orbital (ELUMO), the energy gap (ΔE), chemical hardness (η), softness (σ), dipole moment (μ) and electronegativity (Ɛ) were all evaluated for neutral and protonated forms respectively. The molecular dynamic simulations evidenced a near flat adsorption orientation on the Fe surface.

Quantum chemical and mathematical statistical calculations of phenyltetrazole derivatives as corrosion inhibitors for mild steel in acidic solution: A theoretical approach

The use of organic compounds to prevent the corrosion of mild steel has become widespread in recent years. Among the countless chemical compounds used as possible inhibitors, phenyltrazole derivatives stand out as inexpensive and effective molecules in various electrolytes. This research examines the computational characteristics of selected phenyltrazole compounds investigated as inhibitors of mild steel deterioration in HCl medium using a quantum chemical approach (Density Functional Theory) and mathematical calculations. The inhibitory effectiveness of three phenyltrazole compounds: 5-(4-chlorophenyl)-1H-tetrazole (CL-PT), 5-(4-methoxyphenyl)-1H-tetrazole (MO-PT), and 5-phenyl-1H-tetrazole (PT) was investigated. The quantum chemical parameters, such as the highest occupied molecular orbital (EHOMO), the energy of the lowest unoccupied molecular orbital (ELUMO), the energy gap (ΔE), the dipole moment (d), chemical hardness (η), softness (σ), electronegativity (χ), back donation (Δback donation), and global electrophilicity (ω) were evaluated. The results of the quantum chemical calculations revealed that the three compounds have a good anti-corrosion capacity. The order of inhibition efficiency was CL-PT > MO-PT > PT. In addition, cross-checking the data with experimental analysis confirms the theoretical calculations. In mathematical calculations, four mathematical models are suggested. First, second, third, and n-order models are tested. The third-order model was the best one with a high correlation coefficient.

Theoretical Simulation of the Corrosion-inhibition Potentials of Triterpenoids on Aluminium Metal Surface

The mechanism of the corrosion-inhibition action of three selected triterpenoid compounds including α-amyrin, β-amyrin and Lupeol on Al(110) surface was studied using computational methods including molecular dynamic simulations and quantum chemical calculations. The relative corrosion-inhibition performance of the studied compounds was investigated. Quantum chemical parameters including fraction of electron transfer (ΔN) from the inhibitor molecule to the Al(110) surface, energy gap (ΔE), energy of the lowest unoccupied molecular orbital (ELUMO), energy of the highest occupied molecular orbital (EHOMO), global electrophilicity index (ω), global softness (σ), electronegativity (χ) and global hardness (η) were all computed. The local reactivity-indicating sites for electrophilic and nucleophilic attack were analyzed using Fukui indices, while molecular dynamic simulation was used to study their adsorption behavior on the surface of Al(110). Based on the interactions, the adsorption energy (Eads) values obtained, –49.533 kcal/mol for α-amyrin, –48.284 kcal/mol for β-amyrin and –37.654 kcal/mol for lupeol, are all negative with correspondingly low magnitudes (less than –100 kcal/mol). This shows weak and unstable adsorption structures and relatively low corrosion inhibition, suggesting a physical adsorption mechanism with the trend: α-amyrin > β-amyrin > lupeol.

A novel procedure for predicting chronic toxicities and ecological risks of perfluorinated compounds in aquatic environment

Perfluorinated compounds (PFCs) can pose adverse effect on aquatic species and community structure. However, little is known about how the characteristics of molecules of PFCs affect their chronic toxic potencies to aquatic species, and the species sensitivity distributions (SSDs) and ecological risk assessments of PFCs are hampered by limited available data of chronic toxicity. In the present study, a novel procedure is proposed to obtain the ecological risk of PFCs using existing exposure concentrations of PFCs and SSDs integrated with the chronic toxicity prediction through robust QSAR models. The results showed that the energy of the lowest unoccupied molecular orbital (ELUMO) exhibited the strongest correlation with the chronic toxicities of 15 PFCs (R2 > 0.844, F > 16.206, p < 0.05). SSDs of 15 PFCs on eight species were first constructed, and the SSD fitting parameters were significantly correlated with ELUMO (R2 > 0.610, F > 19.471, p < 0.05). The QSAR-SSDs support the evaluation of hazardous criteria of PFCs for which data are lacking. Given environmental exposure distributions (EEDs) of the national presence of PFCs in aquatic systems in China, the QSAR-SSDs models allow the development of the ecological risk assessment for PFCs. This way, it was concluded that negligible environmental risk (defined as 5% of the species being potentially exposed to concentrations able to cause effects in < 5% of the case) could be expected from exposure to PFCs in surface waters in China. This method may be helpful for providing an evidence-based approach to guide the risk management for PFCs in aquatic environment.

DFT computational study of pyridazine derivatives as corrosion inhibitors for mild steel in acidic media

The molecular structures of two Pyridazine derivative;5-phenyl-6-ethyl-pyridazine-3-thione (PEPT) and 5-phenyl-6-ethylpridazine-3-one (PEPO) were simulated for corrosion inhibition efficiency using quantum chemical calculations based on density functional theory (DFT) at the B3LYP/6-31G* basis set level in order to compare the relationship between their molecular structure,electronic structure and inhibition potential.The quantum chemical properties for inhibition efficiency such as EHOMO (energy of the highest occupied molecular orbital), ELUMO (energy of the lowest unoccupied molecular orbital), energy gap (ΔE), dipole moment (μ), global hardness (η), global softness (S), electronegativity (χ), electrophilicity (ω), nucleophilicity (ɛ), electrons transferred from inhibitors to metal surface (ΔN), and the energy change during electronic back-donation process (ΔE*) were calculated. The results show that 5-phenyl-6-ethyl-pyridazine-3-thione (PEPT) would have higher inhibition efficiency than 5-phenyl-6-ethylpridazine-3-one (PEPO) due to its relative EHOMO, ELUMO, ΔE, μ, η, S , ꭓ, ω, ΔN, and ∆E*.

Understanding the inhibition performance of novel dibenzimidazole derivatives on Fe (110) surface: DFT and MD simulation insights

In order to delay or solve the issue of metal material corrosion, six benimidazole derivativesmolecules namely, 2,6- bis (benzimidazole-2′-yl) pyridine (A), 2,5- bis (benzimidazole -2′-yl) pyridine (B), 2,4- bis (benzimidazole -2′-yl) pyridine (C), 2,3- bis (benzimidazole -2′-yl) pyridine (D), 3,5- bis (benzimidazole-2′-yl) pyridine (E), 3,4- bis (benzimidazole -2′-yl) pyridine (F), have been designed and used as corrosion inhibitors. The adsorption behavior and inhibition mechanism of six inhibitors on the Fe (110) surface had been investigated by the molecular dynamics (MD) simulation and quantum chemical calculation. MD simulations revealed parallel orientation of the above six molecules on the iron surface. In quantum chemical calculations, the energy of the highest occupied molecular orbital (EHOMO), energy of the lowest unoccupied molecular orbital (ELUMO), energy gap (ΔE = ELUMO-EHOMO), electronegativity (χ), chemical hardness (σ), and softness (η) were applied for their possible interaction modes with the surfaces. It was found that F molecule among the six novel corrosion inhibitors has strong adsorption capacity, good environmental stability, and potential applications in corrosion protection of iron surface.

1H-Pyrrole, Furan, and Thiophene Molecule Corrosion Inhibitor Behaviors

The corrosion inhibitor behaviors of the molecules 1H-Pyrrole, Furan, and Thiophene were examined using the computational quantum method. The density functional theory (DFT) was applied to the 6-31G (d, p) basis set, parameters such as the energy of the highest occupied molecular orbital (EHOMO), the energy of the lowest unoccupied molecular orbital (ELUMO), the energy difference (ΔE) and the dipole moment (μ) were calculated. These parameters are correlated with the corrosion effects of organic compounds that are mainly investigated in molecular geometry and electronics. Besides, the chemical hardness (ɳ), softness (σ), electronegativity (χ) have been determined. The transmitted electrons fraction (ΔN), have been determined between cupper surface and the 1H-Pyrrol, Furan and the Thiophene molecule. The parameters that have a direct relation with inhibition efficiency are described.&#x0D; According to the obtained results, it can be said that 1H-Pyrrole inhibitor provides a good inhibition activity which can be used as a good anti-corrosion agent. There is an inverse relationship between the transmitted electrons fraction (ΔN) and electronegativity (χ) of inhibitor. The behavior of the corrosion inhibitor can therefore be predicted without an experimental analysis.

Structural Analysis of Epinephrine by Combination of Density Functional Theory and Hartree-Fock Methods

In this study, we built a model to predict the structure and chemical properties of epinephrine using Density Functional Theory (DFT) and Hartree-Fock (HF) methods, as the methods currently playing a significant role in in computational quantum theories. In the model, six basis sets of DFT and HF methods were used to calculate bandgap energies, which the basis set 6-311++G found to be optimal set, as the difference between the methods were minimum. The basis set 6-311++G was further used to characterize the most stable molecular geometry of epinephrine, as well as the molecular characteristics. Then, the basis set B3LYP/6-31G(d,p) applied on epinephrine to investigate the energy of the highest occupied molecular orbital (EHOMO), the energy of the lowest unoccupied molecular orbital (ELUMO), energy gap (ΔE = ELUMO - EHOMO) and the dipole moment (μ). The fraction of transferred electrons (ΔN) was also calculated, which determined the interaction between the iron surface and epinephrine compound. Corrosion inhibitor behavior can therefore be predicted from the calculated data without an experimental study. The findings of the calculations show good relation between organic-based corrosion inhibitors and quantum chemical parameters process. The parametrization and stimulation optimized in this study can be used as a model to predict the chemical structure and activity of any compound with known chemical formula.

Acute toxicity of polychlorinated diphenyl ethers (PCDEs) in three model aquatic organisms (Scenedesmus obliquus, Daphnia magna, and Danio rerio) of different trophic levels

The frequent detection of polychlorinated diphenyl ethers (PCDEs) in aquatic systems has aroused widespread concerns, however, their potential hazard to aquatic ecosystems has been poorly understood. Here the acute toxicity of 12 PCDE congeners was evaluated in three model aquatic organisms representing different trophic levels following OECD test guidelines, including green algae (Scenedesmus obliquus), water flea (Daphnia magna), and zebrafish (Danio rerio). Dose-dependent increases in growth inhibition and mortality were observed for all tested PCDE congeners. Most of the PCDE congeners, in particular 3,3′,4,4′-tetra-CDE, were highly toxic to the three aquatic organisms with EC50 or LC50 values below 1 mg L-1. Their toxicities were generally comparable with those of certain polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). Moreover, D. magna was the most sensitive species among the three aquatic organisms. In addition, the EC50 or LC50 values had an extremely significant correlation with the n-octanol-water partition coefficient (logKow) of the PCDE congeners. The established quantitative structure-property relationship (QSPR) models indicated that the molecular polarizability (α) could significantly influence the acute toxicity of PCDEs on Daphnia magna and Danio rerio, and the energy of the lowest unoccupied molecular orbital (ELUMO) is the key factor of the acute toxicity of PCDEs in Scenedesmus obliquus. In addition, even at environmental levels, 3,3′,4,4′-tetra-CDE could induced seveve oxidative damages in the three aquactic species. These findings would contribute to the understanding of adverse effects of PCDEs in aquatic organisms.

Synthesis, Characterization, and theoretical inhibitor study for (1E,1'E)-2,2'-thiobis(1-(3-mesityl-3-methylcyclobutyl)ethan-1-one) dioxime

In this study synthesized and characterization of (1E,1'E)-2,2'-thiobis(1-(3-mesityl-3-methylcyclobutyl)ethan-1-one) dioxime for both experimental and computational was reported. The solid-state FT-IR spectrum was observed in the range of 4000–400 cm-1 and CDCl3 solvents were used for 1H and 13C NMR analysis. The molecular geometry was calculated using the Density Functional Theory (DFT/B3LYP) method in the ground state with the 6-31G(d, p) basis sets. Vibrational assignments and chemical shifts have been measured theoretically and compared to experimental data. B3LYP/6-31G(d,p) applied on our title compound to found different parameters such as the energy of the highest occupied molecular orbital (EHOMO), the energy of the lowest unoccupied molecular orbital (ELUMO), energy gap ( ΔE = ELUMO - EHOMO) and the dipole moment (μ) related to the corrosion efficacy of organic compounds whose molecular geometry and electronic properties are especially studied were calculated. Properties such as hardness (ɳ), softness (σ), electronegativity (χ) values were computed using these measurement results to inhibitor activity. The fraction of transferred electrons (ΔN) was also calculated, which determined the interaction between the iron surface and the organic compounds. Corrosion inhibitor behavior can therefore be predicted without an experimental study. The findings of the calculations show good relation between organic-based corrosion inhibitors and quantum chemical parameters process.

Study on quantitative structure-biodegradability relationships of amine collectors by GFA-ANN method

In this study, the biodegradability of 17 amine collectors, categorized by fatty amine, quaternary ammonium compounds and oxygen-containing amine collectors, are tested with the Closed Bottle Test for 90 days, and the results indicate most amine collectors are not readily biodegradable. The oxygen-containing amine collectors have the best biodegradability due to the introduced oxygen-containing functional groups, subsequently fatty amine collectors with branched chains, while the tested quaternary ammonium compounds all have poor biodegradation ability. Besides, we search for and calculate 35 molecular descriptors to develop the quantitative structure biodegradability relationship (QSBR) of amine collectors. With the Genetic Function Approximation (GFA) algorithm, two sets of important molecular descriptors related to biodegradability (q) of amine collectors are selected from 35 molecular descriptors. Based on internal and external validations, the robust and reliable non-linear QSBR model with the squared correlation coefficient above 0.99 is determined via Artificial Neural Network (ANN) method, where the descriptors are respectively CL, N, ELUMO, δv2, indicating the biodegradable ability of amine collectors is correlated with the alkyl chain lengths (CL), the number of nitrogen atom-containing compounds (N), energy of the lowest unoccupied molecular orbital (ELUMO) and valence second-order connectivity index (δv2).

Quantitative structure activity relationships (QSARs) and machine learning models for abiotic reduction of organic compounds by an aqueous Fe(II) complex

Due to the increasing diversity of organic contaminants discharged into anoxic water environments, reactivity prediction is necessary for chemical persistence evaluation for water treatment and risk assessment purposes. Almost all quantitative structure activity relationships (QSARs) that describe rates of contaminant transformation apply only to narrowly-defined, relatively homogenous families of reactants (e.g., dechlorination of alkyl halides). In this work, we develop predictive models for abiotic reduction of 60 organic compounds with diverse reducible functional groups, including nitroaromatic compounds (NACs), aliphatic nitro-compounds (ANCs), aromatic N-oxides (ANOs), isoxazoles (ISXs), polyhalogenated alkanes (PHAs), sulfoxides and sulfones (SOs), and others. Rate constants for their reduction were measured using a model reductant system, Fe(II)-tiron. Qualitatively, the rates followed the order NACs > ANOs ≈ ISXs ≈ PHAs > ANCs > SOs. To develop QSARs, both conventional chemical descriptor-based and machine learning (ML)-based approaches were investigated. Conventional univariate QSARs based on a molecular descriptor ELUMO (energy of the lowest-unoccupied molecular orbital) gave good correlations within classes. Multivariate QSARs combining ELUMO with Abraham descriptors for physico-chemical properties gave slightly improved correlations within classes for NCs and NACs, but little improvement in correlation within other classes or among classes. The ML model obtained covers reduction rates for all classes of compounds and all of the conditions studied with the prediction accuracy similar to those of the conventional QSARs for individual classes (r2 = 0.41–0.98 for univariate QSARs, 0.71–0.94 for multivariate QSARs, and 0.83 for the ML model). Both approaches required a scheme for a priori classification of the compounds for model training. This work offers two alternative modeling approaches to comprehensive abiotic reactivity prediction for persistence evaluation of organic compounds in anoxic water environments.

Experimental and Theoretical Investigations on Copper Corrosion Inhibition by Cefixime Drug in 1M HNO3 Solution

Cefixime, a third-generation semi-synthetic cephalosporin antibiotic was used as a copper corrosion inhibitor in 1M HNO3 solution. The study was conducted through the weight loss technique at 298 - 318 K and theoretical studies based on quantum chemistry. The studied drug inhibited the corrosion of copper in 1M HNO3 over the cefixime concentration range (0.02 - 2 mM). The inhibition efficiency increased with an increase in the inhibitor concentration to reach 91.07% at 2 mM, but decreased with an increase in temperature. The thermodynamic functions related to the adsorption of cefixime on the copper surface and that of the metal dissolution were computed and analyzed. The results point out spontaneous adsorption, mainly through a physisorption mechanism following Langmuir adsorption isotherm model and an endothermic dissolution process. Quantum chemical calculations were also performed at B3LYP level with 6-31G (d, p) basis set and lead to molecular descriptors such as EHOMO (energy of the highest occupied molecular orbital), ELUMO (energy of the lowest unoccupied molecular orbital), ΔE (energy gap) and μ (dipole moment). The global reactivity descriptors such as χ (electronegativity), χ (global hardness), S (global softness), and ω (electrophilicity index) were derived using Koopman’s theorem and analyzed. The local reactivity parameters, including Fukui functions and dual descriptors were determined and discussed. Experimental and theoretical results were found to be in good agreement.

ANTI-CORROSION PERFORMANCE OF 2-ISONICOTINOYL-N-PHENYLHYDRAZINECARBOTHIOAMIDE FOR MILD STEEL HYDROCHLORIC ACID SOLUTION: INSIGHTS FROM EXPERIMENTAL MEASUREMENTS AND QUANTUM CHEMICAL CALCULATIONS

The corrosion inhibition performance of novel synthesized thiosemicarbazide derivative namely, 2-isonicotinoyl-N-phenylhydrazinecarbothioamide (IPC) on the mild steel coupon surface in 1[Formula: see text]M hydrochloric acid solution is investigated by weight loss measurements. The adsorption parameters of the IPC on the mild steel coupon surface have been evaluated and the surface morphology of the tested mild steel is studied by scanning electron microscope (SEM) technique. The results of this study demonstrate a significant inhibitor (IPC) for mild steel and showed the highest inhibitive efficiency of 96.3% at 5[Formula: see text]mM as optimum studied inhibitor concentration. The adsorption of IPC molecules on a mild steel coupon surface is obeyed completely by the model of Langmuir adsorption isotherms. SEM has been applied to analyse the layer of IPC molecules which formed on a mild steel coupon surface as a protective layer. The inhibition efficiency (IE) of IPC from weight loss techniques and SEM analysis was harmonic with each other. The Density Functional Theory (DFT) computations have been applied to evaluate the adsorption sites of the IPC molecules and the quantum chemical calculations correlation of IPC molecules with methodological results are discussed. The energy of the highest occupied molecular orbital (EHOMO) shows a significant tendency of the IPC molecules to donate pairs of electrons to the iron atoms on the surface of mild steel. The energy of the lowest unoccupied molecular orbital (ELUMO) for IPS molecules reveals a high tendency to accept electrons from iron atoms on the surface of mild steel.

A computational quantum chemical and polarizability calculations of liquid crystal 4-cyano-4-pentylbiphenyl with water molecule (H2O)

In this paper, we investigate the quantum chemical parameters such as energy of the highest occupied molecular orbital (EHOMO), energy of the lowest unoccupied molecular orbital (ELUMO), HOMO-LUMO energy gap (△Egap), ionization potential (I), electron affinity (A), chemical potential (μ), electronegativity (χ), hardness (η), softness (S), and electrophilicity index (ω) of liquid crystal (LC) 4-cyano-4-pentylbiphenyl with water molecule (H2O). Above quantum chemical parameters have been calculated at Becke's three-parameter hybrid exchange functional and the Lee–Yang–Parr correlation functional (B3LYP) with 6-31G(d) and 6-31G++(d,p) basis sets in the framework of density-functional theory (DFT). For comparative purposes, we also optimize 4-cyano-4-pentylbiphenyl with water molecule at Perdew-Burke-Ernzerhof (PBEPBE) with 6-31++G(d,p) level. Mulliken charge analysis infer that (-0.03e) amount of charge is being associated with the H2O at B3LYP/6-31G(d) level. This fact indicates a considerable amount of electron population is transferred from pristine 4-cyano-4- pentylbiphenyl to H2O molecule. Polarizability tensor components such as αxx, αyy, αzz, average polarizability (αav), and polarizability anisotropy (Δα) have been calculated. The most intense IR spectral characteristics of 4-cyano-4-pentylbiphenyl with water molecule are accommodated in between 3000 cm−1 to 3920 cm−1at all presented levels.

Coenzyme Coupling Boosts Charge Transport through Single Bioactive Enzyme Junctions.

SummaryOxidation of formate to CO2 is catalyzed via the donation of electrons from formate dehydrogenase (FDH) to nicotinamide adenine dinucleotide (NAD+), and thus the charge transport characteristics of FDH become essential but remain unexplored. Here, we investigated the charge transport through single-enzyme junctions of FDH using the scanning tunneling microscope break junction technique (STM-BJ). We found that the coupling of NAD+ with FDH boosts the charge transport by ∼2,100%, and the single-enzyme conductance highly correlates with the enzyme activity. The combined flicker noise analysis demonstrated the switching of the coenzyme-mediated charge transport pathway and supported by the significantly reduced HOMO-LUMO gap from calculations. Site-specific mutagenesis analysis demonstrated that FDH-NAD+ stably combined own higher bioactivity and boosts charge transport, and the coupling has been optimized via the natural selection. Our work provides evidence of hydrogen bond coupling in bioactivity but also bridges the charge transport through single-enzyme junctions and enzyme activities.

Quantum-Chemical Prediction of the Redox Properties of Humic Acids

A comparative analysis of the reactivity indices of the model structure of humic acids (HAs) and a number of antioxidants was carried out based on the results of quantum-chemical calculations performed using the density functional theory (DFT) b3lyp/6-31g(d,p) method. With the use of 15 compounds as an example, it was found that the electronegativity index χ linearly correlates with the energy of the lowest unoccupied molecular orbital (ELUMO), R2 = 0.977. HAs (ELUMO = –2.52) are located close to molecular oxygen (ELUMO = –3.07), and this fact indicates a high electronegativity of these natural compounds. It was proposed to evaluate the antioxidant ability of the organic matter of HAs by the adsorption energy of molecular oxygen. By determining the local minima of O2 sensing energy in different sections of HAs using the pm6 quantum chemical method, it was established that oxygen is adsorbed by a hydroxyl group with the energy ∆Eads = –70 kcal/mol. This allows the highly reactive organic part of HAs to inhibit molecular oxygen in oxidation processes.

A Computational Study of Quinoline Derivatives as Corrosion Inhibitors for Mild Steel in Acidic Medium

The corrosion inhibition efficiency of three quinoline derivatives namely; ethyl 2-(((8-hydroxyquinolin5-yl)methyl)amino)acetate (QN1), 5-((benzylamino)methyl)quinolin-8-ol (QN2) and 5-(azidomethyl)quinolin-8-ol (QN3) on the mild steel in 1 M HCl was studied using density functional theory (DFT) calculations and quantitative structural activity relationship (QSAR) approach. The experimental inhibition efficiency were discussed in relation with molecular descriptors such as such as EHOMO (energy of the highest occupied molecular orbital), ELUMO (energy of the lowest unoccupied molecular orbital), band gap (BG), dipole moment (DM), chemical hardness (η), softness (σ), electronegativity (χ), electrophilicity (ω), global nucleophilicity (ɛ), electrons transferred from inhibitors to metal surface (ΔN), initial molecule–metal interaction energy (∆ψ), the energy change during electronic back-donation process (ΔEb-d), Molecular weight (MW), and Volume (V). The result showed that EHOMO, σ , ω, ΔN, ∆Eb-d and ∆ψ increases as the percentage inhibition efficiency (%IE) increases. ELUMO, BG, η , DM, and e decreases with increasing% IE, while χ , MW and V did not show any correlation with %IE. The QSAR model developed reproduced the observed corrosion inhibition efficiencies of these compounds well with a cross validation (CV. R2 ) value of 0.9994 and adjusted squared correlation coefficient (R2 adj) value of 0.9988. The results obtained in the study are in good agreement with experimental inhibition efficiency results reported earlier in literature.Keywords: Corrosion Inhibition, Quantum Chemical Calculation, Quinoline Derivatives, QSAR

Understanding Inhibition of Steel Corrosion by Some Potent Triazole Derivatives of Pyrimidine through Density Functional Theory and Molecular Dynamics Simulation Studies

Density Functional Theory (DFT) calculation at B3LYP level of theory and 6-31G* basis set was applied on some triazole derivatives of pyrimidine which led to the optimization of their structures, generation of electronic and other important Quantum chemical descriptors such as the energy of the highest occupied molecular orbital (EHOMO), the energy of the lowest unoccupied molecular orbital (ELUMO), energy band gap (ΔE), Dipole Moment (μ), chemical hardness (η), chemical softness (σ), global electronegativity() and number of transferred electrons () using SPARTAN’14 Software. The obtained results shows a good correlation between the chemical structures of the inhibitors and their experimental inhibition efficiencies (%IEs). The ranking of these efficiencies (%IEs) nicely matched with the order of a good number of the generated descriptors but with a varying degree of correlation as majority of the descriptors indicates that I-4 is the best inhibitor among the data set. Furthermore, molecular dynamic (MD) simulations were carried out to search the best adsorption configuration of the inhibitor on the steel (1 1 0) surface using Material Studio 8.0. The obtained results of MD simulations suggest that the interaction was as a results of the chemical adsorption on the steel surface, since the binding energy &amp;gt; 100 Kcalmol-1 for all the inhibitors and the best adsorption energy was found to be -488.07 Kcalmol-1 (I-4). This observation are in good agreement with the DFT results and the experiment findings. Thus; this study provides a valuable approach and new direction to novel steel corrosion inhibitor discovery.