Physical Chemistry Research
Volume:5 Issue: 2, Spring 2017

Because of participation in many aspects of human life, and due to oxidation-sensitive characteristics of dopamine (DA) and arachidonoyl dopamine (AA-DA), the necessity of biocompatible carrier to keep them against oxidation is of importance. In this work, we explored the putative binding sites of DA and AA-DA to -lactoglobulin (BLG) as potent carrier. Docking results identified the binding sites, involved residues and driving forces to the binding process of these ligands. The dissimilar binding site of AA-DA in comparison with DA has been designated by different values of Gibbs free energy, biding constants and contact residues. Molecular dynamics simulation outcomes confirmed that both compounds stayed in their predicted binding sites during the entire time of simulation with no major secondary and tertiary protein structural changes which pointed that BLG might be considered as a suitable oxidation-protective carrier for these compounds.

In this work, the thermal reaction of aluminum (Al) and nickel oxide (NiO) was investigated by molecular dynamics simulations. Some effective features of reaction such as reaction temperature, the reaction mechanism, and diffusion rate of oxygen into aluminum structure were studied. ReaxFF force field was performed to study the Al/NiO thermite reaction behavior at five different temperatures (500, 900, 1100, 1200, and 1400 K). The results obtained from the molecular dynamics simulation predict that the reaction temperature for aluminum metal and nickel oxide mixture would be 1141 K, which is in a good agreement with that of the experimental value (i.e. 1148.8 K). In addition, the mean square displacement analysis suggests that the movement of aluminum atoms is less than that of oxygen and nickel atoms. The estimated diffusion coefficient of oxygen in the aluminum / nickel oxide thermite mixtures was 4.53 × 10-8 m2 s-1. The results show that the diffusion coefficients significantly increase, by increasing temperature.

Proton transfer (PT) and methyl group transfer (MGT) occurring in small biomimetic systems, Formamide-Formamidic acid (FA-FI), and N-formyl-N-methylformamide-(E)-methyl N-formylformimidate (NMFA-NMFI) are investigated in the gas phase and in single-walled carbon nanotubes by using the density functional theory and the ONIOM approach. It is shown that PT reaction is disfavoured in single-walled CNT (5.5) because it increases the energy barrier, while confinement in CNT (6,6) decreases the energy barrier of MGT. In contrast, the MGT reaction is notably affected by the confinement CNT(6,6) in view of the geometries and energies. The confinement of CNT(6,6) has an influence on the structures and energy barriers, and the activation energies obviously decrease slightly.

In this study, a novel magnetic nanocomposite (Ba-α-Bi2O3-γ-Fe2O3) was successfully synthesized through a combination of ultrasound and co-precipitation method under mild conditions. The structure of the synthesized nano-composite as a visible light photocatalyst was investigated by the XRD, TEM, HRTEM, UV-vis and FT-IR. The HRTEM confirmed that the nano-magnetic composites are rods with diameters of 10–12 nm and lengths of 100–200 nm. The photocatalytic activities of Ba-α-Bi2O3-γ-Fe2O3, α-Bi2O3-γ-Fe2O3, α-Bi2O3, and γ-Fe2O3 were compared by the degradation efficiency of amoxicillin as an antibiotic drug under solar light. Based on the results, amoxicillin in aqueous solution was more efficient photodegraded using Ba-α-Bi2O3-γ-Fe2O3 as nanocomposite under solar light irradiation. The degradation reached to 99% and the mineralization reached to 55% within 2 h under sunlight. In addition, the results of degradation were fitted to the first-order kinetics model and the kinetic constant was 0.017 min-1 with a half-life time of 40 min. Based on the performed experiments, the photogenerated electrons played an important role in the decomposition process. In addition, it was confirmed that the formation of oxidative kinds, such as singlet oxygen and superoxide radical in the presence of oxygen were the major factors in the destruction.

Density, viscosity and refractive index of pure, binary and ternary mixtures of diethanolamine (DEA) and methyl diethanolamine (MDEA) with water have been measured at different temperatures from 288.15 K to 323.15 K at atmospheric pressure. Also, this study presents the effects of mixture composition and temperature upon these thermo- physical properties. To measure the density and refractive index, the amine mass percentages of binary and ternary aqueous solutions were between 5% to 40% and 40% to 80% respectively. For determining the kinematic viscosity, the amine mass percentages for binary aqueous solutions were 5% to 40%. The densities, refractive indexes, and viscosities of 22 binary and ternary mixtures were finally measured.

The examination of available vapor pressure data in the case of the methane, ethane, propane and butane halogenated refrigerants, allowed recommendations of standard equations for this property. In this study, three new models include a general correlation; a substance-dependent correlation and an artificial neural network (ANN) approach have been developed to estimate the saturated vapor pressure of refrigerants. With the presented approaches, vapor pressures have been calculated and compared with source data bank for 5600 data points of 28 refrigerants. The accuracies of new correlations and ANN have been compared with most commonly used correlations and the comparison indicates that all new models provide more accurate results than other literature correlations considered in this work.

The effect of Mentha spicata L. extract on the corrosion behaviour of carbon steel in 1.0 M HCl solution was investigated using polarization, electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN) techniques. The solution containing 250 ppm of the ethanolic solution of extract showed the highest inhibition efficiency (IE). The effect of temperature on the rate of corrosion in the absence and presence of inhibitor was also studied. Adsorption of extract on the carbon steel surface obeyed the Langmuir adsorption isotherm. Polarization measurements indicated that the inhibitor was of mixed type. The IE values from EN measurements showed a reasonable agreement with those obtained from polarization and EIS techniques. The EN method was applied as a complementary quantitative technique to study the corrosion behaviour of the inhibitor.

In this work, the effect of ligand's length on interaction energy of six oximes, A [2-(hydroxyimino)-N-((1-(2-(2-((hydroxyimino)methyl)-1H-imidazol-1-yl)ethyl)-1H-1,2,3-triazol-4-yl)methyl)acetamide], B [2-(hydroxyimino)-N-((1-(3-(2-((hydroxyimino)methyl)-1H-imidazol-1-yl)propyl)-1H-1,2,3-triazol-4-yl)methyl)acetamide], C [2-(hydroxyimino)-N-((1-(4-(2-((hydroxyimino)methyl)-1H-imidazol-1-yl)butyl)-1H-1,2,3-triazol-4-yl)methyl)acetamide], D [2-(hydroxyimino)-N-((1-(5-(2-((hydroxyimino)methyl)-1H-imidazol-1-yl)pentyl)-1H-1,2,3-triazol-4-yl)methyl)acetamide], E [2-(hydroxyimino)-N-((1-(6-(2-((hydroxyimino)methyl)-1H-imidazol-1-yl)hexyl)-1H-1,2,3-triazol-4-yl)methyl)acetamide] and F [2-(hydroxyimino)-N-((1-(7-(2-((hydroxyimino)methyl)-1H-imidazol-1-yl)heptyl)-1H-1,2,3-triazol-4-yl)methyl)acetamide] with tabun inhibited acetylcholinesterase (t-AChE) is investigated by using docking methods. The results show that the size of ligand's length, due to changing the position of interactive groups of oximes in active site of enzyme can regulate oxime-enzyme interaction energy for better reactivation of inhibited cholinesterases by oximes. Indeed, increment of oxime-enzyme interaction energy has paradoxical effects both increasing of oxime affinity to t-AChE, and decreasing of the rate of the oxime access to phosphorus atom within tabun binding to the acetylcholinesterase active site. The obtained results show that to design an oxime as a drug, the length of oxime should be chosen in a size that the interaction of oxime and enzyme is neither too weak to couple, nor too strong to limit oxime mobility in reactivation t-AChE after coupling.

Alkanolamine solutions such as 2-amino-2-methyl-1-propanol (AMP) are widely used in chemical industries for the removal of acid gases such as CO2 and H2S. In this work, the density of CO2, AMP, water, and AMP solutions using the Goharshadi–Morsali–Abbaspour Equation of State “GMA EoS” in the extended 50-degree range of temperatures (313.06-362.65 K) and pressures (0.5-40 MPa) was calculated. The results showed that the GMA EoS can reproduce the density of these fluids within experimental errors throughout the liquid phase. The minimum and maximum absolute average deviations for the prediction of density for all studied fluids are -0.0082 and 5.2288, respectively. The values of statistical parameters between experimental and calculated thermodynamic properties such as isobaric expansion coefficient, isothermal compressibility, internal pressure, and solubility parameter of AMP show the ability of this equation of state in reproducing these properties.

In the present study, the kinetics of biodiesel production through transesterification of Brassica carinata oil with methanol in the presence of Potassium Hydroxide is investigated by kinetic Monte Carlo simulation. The obtained results from simulation agree qualitatively with the existing experimental data. The kinetics data for each step of suggested mechanism are confirmed by simulation. By using the mechanism and kinetics data, the system is simulated at different methanol/oil feed ratios and a comparison between kinetic data is provided. The influences of temperature and percentage of catalyst on the amount of produced biodiesel at different times of reaction are obtained.

A superhydrophobic aluminum surface was fabricated through an enhanced low-cost approach and the effects of several relevant factors on static contact angle and sliding angle were investigated. First, the operating parameters including the etching time as well as the reaction time and temperature were varied. Next, the so-called chemical factors including three different fatty acids and five different solvents were examined. The surface was analyzed by means of SEM, ATR-FTIR, EDX, and WCA measurements. The results show that the immersion time of about 5 min and the reaction temperature of about 60 °C were the optimum conditions for the creation of a superhydrophobic Al surface with excellent self-cleaning properties. Overall, the choice of oleic acid and ethanol were found to be the best as the fatty acid and solvent, respectively. The highest contact angle was 163.7° and the lowest sliding angle was about 1°.

In this study the operations of melting of Au15Ag40 nanoalloy have been studied using the molecular dynamic simulations through the Gupta multiparticle potential and the nonergodicity of simulations is eliminated by the multiple histogram method. The melting characteristics are determined by the analysis of variations in the potential energy. The calculations indicate that the melting of Au15Ag40 nanoalloy is started at 470 K and raised to peak at 505 K and at about 600 K the total of Au15Ag40 melted. We also obtained the Lindemann parameter and other properties at several temperatures during the simulation. The power spectrum values at zero frequency used to show the intensity of diffusive motions at the given temperature.

First principles calculations were carried out for investigation the novel 7-hydroxycoumarinyl gallates derivatives in gas and liquid phases using density functional theory (DFT) method. Computational chemistry simulations were carried out to compare calculated quantum chemical parameters for gallates derivatives. All calculations were performed using DMol3 code which is based on DFT. The Double Numerical basis set with double numerical plus d-function (DND) was used. Calculations were carried out to study the interaction of covalently binding gallates derivatives to the armchair single-walled carbon nanotube (10, 10). The local reactivity was studied through the fukui indices in order to predict both the reactive centers and the practicable sites of nucleophilic and electrophilic attacks. The adsorption energies, the quantum molecular descriptors analysis and the structural changes at the adsorption site are indicative of chemisorption on the armchair single-walled carbon nanotube (10, 10) surface. The HOMO and LUMO are witness to the substantial changes in the electronic properties of the SWCNT systems. Adsorption energies indicate that 7-hydroxycoumarinyl gallates derivatives are physicosorbed on carbon nanotube (10, 10). This property enables the delivery of these derivatives with anti-cancer potential from the nanotube at the targeted sites. These results are extremely relevant in order to diagnosis the potential applications of carbon nanotubes as efficient boats for targeted drug delivery.

Static properties, relatively intensity noise and intensity modulation response in quantum cascade lasers (QCLs) studied theoretically in this paper. The present rate equations model consists of three equations for the electrons density in the conduction band and one equation for photons density in cavity length. Two equations were derived to calculate the noise and modulation response. Calculations in this paper focused on the effect of optical phonon emission rateτij, a number of stages and the gain coefficient on the noise spectrum and modulation response in this types of semiconductor lasers. The results indicate the strong effect of optical phonon emission rate, the gain coefficient and a number of stages on the dynamics properties of QCLs. The static properties such as the population inversion, the threshold injection current and the steady state photons density deviate from the ideal values with increasing in τ21 .The effect of optical phonon emission rateτ21 has similar effect to the effect of photon lifetime on the noise spectrum in comparison with other times.

In this work, the dry reforming of methane was studied using a corona and glow discharge plasma microreactors. A chemical kinetic model was developed to understand the reaction better. The modelization allowed prediction of the reactants conversion according to the energy transfer to the gas (P×τ). The β value is trait of the energy cost, whatever this value was leeser indicated better efficiency. The β value of CH4 equal to 10.42 and 9.91 J and for CO2 equal to 12.24 and 15.42 J for corona and glow discharge plasma respectively, because the dissociation energy of CO2 higher than CH4. The kinetic model demonstrated that there is an exponential function between the conversion of CH4 and CO2 and plasma energy. Also, corona discharge plasma reactor with smaller CH4/CO2 ratio has higher energy efficiency for CO2 and lower for CH4.