Physical Chemistry Research
Volume:8 Issue: 3, Summer 2020

Appearing as a computational microscope, MD simulation can ‘zoom in’ to atomic resolution to assess detailed interactions of a membrane protein with its surrounding lipids, which play important roles in the stability and function of such proteins. This study has employed the molecular dynamics (MD) simulations, to determine the effect of added DMPC or DMTAP molecules on the structure of DPPC bilayer, and also to characterize the mutual interactions of TM23-GlyR (The second and third transmembrane domains of glycine receptor), with the pure and mixed lipid bilayers. Structural properties of DPPC bilayer, namely the order of acyl chains and the area per lipid, were affected by cationic DMTAP and zwitterionic DMPC lipids, in completely reverse ways. In the case of the mutual interactions of lipid molecules and TM23-GlyR, the cationic DMTAP lipids showed greater impact on the structural properties of this protein. On the other hand, TM23-GlyR caused clear increase in the lipid chain order, due to the positive hydrophobic mismatch. In total, this study could shed light on the effect of lipid force field, chain length, and the head group charge and size, on the lipid-protein interplay.

Corrosion of metal surfaces amongst other problems is one major disaster militating against proper functioning of the oil and gas and other manufacturing industries. To therefore lessen the risk, organic corrosion inhibitors have been applied to lessen the rate of corrosion and its effects. However, materials with optimal properties, better than content that allow corrosion are used for this empirical research. (E)-4-hydroxy-3-(2,4,6-tribromophenyl)diazenyl)benzaldehyde was synthesized and elucidated via FTIR, UV/Vis and NMR (1H and 13C) spectroscopy. Weight loss and potentiodynamic polarization methods were understudy to determine the rate of corrosion (Cr) and percentage inhibition efficiency (%IE). The mechanism of adsorption agrees with the Langmuir adsorption isotherm. The surface morphology of the mild steel was determined using the SEM in the bi-condition of the presence and absence of inhibitor. Inhibition efficiency (IE) was varied with concentration and temperature. The results revealed that IE increased with high concentration of the inhibitor but reduced while the temperature was increased. The SEM revealed the formation of protective layer of the attachment of the inhibitor to the metal surface. The results from the experiments agreed well with those obtained from DFT methods. AD3 could therefore be used as an anticorrosive agent in the petroleum industry.

Oils of vegetable origin are of great importance in food, soap, and cosmetic industries and they may also be used as lubricants and raw materials for biodiesel production depending on their viscosity and thermal stability. This work provides insight into the fatty acid components, physicochemical properties and thermal stability of some refined vegetable oils. The Saponification values, peroxide values, acid values, iodine values and refractive index of these oils range from 185.38 to 209.26 mg/g KOH, 2.00 to 37.00 meq O2/ kg, 2.50 to 5.50 mg KOH/ g, 31.09 to 89.46 g / 100g and 1.441 to 1.488 respectively The activation energies obtained from Arrhenius-type equation range from 11.32 to 3.85 kJ mol-1, while the enthalpy (∆H҂) and entropy (∆S҂) of activation obtained from Eyring-type equation range from 6.852 to 14.317 kJ mol-1 and -31.85 to -29.06 J mol-1 K-1 respectively. The Gibbs free energy of activation (∆G҂) ranges from 15.51 to 23.81 k J mol-1. The Pw oil brand has the highest thermal stability and resistance to shear stress due to its high activation energy and a low degree of unsaturation. The heat was absorbed during the process, the reaction mechanism was associative and the entire process was non-spontaneous.

In this work, we determined thermophysical properties such as electrical conductivity and refractive index for 1-propyl-3-methylimidazolium bromide, [PrMIm]Br in ternary mixtures of [PrMIm]Br + ethylene carbonate + water at T = (298.2, 308.2 and 318.2) K and 0.1MPa. Conductometric measurements were carried out for [PrMIm]Br ionic liquid in ethylene carbonate + water solvent mixture in various composition 10, 20 and 30 mass% of ethylene carbonate (EC) in the ionic strength ranging from 0.0029 to 0.2500 mol.kg-1. These data were treated by Fuoss-Onsager equation, and the values of limiting molar conductivity ( ) and ion association constant (KA) were obtained. These results used to calculate the Walden product ( ) and the corresponding standard thermodynamic functions of ion association process including Gibbs free energy ( ), enthalpy ( ) and entropy ( ) for the investigated system. In addition, refractive indices were measured for the binary and ternary [PrMIm]Br + water + EC mixtures at T = (298.2, 308.2 and 318.2) K. The refractive index deviations (ΔnD) were calculated and the binary and ternary data of ΔnD were correlated using Redlich-Kister and the Cibulka equations, respectively. Also, the measured refractive indices were compared to the calculated values using some mixing rules.

Heterocyclic compounds based on Imidazole are very studied today because they are promising for pharmaceuticals applications and synthetic chemistry. Thus, the synthesis, characterization, and optical properties of four different Schiff bases ligands based on imidazole named L1-L4 has been reported by many authors. These compounds have been very studied especially their antifungal properties on an important fungal specie pathogenic for humans (Candida albicans). In this study, firstly the DFT quantum chemical calculations were performed on 4 structures based on Imidazole (L1, L2, L3 and L4) to determine their structural and electronic properties and to understand the correlation that exists between structure and their properties. In the second part, the molecular docking was carried out on the most and less active compounds (L1 and L4) with their targeted proteins to explain the origin of these in silico antioxidant properties and to examine the probable binding mode of the studied compounds with the corresponding amino acid residues of protein. The theoretical results were compared with experimental data.

Application of deep eutectic solvents in industrial chemical processes are improved over time in last decades. In this work, vapor pressures of 13 classes of DESs (DES 1-13) based on 5 salts and 7 hydrogen bond donors with various combinations of molar ratio were used between 343-393 K. The vapor pressure of the pure and aqueous solutions of DESs was calculated by different equations of state, which are based on “φ-φ” and "γ-φ" approachs. Additionally, Voutsas and Wagner models as corresponding-state models were modified to predict the vapor pressure of the pure and aqueous solutions of DESs. The total average absolute relative deviations of the Modified-Voutsas and Modified-Wagner models for the vapor pressure calculation of the pure and aqueous solutions of DESs were 7.03, 9.08 % and 5.47, 7.15 %, respectively. Moreover, the validity of vapor pressure calculation using the two modified models was checked with the aid of a linear equation for the average specific heat capacity of different DESs (23 classes of DESs) between 278.15-353.15 K. Results showed that the total average absolute relative deviations of the specific heat capacity of DESs using the Modified-Voutsas and Modified-Wagner models from the experimental data were 4.128 and 4.056 %, respectively.

Solubility data and tie-line points were experimentally determined for the ternary system (water + phosphoric acid + Heptyl acetate) at T = 298.2 K and ambient pressure. The cloud point method was used to measure the immiscibility region. Type-1 LLE behavior was observed for the investigated system and the plait point data were calculated using the Treybal’s method. The compositions of both aqueous and esteric layers were determined by using of acid-base titration, HPLC method and mass balance equation. The Othmer–Tobias and Hand equations were applied to prove the reliability of tie-line data. Obtained tie-line points were then correlated using the UNIQUAC model and the rmsd results showed that the measured points were satisfactorily regressed by the thermodynamic model. To evaluate the ability of the studied solvent for purification of phosphoric acid, distribution coefficients and separation factors were calculated over the biphasic area. Separation factors were greater than one in all investigated feeds of phosphoric acid for the studied system. Heptyl acetate showed the highest separation factors between all the investigated n-alkyl acetate esters.

In the present study, the capability of the pristine and P-doped Al12N12 nanocage to deliver and detect of 5-Fluorouracil (5-FU) anticancer drug are investigated using the density functional theory (DFT) at the cam-B3LYP/6-31G(d, P) level of theory. The adsorption energy, thermodynamic parameters, natural bond orbital (NBO), atom in molecule theory (AIM), quantum parameters, reduced density gradient (RDG) and UV-visible spectrum for all selected models are calculated and results are analyzed. The values of adsorption energy (Eads) and thermodynamic parameters (ΔG and ΔH) for 5-FU@Al12N12 and 5-FU@Al12N11P complexes are negative and obtained results reveal that all adsorption processes are spontaneous and suitable to make a delivery of drug. The ΔΔG(sol) values of the all studied systems in the presence of water and ethanol solvent are positive and this property is favourable to shooting drug in biological system. The AIM, RDG, NBO calculated results indicate that the interaction between 5-FU drug and Al12N12 nanocage is weak covalent or strong electrostatic type. The bandgap energy of the 5-FU/Al12N12 nanocage complex alters slightly from original values, and so the pristine and P doped Al12N12 nanocage is not an excellent candidate for making a sensitive sensor for the 5-FU drug.

Density functional theory (DFT) and time dependent density functional theory (TD-DFT) calculations were employed to investigate the electronic and nonlinear optical properties of some substituted C2Bn −2Hn (n = 14 −17) carboranes. Li, Na, K, F, Cl, Br are used as substituents. The carboranes substituted with alkali metal show considerably large first hyperpolarizability values than those of un-substituted ones. NLO response of the halogen-substituted systems is slightly enhanced. The well-known two-level model theory is investigated through TD-DFT approach to understand the origin of NLO response. This study indicates that alkali-metal substituted carboranes may be appropriate for nonlinear optical (NLO) applications.

In this research, the performance of functionalized boron nitride nanosheet (BNNS) as a nanostructure membrane with single-atom thickness for the separation of arsenite ions from aqueous solution was examined by molecular dynamics simulation method. The simulated system included a functionalized BNNS placed in an ionic solution containing sodium arsenite, while the external pressures were applied to the system. For the high-water permeability and full ions rejection, the pore of BNNS was functionalized by passivizing pore edge atoms with F and H atoms. Then hydrostatic pressures in the range of 5-100 MPa was applied to the system. During the molecular dynamics simulations, water molecules and arsenite ions were monitored, and some analyses such as water flux, the density profile of water and ion, hydrogen bonds, and radial distribution function were obtained. Results showed that functionalized BNNS was able to conduct water molecules with high permeability through its pore, whereas ions were not able to pass through the pore.

Selective oxidation of cyclohexene and styrene was investigated using molecular oxygen under mild conditions. Au/TiO2 and Au/Al2O3 surfaces were impregnated with three different ionic liquids. Supported ionic liquids (ILs) gold nanocatalysts are particularly versatile catalysts for oxidation reaction with exceptionally high efficiency and significant selectivity. Improved activity is attributed to the stabilization of reaction intermediates via different interaction such as hydrogen bonding and polarity/dipolarizability between ILs and intermediates. Surface coating of obtained nanoparticles with ionic liquids is found to increase the interaction energy. The estimated rate constant decreases in the following order: [EAP] > [bmim]PF6 > [emim]EtSO4. EAP/Au/Al2O3 exhibited maximum conversion compare to other IL-impregnated catalysts. Supported ionic liquids gold nanocatalysts are active catalysts for oxidation reaction with high efficiency and selectivity.

This work examines the possibility of removing the crystal violet (a cationic dye), used in the dyeing of cotton, wood, and silk, onto untreated coffee waste. The influence of various experimental parameters on the adsorption of crystal violet has been analysed: pH, adsorbent dose and initial dye concentration. Optimum adsorption of crystal violet took place at pH 6 and at lower temperatures. Further, the adsorbent was characterised by Fourier Transform Infrared Spectroscopy (FTIR). FTIR analysis revealed the presence of several functional groups that are responsible for the adsorption process. Adsorption equilibrium follows Langmuir’s model with maximum retention of 63.3 mg/g. The kinetics of the crystal violet adsorption were studied using the pseudo-first order and pseudo-second order equations. Adsorption of the dye can be described by pseudo-second order kinetics, reaching the equilibrium at 40 min. The value of the activation energy shows that adsorption is physisorption. Weber-Morris model indicates that this adsorption occurs in two steps. Thermodynamic parameters suggest that the adsorption is spontaneous and exothermic.