Physical Chemistry Research
Volume:9 Issue: 3, Summer 2021

In this study, the liquid-liquid equilibrium (LLE) in the aqueous two-phase system (ATPS) formed by polyethylene glycol (PEG1500 and PEG6000) and magnesium sulfate is investigated. The experimental measurements were performed at temperature of 298.15 K and pH values of 3.60, 5.00, 6.67. Densities and refractive indices of the mixtures were first measured to obtain the compositions from the plotted tie lines. The effects of pH and molecular mass of polymers on the binodal curve, tie lines length (TLL) and slope of tie line (STL) have been examined. It was found the pH values and molecular weight rise the heterogeneous region for each system. The binodal curve was fitted to the Merchuk and the Pirdashti equations. The Othmer-Tobias as well as the Bancroft equations were subsequently selected to correlate the compositions of the tie lines at equilibrium where the fitted parameters are derived. In addition, the Guan’s equation was utilized to correlate the experimental binodal curves. Finally, the effectively excluded volume (EEV) was determined and the values were found to increase with pH.

The effect of Cox addition in the range of 0.1 to 1 mole into Cu supported on activated carbon (AC) catalysts fabricated by deposition-precipitation method was assessed. CuCox/AC prepared via the same method under different calcination temperature was done to evaluate the effect on the properties and activity of the catalysts. The bimetallic Cu-Co catalysts are structurally characterized by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). It was found that Co was clearly incorporated in Cu/AC lattice and improved the crystalline structure with optimum Co loading. CuCox/AC nanoparticles formed with uniform shapes and size under the present synthesis conditions. The catalytic performances of the as-prepared catalysts were evaluated towards the aerobic oxidation of benzyl alcohol using hydrogen peroxide as oxidant. Cu/AC, Co/AC and CuCox/AC showed ability to oxidize benzyl alcohol to benzaldehyde. CuCo0.2/AC calcined at 450°C showed highest catalytic activity exhibiting 86% conversion of benzyl alcohol due to the high crystallinity as compared to the monometallic counterpart. It was found that the crystallinity of the catalysts could be tuned by varying the amount of Co. The synergistic effects of Cu-Co in optimum mole ratio and calcination temperature influenced the availability of active sites participating in the catalytic activity.

Detecting glyphosate is of great importance as it has been classified as a probable carcinogen. In literature, many nanotubes have been used to detect Glyp among them CNT. However, we did not found any study that used BNNT to detect it. So, in this work, we focus on performing a comparative study of the Glyp adsorption on CNT (5.5) and BNNT (5.5) using B3LYP, M06-2X, and B97X-D/6-31G(d) by first-principles calculations in the framework of Density Functional Theory. From our results, we conclude that the adsorption energies of BNNT (5.5)/Glyp are slightly higher than those calculated by CNT (5.5)/ Glyp and are in very close agreement with the NCI analyses. The thermodynamics parameters also showed that the two nanotubes could detect glyphosate with a physisorption process that was exothermic and thermodynamically favourable. Besides that, TDOS and QTAIM analyses revealed the non-covalent interaction between glyphosate and the two nanotubes.

In this investigation, we have optimized uridine and its acylated derivatives employing density functional theory (DFT). All designed derivatives were optimized at the B3LYP/3-21G level of theory. Charge distribution, polarizability, and thermodynamic properties such as free energy, heat capacity, and entropy of modified derivatives were explored in the subsequent analysis to evaluate how certain groups impact the drug properties. To understand the mode of binding and molecular interaction, molecular docking calculation was carried out to point out the potential inhibitors of the SARS-CoV-2 main protease (PDB: 6Y84 and 6LU7) by screening a total of fourteen derivatives which exhibited significant antibacterial and antifungal activities. It was observed that all derivatives were thermodynamically more stable and some of them were more chemically reactive than others. Most of the compounds, studied out here could bind near the crucial catalytic residues, HIS41, and CYS145 of the main protease, and the compounds were surrounded by other active site residues like GLY143, MET49, MET165, GLY143, HIS163, PRO168, GLU166, GLN189, and SER144. Finally, all the modified uridine derivatives were analyzed in silico ADMET and drug-like properties. Our patulous computational and statistical analysis showed that these selected uridine derivatives may use as potential inhibitors against the SARS-CoV-2 Mpro.

The photoactivity of TiO2 and ZnO deposited on cellulose and polystyrene was investigated. The synthesized catalysts were characterized by SEM, XRD, and FT-IR. The X-rays diffraction pattern showed that the TiO2 materials were mainly composed of anatase phase with a small amount of rutile phase. Peaks found for ZnO are assigned to well crystallized ZnO oxides. The SEM images confirmed the dispersion of TiO2 particles and ZnO nanofibers on cellulose and polystyrene, respectively. The photoactivity of the two catalysts was tested for the degradation of acetaminophen. Results showed that for an initial drug concentration of 10 mg/L, the removal of the pollutant under UV light in the presence of TiO2/cellulose reached 80%. Under the same conditions, ZnO/polystyrene was inactive under UV, visible and solar radiations. The study of the effect of H2O2 and K2S2O8 as oxidants showed that the peroxydisulfate (S2O82-) exhibited an intensified effect on degradation efficiency of the pollutant; in fact, in the presence of TiO2/cellulose and ZnO/polystyrene, respectively 85.4 and 93.1% of acetaminophen was removed from the contaminated solutions after adding 1mmol/L of S2O82-. The present findings reveal that under UV light, the photocatalytic systems TiO2-K2S2O8/cellulose and ZnO-K2S2O8/polystyrene show promising results for treating effluents charged with acetaminophen.

Mutual interactions of human serum albumin (HSA) with the two binuclear platinum complexes, containing [(bhq)Pt(dppm)2(Cl)Pt(bhq)(Cl)] (1) and [(bhq)Pt(dppm)2(PhMe)Pt(bhq)(CO2CF3)] (2), in which bhq=benzo[h]quinoline, and dppm=bis(diphenylphosphino) methane, were thoroughly investigated using spectroscopic and molecular modeling techniques. In this respect, fluorescence, Ultraviolet-Visible (UV-Vis) and circular dichroism (CD) spectroscopies, along with the docking and molecular dynamics simulations (MD) were utilized. Analysis of spectroscopic and MD simulation results revealed the structural alterations of HSA, upon binding to the binuclear platinum complexes, while the hydrogen bonding and van der Waals forces were found to mainly contribute to the protein-ligand intermolecular interactions. Results of far-UV CD measurements showed the strong ability of platinum complexes, in reducing the α-helical content of HSA, while other secondary structural features were increased. Due to their different chemical natures, these complexes bind to HSA in different manners. Binding constants and thermodynamic binding parameters between these complexes and HSA were calculated using the Stern−Volmer and van’t Hoff equations. Calculated thermodynamic binding parameters indicated that the interaction is spontaneous and enthalpy driven, through the static and dynamic quenching mechanisms, for complexes 1 and 2, respectively.

The adsorptive capacity of cellulose nanocrystals extracted from sugarcane bagasse using acid hydrolysis for methyl orange (MO) sequestration was investigated. The extracted nanocrystals were characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and Fourier transform infra-red spectroscopy (FTIR). Well-defined pore spaces, predominant nano range of particles (0.045 – 0.082 µm), greater crystallinity index from 1.09 to 1.21, and disappearance of peaks at 1736 and 1429 cm-1 in FTIR in addition to higher carbon content are parameters that better-define the characteristics of cellulose nanocrystals. A Two-fold improvement in monolayer adsorption capacity was obtained for cellulose nanocrystals (432.17mgg-1) described by Langmuir isotherm over bagasse (170.99 mgg-1) described by Freundlich isotherm. Adsorption processes on both adsorbents were spontaneous, exothermic and best described by pseudo second-order kinetics. Polynomial regression models appropriately predicted equations that best describe the effects of different batch adsorption parameters on MO removal with better fittingness than experimentally generated data.

Human chorionic gonadotropin (hCG) is a glycoprotein hormone that is an essential biomarker in oncology and pregnancy. The objective of this research was to examine the effect of ultrasonic irradiation (40 kHz) in various times of exposure (10 to 60 min) on the structure of hCG. The UV-Visible and near-UV CD data illustrated that ultrasonic irradiation could induce alterations in the tertiary structure of hCG and these conformational variations were irreversible. The ultrasonic-induced variations were observed in the intrinsic fluorescence emission. Furthermore, after long periods of exposure, ANS affinity to hCG incremented considerably. A transition to the random coil was observed in far-UV CD data. Ultrasonic irradiation could increment the negative surface charge on hCG. The effect of ultrasonic time revealed initial increment and eventual reduction in hCG size. After 60 min exposure, some new bands were observed at the SDS-PAGE profile of hCG. Collectively, our in vitro experiments demonstrated the sensitive balance between various noncovalent interactions in the structure of hCG could be easily disrupted after ultrasonic treatments. Results from this study are useful to achieve a better understanding of the ultrasonic irradiation physicochemical effects on proteins. Besides, can help to determine safe limits for people particularly, pregnant women.

Functionalized banana stalk (BSAC) was investigated as a potential adsorbent in removing a commonly used pharmaceutical antimalaria drug, Lumefantrine (LUMF). The raw banana stalk was chemically treated with orthophosphoric acid to enhance its adsorptive properties. The effect of LUMF initial concentration, temperature, solution pH, and contact time on the adsorption process was studied using the batch equilibrium process. The surface characteristics of the prepared adsorbent were investigated using SEM, FTIR, proximate analysis, and the Boehm titration techniques. The FTIR spectra showed notable peaks that are responsible for the adsorptive uptake of LUMF. The micrograph from the SEM showed well-developed pores which can be attributed to the effect of the acid treatment, and results from the proximate analysis showed 73.92% carbon content which is a remarkable percentage for a favorable uptake. The sips isotherm model best fitted the experimental data with an R2 = 1, and a maximum adsorption capacity of 102.1 mg/g. The pseudo-second-order kinetic model best explains the kinetics of adsorption of LUMF onto BSAC with R2 values ranging from 0.9845-0.9997. Thermodynamic studies suggest that LUMF uptake by BSAC is endothermic, spontaneous, and thermodynamically favored. BSAC was found to be effective in removing LUMF from aqueous solutions.

In this study, phosphorus trichloride (PCl3) and phosphorus triiodide (PI3) as the condensed inorganic materials were investigated based on the molecular dynamics simulation. To this purpose, molecular dynamics simulations were performed by applying force field parameters derived from the quantum chemistry approach. The potential energy data were computed at the B3LYP/6-31+G (d) and B3LYP/dgdzvpd levels of theory for different configurations of PCl3 and PI3, respectively. To determine force field parameters, a four-site all-atom force field model was used to correlate the potential energy data. Therefore, the force field parameters were applied to perform the molecular dynamics simulations. The MD simulations were performed to obtain the atomic number density, enthalpy, heat capacity, and radial distribution function in the NPT and NVT ensembles for PCl3 and PI3 dimers. There is a good consistency between the experimental data and simulation results over a wide range of experimental conditions.

The binding of ciprofloxacin (CIP) to bovine serum albumin (BSA) in the existence and absence of 6-shogaol was investigated by multiple techniques. Fluorescence spectroscopy results indicated that CIP was able to be quenching of BSA without and with 6-shogaol by way of a static mechanism. The CIP and 6-shogaol binding to BSA leads to the increase of the binding constant (Ka) value of CIP to BSA. In accordance with the minus amounts of ΔH0 and ΔS0, the functions of hydrogen bond and van der Waals forces are very important all over this special binding. In addition, the minus amounts of ΔH0 and ΔS0 for BSA-CIP in the existence of 6-shogaol have been larger than those of the absence of 6-shogaol, which illustrates the higher importance of hydrogen bonding and van der Waals forces. As indicated by the synchronized fluorescence spectroscopy at Δλ = 60 nm, the location of CIP with mixed BSA in binary and trinary systems has been nearer to Tyr residues.

ZnFe2O4/Copper slag (CS) which is an environmentally friendly and cost-effective catalyst was produced by co-precipitation methods and a thermal process. The synthesized catalyst was characterized by XRD, SEM, EDX and BET surface area analysis. The X-rays diffraction pattern confirmed that the crystal structure of ZnFe2O4 after stabilization on CS zeolite has not changed. The SEM images showed that, despite their varying sizes, the particles all have the same shape. Photocatalytic activity of the catalyst was tested for the degradation of ethylbenzene (EB) in water by UV + H2O2 method in the reverse-flow packed bed photo reactor. The process optimization and modeling were performed using the full factorial method. The initial concentration of EB = 30 ppm, pH = 9 and initial H2O2 concentration = 15 ppm were the best conditions. Under ideal process conditions, the removal efficiency of EB was greater than 99.5%. The validity of the Langmuir-Hinshelwood kinetics model was confirmed using EB photocatalytic degradation experimental results. The values of 〖∆H〗^⫲and 〖∆S〗^⫲ for the photocatalytic degradation of EB by ZnFe2O4/CS catalyst in the UV+H2O2 process were calculated based on the transition state theory and gave 1.67 kJ mol-1 and -263.057 J K-1 mol-1 respectively.