Search

Copyright of Archives of Razi Institute is the property of Institut Razi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Using density functional theory, three noncovalent interactions and mechanism of covalent functionalization of drug artemisinin onto γ-Fe2O3 nanoparticles have been investigated. Quantum molecular descriptors of noncovalent configurations were studied. It was specified that binding of drug artemisinin with γ-Fe2O3 nanoparticles is thermodynamically suitable. Hardness and the gap of energy between LUMO and HOMO of artemisinin drug are higher than those of noncovalent artemisinin-γ-Fe2O3 nanoparticle configurations, showing the reactivity of artemisinin increases in the presence of γ-Fe2O3 nanoparticles. Artemisinin can bond to γ-Fe2O3 nanoparticles through carbonyl group. The activation energies, the activation enthalpies and the activation Gibbs free energies of this reaction were calculated. The activation parameters and thermodynamic data indicate that this reaction is exothermic and spontaneous and can take place at room temperature. These results could be generalized to other similar drugs. [ABSTRACT FROM AUTHOR]

The mechanism and regioselectivity of the Diels-Alder cycloaddition reaction between 9- (methoxymethyl)anthracene and citraconic anhydride are explored using the valuable density functional theory (DFT) methods. The solvent effects are considered using the polarizable continuum model in the toluene solution. Due to a small electrophilicity difference of the reactants, the reaction has a low polar character. The investigated Diels-Alder reaction has a normal electron demand character. Depending on the respective position of substituents in the cycloadducts (head-to-head (ortho) or head-to-tail (meta)) the reaction can be progressed via two different pathways: ortho and meta. Due to a very high activation energy, the meta pathway is rejected. The product of the ortho pathway is demonstrated to be the final product of the reaction in the toluene solution. The obtained DFT results are in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

In this work, the biosensor behavior of the DA-DA dinucleotide (DA2N) in the presence of DL-lysine (DLL) and three different single carbon nanotubes (SWNT), i.e., (5-5), (6-6), and (7-7), is studied by molecular dynamics (MD) simulation and density functional theory (DFT) approaches. The MD simulation of the system of DA2N with DLL and various nanotubes was performed. The obtained results for the RMSD values reveal that the simulated systems are in the equilibrium. The single point energy calculations of the DA2N structure in various simulations are performed. The HOMO-LUMO gap and their corresponding orbitals are obtained for DA2N. The results indicate that the adenine ring is responsible for the charge transfer in DA2N. The calculated Fukui indices show that the nitrogen atom of the five-membered adenine ring plays a more active role in the DA2N reactivity. [ABSTRACT FROM AUTHOR]

Herein, the tetradentate N,N′-dipyridoxyl(4-methyl-1,2-phenylenediamine) [=H2L] Schiff base and its Cu(II) salen complex [Cu(L)] are newly synthesized and characterized by IR, NMR and mass spectroscopies together with the elemental analysis. In addition, their geometrical parameters, assignment of their IR bands and NMR chemical shifts of the Schiff base are calculated using density functional theory (DFT) methods. Natural bond orbital analyses were performed at the same computational level, too. In the optimized geometry of the free ligand the aromatic rings are not in the same plane. The structure of the complex is more planar, where the dianionic Schiff-base acts as a tetradentate ligand in the N,N,O-,O-manner. Two phenolic oxygen atoms and two azomethine nitrogen atoms occupy four coordination positions of the square complex. The DFT-calculated results are in good agreement with the experimental values, confirming the suitability of the optimized geometries for the Schiff base and its Cu(II) complex. [ABSTRACT FROM AUTHOR]

Herein, (E)-4-{[(2-amino-5-chlorophenyl)imino]methyl}-5-(hydroxymethyl)- 2-methylpyridin-3-ol [HL] Schiff base and its [Cu(L)Cl] complex were newly synthesized and characterized by several spectroscopic methods. In addition, density functional theory (DFT) methods were used for investigation of the tautomerization of the HL Schiff base, structural parameters of HL and [Cu(L)Cl] species, assignment of the IR vibrational bands and the NMR chemical shifts as well as natural bond orbital (NBO) analyses. The most stable tautomer of the HL Schiff base is the enol form of the meta isomer. The optimized geometry of the free HL Schiff base is not planar. The L- acts as a N2O tridentate ligand, which is bonded to Cu2+ via the deprotonated phenolic oxygen, and the amine and azomethine nitrogens. The [Cu(L)Cl] has a square planar geometry in which the chloro ligand occupies the fourth coordination position. The DFT-computed values are in good consistency with the corresponding experimental values, confirming the suitability of the optimized geometries for HL and [Cu(L)Cl] species. According to the high-energy gaps, these compounds are stable. The atoms in molecule (AIM) analysis was used to evaluate strength of the bonding interactions and electron densities in structure of the compounds.

In recent decades, extensive research has been done on substrates (i.e., titanium and carbon) with lead dioxide coating to design a cheap anode in electrochemical systems instead of a platinized (Pt) electrode. Various factors can affect the structure and catalytic activity of lead dioxide coating. The most important of them are the type of substrate, how to prepare the substrate for the coating process and the types of lead dioxide additives. In this work, the effective factors in the preparation of the substrate were first investigated. Subsequently, the effect of neodymium as an additive on the catalytic activity of the electrode was studied. We prepared these electrodes and they were first evaluated by scanning electron microscopy (SEM), X-ray diffraction (XRD) spectrometer, voltammetry and electrochemical impedance spectrometer (EIS). The results showed that the potential of water oxidation on the modified $Pb{O}_{2\,}$ electrodes by neodymium was 2 V. Here, we used an electrochemical method to prepare perchlorate. Since the anode potential for perchlorate oxidation is near that for water oxidation, conventional electrodes can’t be used in the perchlorate electrosynthesis. To achieve high production yield in the preparation of perchlorate from chlorate, various parameters including pH, time, and current density were optimized by the Box-Behnken design of the experiment method. The optimal values for this process were obtained at pH = 11, temperature 40 °C and current density of 0.5 mA cm ^−2 . The results at the optimal condition showed that the perchlorate production yield by modified $Pb{O}_{2\,}$ electrodes was 80% in the 300 min. This value was only 60% for the unmodified $Pb{O}_{2\,}$ electrode.

At least 25 types of degenerative diseases are thought to be caused by amyloid-beta, including Alzheimer's. However, the exact mechanism of Alzheimer's is still unknown. It has been shown that amphiphilic surfactants with varying tail lengths, PC20:0 and di-C7-PC, have differing effects on the structures of Aβ (1–40) and Aβ (1–42). This paper examines the interaction between these surfactants and peptides. The calculations were performed at concentrations lower than the critical micelle concentration. Four and 12 peptides of beta-amyloid isomers regimens were used for each simulation. Direct and indirect behavioral effects were extensively investigated. A number of critical analyses, including RMSD, ∆RMSF, Pi, and the hydration network, were performed to examine these peptides in the absence and presence of ligands. There can be a negative ∆RMSF for each sequence as a result of ligand or surfactant binding to that sequence; otherwise, the structure is partially or locally folded. Demonstrated that PC20:0 and di-C7-PC amphiphilic surfactants affect the aggregation of Aβ1–40 and Aβ1–42. The results of our simulations showed that the negative values of ΔRMSF match with some Pi > 1 values for both the hydrophobic and hydrophilic sides of ligands. Therefore, potential interactions between residual peptides and ligands were identified. A negative ΔRMSF did not match the Pi > 1 value, indicating the folding behavior of peptide residues. [ABSTRACT FROM AUTHOR]

Background and aims: In nanofibrous filters, morphological properties, diameter of fibers and porosity percent of media are the most filtration characteristics. Therefore, the present study aimed to optimize the electrospinning parameters for reaching to the desired values of the mentioned filter characteristics. Method: For this purpose, a study design was prepared using response surface methodology (RSM), in which electrospinning factors such as solution concentration, applied voltage and electrospinning distance were considered input variables and the fiber diameter, porosity, bead number and average bead diameter to average fiber diameter (ABD/AFD) ratio were considered the output variables. Morphological features of fibers and porosity of media were done through image processing approach of Scanning Emission Microscopy (SEM) images. Results: Maximum concentration in assessed range can provide the best morphology and also the maximum diameter. The highest correlation coefficient has been seen between fiber diameter and solution concentration (p 0.05, r=0.39). There was the significant relationship between both concentration and electrospinning distance and bead size (r=-1.6, r=0.56, respectively). Bead number was decreased specially with increase in concentration. Conclusion: Totally, RSM could well determine the relationship between input and response variables. High regression coefficient in mathematical models indicated the importance of the experimental values. The validation test shown the experimental data are in good agreement with the predicted ones.

Electrospun nanofibrous filter media have attracted considerable attention in the last decade. The present study aimed to develop the electrospun PAN (polyacrylonitrile) filter media through experimental investigations for application in high-performance air filters. For this purpose, an experimental design was proposed to assess the effect of electrospinning process conditions including solution concentration, electric voltage and nozzle-collector distance on the structural properties of filter media including the fiber diameter, percent of porosity and bead number. Optimization of electrospinning parameters was conducted through the Response Surface Methodology to obtain the desired values for fibrous media variables. The morphology of the mats (including bead number and fiber diameter) were studied using SEM images through, Microstructure Measurement image analyzer. The porosity was determined using image analysis algorithms by MATLAB. The findings indicated that the concentration is the most influencing factor on fiber diameter (r= 0.73, p0.05), so that the lower concentrations led to lower fiber diameter and more bead number. Among the electrospinning parameters, the highest correlation coefficient was achieved between porosity of PAN media and applied voltage (r=0.39, p>0.05). There was a negative relationship between fiber diameter and both percent of porosity (r=-23; p>0.05) and bead number(r=-0.53; p

Using density functional theory, the six noncovalent interactions and possible mechanisms of covalent functionalization of drug 6-thioguanine with COOH and COCl functionalized carbon nanotube (NTCOOH and NTCOCl) have been investigated. Quantum molecular descriptors of noncovalent configurations were studied. It was specified that binding of drug 6-thioguanine with NTCOOH has more binding energy than NTCOCl and can act as a favorable system for 6-thioguanine drug delivery within biological and chemical systems (noncovalent). NTCOOH and NTCOCl can bond to the amino groups of 6-thioguanine through OH (COOH mechanism) and Cl (COCl mechanism) groups, respectively. The activation energies, the activation enthalpies and the activation Gibbs free energies of six pathways were calculated and compared with each other. The activation parameters related to COOH mechanism are higher than those related to COCl mechanism and therefore COCl mechanism is suitable for covalent functionalization. These results could be generalized to other similar drugs. [ABSTRACT FROM AUTHOR]

Introduction: In normal pregnancy the maternal immune system is directed towards tolerance or suppression in order to prevent the rejection of the semi allogenic fetus. Antigen presenting cells especially dendritic cells (DCs) are the key cells in initiation and regulation of immune responses. The presence of potent immunostimulatory dendritic cells in the decidual tissue of pregnancy has been demonstrated. The aim of this study was to determine how allostimulatory activity of DCs could be affected during pregnancy. Materials and Methods: DCs were isolated from spleen of pregnant or non-pregnant Balb/c mice and co-cultured with allogenic C57BL/6 T lymphocytes prepared by nylon wool method from brachial lymph nodes. Some cultures of non-pregnant female DCs were treated by 2.5% serum obtained from pregnant mice at early, middle or late gestational periods and were used in the same mixed lymphocyte reaction (MLR) settings. Cell proliferation was measured by ³H thymidin incorporation and cytokine production was measured in supernatants of MLR cultures using ELISA method. Effect of pregnant mouse serum on expression of DC surface markers was evaluated by flow cytometry. Results: No significant difference was found between stimulatory potential of splenic DCs from pregnant and non-pregnant mice in induction of allogenic T cell proliferative response. Moreover, serum of early or late pregnancy did not have any effect on DCs function in comparison with non-pregnant mouse serum, while mid-pregnancy serum significantly inhibited allostimulatory activity of DCs. IFNγ production in co-culture of DCs treated with pregnant mouse serum was significantly lower than that of control group, however, no significant difference in IL-10 production was observed. Treatment of DCs with pregnant mouse serum did not influence the percentage of cells expressing MHCII, CD86, CD8α or CD11b. However a marked reduction of the mean fluorescence intensity of MHC-II was observed. Conclusion: Our results concerning the diminished capacity of DCs to induce production of TH1 cytokines and allogenic T cell proliferation after treatment with pregnant mouse serum reveals a new way of immunologic tolerance against semi-allogenic fetus. [ABSTRACT FROM AUTHOR]