Coordination compounds of some transition metal ions with new Schiff base ligand derived from dibenzoyl methane. Structural characterization,thermal behavior,molecular structure,antimicrobial, anticancer activity and molecular docking studies

Series of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes were prepared with tetradentate Schiff base ligand derived by condensation of 2‐aminophenol with dibenzoylmethane. The novel Schiff base H₂L (2–2′‐((1Z,1Z’)‐(1,3‐diphenyl propane‐1,3 diylidene) bis (azanylylidene) diphenol) and its binary metal complexes were characterized by physicochemical procedures i.e. elemental analysis, FT‐IR, UV–Vis, thermal analyses (TGA/DTG), mass spectrometry, magnetic susceptibility and conductometric measurements. On the basis of these studies, an octahedral geometry for all these complexes was proposed expect Ni(II) complex which had tetrahedral geometry. Molar conductivity values revealed that the complexes were electrolytes except Mn(II), Zn(II) and Cd(II) complexes were non electrolytes. The ligand bound to the metal ions via two azomethine N and two phenolic OH as indicated from the IR and ¹H NMR spectral study. The molecular and electronic structures of H₂L and its zinc complex were optimized theoretically and the quantum chemical parameters were calculated. The antimicrobial activity against a number of bacterial organisms as Streptococcus pneumonia, Bacillus Subtilis, Pseudomonas aeruginosa and Escherichia coli and fungi as Aspergillus fumigates, Syncephalastrum racemosum, Geotricum candidum and Candida albicans by disk diffusion method were screened for the Schiff base and its complexes. The Cd(II) complex has potent antimicrobial activity. Anticancer activity of the Schiff base ligand and its metal complexes were evaluated in human cancer (MCF‐7 cells viability). The Cr(III) complex exhibited higher activity than other complexes and ligand. Molecular docking was used to predict the binding between Schiff base ligand (H₂L) and its Zn(II) complex and the receptors of RNA of amikacin antibiotic (4P20) and human‐DNA‐Topo I complex (1SC7). The docking study provided useful structural information for inhibition studies.     

Small Ubiquitin-Like Modifier Protein 3 Enhances the Solubilization of Human Bone Morphogenetic Protein 2 in <Emphasis Type="Italic">E. coli</Emphasis>

Small ubiquitin-like modifier (SUMO) fusion technology is widely used in the production of heterologous proteins from prokaryotic system to aid in protein solubilization and refolding. Due to an extensive clinical application of human bone morphogenetic protein 2 (hBMP2) in bone augmentation, total RNA was isolated from human gingival tissue and mature gene was amplified through RT-PCR, cloned (pET21a), sequence analyzed, and submitted to GenBank (Accession no. KF250425). To obtain soluble expression, SUMO3 was tagged at the N-terminus of hBMP2 gene (pET21a/SUMO3-hBMP2), transferred in BL21 codon+, and ~?40% soluble expression was obtained on induction with IPTG. The dimerized hBMP2 was confirmed with Western blot, native PAGE analysis, and purified by fast protein liquid chromatography with 0.5 M NaCl elution. The cleavage of SUMO3 tag from hBMP2 converted it to an insoluble form. Computational 3D structural analysis of the SUMO3-hBMP2 was performed and optimized by molecular dynamic simulation. Protein-protein interaction of SUMO3-hBMP2 with BMP2 receptor was carried out using HADDOCK and inferred stable interaction. The alkaline phosphatase assay of SUMO3-hBMP2 on C2C12 cells showed maximum 200-ng/ml dose-dependent activity. We conclude that SUMO3-tagged hBMP2 is more suited for generation of soluble form of the protein and addition of SUMO3 tag does not affect the functional activity of hBMP2.     

One-Pot Synthesis of Dihydropyrimidinones/Thiones Catalyzed by White Marble a Metamorphic Rock: an Efficient and Reusable Catalyst for the Biginelli Reaction

In this work, we report a simple, efficient and green protocol for the synthesis of dihydropyrimidinones/thiones (products of Biginelli reaction) by the use of white marble as an effective heterogeneous catalyst. Short reaction times, high product yields, simple processing procedure and reusability of the catalyst are the superior characteristics of this protocol.     

Magnetic and Heat Resistant Poly(imide-ether) Nanocomposites Derived from Methyl Rich 9<Emphasis Type="Italic">H</Emphasis>-xanthene: Synthesis and Characterization

In this study a new series of magnetic and heat resistant nanocomposites were prepared based on a highly soluble poly(imide-ether) (PIE) reinforced with two different types of magnetic nanoparticles via a solution intercalation technique. New PIE with good solubility and desired molar mass containing bulky xanthene rings and amide groups in the side chains was synthesized via thermal cyclization of the poly(amic acid) precursor, obtained from the reaction of a new diamine derived from 9H-xanthene and 4,4′-oxydiphthalic dianhydride (ODPA). Improved solubility was attributed to the presence of xanthene group and flexible ether linkage in the polyimide backbones that reduce the chain-chain interaction and enhance solubility by penetrating solvent molecules into the polyimide chains. Fe₃O₄ nanoparticles (MNPs) which synthesized from chemical co-precipitation route were coated with silica (SiO₂), sequentially with (3-aminopropyl)triethoxysilane and poly-melamine-terephthaldehyde (MNPs-PMT), and then separately dispersed in the poly(amic acid) solutions and thermally imidized to form PIE/Fe₃O₄ and PIE/MNPs-PMT nanocomposites. The nanostructures and properties of the resultant materials were investigated using FTIR spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The properties of the nanocomposites were strongly related to the dispersion and interaction between the nanoparticles and PIE matrix. The thermogravimetric analysis (TGA) results showed that the addition of MNPs-PMT nanoparticles resulted in a substantial increase in the thermal stability of the corresponding PIEN. The temperature at 10% weight loss (T₁₀) was increased from 416 °C to 428 °C for PIEN containing 3 wt% MNPs-PMT as compared to neat PIE, as well the char yield enhanced. Furthermore, the MNPs-PMT nanoparticles had better dispersion in the polymer matrix due to the strong intermolecular hydrogen bond interactions between the NH and C=N groups of surface-modified nanoparticles and the PIE matrix than the uncoated Fe₃O₄ nanoparticles, and exhibited a better intercalated morphology and improved thermal properties. Also, the PIEN nanocomposites under applied magnetic field exhibited the hysteretic loops of the superparamagnetic nature.     

Distinct Electron Conductance Regimes in Bacterial Decaheme Cytochromes

Shewanella oneidensis MR‐1 gains energy by extracellular electron transfer to solid surfaces. They employ c‐type cytochromes in two Mtr transmembrane complexes, forming a multiheme wire for electron transport across the cellular outer membrane. We investigated electron‐ and hole‐transfer mechanisms in the external terminal of the two complexes, MtrC and MtrF. Comparison of computed redox potentials with previous voltammetry experiments in distinct environments (isolated and electrode‐bound conditions of PFV or in vivo) suggests that these systems function in different regimes depending on the environment. Analysis of redox potential shifts in different regimes indicates strong coupling between the hemes via an interplay between direct Coulomb and indirect interactions through local structural reorganization. The latter results in the screening of Coulomb interactions and explains poor correlation of the strength of the heme‐to‐heme interactions with the distance between the hemes.     

Atrane complexes chemistry as a tool for obtaining trimodal UVM-7-like porous silica

Abstract

The use of atrane complexes as hydrolytic precursors enables the homogeneous incorporation of manganese (25 ≤ Si/Mn ≤ 48) throughout the porous walls of the nanoparticles of a surfactant-templated bimodal mesoporous silica (UVM-7). The subsequent leaching of the manganese nanodomains allows adding controlled microporosity to the host silica framework. The resulting final silica material presents three pore systems structured at different length scales: interparticle textural-type macroporosity (ca. 43.2 nm), ordered intraparticle mesoporosity (ca. 2.63 nm; after template removal), and well-dispersed microporosity (< 2 nm; as consequence of the lixiviation of the Mn-rich domains). The good dispersion of the guest element (Mn) in the silica intermediate provided by the atrane route is responsible for the disordered but regular microporosity achieved.     

Synthesis and characterizations of various polyvinyl pyrrolidon/hydroxyl ethyl methacrylate nanocomposite hydrogels as drug delivery systems

Using polymer hydrogels and nanocomposites hydrogels still promising materials for many applications. Polyvinyl pyrrolidone (PVP) has been used with various polymers synthetic and natural for different applications. In this study PVP and hydroxyl ethyl methacrylate (HEMA) copolymer hydrogels were prepared by the aid of gamma radiation and the PVP/HEMA nanocomposite hydrogels were obtained by in situ adsorption and reduction method of iron salts and silver nitrates (AgNO₃) to form PVP/HEMA-Fe₃O₄ and PVP/HEMA-Ag nanocomposites. The prepared hydrogels and the formed nanoparticles were studied by various techniques; FTIR, TEM, SEM and also the gel content and swelling behavior were evaluated. The prepared hydrogels and nanocomposites hydrogels were examined as drug delivery systems for Ciprofloxacin HCl as model drug. The PVP/HEMA-Fe₃O₄ nanocomposite gave the suitable load and release behavior towards Ciprofloxacin HCl.     

Validated HPTLC and HPLC methods for determination of fluorometholone and sodium cromoglycate in presence of their impurities and degradation products; application to kinetic study and on rabbit aqueous humor

Fluorometholone (FLM) and Sodium Cromoglycate (CMG) are co-formulated in ophthalmic preparation and showed marked instability under different conditions. Two specific, sensitive and precise stability-indicating chromatographic methods have been developed and validated for their determination in the presence of their degradation products and FLM impurity. Ten components were efficiently separated by them. The first method was HPTLC-spectrodensitometry, where the separation was achieved using silica gel 60?F₂₅₄ HPTLC plates and developing system of ethyl acetate: methanol (9:1, v/v). The second method was a reversed phase HPLC associated with kinetic study of the degradation process and was successfully applied for determination of the studied compounds in spiked rabbit aqueous humor. The mobile phase was acetonitrile: methanol: 0.05?M potassium dihydrogenphosphate (0.1% trimethylamine); pH 2.5, adjusted with orthophosphoric acid (20: 30: 50, by volume). In both methods, the separated components were detected at 240?nm and system suitability was checked. Good correlation was obtained in the range of 0.10–24.00 and 0.20–48.00?µg band^?1, for FLM and CMG by HPTLC. While for HPLC, the linearity ranges from 0.01–50.00 and 0.05–50.00?µg?mL^?1 for both drugs. The methods were applied in pharmaceutical formulation, where they were compared to the reported method with no significant difference.     

Adsorption of Molybdenum on Titania from Aqueous Solutions

The adsorption of Mo from dilute aqueous solutions (10(-3) to 3x10(-2) M) is effected on three samples of titania, two are anatase and the third is P25, which is composed of rutile and anatase. The adsorption isotherms at 298, 318, and 338 K are analyzed using a Langmuir linear equation. The isotherms on P25 showed a distinct inflection point that is reproduced by two linear portions, indicating different adsorption regimes. This adsorption behavior is explained as follows: with low amount adsorbed the adsorption is initiated by protonation of the basic hydroxyls on which the negatively charged MoO(4)(2-')s are adsorbed, and this is accompanied by an increase in the pH of the impregnating solution. At higher adsorption the coordinatively unsaturated Ti(4+) sites participate in the process, leading to a decline in the initial increase in pH. In the case of the two anatase samples the low surface area resulted in poor distribution of adsorption sites; consequently, the distinction between the two modes of adsorption was not entirely clear. The higher adsorption site density in the case of anatase is accompanied by a lower surface coverage, θ, than that for P25. The heat of adsorption, Q, on the three titania samples showed a linear increase with θ, which is represented by the regression equation: -Q=95.77θ-4.25 (R(2)=0.993). Copyright 2001 Academic Press.