Coordination and structural studies of crowned-porphyrins

Simple chelating agents have been synthesized using a porphyrin and a covalently linked crown-ether. Depending on the relative spatial arrangement of both motifs, the resulting ligands, either a macrotricycle or bis-macrocycles, differ one from another by their flexibility or their aptitude to chelate bivalent or trivalent cations. The coordination chemistry as well as the structural study of these ligands and complexes are reported. In the particular case of the macrotricycle, the crown-ether motif, perpendicular to the porphyrin induces a side selectivity for the coordination of lead(II) outside the cavity. Furthermore, the coordination of zinc(II) implies a change of conformation of the ligand in which the crown-ether is parallel to the porphyrin.     

Investigation of spatial self-phase modulation of silver nanoparticles in clay suspension

We have investigated the spatial self-phase modulation (SSPM) phenomena in a clay suspension containing silver nanoparticles. Silver nanoparticles (Ag-NPs) were synthesized in the space of lamellar structure of montmorillonite (MMT) by using chemical reducing agent. The UV-vis spectra of the obtained Ag-NPs showed that the intensity surface plasmon resonance (SPR) peaks increase with increasing in concentration of AgNO₃. The results from Ag-NPs UV-vis spectra were in good agreement with the structure studies performed by TEM. The SSPM phenomena manifestation of the non-linear optical property appeared only when MMT suspension filled with Ag-NPs as shown in the existence of far-field pattern. This property increased with the increase of Ag-NPs concentration and limited to small range.     

1-Aryl-3-(1<Emphasis Type="Italic">H</Emphasis>-imidazol-1-yl)propan-1-ol esters: synthesis,anti-<Emphasis Type="Italic">Candida</Emphasis>potential and molecular modeling studies

Background

An increased incidence of fungal infections, both invasive and superficial, has been witnessed over the last two decades. Candida species seem to be the main etiology of nosocomial fungal infections worldwide with Candida albicans, which is commensal in healthy individuals, accounting for the majority of invasive Candida infections with about 30-40% of mortality.

Results

New aromatic and heterocyclic esters 5a-k of 1-aryl-3-(1H-imidazol-1-yl)propan-1-ols 4a-d were successfully synthesized and evaluated for their anti-Candida potential. Compound 5a emerged as the most active congener among the newly synthesized compounds 5a-k with MIC value of 0.0833 μmol/mL as compared with fluconazole (MIC value >1.6325 μmol/mL). Additionally, molecular modeling studies were conducted on a set of anti-Candida albicans compounds.

Conclusion

The newly synthesized esters 5a-k showed more potent anti-Candida activities than fluconazole. Compounds 7 and 8 revealed significant anti-Candida albicans activity and were able to effectively satisfy the proposed pharmacophore geometry, using the energy accessible conformers (E_conf?<?20 kcal/mol).

Open image in new window

     

Optical model analysis of p+6He scattering over a wide range of energy

Optical-model analysis of proton elastic scattering from ⁶He has been carried out for eight sets of elastic scattering data at energies, 24.5, 25.0, 36.2, 38.3, 40.9, 41.6, 71.0 and 82.3 MeV/n respectively. The vector analyzing power and differential cross section for the elastic scattering of ⁶He nucleus from polarized protons at 71 MeV have been analyzed in the framework of the optical model potentials. The data are, first, analyzed in term of phenomenological potentials using the Woods-Saxon form for the real and imaginary parts supplemented by a spin-orbit potential of Thomas form. The analysis has been also performed using microscopic complex potentials.     

Synthesis,characterization, and biocompatibility of poly (acrylic acid/methyl methacrylate)-grafted-poly (ethylene-co-tetrafluoroethylene) film for prosthetic cardiac valves

The surface of poly (ethylene-co-tetrafluoroethylene) (PETFE) strip was grafted by acrylic acid (AAc) and methyl methacrylate (MMA) onto PETFE skeleton to improve the blood compatibility and reduce thrombogenicity for prosthesis. The grafting process was carried out via γ-rays technique as initiator for addition reaction. The optimal conditions were achieved by investigating the effect of different parameters during the grafting process such as exposure to irradiation dose, comonomer concentration, comonomer composition, and solvent. The surface microstructure and composition of copoly (AAc/MMA)-grafted-PETFE surface were characterized by Fourier transform infrared spectroscopy (FTIR), CHNS/O elemental analyzer, scanning electron microscopy (SEM), and electron spectroscopy for chemical analysis (ESCA). Further, heparin was introduced onto the grafted PETFE strip surface. The blood compatibility of modified strip was investigated by the determination of platelet adhesion and thrombus formation. The results indicate that the heparinized copoly (AAc/MMA)-grafted-PETFE sample is a good candidate for manufacturing the prosthetic cardiac valves.     

Controlled Crystallization of Cyano‐Bridged Cu–Pt Coordination Polymers with Two‐Dimensional Morphology

Two‐dimensional (2D) coordination polymers (CPs) have a highly accessible surface area that permits guest molecules to effectively access the micropores in the CPs. Here we report a bottom‐up synthesis of 2D cyano‐bridged Cu–Pt CP nanoflakes using trisodium citrate as a chelating agent, which controls the nucleation rate and the crystal growth. The lateral sizes of the CP nanoflakes are controlled by changing the amount of trisodium citrate used. We strongly believe that our method will be useful for the preparation of other types of 2D CP nanoflakes. The 2D CPs have many active sites for catalytic and electrochemical reactions, and furthermore the assembled CPs can be used as membrane filters.     

The Potential of Microencapsulated Self-healing Materials for Microcracks Recovery in Self-healing Composite Systems: A Review

The autonomic self-healing materials based on microcapsules have made major advancements for the repairing of microcracks in polymers and polymer composite systems. Self-healing encapsulated materials have the inborn ability to heal polymeric composites after being damaged by chemical and mechanical progressions. These intelligent micro-encapsulated self-healing materials possess great capabilities for recovering the mechanical as well aesthetic properties and barrier properties of the polymeric structures. Based on real world observations and experimental data, it is believed that microcracks and microcracking in polymeric materials can result because of many chemical and physical routes and is one of the foremost critical issues for polymeric materials. Especially in polymeric coatings, these microcracks can lead towards disastrous failure, and conventional healing systems like patching and welding cannot be used to repair microcracks at such a micro-level. Self-healing materials, especially, capsule based self-healing materials is a new field sought as an alternative to the conventional repairing techniques, requiring no manual intrusion and uncovering. This review covers the basic and major aspects of the microencapsulated self-healing approach like the effect of synthesis parameters on the size of microcapsules, healing efficiency determination, and the potential of the existing developed microencapsulated agents.     

Immunoaffinity purification and characterization of mitochondrial membrane-bound D-3-hydroxybutyrate dehydrogenase from <Emphasis Type="Italic">Jaculus orientalis</Emphasis>

Background  

The interconversion of two important energy metabolites, 3-hydroxybutyrate and acetoacetate (the major ketone bodies), is catalyzed by D-3-hydroxybutyrate dehydrogenase (BDH¹: EC 1.1.1.30), a NAD⁺-dependent enzyme. The eukaryotic enzyme is bound to the mitochondrial inner membrane and harbors a unique lecithin-dependent activity. Here, we report an advanced purification method of the mammalian BDH applied to the liver enzyme from jerboa (Jaculus orientalis), a hibernating rodent adapted to extreme diet and environmental conditions.     

Acuminatol and Other Antioxidative Resveratrol Oligomers from the Stem Bark of <em>Shorea acuminata</em>

A new resveratrol dimer, acuminatol (1), was isolated along with five known compounds from the acetone extract of the stem bark of Shorea acuminata. Their structures and stereochemistry were determined by spectroscopic methods, which included the extensive use of 2D NMR techniques. All isolated compounds were evaluated for their antioxidant activity using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (RSA) and the β-carotene-linoleic acid (BCLA) assays, and compared with those of the standards of ascorbic acid (AscA) and butylated hydroxytoluene (BHT). All compounds tested exhibited good to moderate antioxidant activity in the DPPH assay (IC₅₀s 0.84 to 10.06 mM) and displayed strong inhibition of β-carotene oxidation (IC₅₀s 0.10 to 0.22 mM). The isolated compounds were evaluated on the Vero cell line and were found to be non-cytotoxic with LC₅₀ values between 161 to 830 μM.     

Stability criteria of an immersed annulus swirling jet in a zero gravity environment

The present work deals with the stability properties of an immersed annulus swirling jet in a zero gravity environment. The considered system is composed of two streaming coaxial fluid cylinders, embedded in a third streaming fluid, where the intermediate one (annulus) has a uniform swirl speed. The fluids are immiscible, inviscid, and incompressible. The linear stability criteria of the model are discussed analytically and stability diagrams are obtained. We conclude that the radii ratio, the Weber number and the swirl number play a significant role in determining the dynamics of the developing interfacial patterns.