Dipyridinocalixcrown/diiodoperfluorocarbon binary host systems for CsI: structural studies and fluorous phase extraction of caesium

A mixture of partial cone 2,4-bis[(2-pyridylmethyl)oxy]-(1,3)-p-tert-butylcalix[4]crown-6, hexadecafluoro-1,8-diiodooctane and CsI in EtOH produces a crystalline ‘supramolecular salt’. In the solid state the caesium ion of the ‘supercation’ is encapsulated inside the cavity created by the crown ether loop, the picolyl and the inverted phenyl moieties, while the two iodide ions of the ‘superanion’ form a discrete five-component aggregate held together by co-existing hydrogen and halogen bonds. Similar calix/CsI/iodofluorocarbon adducts are shown to exist also in solution. In a prototypical study, a combination of this calixcrown and liquid octafluoro-1,4-diiodobutane acts as an effective ‘binary host’ system for the selective extraction of CsI from aqueous to fluorous phase.     

Secondary ion mass spectrometry and X-ray photoelectron spectroscopy investigation on chemical vapor deposited CeO(2-)ZrO(2)-TiO(2) thin films

Mixed CeO(2)-ZrO(2) systems have attracted widespread interest for their use in three-way catalyst (TWC) technology for automotive exhaust conversion to non-toxic products. In this work, CeO(2)-ZrO(2) thin films were deposited, via chemical vapor deposition, in order to obtain nanoscale materials with a high surface-to-volume ratio, with precise control of system properties. The addition of TiO(2) as buffer layer was also investigated. Cordierite was chosen as substrate, being the usual refractory material for catalytic mufflers. The multilayers were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). In particular, the combination of SIMS and XPS allowed us to investigate both surface and in-depth chemical composition, studying also film-intermixing phenomena induced by annealing processes.     

Metal complexes of 2-(2′-or 8′-quinolyl)benzimidazoles and benzothiazoles

Summary The copper(II), cobalt(II) and nickel(II) chloride and bromide complexes with the ligands 2-(2-quinolyl)-benzimidazole (qbi), 2-(4-methyl-2-quinolyl)benzimidazole (mqbi), 2-(4-methyl-8-quinolyl)benzothiazole (m'q'bt) have been prepared and characterized by analytical methods, magnetic measurements as well as by electronic absorption, e.s.r. and far i.r. spectra. Complexes of various stoichiometries have been isolated, namely MLX₂ (all cobalt complexes with exception of the bromide qbi complex; the chloride and bromide nickel m'q'bt and mq'bt complexes), ML₂X₂ (M=Co,L=qbi and X=Br; M=Ni, L=mqbi, X=Cl or Br, M=Ni, L=qbi, X=Cl) and ML₃X₂(M=Ni, L=qbi or mqbi, X=Br). The cobalt ion has a distorted tetrahedral N₂X₂ coordination in all the CoLX₂ complexes, whereas Co(qbi)₂Br₂ is six-coordinate. The following conclusions may be drawn for the nickel complexes: in those with the 11 metal-to-ligand molar ratio the metal ion is four-or five-coordinate; in those with the 12 and 13 ratios the metal ion is hexa-coordinate, being essentially bound to four nitrogen atoms with halogens, oxygens from water or methanol or nitrogen atoms (from the third ligand) occupying the axial positions.     

Evaluation of thin-layer chromatography methods for quality control of commercial products containing Aesculus hippocastanum, Turnera diffusa, Matricaria recutita, Passiflora incarnata, and Tilia occidentalis

In Mexico, plant-derived products with health claims are sold as herbal dietary supplements, and there are no rules for their legal quality control. Aesculus hippocastanum, Turnera diffusa, Matricaria recutita, Passiflora incarnata, and Tilia occidentalis are some of the major commercial products obtained from plants used in this region. In this paper, we describe the effectiveness of thin-layer chromatography methods to provide for the quality control of several commercial products containing these plants. Standardized extracts were used. Of the 49 commercial products analyzed, only 32.65% matched the chromatographic characteristic of standardized extracts. A significant number of commercial products did not match their label, indicating a problem resulting from the lack of regulation for these products. The proposed methods are simple, sensitive, and specific and can be used for routine quality control of raw herbals and formulations of the tested plants. The results obtained show the need to develop simple and reliable analytical methods that can be performed in any laboratory for the purpose of quality control of dietary supplements or commercial herbal products sold in Mexico.     

Oxide thin films based on ordered arrays of 1D nanostructure. A possible approach toward bridging material gap in catalysis

TiO(2) thin films based on ordered arrays of 1D nanostructures (nanorods, nanotubes) are proposed as suitable model materials in studies for bridging material and complexity gap in catalysis. The samples were prepared by anodic oxidation of Ti foils. By changing the preparation conditions (pH, procedure of application of the potential), different types of 1D nanostructure and different characteristics of the ordered array of these 1D nanostructures could be obtained. This allows studying the effect of nanodimension and 3D nanoarchitecture on the characteristics and reactivity of these catalysts. It is also shown that TiO(2) thin films characterized by a well-ordered array of titania nanorod behave as photonic materials, thus showing unique properties of light harvesting efficiency.     

Identification of the Schistosoma mansoni molecular target for the antimalarial drug artemether

Plasmodium falciparum and Schistosoma mansonii are the parasites responsible for most of the malaria and schistosomiasis cases in the world. Notwithstanding their many differences, the two agents have striking similarities in that they both are blood feeders and are targets of an overlapping set of drugs, including the well-known artemether molecule. Here we explore the possibility of using the known information about the mode of action of artemether in Plasmodium to identify the molecular target of the drug in Schistosoma and provide evidence that artemether binds to SmSERCA, a putative Ca2?-ATPase of Schistosoma . We also predict the putative binding mode of the molecule for both its Plasmodium and Schistosoma targets. Our analysis of the mode of binding of artemether to Ca2?-ATPases also provides an explanation for the apparent paradox that, although the molecule has no side effect in humans, it has been shown to possess antitumoral activity.     

Antiviral properties of lactoferrin--a natural immunity molecule

Lactoferrin, a multifunctional iron binding glycoprotein, plays an important role in immune regulation and defence mechanisms against bacteria, fungi and viruses. Lactoferrin's iron withholding ability is related to inhibition of microbial growth as well as to modulation of motility, aggregation and biofilm formation of pathogenic bacteria. Independently of iron binding capability, lactoferrin interacts with microbial, viral and cell surfaces thus inhibiting microbial and viral adhesion and entry into host cells. Lactoferrin can be considered not only a primary defense factor against mucosal infections, but also a polyvalent regulator which interacts in viral infectious processes. Its antiviral activity, demonstrated against both enveloped and naked viruses, lies in the early phase of infection, thus preventing entry of virus in the host cell. This activity is exerted by binding to heparan sulphate glycosaminoglycan cell receptors, or viral particles or both. Despite the antiviral effect of lactoferrin, widely demonstrated in vitro studies, few clinical trials have been carried out and the related mechanism of action is still under debate. The nuclear localization of lactoferrin in different epithelial human cells suggests that lactoferrin exerts its antiviral effect not only in the early phase of surface interaction virus-cell, but also intracellularly. The capability of lactoferrin to exert a potent antiviral activity, through its binding to host cells and/or viral particles, and its nuclear localization strengthens the idea that lactoferrin is an important brick in the mucosal wall, effective against viral attacks and it could be usefully applied as novel strategy for treatment of viral infections.     

Coordination studies on supramolecular chiral ligands and application in asymmetric hydroformylation

In this study we introduce a series of monodentate pyridine-based ligands for which the phosphorus coordination mode to rhodium can be controlled by the binding of Zn(II)-templates to the pyridyl group. A series of monodentate phosphoroamidite and phosphite ligands have been prepared and studied under hydroformylation conditions by in situ high-pressure NMR and IR techniques. These studies reveal the exclusive formation of rhodium hydride complexes in which the phosphorus atom of the ligand resides in an axial position, trans to the hydride, but only after addition of Zn(II)-template. In the absence of these templates the usual mono-coordinated rhodium hydrido complexes are formed, with the phosphorus ligated in the equatorial plane, cis to the hydride. The catalytic performance of these complexes is evaluated in asymmetric hydroformylation of unfunctionalised internal alkenes in which the supramolecular change is reflected in higher activity and selectivity.