A new selective fluorogenic probe for trivalent cations

A new selective chromo-fluorogenic probe for Fe(3+), Cr(3+) and Al(3+) is reported. Detection limits are in the μM range and the fluorogenic sensing ability could be observed by the naked eye when illuminated with UV-light. No response is observed with divalent cations.     

Enzyme‐Responsive Silica Mesoporous Supports Capped with Azopyridinium Salts for Controlled Delivery Applications

The preparation of a new capped silica mesoporous material, Rh‐Azo‐S , for on‐command delivery applications in the presence of target enzymes is described. The material consists of nanometric mesoporous MCM‐41‐like supports loaded with Rhodamine B and capped with an azopyridine derivative. The material was designed to show “zero delivery” and to display a cargo release in the presence of reductases and esterases, which are usually present in the colon, mainly due to intestinal microflora. The opening and cargo release of Rh‐Azo‐S in vitro studies were assessed and seen to occur in the presence of these enzymes, whereas no delivery was noted in the presence of pepsine. Moreover, Rh‐Azo‐S nanoparticles were used to study controlled Rhodamine B dye delivery in intracellular media. HeLa cells were employed for testing the “non”‐toxicity of nanoparticles. Moreover, delivery of the dye in these cells, through internalization and enzyme‐mediated gate opening, was confirmed by confocal microscopy. Furthermore, the nanoparticles capped with the Azo group and loaded with a cytotoxic camptothecin ( CPT ) were also prepared (solid CPT‐Azo‐S ) and used as delivery nanodevices in HeLa cells. When this solid was employed, the cell viability decreased significantly due to internalization of the nanoparticles and delivery of the cytotoxic agent.     

Textile/Metal–Organic‐Framework Composites as Self‐Detoxifying Filters for Chemical‐Warfare Agents

The current technology of air‐filtration materials for protection against highly toxic chemicals, that is, chemical‐warfare agents, is mainly based on the broad and effective adsorptive properties of hydrophobic activated carbons. However, adsorption does not prevent these materials from behaving as secondary emitters once they are contaminated. Thus, the development of efficient self‐cleaning filters is of high interest. Herein, we report how we can take advantage of the improved phosphotriesterase catalytic activity of lithium alkoxide doped zirconium(IV) metal–organic framework (MOF) materials to develop advanced self‐detoxifying adsorbents of chemical‐warfare agents containing hydrolysable P? F, P? O, and C? Cl bonds. Moreover, we also show that it is possible to integrate these materials onto textiles, thereby combining air‐permeation properties of the textiles with the self‐detoxifying properties of the MOF material.     

Development and Validation of a High-Performance Thin-Layer Chromatographic Method,with Densitometry,for Quantitative Analysis of Tizoxanide (a Metabolite of Nitazoxanide) in Human Plasma

JPC – Journal of Planar Chromatography – Modern TLC - A new simple, rapid, and selective high-performance thin-layer chromatographic (HPTLC) method with metronidazole as the internal...     

The role of amide ligands in the stabilization of Pd(II) tricoordinated complexes: is the Pd–NR2 bond order single or higher?

The existence of tricoordinated Pd(II) complexes has been a matter of controversy for a long time. The recent X-ray characterization of a family of Pd complexes [PdArXL] allowed to certify the existence of true tricoordinated Pd(II) species. The unique role played by the amido ligand (X = NR₂), among a family of X ligands, was noticed in a previous computational work. Here, the influence of the R substituents at the amide and the nature of the Pd–N_amido bond are theoretically analyzed. The relative stability of d ⁸ tricoordinated [PdLAr(NR₂)] complexes versus d ⁸ tetracoordinated derivatives as a function of the R substituents is studied by analyzing the two most common ways to fill the vacant coordination site in a tricoordinated complex: solvent coordination (with tetrahydrofuran as solvent), or dimerization giving [(μ-NR₂)₂Pd₂L₂Ar₂]) complexes. The nature of the Pd–N bonding interaction is analyzed using several theoretical schemes as molecular orbitals, QTAIM, ELF and NBO. Each of these schemes suggests that the order of the Pd–N bond in this family of complexes is higher than one. An asymmetric π interaction between the nitrogen lone pair and the LUMO over the tricoordinated Pd center is proposed as an important source of additional stabilization of tricoordinated species provided by amido ligands.     

Derivatives of benzo[5,6]cyclohepta[1,2-b]thiophene. Synthesis of 2,3,7,8-tetrahydro-3-oxothieno[1,2-b]cyclohepta[5,6,7-de]isoquinoline and 1,2,3,7,8,11b-hexahydro-3-oxothieno[1,2-b]cyclohepta[5,6,7-de]isoquinoline

The synthesis of the title compounds was carried out by cyclization via isocyanate of (E)-4,5-dihydro-10H-benzo[5,6]cyclohepta[1,2-b]-thiophene-10-ylideneacetic acid and 4,5-dihydro-10H-benzo[5,6]cyclohepta[1,2-b]-thiophene-10-ylacetic acid respectively, which were obtained by the Wadsworth-Emmons modification of the Wittig reaction of 4,5-dihydro-10H-10-oxobenzo[5,6]cyclohepta[1,2-b]thiophene and triethyl phosphonacetate. The structures of these new compounds are described.     

Monitoring of metabolic profiling and water status of Hayward kiwifruits by nuclear magnetic resonance

The metabolic profiling of kiwifruit (Actinidia deliciosa, Hayward cultivar) aqueous extracts and the water status of entire kiwifruits were monitored over the season (June-December) using nuclear magnetic resonance (NMR) methodologies. The metabolic profiling of aqueous kiwifruit extracts was investigated by means of high field NMR spectroscopy. A large number of water-soluble metabolites were assigned by means of 1D and 2D NMR experiments. The change in the metabolic profiles monitored over the season allowed the kiwifruit development to be investigated. Specific temporal trends of aminoacids, sugars, organic acids and other metabolites were observed.The water status of kiwifruits was monitored directly on the intact fruit measuring the T₂ spin-spin relaxation time by means of a portable unilateral NMR instrument, fully non-invasive. Again, clear trends of the relaxation time were observed during the monitoring period.The results show that the monitoring of the metabolic profiling and the monitoring of the water status are two complementary means suitable to have a complete view of the investigated fruit.     

Determination of Pb and Cu by Anodic Stripping Voltammetry Using Glassy Carbon Electrodes Modified with Mercury or Mercury-Nafion Films

 Two different approaches for the modification of glassy carbon electrodes using a mercury film and mercury-nafion are compared. The mixture of mercury(II) chloride solution with a nafion solution diluted in ethanol is used to coat the polished glassy carbon surface. The modified working electrodes are compared when measuring Pb and Cu in real seawater samples. An optimisation of the parameters during the formation of the films was done to obtain well-defined stripping peaks. The type of inert supporting electrolyte and the pH play an important role on the sensitivity of the measurement. Results for Pb and Cu determinations show the advantages of Hg-nafion modification as an alternative method. These advantages include a shorter modification time, the avoidance of Hg solutions during the formation of the Hg film and an improved sensitivity for Pb determination. Received March 16, 1999. Revision April 24, 2000.     

Ion binding to polyelectrolytes: Monte Carlo simulations versus classical mean field theories

The influence of ion size and surface charge model in titrations of ionizable polyelectrolytes is studied by means of the Semi Grand Canonical Monte Carlo simulation method in the context of the primitive model. Three models describing a discrete distribution of charged functional groups on the polyelectrolyte and different values for the radius of the background electrolyte spanning from ionic to hydrated radii values were analyzed. The polyelectrolyte titrations were simulated by calculating the degree of ionization versus pH curves at two ionic strengths. The results allow us to quantify the impact of the sizes of the background salt ions and surface functional groups of the polyelectrolyte on the dissociation degree. This influence is explained in terms of the effectiveness of the screening of the charged surface sites. Finally, by comparison with the Non-Linear Poisson–Boltzmann model, the influence of ionic correlations and finite size of the solution ions is assessed.     

Beam walk-off suppression in photorefractive polymer-based coherence domain holography

The effect of beam walk-off is known to reduce the overlap region of the writing beams in coherence domain holographic imaging. In photorefractive (PR) polymer devices this problem is particularly pronounced because of the restrictions that are imposed by the slanted recording geometry. Here, we demonstrate that by optically demagnifying the image bearing signal beam the field of view can be enhanced by a factor of 8. In addition, we found that the area ratio of the writing and readout beams determines both the PR performance and the depth resolution. In a second approach, we show that by changing the recording geometry from transmission to reflection the field of view can be almost fully recovered.