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Silver nanoparticles (AgNPs) synthesized with aqueous extracts of Pterocladiella capillacea presented antibacterial activity against Staphylococcus aureus. AgNP preparation was optimized, leading to elongated spheres with a mean diameter of 17.42 nm. The minimum inhibitory concentration (MIC) was 0.74 μgAg mL−1, the lowest reported up to date for algae-stabilized AgNPs.

A mixture of strontium carbonate, hydroxide and oxide was prepared by thermal decomposition of SrCO3 and employed as catalyst in the decomposition of the chemical warfare agent simulant methyl paraoxon, by means of its transesterification with 1-propanol. The catalyst, which was characterized by N2 physisorption (BET method), temperature programmed desorption (CO2-TPD), Fourier Transform Infrared spectroscopy (FTIR), X-Ray diffraction (XRD) and Raman spectroscopy, promoted rate enhancements of the order of 107-fold in comparison to the spontaneous propanolysis reaction, the greatest catalytic effect promoted by metal oxide-based catalysts ever reported for this reaction. Compared to the fresh catalyst, the catalyst directly stored in the reaction solvent showed similar catalytic performance. Analysis of the reaction products by liquid chromatography with electrospray ionization mass spectrometry detection confirmed the transesterification of the substrate leading to dimethyl n-propyl phosphate, a product structurally related to a family of trialkyl phosphate flame retardants.

The molecular recognition of the carboxylatopillar[5]arene on methamphetamine showed interconversion between H2:G H:G stoichiometries with dependence on drug concentration. The study simulated conditions of severe metabolic acidosis (pH 7.00) and presented intelligent and promising dynamics for the removal of overdosed drugs or poisons in the circulatory system.

We report the targeted decomposition of the organophosphate methyl paraoxon by means of its transesterification with 1-propanol catalyzed by magnesium oxide. Catalyst characterization by energy dispersive X-ray fluorescence (EDXRF), nitrogen adsorption/desorption measurements (BET and BJH methods), and temperature programmed desorption of CO2 (CO2-TPD) showed that the employed MgO presents properties favorable for the methyl paraoxon adsorption and transesterification to occur. A thorough kinetic investigation showed that rate enhancements up to 3 × 106-fold can be achieved in comparison with the spontaneous propanolysis of the substrate, and that the material can be used in additional cycles without loss of catalytic activity, with the catalyst recovery achieved through a simple washing procedure. Energies for adsorption of 1-propanol and methyl paraoxon onto a MgO model surface were obtained by density functional theory calculations, which showed that the latter displays a stronger affinity for the catalyst surface, and that the reaction should proceed with methyl paraoxon and 1-propanol molecules juxtapositioned at adjacent Mg2+ sites, with nucleophilic and electrophilic centers ca. 2.4 A away from each other. Additionally, MgO also promoted rate enhancements up to 5 × 104-fold in the propanolysis of a further range of representative phosphate triesters, and in most of the cases the final transesterified products are trialkyl phosphates structurally related to a family of flame-retardants. The results thus provide insights into the development of novel systems for the targeted conversion of organophosphorus compounds into value-added products by employing simple, highly efficient, and low-cost metal oxide catalysts.

The study of host-guest complexation between reactive 2-carboxyphthalanilic acid (CPA) and two cationic pillararenes has been carried out. Host-guest complexation with significant kinetic effects was observed only with the smaller cavity size pillararene (P5A). Kinetics in the pH range 1.50-6.40, ESI-MS

Quenching of the fluorescence of pyrene by AuCl4− ion was investigated in aqueous micellar solutions of hexadecyltrimethylammonium chloride (CTAC) and 3-(N,N-dimethylmyristylammonio)propanesulfonate (SB3–14) in the presence of 0.010 mol L−1 HCl. Because AuCl4− is excluded from anionic sodium dodecyl sulfate (SDS) micelles due to electrostatic repulsion effects, no quenching of pyrene fluorescence by AuCl4− was observed in micellar SDS. Absorption spectral shifts show that AuCl4− binds strongly to both CTAC and SB3–14 micelles and time-resolved fluorescence results indicate that the quenching of the fluorescence of micelle-solubilized pyrene by AuCl4− is dynamic in nature. Fits of the pyrene fluorescence decays with the Tachiya model for micelle quenching in the limit of slow exchange of quenchers between the aqueous phase and micelles provided estimates of the micelle aggregation numbers that are slightly smaller than those determined with other quenchers, and intramicellar quenching rates 3–4 times higher than those observed with known collisional quenchers. The strong interaction of AuCl4− with SB3–14 and CTAC led to the stabilization of gold nanoparticles, highlighting the use of zwitterionic surfactants for the synthesis of stable and biocompatible gold nanoparticles.

Designing artificial enzymes with tailored molecular interactions between the substrate and active site is of major intellectual and practical significance. We report the improved catalytic efficiency of a supramolecular polymer/surfactant complex comprised of PAIM–, a poly(acrylic acid) derivative with imidazole groups attached to the polymer by amide bonds, and the cationic surfactant cetyltrimethylammonium bromide (CTAB). Supramolecular complex formation, at concentrations below the respective CMC values, provides convenient hydrophobic pockets for the reactants close to the multiple catalytic centers, where imidazole and carboxylate groups act as nucleophiles for the degradation of a model phosphate triester, delivering the highly efficient performance of the supramolecular catalysts. Catalytic effects are on the order of thousands for nucleophilic catalysis and are higher by 2 orders of magnitude for the supramolecular polymer/surfactant complex at pH 9. The reported supramolecular catalytic complexe...

Er2O3/Al2TiO5 and Al2TiO5 were evaluated as catalysts for the propanolysis of the organophosphate pesticide dimethyl 4-nitrophenyl phosphate (methyl paraoxon). The solid catalysts were characterized by energy-dispersive X-ray fluorescence (EDXRF), N2 physisorption (BET and BJH methods), and scanning and transmission electron microscopy (SEM and TEM). Physical–chemical characterizations revealed that the erbium content is 11.7% w/w in the novel solid and results in improved catalyst performance when compared with Al2TiO5, with textural properties favorable for methyl paraoxon diffusion in agglomerates composed of polydisperse spherical nanoparticles. Kinetic measurements at 80 °C show that the Er2O3/Al2TiO5 catalyst promotes a catalytic effect of at least 7 × 105-fold when compared with the first-order rate constant of the spontaneous propanolysis of methyl paraoxon.

We report the dephosphorylation reactions of the organophosphates diethyl 2,4-dinitrophenyl phosphate (DEDNPP) and dimethyl 4-nitrophenyl phosphate (methyl paraoxon) by the oxime 2-(hydroxyimino)-N-phenyl-acetamide (Ox 1). Rate enhancements of 107-fold over the rate constant for the spontaneous hydrolysis are observed in aqueous medium in presence of the anionic form of the oxime. Ox 1 represents a new family of nucleophiles which could be used for the degradation of toxic organophosphates. Copyright © 2016 John Wiley & Sons, Ltd.

A reacao entre um novo derivado de imidazol, 3,5-bis((1H-imidazol-1-il)metil)anilina (BIm), e o triester de fosfato dietil 2,4-dinitrofenil fosfato (DEDNPP), que procede por um mecanismo SN2(P), e substancialmente acelerada em presenca do surfactante cationico brometo de cetiltrimetrilamonio (CTAB) e do surfactante anionico dodecil sulfato de sodio (SDS). Tal efeito micelar atipico ilustra o emprego de efeitos hidrofobicos dos reagentes para otimizar o efeito catalitico de micelas aquosas. Tal observacao e importante e util no planejamento de modelos mimeticos de reacoes biologicas, ja que a melhoria da incorporacao dos reagentes aumentara efetivamente a qualidade dos sistemas biomimeticos, sendo que ambos os surfactantes cationico e anionico poderao atuar como nanoreatores homogeneos, concentrando os reagentes neutros hidrofobicos. The reaction of a new imidazole derivative, 3,5-bis((1H-imidazol-1-yl)methyl)aniline (BIm), and the model triester diethyl 2,4-dinitrophenyl phosphate (DEDNPP), which proceeds via a S N 2(P) mechanism, is substantially enhanced in the presence of either cationic cetyltrimethylammonium bromide (CTAB) or anionic sodium dodecyl sulfate (SDS). This unusual micellar effect illustrates the use of the hydrophobic character of the reactants to enhance micellar catalysis. This is an important and useful guideline in planning mimics for biological reactions, because improving incorporation will increase the quality of the biomimetic systems, and both cationic or anionic surfactants will act as homogeneous nanoreactors concentrating the neutral, hydrophobic reactants.

The phosphorylation of imidazole by two activated phosphate diesters and a triester gives phosphorylimidazole derivatives that are stable enough in aqueous solution to be observed and identified by ESI-MS/MS and NMR. Half-lives ranging from hours to days (in the case of the monoethyl ester) show that it is possible to design molecules with variable half-lives with potential to be used for biological intervention experiments as possible inhibitors of biosignaling processes or as haptens for the generation of antibodies.

The high rate of spontaneous hydrolysis of tris-2-pyridyl phosphate (TPP) is explained by the activating effects of the non-leaving ("spectator") groups on P-OAr cleavage, and not by intramolecular catalysis. Previous work on phosphate-transfer reactions has concentrated on the contributions to reactivity of the nucleophile and the leaving group, but our results make clear that the effects of the non-leaving groups on phosphorus can be equally significant. Rate measurements for three series of phosphate triesters showed that sensitivities to the non-leaving groups are substantial for spontaneous hydrolysis reactions, although significantly smaller for reactions with good nucleophiles. There are clear differences between triaryl and dialkyl aryl triesters in sensitivities to leaving and non-leaving groups with the more reactive triaryl systems showing lower values for both β(LG) and β(NLG). Intramolecular catalysis of the hydrolysis of TPP by the neighbouring pyridine nitrogens is insignificant, primarily because of their low basicity.