Sequestering ability of some chelating agents towards methylmercury(II)

A study on the interactions between CH₃Hg⁺ and some S, N and O donor ligands (2-mercaptopropanoic acid (thiolactic acid (H₂ TLA)), 3-mercaptopropanoic acid (H₂ MPA), 2-mercaptosuccinic acid (thiomalic acid (H₃ TMA)), d,l-penicillamine (H₂ PSH), l-cysteine (H₂ CYS), glutathione (H₃ GSH), N,N′-bis(3-aminopropyl)-1-4-diaminobutane (spermine (SPER)), 1,2,3,4,5,6-benzenehexacarboxylic acid (mellitic acid (H₆ MLT)) and ethylenediaminetetraacetic acid (H₄ EDTA)) is reported. The speciation models in aqueous solution and the possible structures of the complexes formed are discussed on the basis of potentiometric, calorimetric, UV spectrophotometric and electrospray mass spectrometric results. For the CH₃Hg⁺–S donor ligand systems, the formation of ML^1–z and MLH^2–z complex species is observed, together with a diprotonated MLH ₂ ^3–z species for CYS ^2?, PSH ^2? and GSH ^3? and the mixed hydrolytic one ML(OH)^?z for TLA ^2? and MPA ^2?. The dependence of the stability on ionic strength and on temperature is also analysed. In the other CH₃Hg⁺-L systems (L?=?MLT ^6?, SPER and EDTA ^4?), ML^1–z , MLH^2–z and MLH₂ ^3–z complex species are formed, together with the MLH₃ ^4–z species for SPER, the mixed hydrolytic ML(OH)^–z one for SPER and EDTA, and the M₂L^2–z for EDTA only. On the basis of the speciation models proposed, the sequestering ability of the ligands towards methylmercury(II) cation is evaluated. All S donor ligands show a good sequestering power (at 10^?11?mol?L^?1 level, in the pH range 4 to 8) following the trend MPA ^2??<?PSH ^2??<?GSH ^3??<?TLA ^2??<?CYS ^2??<?TMA ^3?, while significantly lower is the sequestering ability of MLT, SPER and EDTA (at 10^?3–10^?5?mol?L^?1 level, in the pH range 4 to 8).

A thermodynamic characterization of aqueous nanostructures of water molecules formed by prolonged contact with the hydrophilic polymer Nafion

This work investigates the physicochemical alterations of water perturbed by prolonged contact with the hydrophilic polymer Nafion, referred to as iteratively nafionized water (INW). The parameters measured are: electrical conductivity, χ μS cm^?1, heat of mixing with basic sodium hydroxide (NaOH) solutions, ΔQ _NaOH ^mix  J kg^?1, and pH. The results indicate that supramolecular aggregates of water molecules form after prolonged contact with a Nafion surface. Analytical determination by ion chromatography allows us to exclude the role of contaminants. This suggests that water may possess an exceptional self-organization capability triggered by the contact with a hydrophilic surface. Conductometric, pH-metric, and calorimetric titrations of INW were performed by the addition of NaOH solutions to determine the concentration of the aqueous nanostructures, via conductometric and pH-metric titration with NaOH solutions. Thermodynamic parameters were determined via calorimetric titration, for the process of formation of complexes between the nanostructures and the base used.     

High spin states in48Cr

The self-consistent finite Fermi-system theory with three different parameter sets is used to calculate decay energies and Gamow-Teller strength distributions of neutronrich short-lived nuclides near shell closures Z=50, N=82. Among the parameters, the role of a strong surface neutron-proton attraction and an isovector spin-orbit force is discussed. The obtainedβ-decay half-lives are compared with large-scale calculation results and with available experimental data. Some predictions for the ground state properties of other unstable closed-shell nuclei are presented.     

Interaction times in the19F+63Cu dissipative heavy ion reaction

Coherence energies extracted from excitation functions and angular distributions for the fragments emitted in the¹⁹F+⁶³Cu reaction, measured in the range θ_lab=10° to 120° at incident energies between 100 to 108 MeV (lab.), were compared to the Kun model of dissipative collisions. An overall agreement was found for the angular distributions at forward angles. The general behavior of coherence energies was also properly described and interaction times were deduced.     

A study of γ decays and octupole bands in 21Ne and 21Na

The reactions ¹⁶O(⁷Li, 2n) and ¹⁶O(⁷Li, np) populating ²¹Na and ²¹Ne have been studied at E _L=27 MeV using the GASP γ-detector array. The level schemes for ²¹Na and ²¹Ne have been extended to higher spin. The population of the bands with K=3/2 and 1/2, forming parity doublets, are compared. Preferential E1 decay between bands of opposite parity is observed in agreement with the octupole scenario. The structure of these bands can be interpreted as consisting of an instrinsic asymmetric (⁴He + ¹⁶O) structure with octupole deformation.     

Vanadyl complexes with ethylenedithiodiacetic acid

The complex formation between vanadyl ions and ethylenedithiodiacetic acid (H₂ L) has been studied at 25 °C in 0.5M-NaClO₄ as inert medium, by measuring the hydrogen ion concentration with a glass electrode. In acidic medium and in the investigated concentration ranges (2.07mM≤C _M≤7.50mM, C _L up to 12.5mM) the emf data can be explained assuming the equilibrium: $$VO^{2 + } + L^{2 - } \rightleftharpoons VOL log\beta _{101} = 2.68 \pm 0.03$$      

The occurrence of (S)-(−)-squalene-2,3-epoxide in nature: Isolation from the green alga Caulerpa prolifera

The unprecedented isolation of (S)-(?)-squalene-2,3-epoxide (1) from a natural source (green alga $\text{Caulerpa prolifera}$) is reported.     

On the stability of extremely diluted aqueous solutions at high ionic strength

An extensive study has been carried out on extremely diluted aqueous solutions (EDS). These solutions revealed a really intriguing physico-chemical behaviour, characterized by multiple independent variables. Because of their behaviour, EDS can be described as far-from-equilibrium systems, capable of self-organization as a consequence of little perturbations. In this paper we investigate the stability of the calorimetric behaviour of EDS with a high ionic force, due to the presence of the sodium chloride electrolyte. We measured the excess heats of mixing of EDS with basic solutions, both with and without a high concentration of NaCl, and compared the results. In particular, we explored these concentrations: 0.5 and 1Mmol kg⁻¹). The analysis of the experimental results shows that the calorimetric response of the EDS is stable when they are in a concentrated solution of NaCl. That is of great relevance for the eventual pharmacological action of these solutions, since it involves the interaction with fluids of complex chemical composition and high concentration.     

Partially hydroxylated polycrystalline ionic oxides: a new route toward electron-rich surfaces

Charge traps at the surface of oxide materials play a fundamental role in various chemical processes, such as the activation of supported metal clusters. In this study, combining electron paramagnetic resonance with cluster model DFT calculations, we show that excess electrons at the surface of MgO, CaO, and SrO polycrystalline materials can be generated by preparing weakly hydroxylated surfaces followed by deposition of small amounts of alkali metals. The residual OH groups present on specific sites of the partially dehydroxylated surface act as stable traps for electrons donated by the alkali metal (Na in this case) which forms a Na+ ion distant from the trapped electron. This process results in the formation of thermally stable (H+)(e-) color centers at the surface of the oxide. The procedure could be of interest for the stabilization and activation of supported metal nanoparticles with potential use in catalysis.     

Secondary metabolism of olive secoiridoids. New microcomponents detected in drupes by electrospray ionization and high-resolution tandem mass spectrometry

Olive drupe tissues have been selected as a possible source of information about the secondary metabolism of oleaceae secoiridoids. The structures of a number of new microcomponents, detected and isolated by a combined high-performance liquid chromatography (HPLC)-fraction collector/ultraviolet electrospray ionization mass spectrometry (UV/ESI-MS) apparatus, can be inferred from the data obtained by high-resolution tandem mass spectrometry in a QqTOF instrument. Some of them (1, 2, 3 and 4) are closely correlated to oleuropein. Others, such as neo-nuzhenide (5) and 2'-hydroxyoleuropein (6), typical of other oleaceae families, have never been found in olive tissues.