Structural and dynamical properties of the Hg2+ aqua ion: a molecular dynamics study

Molecular dynamics simulations of the Hg2+ ion in aqueous solution have been carried out using an effective two-body potential derived from quantum mechanical calculations. A stable heptacoordinated structure of the Hg2+ first hydration shell has been observed and confirmed by extended X-ray absorption fine structure (EXAFS) experimental data. The structural properties of the Hg2+ hydration shells have been investigated using radial and angular distribution functions, while the dynamical behavior has been discussed in terms of reorientational correlation functions, mean residence times of water molecules in the first and second hydration shells, and self-diffusion coefficients. The effect of water-water interactions on the Hg2+ hydration properties has been evaluated using the SPC/E and TIP5P water models.     

Synthesis and characterization of new polydiolcitrates with tunable properties

Polydiolcitrates are an emerging class of biocompatible polyesters with a great potential in the field of biomedicine and packaging for food and drug materials. In this work, a new type of (co‐)polydiolcitrates made of citric acid (CA) and ethylene glycol (EG) and/or poly(ethylene glycol) (PEG) is investigated. By varying both the EG/PEG and the CA/diol molar ratios, materials exhibiting very different swelling behavior, mechanical and thermal properties are obtained. In particular, the substitution of EG segments with longer and flexible PEG ones results in an increase in crosslinking density, with remarkable effects on swelling capacity, glass transition temperature, and Young modulus. Moreover, polyesters with CA/diol molar ratio equal to 1:1 exhibit shape memory properties, with full capacity of keeping the temporary shape and high capacity of recovering the original shape. This work demonstrates that the appropriate choice of polyester composition allows modulating the sample properties, that permits to these materials to cover a wide range of possible applications. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3713–3720     

Phytochemical analysis of non-volatile fraction of Artemisia caerulescens subsp. densiflora (Viv.) (Asteraceae), an endemic species of La Maddalena Archipelago (Sardinia – Italy)

Artemisia caerulescens subsp. densiflora Viv. is a rare endemic species from Corsica and Sardinia. We studied a sample collected from Razzoli, an island of the La Maddalena Archipelago. The polar secondary metabolites content of this species was investigated for the first time in this study showing the presence of sesquiterpenoids, flavonoids, caffeoylquinic acids and a coumarin, with the presence of several compounds already recognised in this genus. The metabolites composition was analysed in two different phenological stages, post blooming and flowering. During the blooming stage, the plant showed a molecular pattern mainly represented by sesquiterpenes and sterols with a minor amount of phenolics, while in flowering stage the molecular pattern was more rich in flavonoids and phenylpropanoids.     

Environmental and food analysis by desorption atmospheric pressure photoionization‐mass spectrometry

Desorption atmospheric pressure photoionization‐mass spectrometry (DAPPI‐MS) is a versatile surface analysis technique for a wide range of analytes, especially for neutral and non‐polar analytes. Here, a set of analytes typically found in environmental or food samples was analyzed by DAPPI‐MS. The set included five polyaromatic hydrocarbons (PAHs), one N‐PAH, one brominated flame retardant, and nine pesticides, which were studied with three different spray solvents: acetone and toluene in positive ion mode, and anisole in negative ion mode. The analytes showed [M + H]⁺, M^+?, and [M–H]^? ions as well as fragmentation and substitution products. Detection limits for the studied compounds ranged from 30 pg to 1 ng (from 0.14 to 5.6 pmol). To demonstrate the feasibility of the use of DAPPI‐MS two authentic samples – a circuit board and orange peel – and a spiked soil sample were analyzed. Tetrabromobisphenol A, imazalil, and PAHs were observed from the three above‐mentioned samples, respectively. The method is best suited for rapid screening analysis of environmental or food samples. Copyright © 2010 John Wiley & Sons, Ltd.     

Ultra‐fast adenosine 5′‐triphosphate,adenosine 5′‐diphosphate and adenosine 5′‐monophosphate detection by pressure‐assisted capillary electrophoresis UV detection

Herein, we report a new CE method to measure adenine nucleotides adenosine 5′‐triphosphate, adenosine 5′‐diphosphate, and adenosine 5′‐monophosphate in red blood cells. For this purpose, 20 mmol/L sodium acetate buffer at pH 3.80 was used as running electrolyte, and the separation was performed by the simultaneous application of a CE voltage of 25 kV and an overimposed pressure of 0.2 psi from inlet to outlet. A rapid separation of these analytes in less than 1.5 min was obtained with a good reproducibility for intra‐ and inter‐assay (CV<4 and 8%, respectively) and an excellent analytical recovery (from 98.3 to 99%). The applicability of our method was proved by measuring adenine nucleotides in red blood cells.     

Oxygen adsorption on β-quartz model surfaces: some insights from density functional theory calculations and semiclassical time-dependent dynamics

The O/β-quartz interaction is described by combining our time-dependent semiclassical approach to atom-molecule/surface scattering with first-principles electronic structure calculations at the DFT (PBE0) level of accuracy. In particular, the O, O(2) interaction potentials with an on-top Si atom and its nearest O atom both localized over three different silica clusters have been calculated as a function of the oxygen-silica approaching distance. The calculated DFT potential energy surface has been used in semiclassical trajectory calculations to investigate the sticking and inelastic reflection of oxygen atoms from a model β-quartz surface. The collisional mechanism, including the role played by the phonon dynamics, is brought to light and accurate sticking probabilities are calculated at five impact energies in the range [0.05-0.8] eV and T(S) = 1000 K. The different catalytic response of β-quartz and β-cristobobalite to the atomic oxygen flux is also discussed and highlighted.     

Electron-attachment resonances of glycine zwitterions from quantum scattering calculations: modeling macrosolvation effects

A computational study of the quantum dynamics for low-energy electrons scattered by the isolated zwitterionic species of the glycine molecule is carried out using a model interaction potential described in the main text. The macroscopic effects of water solvation on the target molecule in the electron scattering problem are described through a continuum polarizable model (CPCM) which modifies the target molecular structure. In such a way, realistic molecular orbitals depicting the glycine zwitterion in solution are used to model the electron-molecule interaction. The results of the calculations indicate the presence of five different transient negative ions (TNIs) formed at energies from the threshold and up to about 6 eV. Although no nuclear motion was explicitly considered in the ensuing decay processes, the analysis of the nodal structures and density distributions for the resonant excess electron wavefunctions over the molecular space suggests possible anionic fragmentations that produce (Gly-H)-, H-, -CO2-, and -NH3. The likely consequences of such releases into the medium are briefly discussed.     

Differentiation of human bone marrow stem cells into cells with a neural phenotype: diverse effects of two specific treatments

Background  

It has recently been demonstrated that the fate of adult cells is not restricted to their tissues of origin. In particular, it has been shown that bone marrow stem cells can give rise to cells of different tissues, including neural cells, hepatocytes and myocytes, expanding their differentiation potential.