Proteome investigation of the non-model plant pomegranate (Punica granatum L.)

A gel-free, shotgun proteomics approach was used to characterize pomegranate aril proteome by nanoliquid chromatography–high-resolution tandem mass spectrometry. To identify both high-abundance and low-abundance proteins, we applied two distinct sample preparation protocols, i.e., a classical one widely applied in literature and a second one able to reduce the dynamic range of protein concentration of the sample, based on combinatorial hexapeptide ligand library technology. However, the proteins identified with the latter protocol were only a small minority. Because pomegranate is a non-model plant species, i.e., information of its genome sequence are lacking, only a few protein sequences are included in the most widely known protein sequence databases. To improve both the number of identified proteins and data reliability, identification was performed integrating the results obtained with three distinct plant protein databases, since the majority of proteins could only be attributed by homology with other plant species. Nevertheless, many proteins had assigned only one unique peptide, because of the phylogenetic distance of pomegranate from the main model plants. After manual revision of the identified proteins to eliminate the redundant or ambiguous identifications, a list of 1,488 proteins was obtained, only six of which belonging to pomegranate species. To the author's best knowledge, this is the first work aimed at the proteomic characterization of Punica granatum.     

Multisyringe flow injection analysis hyphenated with liquid core waveguides for the development of cleaner spectroscopic analytical methods: improved determination of chloride in waters

In this work, the hyphenation of the multisyringe flow injection analysis technique with a 100-cm-long pathlength liquid core waveguide has been accomplished. The Cl⁻/Hg(SCN)₂/Fe³⁺ reaction system for the spectrophotometric determination of chloride (Cl⁻) in waters was used as chemical model. As a result, this classic analytical methodology has been improved, minimizing dramatically the consumption of reagents, in particular, that of the highly biotoxic chemical Hg(SCN)₂. The proposed method features a linear dynamic range composed of two steps between (1) 0.2–2 and (2) 2–8 mg Cl⁻ L⁻¹, thus extended applicability due to on-line sample dilution (up to 400 mg Cl⁻ L⁻¹). It also presents improved limits of detection and quantification of 0.06 and 0.20 mg Cl⁻ L⁻¹, respectively. The coefficient of variation and the injection throughput were 1.3% (n = 10, 2 mg Cl⁻ L⁻¹) and 21 h⁻¹. Furthermore, a very low consumption of reagents per Cl⁻ determination of 0.2 μg Hg(II) and 28 μg Fe³⁺ has been achieved. The method was successfully applied to the determination of Cl⁻ in different types of water samples. Finally, the proposed system is critically compared from a green analytical chemistry point of view against other flow systems for the same purpose.     

Neutron diffraction study of the (1-x)αFe2O3xAl2O3 system

The magnetic structure of the (1-x) α Fe₂O₃xAl₂O₃ system with x= 0–0.1 has been investigated on polycrystalline samples by neutron diffraction method. The Morin transition temperature and the Néel temperature are observed to decrease on increasing x. The angle by which the magnetic moments turn out of the basal plane in the Morin transition also decreases with increasing x. The Morin transition does not occur above x = 0.09.     

Highly enantioselective Rh-catalyzed hydrogenation based on phosphine-phosphite ligands derived from carbohydrates.

A new class of efficient catalysts was developed for the asymmetric hydrogenation of alpha,beta-unsaturated carboxylic acid derivatives by synthesizing a series of novel phosphine-phosphite ligands (4a-d) derived from readily available D-(+)-xylose. Excellent enantioselectivities (> 99%) were achieved under very mild reaction conditions (1 bar H(2) and 20 degrees C). Varying the biphenyl substituents in the phosphite moiety greatly affected the enantioselectivity in the hydrogenation reactions. The results also indicate that the sense of enantioselectivity is mainly controlled by the configuration of the phosphite moiety. (31)P[(1)H] NMR and kinetic studies on intermediates of the catalytic cycle show that the [Rh(P(1)-P(2))(enamide)]BF(4) species is the resting state and that the rate dependence is first order in rhodium and hydrogen pressure and zero order in enamide concentration.     

Optimal acoustic error sensing for global active control in a harmonically excited enclosure

The performance of an active control system in global control of enclosed sound fields depends largely on the localization of the error sensors, among other factors. In this paper a modified cost function is proposed in order to guarantee the maximum attenuation that can be produced by a set of secondary sources in the case of an harmonically excited sound field. The cost function is modified in order to drive the error signal to the value corresponding to the optimally attenuated sound field, instead of minimizing the squared pressure. To evaluate the performance of the proposed control system, its robustness against unstructured error is also investigated using a set of intensive calculations. Following this approach, the sensors can be located anywhere and the optimal attenuation is reached using an equal number of error sensors and secondary sources. The results also suggest that the greater the number of error sensors than secondary sources the more robust the control system is. This behavior holds for both the usual strategy of minimizing the squared pressure and the approach presented in this paper. However, the latter strategy is more robust than the traditional approach of minimizing the squared pressures and its robustness does not depend on the location of the error sensors. Thus, as a main conclusion, the use of the new cost function leads to a guaranteed efficiency and a more robust control system and gives absolute freedom in selecting the location of the error sensors.     

In‐syringe‐assisted dispersive liquid–liquid microextraction coupled to gas chromatography with mass spectrometry for the determination of six phthalates in water samples

A fully automated method for the determination of six phthalates in environmental water samples is described. It is based in the novel sample preparation concept of in‐syringe dispersive liquid–liquid microextraction, coupled as a front end to GC–MS, enabling the integration of the extraction steps and sample injection in an instrumental setup that is easy to operate. Dispersion was achieved by aspiration of the organic (extractant and disperser) and the aqueous phase into the syringe very rapidly. The denser‐than‐water organic droplets released in the extraction step, were accumulated at the head of the syringe, where the sedimented fraction was transferred to a rotary micro‐volume injection valve where finally was introduced by an air stream into the injector of the GC through a stainless‐steel tubing used as interface. Factors affecting the microextraction efficiency were optimized using multivariate optimization. Figures of merit of the proposed method were evaluated under optimal conditions, achieving a detection limit in the range of 0.03–0.10 μg/L, while the RSD% value was below 5% (n = 5). A good linearity (0.9956 ≥ r² ≥ 0.9844) and a broad linear working range (0.5–120 μg/L) were obtained. The method exhibited enrichment factors and recoveries, ranging from 14.11–16.39 and 88–102%, respectively.     

On the Reaction Mechanism of the Rhodium‐Catalyzed Arylation of Fullerene (C60) with Organoboron Compounds in the Presence of Water

Density functional theory (DFT) calculations were carried out to study the reaction mechanism of the Suzuki–Miyaura rhodium‐catalyzed hydroarylation of fullerene (C₆₀) by phenylboronic acid in the presence of water. As found experimentally, our results confirm that addition of the phenyl group and the hydrogen atom in C₆₀ occurs at the [6,6] bond. The rate‐determining step corresponds to the simultaneous transfer of a hydrogen atom from a water molecule to C₆₀ and the recovery of the active species. The use of 2‐phenyl‐1,3,2‐dioxaborinane and the 4,4,5,5‐tetramethyl‐2‐phenyl‐1,3,2,‐dioxaborolane instead of phenylboronic acid as organoborate agents does not lead to great modifications of the energy profile. The possible higher steric hindrance of 4,4,5,5‐tetramethyl‐2‐phenyl‐1,3,2,‐dioxaborolane should not inhibit its use in the hydroarylation of C₆₀. Overall, we show how organoboron species arylate C₆₀ in rhodium‐based catalysis assisted by water as a source of protons.     

Design,Synthesis and Characterization of a Visible-Light-Sensitive Molecular Switch and Its PEGylation Towards a Self-Assembling Molecule

HBDI-like chromophores represent a novel set of biomimetic switches mimicking the fluorophore of the green fluorescent protein that are currently studied with the hope to expand the molecular switch/motor toolbox. However, until now members capable of absorbing visible light in their neutral (i. e. non-anionic) form have not been reported. In this contribution we report the preparation of an HBDI-like chromophore based on a 3-phenylbenzofulvene scaffold capable of absorbing blue light and photoisomerizing on the picosecond timescale. More specifically, we show that double-bond photoisomerization occurs in both the E-to-Z and Z-to-E directions and that these can be controlled by irradiating with blue and UV light, respectively. Finally, as a preliminary applicative result, we report the incorporation of the chromophore in an amphiphilic molecule and demonstrate the formation of a visible-light-sensitive nanoaggregated state in water.     

Effect of temperature on pH measurements and acid-base equilibria in methanol-water mixtures

The knowledge of the acid-base equilibria in water-solvent mixtures of both common buffers and analytes is necessary in order to predict their retention as function of pH, solvent composition and temperature. This paper describes the effect of temperature on acid-base equilibria in methanol-water solvent mixtures commonly used as HPLC mobile phases. We measured the delta-correction parameter (delta = sw pH - ss pH = Ej - log sw(gamma)oh) between two pH scales: pH measured in the solvent concerned and referred to the same standard state, ss pH, and the pH measured in that solvent mixture but referred to water as standard state, sw pH, for several methanol compositions in the temperature range of 20-50 degrees C. These determinations suggest that the delta-term depends only on composition of the mixture and on temperature. In water-rich mixtures, for which methanol is below 40% (w/w), delta-term seems to be independent of temperature, within the experimental uncertainties, whereas for methanol content larger than 50% (w/w) the delta-correction decreases as temperature increases. We have attributed this decrease to a large increase in the medium effect when mixtures have more than 50% methanol. The pKa of five weak electrolytes of different chemical nature in 50% methanol-water at 20-50 degrees C are presented: the effect of temperature on pKa was large for amines, pyridine and phenol, but almost no dependence was found for benzoic acid. This indicates that buffers can play a critical role in affecting retention and selectivity in HPLC at temperatures far from 25 degrees C, particularlyfor co-eluted solutes.