Novel coating for solid-phase microextraction: Electropolymerization of a molecular receptor functionalized with 2,2′-bithiophene for the determination of environmental pollutants at trace levels

A novel solid-phase microextraction coating based on the electropolymerization of a molecular receptor properly functionalized with 2,2′-bithiophene was developed for the determination of environmental pollutants in air and water samples. The 2,2′-bithiophene-based film was electrochemically deposed on the surface of a gold wire using cyclic voltammetry. The fibres showed a porous structure with an average thickness of 12 ± 3 μm (n = 5): a good intra-batch and inter-batch repeatability with RSD lower than 14% was also observed. The selective interactions via hydrogen bonding with organic molecules containing electronegative atoms was proved: LOD values in the low ng/l range allowed the determination of vinyl chloride and chlorobenzenes at trace levels in environmental matrices.     

Bacteria‐Based Production of Thiol‐Clickable,Genetically Encoded Lipid Nanovesicles

Despite growing research efforts on the preparation of (bio)functional liposomes, synthetic capsules cannot reach the densities of protein loading and the control over peptide display that is achieved by natural vesicles. Herein, a microbial platform for high‐yield production of lipidic nanovesicles with clickable thiol moieties in their outer corona is reported. These nanovesicles show low size dispersity, are decorated with a dense, perfectly oriented, and customizable corona of transmembrane polypeptides. Furthermore, this approach enables encapsulation of soluble proteins into the nanovesicles. Due to the mild preparation and loading conditions (absence of organic solvents, pH gradients, or detergents) and their straightforward surface functionalization, which takes advantage of the diversity of commercially available maleimide derivatives, bacteria‐based proteoliposomes are an attractive eco‐friendly alternative that can outperform currently used liposomes.     

Last ten years (2008–2018) of chiral ligand‐exchange chromatography in HPLC: An updated review

Chiral ligand‐exchange chromatography is one of the elective strategies for the direct enantioresolution of small chelating compounds: amino acids, diamines, amino alcohols, diols, small peptides, etc. Unlike other methods, the interaction between chiral selector and analyte enantiomers is mediated by a cation, thus producing diastereomeric ternary complexes. Two main approaches are conventionally applied in chiral ligand‐exchange chromatography. The first relies upon chiral stationary phases where the chiral selector is either covalently immobilized or physically adsorbed onto suitable packing materials (coated phases). In the second approach, chiral molecules are added to the eluent, thus generating chiral eluent systems. Among the advantages of chiral ligand‐exchange chromatography, the generation of UV/vis‐active metal complexes, and the use of commercially available or easy‐to‐synthesize chiral selectors, in combination to rather inexpensive achiral columns for coated phases and chiral eluents, are noteworthy. Besides amino acids and amino alcohols, other species have proven suitable for chiral ligand‐exchange chromatography applications. Recently, the use of either chiral ionic liquids or micellar liquid chromatography systems as well as the successful off‐column formation of diastereomeric complexes have expanded the selectivity profiles and application fields. All of these issues are touched in the review, shedding light to the contributions appeared in the last decade.     

Determination of several synthetic cathinones and an amphetamine‐like compound in urine by gas chromatography with mass spectrometry. Method validation and application to real cases

Most routine practices for drugs‐of‐abuse testing do not include screening procedures for new psychoactive substances, despite their increasing diffusion, preventing clear knowledge of the real consumption of these drugs in the populations. To make up for this shortcoming, a gas chromatography with mass spectrometry method was developed for the simultaneous determination of 18 synthetic cathinones and one amphetamine‐like compound in human urine. The sample preparation was based on liquid–liquid extraction under alkaline condition followed by derivatization with trifluoroacetic anhydride. The separation of the 19 analytes was achieved in less than 10 min. The whole methodology was validated according to national and international guidelines. Selectivity, linearity range, limit of detection and limit of quantitation, precision and accuracy were evaluated. For all the analytes, the calibration curve was linear in the 100–1000 ng/mL concentration range. The limits of detection ranged from 10 to 30 ng/mL and limits of quantitation from 30 to 100 ng/mL. Precisions were in the ranges 0.1–10.4%, and 1.0–12.1% for low (100 ng/mL) and high (1000 ng/mL) concentration, respectively. The accuracy, expressed as bias% was within ±20% for all the analytes. The present method was successfully applied to urine samples originating from autopsies, drug abuse/withdrawal controls, clinical investigations, roadside controls, driving re‐licensing, and workplace testing.     

Bacteria‐Based Production of Thiol‐Clickable,Genetically Encoded Lipid Nanovesicles

Despite growing research efforts on the preparation of (bio)functional liposomes, synthetic capsules cannot reach the densities of protein loading and the control over peptide display that is achieved by natural vesicles. Herein, a microbial platform for high‐yield production of lipidic nanovesicles with clickable thiol moieties in their outer corona is reported. These nanovesicles show low size dispersity, are decorated with a dense, perfectly oriented, and customizable corona of transmembrane polypeptides. Furthermore, this approach enables encapsulation of soluble proteins into the nanovesicles. Due to the mild preparation and loading conditions (absence of organic solvents, pH gradients, or detergents) and their straightforward surface functionalization, which takes advantage of the diversity of commercially available maleimide derivatives, bacteria‐based proteoliposomes are an attractive eco‐friendly alternative that can outperform currently used liposomes.     

8-hydroxyquinoline derivatives as fluorescent sensors for magnesium in living cells

Despite the key role of magnesium in many fundamental biological processes, knowledge about its intracellular regulation is still scarce, due to the lack of appropriate detection methods. Here, we report the spectroscopic and photochemical characterization of two diaza-18-crown-6 hydroxyquinoline derivatives (DCHQ) and we propose their application in total Mg(2+) assessment and in confocal imaging as effective Mg(2+) indicators. DCHQ derivatives 1 and 2 bind Mg(2+) with much higher affinity than other available probes (K(d) = 44 and 73 microM, respectively) and show a strong fluorescence increase upon binding. Remarkably, fluorescence output is not significantly affected by other divalent cations, most importantly Ca(2+), or by pH changes within the physiological range. Evidence is provided on the use of fluorometric data to derive total cellular Mg(2+) content, which is consistent with atomic absorption data. Furthermore, we show that DCHQ compounds can be effectively employed to map intracellular ion distribution and movements in live cells by confocal microscopy. A clear staining pattern consistent with known affinities of Mg(2+) for biological ligands is shown; moreover, changes in the fluorescence signal could be tracked following stimuli known to modify intracellular Mg(2+) concentration. These findings suggest that DCHQ derivatives may serve as new tools for the study of Mg(2+) regulation, allowing sensitive and straightforward detection of both static and dynamic signals.     

Chemoselective esterification of phenolic acids and alcohols

[formula: see text] The Mitsunobu reaction can distinguish between alcohol and phenol hydroxyls in esterification reactions, providing an expeditious and broadly applicable entry into various phenolics and polyphenolics of biomedical and nutritional relevance.     

Structure of Escherichia coli dUTPase in Solution: A Small Angle Neutron Scattering Study

The present study investigates shape properties of the enzyme dUTPase from Escherichia coli in the solution phase. In this work small angle neutron scattering (SANS) findings on dUTPase/D₂O solutions for temperature values of T = 8 °C and T = 37 °C are presented. The analysis of SANS data, carried out by using a prolate ellipsoid core/shell model fitting and the well‐known Guinier and Zimm analysis procedures allows the characterization of the shape of the protein in solution. By means of the comparison with experimental and theoretical data existing in literature on dUTPase in the crystalline state, we find that the protein in solution maintains its dimensions before the denaturation process. Furthermore, by analyzing the SANS spectra of dUTPase/D₂O/trehalose solutions, we emphasize the bioprotective effects of trehalose on the protein.

Structure of dUTPase.     

Formation of basic compounds during the indole cyclization of ketone phenylhydrazones

On the basis of previous occasional findings, the Fischer indole cyclization of ten ketone phenylhydrazones containing moieties of increasing bulkiness was investigated in order to isolate eventual side products. In the cases of the three 2-, 3- and 4-acetylpyridine phenylhydrazones the corresponding 2-pyridylindoles were the sole compounds so far isolated. In all the remaining cases, beside the indoles a mixture of basic compounds was obtained. In all cases aniline and a 2-substituted (2-methyl or 2-phenyl)benzimidazole were formed, the last resulting through an apparent ortho-semidinic rearrangements of phenylhydrazones. Starting from methyl isopropyl ketone phenylhydrazone a compound of formula C₁₁H₁₅NO was also isolated, to which the structure of 3-(4-aminophenyl)-3-methylbutanone was assigned on the basis of ir, nmr spectra and of the chemical reactivity. The formation of this compound seems related to a para-benzidine-like rearrangement of phenyl hydrazone.