A Deep Eutectic Solvent‐based Amperometric Sensor for the Detection of Low Oxygen Contents in Gaseous Atmospheres

The possibility of adopting deep eutectic solvents (DESs) instead of room temperature ionic liquids (RTILs) in membrane‐free electrochemical gas probes was estimated by first evaluating the performance of ethaline as electrochemical medium. This very easily prepared DES was chosen as prototype since it displays high conductivity and fairly modest viscosity, comparable with those of RTILs usually adopted in electrochemical measurements. Its electrostability window at Au, Pt and GC electrodes was first detected, together with diffusion coefficients displayed in this medium by ferrocene in the range 2.0–26.5 °C, it being adopted as prototype analyte in view of its well known electrochemical behavior and high enough solubility in ethaline. These diffusion coefficients were then used to infer viscosity values of ethaline at all temperatures considered, by exploiting the Stokes‐Einstein equation. Even though ferrocene diffusion coefficients turned out to be remarkably lower than those displayed in usual aprotic solvents, they were fairly higher than those usually found in electrochemical measurements conducted in RTILs, thus pointing out that the use of DESs as solvents adhering to electrode surfaces for assembling electroanalytical gas sensors could be advantageous. On these bases, a conveniently assembled DES‐based probe was tested for the electrochemical detection of low oxygen contents in cooled atmospheres. The quite satisfactory results found indicated that the drawback affecting DESs, consisting in the low values of diffusion coefficients displayed by dissolved analytes, can be overcome by using thin enough DES layers and resorting to a high sensitive detection approach such as amperometry under flow conditions. In fact, good sensitivities were found at all temperatures considered (2.0–26.5 °C), accompanied by a low detection limit (ca. 0.1 % v/v).     

Oxygenation of alkane C-H bonds with methyl(trifluoromethyl)dioxirane: effect of the substituents and the solvent on the reaction rate

[Chemical reaction: See text] The mechanism of the oxygenation of alkane C-H bonds with methyl(trifluoromethyl)dioxirane (1a) is studied through the effect of the substituent and solvent on the rate of oxygenation of 2-substituted adamantanes (2). The results suggest a remarkable electron deficiency at the reacting carbon atom in the transition state leading to the regular oxygenation products. The linearity of the Hammett plot reveals that the reaction mechanism does not change within a range of 0.15-0.67 units of sigma(I). A change in the solvent does not affect the distribution of the products, indicating a through-bond transmission of the substituent effect as the origin of the deactivation of the substrate.     

Hydrogels for potential colon drug release by thiol-ene conjugate addition of a new inulin derivative

Inulin was chosen as a starting polymer for biocompatible, pH-sensitive and biodegradable hydrogels. Three INUDVSA-TT hydrogels were obtained by crosslinking inulin derivatives with trimethylolpropane tris(3-mercaptopropionate) under varying conditions. The resulting hydrogels were cell compatible, as demonstrated by MTS and trypan blue exclusion assays acting on Caco-2 cells, and were biodegraded by inulinase and esterase, thus suggesting their use as colonic drug delivery systems. 2-Methoxyestradiol, an anti-cancer drug, was soaked in INUDVSA-TT hydrogels and its in vitro release and apoptotic effect on Caco-2 cells were evaluated.     

Development of a new ultra-high-performance liquid chromatography–tandem mass spectrometry method for the determination of digoxin and digitoxin in plasma: Comparison with a clinical immunoassay

Cardiac glycosides digoxin and digitoxin are used in therapy for the treatment of congestive heart failure. Moreover, these compounds can be responsible for intoxication cases caused by fortuitous ingestion of leaves of Digitalis. Due to the narrow therapeutic range of these drugs, therapeutic drug monitoring is recommended in the clinical practice. In this context, immunoassays-based methods are generally employed but digoxin- and digitoxin-like compounds can interfere with the analysis. The aim of this study was to develop and validate an original UPLC–MS/MS method for the determination of digoxin and digitoxin in plasma. The method shows adequate sensitivity and selectivity with acceptable matrix effects and very good linearity, accuracy, precision, and recovery. A simple liquid–liquid extraction procedure was used for sample clean-up. The method was applied for the analysis of n = 220 plasma samples collected in two different clinical chemistry laboratories and previously tested by the same immunoassay. The statistical comparison showed a relevant negative bias of the UPLC–MS/MS method versus the immunoassay. These results are consistent with an immunoassay overestimation of digoxin plasmatic levels due to cross-reaction events with endogenous digoxin-like substances.     

A fast and effective routine method based on HS-SPME–GC–MS/MS for the analysis of organotin compounds in biota samples

This work validated an automated, fast, and low solvent- consuming methodology suited for routine analysis of tributyltin (TBT) and degradation products (dibutyltin, DBT; monobutyltin, MBT) in biota samples. The method was based on the headspace solid-phase microextraction methodology (HS-SPME), coupled with gas chromatographic separation and tandem mass-spectrometry (GC–MS/MS). The effectiveness of the matrix-matched signal ratio external calibration was tested for quantification purposes. The exclusion of matrix influences in the calibration curves proved the suitability of this versatile quantification method. The method detection limits obtained were of 3 ng Sn g⁻¹ dw for all the analytes. The analysis of references materials showed satisfying accuracy under optimum calibration conditions (% recovery between 87–111%; |Z-scores|<2). The repeatability RSD% and intra-laboratory reproducibility RSD% were lower than 9.6% and 12.6%, respectively. The work proved the remarkable analytical performances of the method and its high potential for routine application in monitoring organotin compounds (OTC).     

Cauchy problem for some non-Kovalewskian equations

Some evolution equations with constant leading coefficients and real characteristic roots are considered. The wellposedness of Cauchy problem is proved inH ^∞ and in Gevrey classes, if an assumption is made on the lower order terms. Finally the results are generalized to nonlinear equations.

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Sunto Si considerano equazioni differenziali di evoluzione con coefficienti costanti nella parte principale e radici caratteristiche reali. Si dimostra la buona positura del problema di Cauchy inH ^∞ e nelle classi di Gevrey, sotto un’ipotesi sui termini di ordine inferiore. Infine, i risultati vengono estesi alle equazioni non lineari.

     

End‐group functionalization and postpolymerization modification of helical poly(isocyanide)s

This contribution presents the synthesis of helical alkyne‐terminated polymers using a functionalized Nickel complex to initiate the polymerization of menthylphenyl isocyanides. The resulting polymers display low dispersities and controlled molecular weights. Copper‐catalyzed azide/alkyne cycloadditions (CuAAC) are performed to attach various azide‐containing compounds to the polymer termini. After azido‐phosphonate moiety attachment the polymer displays a signal at 25.4 ppm in the ³¹P NMR spectrum demonstrating successful end‐group functionalization. End‐group functionalization of a fluorescent dye allows to determine the functionalization yield as 89% (±8). Successful ligation of an azide‐functionalized peptide sequence (M_KLA = 1547 g/mol) increases the M_n from 5100 for the parent polymer to 6700 for the bioconjugate as visualized by GPC chromatography. Analysis by CD spectroscopy confirms that the helical conformation of the poly(isocyanide) block in the peptide–polymer conjugate is maintained after postpolymerization modification. These results demonstrate an easy, generalizable, and versatile strategy toward mono‐telechelic helical polymers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2766–2773     

Prince Cangrande’s Collagen: Study of Protein Modification on the Mummy of the Lord of Verona,Italy (1291–1329 AD)

The natural mummy of prince Cangrande, Lord of Verona, Italy (1291–1329 AD) was studied. Two samples were taken: rib bone and muscle. These samples were cleaved with trypsin and analysed by liquid chromatographic methods coupled to mass spectrometry (Q-TOF, ion-trap). Special attention was devoted to nonenzymatic protein modification––the deamidation of asparagine and glutamine. A huge amount of collagen was determined in the tissues of the mummy (covering over 80 % of the sequence)––collagen type I was identified in the rib bone and collagen types I and III in the muscle. A high overall percentage of asparaginyl and glutaminyl residues were deamidated (up to 92 %). In agreement with the literature we can suppose that the deamidation of really old samples (at least 100-years-old) is mainly dependent on the burial conditions and/or thermal age and cannot serve as a precise “molecular clock”.