Synthesis,physicochemical characterization,and TD–DFT calculations of monothiocarbohydrazone derivatives

Structural Chemistry - Derivatives of thiocarbohydrazone studied so far have shown great biological activity such as antioxidant, antimicrobial, and anticancer. Most of these compounds are...     

Hydrolysis of Fe(III) in the presence of mixed anions and promoters

Journal of Radioanalytical and Nuclear Chemistry - Forced hydrolyses in the precipitation systems (a) Fe(NO3)3/Fe2(SO4)3 and FeCl3/Fe2(SO4)3 and (b) FeCl3/N-guanylurea sulphate were investigated...     

Aroma Profile and Chemical Composition of Reverse Osmosis and Nanofiltration Concentrates of Red Wine Cabernet Sauvignon

Wine aroma represents one of the main properties that determines the consumer acceptance of the wine. It is different for each wine variety and depends on a large number of various chemical compounds. The aim of this study was to prepare red wine concentrates with enriched aroma compounds and chemical composition. For that purpose, Cabernet Sauvignon red wine variety was concentrated by reverse osmosis (RO) and nanofiltration (NF) processes under different operating conditions. Different pressures (2.5, 3.5, 4.5 and 5.5 MPa) and temperature regimes (with and without cooling) were applied on Alfa Laval LabUnit M20 equipped with six composite polyamide RO98pHt M20 or NF M20 membranes. Higher pressure increased the retention of sugars, SO₂, total and volatile acids and ethanol, but the temperature increment had opposite effect. Both membranes were permeable for water, ethanol, acetic acid, 4-ethylphenol and 4-ethylguaiacol and their concentration decreased after wine filtration. RO98pHt membranes retained higher concentrations of total aroma compounds than NF membranes, but both processes, reverse osmosis and nanofiltration, resulted in retentates with different aroma profiles comparing to the initial wine. The retention of individual compounds depended on several factors (chemical structure, stability, polarity, applied processing parameters, etc.).     

BODIPY Dyes Bearing Multibranched Fluorinated Chains: Synthesis,Structural, and Spectroscopic Studies

A small series of boron-dipyrromethene (BODIPY) dyes, characterized by the presence of multibranched fluorinated residues, were designed and synthesized. The dyes differ in both the position (para-perfluoroalkoxy-substituted phenyl ring or boron functionalization) and number of magnetically equivalent fluorine atoms (27 or 54 fluorine atoms per molecule). Photophysical and crystallographic characterization of the synthesized BODIPYs was carried out to evaluate the effect of the presence of highly fluorinated moieties on the optical and morphological properties of such compounds.     

Ultrasensitive and Selective Copper(II) Detection: Introducing a Bioinspired and Robust Sensor

A nanopore-based Cu^II-sensing system is reported that allows for an ultrasensitive and selective detection of Cu^II with the possibility for a broad range of applications, for example in medical diagnostics. A fluorescent ATCUN-like peptide 5/6-FAM-Dap-β-Ala-His is employed to selectively bind Cu^II ions in the presence of Ni^II and Zn^II and was crafted into ion track-etched nanopores. Upon Cu^II binding the fluorescence of the peptide sensor is quenched, permitting the detection of Cu^II in solution. The ion transport characteristics of peptide-modified nanopore are shown to be extremely sensitive and selective towards Cu^II allowing to sense femtomolar Cu^II concentrations in human urine mimics. Washing with EDTA fully restores the Cu^II-binding properties of the sensor, enabling multiple repetitive measurements. The robustness of the system clearly has the potential to be further developed into an easy-to-use, lab-on-chip Cu^II-sensing device, which will be of great importance for bedside diagnosis and monitor of Cu^II levels in patients with copper-dysfunctional homeostasis.     

Gas-Phase Transformation of Fluorinated Benzoporphyrins to Porphyrin-Embedded Conical Nanocarbons

Geodesic nitrogen-containing graphene fragments are interesting candidates for various material applications, but the available synthetic protocols, which need to overcome intrinsic strain energy during the formation of the bowl-shaped skeletons, are often incompatible with heteroatom-embedded structures. Through this mass spectrometry-based gas-phase study, we show by means of collision-induced dissociation experiments and supported by density functional theory calculations, the first evidence for the formation of a porphyrin-embedded conical nanocarbon. The influences of metalation and functionalization of the used tetrabenzoporphyrins have been investigated, which revealed different cyclization efficiencies, different ionization possibilities, and a variation of the dissociation pathway. Our results suggest a stepwise process for HF elimination from the fjord region, which supports a selective pathway towards bent nitrogen-containing graphene fragments.     

Insights into mechanical properties of certain bio-inspired branched structures

This study is concerned with the motion and displacement of points on branches of a bio-inspired sympodial tree-like structure of a different hierarchy. First, displacements of points of a sympodial-like tree are recorded in pull-and-release experiments to get a qualitative insight into their behaviour. Then, a sympodial-type structure is analyzed, starting from its trunk, along a first-order branch and along an external and internal second-order branch. Given the fact that each point on branches performs in-plane vibration, their corresponding mechanical model consists of two orthogonal springs of unknown directions and unknown stiffness coefficients. Their directions actually correspond to the principal axes, which are obtained for the first time in the analytical form in terms of system’s geometrical and material parameters. The additional novelty lies in demonstrating how the position of their principal axes changes along each branch. Extreme displacements along principal axes are obtained as well, defining the ellipse of displacement for each point on branches of different order and position. The advantages of branched structures with respect to T-shaped structures that are commonly used in engineering are discussed and emphasized.     

A Highly Water- and Air-Stable Iron-Containing MRI Contrast Agent Sensor for H2O2

A highly water- and air-stable Fe(II) complex with the quinol-containing macrocyclic ligand H₄qp4 reacts with H₂O₂ to yield Fe(III) complexes with less highly chelating forms of the ligand that have either one or two para-quinones. The reaction increases the T₁-weighted relaxivity over four-fold, enabling the complex to detect H₂O₂ using clinical MRI technology. The iron-containing sensor differs from its recently characterized manganese analog, which also detects H₂O₂, in that it is the oxidation of the metal center, rather than the ligand, that primarily enhances the relaxivity.     

Measurement of Stevioside by Square‐Wave Polarography

Steviol glycosides are electroactive compounds and can be detected by mercury electrode. The maxima of square‐wave polarograms of steviol and stevioside appear at ?1.3 V vs. Ag/AgCl in 1 M NaCl at approximately pH 11. The responses are quasireversible and probably caused by electroreduction of carboxyl, or ester groups, respectively. The net peak current is linearly proportional to steviol concentration between 1×10^?6 mol/L and 3.5×10^?5 mol/L. This calibration plot can be used for the determination of the concentration of stevioside in extracts of stevia (Stevia rebaudiana Bertoni) leaves. The proposed method is applicable for routine analysis of stevioside in commercial products.     

Structural and physical–chemical evaluation of Bradykinin Potentiating Peptide and its high soluble supramolecular complex

The supramolecular interactions between a Bradykinin Potentiating Peptide (BPP10c) and β-cyclodextrin (βCD) have been investigated by using several techniques. These new properties acquired by the inclusion phenomena are important in developing a strategy for pharmaceutical formulation. The BPP10c structural elucidation and its inclusion complex formed have been investigated using Nuclear Magnetic Resonance techniques. The peptide secondary structure was investigated using infrared spectroscopy in solution, Circular Dichroism and NMR. In addition, the thermodynamic parameters of the inclusion process were also evaluated using Isothermal Titration Calorimetry. The results obtained by these physical–chemical techniques suggested a 1:1 complex formed by interaction between the Tryptophan amino acid residue and the βCD cavity. The peptide secondary structure was not substantially modified for the inclusion process. In addition, the inclusion process proved to be spontaneous (ΔGº = ?2.53 kcal mol^?1), with an enthalpy reduction (ΔHº = ?3.72 kcal mol^?1) and a favored entropic variation (TΔSº = ?1.19 kcal mol^?1).