Determining accurate molecular sizes in solution through NMR diffusion spectroscopy

This tutorial review deals with the methodological procedures that can be used to obtain accurate molecular sizes in solution from diffusion NMR spectroscopy. The critical aspects associated with the estimation of the size of molecules from the measured translational self-diffusion coefficient, using the Stokes-Einstein equation, are highlighted and discussed. From a theoretical point of view, it is shown how to take into account the size of the solute with respect to that of the solvent and its non-spherical shape using the appropriate correction factors in the frictional coefficient. From a practical point of view, the advantages of introducing an internal standard in the sample are presented. Initially, non-aggregating systems are considered in an attempt to clarify what hydrodynamic dimensions mean. Successively, aggregating systems are addressed showing how it is possible to understand the aggregation level and derive the thermodynamic parameters for some illustrative aggregation processes.     

Amylose-wrapped luminescent conjugated polymers

Highly luminescent inclusion complexes consisting of poly(para-phenylene) (PPP) or poly(4,4'-diphenylene-vinylene) (PDV) in the helical cavity of amylose have been synthesised, structurally characterised by nuclear Overhauser spectroscopy and used to fabricate electroluminescent light-emitting diodes.     

Identification and determination of mainstream and sidestream smoke components in different brands and types of cigarettes by means of solid-phase microextraction-gas chromatography-mass spectrometry

The qualitative and quantitative determination of components of mainstream and sidestream smoke has been performed by solid-phase microextraction-gas chromatography-mass spectrometry. Several brands and types of cigarettes sold in Italy were considered: normal, mild, light, extra light, some with filter and some without. Extraction of the analytes was performed by means of solid-phase microextraction (SPME) and the optimisation of the extraction procedure was performed by experimental design, taking into consideration type of fiber polymer, exposure temperature and time. Sixty-seven components of mainstream and sidestream smoke were identified. The quantified compounds (by means of deuterium-labelled isotopologues) were benzene, toluene, p-xylene, m-xylene, pyridine, o-xylene, limonene, naphthalene, phenol and nicotine. Finally, a comparison between the chemical profile of smoke from the different cigarettes was made.     

Approximation by Max-Product Neural Network Operators of Kantorovich Type

In the present paper, we develop the theory of max-product neural network operators in a Kantorovich-type version, which is suitable in order to study the case of L^p-approximation for not necessarily continuous data. Moreover, also the case of the pointwise and uniform approximation of continuous functions is considered. Finally, several examples of sigmoidal functions for which the above theory can be applied are presented.     

New copper(II)/cyclic tetrapeptide system that easily oxidizes to copper(III) under atmospheric oxygen

A 13-membered ring cyclic tetrapeptide was synthesized by the solid-phase peptide synthesis method, and its copper(II) coordination properties were analyzed by optical spectroscopy, mass spectrometry, and electrochemistry. All collected data strongly support the presence, at alkaline pH, of a stable peptide/copper(III) complex that is formed in solution by atmospheric dioxygen oxidation. On the basis of previous studies on cyclic peptide/copper systems, we suggest that the copper(III) ion is at the center of the ligand's cavity being coordinated to four deprotonated amide nitrogen atoms. This donor set would greatly lower the redox potential for the CuIII/CuII couple, thus allowing easy oxidation of the coordinated copper(II) by atmospheric oxygen.     

Solution structure of some lambda(3) Iodanes: an (17)O NMR and DFT study

The structure of a series of I-O bonded bis(acyloxy)iodoarenes and benzoiodoxolones in chloroform solution has been investigated by 17O NMR spectroscopy and by density functional theory (DFT) calculations, employing the PBE0 functional together with the LANL2DZ basis set extended with polarization (d) and diffuse (p) functions. This combined approach allowed us to ascertain that, although these classes of lambda(3) iodanes maintain in chloroform solution their solid state "T-shaped" structure, a degenerate [1,3] sigmatropic shift of iodine between the two oxygens of the acyloxy groups occurs in solution. The energy barrier involved in this process differs in the two classes, thus causing significant differences in the 17O NMR spectra, at room temperature, of the two classes of compounds.     

Convenient analysis of vitamin D in cheese and other food matrixes by liquid chromatography/mass spectrometry

A convenient method is presented for determination of vitamin D in natural cheese, processed cheese, milk, cereals, noncarbonated soft drinks, and juice by liquid chromatography/ mass spectrometry (LC/MS). Samples were saponified, extracted, evaporated, redissolved in acetonitrile, and injected into an LC-atmospheric pressure chemical ionization-MS system with no preparative chromatographic steps. Vitamin D was determined by selected ion monitoring. MS response was linear for vitamin D3 and its internal standard vitamin D2, and overall average recoveries ranged from 98 to 105%. A blending experiment in which shredded vitamin D3-fortified cheddar was mixed with control nonfortified cheddar showed linearity. The limit of detection for vitamin D was 1.3 ng and the limit of quantitation was 3 ng. The method gave good accuracy and precision, with a standard deviation of 9.5 and relative standard deviation of 6.7%. Results for vitamin D3 obtained with this method for different food matrixes, at different levels, were in agreement with those obtained with the reference LC/UV method currently used by many laboratories and derived from AOAC Official Method 982.29.     

Hovenia dulcis Thumberg: Phytochemistry,Pharmacology, Toxicology and Regulatory Framework for Its Use in the European Union

Hovenia dulcis Thunberg is an herbal plant, belonging to the Rhamnaceae family, widespread in west Asia, USA, Australia and New Zealand, but still almost unknown in Western countries. H. dulcis has been described to possess several pharmacological properties, such as antidiabetic, anticancer, antioxidant, anti-inflammatory and hepatoprotective, especially in the hangover treatment, validating its use as an herbal remedy in the Chinese Traditional Medicine. These biological properties are related to a variety of secondary metabolites synthesized by the different plant parts. Root, bark and leaves are rich of dammarane-type triterpene saponins; dihydrokaempferol, quercetin, 3,3′,5′,5,7-pentahydroflavone and dihydromyricetin are flavonoids isolated from the seeds; fruits contain mainly dihydroflavonols, such as dihydromyricetin (or ampelopsin) and hovenodulinol, and flavonols such as myricetin and gallocatechin; alkaloids were found in root, barks (frangulanin) and seeds (perlolyrin), and organic acids (vanillic and ferulic) in hot water extract from seeds. Finally, peduncles have plenty of polysaccharides which justify the use as a food supplement. The aim of this work is to review the whole scientific production, with special focus on the last decade, in order to update phytochemistry, biological activities, nutritional properties, toxicological aspect and regulatory classification of H. dulcis extracts for its use in the European Union.     

Defining the Human-Biota Thresholds of Toxicological Concern for Organic Chemicals in Freshwater: The Proposed Strategy of the LIFE VERMEER Project Using VEGA Tools

Several tons of chemicals are released every year into the environment and it is essential to assess the risk of adverse effects on human health and ecosystems. Risk assessment is expensive and time-consuming and only partial information is available for many compounds. A consolidated approach to overcome this limitation is the Threshold of Toxicological Concern (TTC) for assessment of the potential health impact and, more recently, eco-TTCs for the ecological aspect. The aim is to allow a safe assessment of substances with poor toxicological characterization. Only limited attempts have been made to integrate the human and ecological risk assessment procedures in a “One Health” perspective. We are proposing a strategy to define the Human-Biota TTCs (HB-TTCs) as concentrations of organic chemicals in freshwater preserving both humans and ecological receptors at the same time. Two sets of thresholds were derived: general HB-TTCs as preliminary screening levels for compounds with no eco- and toxicological information, and compound-specific HB-TTCs for chemicals with known hazard assessment, in terms of Predicted No effect Concentration (PNEC) values for freshwater ecosystems and acceptable doses for human health. The proposed strategy is based on freely available public data and tools to characterize and group chemicals according to their toxicological profiles. Five generic HB-TTCs were defined, based on the ecotoxicological profiles reflected by the Verhaar classes, and compound-specific thresholds for more than 400 organic chemicals with complete eco- and toxicological profiles. To complete the strategy, the use of in silico models is proposed to predict the required toxicological properties and suitable models already available on the VEGAHUB platform are listed.     

A Metal-Based Receptor for Selective Coordination and Fluorescent Sensing of Chloride

A scorpionate Zn²⁺ complex, constituted by a macrocyclic pyridinophane core attached to a pendant arm containing a fluorescent pyridyl-oxadiazole-phenyl unit (PyPD), has been shown to selectively recognize chloride anions, giving rise to changes in fluorescence emission that are clearly visible under a 365 nm UV lamp. This recognition event has been studied by means of absorption, fluorescence, and NMR spectroscopy, and it involves the intramolecular displacement of the PyPD unit by chloride anions. Moreover, since the chromophore is not removed from the system after the recognition event, the fluorescence can readily be restored by elimination of the bound chloride anion.