Quantum mechanical calculations of conformationally relevant 1H and 13C NMR chemical shifts of N-, O-, and S-substituted calixarene systems

QM GIAO calculations of (13)C and (1)H chemical shift values of the ArCH(2)Ar group in N-, O-, and S-substituted calixarene systems were performed with a hybrid DFT functional MPW1PW91 and 6-31G(d,p) basis set. A good reproduction of experimental data was obtained for some representative calixarenes and for a series of simplified calixarene models. This allowed the derivation of chemical shift surfaces versus phi and chi dihedral angles. The applicability of chemical shift surfaces in the study of calixarene conformational features is illustrated.     

l-Arginine Improves Solubility and ANTI SARS-CoV-2 Mpro Activity of Rutin but Not the Antiviral Activity in Cells

The COVID-19 pandemic outbreak prompts an urgent need for efficient therapeutics, and repurposing of known drugs has been extensively used in an attempt to get to anti-SARS-CoV-2 agents in the shortest possible time. The glycoside rutin shows manifold pharmacological activities and, despite its use being limited by its poor solubility in water, it is the active principle of many pharmaceutical preparations. We herein report our in silico and experimental investigations of rutin as a SARS-CoV-2 Mpro inhibitor and of its water solubility improvement obtained by mixing it with l-arginine. Tests of the rutin/l-arginine mixture in a cellular model of SARS-CoV-2 infection highlighted that the mixture still suffers from unfavorable pharmacokinetic properties, but nonetheless, the results of this study suggest that rutin might be a good starting point for hit optimization.     

Contouring of artwork surface by fringe projection and FFT analysis

In the present work, we propose a simple optical method to perform profilometry on works of art. The method is based on the projection of a Ronchi grating onto the surface to be analyzed. When viewed at an angle different from the projection angle, the grid pattern appears deformed by the surface shape. This pattern is digitized, by a high-resolution CCD camera, and then processed using a Fourier transform analysis. The technique is free from the errors caused by higher harmonic components of the grating pattern. Furthermore, the method relies on very simple equipment and it is therefore suitable for in situ measurements. Theoretical details and examples of the technique in operation are given.     

Kabuli and Apulian black Chickpea Milling By-Products as Innovative Ingredients to Provide High Levels of Dietary Fibre and Bioactive Compounds in Gluten-Free Fresh Pasta

Gluten-free (GF) products, including pasta, are often characterised by nutritional deficiencies, such as scarce dietary fibre and excess of calories. Chickpea flour is increasingly being used by the food industries. Hulls, rich in dietary fibre and bioactive compounds, are discarded after milling. The aim of this work was to evaluate the quality features of short-cut GF fresh pasta added of hull (8% w/w) derived from kabuli (KH) or Apulian black (ABH) chickpeas, in comparison with control GF pasta prepared without hull. The enriched pasta, which could be labelled as “high fibre”, was characterised by a higher level of bioactive compounds and antioxidant activity than the control. ABH-enriched pasta showed the highest anthocyanins (33.37 ± 1.20 and 20.59 ± 0.11 mg/kg of cyanidin-3-O-glucoside on dry matter in raw and cooked pasta, respectively). Hull addition increased colour intensity and structural quality of GF pasta: ABH-enriched pasta had the lowest cooking loss and the highest water absorption capacity; KH-enriched pasta showed the highest firmness. No significant differences in sensory liking were found among the samples, except for “aftertaste”. Chickpea hull can be used as an innovative ingredient to produce potentially functional GF pasta, meeting the dietary needs of consumers without affecting quality.     

Dynamic switching between binding sites in the complexation of macrocyclic ‘push-pull’ chromophores to lanthanides

The introduction of a 1,3-diacetylpyridine moiety, as an additional binding niche in a macrocyclic receptor ligand containing a conjugated, push-pull malonate functionality, leads to, in addition to the 1:1 binding stoichiometry, the equilibrium formation of multiple complexes, specifically 1:2, 2:1, and 3:1 ligand:metal complexes with lanthanide trications. Various binding modes elicit distinctive responses in the visible region, which enhance the potential recognition of lanthanide ions. This paper also highlights the usefulness of a full factor analysis in the elucidation of complex binding phenomena.     

Sampling soil-derived CO2 for analysis of isotopic composition: a comparison of different techniques

A new system for soil respiration measurement [P. Rochette, L.B. Flanagan, E.G. Gregorich. Separating soil respiration into plant and soil components using analyses of the natural abundance of carbon-13. Soil Sci. Soc. Am. J., 63, 1207-1213 (1999).] was modified in order to collect soil-derived CO2 for stable isotope analysis. The aim of this study was to assess the suitability of this modified soil respiration system to determine the isotopic composition (delta13C) of soil CO2 efflux and to measure, at the same time, the soil CO2 efflux rate, with the further advantage of collecting only one air sample. A comparison between different methods of air collection from the soil was carried out in a laboratory experiment. Our system, as well as the other dynamic chamber approach tested, appeared to sample the soil CO2, which is enriched with respect to the soil CO2 efflux, probably because of a mass dependent fractionation during diffusion and because of the atmospheric contribution in the upper soil layer. On the contrary, the static accumulation of CO2 into the chamber headspace allows sampling of delta13C-CO2 of soil CO2 efflux.     

Novel topological insulators from crystalline symmetries

We discuss recent advances in the study of topological insulators protected by spatial symmetries by reviewing three representative, theoretical examples. In three dimensions (3D), these states of matter are generally characterized by the presence of gapless boundary states at surfaces that respect the protecting spatial symmetry. We discuss the appearance of these topological states in both crystals with negligible spin–orbit coupling and a fourfold rotational symmetry, as well as in mirror-symmetric crystals with sizable spin–orbit interaction characterized by the so-called mirror Chern number. Finally, we also discuss similar topological crystalline states in one-dimensional (1D) insulators, such as nanowires or atomic chains, with mirror symmetry. There, the prime physical consequence of the non-trivial topology is the presence of quantized end charges.     

An intramolecularly self-templated synthesis of macrocycles: self-filling effects on the formation of prismarenes

Ethyl- and propyl-prism[6]arenes are obtained in high yields and in short reaction times, independent of the nature and size of the solvent, in the cyclization of 2,6-dialkoxynaphthalene with paraformaldehyde. PrS[6]Et or PrS[6]nPr adopt, both in solution and in the solid state, a folded cuboid-shaped conformation, in which four inward oriented alkyl chains fill the cavity of the macrocycle. On these bases, we proposed that the cyclization of PrS[6]Et or PrS[6]nPr occurs through an intramolecular thermodynamic self-templating effect. In other words, the self-filling of the internal cavity of PrS[6]Et or PrS[6]nPr stabilizes their cuboid structure, driving the equilibrium toward their formation. Molecular recognition studies, both in solution and in the solid state, show that the introduction of guests into the macrocycle cavity forces the cuboid scaffold to open, through an induced-fit mechanism. An analogous conformational change from a closed to an open state occurs during the endo-cavity complexation process of the pentamer, PrS[5]. These results represent a rare example of a thermodynamically controlled cyclization process driven through an intramolecular self-template effect, which could be exploited in the synthesis of novel macrocycles.

Ethyl- and propyl-prism[6]arenes are obtained by an intramolecular thermodynamic self-template effect: the self-filling of the internal cavity stabilizes their cuboid structure, driving the equilibrium toward their formation.     

Permeability spectra of Co2Z hexaferrite compacts produced via a modified aqueous co-precipitation technique

Co₂Z hexaferrite materials possess intrinsically high permeability, zero field ferromagnetic resonance values (∼1 GHz), and have their magnetic orientation in the plane perpendicular to the c-axis. These characteristics make these materials practical for applications in low to mid ultra-high frequency and L-band microwave device designs. Due to the relatively large size of elements operating within these bands, it has become important to produce large amounts of Co₂Z type hexaferrite materials. A modified co-precipitation method has been proposed to produce scalable quantities of high quality Co₂Z hexaferrite particles, at ∼24 g/L. These particles have been thoroughly characterized by vibrating sample magnetometry (VSM) and X-ray diffraction (XRD) with regard to phase purity and magnetic properties. After formation and subsequent ball milling, to achieve single domain particles on the order of 0.5–2 um, particles were oriented and pressed into compacts inside a rotating field to ensure magnetization in plane. Samples then underwent VSM, XRD, and scanning electron microscopy to determine the orientation effect. In addition, the complex permittivity and permeability of these samples were measured as a function of applied field and processing conditions. The results show strong orientation in these compacts making them practical for a variety of device applications.     

Quasiparticle relaxation mechanisms in superconductor/ferromagnet bilayers

In this paper we review some recent results obtained on superconducting/ferromagnetic (S/F) structures when measuring the dynamic instabilities of the vortex lattice at high driving currents. The role played on the non-equilibrium properties of the hybrids by both the ferromagnetic and the superconducting materials has been analyzed with a special focus on the values and the temperature dependence of the quasiparticle relaxation times, τ(E). Knowledge of the relaxation mechanisms in these systems is extremely important in view of possible applications since it can drive the optimal choice of both materials to realize, in particular, ultrafast superconducting single photon detectors based on S/F hybrid structures.