A prototype calix[4]arene-based receptor for carbohydrate recognition containing peptide and phosphate binding groups

A novel class of macrobicyclic receptors for carbohydrate recognition based on upper rim, peptide-bridged calix[4]arenes has been designed and synthesized. Receptor 12, in which a charged phosphate group cooperates with peptide hydrogen-bonding donor and acceptor groups in the binding process, is the most efficient and selective in the complexation of simple carbohydrate derivatives. The selectivity observed is toward beta-glucoside 13a, which is better bound (DeltaG degrees = 19.6 kJ mol(-)(1)) compared to the corresponding alpha anomer 13b (DeltaG degrees = 17.0 kJ mol(-)(1)) and to the beta-galactoside 13c (DeltaG degrees = 17.7 kJ mol(-)(1)) in CDCl(3). A substantial drop in the stability constant is observed by esterification of the phosphate group in the host 12 or by alkylation of the OH groups in the 2 and 3 positions in the beta-glucoside and beta-galactoside derivatives. On the basis of a careful analysis of the (1)H NMR data available, a binding mode of the beta-octylglucoside 13a to receptor 12 is proposed.     

X-ray structure of dodecasodium tricopper(II)bis[nonatungstabismuthate(III) hydrate, a polyoxometalate salt containing α-B-BiW9O33 units

The reaction of [Bi₂W₂₂O₇₄(OH)₂]^12– with Cu²⁺ in hot aqueous solution in the presence of Na⁺ affords the polyoxometalate salt Na₁₂[Cu₃Bi₂W₁₈O₆₆]32H₂O. Single-crystal X-ray analysis [monoclinic, space-group C2/m, a = 33.082(6) Å, b = 19.615(5) Å, c = 14.885(2) Å, = 90.632(12)°, Z = 4; R(F) = 0.065 for 6029 data with I> (I), wR(F ²) = 0.135 for all 8793 independent reflections] shows that the anion [{Cu(H₂O)}₃{BiW₉O₃₃}₂]^12–, on a crystal mirror-plane, has noncrystallographic symmetry close to D_3h. Two B--[Bi^IIIW₉O₃₃]^9– units are linked by an equatorial belt of three Cu(H₂O)²⁺ units. Three Na(H₂O)₂ ⁺ units are also attached in the equatorial plane. The bond geometry is square-pyramidal about each Cu atom and trigonal–prismatic about each Na.     

Sol-Gel Nanosized Semiconducting Titania-Based Powders for Thick-Film Gas Sensors

Pure, 5 at%, and 10 at% Ta- or Nb-doped TiO₂ nanosized powders were prepared by the sol-gel method. The powders heated to 400°C have the crystalline anatase structure. While the pure TiO₂ powder heated to 850°C has the rutile structure, the addition of Ta and Nb inhibited the anatase-to-rutile phase transformation at this temperature. Ta was soluble in the titania lattice up to the concentration of 10 at%, while the solubility of Nb was 5 at%. Thick films were fabricated with these powders by screen printing technology and then fired at 650°C and 850°C for 1 h. SEM observations showed that the anatase-to-rutile phase transformation induces a grain growth of about one order of magnitude for pure TiO₂. The addition of Ta and Nb is effective to keep the TiO₂ grain size at the nanometric level even at 850°C. Conductance measurements showed that a good gas response is observed only for the nanostructured titania-based films. The CO response of these materials is only slightly affected by humidity.     

Development of a Sequential Injection Analysis Device for the Determination of Total Polyphenol Index in Wine

A sequential injection analysis method is developed for the determination of the total polyphenol index in wines. The determination is based on the Folin-Ciocalteu reaction, which is monitored spectrophotometrically. Interactions between experimental variables and their optimal levels were investigated using factorial designs. The proposed system is fully computerised and is able to monitor polyphenol index in real samples of white, sweet and red wines. The calibration graph is linear from 5 to 200mg·L^–1 using Tannic acid as standard, with a detection limit of 3.2mg·L^–1. Interferences are studied. For validation purposes the proposed methodology was applied to the determination of the total polyphenol index in different types of wines and compared with earlier alternatives in order to assess their performance.     

Green Synthesis of Gold and Silver Nanoparticles Using Leaf Extract of Capsicum chinense Plant

So far, several studies have focused on the synthesis of metallic nanoparticles making use of extracts from the fruit of the plants from the genus Capsicum. However, as the fruit is the edible, and highly commercial, part of the plant, in this work we focused on the leaves, a part of the plant that is considered agro-industrial waste. The biological synthesis of gold (AuNPs) and silver (AgNPs) nanoparticles using aqueous extracts of root, stem and leaf of Capsicum chinense was evaluated, obtaining the best results with the leaf extract. Gold and silver nanoparticles synthesized using leaf extract (AuNPs-leaf and AgNPs-leaf, respectively) were characterized by UV-visible spectrophotometry (UV-Vis), Fourier Transform Infrared Spectroscopy with Attenuated Total Reflection (FTIR-ATR), X-ray Photoelectron Spectroscopy (XPS), Ultra Hight Resolution Scanning Electron Microscopy coupled to Energy-Dispersive X-ray spectroscopy (UHR-SEM-EDX) and Transmission Electron Microscopy (TEM), and tested for their antioxidant and antimicrobial activities. In addition, different metabolites involved in the synthesis of nanoparticles were analyzed. We found that by the use of extracts derived from the leaf, we could generate stable and easy to synthesize AuNPs and AgNPs. The AuNPs-leaf were synthesized using microwave radiation, while the AgNPs-leaf were synthesized using UV light radiation. The antioxidant activity of the extract, determined by ABTS, showed a decrease of 44.7% and 60.7% after the synthesis of the AuNPs-leaf and AgNPs-leaf, respectively. After the AgNPs-leaf synthesis, the concentration of polyphenols, reducing sugars and amino acids decreased by 15.4%, 38.7% and 46.8% in the leaf extract, respectively, while after the AuNPs-leaf synthesis only reducing sugars decreased by 67.7%. These results suggest that these groups of molecules are implicated in the reduction/stabilization of the nanoparticles. Although the contribution of these compounds in the synthesis of the AuNPs-leaf and the AgNPs-leaf was different. Finally, the AgNPs-leaf inhibited the growth of S. aureus, E. coli, S. marcescens and E. faecalis. All of them are bacterial strains of clinical importance due to their fast antibiotic resistance development.     

An Insight into Kiwiberry Leaf Valorization: Phenolic Composition,Bioactivity and Health Benefits

During kiwiberry production, different by-products are generated, including leaves that are removed to increase the fruit’s solar exposure. The aim of this work was to extract bioactive compounds from kiwiberry leaf by employing microwave-assisted extraction (MAE). Compatible food solvents (water and ethanol) were employed. The alcoholic extract contained the highest phenolic and flavonoid contents (629.48 mg of gallic acid equivalents (GAE) per gram of plant material on dry weight (dw) (GAE/g dw) and 136.81 mg of catechin equivalents per gram of plant material on dw (CAE/g dw), respectively). Oppositely, the hydroalcoholic extract achieved the highest antioxidant activity and scavenging activity against reactive oxygen and nitrogen species (IC₅₀ = 29.10 μg/mL for O₂^•−, IC₅₀ = 1.87 μg/mL for HOCl and IC₅₀ = 1.18 μg/mL for ^•NO). The phenolic profile showed the presence of caffeoylquinic acids, proanthocyanidin, and quercetin in all samples. However, caffeoylquinic acids and quercetin were detected in higher amounts in the alcoholic extract, while proanthocyanidins were prevalent in the hydroalcoholic extract. No adverse effects were observed on Caco-2 viability, while the highest concentration (1000 µg/mL) of hydroalcoholic and alcoholic extracts conducted to a decrease of HT29-MTX viability. These results highlight the MAE potentialities to extract bioactive compounds from kiwiberry leaf.     

Wettability of cellular polyurethane

Cellular polymers constitute an important field of investigation due to their unique properties as shock absorbers and thermal or acoustic insulators. The knowledge of the wetting properties of these materials is important in applications where adhesion or weathering behavior are an issue. In this study, cellular polyurethane polymers were used to investigate the effect of the cellular structure on the wetting properties. The polymeric substrates were analyzed by scanning electron microscopy and the wetting properties were studied by goniometry. The contact angles of water and diiodomethane were measured as a function of time and the surface tension of the expanded polymers was evaluated by the geometric and harmonic mean methods. It was found that the wettability and the surface energy of the cellular polymers increase as the density decreases. © 1997 John Wiley & Sons, Inc.     

Lead-free ferroelectric BaTiO3 doped-(Na0.5Bi0.5)TiO3 thin films processed by pulsed laser deposition technique

The difficulties in synthesizing phase pure BaTiO₃ doped-(Na_0.5Bi_0.5)TiO₃ are known. In this work, we reporting the optimized pulsed laser deposition (PLD) conditions for obtaining pure phase 0.92(Na_0.5Bi_0.5)TiO₃-0.08BaTiO₃, (BNT-BT_0.08), thin films. Dielectric, ferroelectric and piezoelectric properties of BNT-BT_0.08, thin films deposited by PLD on Pt/TiO₂/SiO₂/Si substrates are investigated in this paper. Perovskite structure of BNT-BT_0.08 thin films with random orientation of nanocrystallites has been obtained by deposition at 600 °C. The relative dielectric constant and loss tangent at 100 kHz, of BNT-BT_0.08 thin film with 530 nm thickness, were 820 and 0.13, respectively. Ferroelectric hysteresis measurements indicated a remnant polarization value of 22 μC/cm² and a coercive field of 120 kV/cm. The piezoresponse force microscopy (PFM) data showed that most of the grains seem to be constituted of single ferroelectric domain. The as-deposited BNT-BT_0.08 thin film is ferroelectric at the nanoscale level and piezoelectric.     

Multiple response optimization for Cu, Fe and Pb determination in naphtha by graphite furnace atomic absorption spectrometry with sample injection as detergent emulsion

The present paper reports the optimization for Cu, Fe and Pb determination in naphtha by graphite furnace atomic absorption spectrometry (GF AAS) employing a strategy based on the injection of the samples as detergent emulsions. The method was optimized in relation to the experimental conditions for the emulsion formation and taking into account that the three analytes (Cu, Fe and Pb) should be measured in the same emulsion. The optimization was performed in a multivariate way by employing a three-variable Doehlert design and a multiple response strategy. For this purpose, the individual responses of the three analytes were combined, yielding a global response that was employed as a dependent variable. The three factors related to the optimization process were: the concentration of HNO₃, the concentration of the emulsifier agent (Triton X-100 or Triton X-114) in aqueous solution used to emulsify the sample and the volume of solution. At optimum conditions, it was possible to obtain satisfactory results with an emulsion formed by mixing 4 mL of the samples with 1 mL of a 4.7% w/v Triton X-100 solution prepared in 10% v/v HNO₃ medium. The resulting emulsion was stable for 250 min, at least, and provided enough sensitivity to determine the three analytes in the five samples tested. A recovery test was performed to evaluate the accuracy of the optimized procedure and recovery rates, in the range of 88-105%; 94-118% and 95-120%, were verified for Cu, Fe and Pb, respectively.     

Primitive rispetto all’ oscillazione

We study the real valued functions having a primitive with respect to the oscillation or a primitive with respect to the oscillation up to anegligible set.

---

---

Supported by MURST of Italy.