Covalent Cross-Linking of 2H-MoS2 Nanosheets

The combination of 2D materials opens a wide range of possibilities to create new-generation structures with multiple applications. Covalently cross-linked approaches are a ground-breaking strategy for the formation of homo or heterostructures made by design. However, the covalent assembly of transition metal dichalcogenides flakes is relatively underexplored. Here, a simple covalent cross-linking method to build 2H-MoS₂–MoS₂ homostructures is described, using commercially available bismaleimides. These assemblies are mainly connected vertically, basal plane to basal plane, creating specific molecular sized spaces between MoS₂ sheets. Therefore, this straightforward approach gives access to the controlled connection of sulfide-based 2D materials.     

An Ant Colony Optimisation algorithm for solving the asymmetric traffic assignment problem

In this paper we propose an Ant Colony Optimisation (ACO) algorithm for defining the signal settings on urban networks following a local approach. This consists in optimising the signal settings of each intersection of an urban network as a function only of traffic flows at the accesses to the same intersection, taking account of the effects of signal settings on costs and on user route choices. This problem, also known as Local Optimisation of Signal Settings (LOSS), has been widely studied in the literature and can be formulated as an asymmetric assignment problem. The proposed ACO algorithm is based on two kinds of behaviour of artificial ants which allow the LOSS problem to be solved: traditional behaviour based on the response to pheromones for simulating user route choice, and innovative behaviour based on the pressure of an ant stream for solving the signal setting definition problem. Our results on real-scale networks show that the proposed approach allows the solution to be obtained in less time but with the same accuracy as in traditional MSA (Method of Successive Averages) approaches.     

A pH-Induced Reversible Conformational Switch Able to Control the Photocurrent Efficiency in a Peptide Supramolecular System

External stimuli are potent tools that Nature uses to control protein function and activity. For instance, during viral entry and exit, pH variations are known to trigger large protein conformational changes. In Nature, also the electron transfer (ET) properties of ET proteins are influenced by pH-induced conformational changes. In this work, a pH-controlled, reversible 3₁₀-helix to α-helix conversion (from acidic to highly basic pH values and vice versa) of a peptide supramolecular system built on a gold surface is described. The effect of pH on the ability of the peptide SAM to generate a photocurrent was investigated, with particular focus on the effect of the pH-induced conformational change on photocurrent efficiency. The films were characterized by electrochemical and spectroscopic techniques, and were found to be very stable over time, also in contact with a solution. They were also able to generate current under illumination, with an efficiency that is the highest recorded so far with biomolecular systems.     

Differences in Salivary Proteins as a Function of PROP Taster Status and Gender in Normal Weight and Obese Subjects

Taste plays an important role in processes such as food choices, nutrition status and health. Salivary proteins contribute to taste sensitivity. Taste reduction has been associated with obesity. Gender influences the obesity predisposition and the genetic ability to perceive the bitterness of 6-n-propylthiouracil (PROP), oral marker for food preferences and consumption. We investigated variations in the profile of salivary proteome, analyzed by HPLC-ESI-MS, between sixty-one normal weight subjects (NW) and fifty-seven subjects with obesity (OB), based on gender and PROP sensitivity. Results showed variations of taste-related salivary proteins between NW and OB, which were differently associated with gender and PROP sensitivity. High levels of Ps-1, II-2 and IB-1 proteins belonging to basic proline rich proteins (bPRPs) and PRP-1 protein belonging to acid proline rich proteins (aPRPs) were found in OB males, who showed a lower body mass index (BMI) than OB females. High levels of Ps-1 protein and Cystatin SN (Cyst SN) were found in OB non-tasters, who had lower BMI than OB super-tasters. These new insights on the role of salivary proteins as a factor driving the specific weight gain of OB females and super-tasters, suggest the use of specific proteins as a strategic tool modifying taste responses related to eating behavior.     

Poly(ionic liquid)s derived from 3‐octyl‐1‐vinylimidazolium bromide and N‐isopropylacrylamide with tunable properties

A new series of linear and crosslinked copolymers, obtained from 3‐octyl‐1‐vinylimidazolium bromide (VImBr) and N‐isopropylacrylamide (NIPAAm), were prepared by radical polymerization. Namely, VImBr was synthesized from 1‐bromooctane and an ionic liquid such as 1‐vinylimidazole. NIPAAm was used because it gives raise to well known thermoresponsive (co‐)polymers. The copolymers were thoroughly characterized by means of ¹H NMR and ¹³C NMR spectroscopies. Besides, differential scanning calorimetry, Fourier transform infrared spectroscopy, and scanning electron microscopy were also used. Moreover, the swelling behavior and the thermoresponsive properties of the corresponding hydrogels were studied. It was found that the VImBr incorporation into the copolymers does have a dramatic influence on both the thermal properties of the dried materials and the lower critical solution temperature of the corresponding hydrogels. In detail, the glass transition temperature was dependent on the monomer ratios, and ranged from 5 to 155 °C. Analogously, the lower critical solution temperature of the resulting hydrogels ranged from less than 10 up to 38 °C, thus including the physiological temperature. NMR spectroscopies, which were performed on the linear polymers, indicated that the monomers exhibit an alternating tendency resulting in a microstructure in which blocks are not present, at least when the two monomers are in equimolar amounts. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3521–3532     

A Study of the Thorpe-Ziegler Reaction in Very Mild Conditions

The Thorpe-Ziegler reaction has been used in the preparation of enaminonitriles and cyclic ketones for many years. A wide variety of bases¹ have been employed to acomplish this reaction, the most effective being the alkali metal salts of aralkyl amines. The reaction conditions vary from room temperature to toluene reflux temperature for long periods of time¹.     

Synthesis in Water and Antimicrobial Activity of 5-Trichloromethyl-4,5-dihydroisoxazoles

Two series of 5-trichloromethylisoxazoles were synthesized from the cyclocondensation of 1,1,1-trichloro-4-methoxy-3-alken-2-ones [Cl₃CC(O)C(R²) = C(R¹)OMe, where R¹ = H, Me, Et, Pr, iso-Pr, cyclo-Pr, Bu, terc-Bu, CH₂Br, CHBr₂, CH(Me)SMe, (CH₂)₂Ph, and Ph, and R² = H; R¹ = H and R² = Me and Et; R¹ and R² = -(CH₂)₄- and -(CH₂)₅-; and R¹ = Et and Ph and R² = Me] with hydroxylamine hydrochloride through a rapid one-pot reaction in water. The 5-trichloromethyl-4,5-dihydroisoxazoles were aromatized by reaction with concentrated sulfuric acid to obtain the respective 5-trichloromethylisoxazoles. Their structures were confirmed by elemental analysis, ¹H/¹³C nuclear magnetic resonance, and electron impact mass spectroscopy. Crystal structure analysis for 5-triclhoromethyl-5-hydroxy-3-propyl-4,5-dihydroisoxazole (2d) and 5-trichloromethyl-5-hydroxy-3,4-hexamethylene-4,5-dihydroisoxazole (2o) is presented. The antimicrobial activities of the 5-trichloromethyl-4,5-dihydroisoxazole derivatives were examined using the standard twofold dilution method against Gram-positive bacteria (Staphylococcus aureus), Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), and yeasts (Candida spp. and Cryptococcus neoformans). All of the tested 5-trichloromethyldihydroisoxazoles exhibited antibacterial and antifungal activities at the tested concentrations.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Implementation of the k 0-standardization method for analysis of geological samples at the Neutron Activation Analysis Laboratory, São Paulo, Brazil

The Neutron Activation Analysis Laboratory (LAN-IPEN) has been analysing geological samples for many years with the INAA comparative method, for geochemical and environmental research. This study presents the results obtained in the implementation of the k ₀-standardization method at LAN-IPEN, for geological samples analysis, by using the program k ₀-IAEA, provided by the International Atomic Energy Agency (IAEA). The thermal to epithermal flux ratio f and the shape factor α of the epithermal flux distribution of the IEA-R1 nuclear reactor of IPEN were determined for the pneumatic irradiation facility and one selected irradiation position, for short and long irradiations, respectively. To obtain these factors, the “bare triple-monitor” method with ¹⁹⁷Au–⁹⁶Zr–⁹⁴Zr was used. In order to validate the methodology, the geological reference materials basalts JB-1 (GSJ) and BE-N (IWG-GIT), andesite AGV-1 (USGS), granite GS-N (ANRT), SOIL-7 (IAEA) and sediment Buffalo River Sediment (NIST–BRS-8704), which represent different geological matrices, were analysed. The concentration results obtained agreed with assigned, with bias <10 % except for Zn in AGV-1. The U-score test showed that all results, except Mg in JB-1, are within 95 % confidence interval. These results indicate excellent possibilities of using this parametric method at the LAN-IPEN for geochemical and environmental studies.