Molecular associations of hydrazones of heterocyclic systems. XI

Complexes of hydrazones of heterocyclic compounds with organic acceptors are investigated through the evaluation of spectroscopic and thermodynamic properties. Values of the formation constants and comparison between uv-visible and ft-ir determinations on liquid and solid phases indicate these systems are weak complexes. Contributions from hydrogen bonding and the effects of π?π* or n?π* transitions on the spectroscopic and thermodynamic properties of the complexes are discussed.     

Interacting fermions in highly elongated harmonic traps

Quasi-one-dimensional two-component Fermi gases with effectively attractive and repulsive interactions are characterized for arbitrary interaction strength. The ground-state properties of the gas confined in highly elongated harmonic traps are determined within the local density approximation. For strong attractive effective interactions the existence of a molecular Tonks-Girardeau gas is predicted. The frequency of the lowest breathing mode is calculated as a function of the coupling strength for both attractive and repulsive interactions.     

Optimization of CR-39 for fast neutron dosimetry applications

We present the results of an experimental work aimed at improving the performances of the CR-39^® (Registered Trademark of PPG Industries Inc.) nuclear track detector for neutron dosimetry applications. The work was done in collaboration with the Intercast Europe S.p.A., producer of CR-39 for commercial and scientific applications. We compare the CR-39 made with different additives concentrations and different polymerization processes. We evaluate the response of the CR-39 to fast neutrons from three sources: ²⁴¹Am---Be, ²⁵²Cf and ²³⁸Pu---Li. Particular attention was paid to background fluctuations that limit the lower detectable dose.     

Berberine Derivatives as Pseudomonas aeruginosa MexXY-OprM Inhibitors: Activity and In Silico Insights

The natural alkaloid berberine has been demonstrated to inhibit the Pseudomonas aeruginosa multidrug efflux system MexXY-OprM, which is responsible for tobramycin extrusion by binding the inner membrane transporter MexY. To find a structure with improved inhibitory activity, we compared by molecular dynamics investigations the binding affinity of berberine and three aromatic substituents towards the three polymorphic sequences of MexY found in P. aeruginosa (PAO1, PA7, and PA14). The synergy of the combinations of berberine or berberine derivatives/tobramycin against the same strains was then evaluated by checkerboard and time-kill assays. The in silico analysis evidenced different binding modes depending on both the structure of the berberine derivative and the specific MexY polymorphism. In vitro assays showed an evident MIC reduction (32-fold and 16-fold, respectively) and a 2–3 log greater killing effect after 2 h of exposure to the combinations of 13-(2-methylbenzyl)- and 13-(4-methylbenzyl)-berberine with tobramycin against the tobramycin-resistant strain PA7, a milder synergy (a 4-fold MIC reduction) against PAO1 and PA14, and no synergy against the ΔmexXY strain K1525, confirming the MexY-specific binding and the computational results. These berberine derivatives could thus be considered new hit compounds to select more effective berberine substitutions and their common path of interaction with MexY as the starting point for the rational design of novel MexXY-OprM inhibitors.     

Silver coordination complexes as room-temperature multifunctional materials

A series of bischelate ionic silver complexes [Ag(L*)(2)][X] was prepared by complexation of a newly synthesized 2,2'-bipyridine containing chiral alkoxy chains in the 4,4' positions. The appropriate choice of the construction motifs allows the preparation of new materials in which several functionalities can be introduced. Indeed, when the anion X(-) is a triflate or a dodecylsulfate group, the right combination of intermolecular interactions promotes the production of liquid crystalline mesophases. Therefore, the presence of coordinating anions, which drives the supramolecular assembly, is essential to generate, at the same time, room-temperature columnar hexagonal mesomorphism, the columnar helical supramolecular structure, and excimeric emission.     

The Laser Raman Spectrum of Cyclobutanone

In a recent paper, ¹ we discussed the vibrational spectrum of crystalline Cyclobutanone (CBN) with the main concern over the crystal form stable at 100K. From the dichroism of the infrared bands, the nature of the solid state splittings was ascertained and conclusions were drawn on the symmetry of the unit cell. In doing this, use was made of the crystal Raman spectrum of CBN, to infer the existence of the center of symmetry in the unit cell and to predict the selection rules of the C⁵ _2h space group.     

A study on the interactions between coenzyme Q 0 and superoxide anion. Could ubiquinones mimic superoxide dismutase (SOD)?

An electrochemical study was carried out on 1,4-benzoquinone, duroquinone, coenzymes Q ₀ and Q ₁₀ in the absence and in the presence of molecular oxygen in aprotic (DMF) and protic (DMF/H₂O 95:5 (v/v)) media. Water was added because the investigated reactions are deeply influenced by the presence of protons. Q ₀ and Q ₁₀ exhibited a similar electrochemical behaviour. Since Q ₀ is more soluble in protic medium than the biologically more important analogue Q ₁₀ , it was chosen as a model for a more detailed investigation. Voltammetric studies of Q ₀ carried out in aprotic and protic media in the presence of oxygen showed that, besides simple O₂ ^·− dismutation, the Q ₀ promoted dismutation of O₂ ^·− should also be considered. Spectroelectrochemical experiments with the same experimental conditions support the electrochemical results, showing that in the presence of superoxide and in aprotic medium semiquinone Q ₀ ^·− gives rise to a disproportionation equilibrium, while in the presence of water it tends to be reoxidized to the starting Q ₀ by OOH^·. EPR measurements are also in agreement with these results.     

Density, Refractive Index, and Related Properties for 2-Butanone + n-Hexane Binary Mixtures at Various Temperatures

Density refractive index n and the related properties molar volume V and molar refraction R have been investigated for 2-butanone + n-hexane liquid binary mixtures over the entire composition range and a wide range of temperatures. Some well-known relationships have been applied to study the temperature and composition dependence of the measured and derived quantities. Furthermore, the deviations of the respective excess properties V ^E, n ^E, and R ^E have been examined, with the aim of identifying particular intermolecular interaction patterns responsible for the macroscopic behavior of these binary mixtures. The results have been interpreted on the basis of structural and geometric effects between the components.