Attività biologica e studi di docking di derivati bis-ammidici dell'acido 5,6- diidrossiindolo-2-carbossilico come inibitori dell'enzima HIV-1 integrasi

In un precedente studio, nel tentativo di identificare nuovi inibitori dell'HIV-1 integrasi, è stata da noi considerata la modifica strutturale dell'estere feniletilico dell'acido caffeico I (CAPE), il primo prodotto naturale inibitore dell'IN identificato, incorporando il legame vinilico del CAPE all'interno di una struttura rigida costituita dall'anello pirrolico. In questa comunicazione, a completamento dello studio svolto, noi presentiamo i dati relativi all'attività  inibitoria enzimatica per i derivati IIIe-i, lo studio SAR per tutti i derivati ed uno studio di docking nel sito attivo dell'HIV-1 IN eseguito al fine di investigare le possibili interazioni tra i ligandi e gli a.a. del sito catalitico

A Multi-Channel Low-Power System-on-Chip for in Vivo Recording and Wireless Transmission of Neural Spikes

This paper reports a multi-channel neural spike recording system-on-chip with digital data compression and wireless telemetry. The circuit consists of 16 amplifiers, an analog time-division multiplexer, a single 8 bit analog-to-digital converter, a digital signal compression unit and a wireless transmitter. Although only 16 amplifiers are integrated in our current die version, the whole system is designed to work with 64, demonstrating the feasibility of a digital processing and narrowband wireless transmission of 64 neural recording channels. Compression of the raw data is achieved by detecting the action potentials (APs) and storing 20 samples for each spike waveform. This compression method retains sufficiently high data quality to allow for single neuron identification (spike sorting). The 400 MHz transmitter employs a Manchester-Coded Frequency Shift Keying (MC-FSK) modulator with low modulation index. In this way, a 1.25 Mbit/s data rate is delivered within a limited band of about 3 MHz. The chip is realized in a 0.35 um AMS CMOS process featuring a 3 V power supply with an area of 3.1x 2.7 mm2. The achieved transmission range is over 10 m with an overall power consumption for 64 channels of 17.2 mW. This figure translates into a power budget of 269uW per channel, in line with published results but allowing a larger transmission distance and more efficient bandwidth occupation of the wireless link. The integrated circuit was mounted on a small and light board to be used during neuroscience experiments with freely-behaving rats. Powered by 2 AAA batteries, the system can continuously work for more than 100 hours allowing for long-lasting neural spike recordings

On the thermal and hydrothermal stability of spinel iron oxide nanoparticles as single and core-shell hard-soft phases

The thermal and hydrothermal stability of oleate-capped nanosized spinel iron oxides is of primary importance for the plethora of applications and environments for which they are employed. An in-situ XRD and ex-situ autoclave treatments have been set up for monitoring the thermal and hydrothermal stability in different samples. In detail, spinel iron oxide nanoparticles (NPs) were studied as (i) single-phase alone at three different sizes (about 6, 10, and 15 nm); (ii) as core in a core-shell architecture having cobalt ferrite as shell, at different core sizes (about 6 and 10 nm); (iii) as shell in a core-shell architecture with cobalt ferrite as core, at different shell thicknesses (about 3 and 4 nm). The Rietveld refinement of the diffraction patterns and 57Fe Mössbauer spectroscopy have been exploited to monitor the evolution of the structural parameters and the hematite fraction. Moreover, transmission electron microscopy has permitted to deepen the morphological details on the phases. The spinel iron oxide-hematite transition has been found size- and time-dependent for the single-phase iron oxide NPs (360–455 °C). The transition temperature has increased significantly when iron oxide is incorporated in a core-shell architecture, both as core (630 °C) and shell (520 °C), suggesting a stabilizing effect of cobalt ferrite. The hydrothermal stability of iron oxide and core-shell NPs has been found dependent on water content, time, and temperature, with a reducing effect of pentanol toward the formation of magnetite from maghemite, highlighted by 57Fe Mössbauer spectroscopy. The synergic effects of cobalt ferrite and pentanol have limited the formation of hematite, leading to the obtainment of magnetite-covered cobalt ferrite NPs upon the hydrothermal treatment

Intra-source provenance study on Monte Arci (Sardinia) obsidian by pXRF: Role of the data acquisition and analysis tools

In this work, a detailed study of Monte Arci obsidian sub-sources using the increasingly accessible technique of pXRF is presented based upon a large dataset of 68 geological samples, for the development of X-ray fluorescence-based analytical standardless procedure. In addition, a non-conventional (for obsidian provenance study) direct application of multivariate analysis on XRF spectra (continuous variables), rather than absolute concentrations or intensity ratios (discrete variables) is proposed. Results from different softwares and data analysis approaches (bi-/trivariate versus multivariate) were compared. In a blind test, the bi-/trivariate approach led to the correct assignment for the main SA, SB, and SC sub-sources, taking into account averaged values of intensity ratios with their standard deviation obtained from three independent measurements. A high intra-source variability for the SB subgroups was detected (almost 13% of error in the assignment, 9 samples out of 68). A non-conventional application of multivariate analysis was carried out directly on the XRF spectra and correct assignments were obtained for SA, SB1, SC groups, while 71% of the SB2 samples were correctly identified. The non-destructive analysis on 14 archaeological samples from Su Carroppu (Carbonia, southwestern Sardinia) rockshelter and from the Middle Neolithic (MN) 422 structure of the open-air dwelling site at Cuccuru is Arrius (Cabras, central-western Sardinia) permitted to test the method and hypothesise their provenance. The comparison with visual characterization or previous analyses by Particle Induced X-Ray Emission (PIXE) permitted to verify the correct provenance assignment of all artifacts for the bi-/trivariate method, and for 12/14 samples in the case of the multivariate one. The standardless analytical approach proposed in this work can represent a more general method exploitable for other obsidian sources, other glassy materials, besides other materials of archaeological interest

Nanostructured spinel cobalt ferrites: Fe and Co chemical state, cation distribution and size effects by X-ray photoelectron spectroscopy

Nanostructured spinel cobalt ferrite samples having crystallite size ranging between 5.6 and 14.1 nm were characterized by X-ray photoelectron spectroscopy and X-ray induced Auger electron spectroscopy in order to determine the chemical state of the elements, the iron/cobalt ratio and the cation distribution within tetrahedral and octahedral sites. The presence of size-dependent trends in the binding energy of the main photoelectron peaks and in the kinetic energy of the X-ray induced O KLL signal was also investigated. The results showed that iron is present as FeIII and cobalt is present as CoII. The iron/cobalt ratio determined by XPS ranges between 1.8 and 1.9 and it is in very good agreement, within experimental uncertainty, with the expected 2 : 1 ratio. The percentage of Fe in octahedral sites ranges between 62% and 64% for all samples. The kinetic energy of the O KLL signals increases with crystallite size. These results are explained in terms of changes in the ionicity of the metal–oxygen bonds. The results of this investigation highlight how the XPS technique represents a powerful tool to investigate the composition, the chemical state and inversion degree of cobalt spinel ferrites, contributing to the comprehension of their properties

Evolution of the Magnetic and Structural Properties with the Chemical Composition in Oleate-Capped MnxCo1- xFe2O4Nanoparticles

Understanding the complex link among composition, microstructure, and magnetic properties paves the way to the rational design of well-defined magnetic materials. In this context, the evolution of the magnetic and structural properties in a series of oleate-capped manganese-substituted cobalt ferrites (MnxCo1-xFe2O4) with variable Co/Mn molar ratios is deeply discussed. Single-phase ferrites with similar crystallite and particle sizes (about 10 nm), size dispersity (14%), and weight percentage of capping oleate molecules (17%) were obtained by an oleate-based solvothermal approach. The similarities among the samples permitted the interpretation of the results exclusively on the basis of the actual composition, beyond the other parameters. The temperature and magnetic field dependences of the magnetization were studied together with the interparticle interactions by DC magnetometry. Characteristic temperatures (Tmax, Tdiff, and Tb), coercivity, anisotropy field, and reduced remanence were found to be affected by the Co/Mn ratio, mainly due to the magnetic anisotropy, interparticle interactions, and particle volume distribution. In addition, the cobalt and manganese distributions were hypothesized on the basis of the chemical composition, the inversion degree obtained by 57Fe Mössbauer spectroscopy, the anisotropy constant, and the saturation magnetization

Defect-assisted synthesis of magneto-plasmonic silver-spinel ferrite heterostructures in a flower-like architecture

Artificial nano-heterostructures (NHs) with controlled morphology, obtained by combining two or more components in several possible architectures, make them suitable for a wide range of applications. Here, we propose an oleate-based solvothermal approach to design silver-spinel ferrite flower-like NHs. Small oleate-coated silver nanoparticles were used as seeds for the growth of magnetic spinel ferrite (cobalt ferrite and spinel iron oxide) nanodomains on their surface. With the aim of producing homogeneous flower-like heterostructures, a careful study of the effect of the concentration of precursors, the reaction temperature, the presence of water, and the chemical nature of the spinel ferrite was carried out. The magnetic and optical properties of the NHs were also investigated. A heterogeneous growth of the spinel ferrite phase on the silver nanoparticles, through a possible defect-assisted mechanism, was suggested in the light of the high concentration of stacking faults (intrinsic and twins) in the silver seeds, revealed by Rietveld refinement of powder X-ray diffraction patterns and High-Resolution electron microscopy

On the role of the nature and density of acid sites on mesostructured aluminosilicates dehydration catalysts for dimethyl ether production from CO2

In this work, we designed four different mesostructured acidic materials to be used as methanol dehydration catalysts for the one-pot CO2-to-DME process, in the form of physical mixtures with a Cu/ZnO/Al2O3-based commercial redox catalyst (CZA). The studied systems consist in a mesostructured gamma-Al2O3 and three mesostructured aluminosilicates (namely Al-MCM-41, Al-SBA-15, and Al-SBA-16) with the same Si/Al ratio (= 15) but significantly different textural properties. The main goal of this work is to understand how the textural features can influence the acidic properties (typology, amount, strength, surface density) and, consequently, how catalytic performances can be correlated with acidic features. On this note, we found that the systems presenting both Bronsted and Lewis sites (namely the three aluminosilicates) show much better catalytic performances than gamma-Al2O3, that only features Lewis sites, thus implying that Bronsted sites are more active towards methanol dehydration than Lewis sites. The three aluminosilicates, despite presenting comparable amounts of Bronsted sites, show significantly different performances in terms of selectivity to DME; particularly, Al-SBA-16, the system with the lowest surface area, proved to be the most efficient catalyst. This finding led us to infer that, besides Bronsted acidity, a high surface density of acid sites is a key factor to obtain a high dehydration activity; being methanol dehydration a bi-molecular reaction, the close proximity of two acid sites would indeed favor the kinetics of the process

As(III, V) Uptake from Nanostructured Iron Oxides and Oxyhydroxides: The Complex Interplay between Sorbent Surface Chemistry and Arsenic Equilibria

Iron oxides/oxyhydroxides, namely maghemite, iron oxide-silica composite, akaganeite, and ferrihydrite, are studied for AsV and AsIII removal from water in the pH range 2–8. All sorbents were characterized for their structural, morphological, textural, and surface charge properties. The same experimental conditions for the batch tests permitted a direct comparison among the sorbents, particularly between the oxyhydroxides, known to be among the most promising As-removers but hardly compared in the literature. The tests revealed akaganeite to perform better in the whole pH range for AsV (max 89 mg g−1 at pH0 3) but to be also efficient toward AsIII (max 91 mg g−1 at pH0 3– 8), for which the best sorbent was ferrihydrite (max 144 mg g−1 at pH0 8). Moreover, the study of the sorbents’ surface chemistry under contact with arsenic and arsenic-free solutions allowed the understanding of its role in the arsenic uptake through electrophoretic light scattering and pH measurements. Indeed, the sorbent’s ability to modify the starting pH was a crucial step in determining the removal of performances. The AsV initial concentration, contact time, ionic strength, and presence of competitors were also studied for akaganeite, the most promising remover, at pH0 3 and 8 to deepen the uptake mechanism