Positron bound systems in benzene and in naphthalene

Summary Positron decay in liquid naphthalene and benzene was investigated through measurements of lifetimes and magnetic quenching. The obtained results when compared with those already known in solid phase suggest that positrons become bound in two different systems. The first has a lifetime τ₃≈1 ns which is unaffected by the melting, while the second (τ₄≈3 ns) arises above melting and behaves as a relaxed positronium. This work was supported by CISM (Centro Interuniversitario di Struttura della Materia) del Ministero della Pubblica Istruzione, and by GNSM (Gruppo Nazionale di Struttura della Materia) del CNR.     

Evidence for strong intramolecular hydrogen bonding in some quinoline derivatives

Several analogues of quinoline-8-carboxamide were examined by ¹H NMR and IR in order to establish structural requirements for strong intramolecular hydrogen bonding.     

Volatile Compounds of Lemon and Grapefruit IntegroPectin

An HS-SPME GC-MS analysis of the volatile compounds adsorbed at the outer surface of lemon and grapefruit pectins obtained via the hydrodynamic cavitation of industrial waste streams of lemon and grapefruit peels in water suggests important new findings en route to understanding the powerful and broad biological activity of these new pectic materials. In agreement with the ultralow degree of esterification of these pectins, the high amount of highly bioactive α-terpineol and terpinen-4-ol points to limonene (and linalool) decomposition catalyzed by residual citric acid in the citrus waste peel residue of the juice industrial production.     

Discovery of Monoacylglycerol Lipase (MAGL) Inhibitors Based on a Pharmacophore-Guided Virtual Screening Study

Monoacylglycerol lipase (MAGL) is an important enzyme of the endocannabinoid system that catalyzes the degradation of the major endocannabinoid 2-arachidonoylglycerol (2-AG). MAGL is associated with pathological conditions such as pain, inflammation and neurodegenerative diseases like Parkinson’s and Alzheimer’s disease. Furthermore, elevated levels of MAGL have been found in aggressive breast, ovarian and melanoma cancer cells. Due to its different potential therapeutic implications, MAGL is considered as a promising target for drug design and the discovery of novel small-molecule MAGL inhibitors is of great interest in the medicinal chemistry field. In this context, we developed a pharmacophore-based virtual screening protocol combined with molecular docking and molecular dynamics simulations, which showed a final hit rate of 50% validating the reliability of the in silico workflow and led to the identification of two promising and structurally different reversible MAGL inhibitors, VS1 and VS2. These ligands represent a valuable starting point for structure-based hit-optimization studies aimed at identifying new potent MAGL inhibitors.     

The emergence of semantic categorization in early visual processing: ERP indices of animal vs. artifact recognition

Background

Neuroimaging and neuropsychological literature show functional dissociations in brain activity during processing of stimuli belonging to different semantic categories (e.g., animals, tools, faces, places), but little information is available about the time course of object perceptual categorization. The aim of the study was to provide information about the timing of processing stimuli from different semantic domains, without using verbal or naming paradigms, in order to observe the emergence of non-linguistic conceptual knowledge in the ventral stream visual pathway. Event related potentials (ERPs) were recorded in 18 healthy right-handed individuals as they performed a perceptual categorization task on 672 pairs of images of animals and man-made objects (i.e., artifacts).

Results

Behavioral responses to animal stimuli were ~50 ms faster and more accurate than those to artifacts. At early processing stages (120–180 ms) the right occipital-temporal cortex was more activated in response to animals than to artifacts as indexed by posterior N1 response, while frontal/central N1 (130–160) showed the opposite pattern. In the next processing stage (200–260) the response was stronger to artifacts and usable items at anterior temporal sites. The P300 component was smaller, and the central/parietal N400 component was larger to artifacts than to animals.

Conclusion

The effect of animal and artifact categorization emerged at ~150 ms over the right occipital-temporal area as a stronger response of the ventral stream to animate, homomorphic, entities with faces and legs. The larger frontal/central N1 and the subsequent temporal activation for inanimate objects might reflect the prevalence of a functional rather than perceptual representation of manipulable tools compared to animals. Late ERP effects might reflect semantic integration and cognitive updating processes. Overall, the data are compatible with a modality-specific semantic memory account, in which sensory and action-related semantic features are represented in modality-specific brain areas.     

Enzyme Conformation Influences the Performance of Lipase-powered Nanomotors

Enzyme-powered micro/nanomotors have myriads of potential applications in various areas. To efficiently reach those applications, it is necessary and critical to understand the fundamental aspects affecting the motion dynamics. Herein, we explored the impact of enzyme orientation on the performance of lipase-powered nanomotors by tuning the lipase immobilization strategies. The influence of the lipase orientation and lid conformation on substrate binding and catalysis was analyzed using molecular dynamics simulations. Besides, the motion performance indicates that the hydrophobic binding (via OTES) represents the best orienting strategy, providing 48.4 % and 95.4 % increase in diffusion coefficient compared to hydrophilic binding (via APTES) and Brownian motion (no fuel), respectively (with C_[triacetin] of 100 mm ). This work provides vital evidence for the importance of immobilization strategy and corresponding enzyme orientation for the catalytic activity and in turn, the motion performance of nanomotors, and is thus helpful to future applications.     

Highly efficient intramolecular Cannizzaro reaction between 1,3-distal formyl groups at the upper rim of a cone-calix[4]arene

The 1,3-distal cone-calix[4]arene dialdehyde 1 undergoes Cannizzaro disproportionation in the presence of strong base, but its 1,2-vicinal regioisomer 3 and the analogous monoaldehyde 2 are unreactive under the same conditions. The high intramolecular reactivity of the 1,3-distal regioisomer 1 is measured and discussed in terms of Effective Molarity (EM).     

A Simple Route to New Cyclic (Chloroalkyl)phosphane‐, Diphosphane‐, and Aminophosphane Derivatives

The reaction between benzothiadiphosphole and, in sequence, a bis‐Grignard and a chloroalkyl Grignard reagent has been reported. It produced, after treatment of the crude reaction mixture with elemental sulfur, new chloroalkyl cyclic tertiary phosphane sulfides. These compounds have been successfully employed as precursors of new nonsymmetric phosphoamino and diphosphano derivatives.     

DESI-MS<Superscript>2</Superscript>: a rapid and innovative method for trace analysis of six cytostatic drugs in health care setting

With the aim of establishing exposure levels for hospital personnel preparing and administering cytostatic drugs (CDs), here, we present an innovative screening method based on the use of the desorption electrospray ionization (DESI) interface coupled with a hybrid quadrupole linear ion trap mass spectrometer. A rapid, simple, and sensitive procedure was developed for the simultaneous surface monitoring of cyclophosphamide, dacarbazine, methotrexate, vincristine, gemcitabine, and cytarabine. Since analytes were in the solid state, a novel approach based on the use of passive samplers was combined with the direct analysis of wipes. A PTFE-printed glass slide was used as a passive sampler, while hydrophobic centers of Swiffer® cloths were judged extremely efficient as wipe samplers. After the sampling period, the CD collectors were directly processed with the DESI-MS system without any further treatment. MS/MS confirmatory analysis was conducted using selected reaction monitoring in the positive ion mode and detection limits were evaluated. Values were at the picograms per square millimeter levels on the passive collector and at the picograms per square centimeter levels for the wipe ones. Direct determination on solid-state samples combined with mass spectrometry selectivity provided a powerful tool so far unapplied to occupational hygiene.

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Figure DESI interface detail (spray emitter and MS inlet) with 3D spacefill structures of the six cytostatic drugs analyzed

     

Red Orange and Bitter Orange IntegroPectin: Structure and Main Functional Compounds

DRIFT, HPLC-MS, and SPME-GC/MS analyses were used to unveil the structure and the main functional compounds of red (blood) orange (Citrus sinensis) and bitter orange (Citrus aurantium). The IntegroPectin samples show evidence that these new citrus pectins are comprised of pectin rich in RG-I hairy regions functionalized with citrus biophenols, chiefly flavonoids and volatile molecules, mostly terpenes. Remarkably, IntegroPectin from the peel of fresh bitter oranges is the first high methoxyl citrus pectin extracted via hydrodynamic cavitation, whereas the red orange IntegroPectin is a low methoxyl pectin. C. aurantium IntegroPectin has a uniquely high concentration of adsorbed flavonoids, especially the flavanone glycosides hesperidin, naringin, and eriocitrin.