Chiral bidiaziridines by a two-step domino aziridination of meso-α-diimines

Chiral racemic α-diimines, tested in aziridination reactions with NsONHCO₂Et, for the first time led to the synthesis of (±)-bidiaziridines, stereoselectively derived from the corresponding meso (E-s-trans-E)-α-diimines. Moreover, a minor bidiaziridine isomer, probably a meso form that was lost under classical work-up conditions, can be obtained by adding water to the crude mixtures at the end of amination reactions. The results definitively prove that the imine aziridination by carbamates is a two-step domino process. The structures of the compounds were determined using 2D NMR on purified bidiaziridines.     

Multivariate optimization of a headspace solid‐phase microextraction method followed by gas chromatography with mass spectrometry for the determination of terpenes in Nicotiana langsdorffii

A simple and sensitive procedure based on headspace solid‐phase microextraction and gas chromatography with mass spectrometry was developed for the determination of five terpenes (α‐pinene, limonene, linalool, α‐terpineol, and geraniol) in the leaves of Nicotiana langsdorffii. The microextraction conditions (extraction temperature, equilibration time, and extraction time) were optimized by means of a Doehlert design. The experimental design showed that, for α‐pinene and limonene, a low temperature and a long extraction time were needed for optimal extraction, while linalool, α‐terpineol, and geraniol required a high temperature and a long extraction time. The chosen compromise conditions were temperature 60°C, equilibration time 15 min and extraction time 50 min. The main analytical figures of the optimized method were evaluated; LODs ranged from 0.07 ng/g (α‐pinene) to 8.0 ng/g (geraniol), while intraday and interday repeatability were in the range 10–17% and 9–13%, respectively. Finally, the procedure was applied to in vitro wild‐type and transgenic specimens of N. langsdorffii subjected to abiotic stresses (chemical and heat stress). With the exception of geraniol (75–374 ng/g), low concentration levels of terpenes were measured (ng/g level or lower); some interesting variations in terpene concentration induced by abiotic stress were observed.     

Polyaspartamide–Polylactide Graft Copolymers with Tunable Properties for the Realization of Fluorescent Nanoparticles for Imaging

Here, the synthesis and the characterization of novel amphiphilic graft copolymers with tunable properties, useful in obtaining polymeric fluorescent nanoparticles for application in imaging, are described. These copolymers are obtained by chemical conjugation of rhodamine B (RhB) moieties, polylactic acid (PLA), and O‐(2‐aminoethyl)‐O′‐methyl poly(ethylene glycol) (PEG) on α,β‐poly(N‐2‐hydroxyethyl)‐d,l ‐aspartamide (PHEA). In particular, PHEA is first functionalized with RhB to obtain PHEA–RhB with a derivatization degree in RhB (DD_RhB) equal to 0.55 mol%. By varying the reaction conditions, different amounts of PLA are grafted on PHEA–RhB to obtain PHEA‐RhB‐PLA with DD_PLA equal to 1.9, 4.0, and 6.2 mol%. Then, PEG chains are grafted on PHEA‐RhB‐PLA derivatives to obtain PHEA‐RhB‐PLA‐PEG graft copolymers. The preparation of polymeric fluorescent nanoparticles with tunable properties and spherical shape is described by using PHEA‐RhB‐PLA‐PEG with DD in PLA and PEG equal to 4.0 and 4.9 mol%, by following easily scaling up processes, such as emulsion‐solvent evaporation and high pressure homogenization (HPH)‐solvent evaporation techniques.

     

Development of New Targeted Inulin Complex Nanoaggregates for siRNA Delivery in Antitumor Therapy

Here, a novel strategy of formulating efficient polymeric carriers based on the already described INU-IMI-DETA for gene material whose structural, functional, and biological properties can be modulated and improved was successfully investigated. In particular, two novel derivatives of INU-IMI-DETA graft copolymer were synthesized by chemical functionalisation with epidermal growth factor (EGF) or polyethylenglycol (PEG), named INU-IMI-DETA-EGF and INU-IMI-DETA-PEG, respectively, in order to improve the performance of already described “inulin complex nanoaggregates” (ICONs). The latter were thus prepared by appropriately mixing the two copolymers, by varying each component from 0 to 100 wt% on the total mixture, named EP-ICONs. It was seen that the ability of the INU-IMI-DETA-EGF/INU-IMI-DETA-PEG polymeric mixture to complex siGL3 increases with the increase in the EGF-based component in the EP-ICONs and, for each sample, with the increase in the copolymer:siRNA weight ratio (R). On the other hand, the susceptibility of loaded siRNA towards RNase decreases with the increase in the pegylated component in the polymeric mixture. At all R values, the average size and the zeta potential values are suitable for escaping from the RES system and suitable for prolonged intravenous circulation. By means of biological characterisation, it was shown that MCF-7 cells are able to internalize mainly the siRNA-loaded into EGF-decorated complexes, with a significant difference from ICONs, confirming its targeting function. The targeting effect of EGF on EP-ICONs was further demonstrated by a competitive cell uptake study, i.e., after cell pre-treatment with EGF. Finally, it was shown that the complexes containing both EGF and PEG are capable of promoting the internalisation and therefore the transfection of siSUR, a siRNA acting against surviving mRNA, and to increase the sensitivity to an anticancer agent, such as doxorubicin.     

Laquinimod Modulates Human Astrocyte Function and Dampens Astrocyte-Induced Neurotoxicity during Inflammation

Astrocytes greatly participate to inflammatory and neurotoxic reactions occurring in neurodegenerative diseases and are valuable pharmacological targets to support neuroprotection. Here we used human astrocytes generated from reprogrammed fibroblasts as a cellular model to study the effect of the compound Laquinimod and its active metabolite de-Laquinimod on astrocyte functions and the astrocyte–neuron interaction. We show that human iAstrocytes expressed the receptor for the inflammatory mediator IL1 and responded to it via nuclear translocation of NFκB, an event that did not occur if cells were treated with Laquinimod, indicating a direct anti-inflammatory activity of the drug on the human astrocyte. Similarly, while exposure to IL1 downregulated glial glutamate transporters GLAST and GLT1, treatment with Laquinimod supported maintenance of physiological levels of these proteins despite the inflammatory milieu. Laquinimod also induced nuclear translocation of the aryl hydrocarbon receptor (AHR), suggesting that drug action was mediated by activation of the AHR pathway. However, the drug was effective despite AHR inhibition via CH223191, indicating that AHR signaling in the astrocyte is dispensable for drug responses. Finally, in vitro experiments with rat spinal neurons showed that laquinimod did not exert neuroprotection directly on the neuron but dampened astrocyte-induced neurodegeneration. Our findings indicate that fibroblast-derived human astrocytes represent a suitable model to study astrocyte–neuron crosstalk and demonstrate indirect, partial neuroprotective efficacy for laquinimod.     

The Sound of Silence: Minorities,Abstention and Democracy

Despite the existence of an extensive literature, no definitive conclusion seems to emerge on the extent to which minorities are guaranteed by democratic rules in political systems. This paper contributes to this debate by proposing a modified Heigselmann and Krauss two-dimensional model of preferences in order to capture the role of abstention on minority representativeness. Regardless of the typology of abstention, simulation results show that voter abstention always benefits minorities.     

UV spectra and excitation delocalization in DNA: influence of the spectral width.

The singlet excited states of the model DNA duplex (dA)10.(dT)10 are studied. Calculations are performed in the exciton theory framework. Molecular dynamics calculations provide the duplex geometry. The dipolar coupling is determined using atomic transition charges. The monomer transition energies are simulated by Gaussian functions resembling the absorption bands of nucleosides in aqueous solutions. Most of the excited states are found to be delocalized over at least two bases and result from the mixing of different monomer states. Their properties are only weakly affected by conformational changes of the double helix. On average, the highest oscillator strength is carried by the upper eigenstates. The duplex absorption spectra are shifted a few nanometers to higher energies with respect to the spectra of noninteracting monomers. The states with larger spatial extent are located close to the maximum of the absorption spectrum.     

Interaction of Candida parapsilosis isolates with human hair and nail surfaces revealed by scanning electron microscopy analysis

Candida parapsilosis is found frequently as commensal organism on epithelial tissues, and is also an increasing cause of nosocomial infection. Scanning electron microscope (SEM) observations were used to analyse the capability of C. parapsilosis cells to adhere and grow as biofilm on human natural substrates and to compare the adherence pattern of isolates exhibiting distinct phenotypes. Cells from the crepe phenotype are predominantly elongated and form pseudohyphae whereas cells from the smooth phenotype are yeast-shaped, either in liquid cultures or on human nail and hair surfaces. The electron micrographs revealed that C. parapsilosis cells from the smooth phenotype adhered in higher number to both surfaces compared to the observed for the crepe phenotype. SEM analysis of human hair surface revealed that cells from the smooth phenotype appear as clumped blastoconidia of uniform morphology embedded in a flocculent extracellular material forming biofilm. The extracellular material and biofilm were seeing in a less extension in the crepe phenotype. A distinct adherence pattern was observed when human nail was used as substrate. Here C. parapsilosis cells seem to be linked to surface structures of human nail plate. Fibrillar extracellular material was observed connecting neighbouring cells as well as nail surface.     

Liquid-liquid phase separation of a surfactant-solubilized membrane protein

Solubilization of membrane proteins requires surfactants, whose structural properties play a crucial role in determining the protein phase behavior. We show that ionization of a pH-sensitive surfactant, lauryldymethylamino-N-oxide, bound to the bacterial photosynthetic Reaction Center, induces protein phase segregation in micrometric "droplets." Liquid-liquid phase separation takes place in a narrow pH range, is promoted by increasing temperature, and vanishes by adding salt. After a fast initial droplet growth, the nearly arrested kinetics at a later stage leaves the system in a finely divided, long-lasting emulsified state.