Polyelectrolyte complexes. VI. Polycation structure,polyanion molar mass,and polyion concentration effects on complex nanoparticles based on poly(sodium 2‐acrylamido‐2‐methylpropanesulfonate)

The formation and characterization of some interpolyelectrolyte complex (IPEC) nanoparticles based on poly(sodium 2‐acrylamido‐2‐methylpropanesulfonate) (NaPAMPS), as a function of the polycation structure, polyanion molar mass, and polyion concentration, were followed in this work. Poly(diallyldimethylammonium chloride) and two polycations (PCs) containing (N,N‐dimethyl‐2‐hydroxypropyleneammonium chloride) units in the backbone (PCA₅ and PCA₅D₁) were used as starting polyions. The complex stoichiometry, (n^?/n⁺)_iso, was pointed out by optical density at 500 nm (OD₅₀₀), polyelectrolyte titration, and dynamic light scattering. IPEC nanoparticle sizes were influenced by the polycation structure and polyanion molar mass only before the complex stoichiometry, which was higher for the more hydrophilic polycations (PCA₅ and PCA₅D₁) and for a higher NaPAMPS molar mass, and were almost independent of these factors after that, at a flow rate of the added polyion of about 0.28 mL × (mL PC)^?1 × h^?1. The IPEC nanoparticle sizes remained almost constant for more than 2 weeks, both before and after the complex stoichiometry, at low concentrations of polyions. NIPECs as stable colloidal dispersions with positive charges in excess were prepared at a ratio between charges (n^?/n⁺) of 0.7, and their storage colloidal stability, as a function of the polycation structure and polyion concentration (from 0.8 to ca. 7.8 mmol/L), was demonstrated. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2495–2505, 2004     

Model for the study of the impact of atmospheric heavy metals on soil microbial biomass

In the Castelporziano (Rome) protected area the inputs of atmospheric heavy metals on the soil-plant system were evaluated by the analysis of stem-flowing water from Quercus ilex L. The heavy metals detected in the soil under the canopies exhibited higher concentrations near to the tree trunks, highlighting the tree's capacity to concentrate such polluting substances. Microbial biomass, its specific respiration and the biomass calculated as a percentage of total soil organic matter, were utilised as indicators of the state of the soil and consequently also its quality with respect to heavy metal contamination.     

High-performance liquid chromatographic determination of FCE 24928, a new aromatase inhibitor, in human plasma

A sensitive and selective high-performance liquid chromatographic method for the determination of FCE 24928 (4-amino-androsta-1,4,6-triene-3, 17-dione) in human plasma is reported. The drug was extracted from buffered (pH = 8) plasma samples with methylene chloride-isooctane, then analysed by reversed-phase liquid chromatography. Quantitation was achieved by ultraviolet detection of the eluate at 238 nm. Blank plasma samples from humans, dog and rat assayed as described showed no significant peak at the retention time of the compound of interest. The suitability of the method for in vivo samples was tested by measuring the plasma levels of FCE 24928 in rats that received oral doses of the test compound.     

K18- and CAG-hACE2 Transgenic Mouse Models and SARS-CoV-2: Implications for Neurodegeneration Research

COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is a global pandemic that might lead to very serious consequences. Notably, mental status change, brain confusion, and smell and taste disorders along with neurological complaints have been reported in patients infected with SARS-CoV-2. Furthermore, human brain tissue autopsies from COVID-19 patients show the presence of SARS-CoV-2 neuroinvasion, which correlates with the manifestation of meningitis, encephalitis, leukocyte infiltration, and neuronal damage. The olfactory mucosa has been suggested as a way of entry into the brain. SARS-CoV-2 infection is also known to provoke a hyper-inflammatory reaction with an exponential increase in the production of pro-inflammatory cytokines leading to systemic responses, even in the absence of direct infection of brain cells. Angiotensin-converting enzyme 2 (ACE2), the entry receptor of SARS-CoV-2, has been extensively demonstrated to be present in the periphery, neurons, and glial cells in different brain regions. To dissect the details of neurological complications and develop therapies helping COVID-19 survivors regain pre-infection quality of life, the development of robust clinical models is highly warranted. Several human angiotensin-converting enzyme 2 (hACE2) transgenic mouse models have been developed and used for antiviral drug screening and vaccine development, as well as for better understanding of the molecular pathogenetic mechanisms of SARS-CoV-2 infection. In this review, we summarize recent results from the studies involving two such mouse models, namely K18- and CAG-hACE2 transgenics, to evaluate the direct and indirect impact of SARS-CoV-2 infection on the central nervous system.     

Synthesis and characterization of an MRI Gd‐based probe designed to target the translocator protein

DPA‐713 is the lead compound of a recently reported pyrazolo[1,5‐a]pyrimidineacetamide series, targeting the translocator protein (TSPO 18 kDa), and as such, this structure, as well as closely related derivatives, have been already successfully used as positron emission tomography radioligands. On the basis of the pharmacological core of this ligands series, a new magnetic resonance imaging probe, coded DPA‐C₆‐(Gd)DOTAMA was designed and successfully synthesized in six steps and 13% overall yield from DPA‐713. The Gd‐DOTA monoamide cage (DOTA = 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid) represents the magnetic resonance imaging reporter, which is spaced from the phenylpyrazolo[1,5‐a]pyrimidineacetamide moiety (DPA‐713 motif) by a six carbon‐atom chain. DPA‐C₆‐(Gd)DOTAMA relaxometric characterization showed the typical behavior of a small‐sized molecule (relaxivity value: 6.02 mM^?1 s^?1 at 20 MHz). The good hydrophilicity of the metal chelate makes DPA‐C₆‐(Gd)DOTAMA soluble in water, affecting thus its biodistribution with respect to the parent lipophilic DPA‐713 molecule. For this reason, it was deemed of interest to load the probe to a large carrier in order to increase its residence lifetime in blood. Whereas DPA‐C₆‐(Gd)DOTAMA binds to serum albumin with a low affinity constant, it can be entrapped into liposomes (both in the membrane and in the inner aqueous cavity). The stability of the supramolecular adduct formed by the Gd‐complex and liposomes was assessed by a competition test with albumin. Copyright © 2013 John Wiley & Sons, Ltd.     

Casorati Inequalities for Statistical Submanifolds in Kenmotsu Statistical Manifolds of Constant ϕ-Sectional Curvature with Semi-Symmetric Metric Connection

In this paper, we prove some inequalities between intrinsic and extrinsic curvature invariants, namely the normalized δ-Casorati curvatures and the scalar curvature of statistical submanifolds in Kenmotsu statistical manifolds of constant ϕ-sectional curvature that are endowed with semi-symmetric metric connection. Furthermore, we investigate the equality cases of these inequalities. We also describe an illustrative example.     

Synthesis,characterization, and cytotoxicity evaluation of high-magnetization multifunctional nanoclusters

The paper presents the synthesis, characterization, and in vitro cytotoxicity tests of Fe₃O₄ magnetic nanoclusters coated with ethylenediaminetetraacetic acid disodium salt (EDTA). Electron microscopy analysis (SEM) evidences that magnetite nanoparticles are closely packed into the clusters stabilized with EDTA with well-defined near spherical shapes and sizes in the range 100–200 nm. From XRD measurements, we determined the mean size of the crystallites inside the magnetic cluster about 36 nm. The saturation magnetization determined for the magnetic clusters stabilized with EDTA has high value, about 81.7 emu/g at 300 K. X-ray photoelectron spectroscopy has been used to determine both the elemental and chemical structure of the magnetic cluster surface. In vitro studies have shown that the magnetic clusters at low doses did not induce toxicity on human umbilical vein endothelial cells or lesions of the cell membrane. In contrast, at high doses, the magnetic clusters increased the lipid peroxidation and reduced the leakage of a cytoplasmic enzyme, lactate dehydrogenase (LDH), in parallel with increasing the antioxidant defense.

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Graphical abstract SEM images of EDTA-coated magnetic clusters (MCs) and the HUVEC viability at different MC doses

     

Continuous‐wave optical parametric oscillator based infrared spectroscopy for sensitive molecular gas sensing

Over the past 10 years, with the advent of new crystals designs and a new generation of pump lasers, continuous‐wave (cw) optical parametric oscillators (OPOs) have developed into mature monochromatic light sources. Nowadays, cw OPOs can fulfill a wide variety of criteria for sensitive molecular gas sensing. It can access the mid‐infrared wavelength region, where many molecules have their fundamental rotational‐vibrational transitions, with high power. This high power combined with wide wavelength tuning and narrow linewidth creates excellent conditions for sensitive, high‐resolution spectroscopy. OPOs combined with robust methods, such as photoacoustic spectroscopy and cavity‐enhanced spectroscopy, are well suited for field measurements and remote‐sensing applications. The wide tunability of cw OPOs allows detection of larger molecules with broad absorption band structures, and its fast scanning capabilities allow rapid detection of trace gases, the latter is a demand for life‐science applications. After a short introduction about the physical principle of cw OPOs, with its most recent physical developments, this review focuses on sensitive molecular gas sensing with a variety of spectroscopic applications in atmospheric and life sciences.     

Mechanistic investigations in α‐hydroxycarbonyls reduction by BH4‐

BH₄^‐, a well‐known and widely used reducing agent for carbonyl compounds, has been reported to have the ability to participate in dihydrogen bonding, an interaction with applications in catalysis, stereoselectivity and crystal engineering. Specifically, α‐hydroxycarbonyls are activated for reduction by dihydrogen bonding that occurs between BH₄^‐ and hydroxyl group. We explored the effect of the interaction on the mechanism of these reactions by examining their activation parameters. We found that dihydrogen bonding activates α‐hydroxycyclopentanone for reduction with NBu₄BH₄ by lowering the activation enthalpy by 6.6 kcal/mol. While the activation entropy is a significant component of the barrier, the changes resulting from the occurrence of dihydrogen bonding are manifested predominantly in the enthalpy term. Computational studies suggest that, while internal hydrogen bonding is allowed by the flexibility of the carbon backbone, that interaction is outweighed by dihydrogen bonding once BH₄^‐ is present in the system. Experimentally, a red shift of the hydroxyl frequency is observed upon addition of BH₄^‐ to the reaction mixture, suggesting a dihydrogen bonding interaction. The flexibility of the substrate's skeleton or the selectivity of the hydride sites in BH₄^‐ does not account for the lack of directing effect of the dihydrogen bonding. When a substrate with a rigid naphthalene backbone moiety, 2‐hydroxyacenaphthylen‐1(2H)‐one, is reduced, the stereochemical outcome is very similar to the one corresponding to the α‐hydroxycyclopentanone. Copyright © 2012 John Wiley & Sons, Ltd.