A spectrophotometric assay of folic acid concentrations in rats: correlations with age and organ

Spectrophotometric assays have been used to determine FA concentration in tissue homogenates from various organs (liver, kidneys, brain, spleen) in white rats; these studies were undertaken to test the age--and organ--dependent variations of FA concentrations in tissue homogenates. The results showed a marked decrease of FA concentration in the adult group of rats when related to the young group, and in the aged group when compared to the adults respectively. Analysing the determined values of folates in tissue homogenates of various organs (in rats belonging to the same group of age), the highest concentration has been found in the liver homogenate, followed in decreasing order by kidneys and to a much greater distance, by the brain and spleen.     

Anticancer Potential of Betulonic Acid Derivatives

Clinical trials have evidenced that several natural compounds, belonging to the phytochemical classes of alkaloids, terpenes, phenols and flavonoids, are effective for the management of various types of cancer. Latest research has proven that natural products and their semisynthetic variants may serve as a starting point for new drug candidates with a diversity of biological and pharmacological activities, designed to improve bioavailability, overcome cellular resistance, and enhance therapeutic efficacy. This review was designed to bring an update regarding the anticancer potential of betulonic acid and its semisynthetic derivatives. Chemical derivative structures of betulonic acid including amide, thiol, and piperidine groups, exert an amplification of the in vitro anticancer potential of betulonic acid. With the need for more mechanistic and in vivo data, some derivatives of betulonic acids may represent promising anticancer agents.     

Influence of Various Albumin Concentrations on the Corrosion Resistance of Zr-2.5%Nb Alloy

The Zr-2.5% Nb alloy corrosion resistance in four saline solutions with and without albumin was tested through electrochemical measurements of electrochemical impedance spectroscopy (EIS), linear polarization, and cyclic voltammetry at human body temperature.

The EIS measurements were performed at open circuit potential. The impedance spectra were recorded and the equivalent electric circuits were elaborated. From the linear polarization the Tafel slopes were recorded and the corrosion parameters were calculated. From the potentiodynamic polarization curves, the breakdown potential, the protection potential, and the protection domain were observed.

The amount of ions released from the material was quantified using the ICPMS technique and the results concerning the corrosion resistance were compared with those obtained from linear and cyclic polarization.

Before and after potentiodynamic polarization the topographic measurements were performed; the roughness at the samples surface was observed using AFM. The roughness was co-related to the contact angle measurements.     

Influence of triphenylphosphonium pendant groups on the rheological and morphological properties of new quaternized polysulfone

A new quaternized polysulfone with triphenylphosphonium pendant groups was synthesized by reacting chloromethylated polysulfone with triphenylphosphine. The molecular restructurations, generated by hydrogen bonding, electrostatic interactions, and association phenomena in ternary quaternized polysulfone/N,N‐dimethylformamide (solvent)/water (nonsolvent) systems, were evaluated by rheological investigations. The polyelectrolyte effect, induced by enhanced dissociation of the ionizable groups and by mixed solvents' quality, modify the rheological functions, that is, dynamic viscosity, elastic shear modulus, and viscous shear modulus, as well as the thermodynamic parameters obtained from the rheological properties, such as apparent activation energy. These results were correlated with the morphological properties of the films obtained from solutions in solvent/nonsolvent mixtures and compared with other quaternized polysulfones, having different hydrophobic characteristics. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthetic Approaches of Epoxysuccinate Chemical Probes

Synthetic chemical probes are powerful tools for investigating biological processes. They are particularly useful for proteomic studies such as activity-based protein profiling (ABPP). These chemical methods initially used mimics of natural substrates. As the techniques gained prominence, more and more elaborate chemical probes with increased specificity towards given enzyme/protein families and amenability to various reaction conditions were used. Among the chemical probes, peptidyl-epoxysuccinates represent one of the first types of compounds used to investigate the activity of the cysteine protease papain-like family of enzymes. Structurally derived from the natural substrate, a wide body of inhibitors and activity- or affinity-based probes bearing the electrophilic oxirane unit for covalent labeling of active enzymes now exists. Herein, we review the literature regarding the synthetic approaches to epoxysuccinate-based chemical probes together with their reported applications, from biological chemistry and inhibition studies to supramolecular chemistry and the formation of protein arrays.     

Study of the conversion of aromatic hydrocarbons on EMT-type zeolite: Influence of the partial substitution of Al by Ga

(Al,Ga)EMT-type zeolites (Al:Ga = 1:0, 0.75:0.25 and 0.5:0.5) were prepared and tested as catalysts in the gas-phase toluene–methanol alkylation and toluene–trimethylbenzene transalkylation. Various techniques including XRD, N₂ sorption, MAS NMR and SEM were used to monitor the physico-chemical properties of these solids. The results revealed a high purity and crystallinity of the materials, and that the Ga atoms are entirely incorporated into the framework. The ammonia TPD measurements indicated that the isomorphous substitution of aluminium by gallium leads to a decrease of both acidic strength and acid sites concentration. The catalytic performances of the EMT-type solids in the conversion of methylaromatic hydrocarbons were correlated with their acid properties. Thus, the less acidic (Al,Ga)EMT samples exhibited a lower activity, but a higher selectivity towards the xylenes formation by comparison with (Al)EMT.     

Nanostructured quaternary Ni1-xCuxFe2-yCeyO4 complex system: Cerium content and copper substitution dependence of cation distribution and magnetic-electric properties in spinel ferrites

Quaternary Ni_1-xCu_xFe_2-yCe_yO₄ complex nano-ferrites system with different cerium content ratio and copper substitution degree were synthesized via co-precipitation wet chemical technique. The newly obtained nanoparticles, with general formula Ni_1-xCu_xFe_2-yCe_yO₄ (where x = 0.0, 0.3, 0.6 and y = 0.00, 0.03, 0.05, 0.08 and 0.10) were heated up to 600 °C to stabilize the specific crystalline spinel structure. The limit of cerium content was quantitively determined to be around 0.08 and up to 0.10. Furthermore, the powders were pelletized in a 13 mm wide pellets and thermally treated at 950 °C. The thermal treatment affected even more the phases segregation process, as CeO₂ was identified in the sample with lowest degree of cerium insertion – 0.03. Also, a difference in color and size of pelletized samples was noticed after the 950 °C thermal treatment. The Rietveld refinement, crystal structure confirmation, morphology magnetic and electrical properties of samples have been deeply studied. The cation distribution carried out from Rietveld refinement confirms the occupancy of (Fe³⁺) on tetrahedral sites and [Ni²⁺], [Cu²⁺], [Fe³⁺] and [Ce²⁺] on octahedral sites in the crystal lattice. Preliminary information regarding the cation distribution in spinel structures were suggested by FTIR spectral results, precisely in the 650-520 cm^?1 region, as a consequence of peak shape and lack of shiftiness of M^Td – O bond. Spherical-shaped quaternary nano-ferrites of 17–28 nm were determined from FE-SEM analysis and the samples composition was confirmed by EDX analysis. Hysteresis loops shows modifications in coercivity, magnetization and magnetic remanence with Ni²⁺ and Cu²⁺ ions doping in Ni_1-xCu_xFe_2-yCe_yO₄ complex systems with typical ferrimagnetic behavior. Dielectric measurements were employed in order to determine the electrical permittivity, dielectric losses and conductivity values in a 10 Hz – 1 MHz frequency range.     

Lyapunov–Krasovskii functionals and application to input delay compensation for linear time-invariant systems

For linear systems with pointwise or distributed delay in the inputs which are stabilized through the reduction approach, we propose a new technique of construction of Lyapunov–Krasovskii functionals. These functionals allow us to establish the ISS property of the closed-loop systems relative to additive disturbances.     

Luminescence,Paramagnetic, and Electrochemical Properties of Copper Oxides-Decorated TiO2/Graphene Oxide Nanocomposites

The properties of newly synthesized Cu₂O/CuO-decorated TiO₂/graphene oxide (GO) nanocomposites (NC) were analyzed aiming to obtain insight into their photocatalytic behavior and their various applications, including water remediation, self-cleaning surfaces, antibacterial materials, and electrochemical sensors. The physico-chemical methods of research were photoluminescence (PL), electron paramagnetic resonance (EPR) spectroscopy, cyclic voltammetry (CV), and differential pulse voltammetry (DPV). The solid samples evidenced an EPR signal that can be attributed to the oxygen-vacancy defects and copper ions in correlation with PL results. Free radicals generated before and after UV-Vis irradiation of powders and aqueous dispersions of Cu₂O/CuO-decorated TiO₂/GO nanocomposites were studied by EPR spectroscopy using two spin traps, DMPO (5,5-dimethyl-1-pyrroline-N-oxide) and CPH (1-hydroxy-3-carboxy-2,2,5,5-tetramethylpyrrolidine), to highlight the formation of hydroxyl and superoxide reactive oxygen species, respectively. The electrochemical characterization of the NC modified carbon-paste electrodes (CPE) was carried out by CV and DPV. As such, modified carbon-paste electrodes were prepared by mixing carbon paste with copper oxides-decorated TiO₂/GO nanocomposites. We have shown that GO reduces the recombination process in TiO₂ by immediate electron transfer from excited TiO₂ to GO sheets. The results suggest that differences in the PL, respectively, EPR data and electrochemical behavior, are due to the different copper oxides and GO content, presenting new perspectives of materials functionalization.     

Current and Emerging Approaches for Spine Tumor Treatment

Spine tumors represent a significant social and medical problem, affecting the quality of life of thousands of patients and imposing a burden on healthcare systems worldwide. Encompassing a wide range of diseases, spine tumors require prompt multidisciplinary treatment strategies, being mainly approached through chemotherapy, radiotherapy, and surgical interventions, either alone or in various combinations. However, these conventional tactics exhibit a series of drawbacks (e.g., multidrug resistance, tumor recurrence, systemic adverse effects, invasiveness, formation of large bone defects) which limit their application and efficacy. Therefore, recent research focused on finding better treatment alternatives by utilizing modern technologies to overcome the challenges associated with conventional treatments. In this context, the present paper aims to describe the types of spine tumors and the most common current treatment alternatives, further detailing the recent developments in anticancer nanoformulations, personalized implants, and enhanced surgical techniques.