A fractional map with hidden attractors: chaos and control

The European Physical Journal Special Topics - This paper studies the dynamics of a new fractional-order map with no fixed points. Through phase plots, bifurcation diagrams, largest Lyapunov...     

Studies on the Zymogram Method for the Detection of Pectinolytic Activities Using CTAB

Zymogram analysis is a useful tool for the identification of several enzymes. The present study was undertaken to investigate the efficiency gains from the characterization of pectic enzymes on zymograms by staining of pectin-agarose overlays using cetyl trimethyl ammonium bromide also known as cetrimide or CTAB. The method is based on the fact that the enzymatic hydrolysis of the pectic substrates included in the agarose matrix gel inhibited their precipitation by CTAB, leading to the appearance of cleared zones in front of the pectin hydrolases and lyases. Conversely, esterases led to the increase of pectin precipitation. Fungal pectinolytic enzymes were separated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and subjected to the zymogram detection technique, using two pectin substances, namely citrus pectin and polygalacturonic acid. Overall, the findings presented in the current study indicate that several elements (ions, salts, pH, temperature, chelators, and reducing agents) may significantly affect the results of zymogram analysis and can, therefore, be employed to enhance the discriminatory and operational potential of the analysis in terms of accurate discrimination between several pectinolytic activities involved and effective implementation of the purification procedures required in the process.     

Competition between covalent and noncovalent bond cleavages in dissociation of phosphopeptide-amine complexes

Interactions between quaternary amino or guanidino groups with anions are ubiquitous in nature and have been extensively studied phenomenologically. However, little is known about the binding energies in non-covalent complexes containing these functional groups. Here, we present a first study focused on quantifying such interactions using complexes of phosphorylated A(3)pXA(3)-NH(2) (X = S, T, Y) peptides with decamethonium (DCM) or diaguanidinodecane (DGD) ligands as model systems. Time- and collision energy-resolved surface-induced dissociation (SID) of the singly charged complexes was examined using a specially configured Fourier transform ion cyclotron resonance mass spectrometer (FTICR-MS). Dissociation thresholds and activation energies were obtained from RRKM modeling of the experimental data that has been described and carefully characterized in our previous studies. For systems examined in this study, covalent bond cleavages resulting in phosphate abstraction by the cationic ligand are characterized by low dissociation thresholds and relatively tight transition states. In contrast, high dissociation barriers and large positive activation entropies were obtained for cleavages of non-covalent bonds. Dissociation parameters obtained from the modeling of the experimental data are in excellent agreement with the results of density functional theory (DFT) calculations. Comparison between the experimental data and theoretical calculations indicate that phosphate abstraction by the ligand is rather localized and mainly affected by the identity of the phosphorylated side chain. The hydrogen bonding in the peptide and ligand properties play a minor role in determining the energetics and dynamics of the phosphate abstraction channel.     

Sol-Gel Synthesized High Entropy Metal Oxides as High-Performance Catalysts for Electrochemical Water Oxidation

Hexanary high-entropy oxides (HEOs) were synthesized through the mechanochemical sol-gel method for electrocatalytic water oxidation reaction (WOR). As-synthesized catalysts were subjected to characterization, including X-ray diffraction (XRD), Fourier transforms infrared (FTIR) analysis, and scanning electron microscopy (SEM). All the oxide systems exhibited sharp diffraction peaks in XRD patterns indicating the defined crystal structure. Strong absorption between 400–700 cm⁻¹ in FTIR indicated the formation of metal-oxide bonds in all HEO systems. WOR was investigated via cyclic voltammetry using HEOs as electrode platforms, 1M KOH as the basic medium, and 1M methanol (CH₃OH) as the facilitator. Voltammetric profiles for both equiatomic (EHEOs) and non-equiatomic (NEHEOs) were investigated, and NEHEOs exhibited the maximum current output for WOR. Moreover, methanol addition improved the current profiles, thus leading to the electrode utility in direct methanol fuel cells as a sequential increase in methanol concentration from 1M to 2M enhanced the OER current density from 61.4 to 94.3 mA cm⁻² using NEHEO. The NEHEOs comprising a greater percentage of Al, ([Al_0.35(Mg, Fe, Cu, Ni, Co)_0.65]₃O₄) displayed high WOR catalytic performance with the maximum diffusion coefficient, D° (10.90 cm² s⁻¹) and heterogeneous rate constant, k° (7.98 cm s⁻¹) values. These primary findings from the EC processes for WOR provide the foundation for their applications in high-energy devices. Conclusively, HEOs are proven as novel and efficient catalytic platforms for electrochemical water oxidation.     

Improved Method for Preparation of 3-(1H-Indol-3-yl)benzofuran-2(3H)-ones

3-(1H-Indol-3-yl)benzofuran-2(3H)-ones were efficiently accessed via polyphosphoric acid-mediated condensation of 3-(2-nitrovinyl)-1H-indoles with phenols.     

Surface modification of resorcinarene based self-assembled solid lipid nanoparticles for drug targeting

Prolyl-bearing amphiphilic resorcinarenes, e.g. tetrakis(N-methylprolyl)tetraundecylcalix[4]resorcinarene, self-assemble as stable solid lipid nanoparticles; these fully characterized systems could be further functionalized at their surface with proteins, and interact with specific antibodies bound on a sensor surface.     

In vitro cytotoxicity of some Narcissus plants extracts

This study compares the chloroform extracts of bulbs and roots of Narcissus papyraceus Ker Gawl. and Narcissus tazetta L. The cytotoxicity of the plant extracts was evaluated against human hepatocellular carcinoma cell line (HEPG2) and colon carcinoma cell line (HCT116) in comparison to doxorubicin. The extracts from the after-flowering (AF) bulbs of N. tazetta L. and N. papyraceus exhibited strong cytotoxic activity against HEPG2 (IC₅₀: 2.2, 3.5 μg mL^? 1) and HCT116 (IC₅₀: 4.2, 3.9 μg mL^? 1) cell lines, respectively. N. tazetta L. bulbs exhibited the least cell viability percentage in HepG-2 cell line (5.32%), while the AF root extracts of N. papyraceus exhibited the least cell viability percentage in HCT116 cell line (4.93%), when applied at a concentration of 50 μg mL^? 1, thereby being more active than doxorubicin at the same concentration.     

Colorimetric determination of some important hydrazine derivatives

A simple and rapid colorimetric method for the determination of isoniazid, isocarboxazid, iproniazid phosphate, phenelzine sulphate and phenylhydrazine hydrochloride is described. The method is based on the formation of ferroin, when the studied drugs react with a mixture of iron (III) and 1,10-phenanthroline, and measurement of the absorbance at 512 nm. The procedure has been successfully applied to the assay of the pharmaceutical preparations of the studied drugs and the results are favorably comparable to the official methods.