Copper speciation in aqueous solutions of fulvic acid and related molecular weight distributions

Potentiometric and fluorescence measurements of aqueous solutions of fulvic acid containing Cu(NO₃)₂ or Cu(ClO₄)₂, respectively, were carried out at 25?°C and pH 5.5 to determine naturally occurring Cu species. The fulvic acid used was isolated by XAD-8 from filtrated (0.3 μm) water of a peat bog in the Dachauer Moos near Munich. From the results an operational molecular weight of fulvic acid of about 750 g/ mol was estimated, which was confirmed by molecular weight distributions determined by high-performance size-exclusion chromatography (HPSEC), gel permeation chromatography (GPC) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Using this molecular weight and assuming that mainly 1:1 Cu-fulvic acid complexes are formed, a conditional stability constant of the Cu-fulvic acid complex of 10^5.9 could be calculated. These data are essential for the assessment of organic carrier-mediated migration of Cu as well as of the toxicological risk potential of Cu in aqueous environment and can be used as input parameters for geochemical modeling of the Cu species distribution in aqueous solutions.     

Plasma Bead Entrapped Liposomes as a Potential Drug Delivery System to Combat Fungal Infections

Fibrin-based systems offer promises in drug and gene delivery as well as tissue engineering. We established earlier a fibrin-based plasma beads (PB) system as an efficient carrier of drugs and antigens. In the present work, attempts were made to further improve its therapeutic efficacy exploiting innovative ideas, including the use of plasma alginate composite matrices, proteolytic inhibitors, cross linkers, and dual entrapment in various liposomal formulations. In vitro efficacy of the different formulations was examined. Pharmacokinetics of the formulations encapsulating Amphotericin B (AmpB), an antifungal compound, were investigated in Swiss albino mice. While administration of the free AmpB led to its rapid elimination (<72 h), PB/liposome-PB systems were significantly effective in sustaining AmpB release in the circulation (>144 h) and its gradual accumulation in the vital organs, also compared to the liposomal formulations alone. Interestingly, the slow release of AmpB from PB was unusual compared to other small molecules in our earlier findings, suggesting strong interaction with plasma proteins. Molecular interaction studies of bovine serum albumin constituting approximately 60% of plasma with AmpB using isothermal titration calorimetry and in silico docking verify these interactions, explaining the slow release of AmpB entrapped in PB alone. The above findings suggest that PB/liposome-PB could be used as safe and effective delivery systems to combat fungal infections in humans.     

Pell-type equations and class number of the maximal real subfield of a cyclotomic field

We investigate the solvability of the Diophantine equation \(x^2-my^2=\pm p\) in integers for certain integer m and prime p. Then we apply these results to produce family of maximal real subfield of a cyclotomic field whose class number is strictly larger than 1.     

Concept of Ir-catalyzed CH bond activation/borylation by noncovalent interaction

Noncovalent interactions play a fundamental role in molecular biology, crystal engineering, supramolecular chemistry, drug design, sensing applications, and many other research fields in the chemical sciences. Because of this importance, thorough research efforts have been focused on the interpreting and quantifying these interactions, which include H-bonding, electrostatic effects, ππ interaction, cation-π interaction, hydrophobic-hydrophobic interaction, van der Waals forces, and other such type of interactions. However, on the synthetic standpoint, use of these noncovalent interactions are rare, although might be beneficial for the site-selective CH bond activation and functionalization by transition metal catalysis. In this context, iridium-catalyzed CH borylation has gained immense popularity due to the versatility conferred to the CB bonds. Very recently, researchers have started employing these interactions as a governing factor for attaining regioselectivity in arene CH borylation. In this perspective, we will focus on the advancements made so far by the use of various noncovalent interactions in Ir-catalyzed borylations.     

Fe2O3 nanoparticles dispersed unsaturated polyester resin based nanocomposites: effect of gamma radiation on mechanical properties

ABSTRACT

In this work, unsaturated polyester resin (UPR) matrix based nanocomposite was fabricated using synthesized Fe₂O₃ nanoparticle as reinforcement and methyl ethyl ketone peroxide as curing agent by solution casting method. The Fe₂O₃ nanoparticles were synthesized using the sol–gel method and the formation of nanoparticle was confirmed by X-ray diffraction, Scanning electron microscope, Energy dispersive spectrometry analysis. Interactions between metal oxide nanoparticles and polymer molecules in fabricated nanocomposite were investigated by Fourier transform infrared spectrometer analysis. Pure UPR and Fe₂O₃/UPR composite were irradiated with various gamma radiation doses (0–15?kGy). At the 0?kGy (without radiation), the nanoparticles loaded composite showed better mechanical properties (increased in tensile strength and Young’s modulus and decreased in elongation) compared to that of pure UPR sheet. At the 5?kGy radiation dose, the tensile strength and Young’s modulus were further increased; whereas, the elongation was decreased in both samples.     

Detailed study of ultra-soft magnetic properties of Fe74Cu0.8Nb2.7Si15.5B7

The magnetic properties of nanocrystalline Fe₇₄Cu_0.8Nb_2.7Si_15.5B₇ alloy, which were rapidly solidified and then annealed at various temperatures between 475 and 650°C for different holding time, have been studied. Grain size, silicon content and the lattice parameter of α-Fe(Si) nanograins at the annealing temperatures were determined. Curie temperature of the amorphous phase was determined from the temperature dependence of permeability. For higher annealing temperatures and times, some Si diffused out of the α-Fe(Si) phase and formed an ordered DO₃ phase of Fe₃Si. This changed the overall magnetostriction and average anisotropy of the matrix, which deteriorated the magnetic softness of the material at higher annealing temperatures. Ultra-soft magnetic properties were achieved by averaging the random anisotropy via exchange interaction. Hysteresis loops for samples in as-cast and annealed conditions have also been studied.     

Physico-chemical Investigation of Mixed Micelle Formation Between Tetradecyltrimethylammonium Bromide and Dodecyltrimethylammonium Chloride in Water and Aqueous Solutions of Sodium Chloride

Conductometric measurements have been employed to gain a detailed insight into the interactions between two cationic surfactants, tetradecyltrimethylammonium bromide (TTAB) and dodecyltrimethylammonium chloride (DTAC), in water and in an aqueous solution of sodium chloride. The experimental data were analyzed according to Rubingh’s model within the framework of the pseudophase separation model. The evaluated values of critical micelle concentration (cmc) were found to be lower than their corresponding cmc ^id values, signifying attractive interactions involving both components in the solutions. The micellar mole fractions (\( X_{1}^{\text{Rub}} \)) of TTAB evaluated by Rubingh’s model were always larger than the ideal values (\( X_{1}^{\text{id}} \)), signifying the higher involvement of TTAB in mixed micelles of TTAB and DTAC. Activity coefficients (\( f_{ 1}^{\text{Rub}} \) and \( f_{ 2}^{\text{Rub}} \)) were always below one in all cases signifying synergism in the mixed micelles. All the outcomes point to synergism and attractive interactions in the mixed systems. Values of excess Gibbs energy were evaluated by employing Rubingh’s model (\( \Delta G_{\text{ex}}^{\text{Rub}} \)) and the \( \Delta G_{\text{ex}}^{\text{Rub}} \) values obtained are negative. The values of \( \Delta H_{\text{m}}^{\text{o}} \) and \( \Delta S_{\text{m}}^{\text{o}} \) reveal that hydrophobic interaction is expected to be the binding force between TTAB and DTAC in aqueous media at lower temperatures, while both hydrophobic interactions as well as exothermic interactions are involved at higher temperatures. The interaction forces between the surfactants were found to be enhanced in the presence of NaCl.     

Palladium‐catalyzed cyclization of 2‐alkynyl‐N‐ethanoyl anilines to indoles: synthesis,structural, spectroscopic,and mechanistic study

This study reports a facial regio‐selective synthesis of 2‐alkyl‐N‐ethanoyl indoles from substituted‐N‐ethanoyl anilines employing palladium (II) chloride, which acts as a cyclization catalyst. The mechanistic trait of palladium‐based cyclization is also explored by employing density functional theory. In a two‐step mechanism, the palladium, which attaches to the ethylene carbons, promotes the proton transfer and cyclization. The gas‐phase barrier height of the first transition state is 37 kcal/mol, indicating the rate‐determining step of this reaction. Incorporating acetonitrile through the solvation model on density solvation model reduces the barrier height to 31 kcal/mol. In the presence of solvent, the electron‐releasing (–CH₃) group has a greater influence on the reduction of the barrier height compared with the electron‐withdrawing group (–Cl). These results further confirm that solvent plays an important role on palladium‐catalyzed proton transfer and cyclization. For unveiling structural, spectroscopic, and photophysical properties, experimental and computational studies are also performed. Thermodynamic analysis discloses that these reactions are exothermic. The highest occupied molecular orbital?lowest unoccupied molecular orbital gap (4.9–5.0 eV) confirms that these compounds are more chemically reactive than indole. The calculated UV–Vis spectra by time‐dependent density functional theory exhibit strong peaks at 290, 246, and 232 nm, in good agreement with the experimental results. Moreover, experimental and computed ¹H and ¹³C NMR chemical shifts of the indole derivatives are well correlated. Copyright © 2015 John Wiley & Sons, Ltd.