Influence of V2O5 on the magnetic properties of nickel–zinc–copper ferrites

Additions of V₂O₅ were used to decrease the sintering temperature and to enhance the densification of NiZnCu ferrite. With a small amount of V₂O₅ (0.6–1.2 wt%) as a sintering aid, densification at low sintering temperature was observed. EDS analyses showed the presence of vanadium inside the ferrite grains. Microstructure investigation revealed heterogeneous grain size. Magnetic properties were deteriorated when increasing the V₂O₅ content. As a consequence, the permeability decreased and the core losses increased, which can be explained by the pinning of the domain walls to the grain defects.     

FTIR and Raman analysis of l‐cysteine ethyl ester HCl interaction with dipalmitoylphosphatidylcholine in anhydrous and hydrated states

Interactions of l ‐cysteine ethyl ester hydrochloride (CE), a bioactive cysteine derivative, with dipalmitoylphosphatidylcholine (DPPC) were investigated. To gain a deeper insight into analyzing l ‐cysteine ethyl ester HCl interaction with liposomes of DPPC in anhydrous and hydrated states, we performed experimental studies by infrared (Fourier transform infrared spectroscopy) and Raman spectroscopies. The results revealed that the interaction of CE with the phospholipid head groups was the same in absence or presence of water. In both states, the wavenumber of the PO₂⁻ group and C N bond of the choline group decreased. This behavior can be ascribed to the replacement of hydration water and binding to the phosphate group. In the Raman spectrum results for the anhydrous and gel states, the S H stretching band of the CE shifted to lower frequencies with a decrease in its force constant. Biologically active lipophilic molecules such as CE should be studied in terms of their interaction with lipid bilayers prior to the development of advanced lipid carrier systems such as liposomes. The results of these studies provide information on membrane integrity and physicochemical properties that are essential for the rational design of lipidic drug delivery systems. Copyright © 2015 John Wiley & Sons, Ltd.     

A molecularly imprinted polymer for the determination of neopterin

A molecularly imprinted polymer (MIP) for the specific retention of neopterin has been developed. A set of 6 polymers was prepared by radical polymerization under different experimental condition using methacrylic acid as functional monomer and ethylene glycol dimethacrylate as crosslinker, with the aim to understand their influence on the efficiency of the MIP. The performance of each MIP was tested in batch experiments via their binding capacity. The MIP prepared in the presence of nickel ions in dimethylsulfoxide-acetonitrile mixture (P4) exhibited the highest binding capacity for neopterin (260 μmol per gram of polymer). A selectivity study with two other pteridines demonstrated the polymer P4 also to possess the best selectivity.

A molecularly imprinted polymer for the specific retention of neopterin was developed. A set of 6 polymers was prepared under different experimental condition. The performance of each MIP was tested through their binding capacity. The MIP P4 prepared in the presence of nickel ions exhibited the highest binding capacity

     

Radical C−N Borylation of Aromatic Amines Enabled by a Pyrylium Reagent

Herein, we report a radical borylation of aromatic amines through a homolytic C(sp²)−N bond cleavage. This method capitalizes on a simple and mild activation via a pyrylium reagent (^ScPyry-OTf) thus priming the amino group for reactivity. The combination of terpyridine and a diboron reagent triggers a radical reaction which cleaves the C(sp²)−N bond and forges a new C(sp²)−B bond. The unique non-planar structure of the pyridinium intermediate, provides the necessary driving force for the aryl radical formation. The method permits borylation of a wide variety of aromatic amines indistinctively of the electronic environment.     

Diversity of Neuropeptide Cell-Cell Signaling Molecules Generated by Proteolytic Processing Revealed by Neuropeptidomics Mass Spectrometry

Neuropeptides are short peptides in the range of 3–40 residues that are secreted for cell-cell communication in neuroendocrine systems. In the nervous system, neuropeptides comprise the largest group of neurotransmitters. In the endocrine system, neuropeptides function as peptide hormones to coordinate intercellular signaling among target physiological systems. The diversity of neuropeptide functions is defined by their distinct primary sequences, peptide lengths, proteolytic processing of pro-neuropeptide precursors, and covalent modifications. Global, untargeted neuropeptidomics mass spectrometry is advantageous for defining the structural features of the thousands to tens of thousands of neuropeptides present in biological systems. Defining neuropeptide structures is the basis for defining the proteolytic processing pathways that convert pro-neuropeptides into active peptides. Neuropeptidomics has revealed that processing of pro-neuropeptides occurs at paired basic residues sites, and at non-basic residue sites. Processing results in neuropeptides with known functions and generates novel peptides representing intervening peptide domains flanked by dibasic residue processing sites, identified by neuropeptidomics. While very short peptide products of 2–4 residues are predicted from pro-neuropeptide dibasic processing sites, such peptides have not been readily identified; therefore, it will be logical to utilize metabolomics to identify very short peptides with neuropeptidomics in future studies. Proteolytic processing is accompanied by covalent post-translational modifications (PTMs) of neuropeptides comprising C-terminal amidation, N-terminal pyroglutamate, disulfide bonds, phosphorylation, sulfation, acetylation, glycosylation, and others. Neuropeptidomics can define PTM features of neuropeptides. In summary, neuropeptidomics for untargeted, global analyses of neuropeptides is essential for elucidation of proteases that generate diverse neuropeptides for cell-cell signaling.

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Stability-Indicating Methods for the Determination of Cimetidine Using Derivative and Fourier-Transform Infrared Spectrophotometry

Abstract

Two different techniques, that is, second (D₂) and third (D₃) derivative spectrophotometry and fourier transform infrared (FTIR) Spectrophotometry, are investigated for the selective determination of the intact cimetidine in presence of up to 25% and 75% of its degradates, respectively. The procedures determine 2–10 jag ml^?1 at 224 nm and 217.5 nm by D₂ and D₃, respectively, and 1–6 mg per 250 mg in K Br by the FTIR with mean accuracies of 100.0 ± 1.07%, 100.5 ± 0.87% and 100.3 ± 1.16%, respectively. The drug is successfully analysed in its pharmaceutical formulations.

     

Investigation of "on water" conditions using a biphasic fluidic platform

Converting the DEAD: A fluidic approach to generate precisely defined water-oil interfaces was used to quantify the influence of the water surface (blue drops) on chemical reactions between quadricyclane or β-pinene and diethyl azodicarboxylate (DEAD). This method allows for easy investigation of the "on water" effect.     

Parabens Permeation through Biological Membranes: A Comparative Study Using Franz Cell Diffusion System and Biomimetic Liquid Chromatography

Parabens (PBs) are used as preservatives to extend the shelf life of various foodstuffs, and pharmaceutical and cosmetic preparations. In this work, the membrane barrier passage potential of a subset of seven parabens, i.e., methyl-, ethyl-, propyl- isopropyl, butyl, isobutyl, and benzyl paraben, along with their parent compound, p-hydroxy benzoic acid, were studied. Thus, the Franz cell diffusion (FDC) method, biomimetic liquid chromatography (BLC), and in silico prediction were performed to evaluate the soundness of both describing their permeation through the skin. While BLC allowed the achievement of a full scale of affinity for membrane phospholipids of the PBs under research, the permeation of parabens through Franz diffusion cells having a carbon chain > ethyl could not be measured in a fully aqueous medium, i.e., permeation enhancer-free conditions. Our results support that BLC and in silico prediction alone can occasionally be misleading in the permeability potential assessment of these preservatives, emphasizing the need for a multi-technique and integrated experimental approach.     

Mechanistic studies on the intramolecular electron transfer in an adduct species of the oxo-centred trinuclear iron(III) cation and <Emphasis Type="SmallCaps">l</Emphasis>-ascorbic acid in aqueous solution

The kinetics of the intra-molecular electron transfer of an adduct of l-ascorbic acid and the [Fe₃^IIIO(CH₃COO)₆(H₂O)₃]⁺ cation in aqueous acetate buffer was studied spectrophotometrically, over the ranges 2.55 ≤ pH ≤ 3.74, 20.0 ≤ θ ≤ 35.0 °C, at an ionic strength of 0.50 and 1.0 mol dm⁻³ (NaClO₄). The reaction of l-ascorbic acid and the complex cation involves the rapid formation of an adduct species followed by a slower reduction in the iron centres through consecutive one-electron transfer processes. The final product of the reaction is aqueous iron(II) in acetate buffer. The proposed mechanism involves the triaqua and diaqua-hydroxo species of the complex cation, both of which form adducts with l-ascorbic acid. At 25 °C, the equilibrium constant for the adduct formation was found to be 86 ± 15 and 5.8 ± 0.2 dm³ mol⁻¹ for the triaqua and diaqua-hydroxo species, respectively. The kinetic parameters derived from the rate expression have been found to be: k ₀ = (1.12 ± 0.02) × 10⁻² s⁻¹ for the combined spontaneous decomposition and k ₁ = (4.47 ± 0.06) × 10⁻² s⁻¹ (ΔH ₁^‡ = 51.0 ± 2.3 kJ mol⁻¹, ΔS ₁^‡ = −100 ± 8 J K⁻¹ mol⁻¹), k ₂ = (4.79 ± 0.38) × 10⁻¹ s⁻¹ (ΔH ₂^‡ = 76.5 ± 0.8 kJ mol⁻¹, ΔS ₂^‡ = 6 ± 3 J K⁻¹ mol⁻¹) for the triaqua and diaqua-hydoxo species, respectively.     

Synthese und Struktur von Ruthenium(II)‐Komplexen mit Triazenido‐ und Pentaazadienido‐Liganden

Synthesis and Crystal Structure of Ruthenium(II) Complexes with Triazenido and Pentaazadienido Ligands The ruthenium(II) triazenido complex [RuCl(ClC₆H₄N₃C₆H₄Cl)(p‐cymene)] ( 1 ) is obtained by the reaction of silver bis(p‐chlorphenyl)triazenid with [RuCl₂(p‐cymene)]₂ in CH₂Cl₂, and forms air stable, orange yellow crystals. It crystallizes as 1 ·CH₂Cl₂ in the orthorhombic space group Pbca with the lattice parameters a = 3134.3(3), b = 2105.7(2), c = 769.15(4) pm and Z = 8. In the diamagnetic mononuclear complex 1 the chelating triazenido ligand coordinates with the atoms N(1) and N(3). p‐Cymene binds η⁶ with its C₆ ring. The reaction of the etherphosphane complex [RuCl₂(Ph₂PCH₂C₄H₇O₂)₂] with 1, 3‐bis(p‐tolyl)triazenid in THF yields the complex [RuCl(tolyl‐N₃‐tolyl)(Ph₂PCH₂C₄H₇O₂)₂] ( 2 ). 2 forms monoclinic, red crystals with the space group P2₁/c and a = 1521.0(2), b = 1451.8(2), c = 2073.7(2) pm, β = 99.29(1)° and Z = 4. It is air stable and diamagnetic. The triazenide ion coordinates with the atoms N(1) and N(3). One of the two etherphosphane ligands is chelating and coordinates with the P atom and one O atom, while the other ligand binds in a monodentate fashion with its P atom, resulting in a coordination number of six for the Ru^II. [Ag(tolyl‐N₅‐tolyl)]₂ reacts in THF with [RuCl₂(C₆H₆)]₂ to afford the air stable, diamagnetic pentaazadienido complex [RuCl(tolyl‐N₅‐tolyl)(C₆H₆)] ( 3 ). 3 forms monoclinic, red crystals with the space group P2₁/c and a = 1462.4(1), b = 1056.51(8), c = 1371.4(1) pm, β = 114.36(1)° and Z = 4. The chelating pentaazadienido ligand coordinates with the atoms N(1) and N(3) at the divalent Ru atom. The benzene molecule binds η⁶ with its π system.