Pd(II)-Catalyzed Benzimidazole-Assisted Annulation of 3-(1H-Benzo[d]imidazol-2-yl)-2H-chromen-2-one: Access to Imidazo[1,2-a]chromeno[3,4-c]pyridine

Palladium-catalyzed [4+2] oxidative annulation of coumarin-benzimidazoles with olefins for the synthesis of polycyclic aromatic hydrocarbons have been achieved. This synthetic protocol gives access to a wide range of structurally distinct imidazo[1,2-a]chromeno[3,4-c]pyridines in moderate to good yield with wide functional group tolerance. Further, photophysical properties of annulated scaffolds have been examined, which discloses their interesting solvatochromic emission behaviors.     

Photocatalytic degradation of azo dyes using Zn-doped and undoped TiO2 nanoparticles

Undoped and Zn-doped TiO₂ nanoparticles were synthesized by the sol gel method. The dopant (Zn) was taken at 0.1, 0.2, 0.5, 0.7, and 1.0 mol%. The initial precursors were titanium tetraisopropoxide and zinc acetate. The samples were characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and UV–vis diffuse reflectance. The photocatalytic activity of the prepared nanoparticles was studied by observing their role in degradation of two azo dyes, i.e., Eriochrome Black T and Methyl Red under UV–visible light. The results revealed that Zn-doped TiO₂ nanoparticles exhibited better degradation as compared to undoped TiO₂ nanoparticles. In this study, 0.7 mol% Zn-doped TiO₂ showed highest photocatalytic activity. Doping of Zn allowed better separation of electron–hole pairs which results in increased oxidation and reduction reactions.     

Stevia rebaudiana targeting α-amylase: An in-vitro and in-silico mechanistic study

Diabetes mellitus (DM) is the fastest growing metabolic disorder in the world. Recently, more attention is paid to the study of natural products due to side effects of synthetic drugs. Stevia rebaudiana (Bertoni) is considered an encouraging starting point for the antidiabetic lead development. In the present study, the in vitro α-amylase inhibitory activity of the extracts of S. rebaudiana is investigated. In order to understand the molecular mechanism and future pharmacophore development, in silico study of secondary metabolites isolated from S. rebaudiana was carried out. Results indicated that water extract shows highest α-amylase inhibitory activity as compared to other extracts. Moreover, compound 20 (rebaudioside A) which has been previously reported and isolated from water extract showed the impressive binding profile with α-amylase. Therefore, our study suggests that S. rebaudiana could be used in the development of therapeutic drugs for the treatment of diabetes.     

Williamson–Hall study on synthesized nanocrystalline tungsten carbide (WC)

Ag clusters obtained by the gas-aggregation technique were deposited on the cleavage face (001)NaCl. The average size of the nanoparticles was varied in the range from 0.2 to 10 nm and the temperature was varied from room temperature to 470 K. Owing to the mobility of the clusters on the substrate, they coalesced with formation of larger particles, decorating atomic cleavage steps on (001)NaCl already at room temperature. It was shown that the step decoration is possible only when the average size of the deposited clusters is commensurable with the height of the cleavage steps.     

A semisynthetic Eph receptor tyrosine kinase provides insight into ligand-induced kinase activation

We have developed a methodology for generating milligram amounts of functional Eph tyrosine kinase receptor using the protein engineering approach of expressed protein ligation. Stimulation with ligand induces efficient autophosphorylation of the semisynthetic Eph construct. The in vitro phosphorylation of key Eph tyrosine residues upon ligand-induced activation was monitored via time-resolved, quantitative phosphoproteomics, suggesting a precise and unique order of phosphorylation of the Eph tyrosines in the kinase activation process. To our knowledge, this work represents the first reported semisynthesis of a receptor tyrosine kinase and provides a potentially general method for producing single-pass membrane proteins for structural and biochemical characterization.     

The reaction of PPh3 with Di-μ-chlorobis(arylazooximato)dipalladium(II)

Summary Di--chlorobis(arylazooximato)dipalladiuni(II) compounds react with PPh₃ to give the four-coordinate complexes (5) and (4) in which the azooxime acts as a unidentate and bidentate ligand respectively. Hydrogen bonding in polar solvents such as MeOH or EtOHetc. stabilize (5) whereas, polar solvents such as Me₂CO, py and Et₂O convert (5) into (4). The equilibrium: (4) + PPh₃ (5) exists in PhH solution and equilibrium constants at 30°C have been calculated spectrophotometrically. The variation in equilibrium constants and the stabilities of (5) have been explained on the basis of electron-releasing and electron-withdrawing properties of substituents, R, in the azooxime ligand.     

The mechanism of sonochemical degradation of a cationic surfactant in aqueous solution

The sonochemical degradation of the cationic surfactant, laurylpyridinium chloride (LPC), in water was studied at concentrations of 0.1-0.6 mM, all below its critical micelle concentration (15 mM). It has been found that the initial step in the degradation of LPC occurs primarily by a pyrolysis pathway. Chemical analysis of sonicated solutions by gas chromatography, electrospray mass spectrometry, and high performance liquid chromatography reveals that a broad range of decomposition products, hydrocarbon gases and water-soluble species, are produced. Propionamide and acetamide were identified as two of the degradation intermediates and probably formed as the result of the opening of the pyridinium ring following OH radical addition. Most of the LPC is eventually converted into carboxylic acids. The complete mineralization of these carboxylic acids by sonolysis is however a comparatively slow process due to the hydrophilic nature of these low molecular weight products.