Quenching effect of l-tyrosine on peroxyoxalate chemiluminescence of berberine as the fluorophore

The present work deals with the first attempt to study the effect of l-tyrosine on the characteristics of the peroxyoxalate chemiluminescence. Berberine was applied as an efficient fluorophore. The investigated parameters include rise and fall rate constant for the chemiluminescence burst, theoretical and experimental maximum intensity, the time needed to reach maximum intensity and the total light yield emission, which is theoretically evaluated using the pooled intermediate model by a computerized non-linear least-squares curve fitting program (KINFIT). Furthermore, based on the observed quenching effect of tyrosine, the Stern–Volmer plot with K _Q value of 7.7 × 10⁴ M^?1 in the quencher concentration range 4 × 10^?6–5 × 10^?5 M. Moreover, this method is applied to determinate tyrosine in biological samples successfully.     

Synthesis and Reactions of Some Novel Nicotinonitrile,Thiazolotriazole, and Imidazolotriazole Derivatives for Antioxidant Evaluation

The novel 2-(1H)-pyridone, the lead compound of the pyridone derivative 1, reacted with an electrophilic reagent (ethyl chloroacetate) to give the corresponding ester 2. Condensation of compound 2 with thiosemicarbazide and/or hydrazine hydrate afforded the mercaptotriazole and the corresponding acetic acid hydrazide derivatives 3 and 4, respectively. The latter compound reacted with ethyl acetoacetate, ethyl cyanoacetate, and maleic anhydride to give compounds 5, 6, and 7, respectively. Alkylation of compound 3 with methyl iodide or chloroacetic acid afforded methylsulfanyltriazole and thiazolotriazole derivatives 8 and 9, respectively. Compound 8 reacted with glycine to afford the imidazotriazole derivative 10. Both compounds 9 and 10 reacted with glucose and benzaldehyde to give compounds 11, 12, 13, and 14, respectively. Some of the prepared products were selected and subjected to screening for their antioxidant activity.     

Validation of scanning electron microscope (SEM), energy dispersive X-ray (EDX) and gamma spectrometry to verify source nuclear material for safeguards purposes

Ten ore samples, two unpurified yellow cake samples and natural uranyl nitrate hexahydrate sample were analyzed by Scanning Electron Microscope (SEM) and Energy Dispersive X-ray (EDX) method to verify source nuclear material. Samples represent source nuclear material as possible. All samples were scanned at ideal conditions; working distance = 10 mm, voltage = 30 kV, magnification value = × 100, spot size = 50 to screen samples for the presence of uranium and thorium, Also Hyper pure germanium (HPGe) gamma spectrometers were applied to estimate the uranium and thorium contents in Bq/kg (ppm). For the ore samples uranium-238 ranges from 1,049.23 Bq/kg (85.30 ppm) to 2,096.06 Bq/kg (170.41 ppm), uranium-235 ranges from 47.51 to 105.61 Bq/kg and thorium-232 ranges from 22.84 Bq/kg (5.65 ppm) to 41.78 Bq/kg (10.34 ppm). For the yellow cake samples and uranyl nitrate hexahydrate uranium-238 ranges from 42.99 Bq/kg (3.50 ppm) to 71,887.2 Bq/kg (5,844.49 ppm) and thorium-232 is 4.78 Bq/kg (1.83 ppm) and the other two samples are lower than the detection limit.     

Retention profile of Fe,Mn and Cu onto chemically treated polyurethane with carbon disulfide

Dithiocarbamate modified polyurethane foam (DTC-PUF) was synthesized as a new solid-phase extraction sorbent for the preconcentration and determination of Fe(II), Mn(II) and Cu(II) in environmental samples using flame atomic absorption spectrometry. Maximum extraction of the elements was achieved at pH 5–7 and flow rate 3 mL min^?1. Quantitative desorption was achieved by 10 mL from 1.0 mol L^?1 HCl solution. The capacity of the sorbent was 149.2 ± 0.5, 237.5 ± 0.2, 200.2 ± 0.1 μg g^?1 and the limit of detection was of 0.015, 0.015 and 0.012 μg mL^?1for Fe(II), Mn(II) and Cu(II), respectively. A preconcentration factor of 100 was obtained for all elements. The developed method was successfully applied to the determination of the tested elements in water (tap and lake) and plant (spinach and parsley leaves) samples and showed good recovery values from 98 to 111% with corresponding RSD values ranged from 0.6 to 8.6%.     

Synthesis of Interglycosidically S‐Linked 1‐Thio‐Oligosaccharides Under Microwave Irradiation*

Microwave irradiation (MWI) has accelerated the synthesis of S‐(2,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranosyl)thiouronium bromide (2a), whose reaction with 2,3,4,6‐tetra‐O‐acetyl‐α‐D‐glucopyranosyl bromide (1a) in the presence of Et₃N afforded stereoselectively the acetylated β,β‐1‐thiotrehalose 4a. Similarly, the respective D‐galactopyranosyl 4b and 2‐acetylamino‐2‐deoxy‐D‐glucopyranosyl 4c analog as well as 4,4′‐di‐O‐(2,3,4,6‐tetra‐O‐acetyl‐β‐D‐galactopyranosyl) 4d and 4,4′‐di‐O‐(2,3,4,6‐tetra‐O‐acetyl‐α‐D‐glucopyranosyl) 4e derivatives of 2,2′,3,3′,6,6′‐hexa‐O‐acetyl β,β‐1‐thiotrehalose were prepared.     

Synthesis of Chitosan-La2O3 Nanocomposite and Its Utility as a Powerful Catalyst in the Synthesis of Pyridines and Pyrazoles

Recently, the development of nanocatalysts based on naturally occurring polysaccharides has received a lot of attention. Chitosan (CS), as a biodegradable and biocompatible polysaccharide, is considered to be an excellent template for the design of a hybrid biopolymer-based metal oxide nanocomposite. In this case, lanthanum oxide nanoparticles doped with chitosan at different weight percentages (5, 10, 15, and 20 wt% CS/La₂O₃) were prepared via a simple solution casting method. The prepared CS/La₂O₃ nanocomposite solutions were cast in a Petri dish in order to produce the developed catalyst, which was shaped as a thin film. The structural features of the hybrid nanocomposite film were studied by FTIR, SEM, and XRD analytical tools. FTIR spectra confirmed the presence of the major characteristic peaks of chitosan, which were modified by interaction with La₂O₃ nanoparticles. Additionally, SEM graphs showed dramatic morphological changes on the surface of chitosan, which is attributed to surface adsorption with La₂O₃ molecules. The prepared CS/La₂O₃ nanocomposite film (15% by weight) was investigated as an effective, recyclable, and heterogeneous base catalyst in the synthesis of pyridines and pyrazoles. The nanocomposite used was sufficiently stable and was collected and reused more than three times without loss of catalytic activity.     

Electropolymerized coatings of poly(o‐anisidine) and poly(o‐anisidine)‐TiO2 nanocomposite on aluminum alloy 3004 by using the galvanostatic method and their corrosion protection performance

Poly(o‐anisidine) (POA) and poly(o‐anisidine)‐TiO₂ (POA‐TiO₂) nanocomposite coatings on aluminum alloy 3004 (AA3004) have been investigated by using the galvanostatic method. The electrosynthesized coatings were characterized by FT ‐ IR spectroscopy, XRD, SEM ‐ EDX and SEM. The corrosion protection performance of POA and POA‐TiO₂ nanocomposite coatings was investigated in the 3.5% NaCl solution by using potentiodynamic polarization technique and electrochemical impedance spectroscopy. The results show that the corrosion rate of the nanocomposite coatings is about 900 times lower than the bare AA3004 under optimal conditions. Copyright © 2013 John Wiley & Sons, Ltd.     

Reversible Assembly of Microgels by Metallo-Supramolecular Chemistry

The combination of supramolecular chemistry and soft colloids as microgels represents an ambitious way to develop multi-versatile colloidal assemblies. Hereafter, terpyridine-functionalized poly(N-isopropylacrylamide) (PNiPAM) microgel building blocks are shown to undergo an assemble–freeze–disassemble process. The microgel assemblies, which are controlled by monitoring the attractive and repulsive potentials between the soft colloidal particles, are then frozen by forming inter-particle metal–terpyridine bis-complexes upon addition of the metallic cation (such as Fe^II, Co^II). By oxidation of the metal–terpyridine bis-complex links, the aggregates open up, which is due to the complex dissociation releasing the connected particles in the form of single microgels. We extended our work to the development of 1D filaments and 2D membranes materials made of soft particles connected via supramolecular chemistry.     

Natural radioactivity and radon exhalation rates in building materials used in Egypt

Natural and fabricated building materials commonly used in Egypt were surveyed for both natural radionuclides content and radon exhalation rate. These include raw as well as construction products. Concentration of natural radionuclides in all samples were determined by γ-ray spectroscopy with HPGe detector. For Radon exhalation rate measurements of fabricated samples, the seal can-technique has been applied using CR-39 plastic track detectors. The radiation hazard indices of the total natural radioactivity in the studied samples were estimated. The results were compared with the corresponding results of different countries and were found to be lying within the average world values. Radon exhalation rate in the studied samples varied between 197 (cement brick) and 907 mBq m⁻² h⁻¹ (blast furnace slag cement). The results of this survey suggest that, using blast furnace slag cement for pre-coating the internal walls of buildings in the Urban region of Egypt is discouraged and the replacement of clay brick by cement brick will be more healthy for the public.