Reaction in Dry Media: Silica Gel Supported Ferric Chloride Catalyzed Synthesis of 1,8-Dioxo-octahydroxanthene Derivatives

Herein, we describe a green procedure for the one-pot preparation of 1,8-dioxo-octahydroxanthene derivatives by condensation of dimedone and substituted benzaldehydes in the presence of FeCl ₃ -SiO ₂ as an efficient and heterogeneous catalyst under microwave irradiation and thermal conditions. This method has the advantages of high yields, cleaner reactions, efficient and cost-effective method, simple methodology, short reaction times, easy workup, and greener conditions.     

Preparation and Characterization of Cu2S Nanoparticles Via Ultrasonic Method

This study reports on the synthesis of Cu₂S nanoparticles via an ultrasonic method by employing Na₂SO₃ as a reducing agent. Morphology, structure, and composition of the obtained products were characterized by X-ray diffraction, energy dispersive X-ray analysis, scanning electron microscope and photoluminescence spectroscopy. The effects of time and power of irradiation were studied.     

Synthesis of New and Novel N-Protected 1-Aminoalkyl-2-naphthol Derivatives

A series of three-component reactions has been carried out using HClO₄-SiO₂ as a versatile heterogeneous catalyst. A series of new and novel N-protected 1-aminoalkyl-2-naphthol derivatives have been prepared under thermal solvent-free reaction conditions. In all cases, the reaction conditions were very simple and high-yielding.     

Aluminum Chloride (Alcl3) Promotes Selective Oxidative Deprotection of Benzylic Trimethylsilyl and Tert- Butyldimethylsilyl Ethers to the Corresponding Carbonyl Compounds with Manganese Dioxide (Mno2)

Various types of trimethylsilyl and tert-butyldimethylsilyl ethers of primary and secondary benzylic alcohols could be selectively converted to their corresponding carbonyl compounds with MnO₂ in the presence of AlCl₃ in good to excellent yields.     

Measurement of natural radioactivity in soil from Peshawar basin of Pakistan

Natural radioactivity in the environment may change with time due to human activities, chemical and biological changes. From the view of radiation risk to population, the knowledge of natural radioactivity levels and the measurement of collective radiation dose received by the population is very vital. Radiological constraints on soil of thickly populated Peshawar basin in northern Pakistan were assessed through radiometric assay. Soil samples collected from different locations of four districts of this basin were analysed using an HPGe gamma spectrometer. Activity concentrations of ⁴⁰K, ²²⁶Ra and ²³²Th in these samples was 648 ± 121 (421–996), 45 ± 7 (32–60) and 59 ± 7 (46–72) Bq kg^?1, respectively that followed lognormal distribution. The average concentrations of primordial radionuclides were found to be higher than that reported for the worldwide soil. Radium equivalent activity and gamma index derived from these activity concentrations were lesser than their respective limits. The average absorbed dose rate and the annual effective dose for both indoor and outdoor cases were found to be higher than the values given in the UNSCEAR 2000 report. The results of the present study were compared with those for other locations of Pakistan along with that for the world. The radiological impact of the measured data was evaluated using hazard assessment models. A thoughtful discussion of the above mentioned evaluation is also given.     

In Silico and Experimental Characterization of Chimeric Bacillus thermocatenulatus Lipase with the Complete Conserved Pentapeptide of Candida rugosa Lipase

Lipases are one of the highest value commercial enzymes as they have broad applications in detergent, food, pharmaceutical, and dairy industries. To provide chimeric Bacillus thermocatenulatus lipase (BTL2), the completely conserved pentapeptide (¹¹²Ala-His-Ser-Gln-Gly¹¹⁶) was replaced with similar sequences (²⁰⁷Gly-Glu-Ser-Ala-Gly²¹¹) of Candida rugosa lipase (CLR) at the nucleophilic elbow region. For this purpose, three mutations including A112G, H113E, and Q115A were inserted in the conserved pentapeptide sequence of btl2 gene. Based on the crystal structures of 2W22, the best structure of opened form of the chimeric lipases were garnered using the MODELLER v9.10 software. The native and chimeric lipases were docked to a set of ligands, and a trial version of Molegro Virtual Docker (MVD) software was used to obtain the energy values. Docking results confirmed chimeric lipase to be better than the native lipase. Following the in silico study, cloning experiments were conducted and expression of native and chimeric btl2 gene in Pichia pastoris was performed. The native and chimeric lipases were purified, and the effect of these mutations on characteristics of chimeric lipase studied and then compared with those of native lipase. Chimeric lipase exhibited 1.6-fold higher activity than the native lipase at 55 °C. The highest percentage of both lipases activity was observed at 60 °C and pH of 8.0. The ion Ca²⁺ slightly inhibited the activity of both lipases, whereas the organic solvent enhanced the lipase stability of chimeric lipase as compared with the native lipase. According to the results, the presence of two glycine residues at the conserved pentapeptide region of this chimeric lipase (¹¹² Gly-Glu-Ser-Ala-Gly ¹¹⁶) may increase the flexibility of the nucleophilic elbow region and affect the enzyme activity level.     

Synthesis and antibacterial activity of ethyl 2-amino-6-methyl-5-oxo- 4-aryl-5,6-dihydro-4H-pyrano[3,2-c]quinoline-3-carboxylate

The three-component reaction of 4-hydroxy-1-methyl-2(1H)-quinolinone, aromatic aldehydes and ethyl cyanoacetate was carried out in the presence of a catalytic amount of 4-dimethyl aminopyridine(DMAP) in aqueous ethanol. The reactions result in the formation of pyranoquinoline derivatives in excellent yields. Antibacterial activity has been evaluated against Gram positive and Gram negative bacteria for some of the synthesized compounds. The results indicated that these compounds are moderately effective against bacterial growth and their effectiveness is highest against Pseudomonas aeruginosa.     

Purification and Characterization of Pepsin-Solubilized Collagen from Skin of Sea Cucumber Holothuria parva

Pepsin-solubilized collagen (PSC) was extracted from the skin of sea cucumber Holothuria parva and was fractionally characterized. The PSC from H. parva skin consisted of three α₁ chains (α₁)₃, in contrast to calf skin collagen type I with two α₁ and one α₂ chains (α₁)₂α₂ with approximately 130 kDa each. The maximum transition (T_m) and denaturation temperature (T_d) of PSC were determined to be 46.94 and 32.5 °C, respectively. The amino acid composition analysis revealed that glycine, proline, alanine, and hydroxyproline were the abundant amino acids available in extracted PSC. The results showed that the isolated collagen from H. parva has some similar characteristics to previously reported collagens used in food and pharmaceutical industries.     

A three‐phase solvent extraction system combined with deep eutectic solvent‐based dispersive liquid–liquid microextraction for extraction of some organochlorine pesticides in cocoa samples prior to gas chromatography with electron capture detection

A sample pretreatment method based on the combination of a three‐phase solvent extraction system and deep eutectic solvent‐based dispersive liquid–liquid microextraction has been introduced for the extraction of four organochlorine pesticides in cocoa samples before their determination by gas chromatography‐electron capture detection. A mixture of sodium chloride, acetonitrile, and potassium hydroxide solution is added to cocoa bean or powder. After vortexing and centrifugation of the mixture, the collected upper phase (acetonitrile) is removed and mixed with a few microliters of N,N‐diethanol ammonium chloride: pivalic acid deep eutectic solvent. Then it is rapidly injected into deionized water and a cloudy solution is obtained. Under optimum conditions, the limits of detection and quantification were found to be 0.011‐0.031 and 0.036‐0.104 ng/g, respectively. The obtained extraction recoveries varied between 74 and 92%. Also, intra‐ (n = 6) and interday (n = 4) precisions were less than or equal to 7.1% for the studied pesticides at a concentration of 0.3 ng/g of each analyte. The suggested method was applied to determine the studied organochlorine pesticide residues in various cocoa powders and beans gathered from groceries in Tabriz city (Iran) and aldrin and dichlobenil were found in some of them.     

Single and double electron capture associated with target K-shell ionization for F7 + ,8 + ,9++Ar

Ratios for target Ar K-shell ionization associated with single and double electron capture, as well as the ratios corresponding to total capture and the projectile K x rays, were determined for 1.8- to 2.2-MeV/u F^{7 + ,8 + ,9+} projectiles. This work was performed at Western Michigan University with the tandem Van de Graaff accelerator. Coincidences between emitted K-shell X-rays (both target and projectile) and the corresponding charge-changed particles were observed. The F⁹⁺ Ar K X-ray coincidence ratios for double to single capture are found to well exceed unity over the limited energy range of the measurements. Possible explanations for this anomalous behavior are discussed.