Effects of Sucrose and Trehalose on Stability,Kinetic Properties,and Thermal Aggregation of Firefly Luciferase

In this study, we used sugars as stabilizing additives to improve the thermostability and to inhibit aggregation of firefly luciferase. The combination of sucrose and trehalose has a strong stabilizing effect on firefly luciferase activity and prevents its thermoinactivation. These additives can also increase optimum temperature. It has been shown that the presence of both sucrose and trehalose can inhibit thermal aggregation of firefly luciferase and decrease bioluminescence decay rate. In order to understand the molecular mechanism of thermostabilization, we investigated the effects of sucrose and trehalose combination on the secondary structure of luciferase by Fourier transform infrared spectroscopy. Minor changes in content of secondary structure of firefly luciferase are observed upon treatment with additives.     

Diastereoselective synthesis of fused [1,3]oxazines from ethyl pyruvate,activated acetylenes and N-heterocycles

The 1:1 zwitterionic intermediates obtained from the reaction between isoquinoline, quinoline, pyridine, or N-methylimidazole with activated acetylenes are trapped by ethyl pyruvate to produce highly functionalized fused [1,3]oxazines in good yields.     

NiFe2O4@SiO2@Cu3(BTC)2 nanocomposite as a magnetic metal–organic framework

A new magnetic metal–organic framework (MOF), namely, NiFe₂O₄@SiO₂@Cu₃(BTC)₂, was synthesized via an in situ method using Fe(NO₃)₃, Ni(NO₃)₂, CuN₂O₆, TEOS, (3-aminopropyl)triethoxysilane, and benzene-1,3,5-tricarboxylic acid. Three different samples were fabricated according to a formula; xNiFe₂O₄@(100 − x)SiO₂@Cu₃(BTC)₂, where x = 10, 30, and 50. The integration of the intrinsic characteristic of Cu₃(BTC)₂ as an MOF with strong magnetic properties of NiFe₂O₄ could lead to an exquisite material with specific behaviors. X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), diffuse reflectance spectroscopy (DRS), photoluminescence (PL), vibrating sample magnetometer (VSM), transmission electron microscopy (TEM), and simulated thermal analyzer (STA) were utilized to characterize the mentioned samples. Results approved that the synthesized compounds were composed of SiO₂ and Cu-MOF and NiFe₂O₄ crystalline phases with rod-like morphology. The similarity between the morphology of the synthesized samples and Cu-MOF approved that an appropriate fabrication method has been selected. This fact led to observe mesoporous composites with 38–90 m² g⁻¹ specific surface area. PL spectroscopy confirmed the near bandgap emission, ligand-to-metal charge transfer, and metal-to-ligand charge transfer. Although all the samples had magnetic hysteresis, the highest magnetization was seen in the 50NiFe₂O₄@SiO₂@Cu₃(BTC)₂ sample. This composite compound with a magnetization value of 2 emu g⁻¹ at 8000 Oe and a specific surface area of 90 m² g⁻¹ could be classified as a magnetic MOF (MMOF). STA results suggested that 400°C is the highest operating temperature for this compound.     

Synthesis of 1,2,3,5-substituted pyrroles from α-bromoacetophenones and 2-nitroethene-1,1-diamines

The simple synthesis of 1,2,3,5-substituted pyrroles from α-bromoacetophenones and 2-nitroethene-1,1-diamines in the presence of K₂CO₃ in DMF at 120 °C is described. A range of fused and non-fused polysubstituted pyrroles were prepared in high yields with short reaction times.     

A Simple and Sensitive Analytical Method for Determination of Naltrexone Level in Plasma by GC–MS

A gas chromatography-mass spectrometry method for determination of naltrexone in plasma is presented. The method is based on pre-column derivatization of analyte to trimethylsilyl derivative of naltrexone. The analyte and internal standard were extracted from plasma by liquid–liquid extraction. Validation of the method has been studied in the concentration range 1–50 ng mL⁻¹.

     

Studies towards the Synthesis of (+)-Dictyoxetane

The dolabellane-type diterpene dictyoxetane represents a significant challenge to synthetic organic chemistry. Methodology directed towards the total synthesis of naturally occurring (+)-dictyoxetane is reported. Catalytic asymmetric synthesis of the trans-hydrindane ring system is achieved through chemoselective deoxygenation of the Hajos-Parrish ketone. An alternative to the Garst-Spencer furan annulation is developed for the synthesis of a 2,5-dimethyl, tetrasubstituted furan, employing a tandem 5-exo-dig alcohol to alkyne cyclisation/aromatisation reaction as a key step. The (4+3) cycloaddition reaction of an oxyallyl cation with a tetrasubstituted furan is established on a cyclohexanone-derived model system, and a range of related (4+3) cycloadditions investigated on a homochiral, trans-hydrindane-fused furan, where regio- and diastereoselectivity is required for the natural product synthesis. In an alternative (4+2) Diels-Alder approach, a C₂-symmetric vinyl sulfoxide-based chiral ketene equivalent is used to prepare oxanorbornenes with the same oxygen bridge stereochemistry found in the 2,7-dioxatricyclo[4.2.1.0^3,8]nonane ring system of the natural product.     

Synthesis and Characterization of CdS Nanoparticles via Cyclic Microwave from Cadmium Oxalate

The present study reports synthesis and characterization of CdS nanoparticles prepared by cyclic microwave route with the use of [Cd(C₂O₄)·3H₂O] powder as a precursor. The products, with an average size ~15 nm, were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray microanalysis, thermogravimetric analysis, transmission electron microscopy and Fourier transform infrared spectroscopy. Optical property of obtained product was investigated by photoluminescence spectroscopy. The prepared nanostructures displayed a very strong luminescence at 528 nm (2.34 eV) at room temperature.     

Heteroleptic copper switches

Heteroleptic copper compounds have been designed and synthesized on solid supports. Chemical redox agents were used to change the oxidation state of the SiO(2)-immobilized heteroleptic copper compounds from Cu(I) to Cu(II) and then back to Cu(I). Optical spectroscopy of a dimethyl sulfoxide suspension demonstrated the reversibility of the Cu(I)/Cu(II) SiO(2)-immobilized compounds by monitoring the metal-to-ligand charge transfer peak at about 450 nm. Electron paramagnetic resonance spectroscopy was used to monitor the isomerization of Cu(I) tetrahedral to Cu(II) square planar. This conformational change corresponds to a 90° rotation of one ligand with respect to the other. Conductive atomic force microscopy and macroscopic gold electrodes were used to study the electrical properties of a p(+) Si-immobilized heteroleptic copper compound where switching between the Cu(I)/Cu(II) states occurred at -0.8 and +2.3 V.