A DFT study of the mechanism and selectivities of the [3 + 2] cycloaddition reaction between 3‐(benzylideneamino)oxindole and trans‐β‐nitrostyrene

The mechanism and regioselectivities and stereoselectivities of the [3 + 2] cycloaddition (32CA) reaction of 3‐(benzylideneamino) oxindole (AY) and trans‐β‐nitrostyrene have been studied using both B3LYP and ωB97XD density functional theory methods together with the standard 6‐31G(d) basis set. Four reactive pathways associated with the ortho and meta regioselective channels and endo and exo stereoselective approaches modes have been explored and characterized. While the B3LYP functional fails to predict the experimental regioselectivity, the ωB97XD one succeeds to predict the experimentally observed meta regioselectivity favoring the formation of meta/endo cycloadduct as the major isomer. Inclusion of solvent effects increases the regioselectivity and decreases the experimentally observed stereoselectivity. Analysis of the density functional theory global reactivity indices and the Parr functions of the reagents in its ground state allows explaining the reactivity and the meta regioselectivity of this zwitterionic‐type 32CA reaction, which account for the high polar character of this reaction. Non‐covalent interaction analysis of the most favorable meta/endo transition state structure reveals that the formation of a hydrogen‐bond between 1 nitro oxygen and the AY N–H hydrogen is responsible for the selectivity experimentally found in this polar zwitterionic‐type 32CA reaction.     

Synthesis, characterization, and electrical properties studies of cadmium selenide nanoparticle

A new solvothermal route was used for the preparation of CdSe nanoparticles at 160 °C for 10 h using ethylenediamine as a solvent. X-ray powder diffraction and transmission electron microscope were employed to characterize the size, morphology, and crystalline structure of the as-prepared sample. The formation process was discussed and it revealed a uniform hexagonal shape of CdSe nanoparticle with good dispersion, with an average size of 35 nm. Fourier transform infrared and ultraviolet-visible spectroscopies were used to follow the reaction and to determine the optical band gap. DC and AC electrical conductivities were studied and the activation energies were determined as well as the conduction mechanism. The results indicated that CdSe behaves as a semiconducting material. The dielectric properties were measured as a function of temperature at different frequencies ranging from 100 Hz to 100 kHz. The increase of the dielectric constant with increasing temperature was discussed on the basis of increasing polarizability, while its decrease with increasing frequency is attributed to the dielectric dispersion.     

Synthesis of imprinted polymer material with palladium ion nanopores and its analytical application

Ion imprinted polymer (IIP) materials with nanopores were prepared by formation of ternary complex of palladium imprint ion with dimethylglyoxime (DMG) and 4-vinylpyridine (VP, functional monomer) and thermally copolymerizing with styrene (crosslinking monomer) and divinylbenzene (cross linker) and 2,2′-azobisisobutyronitrile as initiator. The synthesis was carried out with cyclohexanol as porogen and subsequently leached with 50% (v/v) HCl to obtain leached IIP particles. These leached IIP particles can now pick up palladium ions from dilute aqueous solutions. The optimal acidity for quantitative enrichment was 0.2-0.4N HCl and eluted completely by stirring for 15 min with 2×10 ml of 50% (v/v) HCl. The palladium ion imprinting polymer gave 100 times higher distribution ratio than ion recognition (blank) polymer (IRP). Further, percent extraction, distribution ratio and selectivity coefficients of palladium and other selected inorganic ions using IRP and IIP particles were determined and compared. Five replicate determinations of 50 μg of palladium in 1 l of solution gave a mean absorbance of 0.200 with a relative standard deviation of 2.12%. The detection limit corresponding to three times the standard deviation of the blank was 2.5 μg of palladium/l.     

DIFFERENTIAL SPECTROPHOTOMETRY OF Phycomyces MUTANTS WITH ABNORMAL PHOTORESPONSES

Abstract— The unidentified receptor pigments responsible for phototropism and other blue light responses of Phycomyces are expected to contribute only a minuscule fraction of the in vivo absorption spectra, even for carotene-deficient ( car genotype) albino strains. The variable amount of residual carotenoids in strains with mutations in the carA gene precluded their use for the comparison of phototropism (mad) mutants with phototropically normal controls. We turned instead to carB albino strains, all of which have negligible carotene content. For various mad genes, we isolated carB mad strains by crosses and mutagenesis, and compared them with carB controls, in search of spectral differences associated with the mad photoreception defects. The spectra and their second derivatives show cytochrome bands, as well as a minor peak near 480 nm. This peak was present in carB strains, so it is probably not due to carotenoids. Strains L26 and L136 (both carB madE , but with different genetic backgrounds) showed modifications in the480–500 nm region. Sporangiophores that lacked the green material that usually interferes with in vivo spectroscopy were obtained by the addition of potassium iodide to the culture medium. Dark-grown carB sporangiophores have a more pronounced second-derivative peak at 480 nm than do light-grown sporangiophores. Growth in the light, though, did not significantly alter the spectra of sporangiophores of L131 (carB madB) or L130 (carB madC). The spectral differences may be useful in the biochemical search for the receptor pigments.     

Adsorption of tartrazine from an aqueous solution by octadecyltrimethylammonium bromide-modified bentonite: Kinetics and isotherm modeling

A modified bentonite was prepared at different surfactant (ODTMA) loadings through ion exchange. The obtained organobentonite adsorbent materials were then used for the removal of an anionic dye, tartrazine, from an aqueous solution. The bentonite was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and Brunauer- Emmett-Teller (BET) method. The modification of organophilic bentonite by ODTMA increases the basal spacing d₀₀₁ from 24.1 to 39.1 Å when the cation exchange capacity increases from 1 to 4. The increase in the spacing, due to the basic organic modifications, was confirmed by the results of thermogravimetric analysis, Fourier transform infrared spectroscopy, and BET. The effects of contact time, initial concentration, and solution pH onto an adsorbed amount of tartrazine were investigated. To predict adsorption isotherm, the experimental data were analyzed using the Langmuir and Freundlich isotherm equations. It was determined that the isotherm data were fitted to the Langmuir isotherm. The adsorption process was also found to follow a pseudo-second-order kinetic model.     

An interior-point algorithm for semidefinite least-squares problems

Applications of Mathematics - We propose a feasible primal-dual path-following interior-point algorithm for semidefinite least squares problems (SDLS). At each iteration, the algorithm uses only...     

Solid drop based liquid-phase microextraction

Solid drop based liquid-phase microextraction (SDLPME) is a novel sample preparation technique possessing obvious advantages of simple operation with a high pre-concentration factor, low cost and low consumption of organic solvent. SDLPME coupled with gas chromatography (GC), high-performance liquid chromatography (HPLC), and atomic absorption spectrometry (AAS) has been widely applied to the analyses of a different variety of samples. The basic principles, parameters affecting the extraction efficiency, and the latest applications of SDLPME are reviewed in this article.     

Comparison between a high-resolution single-stage Orbitrap and a triple quadrupole mass spectrometer for quantitative analyses of drugs

The capabilities of a high-resolution (HR), accurate mass spectrometer (Exactive-MS) operating in full scan MS mode was investigated for the quantitative LC/MS analysis of drugs in patients' plasma samples. A mass resolution of 50,000 (FWHM) at m/z 200 and a mass extracted window of 5?ppm around the theoretical m/z of each analyte were used to construct chromatograms for quantitation. The quantitative performance of the Exactive-MS was compared with that of a triple quadrupole mass spectrometer (TQ-MS), TSQ Quantum Discovery or Quantum Ultra, operating in the conventional selected reaction monitoring (SRM) mode. The study consisted of 17 therapeutic drugs including 8 antifungal agents (anidulafungin, caspofungin, fluconazole, itraconazole, hydroxyitraconazole posaconazole, voriconazole and voriconazole-N-oxide), 4 immunosuppressants (ciclosporine, everolimus, sirolimus and tacrolimus) and 5 protein kinase inhibitors (dasatinib, imatinib, nilotinib, sorafenib and sunitinib). The quantitative results obtained with HR-MS acquisition show comparable detection specificity, assay precision, accuracy, linearity and sensitivity to SRM acquisition. Importantly, HR-MS offers several benefits over TQ-MS technology: absence of SRM optimization, time saving when changing the analysis from one MS to another, more complete information of what is in the samples and easier troubleshooting. Our work demonstrates that U/HPLC coupled to Exactive HR-MS delivers comparable results to TQ-MS in routine quantitative drug analyses. Considering the advantages of HR-MS, these results suggest that, in the near future, there should be a shift in how routine quantitative analyses of small molecules, particularly for therapeutic drugs, are performed.     

Green synthesis,molecular docking and pharmacological evaluation of new triazolo-thiadiazepinylcoumarine derivatives as sedative-hypnotic scaffold

4-Amino-5-mercapto-4H-1,2,4-triazole derivative 1 was used as a key intermediate for the preparation of 1,2,4-triazolo[3,4-b][1,3,4]thiadiazepine derivatives 5a-d , 12a-g , and 16 via reactions with the appropriate chalcones 2a-d , α,β-unsaturated carbonitrile derivatives 9a-g and 13 , respectively. The identity of the synthesized compounds was elucidated via their spectral data and elemental analysis. Moreover, the sedative-hypnotic activity of the newly synthesized compounds were evaluated and showed excellent activities especially compounds 12b , 12f , and 16 . Also, their structure activity relationship (SAR) was clearly demonstrated and showed that the electron-donating groups enhance activities while electron-withdrawing groups decrease activities. The molecular docking of the most active derivative 16 against γ-amino butyric acid (GABA) receptor was performed by the MOE 2014 0901program. The acquired outcomes demonstrated that the most active compounds could be a helpful model for future structure, adjustment, and examination to build more active analogs.