The titrimetric determination of sulphate,thiosulphate and polythionates in mining effluents

A titrimetric procedure is described for the determination of various forms of sulphur (sulphate, sulphite, thiosulphate, dithionate, tri- and tetrathionates after conversion to sulphate) in mining effluents. Metal ions are removed, after an oxidizing step, by a cationexchange resin, and the sulphate is precipitated with a known excess of 0.01 M barium chloride at pH 3.5. The excess of barium is back-titrated with standard 0.01 M ethylenediaminetetraacetic acid (EDTA) solution to a o-cresolphthalein complexone end-point at pH 11.0. The results obtained are in good agreement with those obtained by lengthy gravimetric procedures. Indirectly, dithionate can be determined, and sulphate and oxidizable thio salts such as thiosulphate and di-, tri-, and tetrathionates can be distinguished.     

Discovery of a Novel Mycobacterial F‐ATP Synthase Inhibitor and its Potency in Combination with Diarylquinolines

The F₁F_O‐ATP synthase is required for growth and viability of Mycobacterium tuberculosis and is a validated clinical target. A mycobacterium‐specific loop of the enzyme's rotary γ subunit plays a role in the coupling of ATP synthesis within the enzyme complex. We report the discovery of a novel antimycobacterial, termed GaMF1, that targets this γ subunit loop. Biochemical and NMR studies show that GaMF1 inhibits ATP synthase activity by binding to the loop. GaMF1 is bactericidal and is active against multidrug‐ as well as bedaquiline‐resistant strains. Chemistry efforts on the scaffold revealed a dynamic structure activity relationship and delivered analogues with nanomolar potencies. Combining GaMF1 with bedaquiline or novel diarylquinoline analogues showed potentiation without inducing genotoxicity or phenotypic changes in a human embryonic stem cell reporter assay. These results suggest that GaMF1 presents an attractive lead for the discovery of a novel class of anti‐tuberculosis F‐ATP synthase inhibitors.     

Determination of polythionates and thiosulphate in mining effluents and mill circuit solutions

A method is described for the determination of total polythionates plus thiosulphate by acidimetric titration. The titration can be carried out either at the Methyl Orange (pH = 4.30) or at the phenolphthalein (pH = 8.20) end-point, with standard sodium hydroxide solution, to determine the amount of acid produced on oxidation of the thiosulphate and polythionates. The precision and accuracy are good and samples containing as little as 0.1 mg of the thio salt can be analysed very easily. Results obtained by this method are compared with those obtained by a calorimetric method and are in good agreement.     

Use of cadmium selenide thin films as a carbon dioxide gas sensor

Cadmium Selenide (CdSe) thin films were prepared in different growth conditions by thermal evaporation. The films were characterised using transmission electron microscopy and X-ray diffraction. The electrical parameters such as resistivity, carrier mobility, and concentration were determined. The sensitivity of carbon dioxide (CO₂) gas on CdSe thin films were studied. A tentative mechanism was proposed, in which the role of CO₂ gas in increasing the conductivity of CdSe thin films were explained by Molecular Orbital (MO) theory. CO₂ gas sensing alarm system was fabricated.     

Discovery of a Novel Mycobacterial F-ATP Synthase Inhibitor and its Potency in Combination with Diarylquinolines

The F₁F_O-ATP synthase is required for growth and viability of Mycobacterium tuberculosis and is a validated clinical target. A mycobacterium-specific loop of the enzyme's rotary γ subunit plays a role in the coupling of ATP synthesis within the enzyme complex. We report the discovery of a novel antimycobacterial, termed GaMF1, that targets this γ subunit loop. Biochemical and NMR studies show that GaMF1 inhibits ATP synthase activity by binding to the loop. GaMF1 is bactericidal and is active against multidrug- as well as bedaquiline-resistant strains. Chemistry efforts on the scaffold revealed a dynamic structure activity relationship and delivered analogues with nanomolar potencies. Combining GaMF1 with bedaquiline or novel diarylquinoline analogues showed potentiation without inducing genotoxicity or phenotypic changes in a human embryonic stem cell reporter assay. These results suggest that GaMF1 presents an attractive lead for the discovery of a novel class of anti-tuberculosis F-ATP synthase inhibitors.     

Improvement of efficiency of ITO/Se thin film solar cells using tellurium stimulator

Indium Tin Oxide ITO/Se thin film solar cells have been fabricated by vacuum deposition. Prior to deposition of selenium film, ultrathin tellurium film has been deposited on ITO thin film. Tellurium film acts as a stimulator for bringing improvement in crystallite size, adhesion to ITO and electrical behaviour of selenium thin films. The maximum efficiency of the ITO/Se thin film solar cells without tellurium stimulator and with tellurium stimulator under illumination AM1 (100 mW cm⁻²) are found to be 1.68% and 2.27% while under fluorescent tubelight (0.15 mW cm⁻²) are found to be 5.85% and 7.05% respectively. The ITO/Se thin film solar cells exhibits high spectral response at short wavelength. The barrier height of the ITO/Se thin film solar cells was determined.     

Synthesis and vibrational spectra of diphenyl-lead di-isothiocyanate adducts with some O- and N-donor ligands

Diphenyl-lead di-isothiocyanate forms: (a) 1:2 complexes with hexamethylphosphoramide, dimethylsulphoxide, N,N-dimethyl-acetamide, N,N-dimethylformamide, piperidine, and ethylene-diamine; (b) 1:1 complexes with 2,2′-bipyridyl and 1,10-phenanthroline; (c) the condensation product Ph₂Pb(NCS) (ox) with 8-hydroxyquinoline. All complexes are solids, insoluble in common polar and nonpolar organic solvents, and most melt with decomposition at about 200°. Only Ph₂Pb(NCS)₂·2hmpa (m.p. 232°) can be recrystallized from benzene in which it is monomeric. Attempts to isolate complexes of Ph₂Pb(NCS)₂ with triethylphosphate, tetrahydrofuran, dioxane, pyridine, aniline, acetonitrile, triphenylphosphine, acetylacetone, and tetramethylethylenediamine were unsuccessful. The infrared and Raman spectra of Ph₂Pb(NCS)₂ and its complexes show: (a) bands near 2100 cm^?1 which are attributed to ν(CN) of -NCS- bridging groups; (b) bands near 800 cm^?1 which are ^?1 due to the δ(NCS) vibration. These observations and the physical properties of the compounds suggest that weak Pb-S bonds of the -NCS- bridges in polymeric Ph₂Pb(NCS)₂ are broken up by ligands to produce complexes containing lead-ligand bonds, Pb-NCS bonds, and -NCS- bridge bonds to a degree which depends upon the donor power of the ligand.     

3D-QSAR and molecular modeling of HIV-1 integrase inhibitors

Three-dimensional quantitative structure-activity relationship (3D QSAR) methods were applied on a series of inhibitors of HIV-1 integrase with respect to their inhibition of 3-processing and 3-end joining steps in vitro.The training set consisted of 27 compounds belonging to the class of thiazolothiazepines. The predictive ability of each model was evaluated using test set I consisting of four thiazolothiazepines and test set II comprised of seven compounds belonging to an entirely different structural class of coumarins. Maximum Common Substructure (MCS) based method was used to align the molecules and this was compared with other known methods of alignment. Two methods of 3D QSAR: comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were analyzed in terms of their predictive abilities. CoMSIA produced significantly better results for all correlations. The results indicate a strong correlation between the inhibitory activity of these compounds and the steric and electrostatic fields around them. CoMSIA models with considerable internal as well as external predictive ability were obtained. A poor correlation obtained with hydrophobic field indicates that the binding of thiazolothiazepines to HIV-1 integrase is mainly enthalpic in nature. Further the most active compound of the series was docked into the active site using the crystal structure of integrase. The binding site was formed by the amino acid residues 64-67, 116, 148, 151-152, 155-156, and 159. The comparison of coefficient contour maps with the steric and electrostatic properties of the receptor shows high level of compatibility.