Consensus QSAR models estimating acute toxicity to aquatic organisms from different trophic levels: algae,Daphnia and fish

ABSTRACT

We report new consensus models estimating acute toxicity for algae, Daphnia and fish endpoints. We assembled a large collection of 3680 public unique compounds annotated by, at least, one experimental value for the given endpoint. Support Vector Machine models were internally and externally validated following the OECD principles. Reasonable predictive performances were achieved (RMSE_ext = 0.56–0.78) which are in line with those of state-of-the-art models. The known structural alerts are compared with analysis of the atomic contributions to these models obtained using the ISIDA/ColorAtom utility. A benchmarking against existing tools has been carried out on a set of compounds considered more representative and relevant for the chemical space of the current chemical industry. Our model scored one of the best accuracy and data coverage.

Nevertheless, industrial data performances were noticeably lower than those on public data, indicating that existing models fail to meet the industrial needs. Thus, final models were updated with the inclusion of new industrial compounds, extending the applicability domain and relevance for application in an industrial context. Generated models and collected public data are made freely available.     

Asymmetric radical polymerization and copolymerization of N‐(1‐phenyldibenzosuberyl)methacrylamide and its derivative leading to optically active helical polymers

N‐(1‐Phenyldibenzosuberyl)methacrylamide (PDBSMAM) and its derivative N‐[(4‐butylphenyl)dibenzosuberyl]methacrylamide (BuPDBSMAM) were synthesized and polymerized in the presence of (+)‐ and (?)‐menthols at different temperatures. The tacticity of the polymers was estimated to be nearly 100% isotactic from the ¹H NMR spectra of polymethacrylamides derived in D₂SO₄. Poly(PDBSMAM) was not soluble in the common organic solvents, and its circular dichroism spectrum in the solid state was similar to that of the optically active poly(1‐phenyldibenzosuberyl methacrylate) (poly(PDBSMA)) with a prevailing one‐handed helicity, indicating that the poly(PDBSMAM) also has a similar helicity. Poly(BuPDBSMAM) was optically active and soluble in THF and chloroform. Its optical activity was much higher than that of the poly[N‐(triphenylmethayl)methacrylamide], suggesting that one‐handed helicity may be more efficiently induced on the poly(BuPDBSMAM). The copolymerization of BuPDBSMAM with a small amount of optically active N‐[(R)‐(+)‐1‐(1‐naphthyl)ethyl]methacrylamide, particularly in the presence of (?)‐menthol, produced a polymer with a high optical activity. The prevailing helicity may also be efficiently induced. The chiroptical properties of the obtained polymers were studied in detail. The chiral recognition by the polymers was also evaluated. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1304–1315, 2007     

Efficient,Convenient and Mild Three Component Template Preparation and Characterization of Some New Schiff Base Complexes

A few kinds of novel Schiff base complexes have been prepared by three component reaction of the substituted hydroxyacetophenone with several aliphatic diamines and transition metals such as; Ni(II), Zn(II) and UO₂(II) under mild reaction conditions. The products have been afforded with excellent yields and appropriate reaction times. The structure of these ligands has been characterized by their IR, ¹H NMR, ¹³C NMR and MS spectral and physical data.     

Experimental analysis of current conduction through thermally grown SiO<Subscript>2</Subscript> on thick epitaxial 4H-SiC employing Poole-Frenkel mechanism

Electrical properties of SiO₂ grown on the Si-face of the epitaxial 4H-SiC substrate by wet thermal oxidation technique have been experimentally investigated in metal oxide-silicon carbide (MOSiC) structure with varying oxide thicknesses employing Poole-Frenkel (P-F) conduction mechanism. The quality of SiO₂ with increasing thickness in MOSiC structure has been analysed on the basis of variation in multiple oxide traps due to effective P-F conduction range. Validity of Poole-Frenkel conduction is established quantitatively employing electric field and the oxide thickness using forward I–V characteristics across MOSiC structures. From P-F conduction plot (ln(J/E) vs. E ^1/2), it is revealed that Poole-Frenkel conduction retains its validation after a fixed electric field range. The experimental methodology adopted is useful for the characterization of oxide films grown on 4H-SiC substrate.     

Photocatalytic activity of ZnO nanoparticles prepared via submerged arc discharge method

ZnO nanostructures were synthesized through arc discharge of zinc electrodes in deionized (DI) water. X-ray diffraction (XRD) analysis of the prepared nanostructures indicates formation of crystalline ZnO of hexagonal lattice structures. Transmission electron microscopy (TEM) images illustrate rod-like as well as semi spherical ZnO nanoparticles with 15–20 nm diameter range, which were formed during the discharge process with 5 A arc current. The average particle size was found to increase with the increasing arc current. X-ray photoelectron spectroscopy (XPS) analysis confirms formation of ZnO at the surface of the nanoparticles. Surface area of the sample prepared at 5 A arc current, measured by BET analysis, was 34 m²/g. Photodegradation of Rhodamine B (Rh. B) shows that the prepared samples at lower currents have a higher photocatalytic activity due to larger surface area and smaller particle size.