No abstract

No abstract

The activity of 72 1,4-dihydropyridines as calcium channel antagonists was examined. The simplified molecular input-line entry system (SMILES) was used as representation of the molecular structure of the calcium channel antagonists. Quantitative structure-activity relationships (QSARs) were developed using CORAL software (http://www.insilico.eu/CORAL) for four random splits of the data into the training and test sets. Using the Monte Carlo method, the CORAL software generated the optimal descriptors for one-variable models. The reproducibility of each model was tested performing three runs of the Monte Carlo optimization. The obtained results reveal good predictive potential of the applied approach: The correlation coefficients (r(2) ) for the test sets of the four random splits are 0.9571, 0.9644, 0.9836, and 0.9444.

The stability of metal-humate complexes is an important factor determining and predicting speciation, mobility and bioavailability of heavy metals in the environment. A comparative investigation of the complexation of Cu(II) and Pb(II) with humic acid and humic-like ligands, such as benzoic and salicylic acid, was performed. The analysis was realized at pH 4.0, a temperature of 25 °C and at an ionic strength of 0.01 mol dm -3 (NaCl) using the Schubert ion-exchange method and its modified form. The stability constants were calculated from the experimental data by the Schubert method for complexes with benzoic and humic acid. A modified Schubert method was used for the determination of the stability constants of the complexes with salicylic acid. It was found that Cu(II) and Pb(II) form mononuclear complexes with benzoic and humic acid while with salicylic acid both metals form polynuclear complexes. The results indicate that Pb(II) has a higher binding ability than Cu(II) to all the investigated ligands. The Cu(II)-salicylate and Pb(II)-salicylate complexes showed noticeable higher stability constants compared with their complexes with humic acid, while the stabilities of the complexes with benzoic acid differed less. Salicylic and benzoic acids as humic-like ligands can be used for setting the range of stability constants of humic complexes with Cu(II) and Pb(II).

No abstract