QSARs were derived for 103 analogues of 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (HEPT), a potent inhibitor of the HIV-1 reverse transcriptase (RT). The activity of these compounds was investigated by means of multiple linear regression (MLR) and artificial neural network (ANN) techniques. Considering the relevant descriptors obtained from the MLR, a correlation coefficient of 0.92 (n = 95) was obtained with a 4-5-1 ANN model. The contribution of each descriptor to the structure-activity relationships was evaluated. The results showed that the anti-HIV activity of HEPT derivatives was strongly dependent on hydrophobic character and also steric factors of substituents.

Oxidative stress induced by nickel sulfide appears to cause loss of p16 and activation of MAP kinase signaling. These findings support the hypothesis of synergistic interactions between MAP kinase activation and p16 loss in carcinogenesis.

Structure-toxicity relationships were studied for a set of 47 insecticides by means of multiple linear regression (MLR) and artificial neural network (ANN). A model with three descriptors, including shape surface [S(R2)], hydrogen-bonding acceptors [HBA(R2)] and molar refraction [MR(R1)], showed good statistics both in the regression (r = 0.875, s = 0.417 and q2 = 0.675) and artificial neural network model with a configuration of [3-5-1] (r = 0.966, s = 0.200 and q2 = 0.647). The statistics for the prediction on toxicity [log LD50 (lethal dose 50, oral, rat)] in the test set of 20 organophosphorus insecticides derivatives is (r = 0.849, s = 0.435) and (r = 0.748, s = 0.576) for MLR and ANN respectively. The model descriptors indicate the importance of molar refraction and shape contributions toward toxicity of organophosphorus insecticides derivatives used in this study. This information is pertinent to the further design of new insecticides.