The index of ideality of correlation: improvement of models for toxicity to algae.

Toxicity to algae is important characteristic of substances from ecologic point of view. The CORAL software ( http://www.insilico.eu/coral ) gives possibility to build up model of toxicity to algae using data on the molecular architecture and experimental toxicity, without additional data on physicochemical and/or biochemical parameters. Considerable improvement of the model is observed in the case of using the index of ideality of correlation (IIC) in the role of additional criterion of predictive potential. The IIC is calculated with using of the correlation coefficient between experimental and calculated values of endpoint for the calibration set, with taking into account the positive and negative dispersions between experimental and calculated values. The best model calculated with use the IIC is characterized (the validation set) by n = 50, r2 = 0.947, RMSE = 0.401 whereas, model calculated without use the IIC is characterized by n = 50, r2 = 0.805, and RMSE = 0.539. The suggested models are built up in accordance to five OECD principles.