The 3D structures of all molecules studied in the investigations reported here were generated by the 3D structure generator CORINA - and used without further optimization. Partial atomic charges were calculated by the PEOE (Partial Equalization of Orbital Electronegativity) method  and its extension to conjugated systems . Residual electronegativity values were also obtained by the above two procedures  by considering the charge dependence of electronegativities . The method for the calculation of atom polarizabilities has been published in reference . These methods are collected in the program package PETRA (Parameter Estimation for the Treatment of Reactivity Applications) .
The molecular electrostatic potential was obtained in a classical manner by moving a point charge on the molecular surface and calculating the potential according to Coulombs law from the partial atomic charges . Any molecular surface can be taken into account; in most cases, we used the van der Waals surface.
The Kohonen neural networks were generated and analyzed by the Kohonen map simulator KMAP . The study of the benzodiazepine and dopamine dataset was performed with an implementation of a Kohonen network on a massively parallel computer, MasPar .
In many studies reported here, the same dataset was used: 31 steroids binding to the corticosteroid binding globulin (CBG) receptor  and for which affinity data were available in the literature -. This dataset was chosen because it had been studied with other methods . Quite intentionally the same dataset of CBG steroids is used again and again, in order to render the various methods comparable and show which features they emphasize.