ABSTRACT
The Free-Wilson model is a simple and efficient method for the quantitative description of structure-biological activity relationships for molecules. It is the only numerical method which directly relates structural features with biological properties, in contrast to Hansch analysis, where physical-chemical properties are correlated with biological activity expressed as numerical values. The Free-Wilson model can help understand and interpret substituent effects. Vital to the development of the main idea of this model was the concept of the receptor site. According to this concept, biological activity depends on the recognition of a bioactive substrate (BAS) by a receptor site, followed by the binding of the BAS to the receptor site. Many applications of Free-Wilson and Hansch analysis confirm the theory that group contributions are additive for the total biological activity. Still, there are other effects causing deviations from the additive concept.
