Molecular Similarity and QSAR

2 Molecular Similarity and QSAR. - In a first contribution on the design of a practical, fast and reliable molecular similarity index Popelier107 proposed a measure operating in an abstract space spanned by properties evaluated at BCPs, called BCP space. Molecules are believed to be represented compactly and reliably in BCP space, as this space extracts the relevant information from the molecular ab initio wave functions. Typical problems of continuous quantum similarity measures are hereby avoided. The practical use of this novel method is adequately illustrated via the Hammett equation for para- and me/a-substituted benzoic acids. On the basis of the author s definition of distances between molecules in BCP space, the experimental sequence of acidities determined by the well-known a constant of a set of substituted congeners is reproduced. Moreover, the approach points out where the common reactive centre of the molecules is. The generality and feasibility of this method will enable predictions in medically related Quantitative Structure Activity Relationships (QSAR). This contribution combines the historically disparate fields of molecular similarity and QSAR. 

In a second contribution on quantum molecular similarity O Brien and Popelier108 investigate the relation between properties in BCP space and bond 

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Santos-Filho, O.A., Hopfinger, A.J. and Zheng, T. (2004) Characterization of skin penetration processes of organic molecules using molecular similarity and QSAR analysis. Mol. Pharm., 1, 466-476. 

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