Molecular similarity tailored approach

In this chapter, we will discuss the utihty of HiQSAR studies using these five classes of descriptors. We will also show the utility of molecular similarity and our recently developed tailored similarity approach in the clustering of chemical libraries and selection of analogs. 

In most cases, separation and purification via crystallization are highly selective due to the fact that molecular recognition process at the crystal-solution interface acts in such a way as to select the host molecules and reject impurities. However, sometimes the solute and impurity molecules are not discriminated at certain crystal faces, especially when the impurity has many of the structural and chemical characteristics of the primary solute but differs only in some specific way. A systematic approach toward understanding the effects of such impurities on crystal growth has been developed using the concept of tailor-made additives (Weissbuch et al. 2003). These additives are structurally similar to the solute molecules and are basically composed of two moieties. The first, known as the binder, has a similar structure (and stereochemistry) to that of the substrate molecule on the crystal surface where it adsorbs. The second, referred to as the perturber, is modified when compared with the substrate molecule and thus hinders the attachment of the oncoming solute molecules to the crystal surface. Several classic examples in the literature highlight this type of interaction mechanism in molecular crystals. 

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