Two-dimensional fragment descriptors

Dixon, S.L. and Koehler, R.T. (1999) The hidden component of size in two-dimensional fragment descriptors side effects on sampling in bioactive libraries. /. Med. Chem., 42, 2887-2900. 

Third, there is a need to be able to integrate the basic searching facilities with the more sophisticated routines for three-dimensional structure matching that have been described in this review. ° ° ° An obvious related area is the use of three-dimensional structures to derive descriptors for quantitative structure-aaivity relationships. This could be either an extension of the wide use of two-dimensional fragments for substructural analysis stud-ies 8 8i to three-dimensional fragments, or the automatic generation of data for a prediction of potency, e.g., the recent work of Cramer et al. ° ... 

Two-dimensional descriptors are normally represented by linear bit strings indicating the presence or the absence of some properties in the molecule Examples include structural fragments (structural keys, 40, 41, 36), specific atom paths with predefined... 

Fragment descriptors Both two-dimensional (2-D) connection tables for the molecular structures involved, as well as three-dimensional (3-D) information for these structures may generate a variety of fragment descriptors for substructure search systems (for a review of substructure search systems, see Chen ). Active research continues to be carried out in this field, and the interested reader can peruse the review by Downs for more information. 

The importance of methods to predict log P from chemical structure was described in Chapter 14, which is focused on fragment- and atom-based approaches. In this chapter property-based approaches are reviewed, which comprise two main categories (i) methods that use three-dimensional (3D) structure representation and (ii) methods that are based on topological descriptors. 

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