Substructure subgraph isomorphism

The refinement procedure utilises the fact that if some query node Q(X) has another node Q(fV) at some specific distance ) ( and/or angle), and if some database node D(Z) matches with Q(W), then there must also be some node D(Y) at the appropriate distance(s) from D(Z) which matches with Q(X) this is a necessary, but not sufficient, condition for a subgraph isomorphism to be present (except in the limiting case of all the query nodes having been matched, when the condition is both necessary and sufficient). The refinement procedure is called before each possible assignment of a database node to a query node and the matched substructure is increased by one node if, and only if, the condition holds for all nodes W, X, Y and Z. The basic algorithm terminates once a match has been detected or until a mismatch has been confirmed [70] it is easy to extend the algorithm to enable the detection of all matches between a query pattern and a database structure, as is required for applications such as those discussed here. 

Substructure Search. Application of subgraph isomorphism" search to chemical structures. This consists of finding a particular arrangement of atoms and bonds as they are embedded in a chemical structure. The arrangement being searched for is termed the query substructure, the structures being searched are termed the candidates, and any particular structure in that set is termed a target structure. If the query substructure is... 

The substructure search, using standard subgraph isomorphism techniques , is used not only to confirm the presence of the required functional groups but also to identify all possible candidates for the key centres. This is used in the final stage of a search conformation regeneration. 

Our current work involves the use of the DAP for the implementation of UUmann s subgraph isomorphism algorithm, which has been shown to provide a highly efficient mechanism for substructure searching in files of both 2-D and 3-D chemical structures . 

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