Graphic Markush structure search systems

A structure search of chemical substances can be performed in the chemical structure databases. The structure query can be input using a graphical structure editor. The following search methods are possible, depending on the type of structure database. The structure search capabilities depend on the software system. Here, the focus is on the implementation of STN International exact structure search, family search, substructure search, similarity search, generic (Markush) search, and reaction search. 

QUESTEL and STN are the only hosts providing the graphic structure search using the Generic DARC System. Under the same command mode Derwent s Markush Dare file, containing the Markush structures is available. Regrettably, there is no nomenclature file text on QUESTEL which would allow searches for substance names und molecular formulae. 

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