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ChemOffice.Com - CambridgeSoft

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Administrator<br />

For the two compounds above, the Tanimoto<br />

coefficient is 17/30, or about 57%. This is not very<br />

similar. Although ChemFinder will allow you to<br />

specify any Tanimoto value down to 0%, for most<br />

cases you will likely be looking for compounds that<br />

have Tanimoto coefficients of 90% or higher.<br />

Substructure<br />

Similarity<br />

Unlike full structure similarity, substructure<br />

similarity is not commutative: you are comparing a<br />

portion of one structure against the entire other<br />

structure, and so it does matter which you compare<br />

to which. In considering substructure similarity,<br />

ChemFinder finds what percentage of descriptors<br />

in the query are also present in the target.<br />

This value will always be at least as large as the<br />

complete-structure Tanimoto coefficient for the<br />

same two compounds, and usually it will be larger.<br />

The two compounds above are 17/23, or about<br />

74% similar by substructure similarity. For a given<br />

coefficient value, a substructure similarity search<br />

will always return all of the hits in a full structure<br />

similarity search, and will often return additional<br />

ones as well.<br />

690• Similarity Rules <strong>CambridgeSoft</strong><br />

Substructure Similarity

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