Chemical similarity molecular fingerprinting techniques

The fact that mass, infra-red, NMR and ultra-violet spectra and, to a certain extent, also chromatographic retention data can be considered as molecular fingerprints , forms the basis of most computerised library search systems. Retrieval methods for characteristic chemical data and techniques for the comparison of human fingerprints have similar elements the first step is to clean up the raw data, then in many cases a data reduction is carried out by selection of prominent features. Finally, there is the comparison of unknown and reference data patterns, which, for a useful result, requires a statistical correlation to be established. In this paper no attention will be paid to feature selection. 

In the previous chapter, we learnt the use of fingerprints for searching chemical structures. Of equal importance is the need for searching chemical reactions to estimate their similarity using computational tools. In this section, we will therefore learn how to use reaction fingerprints for searching in databases and online servers. Similar techniques are employed in both cases. Stractural properties that are present in the reaction are used for estimation of reaction similarity. Two reactions can be considered similar if their product side artd/or reactant side are similar. With this consideration, reaction sirrrilarity is reduced to molecular or 5irMctMro/ similarity. 

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