Editing Quantitative structure–activity relationship (section)

=== Biological ===

The biological activity of molecules is usually measured in [[assay]]s to establish the level of inhibition of particular [[signal transduction]] or [[metabolic pathway]]s. [[Drug discovery]] often involves the use of QSAR to identify chemical structures that could have good inhibitory effects on specific [[biological target|targets]] and have low [[toxicity]] (non-specific activity).  Of special interest is the prediction of [[partition coefficient]] log ''P'', which is an important measure used in identifying "[[druglikeness]]" according to [[Lipinski's Rule of Five]].{{cn|date=March 2024}}

While many quantitative structure activity relationship analyses involve the interactions of a family of molecules with an [[enzyme]] or [[receptor (biochemistry)|receptor]] binding site, QSAR can also be used to study the interactions between the [[structural domain]]s of proteins. Protein-protein interactions can be quantitatively analyzed for structural variations resulted from [[site-directed mutagenesis]].<ref name="pmid12668435">{{cite journal | vauthors = Freyhult EK, Andersson K, Gustafsson MG | title = Structural modeling extends QSAR analysis of antibody-lysozyme interactions to 3D-QSAR | journal = Biophysical Journal | volume = 84 | issue = 4 | pages = 2264–72 | date = Apr 2003 | pmid = 12668435 | pmc = 1302793 | doi = 10.1016/S0006-3495(03)75032-2 | bibcode = 2003BpJ....84.2264F }}</ref>

It is part of the [[machine learning]] method to reduce the risk for a SAR paradox, especially taking into account that only a finite amount of data is available (see also [[Minimum-variance unbiased estimator|MVUE]]). In general, all QSAR problems can be divided into [[Coding (social sciences)|coding]]<ref name="isbn3-527-29913-0">{{cite book | vauthors = Timmerman H, Todeschini R, Consonni V, Mannhold R, Kubinyi H | title = Handbook of Molecular Descriptors | publisher = Wiley-VCH | location = Weinheim | year = 2002 | isbn = 978-3-527-29913-3 }}</ref>
and [[learning]].<ref name="isbn0-471-05669-3">{{cite book |vauthors=Duda RO, Hart PW, Stork DG | title = Pattern classification | publisher = John Wiley & Sons | location = Chichester | year = 2001 | isbn = 978-0-471-05669-0 }}</ref>