Topological indices are used for example in the development of quantitative structure-activity relationships (QSARs) in which the biological activity or other properties of molecules are correlated with their chemical structure.
[2] Topological descriptors are derived from hydrogen-suppressed molecular graphs, in which the atoms are represented by vertices and the bonds by edges.
[8][9] The extended topochemical atom (ETA)[10] indices have been developed based on refinement of TAU descriptors.
[11] QSARs represent predictive models derived from application of statistical tools correlating biological activity (including desirable therapeutic effect and undesirable side effects) of chemicals (drugs/toxicants/environmental pollutants) with descriptors representative of molecular structure and/or properties.
QSARs are being applied in many disciplines for example risk assessment, toxicity prediction, and regulatory decisions[13] in addition to drug discovery and lead optimization.