Ilangovan et al. reported the compounds associated with biological activity for PqsR DS in 2013 . These compounds differ from each other only in the substitution of nitrogen in the quinazoline ring: the inactive compound has a hydroxyl, the agonist has ethyl, and the antagonist has an amine; finding the association of biological activity related to several acceptors and donors of hydrogen bonds in this position. For molecules of this analysis linked to RhlR DS, it is possible to establish a steric effect in the active site with the type of activity, as is showed in Figure . This analysis allows establishing for these scaffolds a mechanism of action cliffs (MOA-cliffs) .