Analysis of the maximum common substructure (MCS) allows finding a small structural difference between molecules with different types of activity. All the molecules shown in Figure for LasR DS were reported by O'Reilly and collaborators , they have a triphenyl scaffold showing the activity related to a specific ring substitution, the inactive molecule is ortho and meta disubstituted by fluorine in the first ring, the agonist and antagonist are monosubstituted in the ortho position by the chlorine in the first ring, but the antagonist is also monosubstituted in the para position in the third ring. These substitutions can change the inductive effect generating different interactions in the active site .