Figure 1.

Molecules in this study. In all, R¹ is an H atom. In Pseudomonas quinolone signal (PQS), 2-heptyl-4-hydroxyquinoline (HHQ), 2-heptyl-3-chloro-4(1H)-quinolone (3Cl-PQS) and 2-heptyl-3-amino-4(1H)-quinolone (3NH₂-PQS) R² is an alkyl side chain, C₇H₁₅. In C1-PQS, C3-PQS, C5-PQS, and C9-PQS R² is an alkyl side chain of 1, 3, 5, and 9 carbon molecules, respectively. In PQS and HHQ, R³ is a hydroxyl group or an H atom, respectively. In 3Cl-PQS and 3NH₂-PQS, R³ is a chlorine or primary amine group, respectively.