Notes: 2-nonyl-3-hydroxy-4-Quinolone-d4 is intended for use as an internal standard for the quantification of 2-nonyl-3-hydroxy-4-quinolone (Item No. 9002699) by GC- or LC-MS. 2-nonyl-3-hydroxy-4-Quinolone is a bacterial quorum-sensing signal molecule produced by P. aeruginosa.{65266} It activates a biosensor for the P. aeruginosa gene pqsA, which encodes the first enzyme in the P. aeruginosa biosynthesis of the bacterial quorum-sensing signal molecule 2-heptyl-3-hydroxy-4-quinolone (Item No. 29186), in a concentration-dependent manner.{65265}