Cationic liposomes enhanced firefly bioluminescent assay of adenosine 5'-triphosphate disodium salt

Cationic liposomes containing stearylamine enhanced the intensity of maximum light emission from the firefly luciferin-luciferase reaction with ATP in the range of 1.0 pM up to 5.5 nM. In contrast, the bioluminescent intensities in the presence of anionic and zwitterionic liposomes were about the same as those in water alone. The detection limit for ATP in the presence of cationic liposomes was 1.0 pM in aqueous ATP standard solutions. The sensitivity for ATP was improved by a factor of five times compared to that in water alone. The method was applied to the determination of ATP in Escherichia coli extracts. The sensitivity threshold was presumed to be 340 cells ml-1.