Type I and type II photosensitization by the antibacterial drug nalidixic acid. A laser flash photolysis study.
The 355 nm laser flash photolysis of nalidixic acid at pH 9.2 leads to the formation of the nalidixate anion triplet state (absorption lambda max = 620 nm; 5700 less than or equal to epsilon T less than or equal to 9000 M-1cm-1; 0.6 less than or equal to phi T less than or equal to 1). The first order triplet state decay (kT = 7.7 x 10(3) s-1) is accompanied by a diffusion controlled triplet-triplet annihilation. Oxygen efficiently quenches the triplet state (k = 3.2 x 10(9) M-1s-1). The nalidixate radical dianion (absorption lambda max = 650 nm; epsilon = 3000 M-1cm-1) is produced by the diffusion controlled reductive quenching of the triplet state by tryptophan and tyrosine. The superoxide anion (O2-.) is produced by diffusion controlled reaction of the radical dianion with oxygen. The O2-. is characterized by its reactions with ferricytochrome c and superoxide dismutase. The physiological form of nalidixic acid is thus a good Type I and Type II photosensitizer.
Vermeersch
G
G
Laboratoire de Physique, UA CNRS 351, Faculté de Pharmacie, Université de Lille II, France.
Ronfard-Haret
J C
JC
Bazin
M
M
Carillet
V
V
Morliere
P
P
Santus
R
R
D000838:Anions / Q000737:chemistry; D003574:Cytochrome c Group / Q000737:chemistry; D005609:Free Radicals / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007834:Lasers; D009268:Nalidixic Acid / Q000494:pharmacology*; D010084:Oxidation-Reduction; D010782:Photolysis; D013053:Spectrophotometry
D000838:Anions; D003574:Cytochrome c Group; D005609:Free Radicals; D009268:Nalidixic Acid