Efficient singlet oxygen inactivation of firefly luciferase

Firefly luciferase is inactivated by singlet oxygen at near diffusion controlled rates, 1.9 X 10(9) M-1 s-1, based on direct comparison with the oxidation of L-histidine. The inactivation kinetics are multiphasic. Inactivation is inhibitable by NaN3. Surface-separated-sensitizer (SSS) system in which singlet oxygen is produced above an air gap separating the reaction solution from the Rose Bengal sensitizer, ensuring only Type II reactions, was compared with a Sensitox II system in which the polymer bound Rose Bengal is contained in the reaction solution and both Type I and Type II reactions can occur. A slight stabilization is afforded by MgSO4.