Intense chemiluminescence from the oxidation of luminol with mchloroperoxybenzoic acid catalyzed by Mn(III)-microperoxidase

We have studied the chemiluminescence (CL) of luminol oxidation with mchloroperoxybenzoic acid (mCPBA) or hydrogen peroxide (H2O2) catalyzed by Mn(III)microperoxidase 8 (Mn(III)-MP8) using the stopped-flow technique. The CL involving Mn(III)-MP8 is two to three times as intense as that of the corresponding Fe(III)-MP8, while using mCPBA in place of H2O2 as the oxidant enhances the CL by 12¯18-fold at the optimum pH (~12). The rapid formation of the intermediate, O=Mn(IV)-MP8, upon addition of mCPBA to Mn(III)-MP8 will lead to a fast CL cycle. This in turn, will produce an intense CL of very short duration. The ratio of the peak CL intensity (mCPBA:H2O2) for the Mn(III)-MP8 system remains essentially constant (~20) regardless of the pH and the concentrations of oxidant and luminol used, provided that the supply of the oxidant and luminol is sufficient. The novel use of Mn(III)MP8/mCPBA for the CL of luminol oxidation will have a great analytical potential for very sensitive assays.