ON THE USE OF THE QUENCHING OF LUMINOL LUMINESCENCE TO EVALUATE SOD ACTIVITY

Addition of horseradish peroxidase to a luminol solution (pH = 9.4) pr oduces a burst of light followed by a steady luminescence that lasts f or several minutes. This steady-state luminescence is readily quenched by SOD, with a Q1/2 concentration (the additive concentration needed to decrease by one-half the emitted luminescence intensity) of c.a. 4 ng/ml (14 mU/ml). The luminescence intensity decrease can then be empl oyed to evaluate SOD activity in SOD-containing samples. However, the light intensity can also be quenched by additives, such as Trolox, tha t are able to trap luminol-derived intermediates. It is proposed that double quenching experiments must be performed in order to be able to relate the observed effect of an additive to its SOD-like activity.