Lucigenin: Redox potential in aqueous media and redox cycling with O-2(-) production

The use of lucigenin luminescence as a measure of [O-2(-)] has been questio ned because lucigenin has been shown to be capable of mediating the product ion of O-2(-). This being the case, lucigenin can signal the presence of O- 2(-) even in systems not producing it in the absence of lucigenin, The redu ction potential of lucigenin should be in accord with its ability to mediat e O-2(-) production; but it has not heretofore been measured in aqueous med ia. The problems facing such measurement are the insolubility of the divale ntly reduced form, which deposits on the electrode, and the slow conformati onal transition that follows the second electron transfer and which interfe res with reversibility, We have now used rapid scan cyclic voltammetry to d etermine that the reduction potential for lucigenin is -0.14 +/- 0.02 V ver sus the normal hydrogen electrode. This value applies to both the first and the second electron transfers to lucigenin and it is in accord with the fa cile mediation of O-2(-) production by this compound. (C) 2000 Academic Pre ss.