Superoxide, amine buffers and tetranitromethane: A novel free radical chain reaction

The amine buffer Tris slowly reduces tetranitromethane (TNM) to the nitrofo rm anion in a non-accelerating reaction. The amine buffers HEPES and MOPS a lso (slowly) react with TNM but the dialkylaminoalkyl radicals formed from these two buffers undergo further reactions resulting in a rapid, accelerat ing, free radical chain process whereby the amine is oxidized and TNM reduc ed. The chemical functionality in any reaction component, not necessarily t he buffer, required for this radical chain mechanism is >N-CH<. In the pres ence of such groups, the quantification of superoxide by TNM is impossible.