Alternating reactivity of free radicals coordinated to chelated transition metals and to hemoproteins

Abstract

The mean lifetime of free radicals increases by coordination to transition metals of chelates including hemoproteins (hemoglobin, cytochrome c, catalase), when the radical generation proceeds in non-polar media in temperature range of physiological ones (290-310 K). In polar media (water, methyl- or ethylalcohol, pyridine), or in the presence of effective ligating agents (e.g. bases of nucleic acids), or at slightly elevated temperatures the intermediately stabilized oxygen centred radicals are liberated from the complex and the original high reactivity of the free radical is renewed. It is assumed that in this way sterically unhindered free radicals derived from chemical carcinogens with alternating reactivity could be transported through the microheterogeneous cell matrix.