DEOXYRIBOSE DEGRADATION CATALYZED BY FE(III)-EDTA - KINETIC ASPECTS AND POTENTIAL USEFULNESS FOR SUBMICROMOLAR IRON MEASUREMENTS

Iron ions play a central role in .OH radicals formation and induction of oxidative stress in living organisms. Iron-catalyzed .OH radical fo rmation degrades deoxyribose to thiobarbituric acid reactive substance s (TBA-RS). This paper analyzes kinetic properties of the Fe(III)-EDTA -catalyzed deoxyribose degradation in the presence of ascorbate. The y ield of TBA-RS formation in the presence of EDTA was 4-fold higher tha n in its absence, contrasting with results reported elsewhere, Cu(II)- EDTA and Fe(III)-citrate were unable to catalyze deoxyribose degradati on. The dependence on deoxyribose concentration was fitted to a Linewe aver Burk-like plot and it was calculated that approximately 4.5 mM de oxyribose scavenged half of the .OH radicals formed. The data for Fe(I II)-EDTA concentration dependence could also be fitted to a rectangula r hyperbolic function. This function was linear up to 1 mu M added FeC l3 and this property could be utilized as an assay for the estimation of submicromolar iron concentrations. Submicromolar concentrations of iron could induce measurable yields of TBA-RS. Differences of as littl e as 0.1 mu M Fe(III)-EDTA could be reproducibly detected under optimu m experimental conditions, above a consistent background absorbance th at was equivalent to 0.35 +/- 0.05 mu M Fe(III)-EDTA and represented c ontaminating iron in the reactants that could not be removed with Chel ex-100. The low method determination limit makes the deoxyribose degra dation reaction potentially useful as a new, highly sensitive and cost effective assay for iron quantification.