Radiolytic reduction of ceric ions in water DMSO mixtures and radioprotection

Abstract

It is convenient to classify mechanisms of radioproteetion into those that involve fast radiation chemical processes and those in which the protection is the result of changes in the cell biochemistry. In the former, the added protectors have two principal effects: OH scavenging which reduces the radiosensitised damage and fast chemical repair processes involving hydrogen donation from the protector to the target radical. Typical of the first type of protector is dimethyl sulphoxide(DMSO)¹ because it is known to be a good OH scavenger (k_OH+DMSO =5×10⁹ mol⁻¹ s⁻¹. (ref. 2). We have attempted to establish the redox properties of the OH radical adduct³ as well as those of H₂O₂ or H and HO₂ radicals in water–DMSO mixtures. To this end we added to the solutions containing 0.5 M H₂SO₄, cerie ions at concentrations varying from 2.5 × 10⁻³ to 5 × 10⁻² M. The Ce⁴⁺ reduction yield was determined as a function of the DMSO content in the solution, by irradiating the mixture with γ rays, in the presence or absence of air. The details of the experimental procedure will be given elsewhere. We report here that the yields (G) are independent of the Ce⁴⁺ concentration in the range studied and of the presence or absence of air, and depend only on the DMSO concentration.