Radical-Induced Oxidation of Dithiothreitol in Acidic Oxygenated Aqueous Solution: A Chain Reaction

Sulfur-centered radicals derived from dithiothreitol (DTT) have been generated radiolytically in aqueous solution in the neutral to acid pH range. In the presence of O2, these are eventually transformed by a chain reaction into dihydroxydithiane (ox-DTT) and H2O2. In acid solution, the chain character of the reaction becomes more pronounced with decreasing pH. The radiolytic yield of the products (G value) also depends on the DTT concentration and the dose rate. The HO2• radical carries the chain, abstracting an H atom from the DTT molecule (k = 120 dm3 mol-1 s-1), while its conjugated base, the O2•- radical (pKa(HO2•) = 4.8), does not react with DTT. The chain is continued when the DTT-derived radicals react with O2, yielding ox-DTT and HO2• radicals. The self-termination of the HO2•/O2•- radicals breaks the chain.