RADICAL-INDUCED OXIDATION OF DITHIOTHREITOL IN ACIDIC OXYGENATED AQUEOUS-SOLUTION - A CHAIN-REACTION

Sulfur-centered radicals derived from dithiothreitol (DTT) have been g enerated radiolytically in aqueous solution in the neutral to acid pH range. In the presence of O-2, these are eventually transformed by a c hain reaction into dihydroxydithiane (ox-DTT) and H2O2. In acid soluti on, the chain character of the reaction becomes more pronounced with d ecreasing pH. The radiolytic yield of the products (G value) also depe nds on the DTT concentration and the dose rate. The HO2. radical carri es the chain, abstracting an H atom from the DTT molecule (k = 120 dm( 3) mol(-1) s(-1)), while its conjugated base, the O-2(.-) radical (pK( a)(HO2.) = 4.8), does not react with DTT. The chain is continued when the DTT-derived radicals react with O-2, yielding ox-DTT and HO2. radi cals. The self-terminationof the HO2./O-2(.-) radicals breaks the chai n.