The reverse of the 'repair' reaction of thiols: H-abstraction at carbon by thiyl radicals.

SummaryThiyl radicals (RS·) formed by the reaction of radiolytically generated OH radicals with thiols, e.g. 1,4-dithiothreitol (DTT), react with cis- and trans-2,5-dimethyltetrahydrofuran by abstracting an H atom in the α-position to the ether function (k ≈ 5 × 103 dm3 mol−1 s−1). The so-formed planar ether radical is ‘repaired’ by the thiol (k = 6 × 108 dm3 mol−1 s−1) thereby regenerating a cis- or trans-2,5-dimethyltetrahydrofuran molecule. In this reaction a thiyl radical is reproduced. Thus trans-2,5-Me2THF from cis-2,5-Me2THF and vice versa are formed in a chain reaction: at a dose rate of 2·8 × 10−3 Gy s−1 and a trans-2,5-Me2THF concentration of 1 × 10−2 mol dm−3 using DTT as the thiol, G(cis-2 5-Me2THF) = 160 has been found. The chain reaction is very sensitive to impurities and also to disulphides such as those radiolytically formed. 2,5-Me2THF can be regarded as a model for the sugar moiety of DNA where the C(4′)-radical is known to lead to DNA strand breakage. The possible role of cellular thio...