They are generated by hydrogen-atom abstraction from thiols using initiators such as AIBN:[2] Thiyl radicals are also invoked as intermediates in some biochemical reactions.
[4] Other substrates of thiyl radicals include other proteins (k = 1.4 x 105 M−1s−1),[5] monounsaturated fatty acids (MUFAs) (k = 1.6 x 105 M−1s−1),[6] and ubiquinone (k = 2.5 x 103 M−1s−1).
Interestingly, the addition of lipophilic thiols in cell culture or administration to C. elegans accelerated lipid peroxidation at the same initiation rate, caused damage to membrane proteins, and was associated with a decline in polyunsaturated fatty acids (PUFAs) and a shortened lifespan.
Nonetheless, both compounds have high rate constants for their reaction with peroxyl radicals, highlighting their evolutionary importance as scavengers.
[11][12][13] Isoprenoid polyenes, such as carotenoids or lycopene, exhibit very high rate constants regarding thiyl radicals (up to 109 M−1s−1).