Sulfhydryl radical (HS /S ): a contender for the isomerization of double bonds in membrane lipids

Some trans fatty acid residues found in living organisms can only be formed through an endogenous transformation of the naturally occurring cis structures, and their presence has been correlated with radical stress produced during physiological and pathological processes.[1-3] Diffusible thiyl radicals were deduced to be the species responsible for this isomerization on the basis of biomimetic models.[4-6] For example, methanethiyl radicals (CH3SC) produced by the reductive modification of methionine residues promote the isomerization extremely efficiently.[7-9] Nitrogen dioxide (NO2C) has also been suggested as an isomerizing species in a biological milieu;[2] however, it seems doubtful that NO2C really functions in this way