Thioglycolic acid reaction with hair

Methionine sulfone is presumably formed by reaction of the neutralizer with methionine residues thioacetylated lyine is probably formed by reaction of lysine with thioglycolide impurity in the thioglycolic acid [1]. The mixed disulfide is presumably formed by displacement of thioglycolate on the cystine residues in hair. One might also expect to find trace quantities of methionine sulfoxide in hair however, to date it has not been reported. 

A novel displacement reaction in permanent-waving involves treating reduced hair with polyoxyethylene esters of thioglycolic acid (MW 550-750) described recently by Salce et al. [3]. These esters are reported to bind to the fibers by displacement of reduced disulfide in hair on the ester linkage of the additive resulting in the formation of mixed disulfides, producing more hydrophobic hair fibers and improvement in the curl relaxation due to the increased hydrophobicity. 

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