Cystine in wool

Swan153 demonstrated that sulfite or bisulfite ion reacts with sulfhydryl (SH) groups of cystine in wool protein, reducing the disulfide linkage and giving a protein fraction (P ) having one cysteine SH and a second protein (P ) on which a S-sulfo derivative of the cysteine moiety has been formed ... 

Sunlight and ultraviolet light have been shown to decrease the 15% index (in distilled water). This effect relates to the total radiation on the hair [58]. These findings were interpreted as photochemical degradation of disulfide bonds and have been confirmed by Robbins and Kelly [59]. This work involved analysis of amino acids of both proximal and distal ends of human hair where a significantly larger amount of cysteic acid and a significantly smaller amount of cystine were found in distal ends. Harris and Smith [60] have provided evidence for ultraviolet disruption of cystine in wool. 

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