Abstract
Water soluble wool keratin was prepared by derivatization of disulfide (SS) bonds of cystine residues to carboxymethylalanyl disulfide (CMAD) groups. The solubilization reaction was carried out in 0.2 M thioglycolic acid aqueous solution under alkaline conditions (pH 11 - pH 13.5). CMAD wool keratin was successfully obtained even in the absence of urea and dithiodiglycolic acid. The solubilization reaction was performed by two stages, derivatization reaction including reduction step, oxidation step and oxidation reactions. The derivatization reaction was accelerated by increment of alkali concentration, however, hydrolysis of wool keratin occurred simultaneously at high alkaline concentration more than pH 13. Molecular degradation hardly occurred when reaction time was short, even pH 13 system. To investigate the prevention of hair damage, CMAD wool keratin was prepared at pH 13 for 12 h. It was added in permanent waving agent and the bleaching and permanent waving (B&P) treatments were carried out. Human hair was damaged remarkably by repetition of B&P treatments. However, cuticle layers of treated hair using CMAD wool keratin were hardly damaged even if the treatment was repeated for 3 times. CMAD wool keratin is useful for prevention of hair damage.
