MadSci Network: Biochemistry

Re: Why is it not advisable to have hair bleached and permed at the same time?

Date: Fri Jan 30 12:59:23 1998
Posted By: Dick van Wassenaar, Grad student analytical PROTEIN Biochemist, Unilever Research laboratory
Area of science: Biochemistry
ID: 884602141.Bc

Dear Daphne,

To some extent you are right, but the chemistry is different from what you think.

During bleaching, the hydrogen peroxide oxidizes the cystine residues in the hair proteins; however, they are so strongly oxidized that they form CysSO3H [Cysteic acid]. This oxidized form of cysteine CANNOT be reduced anymore and therefore the bleaching effect lasts as long as the hair is there. Only newly grown hair will have the normal cysteines again.

During perming, on the other hand, the cystine [disulphide linked (-S-S-)] residues are reduced to the cysteine [free sulphydryl group (S-H)] form and these are [mildly] reoxidized again into new cystine [-S-S-] linked pairs. In this case one can speak of shuffling between and within polypeptide chains. Because of this shuffling, new curls are formed. Because the nature of these bonds are more sensitive to ‘natural’ reduction/oxidation, perming does not last as long as bleaching.

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