Permanent waving, of hair

The desire of individuals to improve the natural appearance of their hair can be dated back to ancient Egyptian and Greco-Roman societies. Such dissatisfaction continues to be the driving factor in the development of 

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The loss of structure by a protein is called denaturation. This structural change may be a loss of quaternary, tertiary, or secondary structure it may also be degradation of the primary structure by cleavage of the peptide bonds. Even mild heating can cause irreversible denaturation. When we cook an egg, the protein called albumen denatures into a white mass. The permanent waving of hair, which consists primarily of long a helices of the protein keratin, is a result of partial denaturation. 

A practical application of the chemistry of disulfide bonds is permanent waving of hair, as summarized in Fig. 22.26. The S—S linkages in the protein of hair are broken by treatment with a reducing agent. The hair is then set in curlers to change the tertiary protein structure to the desired shape. Then treatment with an oxidizing agent causes new S—S bonds to form, which allow the hair protein to retain the new structure. 

Problem 20.67. Permanent waving of hair involves the treatment of the hair with a reducing agent, placing the hair in curlers, and treating it with an oxidizing agent. Explain the chemistry involved. 

Describe how the "permanent waving" of hair is based on the chemistry of the amino acid cysteine and how it influences the tertiary structure of the proteins in the hair. 

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