Hair fibers structural alteration

Unaltered human hair is hair that has not been chemically modified by treatment with bleaches, permanent waves, straighteners, or hair dyes. Numerous publications [6,12-27] describe results of the amino acid analysis of unaltered human hair. Table 2-1 depicts the structures for 21 amino acids that have been identified in human hair. Cysteic acid and other amino acids, derived from those amino acids of Table 2-1, are also present in either weathered or cosmetically altered hair, see Table 2-2. Table 2-3 summarizes results from several sources describing quantitative whole-fiber analyses of these 21 amino acids. These same amino acids are classified according to functional group in Table 2-4. 

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