The Structure and Chemistry of Human Hair 2 sunlight, even for hair of a living subject, is best avoided because it causes considerable chemical damage, leaving it susceptible to subsequent mechanical degradation. In the case of archaeological hairs, sunlight exposure renders them vulnerable to microbiological attack. By way of example, the fine physical state of the hair of English author Jane Austen was undoubtedly due to the protection of her hair from sunlight exposure by the wearing of a bonnet.5 Chemical Composition Table 1 discloses that natural white hair is composed mainly of protein and that significant amounts of protein-bound sulphur are present. Lipids are mainly associated with the cell membrane complexes that separate the hair’s constituent hardened cells from each other. Zinc is present at a relatively high level and is a leftover from the enzymatic processes in the follicle responsible for the hardening of the fiber. Black hair contains as much as 4% by weight of the particulate pigment, melanin. Table 1. Overall composition of human head hair Component Approx. content in weight % dry hair Protein 91 Lipid 4 Sugars 1.0 Protein-bound sulphur 4.7 Ash 0.5 Zinc 200 ppm Table 2 shows the amino acid composition of hair obtained by regular amino acid analysis following acid hydrolysis6. For later convenience the 3-letter and 1-letter codes for the amino acids are included in this table readers are advised to bear them in mind. Asparagine and glutamine are the amides of aspartic acid and glutamic acid, respectively. The amounts of these in the hair cannot be determined following acid hydrolysis but are included in the
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