Variations in the Proteins of Wool and Hair

Keratins are not materials of unique amino acid and protein composition. A wide range of compositions over which satisfactory structure-function is achieved has been found; for example the half-cystine content of wool falls in the range 8% to 15%, and that of tyrosine 2.3% to 4.6%. Variations in composition occur not only between fibres from different individuals of a species but also along the length of fibres from the one animal. Protein composition may be influenced by the genetic origin, nutritional status and physiological state of the animal.