Molecular organization of avian epidermal structures

1. A number of differences in the phi-keratins have been shown to exist among various avian epidermal structures. 2. There is extensive electrophoretic heterogeneity within tissues and two elemental sizes of monomers. Feathers, natal and definitive down monomers have a weight of 10,500 dalton; scale, break and claw monomers approx 13,500 daltons. 3. Differences in the size of the monomers is due to the presence of an insoluble tryptic peptide high in Gly, Phe, Leu and Tyr. 4. Tissue differences in composition are related to structure and function.