Keratin

Keratin biomaterials have been in use for decades, yet they are seemingly new to the field. The hair follicle is not simply a tubular structure containing keratin protein. More precisely, it is a molecular composite, composed of several different types of keratins, carefully arranged by an inadequately understood process of self-assembly, that arranges itself into separate compartments, each containing a different composition and ultrastructure. The different types of keratin and keratin associated proteins (KAP), their physical arrangement relative to each other, covalent and non-covalent interactions, the composite nature of keratin fibers, different super-structural compartments (e.g. cortex, cuticle), relative reactivities toward processing reagents, and solution behavior of extracted molecules are all important considerations when designing a keratin extraction/purification protocol. The keratins found in hair are characterized primarily by their high cysteine content and extent of disulfide crosslinking. Oxidative sulfitolysis of keratin can be considered as a chemical hybrid between oxidation and reduction.