Alpha-keratin keratin cell due to their effect on the various hydrogen bonds in the alpha-keratin network. Alpha-keratins proteins can be one of two types: type I or type II. There are 54 keratin genes in humans, 28 of which code for type I, and 26 for type II. Type I proteins are acidic, meaning they contain more acidic amino acids, such as aspartic acid, while type II proteins are basic, meaning they contain more basic amino acids, such as lysine. This differentiation is especially important in alpha-keratins because in the synthesis of its sub-unit dimer, the coiled coil, one protein coil
Collagen helix – this should not be confused with the right-handed alpha helix. These three left-handed helices are twisted together into a right-handed triple helix or "super helix", a cooperative quaternary structure stabilized by many hydrogen bonds. With type I collagen and possibly all fibrillar collagens, if not all collagens, each triple-helix associates into a right-handed super-super-coil referred to as the collagen microfibril. Each microfibril is interdigitated with its neighboring microfibrils to a degree that might suggest they are individually unstable, although within collagen fibrils, they are so well ordered as to be crystalline. A distinctive feature of collagen is the