The alpha helix - a common folding pattern. He predicted the shape and size of the helix exactly as shown later by experimental studies on Keratin, a protein which is almost pure alpha-helix. The alpha helix has overlapping hydrogen bonds . As a result,some can be broken and the structure remains stable. Only when most all of them are broken, does the denatured protein unwind into a random coil configuration.
Hair consists of almost pure alpha-helix as the protein keratin.
Permanent waves and hair straightening chemicals are reducing agents which break disulfide bonds. The beta pleated sheet - another common structural feature of proteins. An example of almost pure beta pleated sheet is the protein which makes up silk. Hairpin turns, where the chain reverses direction, are constructed in particular ways- one of the two amino acids must be glycine to give room for the atoms to make the turn. The collagen helix - an unusual way to make a helical, structural, protein.