The pleated sheet, a new layer configuration of polypeptide chains.

For many years it has been assumed that in silk fibroin, stretched hair and muscle, and other proteins with the ,3-keratin structure the polypeptide chains are extended to nearly their maximum length, about 3.6 A per residue, and during the last decade it has been assumed also that the chains form lateral hydrogen bonds with adjacent chains, which have the opposite orientation. A hydrogen-bonded layer of this sort is represented diagrammatically in figure l.1-4