Secondary Structure. The amino acid side groups are not the only portions of proteins that form hydrogen bonds. Two patterns of H bonding occur.
1. hydrogen bonds form along a single chain, linking one amino
acid to another farther down the chain. This tends to pull the chain into a coil called an alpha (α) helix.
2. hydrogen bonds occur across two chains, linking the amino acids in one chain to those in the other. Often, many parallel chains are linked, forming a pleated, sheetlike structure called a β-pleated sheet.