The Underlying Structure of an Alpha-Helical Peptide. This reveals a complex pattern of covalent bonds. When a peptide folds into an alpha-helix, the backbone atoms are brought near each other.
Hydrogen bonds form between the backbone oxygens and nitrogens .
Hydrogen bonds provide an effective stabilizing force only when many act together, as they do here. Hydrophobic interactions are another source of stability for the alpha-helical shape. The helix folds so as to minimize the contact of hydrophobic carbons with the watery medium. If not for this packing, the backbone oxygens and amines would hydrogen bond to water molecules instead of each other. Click and drag on the molecule to rotate it to see the distribution of hydrophilic side chains yourself.