Fig. 2.

Schematic diagram of a collagen fibril illustrating the distinct triple helical structure of the α-chains. Representative portions of three individual α-chains, each with the triple amino acid repeat Gly-X-Y, are shown in the magnified section. Each chain is comprised of a glycine (black), proline (position ‘X,’ red), and hydroxyproline (position ‘Y,’ blue) residue. Hydrogen bonds (dashed black lines) between the N–H of glycine on each chain and the carbonyl of proline on an adjacent chain establish the triple helix