Collagen/collagen interaction sites involved in fibril formation; the basic concept of inhibiting collagen fibril formation. A, the stages of normal fibril formation by site-specific interaction between telopeptides of one collagen molecule and the T-TBR of the interacting molecule located in the D4 period; fibril-incorporated collagen molecules are very resistant to enzymatic degradation. B, by blocking the sites of critical collagen-collagen interaction, formation of fibrils is inhibited, preventing the accumulation of fibrils and allowing rapid degradation of excess collagen molecules. Asterisks represent sites of cross-links formation. The model of a microfibril illustrates the compact packing of collagen molecules (indicated in colors matching those for specific D periods) and indicates how the binding of a bulky inhibitor to collagen molecules would prevent such a compact organization.