Peptide sequences used for the preparation of collagen cleavage antibodies. The cleavage positions of cathepsin K and collagenase in the triple helical domain of type II collagen are indicated. Small grey arrows designate the minor collagenase cleavage positions recognized by the C1,2C antibody following reaction at the primary site. The sequences of the collagen molecule forming the C-terminus of the fragments generated on cleavage represent the C2K, C2C and C1,2C epitopes. P* denotes 4-hydroxyproline.