Collagen is composed of three chains, which wind into triple helices. As there are high percentages of acidic and basic residues in natural collagen, mechanisms of how salt bridges could modulate the trimerization have been received much attention. Sixteen pairwise salt bridges were constructed in a collagen heterotrimer abc, making an energetic-contribution library for collagen stability. The local stability of type I collagen was predicted from the library. Separation between the stabilizing and ligand-binding regions of type I collagen suggests that there be a balance between overall stability to maintain triple helices and local instability relevant to biological functions.