FIGURE 2.

Various sacrificial bonds on single strand connections. (1) The molecule binds to itself with sacrificial bonds; the hidden length is the distance between the two binding sites on the molecule. When a force is applied and molecules are stretched, the sacrificial bonds will break according to their relative bond strengths (20). (2) The molecule binds to the surface with sacrificial bonds. The hidden length equals the distance between two neighboring sites on the molecule that bind to the surface. When a force is applied and the molecules are stretched, the sacrificial bonds break in the sequence that they are in on the molecule. (3) One molecule binds to a second molecule with complementary binding site sequence. The hidden length equals the distance between neighboring sacrificial bonds on one molecule plus the distance between the corresponding binding sites on the second molecule (in the figure this length is twice the distance between A and B). When a force is applied and the molecules are stretched, the bonds break in the sequence that they are in on the molecules (17,27,29). (4) One molecule bonds to a second molecule with a reversed complementary binding site sequence. The sacrificial bonds are loaded in parallel; therefore they will all break once a force is reached larger than the combined binding force. In this case, no hidden length is set free.