Elasticity in the DC-SIGNR/glycolipid complex is also apparent from comparisons of approaching and receding forceÀ distance curves between the various forms of DC-SIGNR and Man 9 GlcNAc 2 membranes. During separation, the bonds fail and the surfaces pull out of contact at the position of the maximum adhesion (D Adh ) ( Figure 2B, right pointing arrow) . For the 7and 6-repeat forms of DC-SIGNR, D Adh exceeds D eq by 3.5 nm (Table 1 , Figures 2B and 3A,B) . This difference must result from stretching of the DC-SIGNR/Man 9 GlcNAc 2 complex such that, upon separation, the complexes extend relative to their equilibrium thickness D eq . This may be due, in part, to the reorientation of the carbohydrate ligand. Protein flexibility, which enables the DC-SIGNR variants to jump to contact at D C < D T , would also play a role in this force-dependent stretching.