FIGURE 1.

Schematic of experimental setup. Recombinant syntaxin 1A and synaptobrevin 2 cytoplasmic tails are attached to the cantilever tip and coverslip, respectively, through a Ni²⁺-six histidine residue coordination at the C-termini of these proteins. The picture is not to scale. The piezo is used to first move the coverslip up toward the cantilever tip to bring about the interaction and then down to exert force on the intermolecular bond. The work parameter λ is the distance from the bottom of the cantilever holder to the top of the coverslip, x_i is the extension of the bound intermolecular complex, and F_i/k is the distance bent by the tip of a cantilever of spring constant k in response to a force F_i.