Single-molecule force spectroscopy.

<p>(A) Force spectroscopy data obtained during the bond rupture between E1-5 constructs attached to a gold-coated AFM tip and a gold-covered glass slide (see scheme). A typical force extension curve shows the unbinding of E1-5 dimers in the absence of calcium ions (grey) and the presence of calcium ions (green). The extension curves show nonlinear stretching behavior preceding bond rupture. The rupture force histogram (green) reveals two major maxima potentially corresponding to two types of bonds. (B) Corresponding SMFS data of force-assisted unbinding of E1-2/E1-2 (red) or (C) E1-5/E1-2 (orange) cadherin molecules attached to tip and substrate as illustrated in the schemes. Tip substrate contact time was 0.1 s and pulling velocity was 1 μm/s.