Figure 1.

Typical force-extension curve recorded in an AFM stretching experiment on a (GB1)₈ construct. The lower curve shows the force as the AFM tip approaches the substrate until the contact is established. The upper curve represents the force while the tip is retracted from the substrate and shows a series of unfolding events of the construct picked up by the tip. Notice that this trace displays six unfolding events. The effect of an aspecific interaction at the beginning of the retracting trace is observed. The peak forces leading to the unfolding of the various modules are measured with respect to the background provided by the constant part of the retracting curve.