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. Author manuscript; available in PMC: 2009 Jun 28.
Published in final edited form as: Ann N Y Acad Sci. 2009 Jan;1152:113–120. doi: 10.1111/j.1749-6632.2008.03991.x

Figure 4.

Figure 4

The retraction part of a typical force-distance (extension) curve using a Sx1A/SNAP25B functionalized tip and a Sb2 functionalized coverslip. In the segments ab and bc the coverslip and the cantilever tip are still in contact. The bcd segment is due to non-specific ineractions which are present even in the absence of any proteins. The Sx1A-SNAP25B-Sb2 intermolecular “bond” starts to be extended at point d. The increasing extension as the coverslip moves further away from the tip leads to an increased application of force on the intermolecular bond till it ruptures at point e. The segment ef' is then the measure of the force (ordinate) necessary to remove Sx1A-SNAP25B-Sb2 interaction. The extension induced can be calculated from the z-axis distance moved by the piezo (abscissa) given by segment de. The dotted line indicates the extension after the distance has been corrected for the bending of the cantilever. Retraction velocity: 1.6 μm/s.