Relationship between stiffness and force in single molecule pulling experiments

Single molecule pulling experiment was performed wherein the tip is oscillated at the same time as the molecule is pulled. The force and stiffness data were found to be in excellent agreement in regions of conservative behavior suggesting that elastic behavior dominates this region of the pulling curve at the frequency used for measurement. This shows how simultaneous acquisition of static and oscillatory data serves as a check of nondissipative, nondispersive behavior. Portions of the curve must correspond to an elastic distortion of the chromatin. In addition, more complex behavior could be studied by recording both the amplitude and phase of the cantilever displacement over a wide range of frequencies.