Time course of force relaxation after lengthening and shortening of the tether.

Both the tether length (lower curve, filled symbols) and tether force (upper curve, open symbols) are shown as functions of time. The equilibrium force for this tether is between 34 and 35 pN. This value is approached after the initial formation of the tether and again after successive lengthening and shortening of the tether length. This behavior is characteristic of a system in thermodynamic equilibrium.