Kinetics of a semiflexible chain under external force.

The kinetic properties of a semiflexible chain subject to an external force are investigated using scaling arguments and computer simulations. By monitoring the mean square displacements in principal axes, the authors found that the anisotropic dynamic fluctuations go through several distinct kinetic regimes characterized by two different exponents corresponding to transverse and longitudinal fluctuations. When a force is applied at one chain end, the tension propagates gradually to the other end, leading to nonuniform tension profiles. At short times, they observe sublinear relaxation of the mean square fluctuations in both longitudinal and transverse directions. At intermediate times, the kinetics is dominated by tension driven straightening with smaller kinetic exponents. Nonuniform tension profiles lead to the superlinear dependence of the longitudinal mean square displacement. In contrast, the late stage relaxation is diffusive again once the tension profile becomes uniform. The detailed tension profiles are reported for constant force measurement as well as constant pulling speed measurement.