Periodic electric field as a biopolymer conformation switch: a possible mechanism.

A theoretical model is proposed to describe the influence of a periodic electric field (PEF) upon a biopolymer. The biopolymer is treated as a classical mechanical system consisting of subsystems (molecular groups) which interact with each other through potential forces. The PEF is treated as a periodic driving force applied to a molecular group. The energy dissipation is considered using the model of fluid (viscous) friction. Arguments for the non-linear character of the friction-velocity dependence caused by the non-Newtonian rheology of a viscous medium are formulated. A forced molecular-group motion is investigated for the situation of a small driving-force period, with oscillations overdamped and a driving force consisting of more than one harmonic. As a result, it is established that the motion always gets to a terminal stage when only a small-scale vibration about some point, X*, takes place. The terminal motion is preceded by a transient characterized by the presence of a directional velocity component and so by a drift along a potential profile. The drift goes on until a barrier is met which has a sufficiently large steepness (the barrier height is not important). As a result, the point X* may happen to be remote from the conformation potential local minimum (conformational state). The physical reasons for the drift are described.(ABSTRACT TRUNCATED AT 250 WORDS)