Planetary Rotary Ratchets of a Rigid Roller Held within a Soft Rotor Housing, and Its Robust Rotation Transmission Mechanism

摘要

Biological rotary motors seemingly comprise the rigid and soft (compliant or flexible) parts of a protein subunit, and such parts are considered to be assembled to robustly transmit torque against disturbances. To explore the efficacy of operating a rigid roller held within a soft rotor housing (RH), as in a molecular rotary motor, we study stochastic rotary ratchet models that incorporate the design of a planetary rotary engine or a Wankel rotary engine. Using models that comprise a rotor of M-fold symmetry (M = 2, 3,4) and a two-dimensional soft RH potential of (M - 1)-fold symmetry, we investigate the dynamics of a rotor driven by a rotationally modulated potential. We define a lever mechanism proper to a system comprising a rigid rotor and a soft RH, and elucidate how the force of the modulation from the RH is efficiently transmitted to the rotor to cause robust unidirectional rotation.