Simulations of a Myosin II dynamics based on a pulsating ratchet with double-well potentials

Although molecular motors of various kinds have been proposed during the last decade to try to explain the main dynamical features of proteins, it is fair to claim that the detailed biological mechanism responsible for converting chemical energy into directional motion is still rather obscure. The proposed models are mainly centered on ratchets or Brownian motors because their use is not restricted to myosin dynamics alone, but are also appropriate for a wide range of biophysical phenomena. An important characteristic feature of ratchets is their energetic efficiency, quantitatively indicating how much they are able to convert fluctuations into useful work. Generally, the so-called “flashing ratchets”, in which transported particles are subject to a time fluctuating potential, show energetic efficiency values that are less than the corresponding experimental results. However, recent investigations have demonstrated that some kind of ratchet models based on alternating potentials with identical spatial periods and mutually shifted by half a period can achieve a better efficiency. With reference to such kinds of ratchets, by adding the assumptions that the motor step equals the distance L between successive actin monomers, here we propose a model of pulsating ratchet based on two 2L-periodic double-well potentials, U1(x) and U2(x) alternate according to a Poisson process. Numerous simulations for several choices of involved parameters, indicate increased values of the motor efficiency.