Makhnovskii Yu A, Rozenbaum V M, Yang D-Y, Lin S H
Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166 Taipei, Taiwan.
J Phys Chem A. 2007 Sep 27;111(38):9486-93. doi: 10.1021/jp073307u. Epub 2007 Aug 16.
This paper analyzes the confined motion of a Brownian particle fluctuating between two conformational states with different potential profiles and different position-dependent rate constants of the transitions, the fluctuations arising from both thermal (equilibrium) and external (nonequilibrium) noise. The model illustrates a mechanism to transduce, on the nanoscale, the energy of nonequilibrium fluctuations into mechanical energy of reciprocating motion. Expressions for the reciprocating velocity and the efficiency of energy conversion are derived. These expressions are treated in more detail in the slow-fluctuation (quasi-equilibrium) regime, by simple perturbation theory arguments, and in the fast fluctuation limit, in terms of the potential of mean force. A notable observation is that the generalized driving force of the reciprocating motion is caused by two sources: the energy contribution due to the difference between the potential profiles of the states and the entropic contribution due to the difference between the position-dependent rate constants. Two illustrative examples are presented, where one of the two sources can be ignored and an exact solution is allowed. Among other aspects, we also discuss the ways to construct a molecular motor based on the reciprocating engine.
本文分析了一个布朗粒子在具有不同势分布和不同位置依赖跃迁速率常数的两个构象状态之间波动的受限运动，这种波动源于热（平衡）噪声和外部（非平衡）噪声。该模型展示了一种在纳米尺度上把非平衡涨落能量转化为往复运动机械能的机制。推导了往复速度和能量转换效率的表达式。通过简单的微扰理论论证，在慢涨落（准平衡） regime 中对这些表达式进行了更详细的处理，并在快涨落极限下，根据平均力势进行了处理。一个值得注意的观察结果是，往复运动的广义驱动力由两个来源引起：由于状态势分布差异导致的能量贡献以及由于位置依赖速率常数差异导致的熵贡献。给出了两个示例，其中两个来源之一可以忽略并得到精确解。在其他方面，我们还讨论了基于往复式发动机构建分子马达的方法。
