Inchworm movement of two rings switching onto a thread by biased Brownian diffusion represent a three-body problem
Inchworm movement of two rings switching onto a thread by biased Brownian diffusion represent a three-body problem
复制标题
DOI：
10.1073/pnas.1719539115
复制
发表时间：
2018-09-18
影响因子：
11.1
通讯作者：
Flood, Amar H.
中科院分区：
文献类型：
--
作者：
Benson, Christopher R.;Maffeo, Christopher;Flood, Amar H.
许多单个部件的协调运动是所有机器运行的基础。然而，尽管有几代人的工程经验，理解三个或更多耦合部件的运动仍然是一个挑战，自牛顿时代以来被称为“三体问题”。“在这里，我们描述，量化和模拟一个分子三体问题，将两个分子环连接到一个线性分子线上。具体来说，我们使用基于四嗪的线的电压触发还原来捕获两个矢车菊大环并形成[3]伪轮烷产物。由于氰星环之间的非共价耦合，我们发现线程发生意外和罕见的尺蠖状运动，其中一个环如下其他。该机制来自控制，循环伏安法（CV）的痕迹分析，和布朗动力学模拟。来自两个非共价相互作用的环的CV与被设计为通过尺蠖途径穿线的两个共价连接的环的CV相匹配，并且它们显著偏离被设计为通过逐步途径穿线的大环的CV。随时间变化的电化学提供了线程的速率常数的估计。实验得出的参数（能量威尔斯，障碍，扩散系数）有助于确定可能的运动路径与速率动力学和布朗动力学模拟。模拟结果表明，在动力学方面，组件间的耦合可以分解为环-线耦合，在热力学方面，可以分解为环-环耦合，从而将三体问题简化为两体问题。我们的研究结果提供了一个基础，高通量设计的分子机械与多个组件进行耦合运动。
The coordinated motion of many individual components underpins the operation of all machines. However, despite generations of experience in engineering, understanding the motion of three or more coupled components remains a challenge, known since the time of Newton as the "three-body problem." Here, we describe, quantify, and simulate a molecular three-body problem of threading two molecular rings onto a linear molecular thread. Specifically, we use voltage-triggered reduction of a tetrazine-based thread to capture two cyanostar macrocycles and form a [3]pseudorotaxane product. As a consequence of the noncovalent coupling between the cyanostar rings, we find the threading occurs by an unexpected and rare inchworm-like motion where one ring follows the other. The mechanism was derived from controls, analysis of cyclic voltammetry (CV) traces, and Brownian dynamics simulations. CVs from two noncovalently interacting rings match that of two covalently linked rings designed to thread via the inchworm pathway, and they deviate considerably from the CV of a macrocycle designed to thread via a stepwise pathway. Time-dependent electrochemistry provides estimates of rate constants for threading. Experimentally derived parameters (energy wells, barriers, diffusion coefficients) helped determine likely pathways of motion with rate-kinetics and Brownian dynamics simulations. Simulations verified intercomponent coupling could be separated into ring-thread interactions for kinetics, and ring-ring interactions for thermodynamics to reduce the three-body problem to a two-body one. Our findings provide a basis for high-throughput design of molecular machinery with multiple components undergoing coupled motion.