FREE ENERGY CONVERSION IN BIOLOGY

单一的动蛋白分子(一种马达蛋白)已被证明能够 在微管(一种周期性生物聚合物)上单向移动 相同的单体亚基)通过催化三磷酸腺苷的水解。 三磷酸腺苷水解的化学自由能到底是如何转化的 机械能在这个系统中的作用还不清楚。在最后一次 报告中，我们展示了酶作用下的布朗粒子可以被驱动到 在静态周期电势场上单向运动 它催化的化学反应的自由能，如果至少有一个 催化循环的中间产物被带电，并且 各周期的势场是不对称的。这是第一次 具有显示化学-机械自由的显式机制的模型 进行能量转换。今年，我们延长了 进一步研究，集中力量抓好两个问题。首先，我们 研究了当酶反应时布朗粒子的行为 包含一个以上的循环和一个以上的带电 各州。研究发现，颗粒运动的方向 不仅取决于势的不对称性，而且还取决于 详细的催化反应机理。这一结果表明 一种基于蛋白质分子的实验分离方法 酶活性。二、形式主义和计算主义 程序已被延长和重新制定，以便它们成为 适用于动蛋白分子。一般而言，存在一个 微管表面附近的静态周期电场是 不太可能。因此，基于直接交互的模型 在带电状态和周期性不对称电场之间可以 不能直接应用于激动素系统。相反，我们有 使用与肌肉收缩相同的“过桥”概念，其中 力是通过连接运动蛋白的一部分产生的(交叉- 桥)连接到微管的每个单体上的特定结合位置。 目前，形式主义被用于评估运动蛋白的机制 基于体外实验数据的运动。

Single kinesin molecules (a motor protein) have been shown to be able to move unidirectionally on a microtubule (a periodic biopolymer made of identical monomer subunits) by catalyzing the hydrolysis of ATP. Exactly how the chemical free energy of ATP hydrolysis is converted into mechanical energy in this system is not clear. In the last report, we showed that an enzymatic Brownian particle can be driven to move unidirectionally on a static periodic electric potential field by the free energy of the chemical reaction it catalyzes, if at least one of the intermediates of the catalytic cycle is charged and the potential field in each period is not symmetrical. This is the first model with explicit mechanisms showing how chemical-mechanical free energy transduction is carried out. This year, we have extended the research further and concentrated our work on two problems. First, we examined how the Brownian particle behave when the enzymatic reactions of the particle contains more than one cycle and more than one charged states. It was found that the direction of the particle movement depended not only on the asymmetry of the potential, but also on the detailed mechanisms of the catalytic reactions. This result suggests an experimental separation method for protein molecules based on their enzymatic activities. Second, the formalism and the calculation procedure have been extended and reformulated so that they become applicable to kinesin molecules. In general, the existence of a static periodic electric field near the surface of a microtubule is not very likely. Therefore, the model based on direct interaction between charged states and a periodic asymmetric electric field may not be directly applicable to the kinesin system. Instead, we have used the same "cross-bridge" concept as in muscle contraction, where force is generated by attaching a part of the kinesin (the cross- bridge) to a specific binding site on each monomer of the microtubule. The formalism is currently used in assessing the mechanisms of kinesin movement based on in vitro experimental data.