旋转生物马达中的质子输运和转矩产生
Proton transport and torque generation in rotary biomotors
摘要：
我们分析了一个简单的纳米机电模型，由一个定子部分和一个环形转子有12个质子结合位点的旋转生物马达的动力学。该模型与腺苷三磷酸（ATP）合酶的膜嵌入式F $_0$马达密切相关，该马达将质子的跨膜电化学梯度的能量转化为转子的机械运动。结果表明，空转子位置的负电荷和正定子电荷之间的库仑耦合，位于附近的周质质子传导通道（质子源），在扭矩产生过程中起着主导作用。当接近源出口时，转子位点具有高于该位点的能级的质子能级，位于细胞质通道（质子漏）附近。在该转矩产生过程的第一阶段，电化学电势的能量被转换成转子上的质子结合位点的势能。然后，库仑力的切向分量产生机械扭矩。我们证明，在低温下，负载电机工作在穿梭制度的电化学势的能量被消耗，而不产生任何单向旋转。在高温下，当布朗棘轮机制启动时，马达切换到产生扭矩的状态。在ATP水解产生的显著外部扭矩存在的情况下，系统作为质子泵运行，逆着跨膜电势梯度转移质子。在这里，我们专注于F $_0$电机，即使我们的分析是适用于细菌鞭毛电机。
英文摘要：
We analyze the dynamics of rotary biomotors within a simple nano-electromechanical model, consisting of a stator part and a ring-shaped rotor having twelve proton-binding sites. This model is closely related to the membrane-embedded F$_0$ motor of adenosine triphosphate (ATP) synthase, which converts the energy of the transmembrane electrochemical gradient of protons into mechanical motion of the rotor. It is shown that the Coulomb coupling between the negative charge of the empty rotor site and the positive stator charge, located near the periplasmic proton-conducting channel (proton source), plays a dominant role in the torque-generating process. When approaching the source outlet, the rotor site has a proton energy level higher than the energy level of the site, located near the cytoplasmic channel (proton drain). In the first stage of this torque-generating process, the energy of the electrochemical potential is converted into potential energy of the proton-binding sites on the rotor. Afterwards, the tangential component of the Coulomb force produces a mechanical torque. We demonstrate that, at low temperatures, the loaded motor works in the shuttling regime where the energy of the electrochemical potential is consumed without producing any unidirectional rotation. The motor switches to the torque-generating regime at high temperatures, when the Brownian ratchet mechanism turns on. In the presence of a significant external torque, created by ATP hydrolysis, the system operates as a proton pump, which translocates protons against the transmembrane potential gradient. Here we focus on the F$_0$ motor, even though our analysis is applicable to the bacterial flagellar motor.
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