基于过渡态速率理论的叶片类囊体膜离子通道模型

Modeling the ion channel of thylakoid membrane in leaves based on the transition state rate theory

开发了一种基于过渡态速率理论(TSRT)的离子通道模型,并首次应用在植物叶片类囊体膜阳离子通道建模中.在该模型体系中,离子跨膜输运被认为是穿越数个能垒和结合位点的耗能过程.模型采用3个能垒和2个结合位点的模式(3B2S),并允许不同种类离子占据其中位点,但"挤出(knock out)效应"不考虑在内.通过计算叶片类囊体膜上的电压门控离子通道的阳离子流密度和研究跨膜电势差的消长情况,发现该模型能够很好地模拟离子通道所具备的3种特性,即饱和性、选择性以及竞争性抑制.而且该模型对参数需求少,运算时间短,可快速高效地获取一种离子通道的协助转运特性,为进一步的布朗动力学仿真提供基础.该模型也可嵌入到叶片整体光合系统模型中,为深入理解叶绿体光诱导的跨膜电势差的消散机理提供一种新的思路.

An ionic transport model was developed based on the transition state rate theory(TSRT) and it was used to model the cation channel of thylakoid membrane in leaves. In this scenario, the ion transmembrane transport is considered to be a process of energy consumption through several energy barriers and binding sites. The model adopts the mode of three energy barriers and two binding sites(3 B2 S), and allows different kinds of ions to occupy the sites. However, the "knock out effect" is not taken into account. It was found that the TSRT model is able to reproduce three characteristics: saturability, selectivity and competitiveness, by means of calculating the cation fluxes of thylakoid membrane and analyzing the variation of trans-membrane voltage. Moreover, the model requires few parameters and has short operation time, which can quickly and efficiently obtain the assisted transport characteristics of an ion channel, and provide the basis for further Brownian dynamics simulation. It could be inserted into the integrated photosynthetic model. Therefore, this provides a new idea for further understanding the dissipation mechanism of chloroplast induced transmembrane potential difference.