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Mapping Intrachannel Diffusive Dynamics of Interacting Molecules onto a Two-Site Model: Crossover in Flux Concentration Dependence
The Journal of Physical Chemistry B ( IF 3.3 ) Pub Date : 2018-06-29 , DOI: 10.1021/acs.jpcb.8b04371
Alexander M. Berezhkovskii 1, 2 , Sergey M. Bezrukov 1
Affiliation  

This study focuses on how interactions of solute molecules affect the concentration dependence of their flux through narrow membrane channels. It is assumed that the molecules cannot bypass each other because of their hard-core repulsion. In addition, other short- and long-range solute–solute interactions are included into consideration. These interactions make it impossible to develop an analytical theory for the flux in the framework of a diffusion model of solute dynamics in the channel. To overcome this difficulty, we course-grain the diffusion model by mapping it onto a two-site one, where the rate constants describing the solute dynamics are expressed in terms of the parameters of the initial diffusion model. This allows us (i) to find an analytical solution for the flux as a function of the solute concentration and (ii) to characterize the solute–solute interactions by two dimensionless parameters. Such a characterization proves to be very informative as it results in a clear classification of the effects of the solute–solute interactions on the concentration dependence of the flux. Unexpectedly, this dependence can be nonmonotonic, exhibiting a sharp maximum in a certain parameter range. We hypothesize that such a behavior may constitute an element of a regulatory mechanism, wherein maximal flux reports on the optimal solute concentration in the bulk near the channel entrance.

中文翻译:

将相互作用分子的通道内扩散动力学映射到两站点模型上:通量浓度依赖性的交叉

这项研究的重点是溶质分子的相互作用如何影响通过窄膜通道的通量的浓度依赖性。假定分子由于其硬核排斥而不能彼此绕过。此外,还考虑了其​​他短期和长期的溶质-溶质相互作用。这些相互作用使得不可能在通道中溶质动力学扩散模型的框架内发展出关于通量的分析理论。为了克服这一困难,我们通过将扩散模型映射到两点模型来对粒度模型进行处理,其中描述溶质动力学的速率常数是根据初始扩散模型的参数来表示的。这使我们(i)可以找到通量作为溶质浓度的函数的解析解,并且(ii)通过两个无量纲参数来描述溶质-溶质之间的相互作用。这种表征被证明是非常有用的,因为它可以对溶质-溶质相互作用对通量浓度依赖性的影响进行清晰的分类。出乎意料的是,这种依赖性可能是非单调的,在特定参数范围内显示出极大的最大值。我们假设这种行为可能构成调节机制的一个要素,其中最大通量报告了通道入口附近大部分物质中的最佳溶质浓度。这种表征被证明是非常有用的,因为它可以对溶质-溶质相互作用对通量浓度依赖性的影响进行清晰的分类。出乎意料的是,这种依赖性可能是非单调的,在特定参数范围内显示出极大的最大值。我们假设这种行为可能构成调节机制的一个要素,其中最大通量报告了通道入口附近大部分物质中的最佳溶质浓度。这种表征被证明是非常有用的,因为它可以对溶质-溶质相互作用对通量浓度依赖性的影响进行清晰的分类。出乎意料的是,这种依赖性可能是非单调的,在特定参数范围内显示出极大的最大值。我们假设这种行为可能构成调节机制的一个要素,其中最大通量报告了通道入口附近大部分物质中的最佳溶质浓度。
更新日期:2018-11-29
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