Molecular transport through channels and pores: Effects of in-channel interactions and blocking
Molecular transport through channels and pores: Effects of in-channel interactions and blocking
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DOI：
10.1073/pnas.0601769103
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发表时间：
2006-08-01
影响因子：
11.1
通讯作者：
Nadler, Walter
中科院分区：
文献类型：
--
作者：
Bauer, Wolfgang R.;Nadler, Walter
分子通过通道和孔的易化移位对于生物系统中的跨膜转运具有根本重要性。几个这样的系统在通道内具有特定的结合位点，但是仍然缺乏对通道和分子之间的相互作用如何影响流动的清晰理解。我们对该问题提出了一种通用的分析处理方法，将分子流与首次通过时间和通道内的颗粒数量联系起来。这两个量以不同的方式取决于信道属性。对于理想化的情况下，非相互作用的分子，我们发现一个增加的流量时，有一个结合位点在通道中，尽管增加了第一次通过时间。在分子可能阻塞通道的更现实的情况下，我们发现流量的增加仅达到结合强度的某个阈值，并且依赖于浓度梯度的符号，即，不对称运输分析了这种情况下的最佳结合强度。在所有情况下，运输便利化的原因是通道内颗粒的占据概率增加，其克服了由于结合而导致的首次通过时间的任何增加。
Facilitated translocation of molecules through channels and pores is of fundamental importance for transmembrane transport in biological systems. Several such systems have specific binding sites inside the channel, but a clear understanding of how the interaction between channel and molecules affects the flow is still missing. We present a generic analytical treatment of the problem that relates molecular flow to the first passage time across and the number of particles inside the channel. Both quantities depend in different ways on the channel properties. For the idealized case of noninteracting molecules, we find an increased flow whenever there is a binding site in the channel, despite an increased first passage time. In the more realistic case that molecules may block the channel, we find an increase of flow only up to a certain threshold value of the binding strength and a dependence on the sign of the concentration gradient, i.e., asymmetric transport. The optimal binding strength in that case is analyzed. In all cases the reason for transport facilitation is an increased occupation probability of a particle inside the channel that overcomes any increase in the first passage time because of binding.