Institut Lumière Matière, Unité Mixte de Recherche 5306, Université Lyon 1-Centre National de la Recherche Scientifique, Université de Lyon, 69622 Villeurbanne, France.
Proc Natl Acad Sci U S A. 2013 Oct 8;110(41):16367-72. doi: 10.1073/pnas.1306447110. Epub 2013 Sep 25.
The ubiquitous aquaporin channels are able to conduct water across cell membranes, combining the seemingly antagonist functions of a very high selectivity with a remarkable permeability. Whereas molecular details are obvious keys to perform these tasks, the overall efficiency of transport in such nanopores is also strongly limited by viscous dissipation arising at the connection between the nanoconstriction and the nearby bulk reservoirs. In this contribution, we focus on these so-called entrance effects and specifically examine whether the characteristic hourglass shape of aquaporins may arise from a geometrical optimum for such hydrodynamic dissipation. Using a combination of finite-element calculations and analytical modeling, we show that conical entrances with suitable opening angle can indeed provide a large increase of the overall channel permeability. Moreover, the optimal opening angles that maximize the permeability are found to compare well with the angles measured in a large variety of aquaporins. This suggests that the hourglass shape of aquaporins could be the result of a natural selection process toward optimal hydrodynamic transport. Finally, in a biomimetic perspective, these results provide guidelines to design artificial nanopores with optimal performances.
无处不在的水通道蛋白能够在细胞膜间传导水，将高选择性和惊人的渗透性这两种看似矛盾的功能结合在一起。尽管分子细节显然是实现这些功能的关键，但在这种纳米孔中，整体传输效率也受到纳米收缩处与附近体相储库之间的连接处粘性耗散的强烈限制。在本研究中，我们重点关注这些所谓的入口效应，并特别研究水通道蛋白的沙漏形状是否可能源于这种流体动力耗散的几何最优。我们使用有限元计算和分析模型的组合，表明具有合适开口角度的锥形入口确实可以大大提高通道的整体渗透性。此外，发现能够使渗透性最大化的最佳开口角度与在各种水通道蛋白中测量到的角度非常吻合。这表明水通道蛋白的沙漏形状可能是朝向最佳流体动力学传输的自然选择过程的结果。最后，从仿生学的角度来看，这些结果为设计具有最佳性能的人工纳米孔提供了指导。
