Water transport through a transmembrane channel formed by arylene ethynylene macrocycles

Abstract

Benefitting from the rigid backbone and π–π stacking interactions, arylene ethynylene macrocycles (AEMs) have a high tendency toward a stable nanotube assembly, which brings about potential in transmembrane channel use. Herein, we use molecular dynamics simulations to study the transport properties of water molecules through such a macrocycle nanotube (MNT) embedded in a DPPC bilayer membrane. For comparison, we also consider a structurally less complex channel of carbon nanotube (CNT) with similar size. We find that due to the spatial distribution of the MNT interior, water density profiles exhibit more remarkable wave patterns compared to the CNT, where the water occupancy within cross-sections along the channel have a unique variation of 2–3–2–3. Water molecules inside the MNT are subject to not only shape shifting but also rotation to satisfy the steric environment, which results in an inertial loss and slows down the water flow. We further consider the effect of channel–water interaction and channel length. The water flow through MNTs and CNTs both exhibit maximum behaviors with the increase of channel–water interactions. The MNT flow becomes larger when the channel–water interaction is at low or high levels. Both the water flow decrease steeply first and then smoothly with the increase of channel length. These results indicate that the channel structure and channel–water interaction have a distinct impact on the transport properties of water molecules. As the size of MNT can be well controlled by experimental techniques, this is promising for the design of novel nanofluidic devices.