Different transport behaviors of NH4+ and NH3 in transmembrane cyclic peptide nanotubes

摘要

Two water-filled transmembrane cyclic peptide nanotubes (CPNTs) of 8xcyclo-(WL)(n=4,5)/POPE were chosen to investigate the dependences of the transport properties of the positive NH4+ and neutral NH3 on the channel radius. Molecular dynamic simulations revealed that molecular charge, size, ability to form H-bonds and channel radius all significantly influence the behaviors of NH4+ and NH3 in a CPNT. Higher electrostatic interactions, more H-bonds, and water-bridges were found in the NH4+ system, resulting in NH4+ meeting higher energy barriers, while NH3 can enter, exit and permeate the channels effortlessly. This work sheds a first light on the differences between the mechanisms of NH4+ and NH3 moving in a CPNTat an atomic level.