Intrinsic ion selectivity of narrow hydrophobic pores
1School of Biomedical, Biomolecular and Chemical Sciences, The University of Western Australia, Crawley, WA 6009, Australia.
Abstract:
We show that narrow hydrophobic pores have an intrinsic ion selectivity by using single-walled carbon nanotube membranes as a model. We examined pores of radius 3.4-6.1 A, and conducted molecular dynamics simulations to show that Na+, K+, and Cl- face different free energy barriers when entering hydrophobic pores. Most of the differences result from the different dehydration energies of the ions; however, changes in the solvation shell structure in the confined nanotube interior and van der Waals interactions in the small tubes can both play a role. Molecular dynamics simulations conducted under hydrostatic pressure show that carbon nanotube membranes can act as ion sieves, with the pore radius and pressure determining which ions will permeate through the membrane. This work suggests that the intrinsic ion selectivity of biological pores of differing radii might also play a role in determining their selectivity, in addition to the more common explanations based on electrostatic effects. In addition, "hydrophobic gating" can arise in continuous water-filled pores.
Related Concept Videos
Pore Transport and Ion-Pair Transport
Pore transport, also known as convective transport, is a process where small molecules like urea, water, and sugars rapidly cross cell membranes as though there were channels or pores in the membrane. Although direct microscopic evidence is limited but the concept of pores or channels is widely accepted based on physiological evidence. Despite the lack of direct microscopic...
Potentiometry: Membrane Electrodes
Aquaporins
Non-gated Ion Channels
Compared to the gated ion channels, the non-gated channels, also known as leakage or passive channels, have no gating mechanism.
Non-gated Ion Channels
Compared to the gated ion channels, the non-gated channels, also known as leakage or passive channels, have no gating mechanism.
The Significance of Membrane Transport
Transporters facilitate either an active or passive movement of solutes. They can allow a single-molecule transport down its...


