Kinetics and mechanism of proton transport across membrane nanopores

TL;DR

This study uses computer simulations to analyze how protons pass through a nanopore membrane, revealing a diffusive single-file mechanism with high electrostatic barriers, and estimates a low translocation rate at neutral pH.

Contribution

It provides detailed computational insights into the kinetics and mechanism of proton transport through membrane nanopores, highlighting the role of electrostatic barriers and water chain dynamics.

Findings

Protons move via diffusive single-file water chains.

High electrostatic barriers hinder proton translocation.

Estimated rate of about 1 proton per hour per tube at neutral pH.

Abstract

We use computer simulations to study the kinetics and mechanism of proton passage through a narrow-pore carbon-nanotube membrane separating reservoirs of liquid water. Free energy and rate constant calculations show that protons move across the membrane diffusively in single-file chains of hydrogen-bonded water molecules. Proton passage through the membrane is opposed by a high barrier along the effective potential, reflecting the large electrostatic penalty for desolvation and reminiscent of charge exclusion in biological water channels. At neutral pH, we estimate a translocation rate of about 1 proton per hour and tube.