title: Ultrafast proton transport in sub-1-nm diameter carbon nanotube porins.
abstract: Proton transport plays an important role in many biological processes due to the ability of protons to rapidly translocate along chains of hydrogen-bonded water molecules. Molecular dynamics simulations have predicted that confinement in hydrophobic nanochannels should enhance the rate of proton transport. Here, we show that 0.8-nm-diameter carbon nanotube porins, which promote the formation of one-dimensional water wires, can support proton transport rates exceeding those of bulk water by an order of magnitude. The transport rates in these narrow nanotube pores also exceed those of biological channels and Nafion. With larger 1.5-nm-diameter nanotube porins, proton transport rates comparable to bulk water are observed. We also show that the proton conductance of these channels can be modulated by the presence of Ca(2+) ions. Our results illustrate the potential of small-diameter carbon nanotube porins as a proton conductor material and suggest that strong spatial confinement is a key factor in enabling efficient proton transport.
authors.affiliation: Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA.
authors.forename: Ramya H
authors.initials: RH
authors.lastname: Tunuguntla
authors.affiliation: Department of Materials Science and Engineering, University of California, 210 Hearst Avenue, Berkeley, California 94720, USA.|National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA.
authors.forename: Frances I
authors.initials: FI
authors.lastname: Allen
authors.affiliation: Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA.
authors.forename: Kyunghoon
authors.initials: K
authors.lastname: Kim
authors.affiliation: Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA.
authors.forename: Allison
authors.initials: A
authors.lastname: Belliveau
authors.affiliation: Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA.|School of Natural Sciences, University of California Merced, 5200 N. Lake Road, Merced, California 94343, USA.
authors.forename: Aleksandr
authors.initials: A
authors.lastname: Noy