1.D.149. The Rosette Nanotube Porin (RosNT) Family
Rosette nanotubes (RNTs) are a class of materials formed by molecular self-assembly of a fused guanine-cytosine base (GwedgeC base). An important feature of these self-assembled nanotubes is their precise atomic structure, intriguing for rational design and optimization as synthetic transmembrane porins. Tripathi et al. 2020 presented experimental observations of ion transport across 1.1 nm inner diameter RNT porins (RNTPs) of various lengths in the range 5-200 nm. In a typical experiment, custom lipophilic RNTPs were first inserted into lipid vesicles; the vesicles then spontaneously fused with a planar lipid bilayer, which produced stepwise increases of ionic current across the bilayer. Measurements in 1 M KCl solution indicated ion transport rates of approximately 50 ions s-1 V-1 m, which for short channels amounts to conductance values of approximately 1 nS, commensurate with naturally occurring toxin channels such as alpha-hemolysin. Measurements of interaction times of alpha-cyclodextrin with RNTPs revealed two distinct unbinding time scales, which suggested that interactions of either face of alpha-cyclodextrin with the RNTP face are differentiable, backed with all-atom molecular dynamics simulations. hese results highlight the potential of RNTPs as self-assembled nonproteinaceous single-molecule sensors and selective nanofilters with tunable functionality through chemistry (Tripathi et al. 2020).