Data from: "Ion transport in carbon nanotube porins with a pH-switchable entrance gate"

Molecular transport in nanofluidic channels whose sizes approach molecular dimensions often differs drastically from conventional bulk transport. Strong confinement forces molecules in those channels into close proximity with channel walls, amplifying the roles of surface transport, surface defects, and molecular gates. Here we use defect-induced chemical etching (DICE) to introduce a defined chemical functionality at the nanotube rim that acts as a pH-triggered molecular gate by forming a movable lid that blocks the pore entrance. We use single channel ion and proton transport measurement to show that these sub-1-nm diameter fluorescent ultra-short carbon nanotube porins (FUNPs) are able to modulate ion transport by switching between the ``open'' and ``closed'' conformations of this molecular gate. Specifically, at neutral pH the channel lid is open, allowing virtually unimpeded ion transport through the gate, where as at the acidic pH values the lid forms a ``closed'' conformation that blocks transport through the nanotube. We also report first-principles MD simulations that confirm this gating mechanism and reveal further molecular details of the ion and proton transport processes in these functional nanopores.