Nanopore electro-osmotic trap for the label-free study of single proteins and their conformations
Sonja Schmid (Wageningen University & Research, Kavli institute of nanoscience Delft, TU Delft - Applied Sciences)
Pierre Stömmer (Technische Universität München)
Hendrik Dietz (Technische Universität München)
Cees Dekker (Kavli institute of nanoscience Delft, TU Delft - Applied Sciences)
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Abstract
Many strategies have been pursued to trap and monitor single proteins over time to detect the molecular mechanisms of these essential nanomachines. Single-protein sensing with nanopores is particularly attractive because it allows label-free high-bandwidth detection on the basis of ion currents. Here we present the nanopore electro-osmotic trap (NEOtrap) that allows trapping and observing single proteins for hours with submillisecond time resolution. The NEOtrap is formed by docking a DNA-origami sphere onto a passivated solid-state nanopore, which seals off a nanocavity of a user-defined size and creates an electro-osmotic flow that traps nearby particles irrespective of their charge. We demonstrate the NEOtrap’s ability to sensitively distinguish proteins on the basis of size and shape, and discriminate between nucleotide-dependent protein conformations, as exemplified by the chaperone protein Hsp90. Given the experimental simplicity and capacity for label-free single-protein detection over the broad bio-relevant time range, the NEOtrap opens new avenues to study the molecular kinetics underlying protein function.