Multiple rereads of single proteins at single-amino acid resolution using nanopores

A proteomics tool capable of identifying single proteins would be important for cell biology research and applications. Here, we demonstrate a nanopore-based single-molecule peptide reader sensitive to single-amino acid substitutions within individual peptides. A DNA-peptide conjugate was pulled through the biological nanopore MspA by the DNA helicase Hel308. Reading the ion current signal through the nanopore enabled discrimination of single-amino acid substitutions in single reads. Molecular dynamics simulations showed these signals to result from size exclusion and pore binding. We also demonstrate the capability to "rewind" peptide reads, obtaining numerous independent reads of the same molecule, yielding an error rate of <10-6 in single amino acid variant identification. These proof-of-concept experiments constitute a promising basis for the development of a singlemolecule protein fingerprinting and analysis technology.BN/Cees Dekker La

SDS-assisted protein transport through solid-state nanopores

Using nanopores for single-molecule sequencing of proteins – similar to nanopore-based sequencing of DNA – faces multiple challenges, including unfolding of the complex tertiary structure of the proteins and enforcing their unidirectional translocation through nanopores. Here, we combine molecular dynamics (MD) simulations with single-molecule experiments to investigate the utility of SDS (Sodium Dodecyl Sulfate) to unfold proteins for solid-state nanopore translocation, while simultaneously endowing them with a stronger electrical charge. Our simulations and experiments prove that SDS-treated proteins show a considerable loss of the protein structure during the nanopore translocation. Moreover, SDS-treated proteins translocate through the nanopore in the direction prescribed by the electrophoretic force due to the negative charge impaired by SDS. In summary, our results suggest that SDS causes protein unfolding while facilitating protein translocation in the direction of the electrophoretic force; both characteristics being advantageous for future protein sequencing applications using solid-state nanopores.BN/Chirlmin Joo LabBN/Cees Dekker La

Translocation of DNA through Ultrathin Nanoslits

2D nanoslit devices, where two crystals with atomically flat surfaces are separated by only a few nanometers, have attracted considerable attention because their tunable control over the confinement allows for the discovery of unusual transport behavior of gas, water, and ions. Here, the passage of double-stranded DNA molecules is studied through nanoslits fabricated from exfoliated 2D materials, such as graphene or hexagonal boron nitride, and the DNA polymer behavior is examined in this tight confinement. Two types of events are observed in the ionic current: long current blockades that signal DNA translocation and short spikes where DNA enters the slits but withdraws. DNA translocation events exhibit three distinct phases in their current-blockade traces—loading, translation, and exit. Coarse-grained molecular dynamics simulation allows the different polymer configurations of these phases to be identified. DNA molecules, including folds and knots in their polymer structure, are observed to slide through the slits with near-uniform velocity without noticeable frictional interactions of DNA with the confining graphene surfaces. It is anticipated that this new class of 2D-nanoslit devices will provide unique ways to study polymer physics and enable lab-on-a-chip biotechnology.BN/Cees Dekker La

A nanopore-powered DNA turbine

Rotary motors play a key role in the transduction of energy, from macroscale windmills to nanoscale turbines such as ATP synthase in cells. Here, we demonstrate a rationally designed nanoscale DNA-origami turbine with three chiral blades that uses a transmembrane electrochemical potential across a nanopore to drive a DNA bundle into sustained unidirectional rotations of ~10 revolutions/s. All-atom molecular-dynamics simulations show how 20 hydrodynamic flows drive this turbine. The rotation direction is set by the designed chirality of the turbine, whereas at high salt concentrations, DNA-bound ions can reverse the flow and hence the rotation direction. Our artificial turbines operate autonomously in physiological conditions and convert energy from naturally abundant electrochemical potentials into mechanical work. The results open new possibilities for engineering active robotics at the nanoscale

A DNA turbine powered by a transmembrane potential across a nanopore

Rotary motors play key roles in energy transduction, from macroscale windmills to nanoscale turbines such as ATP synthase in cells. Despite our abilities to construct engines at many scales, developing functional synthetic turbines at the nanoscale has remained challenging. Here, we experimentally demonstrate rationally designed nanoscale DNA origami turbines with three chiral blades. These DNA nanoturbines are 24–27 nm in height and diameter and can utilize transmembrane electrochemical potentials across nanopores to drive DNA bundles into sustained unidirectional rotations of up to 10 revolutions s−1. The rotation direction is set by the designed chirality of the turbine. All-atom molecular dynamics simulations show how hydrodynamic flows drive this turbine. At high salt concentrations, the rotation direction of turbines with the same chirality is reversed, which is explained by a change in the anisotropy of the electrophoretic mobility. Our artificial turbines operate autonomously in physiological conditions, converting energy from naturally abundant electrochemical potentials into mechanical work. The results open new possibilities for engineering active robotics at the nanoscale.BN/Cees Dekker LabRST/Storage of Electrochemical Energ