There is a great interest in reducing the toxicity of the fuel used to self-propel artificial nanomachines. Therefore, a method to increase the efficiency of the conversion of chemicals into mechanical energy is desired. Here, we employed temperature control to increase the efficiency of microjet engines while simultaneously reducing the amount of peroxide fuel needed. At physiological temperatures, i.e. 37 °C, only 0.25% H(2)O(2) is needed to propel the microjets at 140 μm s(-1), which corresponds to three body lengths per second. In addition, at 5% H(2)O(2), the microjets acquire superfast speeds, reaching 10 mm s(-1). The dynamics of motion is altered when the speed is increased; i.e., the motion deviates from linear to curvilinear trajectories. The observations are modeled empirically.

Self-folded magnetic microtools with sharp ends are directed at enabling drilling and related incision operations of tissues, ex vivo, in a fluid with a viscosity similar to that of blood. These microtools change their rotation from a horizontal to a vertical one when they are immersed into a rotational magnetic field. Novel self-assembly paradigms with magnetic materials can enable the creation of remotely controlled and mass-produced tools for potential applications in minimally invasive surgery.

Nuclear pore complexes (NPCs) lined with intrinsically disordered FG-domains act as selective gatekeepers for molecular transport between the nucleus and the cytoplasm in eukaryotic cells. The underlying physical mechanism of the intriguing selectivity is still under debate. Here, we probe the transport of ions and transport receptors through biomimetic NPCs consisting of Nsp1 domains attached to the inner surface of solid-state nanopores. We examine both wildtype FG-domains and hydrophilic SG-mutants. FG-nanopores showed a clear selectivity as transport receptors can translocate across the pore whereas other proteins cannot. SG mutant pores lack such selectivity. To unravel this striking difference, we present coarse-grained molecular dynamics simulations that reveal that FG-pores exhibit a high-density, nonuniform protein distribution, in contrast to a uniform and significantly less-dense protein distribution in the SG-mutant. We conclude that the sequence-dependent density distribution of disordered proteins inside the NPC plays a key role for its conductivity and selective permeability.

The nuclear pore complex (NPC) is the gatekeeper for nuclear transport in eukaryotic cells. A key component of the NPC is the central shaft lined with intrinsically disordered proteins (IDPs) known as FG-Nups, which control the selective molecular traffic. Here, we present an approach to realize artificial NPC mimics that allows controlling the type and copy number of FG-Nups. We constructed 34 nm-wide 3D DNA origami rings and attached different numbers of NSP1, a model yeast FG-Nup, or NSP1-S, a hydrophilic mutant. Using (cryo) electron microscopy, we find that NSP1 forms denser cohesive networks inside the ring compared to NSP1-S. Consistent with this, the measured ionic conductance is lower for NSP1 than for NSP1-S. Molecular dynamics simulations reveal spatially varying protein densities and conductances in good agreement with the experiments. Our technique provides an experimental platform for deciphering the collective behavior of IDPs with full control of their type and position.

While DNA origami is a popular and versatile platform, its structural properties are still poorly understood. In this study we use solid-state nanopores to investigate the ionic permeability and mechanical properties of DNA origami nanoplates. DNA origami nanoplates of various designs are docked onto solid-state nanopores where we subsequently measure their ionic conductance. The ionic permeability is found to be high for all origami nanoplates. We observe the conductance of docked nanoplates, relative to the bare nanopore conductance, to increase as a function of pore diameter, as well as to increase upon lowering the ionic strength. The honeycomb lattice nanoplate is found to have slightly better overall performance over other plate designs. After docking, we often observe spontaneous discrete jumps in the current, a process which can be attributed to mechanical buckling. All nanoplates show a non-linear current-voltage dependence with a lower conductance at higher applied voltages, which we attribute to a physical bending deformation of the nanoplates under the applied force. At sufficiently high voltage (force), the nanoplates are strongly deformed and can be pulled through the nanopore. These data show that DNA origami nanoplates are typically very permeable to ions and exhibit a number of unexpected mechanical properties which are interesting in their own right, but also need to be considered in the future design of DNA origami nanostructures. KeywordsDNA origami; nanopore; ionic permeability; mechanical properties Solid-state-nanopore research 1, 2 is an area which has been gaining much attention due to its potential applications in sequencing, biosensing, and as a tool for biophysics. In this technique an electric field is applied across a membrane containing a single pore. Charged molecules such as DNA experience an electrophoretic force which pulls them through the pore. Molecules are detected by the temporary reduction (or increase at low salt) in the ionic current which they cause as they pass through the pore. Despite recent advances 1, 2 in solid-* Corresponding author.c.dekker@tudelft.nl.

The controlled functionalization of surfaces with proteins is crucial for many analytical methods in life science research and biomedical applications. Here, a coating for silica-based surfaces is established which enables stable and selective immobilization of proteins with controlled orientation and tunable surface density. The coating is reusable, retains functionality upon long-term storage in air, and is applicable to surfaces of complex geometry. The protein anchoring method is validated on planar surfaces, and then a method is developed to measure the anchoring process in real time using silicon nitride solid-state nanopores. For surface attachment, polyhistidine tags that are site specifically introduced into recombinant proteins are exploited, and the yeast nucleoporin Nsp1 is used as model protein. Contrary to the commonly used covalent thiol chemistry, the anchoring of proteins via polyhistidine tag is reversible, permitting to take proteins off and replace them by other ones. Such switching in real time in experiments on individual nanopores is monitored using ion conductivity. Finally, it is demonstrated that silica and gold surfaces can be orthogonally functionalized to accommodate polyhistidine-tagged proteins on silica but prevent protein binding to gold, which extends the applicability of this surface functionalization method to even more complex sensor devices.

While graphene may appear to be the ultimate support membrane for transmission electron microscopy (TEM) imaging of DNA nanostructures, very little is known if it poses an advantage over conventional carbon supports in terms of resolution and contrast. Microscopic investigations are carried out on DNA origami nanoplates that are supported onto freestanding graphene, using advanced TEM techniques, including a new dark-field technique that is recently developed in our lab. TEM images of stained and unstained DNA origami are presented with high contrast on both graphene and amorphous carbon membranes. On graphene, the images of the origami plates show severe unwanted distortions, where the rectangular shape of the nanoplates is significantly distorted. From a number of comparative control experiments, it is demonstrated that neither staining agents, nor screening ions, nor the level of electron-beam irradiation cause this distortion. Instead, it is suggested that origami nanoplates are distorted due to hydrophobic interaction of the DNA bases with graphene upon adsorption of the DNA origami nanoplates.

Super-resolution imaging allows for the visualization of cellular structures on a nanoscale level. DNA-PAINT (DNA point accumulation in nanoscale topology) is a super-resolution method that depends on the binding and unbinding of DNA imager strands. The current DNA-PAINT technique suffers from slow acquisition due to the low binding rate of the imager strands. Here we report on a method where imager strands are loaded into a protein, Argonaute (Ago), which allows for faster binding. Ago preorders the DNA imager strand into a helical conformation, allowing for 10 times faster target binding. Using a 2D DNA origami structure, we demonstrate that Ago-assisted DNA-PAINT (Ago-PAINT) can speed up the current DNA-PAINT technique by an order of magnitude, while maintaining the high spatial resolution. We envision this tool to be useful for super-resolution imaging and other techniques that rely on nucleic acid interactions.