Search

Protein unfolding and translocation through membrane pores occurs in several biological processes and has implications in nanopore technologies. Here, the authors show that the kinetics of unfolding differ depending on which end of the chain enters the pore first.

The development of tiny, soft and biocompatible batteries to power minimally invasive biomedical devices is of critical importance. Here the authors present a microscale soft rechargeable lithium-ion battery based on the lipid-supported assembly of silk hydrogel droplets that enables a variety of biomedical applications.

Tiny holes have been drilled through individual layers of graphene — atomically thin sheets of carbon — using an electron beam. These nanopores might be useful for the ultrarapid sequencing of single DNA molecules.

Soft bioelectronic devices have exciting potential applications in robotics, computing and medicine, but they are typically restricted by the requirement for tethers or stiff electrodes. Now, a synthetic nerve has been developed that is bioinspired, wireless and powered by light. By patterning functionalized lipid membrane compartments, information was directionally conveyed using electrochemical signals.

The discrimination of nucleic acid sequences and the detection of sequence-specific nucleic acid binding events by protein nanopores can be parallelized by optically encoding the ionic flux through the pores.

The stepwise stochastic motion of an individual organoarsenic(III) molecule along a linear track of thiols can be monitored in real time within a protein nanopore.

When anchored inside a protein pore, the bond-making and bond-breaking events of a single reacting molecule can be detected by alterations in current flow. This approach is used to detect a hydrogen–deuterium kinetic isotope effect. The single-molecule measurements provide information not available from experiments on an ensemble system.

A protein nanopore with a permanent adaptor molecule can continuously identify unlabelled DNA bases with ∼99.8% accuracy. This level of performance could provide the foundation for the development of nanopore-based DNA sequencing technologies that are faster and less expensive than existing approaches.

A nanoreactor approach has now been used to investigate the substitution reactions of arsenic(III) compounds with thiols at the single-molecule level. The rates of interconversion of seven reaction components are tracked, revealing the stereochemistry of sulfur–sulfur substitution at an arsenic centre.

Here the authors present photo-nanopores in which α-haemolysin monomers are modified with arylazopyrazoles, allowing quantitative photoswitching of the transmembrane ionic current, analogous to electronic diodes and light-tunable resistors in response to light.

Pore-forming proteins are deadly biological weapons that punch holes in target-cell membranes. The structure of the pore formed by a bacterial toxin suggests that diverse pore formers have similar assembly pathways.

A study describes the development of a miniaturized hydrogel-based soft power source capable of modulating the activity of networks of neuronal cells without the need for metal electrodes.

A protein nanopore can distinguish model proteins phosphorylated at adjacent sites.

Aqueous droplets connected by single lipid bilayers have been used to examine the properties of protein channels and pores, and networks of droplets can form microscale batteries and detect light. Now, by inserting an engineered pore with diode-like properties into the interface bilayers, droplet networks that mimic simple electronic devices have been produced.

Brain injuries can result in significant damage to the cerebral cortex, and restoring the cellular architecture of the tissue remains challenging. Here, the authors use a droplet printing technique to fabricate a simplified human cerebral cortical column and demonstrate its functionality and potential for future personalized therapy approaches.

Electro-osmosis in an anion-selective α-hemolysin nanopore is used to capture, unfold and transport polypeptides of over 1,200 residues, which allows the mapping of post-translational modifications in polypeptide chains by monitoring the ionic current at a single-molecule resolution.

Capsular polysaccharides are a protective layer enveloping pathogenic bacteria. Understanding their export could guide the design of therapeutics that render bacteria vulnerable to attack by the immune system or other therapeutic agents. Now, a synthetic strategy of polyglycosylation has been developed to obtain defined capsular polysaccharide fragments. Subsequent nanolitre detection enables their export to be studied at the single-molecule level.

An important challenge in the bottom-up fabrication of artificial tissues is communication between compartments bounded by lipid bilayers. Mantri et al. engineer a dimeric transmembrane pore that, like eukaryotic gap junctions, can form a conductive pathway between adjacent bilayers.

Site-selective chemistry is performed on a polymer confined and extended in a nanotube by controlling the spatial alignment of the reactive groups.

Precise patterning of lipid-stabilised aqueous droplets is a key challenge in building synthetic tissue designs. Here, the authors show how the interactions between pairs of droplets direct the packing of droplets within 3D-printed networks, enabling the formation of synthetic tissues with high-resolution features.

DNA nanorings serve as scaffolds to aid the self-assembly of nanopores from Wza peptides.

Responsive hydrogels are of interest for a range of potential applications, including microscale soft robotic and biomedical devices. Now, a versatile fabrication approach has been developed to prepare patterned, multi-material and multi-responsive hydrogels. Pre-gel droplets are connected through lipid bilayers in predetermined architectures and photopolymerized to yield continuous hydrogel structures that respond to a variety of stimuli.

The unfolding pathway of a model protein during translocation through a transmembrane pore differs from that in solution.

The assembly of transmembrane barrels formed from short synthetic peptides has not been previously demonstrated. Now, a transmembrane pore has been fabricated via the self-assembly of peptides. The 35-amino-acid α-helical peptides are based on the C-terminal D4 domain of the Escherichia coli polysaccharide transporter Wza.

Capsular polysaccharides (CPS) enclose many pathogenic strains of Escherichia coli, protecting the bacteria from the host. Here, an extracellular blocker of Wza, a pore-forming protein that transports CPS to the cell surface, has been discovered by single-channel electrical recording. Treatment with the blocker exposes the bacterial cell surface and thereby facilitates killing by the human immune system.

The spatial arrangement of bacterial strains and species within microbial communities is considered crucial for their ecology. Here, Krishna Kumar et al. use a droplet-based printing method to arrange different bacterial genotypes across a sub-millimetre array, and show that micron-scale changes in spatial distributions can drive major shifts in ecology.

Large DNA molecules are rapidly loaded into nanoscale wells from dilute solution for single-molecule sequencing.

Water droplets assembled into defined networks communicate with each other, and with the external aqueous environment, through protein nanopores.

A single α-haemolysin protein is inserted into a solid-state nanopore to form a hybrid structure that is potentially more suited towards creating wafer-scale device arrays for genomic sequencing and protein studies.

Ion channels have essential roles in the nervous system. An engineered ligand-gated channel with a photoactivated switch will be useful for addressing several issues in neuronal signaling.

Gram-negative bacteria assemble biofilms from amyloid fibres, which translocate across the outer membrane as unfolded amyloid precursors through a secretion system. Here, the authors characterise the structural details of the amyloid transporter FapF in Pseudomonas.

A key to understanding bacterial pathogenicity is the mechanism by which water-soluble protein toxins assemble on cell membranes to form oligomeric bilayer-spanning pores. The recent reconstructions from cryo-electron micrographs of three-dimensional pore and prepore structures of the cholesterol-dependent toxin pneumolysin shed new light on the later steps of the assembly of large toxin pores.

The de novo design of functional membrane proteins is a formidable challenge. Now, water-soluble peptides have been designed that assemble into α-helical barrels with accessible, polar and hydrated central channels. Insights from these structures have been used to produce stable membrane-spanning, cation-selective channels.

Crystallographic, biophysical and in silico analyses indicate that the conformational state of the mechanosensitive channel MscS is determined by the reorganization, due to changes in membrane tension, of the lipids within and around the protein.