SARS-CoV-2-derived peptides define heterologous and COVID-19-induced T cell recognition.

T cell immunity is central for the control of viral infections. To characterize T cell immunity, but also for the development of vaccines, identification of exact viral T cell epitopes is fundamental. Here we identify and characterize multiple dominant and subdominant SARS-CoV-2 HLA class I and HLA-DR peptides as potential T cell epitopes in COVID-19 convalescent and unexposed individuals. SARS-CoV-2-specific peptides enabled detection of post-infectious T cell immunity, even in seronegative convalescent individuals. Cross-reactive SARS-CoV-2 peptides revealed pre-existing T cell responses in 81% of unexposed individuals and validated similarity with common cold coronaviruses, providing a functional basis for heterologous immunity in SARS-CoV-2 infection. Diversity of SARS-CoV-2 T cell responses was associated with mild symptoms of COVID-19, providing evidence that immunity requires recognition of multiple epitopes. Together, the proposed SARS-CoV-2 T cell epitopes enable identification of heterologous and post-infectious T cell immunity and facilitate development of diagnostic, preventive and therapeutic measures for COVID-19.

Structural Basis for Polyproline-Mediated Ribosome Stalling and Rescue by the Translation Elongation Factor EF-P.

Ribosomes synthesizing proteins containing consecutive proline residues become stalled and require rescue via the action of uniquely modified translation elongation factors, EF-P in bacteria, or archaeal/eukaryotic a/eIF5A. To date, no structures exist of EF-P or eIF5A in complex with translating ribosomes stalled at polyproline stretches, and thus structural insight into how EF-P/eIF5A rescue these arrested ribosomes has been lacking. Here we present cryo-EM structures of ribosomes stalled on proline stretches, without and with modified EF-P. The structures suggest that the favored conformation of the polyproline-containing nascent chain is incompatible with the peptide exit tunnel of the ribosome and leads to destabilization of the peptidyl-tRNA. Binding of EF-P stabilizes the P-site tRNA, particularly via interactions between its modification and the CCA end, thereby enforcing an alternative conformation of the polyproline-containing nascent chain, which allows a favorable substrate geometry for peptide bond formation.

The Myxobacterial Antibiotic Myxovalargin: Biosynthesis, Structural Revision, Total Synthesis, and Molecular Characterization of Ribosomal Inhibition.

Resistance of bacterial pathogens against antibiotics is declared by WHO as a major global health threat. As novel antibacterial agents are urgently needed, we re-assessed the broad-spectrum myxobacterial antibiotic myxovalargin and found it to be extremely potent against Mycobacterium tuberculosis. To ensure compound supply for further development, we studied myxovalargin biosynthesis in detail enabling production via fermentation of a native producer. Feeding experiments as well as functional genomics analysis suggested a structural revision, which was eventually corroborated by the development of a concise total synthesis. The ribosome was identified as the molecular target based on resistant mutant sequencing, and a cryo-EM structure revealed that myxovalargin binds within and completely occludes the exit tunnel, consistent with a mode of action to arrest translation during a late stage of translation initiation. These studies open avenues for structure-based scaffold improvement toward development as an antibacterial agent.

Radio-Frequency Manipulation of State Populations in an Entangled Fluorine-Muon-Fluorine System.

Entangled spin states are created by implanting muons into single-crystal LiY_{0.95}Ho_{0.05}F_{4} to form a cluster of correlated, dipole-coupled local magnetic moments. The resulting states have well-defined energy levels allowing experimental manipulation of the state populations by electromagnetic excitation. Experimental control of the evolution of the muon spin polarization is demonstrated through application of continuous, radio-frequency electromagnetic excitation fields. A semiclassical model of quantum, dipole-coupled spins interacting with a classical, oscillating magnetic field accounts for the muon spin evolution. On application of the excitation field, this model shows how changes in the state populations lead to the experimentally observed effects, thus enabling a spectroscopic probe of entangled spin states with muons.

Single-layer MoS2 nanopores as nanopower generators.

Making use of the osmotic pressure difference between fresh water and seawater is an attractive, renewable and clean way to generate power and is known as 'blue energy'. Another electrokinetic phenomenon, called the streaming potential, occurs when an electrolyte is driven through narrow pores either by a pressure gradient or by an osmotic potential resulting from a salt concentration gradient. For this task, membranes made of two-dimensional materials are expected to be the most efficient, because water transport through a membrane scales inversely with membrane thickness. Here we demonstrate the use of single-layer molybdenum disulfide (MoS2) nanopores as osmotic nanopower generators. We observe a large, osmotically induced current produced from a salt gradient with an estimated power density of up to 10(6) watts per square metre--a current that can be attributed mainly to the atomically thin membrane of MoS2. Low power requirements for nanoelectronic and optoelectric devices can be provided by a neighbouring nanogenerator that harvests energy from the local environment--for example, a piezoelectric zinc oxide nanowire array or single-layer MoS2 (ref. 12). We use our MoS2 nanopore generator to power a MoS2 transistor, thus demonstrating a self-powered nanosystem.

A role for the Saccharomyces cerevisiae ABCF protein New1 in translation termination/recycling.

Translation is controlled by numerous accessory proteins and translation factors. In the yeast Saccharomyces cerevisiae, translation elongation requires an essential elongation factor, the ABCF ATPase eEF3. A closely related protein, New1, is encoded by a non-essential gene with cold sensitivity and ribosome assembly defect knock-out phenotypes. Since the exact molecular function of New1 is unknown, it is unclear if the ribosome assembly defect is direct, i.e. New1 is a bona fide assembly factor, or indirect, for instance due to a defect in protein synthesis. To investigate this, we employed yeast genetics, cryo-electron microscopy (cryo-EM) and ribosome profiling (Ribo-Seq) to interrogate the molecular function of New1. Overexpression of New1 rescues the inviability of a yeast strain lacking the otherwise strictly essential translation factor eEF3. The structure of the ATPase-deficient (EQ2) New1 mutant locked on the 80S ribosome reveals that New1 binds analogously to the ribosome as eEF3. Finally, Ribo-Seq analysis revealed that loss of New1 leads to ribosome queuing upstream of 3'-terminal lysine and arginine codons, including those genes encoding proteins of the cytoplasmic translational machinery. Our results suggest that New1 is a translation factor that fine-tunes the efficiency of translation termination or ribosome recycling.

Structural basis for antibiotic resistance mediated by the Bacillus subtilis ABCF ATPase VmlR.

Many Gram-positive pathogenic bacteria employ ribosomal protection proteins (RPPs) to confer resistance to clinically important antibiotics. In Bacillus subtilis, the RPP VmlR confers resistance to lincomycin (Lnc) and the streptogramin A (SA) antibiotic virginiamycin M (VgM). VmlR is an ATP-binding cassette (ABC) protein of the F type, which, like other antibiotic resistance (ARE) ABCF proteins, is thought to bind to antibiotic-stalled ribosomes and promote dissociation of the drug from its binding site. To investigate the molecular mechanism by which VmlR confers antibiotic resistance, we have determined a cryo-electron microscopy (cryo-EM) structure of an ATPase-deficient B. subtilis VmlR-EQ2 mutant in complex with a B. subtilis ErmDL-stalled ribosomal complex (SRC). The structure reveals that VmlR binds within the E site of the ribosome, with the antibiotic resistance domain (ARD) reaching into the peptidyltransferase center (PTC) of the ribosome and a C-terminal extension (CTE) making contact with the small subunit (SSU). To access the PTC, VmlR induces a conformational change in the P-site tRNA, shifting the acceptor arm out of the PTC and relocating the CCA end of the P-site tRNA toward the A site. Together with microbiological analyses, our study indicates that VmlR allosterically dissociates the drug from its ribosomal binding site and exhibits specificity to dislodge VgM, Lnc, and the pleuromutilin tiamulin (Tia), but not chloramphenicol (Cam), linezolid (Lnz), nor the macrolide erythromycin (Ery).

Bifunctional Nitrone-Conjugated Secondary Metabolite Targeting the Ribosome.

Many microorganisms possess the capacity for producing multiple antibiotic secondary metabolites. In a few notable cases, combinations of secondary metabolites produced by the same organism are used in important combination therapies for treatment of drug-resistant bacterial infections. However, examples of conjoined roles of bioactive metabolites produced by the same organism remain uncommon. During our genetic functional analysis of oxidase-encoding genes in the everninomicin producer Micromonospora carbonacea var. aurantiaca, we discovered previously uncharacterized antibiotics everninomicin N and O, comprised of an everninomicin fragment conjugated to the macrolide rosamicin via a rare nitrone moiety. These metabolites were determined to be hydrolysis products of everninomicin P, a nitrone-linked conjugate likely the result of nonenzymatic condensation of the rosamicin aldehyde and the octasaccharide everninomicin F, possessing a hydroxylamino sugar moiety. Rosamicin binds the erythromycin macrolide binding site approximately 60 Å from the orthosomycin binding site of everninomicins. However, while individual ribosomal binding sites for each functional half of everninomicin P are too distant for bidentate binding, ligand displacement studies demonstrated that everninomicin P competes with rosamicin for ribosomal binding. Chemical protection studies and structural analysis of everninomicin P revealed that everninomicin P occupies both the macrolide- and orthosomycin-binding sites on the 70S ribosome. Moreover, resistance mutations within each binding site were overcome by the inhibition of the opposite functional antibiotic moiety binding site. These data together demonstrate a strategy for coupling orthogonal antibiotic pharmacophores, a surprising tolerance for substantial covalent modification of each antibiotic, and a potential beneficial strategy to combat antibiotic resistance.

Transverse Detection of DNA Using a MoS2 Nanopore.

Classical nanopore sensing relies on the measurement of the ion current passing through a nanopore. Whenever a molecule electrophoretically translocates through the narrow constriction, it modulates the ion current. Although this approach allows one to measure single molecules, the access resistance limits the spatial resolution. This physical limitation could potentially be overcome by an alternative sensing scheme taking advantage of the current across the membrane material itself. Such an electronic readout would also allow better temporal resolution than the ionic current. In this work, we present the fabrication of an electrically contacted molybdenum disulfide (MoS2) nanoribbon integrated with a nanopore. DNA molecules are sensed by correlated signals from the ionic current through the nanopore and the transverse current through the nanoribbon. The resulting signal suggests a field-effect sensing scheme where the charge of the molecule is directly sensed by the nanoribbon. We discuss different sensing schemes such as local potential sensing and direct charge sensing. Furthermore, we show that the fabrication of freestanding MoS2 ribbons with metal contacts is reliable and discuss the challenges that arise in the fabrication and usage of these devices.

Clinical Outcome After Rectal Replacement With Side-to-End, Colon-J-Pouch, or Straight Colorectal Anastomosis Following Total Mesorectal Excision: A Swiss Prospective, Randomized, Multicenter Trial (SAKK 40/04).

OBJECTIVE: To compare, in a phase 3, prospective, randomized, multi-center clinical trial functional outcome of reconstruction procedures following total mesorectal excision (TME). SUMMARY BACKGROUND DATA: Intestinal continuity reconstruction following TME is accompanied by postoperative defecation dysfunctions known as "anterior resection syndrome." Commonly used reconstruction techniques are straight colorectal anastomosis (SCA), colon J -pouch (CJP), and side-to-end anastomosis (SEA). Comparison of their functional outcomes in prospective, randomized, multi-center studies, including long-term assessments, is lacking. METHODS: Patients requiring TME for histologically proven rectal tumor, with or without neoadjuvant treatment, age ≥ 18 years, normal sphincter function without history of incontinence, any pretreatment staging or adenoma, expected R0-resection, were randomized for standardized SCA, CJP, or SEA procedures. Primary endpoint was comparison of composite evacuation scores 12 months after TME. Comparison of composite evacuation and incontinence scores at 6, 18 and 24 months after surgery, morbidity, and overall survival represented secondary endpoints. Analysis was based on "per protocol" (PP) population, fully complying with trial requirements, and intention-to treat (ITT) population. RESULTS: Three hundred thirty-six patients from 15 hospitals were randomized. PP population included 257 patients (JCP = 63; SEA = 95; SCA = 99). Composite evacuation scores of PP and ITT populations did not show statistically significant differences among the 3 groups at any time point. Similarly, composite incontinence scores for PP and ITT populations showed no statistically significant difference among the 3 trial arms at any time point. CONCLUSIONS: Within boundaries of investigated procedures, surgeons in charge may continue to perform reconstruction of intestinal continuity following TME at their technical preference.

Quality of Life After Total Mesorectal Excision and Rectal Replacement: Comparing Side-to-End, Colon J-Pouch and Straight Colorectal Reconstruction in a Randomized, Phase III Trial (SAKK 40/04).

BACKGROUND: Functional outcomes of different reconstruction techniques have an impact on patients' quality of life (QoL), but information on long-term QoL is lacking. We compared QoL among three reconstruction techniques after total mesorectal excision (TME). METHODS: Quality of life was assessed within a randomized, multicenter trial comparing rectal surgery using side-to-end anastomosis (SEA), colon J-pouch (CJP), and straight colorectal anastomosis (SCA) by the Functional Assessment of Cancer Therapy-Colorectal scale (FACT-C) before randomization and every 6 months up to 2 years post-TME. The primary QoL endpoint was the change in the Trial Outcome Index (TOI), including the FACT-C subscales of physical and functional well-being and colorectal cancer symptoms (CSS), from baseline to month 12. Pair-wise comparisons of changes from baseline (presurgery) to each timepoint between the three arms were analyzed by Mann-Whitney tests. RESULTS: For the QoL analysis, 257 of 336 randomized patients were in the per protocol evaluation (SEA = 95; CJP = 63; SCA = 99). Significant differences between the reconstruction techniques were found for selected QoL scales up to 12 months, all in favor of CJP. Patients with SEA or SCA reported a clinically relevant deterioration for TOI and CSS at 6 months, those with SCA for CSS also at 12 months after TME. Patients with CJP remained stable. CONCLUSIONS: Although the three reconstruction techniques differ in their effects on QoL at months 6 and 12, these differences did not persist over the whole observation period of 24 months. Patients with a colon J-pouch may benefit with respect to QoL in the short-term.

High-dose Anderson operation for nystagmus-related anomalous head turn.

PURPOSE: To evaluate the effectiveness of a high-dose Anderson procedure (AP) to correct infantile nystagmus-related anomalous head turn (HT). METHODS: Twenty-nine consecutive orthotropes with infantile nystagmus with and without associated sensory defect received high-dose AP. HT was measured while the patient tried to read letters at best-corrected visual acuity (BCVA) level at 5 m and 0.3 m. BCVA, binocular vision (BV), and alignment (prism and cover test) were measured. High-dose AP with recessions of 9-16 mm was performed. All measures were taken before and 3-6 and ≥ 8 months post surgery. Success was defined by postoperative HT ≤ 10°/HT ≤ 15°. RESULTS: Medians and ranges (minimum-maximum) were:. Age at surgery was 7 years (4-44). HT at 5 m and HT at 0.3 m were 35° (20-40) and 20° (0-35), respectively. After 4 months (3-6), HT was 10° (- 3-20) and 5° (- 5-20); success rates were 74%/96% and 83%/96%. After 15 months (8-45), HT was 12° (0-20) and 6° (0-15); success rates were 46%/75% and 92%/100%; residual HT > 15° occurred in 5/9 cases with recessions < 13 mm and 1/15 cases with recessions ≥ 13 mm. With recessions ≥ 13 mm, 60% (95% confidence intervals (C.I.), 33-83%) achieved HT ≤ 10° and 93% (95% C.I. 66-99%) achieved HT ≤ 15°. Overcorrection did not occur. Anomalous head posture components in vertical and frontal planes did not improve. Residual motility was 30° (10-45). The mean BCVA improved by only 0.037 logMAR (p = 0.06). BV and ocular alignment were constant, except in 2 patients whose exophoria decompensated. CONCLUSIONS: Kestenbaum surgery is a common procedure to correct infantile nystagmus-related HT. Anderson surgery is confined to bilateral yoke muscle recession; hence, less invasive but nevertheless comparably effective, high dosage is provided.

Splitting of the lateral rectus muscle with medial transposition to treat oculomotor palsy: a retrospective analysis of 29 consecutive cases.

PURPOSE: The lateralis splitting technique has been an interesting option for treating large-angle exotropia due to complete 3rd nerve paralysis since its inception in the early 1990s. The purpose of this study is to report on our experience regarding the effectiveness and complications of this method. METHODS: Retrospective analysis of a consecutive series of 29 patients operated by one single experienced surgeon and examined according to a specific operative and perioperative protocol. Patients were examined preoperatively, on the 2nd day and 3rd month after surgery. Outcome measures include strabismus angle, horizontal motility, head turn, binocular function, and incidence and resolution of postoperative serous retinal detachment as seen with infrared imaging and spectral domain optical coherence tomography (SD-OCT). RESULTS: Surgery brought about a large and stable reduction of strabismus angle and head turn. It reduced horizontal motility, but moved the range of monocular excursion much closer to center. Eighty percent of patients with constant diplopia acquired some fields of single binocular vision. A significant number of cases (33.3%) developed transitory serous retinal detachment with varying onset and extent. CONCLUSION: This is by far the largest published study regarding the outcome of lateralis splitting in NIII palsy. The procedure is difficult, yet a very useful option. Serous detachment is a serious complication, but usually transitory. Its cause and mechanisms are not fully understood and warrant further investigation.

Cryo-EM structure of the spinach chloroplast ribosome reveals the location of plastid-specific ribosomal proteins and extensions.

Ribosomes are the protein synthesizing machines of the cell. Recent advances in cryo-EM have led to the determination of structures from a variety of species, including bacterial 70S and eukaryotic 80S ribosomes as well as mitoribosomes from eukaryotic mitochondria, however, to date high resolution structures of plastid 70S ribosomes have been lacking. Here we present a cryo-EM structure of the spinach chloroplast 70S ribosome, with an average resolution of 5.4 Å for the small 30S subunit and 3.6 Å for the large 50S ribosomal subunit. The structure reveals the location of the plastid-specific ribosomal proteins (RPs) PSRP1, PSRP4, PSRP5 and PSRP6 as well as the numerous plastid-specific extensions of the RPs. We discover many features by which the plastid-specific extensions stabilize the ribosome via establishing additional interactions with surrounding ribosomal RNA and RPs. Moreover, we identify a large conglomerate of plastid-specific protein mass adjacent to the tunnel exit site that could facilitate interaction of the chloroplast ribosome with the thylakoid membrane and the protein-targeting machinery. Comparing the Escherichia coli 70S ribosome with that of the spinach chloroplast ribosome provides detailed insight into the co-evolution of RP and rRNA.

Intracellular Antimicrobial Peptides Targeting the Protein Synthesis Machinery.

While antimicrobial peptides (AMPs) are well-known for their disruptive effects on bacterial membranes, the mechanism of many intracellular AMPs is still being elucidated. In the recent years, it has been demonstrated that the subclass of proline-rich AMPs (PrAMPs) can pass through the bacterial membrane and kill bacteria by inhibiting protein synthesis. PrAMPs are a product of the innate immune system and are secreted in response to bacterial infection. So far PrAMPs have been identified in many arthropods, such as beetles, wasps, and flies, as well as some mammals, such as sheep, cows, and goats. PrAMPs show high potency against Gram-negative bacteria, while exhibiting low toxicity in eukaryotes, suggesting that they may represent a promising avenue for the development of future antimicrobial agents to combat the increase of multidrug-resistant bacterial pathogens. Structural and biochemical data have revealed the PrAMP binding sites on the ribosome as well as insight into their mechanisms of action. While the binding site of all so far investigated PrAMPs is situated within nascent polypeptide exit tunnel, the mechanism of action is distinct between class I and II PrAMPs. Specifically, class I PrAMPs, such as Bac7, Onc112, pyrrhocoricin, and metalnikowin, block the delivery of aa-tRNA by EF-Tu to the ribosomal A-site, whereas the class II PrAMPs, such as apidaecin 1b and Api137, act during translation termination and inhibit protein synthesis by trapping of release factors on the 70S ribosome following hydrolysis of the nascent polypeptide chain.

Structures of the orthosomycin antibiotics avilamycin and evernimicin in complex with the bacterial 70S ribosome.

The ribosome is one of the major targets for therapeutic antibiotics; however, the rise in multidrug resistance is a growing threat to the utility of our current arsenal. The orthosomycin antibiotics evernimicin (EVN) and avilamycin (AVI) target the ribosome and do not display cross-resistance with any other classes of antibiotics, suggesting that they bind to a unique site on the ribosome and may therefore represent an avenue for development of new antimicrobial agents. Here we present cryo-EM structures of EVN and AVI in complex with the Escherichia coli ribosome at 3.6- to 3.9-Å resolution. The structures reveal that EVN and AVI bind to a single site on the large subunit that is distinct from other known antibiotic binding sites on the ribosome. Both antibiotics adopt an extended conformation spanning the minor grooves of helices 89 and 91 of the 23S rRNA and interacting with arginine residues of ribosomal protein L16. This binding site overlaps with the elbow region of A-site bound tRNA. Consistent with this finding, single-molecule FRET (smFRET) experiments show that both antibiotics interfere with late steps in the accommodation process, wherein aminoacyl-tRNA enters the peptidyltransferase center of the large ribosomal subunit. These data provide a structural and mechanistic rationale for how these antibiotics inhibit the elongation phase of protein synthesis.

Orthogonal Tip-to-Tip Nanocapillary Alignment Allows for Easy Detection of Fluorescent Emitters in Femtomolar Concentrations.

Here we present the realization of a novel fluorescence detection method based on the electromigration of fluorescent molecules within a nanocapillary combined with the laser excitation through a platinum (Pt)-coated nanocapillary. By using the Pt nanocapillary assisted focusing of a laser beam, we completely remove the background scattering on the tip of the electrophoretic nanocapillary. In this excitation geometry, we demonstrate a 1000-fold sensitivity enhancement (1.0 nM to 1.0 pM) compared to the detection in microcapillaries with epifluorescence illumination and fluorescence spectrophotometry. Due to a significant electroosmotic flow, we observe a decelerating migration of DNA molecules close to the tip of the electrophoretic nanocapillary. The reduced DNA translocation velocity causes a two-step stacking process of molecules in the tip of the nanocapillary and can be used as a way to locally concentrate molecules. The sensitivity of our method is further improved by a continuous electrokinetic injection of DNA molecules followed by sample zone stacking on the tip of the nanocapillary. Concentrations ranging from 0.1 pM to 1.0 fM can be directly observed on the orifice of the electrophoretic nanocapillary. This is a 1000-fold improvement compared to traditional capillary electrophoresis with laser-induced fluorescence.

Structure of the mammalian antimicrobial peptide Bac7(1-16) bound within the exit tunnel of a bacterial ribosome.

Proline-rich antimicrobial peptides (PrAMPs) produced as part of the innate immune response of animals, insects and plants represent a vast, untapped resource for the treatment of multidrug-resistant bacterial infections. PrAMPs such as oncocin or bactenecin-7 (Bac7) interact with the bacterial ribosome to inhibit translation, but their supposed specificity as inhibitors of bacterial rather than mammalian protein synthesis remains unclear, despite being key to developing drugs with low toxicity. Here, we present crystal structures of the Thermus thermophilus 70S ribosome in complex with the first 16 residues of mammalian Bac7, as well as the insect-derived PrAMPs metalnikowin I and pyrrhocoricin. The structures reveal that the mammalian Bac7 interacts with a similar region of the ribosome as insect-derived PrAMPs. Consistently, Bac7 and the oncocin derivative Onc112 compete effectively with antibiotics, such as erythromycin, which target the ribosomal exit tunnel. Moreover, we demonstrate that Bac7 allows initiation complex formation but prevents entry into the elongation phase of translation, and show that it inhibits translation on both mammalian and bacterial ribosomes, explaining why this peptide needs to be stored as an inactive pro-peptide. These findings highlight the need to consider the specificity of PrAMP derivatives for the bacterial ribosome in future drug development efforts.

Proline-rich antimicrobial peptides targeting protein synthesis.

Covering: up to 2017The innate immune system employs a broad array of antimicrobial peptides (AMPs) to attack invading microorganisms. While most AMPs act by permeabilizing the bacterial membrane, specific subclasses of AMPs have been identified that pass through membranes and inhibit bacterial growth by targeting fundamental intracellular processes. One such subclass is the proline-rich antimicrobial peptides (PrAMPs) that bind to the ribosome and interfere with the process of protein synthesis. A diverse range of PrAMPs have been identified in insects, such as bees, wasps and beetles, and crustaceans, such as crabs, as well as in mammals, such as cows, sheep, goats and pigs. Mechanistically, the best-characterized PrAMPs are the insect oncocins, such as Onc112, and bovine bactenecins, such as Bac7. Biochemical and structural studies have revealed that these PrAMPs bind within the ribosomal exit tunnel with a reverse orientation compared to a nascent polypeptide chain. The PrAMPs allow initiation but prevent the transition into the elongation phase of translation. Insight into the interactions of PrAMPs with their ribosomal target provides the opportunity to further develop these peptides as novel antimicrobial agents.

Observation of ionic Coulomb blockade in nanopores.

Emergent behaviour from electron-transport properties is routinely observed in systems with dimensions approaching the nanoscale. However, analogous mesoscopic behaviour resulting from ionic transport has so far not been observed, most probably because of bottlenecks in the controlled fabrication of subnanometre nanopores for use in nanofluidics. Here, we report measurements of ionic transport through a single subnanometre pore junction, and the observation of ionic Coulomb blockade: the ionic counterpart of the electronic Coulomb blockade observed for quantum dots. Our findings demonstrate that nanoscopic, atomically thin pores allow for the exploration of phenomena in ionic transport, and suggest that nanopores may also further our understanding of transport through biological ion channels.