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Mitochondrial ATP synthases form rows of dimers, which induce membrane curvature to give cristae their characteristic lamellar or tubular morphology. The angle formed between the central stalks of ATP synthase dimers varies between species. Using cryo-electron tomography and sub-tomogram averaging, we determined the structure of the ATP synthase dimer from the nematode wormC. elegans.We showed that the angle formed by the ATP synthase dimer is different to previously determined structures. The consequences of species-specific differences at the dimer interface were investigated by comparing mitochondrial morphology betweenC. elegansandS. cerevisiae. We reveal that a larger ATP synthase dimer angle inC. elegansis consequent with more lamellar (flatter) cristae compared to yeast. The underlying cause of this difference was investigated by generating an atomic model of theC. elegansATP synthase dimer by homology modelling and comparing it to an existingS. cerevisiaestructure. We reveal extensions and rearrangements ofC. eleganssubunits that maintain the dimer interface. We propose that increased dimer angles resulting in flatter cristae could provide an energetic advantage for species that inhabit variable-oxygen environments.Significance StatementATP synthase, the world’s smallest rotary motor, generates the energy required for all living processes. The universal formation of ATP synthase dimers in mitochondria induces membrane curvature and cristae formation, generating the famously convoluted inner mitochondrial membrane that maximises ATP production. Intriguingly, the angle between ATP synthase dimers varies between species. Here, we report the discovery of a novel ATP synthase dimer angle in mitochondria from the nematode wormC. elegans,identify a relationship between dimer angle and crista membrane morphology, and exploit AlphaFold homology modelling to investigate associated structural changes. In summary, we have taken steps towards understanding the importance of subunit composition at the ATP synthase dimer interface, providing insights into the origins of this evolutionary divergence.

Phages are viruses that infect bacteria and dominate every ecosystem on our planet. As well as impacting microbial ecology, physiology and evolution, phages are exploited as tools in molecular biology and biotechnology. This is particularly true for the Ff (f1, fd or M13) phages, which represent a widely distributed group of filamentous viruses. Over nearly five decades, Ff has seen an extraordinary range of applications, including in phage display and nanotechnology. However, the complete structure of the phage capsid and consequently the mechanisms of infection and assembly remain largely mysterious. Using cryo-electron microscopy and a highly efficient system for production of short Ff-derived nanorods, we have determined the first structure of a filamentous virus, including the filament tips. Structure combined with mutagenesis was employed to identify domains of the phage that are important in bacterial attack and for release of new phage progeny. These data allow new models to be proposed for the phage lifecycle and will undoubtedly enable the development of novel biotechnological applications.

Surface layers (S-layers) are resilient two-dimensional protein lattices that encapsulate many bacteria and most archaea. In archaea, S-layers usually form the only structural component of the cell wall and thus act as the final frontier between the cell and its environment. Therefore, S-layers are crucial for supporting microbial life. Notwithstanding their importance, little is known about archaeal S-layers at the atomic level. Here, we combined single particle cryo electron microscopy (cryoEM), cryo electron tomography (cryoET) and Alphafold2 predictions to generate an atomic model of the two-component S-layer of Sulfolobus acidocaldarius. The outer component of this S-layer (SlaA) is a flexible, highly glycosylated, and stable protein. Together with the inner and membrane-bound component (SlaB), they assemble into a porous and interwoven lattice. We hypothesize that jackknife-like conformational changes, as well as pH-induced alterations in the surface charge of SlaA, play important roles in S-layer assembly.

Translational control is an essential process for the cell to adapt to varying physiological or environmental conditions. To survive adverse conditions such as low nutrient levels, translation can be shut down almost entirely by inhibiting ribosomal function. Here we investigated eukaryotic hibernating ribosomes from the microsporidian parasite Spraguea lophii in situ by a combination of cryo-electron tomography (cryoET) and single particle cryoEM. We show that microsporidian spores contain ribosomes primed for host cell invasion and thus shed new light on the infection mechanism of this important pathogen. Prior to host infection, virtually all ribosomes are locked in the 100 S dimeric state, which appears to be formed by a unique dimerization mechanism that is distinct from its bacterial counterparts. Within the dimer, the hibernation factor MDF1 is bound within the E site, locking the L1 stalk in a closed conformation, and thus preventing the translation of mRNAs to polypeptides.

Pili are ubiquitous filamentous surface extensions that play crucial roles for bacterial and archaeal cellular processes such as adhesion, biofilm formation, motility, cell-cell communication, DNA uptake and horizontal gene transfer to name a few. Here we report on the discovery and structure of the archaeal thread – a remarkably stable archaeal pilus that belongs to a so-far largely unknown class of protein filaments. We find that the filament is highly glycosylated and interconnected via donor strand complementation, as well as isopeptide bonds, reminiscent of bacterial type I pili. Despite striking structural similarity with bacterial type-1 pili, archaeal threads appear to have evolved independently and are likely assembled by a markedly distinct mechanism.

Archaea swim by means of a unique molecular machine called the archaellum. The archaellum consists of an ATP-powered intracellular motor that drives the rotation of an extracellular filament, allowing the cell to rapidly propel itself through liquid media.The archaellum filament comprises multiple copies of helically organised subunits named archaellins. While in many species several archaellin homologs are encoded in the same operon, structural studies conducted to date have suggested that archaella consist of only one protein species. Thus, the role of the remaining archaellin genes remains elusive.Here we present the structure of the Methanocaldococcus villosus archaellum filament at 3.08 Å resolution. We find that the filament is composed of two alternating archaellins - ArlB1 and ArlB2, suggesting that the architecture and assembly of archaella is more complex than previously thought. Moreover, we identify two major structural elements that enable the archaellum filament to move.Our findings provide new insights into archaeal motility and challenge the current view on the archaellum architecture and assembly.

Significance Many bacteria and most archaea are enveloped in S-layers, protective lattices of proteins that are among the most abundant on earth. S-layers define both the cell’s shape and periplasmic space, and play essential roles in cell division, adhesion, biofilm formation, protection against harsh environments and phages, and comprise important virulence factors in pathogenic bacteria. Despite their importance, structural information about archaeal S-layers is sparse. Here, we describe in situ structural data on archaeal S-layers by cutting-edge electron cryotomography. Our results shed light on the function and evolution of archaeal cell walls and thus our understanding of microbial life. They will also inform approaches in nanobiotechnology aiming to engineer S-layers for a vast array of applications., Surface protein layers (S-layers) often form the only structural component of the archaeal cell wall and are therefore important for cell survival. S-layers have a plethora of cellular functions including maintenance of cell shape, osmotic, and mechanical stability, the formation of a semipermeable protective barrier around the cell, and cell–cell interaction, as well as surface adhesion. Despite the central importance of S-layers for archaeal life, their 3-dimensional (3D) architecture is still poorly understood. Here we present detailed 3D electron cryomicroscopy maps of archaeal S-layers from 3 different Sulfolobus strains. We were able to pinpoint the positions and determine the structure of the 2 subunits SlaA and SlaB. We also present a model describing the assembly of the mature S-layer.

The Ff family of filamentous bacteriophages infect gram-negative bacteria, but do not cause lysis of their host cell. Instead, new virions are extruded via the phage-encoded pIV protein, which has homology with bacterial secretins. Here, we determine the structure of pIV from the f1 filamentous bacteriophage at 2.7 Å resolution by cryo-electron microscopy, the first near-atomic structure of a phage secretin. Fifteen f1 pIV subunits assemble to form a gated channel in the bacterial outer membrane, with associated soluble domains projecting into the periplasm. We model channel opening and propose a mechanism for phage egress. By single-cell microfluidics experiments, we demonstrate the potential for secretins such as pIV to be used as adjuvants to increase the uptake and efficacy of antibiotics in bacteria. Finally, we compare the f1 pIV structure to its homologues to reveal similarities and differences between phage and bacterial secretins., New virions of Ff bacteriophages are extruded from the host cell via the channel built from phage protein pIV, homologous to bacterial secretins. Here, the authors report the structure of this channel from the f1 filamentous bacteriophage and propose its use as an adjuvant to increase the uptake and efficacy of antibiotics.

Herein a robust and active combustion catalyst was prepared with three-quarter (75 wt.%) of its composition derived from the aluminium foil waste and designated as 5Pd-ACFL. The prepared catalyst was characterised using X-ray diffraction (XRD), Temperature-programmed reduction (TPR), Bright-field transmission electron microscopy (BF-TEM), High angle annular dark field (HAADF), Fourier transform infrared-pyridine (FTIR-Pyridine) and X-ray Photoelectron Spectroscopy (XPS) techniques and compared to the commercial equivalent (5Pd-AC550). The catalyst 5Pd-ACFL550 showed higher catalytic activity than that of 5Pd-AC550 in the total methane oxidation reaction with T50% at 303 ºC at Gas hourly space velocity (GHSV) of 100,000 mL g-1 h-1. Our approach opens doors for the preparation of robust cheap combustion catalyst from aluminium foil waste and demonstrates its application in the catalytic converters of natural gas vehicles (NGV-vehicles) and other combustion applications. As a result, this can be opened up to a wider variety of application markets, including residential and automotive applications.

Herein, an in situ DRIFT technique was used to study the reaction mechanism of methanol dehydration to dimethyl ether (DME). Moreover, the effect of silver loading on the catalytic performance of η-Al2O3 was examined in a fixed bed reactor under the reaction conditions where the temperature ranged from 180 to 300 °C with a WHSV = 48.4 h–1. It was observed that the optimum Ag loading was found to be 10% Ag/η-Al2O3 with this novel catalyst also showing a high degree of stability under steady-state conditions, and this is attributed to the enhancement in both the surface Lewis acidity and the hydrophobicity.

Reduction of threading dislocation density in top-down fabricated GaN nanocolumns (NCs) via their successive lateral shrinkage by anisotropic wet etch and lateral overgrowth by metalorganic chemical vapor deposition is studied by transmission electron microscopy. The fabrication process involves a combination of dry and wet etches to produce NC arrays of a low fill factor (

Surface protein layers (S-layers) often form the only structural component of the archaeal cell wall and are therefore important for cell survival. S-layers have a plethora of cellular functions including maintenance of cell shape, osmotic and mechanical stability, the formation of a semi-permeable protective barrier around the cell, cell-cell interaction, as well as surface adhesion. Despite the central importance of the S-layer for archaeal life, their three-dimensional architecture is still poorly understood. Here we present the first detailed 3D electron cryo-microscopy maps of archaeal S-layers from three different Sulfolobus strains. We were able to pinpoint the positions and determine the structure of the two subunits SlaA and SlaB. We also present a model describing the assembly of the mature S-layer.

A comprehensive description of a procedure to form dense locally ordered 2D arrays of vertically aligned hexagonal in section GaN nanocolumns (NCs) without height deviations will be presented. Particular focus will be given for the preparation of silica nanosphere hard masks, dry etching to form GaN NCs, wet etching to modify NC shape, thermal annealing and regrowth to recover non-polar m-plane facets, improve NC crystal quality and array fill factor.

Design considerations for vertical Gallium Nitride (GaN) nanowire Schottky barrier diodes (NWSBDs) for high voltage applications is discussed in this paper. Preliminary quasi-vertical NWSBDs fabricated on a Sapphire substrate show rectifying properties with breakdown voltage of 100 V. The principle of dielectric Reduced SURface Field (RESURF) which is naturally compatible with the NW structure, is utilized to block high voltages (> 600 V) within the fabrication constraints of nano-pillar height and drift doping concentration. Design considerations for the NWSBD is explored through 3D TCAD simulations. TCAD simulations show the NWSBDs can block voltages upward of 700 V with very low on-resistance with optimal design. The measured and simulated results are compared with state of the art GaN devices to provide an understanding of the true potential of the GaN NW architecture as power devices offering high breakdown voltages and low on-state resistance and a reliable device operation, all on a vertical architecture and a non-native substrate.

A new concept of vertical gallium nitride (GaN) Schottky barrier diode based on nanowire (NW) structures and the principle of dielectric REduced SURface Field (RESURF) is proposed in this paper. High-threading dislocation density in GaN epitaxy grown on foreign substrates has hindered the development and commercialization of vertical GaN power devices. The proposed NW structure, previously explored for LEDs offers an opportunity to reduce defect density and fabricate low cost vertical GaN power devices on silicon (Si) substrates. In this paper, we investigate the static characteristics of high-voltage GaN NW Schottky diodes using 3-D TCAD device simulation. The NW architecture theoretically achieves blocking voltages upward of 700 V with very low specific on-resistance. Two different methods of device fabrication are discussed. Preliminary experimental results are reported on device samples fabricated using one of the proposed methods. The fabricated Schottky diodes exhibit a breakdown voltage of around 100 V and no signs of current collapse. Although more work is needed to further explore the nano-GaN concept, the preliminary results indicate that superior tradeoff between the breakdown voltage and specific on-resistance can be achieved, all on a vertical architecture and a foreign substrate. The proposed NW approach has the potential to deliver low cost reliable GaN power devices, circumventing the limitations of today's high electron mobility transistors (HEMTs) technology and vertical GaN on GaN devices.

We have investigated single electron spin transport in individual single crystal bcc Co30Fe70 nanoparticles using scanning tunnelling microscopy with a standard tungsten tip. Particles were deposited using a gas-aggregation nanoparticle source and individually addressed as asymmetric double tunnel junctions with both a vacuum and a MgO tunnel barrier. Spectroscopy measurements on the particles show a Coulomb staircase that is correlated with the measured particle size. Field emission tunnelling effects are incorporated into standard single electron theory to model the data. This formalism allows spin-dependent parameters to be determined even though the tip is not spin-polarised. The barrier spin polarisation is very high, in excess of 84%. By variation of the resistance, several orders of magnitude of the system timescale are probed, enabling us to determine the spin relaxation time on the island. It is found to be close to 10 μs, a value much longer than previously reported.

Chemically ordered B2 FeRh exhibits a remarkable antiferromagnetic-ferromagnetic phase transition that is first order. It thus shows phase coexistence, usually by proceeding though nucleation at random defect sites followed by propagation of phase boundary domain walls. The transition occurs at a temperature that can be varied by doping other metals onto the Rh site. We have taken advantage of this to yield control over the transition process by preparing an epilayer with oppositely directed doping gradients of Pd and Ir throughout its height, yielding a gradual transition that occurs between 350 K and 500 K. As the sample is heated, a horizontal antiferromagnetic-ferromagnetic phase boundary domain wall moves gradually up through the layer, its position controlled by the temperature. This mobile magnetic domain wall affects the magnetisation and resistivity of the layer in a way that can be controlled, and hence exploited, for novel device applications.

A Nanostructured GaN Device Architecture for Power Applications Z. John Shen, Gourab Sabui, Vitaly Z. Zubialevich, Mary White, Pietro Pampili, Peter J. Parbrook, Mathew McLaren, Miryam Arredondo-Arechavala Gallium nitride (GaN) has emerged as a promising material for development of power semiconductor devices owing to its high critical electric field, large bandgap and superior transport properties. The unique properties of GaN have prompted realization of power devices both in a lateral (high electron mobility transistors (HEMTs)) and a vertical layout (bulk GaN on GaN devices). GaN power devices show extremely low conduction and switching losses and holds the key to extremely low-loss and high-efficiency power converters of the future. However, GaN power devices have been plagued with several inherent drawbacks preventing a ubiquitous adoption of GaN as the material of choice for power switches. The most critical trade-off has been the choice of substrate for the growth of GaN epitaxy: a high performance, high-cost native substrate against a low-cost, non-native substrate with associated reliability issues. For GaN to thrive as a superior successor to Si, a low cost, high performance epitaxy with improved reliability is expected moving forward. Current lateral HEMTs and vertical GaN on GaN devices are inadequate to address this trade-off. A novel nanostructured approach to GaN power devices is proposed in this paper. The unique property of GaN nanowires is its ability to elastically relax in the lateral direction, and accommodate lattice mismatch with non-native substrate through pseudomorphic growth without dislocation formation as compared to thin-film heterostructures. Experimental studies have shown self-induced GaN NWs grown with a high surface to volume ratio on a Si substrate have a non-polar side face and is virtually free of threading dislocations and other structural defects. Power devices grown on a nano-GaN epitaxy theoretically have the potential to bypass the reliability concerns associated with a non-native substrate but still deliver comparable or even superior performance, albeit at a low-cost. Schottky barrier diodes are designed and fabricated based on the nano-GaN concept. Fabricated diodes grown on a Sapphire substrate show distinct rectifying properties blocking voltages of 100 V. Despite repetitive biasing, the devices did not show any sign of current collapse. Design optimization of the nanowire Schottky barrier diode (NWSBD) is performed using 3D TCAD drift-diffusion simulations and semiconductor-oxide interaction was utilized to push the performance of the NWSBDs beyond the unipolar limit of GaN. The optimized NWSBD show the potential to block voltages upwards of 650 V working under present fabrication constraints of doping concentrations and pillar height. Simulated characteristics predict superior VRB 2/RON FoM, outperforming both the lateral HEMTs and the vertical GaN on GaN devices. A fully controlled, three terminal nanowire field effect transistor (NWFET) is also investigated using 3D TCAD drift-diffusion modeling. The NWFET can be operated in both normally-off and normally-on modes based on design and requirements. The 3D gate around the nanowires coupled with a strong dielectric REduced SURface Field (RESURF) effect allows this architecture to block voltages beyond the 1D unipolar material limit of GaN in the reverse bias. With proper design, highly desirable linear voltage to pillar height scaling can be achieved for the NWFET. Breakdown voltages of more than 900 V is predicted, with superior VRB 2/RON and QGD x RDS(ON) figure of merits. Despite lacking a body-diode, the NWFETs being quasi-symmetrical enables current conduction in the 3rd quadrant itself by self-commutated reverse conduction with a very low voltage drop. The nanowire architecture holds great potential to produce power rectifiers and controlled FETs with high performance, improved reliability and ruggedness and in a cost-effective way.

We report on the temperature dependence of the recently discovered spin Hall magnetoresistance in a yttrium iron garnet (YIG)/platinum (Pt) thin film. The YIG/Pt layers are an ideal choice as the combination of an insulating magnetic material and the high spin-orbit interaction in Pt gives a relatively large magnetoresistance and no electrical conduction occurs in the YIG. The temperature dependence of the magnetoresistance was measured between 1.4 K and 280 K from which the temperature dependence of the spin diffusion length in Pt has been extracted. We found that the best agreement between our data and the recently published [Chen, Phys. Rev. B 87, 144411 (2013)PRBMDO1098-012110.1103/ PhysRevB.87.144411] theory of the spin Hall magnetoresistance is given by an assumed Elliot-Yafet mechanism of spin relaxation with temperature-independent spin Hall angle and spin mixing conductance. The best estimate for the spin diffusion length returns values between 0.57 and 3.85 nm.

Synchrotron X-ray diffraction was used to study the phase transformation processes during the magnetostructural transition in a B2-ordered FeRh (001)-oriented epilayer grown on MgO by sputtering. Out-of-plane lattice constant measurements within the hysteretic regime of the transition reveal a microstructure consistent with the coexistence of lattice-expanded and contracted phases in spatially distinct regions. It was found that the phase separation is more pronounced during cooling than heating. Furthermore, whilst lattice-expanded domains that span the height of the film can be undercooled by several kelvins, there is no equivalent superheating. This asymmetry between the cooling and heating processes in FeRh is consistent with the difference in the kinetics of generic freezing and melting transitions.

Chemically ordered alloys are useful in a variety of magnetic nanotechnologies. They are most conveniently prepared at an industrial scale using sputtering techniques. Here we describe a method for preparing epitaxial thin films of B2-ordered FeRh by sputter deposition onto single crystal MgO substrates. Deposition at a slow rate onto a heated substrate allows time for the adatoms to both settle into a lattice with a well-defined epitaxial relationship with the substrate and also to find their proper places in the Fe and Rh sublattices of the B2 structure. The structure is conveniently characterized with X-ray reflectometry and diffraction and can be visualised directly using transmission electron micrograph cross-sections. B2-ordered FeRh exhibits an unusual metamagnetic phase transition: the ground state is antiferromagnetic but the alloy transforms into a ferromagnet on heating with a typical transition temperature of about 380 K. This is accompanied by a 1% volume expansion of the unit cell: isotropic in bulk, but laterally clamped in an epilayer. The presence of the antiferromagnetic ground state and the associated first order phase transition is very sensitive to the correct equiatomic stoichiometry and proper B2 ordering, and so is a convenient means to demonstrate the quality of the layers that can be deposited with this approach. We also give some examples of the various techniques by which the change in phase can be detected.

Iron-rhodium (FeRh) nanoislands of equiatomic composition have been analysed using scanning transmission electron microscopy (STEM) electron energy loss spec-troscopy(EELS) and high angle annular dark field (HAADF) techniques. Previous magne-tometry results have lead to a hypothesis that at room temperature the core of the islands are antiferromagnetic while the shell has a small ferromagnetic signal. The causes of this effect are most likely to be a difference in composition at the edges or a strain on the island that stretches the lattice and forces the ferromagnetic transition. The results find, at the film-substrate interface, an iron-rich layer ~ 5 A thick that could play a key role in affecting the magnetostructural transition around the interfacial region and account for the room temperature ferromagnetism.

The lattice structure of roughly equiatomic iron-rhodium epilayers was studied using transmission electron microscopy. Thin films were grown on magnesium oxide substrates using molecular beam epitaxy with thicknesses of 50 nm and capped with a 2-3 nm thick MgO or Al cap. The samples were prepared into cross-sections for characterisation by TEM. Observation of the interfaces FeRh makes with the cap and the substrate are of interest, due to the potential for strain and interfacial diffusion, which will affect the magnetic properties. TEM imaging combined with X-ray photoelectron spectroscopy depth profiling data give an insight into how strain and diffusion at the interface can affect the magnetic transition.