Search

Methanogens are a diverse group of Archaea that obligately couple energy conservation to the production of methane. Some methanogens encode alternate pathways for energy conservation, like anaerobic respiration, but the biochemical details of this process are unknown. We show that a multiheme c-type cytochrome called MmcA from Methanosarcina acetivorans is important for intracellular electron transport during methanogenesis and can also reduce extracellular electron acceptors like soluble Fe3+ and anthraquinone-2,6-disulfonate. Consistent with these observations, MmcA displays reversible redox features ranging from -100 to -450 mV versus SHE. Additionally, mutants lacking mmcA have significantly slower Fe3+ reduction rates. The mmcA locus is prevalent in members of the Order Methanosarcinales and is a part of a distinct clade of multiheme cytochromes that are closely related to octaheme tetrathionate reductases. Taken together, MmcA might act as an electron conduit that can potentially support a variety of energy conservation strategies that extend beyond methanogenesis.

Electromagnetic waves propagation through the ionosphere is subject to several effects including refraction, absorption, signal delay, or Faraday rotation. A ray tracer propagator that simulates these effects is an important tool for all satellite missions relying on trans-ionospheric communications and Earth observation. This study presents an update to the 1975 Jones & Stephenson IONORT's code by implementing the use of up-to-date ionospheric, atmospheric, and geomagnetic models (IRI or NeQuick, NRLMSISE-00, IGRF), and a new 3-D model for equatorial plasma bubbles (EPBs). The developed code is part of the Ionosphere Modular Software Package (IMSP) in the context of the European Space Agency (ESA) project SIMIONO. HF radar sounders, Synthetic Aperture Radars (SAR), and GNSS Reflectometry (GNSS-R) missions constitute the main application of this software. The ray tracer has been validated with respect to the original software and by comparing real vs. simulated vertical ionograms in different locations and dates., This work was supported in part by the grant GENESIS PID2021-126436OB-C21 from the Programa Estatal para Impulsar la Investigación Científico-Técnica y su Transferencia, del Plan Estatal de Investigación Científica, Técnica y de Innovación 2021-2023 (Spain) and in part by the European Social Fund (ESF), Grant RYC-2016-2018 financed by MCIN/AEI /10.13039/501100011033., Peer Reviewed, Postprint (published version)

The structure and mechanism of the water-oxidation chemistry that occurs in photosystem II have been subjects of great interest. The advent of X-ray free electron lasers allowed the determination of structures of the stable intermediate states and of steps in the transitions between these intermediate states, bringing a new perspective to this field. The room-temperature structures collected as the photosynthetic water oxidation reaction proceeds in real time have provided important novel insights into the structural changes and the mechanism of the water oxidation reaction. The time-resolved measurements have also given us a view of how this reaction-which involves multielectron, multiproton processes-is facilitated by the interaction of the ligands and the protein residues in the oxygen-evolving complex. These structures have also provided a picture of the dynamics occurring in the channels within photosystem II that are involved in the transport of the substrate water to the catalytic center and protons to the bulk.

The EQTC 2023 held from October 16th to October 20th, 2023, in Hannover, was a week of conference and exhibition. The conference featured over 40 exhibitors, more than two-dozen plenary presentations and panel discussions, over 140 speakers and 180 poster presentations on the successes and challenges for the EU’s quantum sector. With approximately 700 guests, the European quantum community made the European Quantum Technologies Conference (EQTC) Europe’s quantum event of the year. The EQTC 2023 brought together a diverse community of brilliant scientists, innovative engineers, visionary leaders, and enthusiastic students, all united by their passion for quantum technologies and science.

This paper presents the electron and photon energy calibration obtained with the ATLAS detector using 140 fb−1 of LHC proton-proton collision data recorded at √s = 13 TeV between 2015 and 2018. Methods for the measurement of electron and photon energies are outlined, along with the current knowledge of the passive material in front of the ATLAS electromagnetic calorimeter. The energy calibration steps are discussed in detail, with emphasis on the improvements introduced in this paper. The absolute energy scale is set using a large sample of Z-boson decays into electron-positron pairs, and its residual dependence on the electron energy is used for the first time to further constrain systematic uncertainties. The achieved calibration uncertainties are typically 0.05% for electrons from resonant Z-boson decays, 0.4% at ET ∼ 10 GeV, and 0.3% at ET ∼ 1 TeV; for photons at ET ∼ 60 GeV, they are 0.2% on average. This is more than twice as precise as the previous calibration. The new energy calibration is validated using J/ → ee and radiative Z-boson decays. © 2024 Institute of Physics. All rights reserved.

This paper presents the electron and photon energy calibration obtained with the ATLAS detector using 140 fb−1 of LHC proton-proton collision data recorded at √s = 13 TeV between 2015 and 2018. Methods for the measurement of electron and photon energies are outlined, along with the current knowledge of the passive material in front of the ATLAS electromagnetic calorimeter. The energy calibration steps are discussed in detail, with emphasis on the improvements introduced in this paper. The absolute energy scale is set using a large sample of Z-boson decays into electron-positron pairs, and its residual dependence on the electron energy is used for the first time to further constrain systematic uncertainties. The achieved calibration uncertainties are typically 0.05% for electrons from resonant Z-boson decays, 0.4% at ET ∼ 10 GeV, and 0.3% at ET ∼ 1 TeV; for photons at ET ∼ 60 GeV, they are 0.2% on average. This is more than twice as precise as the previous calibration. The new energy calibration is validated using J/ → ee and radiative Z-boson decays. © 2024 Institute of Physics. All rights reserved.

Macromolecular crystallography generally requires the recovery of missing phase information from diffraction data to reconstruct an electron-density map of the crystallized molecule. Most recent structures have been solved using molecular replacement as a phasing method, requiring an a priori structure that is closely related to the target protein to serve as a search model; when no such search model exists, molecular replacement is not possible. New advances in computational machine-learning methods, however, have resulted in major advances in protein structure predictions from sequence information. Methods that generate predicted structural models of sufficient accuracy provide a powerful approach to molecular replacement. Taking advantage of these advances, AlphaFold predictions were applied to enable structure determination of a bacterial protein of unknown function (UniProtKB Q63NT7, NCBI locus BPSS0212) based on diffraction data that had evaded phasing attempts using MIR and anomalous scattering methods. Using both X-ray and micro-electron (microED) diffraction data, it was possible to solve the structure of the main fragment of the protein using a predicted model of that domain as a starting point. The use of predicted structural models importantly expands the promise of electron diffraction, where structure determination relies critically on molecular replacement.

We report the development of deep-learning coherent electron diffractive imaging at subangstrom resolution using convolutional neural networks (CNNs) trained with only simulated data. We experimentally demonstrate this method by applying the trained CNNs to recover the phase images from electron diffraction patterns of twisted hexagonal boron nitride, monolayer graphene, and a gold nanoparticle with comparable quality to those reconstructed by a conventional ptychographic algorithm. Fourier ring correlation between the CNN and ptychographic images indicates the achievement of a resolution in the range of 0.70 and 0.55 Å. We further develop CNNs to recover the probe function from the experimental data. The ability to replace iterative algorithms with CNNs and perform real-time atomic imaging from coherent diffraction patterns is expected to find applications in the physical and biological sciences.

In this study, we present a complete set of electron scattering cross-sections from 1-Methyl-5-Nitroimidazole (1M5NI) molecules for impact energies ranging from 0.1 to 1000 eV. This information is relevant to evaluate the potential role of 1M5NI as a molecular radiosensitizers. The total electron scattering cross-sections (TCS) that we previously measured with a magnetically confined electron transmission apparatus were considered as the reference values for the present analysis. Elastic scattering cross-sections were calculated by means of two different schemes: The Schwinger multichannel (SMC) method for the lower energies (below 15 eV) and the independent atom model-based screening-corrected additivity rule with interferences (IAM-SCARI) for higher energies (above 15 eV). The latter was also applied to calculate the total ionization cross-sections, which were complemented with experimental values of the induced cationic fragmentation by electron impact. Double differential ionization cross-sections were measured with a reaction microscope multi-particle coincidence spectrometer. Using a momentum imaging spectrometer, direct measurements of the anion fragment yields and kinetic energies by the dissociative electron attachment are also presented. Cross-sections for the other inelastic channels were derived with a self-consistent procedure by sampling their values at a given energy to ensure that the sum of the cross-sections of all the scattering processes available at that energy coincides with the corresponding TCS. This cross-section data set is ready to be used for modelling electron-induced radiation damage at the molecular level to biologically relevant media containing 1M5NI as a potential radiosensitizer. Nonetheless, a proper evaluation of its radiosensitizing effects would require further radiobiological experiments.

Mealworms are one of the most economically important insects in large-scale production for human and animal nutrition. Densoviruses are highly pathogenic for invertebrates and exhibit an extraordinary level of diversity which rivals that of their hosts. Molecular, clinical, histological, and electron microscopic characterization of novel densovirus infections is of utmost economic and ecological importance. Here, we describe an outbreak of densovirus with high mortality in a commercial mealworm (Tenebrio molitor) farm. Clinical signs included inability to prehend food, asymmetric locomotion evolving to nonambulation, dehydration, dark discoloration, and death. Upon gross examination, infected mealworms displayed underdevelopment, dark discoloration, larvae body curvature, and organ/tissue softness. Histologically, there was massive epithelial cell death, and cytomegaly and karyomegaly with intranuclear inclusion (InI) bodies in the epidermis, pharynx, esophagus, rectum, tracheae, and tracheoles. Ultrastructurally, these InIs represented a densovirus replication and assembly complex composed of virus particles ranging from 23.79 to 26.99 nm in diameter, as detected on transmission electron microscopy. Whole-genome sequencing identified a 5579-nucleotide-long densovirus containing 5 open reading frames. A phylogenetic analysis of the mealworm densovirus showed it to be closely related to several bird- and bat-associated densoviruses, sharing 97% to 98% identity. Meanwhile, the nucleotide similarity to a mosquito, cockroach, and cricket densovirus was 55%, 52%, and 41%, respectively. As this is the first described whole-genome characterization of a mealworm densovirus, we propose the name Tenebrio molitor densovirus (TmDNV). In contrast to polytropic densoviruses, this TmDNV is epitheliotropic, primarily affecting cuticle-producing cells.

The cryo-electron microscopy (cryo-EM) method microcrystal electron diffraction (MicroED) was initially described in 2013 and has recently gained attention as an emerging technique for research in drug discovery. As compared to other methods in structural biology, MicroED provides many advantages deriving from the use of nanocrystalline material for the investigations. Here, we review the recent advancements in the field of MicroED and show important examples of small molecule, peptide and protein structures that has contributed to the current development of this method as an important tool for drug discovery.

Crystallizing G protein-coupled receptors (GPCRs) in lipidic cubic phase (LCP) often yields crystals suited for the cryogenic electron microscopy (cryoEM) method microcrystal electron diffraction (MicroED). However, sample preparation is challenging. Embedded crystals cannot be targeted topologically. Here, we use an integrated fluorescence light microscope (iFLM) inside of a focused ion beam and scanning electron microscope (FIB-SEM) to identify fluorescently labeled GPCR crystals. Crystals are targeted using the iFLM and LCP is milled using a plasma focused ion beam (pFIB). The optimal ion source for preparing biological lamellae is identified using standard crystals of proteinase K. Lamellae prepared using either argon or xenon produced the highest quality data and structures. MicroED data are collected from the milled lamellae and the structures are determined. This study outlines a robust approach to identify and mill membrane protein crystals for MicroED and demonstrates plasma ion-beam milling is a powerful tool for preparing biological lamellae.

In recent years, correlated insulating states, unconventional superconductivity, and topologically non-trivial phases have all been observed in several moiré heterostructures. However, understanding of the physical mechanisms behind these phenomena is hampered by the lack of local electronic structure data. Here, we use scanning tunnelling microscopy and spectroscopy to demonstrate how the interplay between correlation, topology, and local atomic structure determines the behaviour of electron-doped twisted monolayer-bilayer graphene. Through gate- and magnetic field-dependent measurements, we observe local spectroscopic signatures indicating a quantum anomalous Hall insulating state with a total Chern number of ±2 at a doping level of three electrons per moiré unit cell. We show that the sign of the Chern number and associated magnetism can be electrostatically switched only over a limited range of twist angle and sample hetero-strain values. This results from a competition between the orbital magnetization of filled bulk bands and chiral edge states, which is sensitive to strain-induced distortions in the moiré superlattice.

NendoU from SARS-CoV-2 is responsible for the virus's ability to evade the innate immune system by cleaving the polyuridine leader sequence of antisense viral RNA. Here we report the room-temperature structure of NendoU, solved by serial femtosecond crystallography at an X-ray free-electron laser to 2.6 Å resolution. The room-temperature structure provides insight into the flexibility, dynamics, and other intrinsic properties of NendoU, with indications that the enzyme functions as an allosteric switch. Functional studies examining cleavage specificity in solution and in crystals support the uridine-purine cleavage preference, and we demonstrate that enzyme activity is fully maintained in crystal form. Optimizing the purification of NendoU and identifying suitable crystallization conditions set the benchmark for future time-resolved serial femtosecond crystallography studies. This could advance the design of antivirals with higher efficacy in treating coronaviral infections, since drugs that block allosteric conformational changes are less prone to drug resistance.

FLASH radiation therapy (FLASH-RT), delivered with ultrahigh dose rate (UHDR), may allow patients to be treated with less normal tissue toxicity for a given tumor dose compared with currently used conventional dose rate. Clinical trials are being carried out and are needed to test whether this improved therapeutic ratio can be achieved clinically. During the clinical trials, quality assurance and credentialing of equipment and participating sites, particularly pertaining to UHDR-specific aspects, will be crucial for the validity of the outcomes of such trials. This report represents an initial framework proposed by the NRG Oncology Center for Innovation in Radiation Oncology FLASH working group on quality assurance of potential UHDR clinical trials and reviews current technology gaps to overcome. An important but separate consideration is the appropriate design of trials to most effectively answer clinical and scientific questions about FLASH. This paper begins with an overview of UHDR RT delivery methods. UHDR beam delivery parameters are then covered, with a focus on electron and proton modalities. The definition and control of safe UHDR beam delivery and current and needed dosimetry technologies are reviewed and discussed. System and site credentialing for large, multi-institution trials are reviewed. Quality assurance is then discussed, and new requirements are presented for treatment system standard analysis, patient positioning, and treatment planning. The tables and figures in this paper are meant to serve as reference points as we move toward FLASH-RT clinical trial performance. Some major questions regarding FLASH-RT are discussed, and next steps in this field are proposed. FLASH-RT has potential but is associated with significant risks and complexities. We need to redefine optimization to focus not only on the dose but also on the dose rate in a manner that is robust and understandable and that can be prescribed, validated, and confirmed in real time. Robu

We use the Magnetospheric Multiscale mission to observe a bi-directional electron acceleration event in the electron foreshock upstream of Earth's quasi-perpendicular collisionless bow shock. The acceleration region is associated with a decrease in wave activity, inconsistent with common electron acceleration mechanisms such as Diffusive Shock Acceleration and Stochastic Shock Drift Acceleration. We propose a two-step acceleration process where an electron field-aligned beam acts as a seed population further accelerated by a shrinking magnetic bottle process, with the shock acting as the magnetic mirror(s)., QC 20230824

Electron/hole transfer mechanisms in DNA and polynucleotide structures continue to garner considerable interest as emerging charge-transport systems and molecular electronics. To shed mechanistic insight into these electronic properties, we carried out large-scale density functional theory (DFT) calculations (up to 650 atoms) to systematically analyze the structural and electron/hole transport properties of fully periodic single- and double-stranded DNA. We examined the performance of various exchange-correlation functionals (LDA, BLYP, B3LYP, and B3LYP-D) and found that single-stranded thymine (T) and cytosine (C) are predominantly hole conductors, whereas single-stranded adenine (A) and guanine (G) are better electron conductors. For double-stranded DNA structures, the periodic A-T and G-C electronic band structures undergo a significant renormalization, which causes hole transport to only occur on the A and G nucleobases. Our calculations (1) provide new benchmarks for periodic nucleobase structures using dispersion-corrected hybrid functionals with large basis sets and (2) highlight the importance of dispersion effects for obtaining accurate geometries and electron/hole mobilities in these extended systems.

© 2011 Elsevier Science BV . This work has been supported by the Spanish Ministerio de Ciencia e Innovacion (FPA2009-07772 and CONSOLIDER CPAN CSD2007-42) and "Comunidad de Madrid" (Ref.: 910600). Monasor acknowledges the "Consejeria de Educacion y Ciencia de Castilla-La Mancha" and the "Fondo Social Europeo" for a postdoctoral fellowship. Very fruitful discussion with our colleagues of the Auger collaboration are acknowledged, in particular with B. Keilhauer, J. Matthews, V.H. Ponce and M. Unger., An accurate knowledge of the fluorescence yield and its dependence on atmospheric properties such as pressure, temperature or humidity is essential to obtain a reliable measurement of the primary energy of cosmic rays in experiments using the fluorescence technique. In this work, several sets of fluorescence yield data (i.e. absolute value and quenching parameters) are described and compared. A simple procedure to study the effect of the assumed fluorescence yield on the reconstructed shower parameters (energy and shower maximum depth) as a function of the primary features has been developed. As an application, the effect of water vapor and temperature dependence of the collisional cross section on the fluorescence yield and its impact on the reconstruction of primary energy and shower maximum depth has been studied. Published by Elsevier B.V., Ministerio de Ciencia e Innovacion (MICINN), Comunidad de Madrid, Consejeria de Educacion y Ciencia de Castilla-La Mancha, Fondo Social Europeo, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2015 American Physical Society, Broadband ultrashort terahertz (THz) pulses can be produced using plasma generation in a noble gas ionized by femtosecond two-color pulses. Here we demonstrate that, by using multiple-frequency laser pulses, one can obtain a waveform which optimizes the free electron trajectories in such a way that they acquire the largest drift velocity. This allows us to increase the THz conversion efficiency to 2%, an unprecedented performance for THz generation in gases. In addition to the analytical study of THz generation using a local current model, we perform comprehensive 3D simulations accounting for propagation effects which confirm this prediction. Our results show that THz conversion via tunnel ionization can be greatly improved with well-designed multicolor pulses., DFG, Sección Deptal. de Óptica (Óptica), Fac. de Óptica y Optometría, TRUE, pub

© 2010 Elsevier B.V. Autoría conjunta: Pierre Auger Collaboration. Artículo firmado por más de 10 autores. The successful installation and commissioning of the Pierre Auger Observatory would not have been possible without the strong commitment and effort from the technical and administrative staff in Malargüe. We are very grateful to the following agencies and organizations for financial support: Comisión Nacional de Energía Atómica, Fundación Antorchas, Gobierno De La Provincia de Mendoza, Municipalidad de Malargüe, NDM Holdings and Valle Las Leñas, in gratitude for their continuing cooperation over land access, Argentina; the Australian Research Council; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Financiadora de Estudos e Projetos (FINEP), Fundação de Amparo à Pesquisa do Estado de Rio de Janeiro (FAPERJ), Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Ministério de Ciência e Tecnologia (MCT), Brazil; AVCR AV0Z10100502 and AV0Z10100522, GAAV KJB300100801 and KJB100100904, MSMT-CR LA08016, LC527, 1M06002, and MSM0021620859, Czech Republic; Centre de Calcul IN2P3/CNRS, Centre National de la Recherche Scientifique (CNRS), Conseil Régional Ile-de-France, Département Physique Nucléaire et Corpusculaire (PNC-IN2P3/CNRS), Département Sciences de l’Univers (SDU-INSU/CNRS), France; Bundesministerium für Bildung und Forschung (BMBF), Deutsche Forschungsgemeinschaft (DFG), Finanzministerium Baden-Württemberg, HelmholtzGemeinschaft Deutscher Forschungszentren (HGF), Ministerium für Wissenschaft und Forschung, Nordrhein-Westfalen, Ministerium für Wissenschaft, Forschung und Kunst, Baden-Württemberg, Germany; Istituto Nazionale di Fisica Nucleare (INFN), Ministero dell’Istruzione, dell’Università e della Ricerca (MIUR), Italy; Consejo Nacional de Ciencia y Tecnología (CONACYT), Mexico; Ministerie van Onderwijs, Cultuur en Wetenschap, Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO), Stichting voor Fundamenteel Onderzoek de, We report a measurement of the flux of cosmic rays with unprecedented precision and Statistics using the Pierre Auger Observatory Based on fluorescence observations in coincidence with at least one Surface detector we derive a spectrum for energies above 10(18) eV We also update the previously published energy spectrum obtained with the surface detector array The two spectra are combined addressing the systematic uncertainties and, in particular. the influence of the energy resolution on the spectral shape The spectrum can be described by a broken power law E-gamma with index gamma = 3 3 below the ankle which is measured at log(10)(E-ankle/eV) = 18 6 Above the ankle the spectrum is described by a power law with index 2 6 followed by a flux suppression, above about log(10)(E/eV) = 19 5, detected with high statistical significance (C) 2010 Elsevier B V All rights reserved, Unión Europea. FP7, Czech Science Foundation, Czech Republic, Centre de Calcul IN2P3/CNRS, France, Centre National de la Recherche Scientifique (CNRS), France, Conseil Regional Ile-de-France, France, Departement Physique Nucleaire et Corpusculaire, France, Departement Sciences de l'Univers (SDU-INSU/CNRS), Institut Lagrange de Paris (ILP), France, Bundesministerium fur Bildung und Forschung (BMBF), Germany, Deutsche Forschungsgemeinschaft (DFG), Germany, Finanzministerium Baden-Wurttemberg, Germany, Helmholtz Alliance for Astroparticle Physics (HAP), Germany, Helmholtz-Gemeinschaft Deutscher Forschungszentren (HGF), Germany, Ministerium fur Wissenschaft und Forschung, Germany Nordrhein Westfalen, Germany, Ministerium fur Wissenschaft Forschung und Kunst Baden-Wurttemberg, Germany, Istituto Nazionale di Fisica Nucleare (INFN), Italy, Ministero dell'Istruzione, dell'Universita e della Ricerca (MIUR), Italy, Gran Sasso Center for Astroparticle Physics (CFA), Italy, CETEMPS Center of Excellence, Ministero degli Affari Esteri (MAE), Italy, Ministerie van Onderwijs, Cultuur en Wetenschap, Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO), Stichting voor Fundamenteel Onderzoek der Materie (FOM), Netherlands, National Centre for Research and Development, Poland, National Science Centre, Poland, Portuguese national funds, Portugal, FEDER funds within Programa Operacional Factores de Competitividade through Fundacao para a Ciencia e a Tecnologia (COMPETE), Portugal, Romanian Authority for Scientific Research ANCS, Romania, CNDI-UEFISCDI partnership projects, Romania, Minister of National Education, Programme Space Technology and Advanced Research (STAR), Romania, Slovenian Research Agency, Slovenia, Comunidad de Madrid, FEDER funds, Spain, Ministerio de Educacion y Ciencia, Spain, Xunta de Galicia, Spain, UNESCO, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

©2014 Elsevier B.V. All rights reserved. This work was supported by MICINN (projects MAT2010-17180 and FIS2009-07880), JCYL (project SA226U13) and USAL (project KBBB). C.G.-S. acknowledges financial upport from Comunidad de Madrid and European Social Foundation., We study the scattering of massless Dirac particles by oscillating barriers in one dimension. Using the Floquet theory, we find the exact scattering amplitudes for time-harmonic barriers of arbitrary shape. In all cases the scattering amplitudes are found to be independent of the energy of the incoming particle and the transmission coefficient is unity. This is a manifestation of the Klein tunneling in time-harmonic potentials. Remarkably, the transmission amplitudes for arbitrary sharply-peaked potehtials also become independent of the driving frequency. Conditions for which barriers of finite width can be replaced by sharply-peaked potentials are discussed., Ministerio de Ciencia e Innovación (MICINN), JCYL, USAL, Comunidad de Madrid, European Social Foundation, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

A variety of electron transfer mechanisms link bacterial cytosolic electron pools with functionally diverse redox activities in the cell envelope and extracellular space. In Listeria monocytogenes, the ApbE-like enzyme FmnB catalyzes extracytosolic protein flavinylation, covalently linking a flavin cofactor to proteins that transfer electrons to extracellular acceptors. L. monocytogenes uses an energy-coupling factor (ECF) transporter complex that contains distinct substrate-binding, transmembrane, ATPase A, and ATPase A subunits (RibU, EcfT, EcfA, and EcfA) to import environmental flavins, but the basis of extracytosolic flavin trafficking for FmnB flavinylation remains poorly defined. In this study, we show that the EetB and FmnA proteins are related to ECF transporter substrate-binding and transmembrane subunits, respectively, and are essential for exporting flavins from the cytosol for flavinylation. Comparisons of the flavin import versus export capabilities of L. monocytogenes strains lacking different ECF transporter subunits demonstrate a strict directionality of substrate-binding subunit transport but partial functional redundancy of transmembrane and ATPase subunits. Based on these results, we propose that ECF transporter complexes with different subunit compositions execute directional flavin import/export through a broadly conserved mechanism. Finally, we present genomic context analyses that show that related ECF exporter genes are distributed across members of the phylum Firmicutes and frequently colocalize with genes encoding flavinylated extracytosolic proteins. These findings clarify the basis of ECF transporter export and extracytosolic flavin cofactor trafficking in Firmicutes. IMPORTANCE Bacteria import vitamins and other essential compounds from their surroundings but also traffic related compounds from the cytosol to the cell envelope where they serve various functions. Studying the foodborne pathogen Listeria monocytogenes, we find that the mo

The production of ethanol by the yeast Saccharomyces cerevisiae remains the process in industrial biotechnology with the largest product volume (ca. 100 million litres annually in 2022). Carbon losses occur due to the formation of biomass and glycerol, which can account for at least 8% of the product. Under anaerobic conditions, formation of yeast biomass and glycerol are coupled via redox-cofactor balances, as a net generation of NADH during biomass formation needs to be compensated by NADH-dependent formation of glycerol from sugar. This thesis discusses redox-engineering strategies for maximizing ethanol yields on substrate., BT/Industriele Microbiologie, application external

A search is presented for the Higgs boson decay to a pair of electrons (e+e−) in proton-proton collisions at √ s = 13 TeV. The data set was collected with the CMS experiment at the LHC between 2016 and 2018, corresponding to an integrated luminosity of 138 fb−1. The analysis uses event categories targeting Higgs boson production via gluon fusion and vector boson fusion. The observed upper limit on the Higgs boson branching fraction to an electron pair is 3.0 × 10−4 (3.0 × 10−4 expected) at the 95% confidence level, which is the most stringent limit on this branching fraction to date.

Although tumor growth requires the mitochondrial electron transport chain (ETC), the relative contribution of complex I (CI) and complex II (CII), the gatekeepers for initiating electron flow, remains unclear. In this work, we report that the loss of CII, but not that of CI, reduces melanoma tumor growth by increasing antigen presentation and T cell-mediated killing. This is driven by succinate-mediated transcriptional and epigenetic activation of major histocompatibility complex-antigen processing and presentation (MHC-APP) genes independent of interferon signaling. Furthermore, knockout of methylation-controlled J protein (MCJ), to promote electron entry preferentially through CI, provides proof of concept of ETC rewiring to achieve antitumor responses without side effects associated with an overall reduction in mitochondrial respiration in noncancer cells. Our results may hold therapeutic potential for tumors that have reduced MHC-APP expression, a common mechanism of cancer immunoevasion.

One-dimensional (1D) nanostructures, such as nanowires, constitute building blocks for nanoscience and nanotechnology. Their fundamental physical properties are dictated by their crystalline structures, which are often characterized by transmission electron microscopy (TEM). Theoretically, the shape of a nanostructure can affect its electron diffraction pattern; however, for 1D nanostructures, an experimental observation of this geometric effect has not been reported. Here, we demonstrate unambiguously the first experimental observation of this geometric effect in electron diffraction from nanowires of iridium dioxide (IrO2) and lead tin telluride (Pb1-xSnxTe), which are topological semimetals and topological crystalline insulators, respectively. Grown by chemical vapor deposition, the nanowires are single-crystalline and have well defined facets with nearly rectangular cross-sections. Diffraction spot splitting was observed in electron diffraction patterns when the e-beam was not perpendicular to the major facets of the nanowires. Atomic-resolution scanning TEM studies rule out other possible origins of the splitting, including twin domains and non-uniform strain. Theoretical calculations of electron diffraction capturing the nanowire geometry show good agreement with the experimental results, including the diffraction order dependence of the peak splitting. The observation of this geometric effect offers a non-destructive approach to characterizing the thickness of the one-dimensional nanostructures. © 2023 Elsevier Ltd

Purpose: The increased normal tissue tolerance for FLASH radiotherapy (FLASH-RT), as compared to conventional radiotherapy, was first observed in ultra-high dose rate electron beams. Initial clinical trials in companion animals have revealed a high risk of developing osteoradionecrosis following high-dose single-fraction electron FLASH-RT, which may be related to inhomogeneities in the dose distribution. In the current study, we aim to evaluate the possibilities of intensity-modulated electron FLASH-RT in a clinical setting to ensure a homogeneous dose distribution in future veterinary and human clinical trials. Methods: Our beam model in the treatment planning system electronRT (.decimal, LLC, Sanford, FL, USA) was based on a 10-MeV electron beam from a clinical linear accelerator used to treat veterinary patients with FLASH-RT in a clinical setting. In electronRT, the beam can be intensity-modulated using tungsten island blocks in the electron block cutout, and range-modulated using a customized bolus with variable thickness. Modulations were first validated in a heterogeneous phantom by comparing measured and calculated dose distributions. To evaluate the impact of intensity modulation in superficial single-fraction FLASH-RT, a treatment planning study was conducted, including eight canine cancer patient cases with simulated tumors in the head-and-neck region. For each case, treatment plans with and without intensity modulation were created for a uniform bolus and a range-modulating bolus. Treatment plans were evaluated using a target dose homogeneity index (HI), a conformity index (CI), the near-maximum dose outside the target ((Formula presented.)), and the near-minimum dose to the target ((Formula presented.)). Results: By adding intensity modulation to plans with a uniform bolus, the HI could be improved (p = 0.017). The combination of a range-modulating bolus and intensity modulation provided a further significant improvement of the HI as compared to usin

Purpose: The increased normal tissue tolerance for FLASH radiotherapy (FLASH-RT), as compared to conventional radiotherapy, was first observed in ultra-high dose rate electron beams. Initial clinical trials in companion animals have revealed a high risk of developing osteoradionecrosis following high-dose single-fraction electron FLASH-RT, which may be related to inhomogeneities in the dose distribution. In the current study, we aim to evaluate the possibilities of intensity-modulated electron FLASH-RT in a clinical setting to ensure a homogeneous dose distribution in future veterinary and human clinical trials. Methods: Our beam model in the treatment planning system electronRT (.decimal, LLC, Sanford, FL, USA) was based on a 10-MeV electron beam from a clinical linear accelerator used to treat veterinary patients with FLASH-RT in a clinical setting. In electronRT, the beam can be intensity-modulated using tungsten island blocks in the electron block cutout, and range-modulated using a customized bolus with variable thickness. Modulations were first validated in a heterogeneous phantom by comparing measured and calculated dose distributions. To evaluate the impact of intensity modulation in superficial single-fraction FLASH-RT, a treatment planning study was conducted, including eight canine cancer patient cases with simulated tumors in the head-and-neck region. For each case, treatment plans with and without intensity modulation were created for a uniform bolus and a range-modulating bolus. Treatment plans were evaluated using a target dose homogeneity index (HI), a conformity index (CI), the near-maximum dose outside the target ((Formula presented.)), and the near-minimum dose to the target ((Formula presented.)). Results: By adding intensity modulation to plans with a uniform bolus, the HI could be improved (p = 0.017). The combination of a range-modulating bolus and intensity modulation provided a further significant improvement of the HI as compared to usin

©2022 American Physical Society We thank Roopali Kukreja for answering our questions about Ref. [21] and Sergio O. Valenzuela and Olivier Fruchart for critical reading of the manuscript. We acknowledge M. R. Osorio and D. Granados at IMDEA-nanoscience nanofabri- cation center for their help in the lithography process. This work has been partially funded by MCIN/AEI/10.13039/501100011033 through Projects No. FIS2016-78591-C3-1- R, No. MAT2017-87072-C4-2-P, No. RTI2018-097895-B- C42, No. RTI2018-095303-B-C53, and No. PID2020 - 117024GB-C43 and by the Comunidad de Madrid through Project No. NANOMAGCOST-CM P2018/NMT-4321. IMDEA Nanociencia acknowledges support from the Severo Ochoa Programme for Centres of Excellence in R&D (Grants No. SEV-2016-0686 and No. CEX2020- 001039-S) . The work has been supported by the ALBA in- house research program. We thank the Spanish National Center of Electron Microscopy for Scanning Electron Microscopy measurements. M. W. K. acknowledges funding from Horizon 2020 Marie Sk ? odowska-Curie COFUND DOC-FAM, with Grant agreement No. 754397., The spin Hall effect and the inverse spin Hall effect are important spin-charge conversion mechanisms. The direct spin Hall effect induces a surface spin accumulation from a transverse charge current due to spin-orbit coupling even in nonmagnetic conductors. However, most detection schemes involve additional interfaces, leading to large scattering in reported data. Here we perform interface-free x-ray spectroscopy measurements at the Cu L_(3;2) absorption edges of highly Bi-doped Cu (Cu_(95)Bi_5). The detected x-ray magnetic circular dichroism signal corresponds to an induced magnetic moment of (2.2 + 0.5) x 10^(-12) mu(B) A^(-1) cm^(2) per Cu atom averaged over the probing depth, which is of the same order of magnitude as found for Pt measured by magneto-optics. The results highlight the importance of interface-free measurements to assess material parameters and the potential of CuBi for spin-charge conversion applications., Unión Europea. Horizonte 2020, Ministerio de Ciencia e Innovación (MICINN) / FEDER, Ministerio de Ciencia e Innovación (MICINN), Comunidad de Madrid, Centro de Excelencia Severo Ochoa (MICINN), Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

Quantum computers based on semiconductor quantum dots are proving promising contenders for large scale quantum information processing. In particular, group IV based semiconductor hosts containing an abundance of nuclear spin-zero isotopes have made considerable headway into fulfilling the requirements of a universal quantum computer. Silicon (Si) and germanium (Ge) are two elements that have played important roles in the history of classical computing, and are now poised to do the same in the future of quantum computation. In this thesis, we advance efforts in developing a quantum computer in both Si, using electron spins in Si-metaloxide- semiconductor (SiMOS) hosted quantum dots, and hole spins in planar germanium quantumwells (Ge/SiGe)., QCD/Veldhorst Lab

Bone is a complex natural material with a complex hierarchical multiscale organization, crucial to perform its functions. Ultrastructural analysis of bone is crucial for our understanding of cell to cell communication, the healthy or pathological composition of bone tissue, and its three-dimensional (3D) organization. A variety of techniques has been used to analyze bone tissue. This article describes a combined approach of optical, scanning electron, and transmission electron microscopy for the ultrastructural analysis of bone from the nanoscale to the macroscale, as illustrated by two pathological bone tissues. By following a top-down approach to investigate the multiscale organization of pathological bones, quantitative estimates were made in terms of calcium content, nearest neighbor distances of osteocytes, canaliculi diameter, ordering, and D-spacing of the collagen fibrils, and the orientation of intrafibrillar minerals which enable us to observe the fine structural details. We identify and discuss a series of two-dimensional (2D) and 3D imaging techniques that can be used to characterize bone tissue. By doing so we demonstrate that, while 2D imaging techniques provide comparable information from pathological bone tissues, significantly different structural details are observed upon analyzing the pathological bone tissues in 3D. Finally, particular attention is paid to sample preparation for and quantitative processing of data from electron microscopic analysis.

The structural investigation of biological macromolecules is indispensable in understanding the molecular mechanisms underlying diseases. Several structural biology techniques have been introduced to unravel the structural facets of biomolecules. Among these, the electron cryomicroscopy (cryo-EM) method microcrystal electron diffraction (MicroED) has produced atomic resolution structures of important biological and small molecules. Since its inception in 2013, MicroED established a demonstrated ability for solving structures of difficult samples using vanishingly small crystals. However, membrane proteins remain the next big frontier for MicroED. The intrinsic properties of membrane proteins necessitate improved sample handling and imaging techniques to be developed and optimized for MicroED. Here, we summarize the milestones of electron crystallography of two-dimensional crystals leading to MicroED of three-dimensional crystals. Then, we focus on four different membrane protein families and discuss representatives from each family solved by MicroED.

Structures of two globular proteins were determined ab initio using microcrystal electron diffraction (MicroED) data that were collected on a direct electron detector in counting mode. Microcrystals were identified using a scanning electron microscope (SEM) and thinned with a focused ion beam (FIB) to produce crystalline lamellae of ideal thickness. Continuous-rotation data were collected using an ultra-low exposure rate to enable electron counting in diffraction. For the first sample, triclinic lysozyme extending to a resolution of 0.87 Å, an ideal helical fragment of only three alanine residues provided initial phases. These phases were improved using density modification, allowing the entire atomic structure to be built automatically. A similar approach was successful on a second macromolecular sample, proteinase K, which is much larger and diffracted to a resolution of 1.5 Å. These results demonstrate that macromolecules can be determined to sub-ångström resolution by MicroED and that ab initio phasing can be successfully applied to counting data.

The tetrazine/trans-cyclooctene ligation stands out from the bioorthogonal toolbox due to its exceptional reaction kinetics, enabling multiple molecular technologies in vitro and in living systems. Highly reactive 2-pyridyl-substituted tetrazines have become state of the art for time-critical processes and selective reactions at very low concentrations. It is widely accepted that the enhanced reactivity of these chemical tools is attributed to the electron-withdrawing effect of the heteroaryl substituent. In contrast, we show that the observed reaction rates are way too high to be explained on this basis. Computational investigation of this phenomenon revealed that distortion of the tetrazine caused by intramolecular repulsive N-N interaction plays a key role in accelerating the cycloaddition step. We show that the limited stability of tetrazines in biological media strongly correlates with the electron-withdrawing effect of the substituent, while intramolecular repulsion increases the reactivity without reducing the stability. These fundamental insights reveal thus far overlooked mechanistic aspects that govern the reactivity/stability trade-off for tetrazines in physiologically relevant environments, thereby providing a new strategy that may facilitate the rational design of these bioorthogonal tools.

Photoinduced proton-coupled electron transfer and long-range two-proton transport via a Grotthuss-type mechanism are investigated in a biomimetic construct. The ultrafast, nonequilibrium dynamics are assessed via two-dimensional electronic vibrational spectroscopy, in concert with electrochemical and computational techniques. A low-frequency mode is identified experimentally and found to promote double proton and electron transfer, supported by recent theoretical simulations of a similar but abbreviated (non-photoactive) system. Excitation frequency peak evolution and center line slope dynamics show direct evidence of strongly coupled nuclear and electronic degrees of freedom, from which we can conclude that the double proton and electron transfer processes are concerted (up to an uncertainty of 24 fs). The nonequilibrium pathway from the photoexcited Franck-Condon region to the E2PT state is characterized by an ∼110 fs time scale. This study and the tools presented herein constitute a new window into hot charge transfer processes involving an electron and multiple protons.

We report on a blinded analysis of low-energy electronic recoil data from the first science run of the XENONnT dark matter experiment. Novel subsystems and the increased 5.9 ton liquid xenon target reduced the background in the (1, 30) keV search region to (15.8±1.3) events/(ton×year×keV), the lowest ever achieved in a dark matter detector and ∼5 times lower than in XENON1T. With an exposure of 1.16 ton-years, we observe no excess above background and set stringent new limits on solar axions, an enhanced neutrino magnetic moment, and bosonic dark matter.

This dissertation covers the development and calibration of the Jovian plasma Dynamics and Composition analyzer (JDC). JDC is together with five other sensors a part of the Particle Environment Package (PEP), one of the payloads of the European Space Agency's JUpiter ICy moons Explorer (JUICE) mission. The JUICE mission is designed to broaden our understanding of the Jovian system including Jupiter, the four Galilean moons (Io, Europa, Ganymede and Callisto) and Jupiter's vast magnetosphere. JUICE is planned to launch in 2023. The PEP payload will study the plasma environment around Jupiter and its moons in great detail. As one of the sensors of PEP, JDC will measure the energy distribution of positive and negative ions as well as electrons in an energy range from a few eV/q up to 35keV/q. The field of view covered by JDC spans over a full hemisphere. JDC also determines the mass of particles using the time-of-flight principle. Alternatively, there is the possibility to determine the distribution of particle arrival times to study their distribution in the time domain. In this thesis, ion-optical, mechanical, electrical, thermal, radiation shielding and instrument operation related design solutions are presented and discussed. Special attention was paid to the performance of the channel electron multipliers used as time-of-flight start detectors. To verify their performance throughout the whole mission, a full lifetime test for these detectors was successfully performed. As a result of this test a qualitative performance model for channel electron multipliers was developed. Another experiment included in this work is the determination of the residual gas pressure evolution inside of JDC. A sufficiently low residual gas pressure is required for safe operation of JDC's high voltage systems. Finally, the performance of the JDC linear electric field reflectron was verified using a dedicated prototype. The last part of this work describes the methods used for instrument, Den här avhandlingen behandlar utvecklingen och kalibreringen av instrumentetJovian plasma Dynamics and Composition analyzer (JDC). JDC utgör tillsammans med fem andra sensorer Particle Environment Package (PEP), som är ett av experimenten på European Space Agency:s rymdsond Jupiter Icy moons Explorer (JUICE). JUICE uppdrag är att bredda och fördjupa vår kunskap om Jupiter-systemet. Rymdsonden ska skjutas upp 2023 och studera Jupiter, Jupiters magnetosfär och de fyra Galileiska månarna (Io, Europa, Ganymedes och Callisto). Instrumentpaketet PEP är konstruerat för att undersöka plasmamiljön kring Jupiter och dess månar i detalj. Sensorn JDC har som sin specifika uppgift att observera energifördelningen hos positiva och negativa joner samt elektroner i ett energiområde från några få eV/q (elektronvolt per laddningsenhet) upp till 35 keV/q. JDC:s synfält är en hel hemisfär och instrumentet använder flygtidsprincipen för att bestämma massorna hos de partiklar som observeras. Det finns också en möjlighet att istället registrera partiklarnas ankomsttider för att titta på fördelningen i tidsdomänen. I avhandlingen presenteras jonoptiska, mekaniska, elektriska och termiska konstruktionslösningar för JDC. Aspekter relaterade till strålningsskärmning och drift av instrumentet diskuteras också. Vi tittar särskilt på prestandan hos de kanalelektronmultiplikatorer som används som startdetektorer i flygtidssystemet. För att undersöka hur de kommer att fungera under den långa expeditionen har ett livstidstest utförts. Utgående från resultaten har en kvalitativ prestandamodell tagits fram. Ett annat experiment som avhandlingen behandlar är undersökningen av hur residualgastrycket utvecklas inuti JDC. För att de högspänningssystem som finns inuti instrumentet ska fungera utan risk för överslag måste trycket vara tillräckligt lågt. Slutligen diskuteras användningen av en särskild prototyp för att verfiera funktionaliteten hos den så kallade ’reflektronen’, en av JDC:s centrala delar., Various Pagination.

We develop a minimal non-BCS model for the CuO2 planes with the on-site Hilbert space reduced to only three effective valence centers CuO4 with different charge, conventional spin, and orbital symmetry, combined in a charge triplet, to describe the low-energy electron structure and the phase states of HTSC cuprates. Using the S = 1 pseudospin algebra we introduce an effective spin-pseudospin Hamiltonian which takes into account local and nonlocal correlations, one- and two-particle transport, and spin exchange. The T-n phase diagrams of the complete spin-pseudospin model for the CuO2 planes were reproduced by means of a site-dependent variational approach within effective field approximation typical for spin-magnetic systems. Limiting ourselves to two-sublattice approximation and nn-couplings we arrived at several Néel-like phases in CuO2 planes for parent and doped systems with a single nonzero local order parameter: antiferromagnetic insulator, charge order, glueless d-wave Bose superfluid phase, and unusual metallic phase. However, the Maxwell's construction shows the global minimum of free energy is realized for phase separated states which are bounded by the third-order phase transition line T∗(n), which is believed to be responsible for the onset of the pseudogap phenomenon. © Published under licence by IOP Publishing Ltd.

This paper presents a new analysis of the experimental transmission spectra of polyethylene terephthalate (PET) films before and after irradiation with swift heavy ions (SHI) films, as reported previously by the authors. It is shown that the absorption edge red shift for irradiated films contains two regions of exponential form, one of which is located in the UV region and the other at lower energy, mainly in the visible part of the spectrum. The behaviour of the transmission curves under different irradiating fluences demonstrates that these two regions reflect respectively the electron-enriched core of the latent track and its electron-depleted peripheral halo. The focal point method yields a bandgap energy of 4.1 eV for the electron-enriched core of the latent track, which is similar to n-doped semiconductors, and a bandgap of about 1.3–1.5 eV for the electron-depleted halo, similar to p-doped semiconductors. The boundary between the latent track cores and halos corresponds to a conventional semiconductor p-n junction. The values of the characteristic Urbach energy determined from experimental data correspond to the nonradiative transition energy between the excited singlet and triplet levels of benzene-carboxyl complexes in repeat units of the PET chain molecule. A parallel is drawn between the SHI-induced redistribution of electrons held in structural traps in the PET film and chemical redox reactions, which involve the redistribution of electrons in chemical bonds. It is suggested that alkali etching triggers the release of excess electrons in the latent track cores, which act as a catalyst for the fragmentation of PET chain molecules along the latent tracks of the SHI irradiation. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

This dissertation covers the development and calibration of the Jovian plasma Dynamics and Composition analyzer (JDC). JDC is together with five other sensors a part of the Particle Environment Package (PEP), one of the payloads of the European Space Agency's JUpiter ICy moons Explorer (JUICE) mission. The JUICE mission is designed to broaden our understanding of the Jovian system including Jupiter, the four Galilean moons (Io, Europa, Ganymede and Callisto) and Jupiter's vast magnetosphere. JUICE is planned to launch in 2023. The PEP payload will study the plasma environment around Jupiter and its moons in great detail. As one of the sensors of PEP, JDC will measure the energy distribution of positive and negative ions as well as electrons in an energy range from a few eV/q up to 35keV/q. The field of view covered by JDC spans over a full hemisphere. JDC also determines the mass of particles using the time-of-flight principle. Alternatively, there is the possibility to determine the distribution of particle arrival times to study their distribution in the time domain. In this thesis, ion-optical, mechanical, electrical, thermal, radiation shielding and instrument operation related design solutions are presented and discussed. Special attention was paid to the performance of the channel electron multipliers used as time-of-flight start detectors. To verify their performance throughout the whole mission, a full lifetime test for these detectors was successfully performed. As a result of this test a qualitative performance model for channel electron multipliers was developed. Another experiment included in this work is the determination of the residual gas pressure evolution inside of JDC. A sufficiently low residual gas pressure is required for safe operation of JDC's high voltage systems. Finally, the performance of the JDC linear electric field reflectron was verified using a dedicated prototype. The last part of this work describes the methods used for instrument, Den här avhandlingen behandlar utvecklingen och kalibreringen av instrumentetJovian plasma Dynamics and Composition analyzer (JDC). JDC utgör tillsammans med fem andra sensorer Particle Environment Package (PEP), som är ett av experimenten på European Space Agency:s rymdsond Jupiter Icy moons Explorer (JUICE). JUICE uppdrag är att bredda och fördjupa vår kunskap om Jupiter-systemet. Rymdsonden ska skjutas upp 2023 och studera Jupiter, Jupiters magnetosfär och de fyra Galileiska månarna (Io, Europa, Ganymedes och Callisto). Instrumentpaketet PEP är konstruerat för att undersöka plasmamiljön kring Jupiter och dess månar i detalj. Sensorn JDC har som sin specifika uppgift att observera energifördelningen hos positiva och negativa joner samt elektroner i ett energiområde från några få eV/q (elektronvolt per laddningsenhet) upp till 35 keV/q. JDC:s synfält är en hel hemisfär och instrumentet använder flygtidsprincipen för att bestämma massorna hos de partiklar som observeras. Det finns också en möjlighet att istället registrera partiklarnas ankomsttider för att titta på fördelningen i tidsdomänen. I avhandlingen presenteras jonoptiska, mekaniska, elektriska och termiska konstruktionslösningar för JDC. Aspekter relaterade till strålningsskärmning och drift av instrumentet diskuteras också. Vi tittar särskilt på prestandan hos de kanalelektronmultiplikatorer som används som startdetektorer i flygtidssystemet. För att undersöka hur de kommer att fungera under den långa expeditionen har ett livstidstest utförts. Utgående från resultaten har en kvalitativ prestandamodell tagits fram. Ett annat experiment som avhandlingen behandlar är undersökningen av hur residualgastrycket utvecklas inuti JDC. För att de högspänningssystem som finns inuti instrumentet ska fungera utan risk för överslag måste trycket vara tillräckligt lågt. Slutligen diskuteras användningen av en särskild prototyp för att verfiera funktionaliteten hos den så kallade ’reflektronen’, en av JDC:s centrala delar., Various Pagination.

Revealing the positions of all the atoms in large macromolecules is powerful but only possible with neutron macromolecular crystallography (NMC). Neutrons provide a sensitive and gentle probe for the direct detection of protonation states at near-physiological temperatures and clean of artifacts caused by x rays or electrons. Currently, NMC use is restricted by the requirement for large crystal volumes even at state-of-the-art instruments such as the macromolecular neutron diffractometer at the Spallation Neutron Source. EWALD's design will break the crystal volume barrier and, thus, open the door for new types of experiments, the study of grand challenge systems, and the more routine use of NMC in biology. EWALD is a single crystal diffractometer capable of collecting data from macromolecular crystals on orders of magnitude smaller than what is currently feasible. The construction of EWALD at the Second Target Station will cause a revolution in NMC by enabling key discoveries in the biological, biomedical, and bioenergy sciences.

The structural investigation of biological macromolecules is indispensable in understanding the molecular mechanisms underlying diseases. Several structural biology techniques have been introduced to unravel the structural facets of biomolecules. Among these, the electron cryomicroscopy (cryo-EM) method microcrystal electron diffraction (MicroED) has produced atomic resolution structures of important biological and small molecules. Since its inception in 2013, MicroED established a demonstrated ability for solving structures of difficult samples using vanishingly small crystals. However, membrane proteins remain the next big frontier for MicroED. The intrinsic properties of membrane proteins necessitate improved sample handling and imaging techniques to be developed and optimized for MicroED. Here, we summarize the milestones of electron crystallography of two-dimensional crystals leading to MicroED of three-dimensional crystals. Then, we focus on four different membrane protein families and discuss representatives from each family solved by MicroED.

The anaerobic oxidation of methane coupled to sulfate reduction is a microbially mediated process requiring a syntrophic partnership between anaerobic methanotrophic (ANME) archaea and sulfate-reducing bacteria (SRB). Based on genome taxonomy, ANME lineages are polyphyletic within the phylum Halobacterota, none of which have been isolated in pure culture. Here, we reconstruct 28 ANME genomes from environmental metagenomes and flow sorted syntrophic consortia. Together with a reanalysis of previously published datasets, these genomes enable a comparative analysis of all marine ANME clades. We review the genomic features that separate ANME from their methanogenic relatives and identify what differentiates ANME clades. Large multiheme cytochromes and bioenergetic complexes predicted to be involved in novel electron bifurcation reactions are well distributed and conserved in the ANME archaea, while significant variations in the anabolic C1 pathways exists between clades. Our analysis raises the possibility that methylotrophic methanogenesis may have evolved from a methanotrophic ancestor.

Inorganic-organic hybrid materials represent a large share of newly reported structures, owing to their simple synthetic routes and customizable properties1. This proliferation has led to a characterization bottleneck: many hybrid materials are obligate microcrystals with low symmetry and severe radiation sensitivity, interfering with the standard techniques of single-crystal X-ray diffraction2,3 and electron microdiffraction4-11. Here we demonstrate small-molecule serial femtosecond X-ray crystallography (smSFX) for the determination of material crystal structures from microcrystals. We subjected microcrystalline suspensions to X-ray free-electron laser radiation12,13 and obtained thousands of randomly oriented diffraction patterns. We determined unit cells by aggregating spot-finding results into high-resolution powder diffractograms. After indexing the sparse serial patterns by a graph theory approach14, the resulting datasets can be solved and refined using standard tools for single-crystal diffraction data15-17. We describe the ab initio structure solutions of mithrene (AgSePh)18-20, thiorene (AgSPh) and tethrene (AgTePh), of which the latter two were previously unknown structures. In thiorene, we identify a geometric change in the silver-silver bonding network that is linked to its divergent optoelectronic properties20. We demonstrate that smSFX can be applied as a general technique for structure determination of beam-sensitive microcrystalline materials at near-ambient temperature and pressure.

DNA oligomers are known to serve as stabilizing ligands for silver nanoclusters (AgN-DNAs) with rod-like nanocluster geometries and nanosecond-lived fluorescence. Here, we report two AgN-DNAs that possess distinctly different structural properties and are the first to exhibit only microsecond-lived luminescence. These emitters are characterized by significant broadband downconversion from the ultraviolet/visible to the near-infrared region. Circular dichroism spectroscopy shows that the structures of these two AgN-DNAs differ significantly from previously reported AgN-DNAs. We find that these nanoclusters contain eight valence electrons, making them the first reported DNA-stabilized luminescent quasi-spherical superatoms. This work demonstrates the important role that nanocluster composition and geometry play in dictating luminescence properties of AgN-DNAs and significantly expands the space of structure-property relations that can be achieved for AgN-DNAs.

In this study, novel experimental total electron detachment cross sections for O2- collisions with benzene molecules are reported for the impact energy range (10-1000 eV), as measured with a transmission beam apparatus. By analysing the positively charged species produced during the collision events, relative total ionisation cross sections were derived in the incident energy range of 160-900 eV. Relative partial ionisation cross sections for fragments with m/z ≤ 78 u were also given in this energy range. We also confirmed that heavier compounds (m/z > 78 u) formed for impact energies between 550 and 800 eV. In order to further our knowledge about the collision dynamics governing the fragmentation of such heavier molecular compounds, we performed molecular dynamics calculations within the framework of the Density Functional Theory (DFT). These results demonstrated that the fragmentation of these heavier compounds strongly supports the experimental evidence of m/z = 39-42, 50, 60 (u) cations formation, which contributed to the broad local maximum in the total ionisation observed from 550 to 800 eV. This work reveals the reactivity induced by molecular anions colliding with hydrocarbons at high energies, processes that can take place in the interstellar medium under various local conditions.

Photoinduced proton-coupled electron transfer and long-range two-proton transport via a Grotthuss-type mechanism are investigated in a biomimetic construct. The ultrafast, nonequilibrium dynamics are assessed via two-dimensional electronic vibrational spectroscopy, in concert with electrochemical and computational techniques. A low-frequency mode is identified experimentally and found to promote double proton and electron transfer, supported by recent theoretical simulations of a similar but abbreviated (non-photoactive) system. Excitation frequency peak evolution and center line slope dynamics show direct evidence of strongly coupled nuclear and electronic degrees of freedom, from which we can conclude that the double proton and electron transfer processes are concerted (up to an uncertainty of 24 fs). The nonequilibrium pathway from the photoexcited Franck-Condon region to the E2PT state is characterized by an ∼110 fs time scale. This study and the tools presented herein constitute a new window into hot charge transfer processes involving an electron and multiple protons.

The simplest response theory methods for computing vertical excitation spectra in condensed-phase are configuration interaction with single excitations (CIS) and linear-response time-dependent density functional theory (TDDFT) within the Tamm-Dancoff approximation. In applications to X-ray absorption spectroscopy (XAS), methods like CIS and TDDFT that codify only single excitations into the wave function are prone to catastrophic errors in main-edge and post-edge features whose shapes act as a crucial fingerprint in structural analyses of liquids. We show that these errors manifest primarily due to a lack of orbital relaxation in conventional linear-response theories and that core-ionized (n - 1-electron) references, like those of electron-affinity TDDFT, can eliminate the errors in the spectral profile, even in the highest-energy parts of the post-edge. Crucially, we find that single excitations atop core-ionized references are sufficient to elucidate liquid-phase XAS spectra with semi-quantitative accuracy, opening the door for methods like electron-affinity CIS/TDDFT to be used as efficient alternatives to higher-order wave function approaches.

We develop a time-dependent second-order Green's function theory (GF2) for calculating neutral excited states in molecules. The equation of motion for the lesser Green's function (GF) is derived within the adiabatic approximation to the Kadanoff-Baym (KB) equation, using the second-order Born approximation for the self-energy. In the linear response regime, we recast the time-dependent KB equation into a Bethe-Salpeter-like equation (GF2-BSE), with a kernel approximated by the second-order Coulomb self-energy. We then apply our GF2-BSE to a set of molecules and atoms and find that GF2-BSE is superior to configuration interaction with singles (CIS) and/or time-dependent Hartree-Fock (TDHF), particularly for charge-transfer excitations, and is comparable to CIS with perturbative doubles (CIS(D)) in most cases.