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Design and implementation of aerobic and ambient CO2-reduction as an entry-point for enhanced carbon fixation
No full textThe direct reduction of CO2 into one-carbon molecules is key to highly efficient biological CO2-fixation. However, this strategy is currently restricted to anaerobic organisms and low redox potentials. In this study, we introduce the CORE cycle, a synthetic metabolic pathway that converts CO2 to formate at aerobic conditions and ambient CO2 levels, using only NADPH as a reductant. Combining theoretical pathway design and analysis, enzyme bioprospecting and high-throughput screening, modular assembly and adaptive laboratory evolution, we realize the CORE cycle in vivo and demonstrate that the cycle supports growth of E. coli by supplementing C1-metabolism and serine biosynthesis from CO2. We further analyze the theoretical potential of the CORE cycle as a new entry-point for carbon in photorespiration and autotrophy. Overall, our work expands the solution space for biological carbon reduction, offering a promising approach to enhance CO2 fixation processes such as photosynthesis, and opening avenues for synthetic autotrophy
Structure and catalytic activity of the SAM-utilizing ribozyme SAMURI
No full textRibozymes that catalyze site-specific RNA modification have recently gained increasing interest for their ability to mimic methyltransferase enzymes and for their application to install molecular tags. Recently, we reported SAMURI as a site-specific alkyltransferase ribozyme using S-adenosylmethionine (SAM) or a stabilized analog to transfer a methyl or propargyl group to N3 of an adenosine. Here, we report the crystal structures of SAMURI in the postcatalytic state. The structures reveal a three-helix junction with the catalytic core folded into four stacked layers, harboring the cofactor and the modified nucleotide. Detailed structure–activity analyses explain the cofactor scope and the structural basis for site selectivity. A structural comparison of SAMURI with SAM riboswitches sheds light on how the synthetic ribozyme overcomes the strategies of natural riboswitches to avoid self-methylation. Our results suggest that SAM and its analogs may serve as substrates for various RNA-catalyzed reactions, for which the corresponding ribozymes remain to be identified
Highly conserved ribosome biogenesis pathways between human and yeast revealed by the MDN1-NLE1 interaction and NLE1 containing pre-60S subunits
No full textThe assembly of ribosomal subunits, primarily occurring in the nucleolar and nuclear compartments, is a highly complex process crucial for cellular function. This study reveals the conservation of ribosome biogenesis between yeast and humans, illustrated by the structural similarities of ribosomal subunit intermediates. By using X-ray crystallography and cryo-EM, the interaction between the human AAA+ ATPase MDN1 and the 60S assembly factor NLE1 is compared with the yeast homologs Rea1 and Rsa4. The MDN1-MIDAS and NLE1-Ubl complex structure at 2.3 Å resolution mirrors the highly conserved interaction patterns observed in yeast. Moreover, human pre-60S intermediates bound to the dominant negative NLE1-E85A mutant revealed at 2.8 Å resolution an architecture that largely matched the equivalent yeast structures. Conformation of rRNA, assembly factors and their interaction networks are highly conserved. Additionally, novel human pre-60S intermediates with a non-rotated 5S RNP and processed ITS2/foot structure but incomplete intersubunit surface were identified to be similar to counterparts observed in yeast. These findings confirm that the MDN1-NLE1-driven transition phase of the 60S assembly is essentially identical, supporting the idea that ribosome biogenesis is a highly conserved process across eukaryotic cells, employing an evolutionary preservation of ribosomal assembly mechanisms
QCD axion strings or seeds?
No full textWe study the impact of QCD axion strings on the cosmological history of electroweak (EW) symmetry breaking, focussing on the minimal KSVZ axion model. We consider the case of the pure SM Higgs potential as well as a simple scenario with a first order EW phase transition. We capture the effect of the Peccei-Quinn (PQ) sector within an effective-theory approach for the Higgs field, where the axion string core and the heavy PQ states are integrated out. The relevant parameters in this effective theory are controlled by the size of the portal coupling between the Higgs and the PQ scalar, and the mass of the PQ radial excitation. We determine the range of portal couplings for which the axion strings can strongly affect the dynamics of EW symmetry breaking. In the case of a first order EW phase transition, the strings can act as seeds by either catalyzing the nucleation of (non-spherical) bubbles, or leading to the completion of the phase transition by triggering a classical instability
Local crystallization inside the polymer electrolyte for lithium metal batteries observed by operando nanofocus WAXS
No full textThe development of next-generation lithium-based batteries is accompanied by the intention to suppress the formation of dendritic lithium on the electrode, and is dominated by the picture that dendrites start to grow at the electrodes. Shifting from liquid to solid-state electrolytes, a high transference number is a quantity that promises the restraint of such parasitic side reactions. In this study, nanofocus X-ray wide-angle scattering is used to detect possible lithium-based crystallites in the polymer-based electrolyte. We perform operando scanning nanofocus wide-angle X-ray scattering on a composite gel-type polymer consisting of poly(vinylidene fluoride-co-hexafluoropropylene) and the single-ion conducting polymer poly((trifluoromethane) sulfonimide lithium styrene) in a lithium symmetric cell. We observe the occurrence and kinetics of lithium carbonate crystallites inside the electrolyte over a depth of 16 µm during three half-cycles. Furthermore, we prove the existence of lithium hydroxide crystallites near the lithium electrode and their absence in the bulk. Importantly, we identify the growth of pure metallic lithium inside the electrolyte as a sign of lithium dendrite growth happening inside the polymer-based electrolyte and not at the electrodes. Thus, nanofocus wide-angle X-ray scattering visualizes local structure changes such as dendrite formation inside the polymer-based electrolyte despite an unchanged electrochemical performance
Measurements of production cross-sections in collisions at TeV with the ATLAS detector
No full textMeasurements of production cross-sections are presented, providing a test of the predictions of perturbative quantum chromodynamics and the electroweak theory. The measurements are based on data from collisions at TeV recorded by the ATLAS detector at the Large Hadron Collider in 2015-2018, corresponding to an integrated luminosity of 140 fb. The number of events due to top-quark pair production, the largest background, is reduced by rejecting events containing jets with -hadron decays. An improved methodology for estimating the remaining top-quark background enables a precise measurement of cross-sections with no additional requirements on jets. The fiducial cross-section is determined in a maximum-likelihood fit with an uncertainty of 3.1%. The measurement is extrapolated to the full phase space, resulting in a total cross-section of pb. Differential cross-sections are measured as a function of twelve observables that comprehensively describe the kinematics of events. The measurements are compared with state-of-the-art theory calculations and excellent agreement with predictions is observed. A charge asymmetry in the lepton rapidity is observed as a function of the dilepton invariant mass, in agreement with the Standard Model expectation. A CP-odd observable is measured to be consistent with no CP violation. Limits on Standard Model effective field theory Wilson coefficients in the Warsaw basis are obtained from the differential cross-sections
Intermediate valence transition in epitaxial (111) films of strongly correlated Thulium monochalcogenidesZwischenvalenz-Übergänge in epitaktischen (111) Filmen aus stark korrelierten Thulium-Monochalkogeniden
No full textFundamental insights into complex quantum phases of many-body systems can be ob-tained by the investigation of the underlying particle interactions. The variety of compet-ing interactions between particles involved determines their behaviour in these quantumphases. In strongly correlated electron systems the involved particles are the localized4f-electrons and the itinerant 5d-electrons. Their interactions can lead to the fascinatingintermediate valence phase of non-integer f-occupation. In TmSe1−xTex this phase canbe induced by a semiconductor-metal transition whose volume change already indicates adrastic change in electron interaction. This phase transition makes TmSe1−xTex suitableto investigate the evolution of the electron interactions. The major issue is the unavail-ability of TmSe1−xTex crystals within the phase transition due to a miscibility gap justlocated around the point of transition. In order to close this gap and realize TmSe1−xTexcompounds throughout the whole semiconductor-metal transition, the epitaxial growthof TmSe1−xTex by molecular-beam epitaxy is chosen. The advantage of this system isthe unique possibility to study the evolution of the electron interactions by photoemissionspectroscopy since the whole phase transition and thus the emergence of intermediatevalence appears under ambient conditions. Systematic investigations on this phase tran-sition in epitaxial TmSe1−xTex have not yet been realised by photoemission spectroscopywhich is therefore the task of this work. For this purpose, a high quality epitaxial growthof TmSe1−xTex is achieved on SrF2 (111) which in addition opens a spectroscopic accessso far unavailable by bulk single crystal cleavage. Two strategies to obtain TmSe1−xTexphases throughout the phase transition are investigated. Tuning the lattice parameters ofTmTe by substrate-induced strain turns out to be not enough to reach the phase transi-tion. A direct growth of thin TmSe1−xTex films varying in xenables the investigation of theoverall electronic structure across the phase transition although the miscibility gap is notclosed by epitaxy. This includes the first ever observed bandstructure of TmTe and TmSein the (111) orientation. In the metallic phase of the transition a constant f-occupation isobserved while in the semiconducting phase the f-occupation seems to decrease towardsthe phase transition. Drastic variations in the electronic interactions are hereby displayedwhich are accompanied by the observed gap opening. The detected separation of the 4f-state in the intermediate valence phase at temperatures below 100 K is unexpected by theunderlying Anderson model. It shows the possibly necessary inclusion of other interac-tions among the electrons for the theoretical description of intermediate valence systems.With these results the basis for further investigations of electron interactions in the inter-mediate valence system TmSe1−xTex is given. The goal to provide spectroscopic access bymolecular-beam epitaxy to phases throughout the transition has not been ruled out
Pressure‐Driven Reactivity in Dense Methane‐Nitrogen Mixtures
No full textCarbon, nitrogen, and hydrogen are among the most abundant elements in the solar system, and our understanding of their interactions is fundamental to prebiotic chemistry. CH4 and N2 are the simplest archetypical molecules formed by these elements and are both markedly stable under extremes of pressure. Through a series of diamond anvil cell experiments supported by density functional theory calculations, we observe diverse compound formation and reactivity in the CH4-N2 binary system at high pressure. Above 7 GPa two concentration-dependent molecular compounds emerge, (CH4)5N2 and (CH4)7(N2)8, held together by weak van der Waals interactions. Strikingly, further compression at room temperature irreversibly breaks the N2 triple bond, inducing the dissociation of CH4 above 140 GPa, with the near-quenched samples revealing distinct spectroscopic signatures of strong covalently bonded C-N-H networks. High temperatures vastly reduce the required pressure to promote the reactivity between CH4 and N2, with NH3 forming together with longer-chain hydrocarbons at 14 GPa and 670 K, further decomposing into powdered diamond when temperatures exceed 1200 K. These results exemplify how pressure-driven chemistry can cause unexpected complexity in the most simple molecular precursors
Self-rectifying hysteresis with dynamic conductance modulation in amorphous-nanocrystalline lanthanum nickelate based memristive devices
No full textIn this work, an investigation of the structural properties of the lanthanum nickelate (LNO) films grown by metal-organic chemical vapor deposition (MOCVD) at 450 °C as well as the memristive properties of the TiN/LNO/Pt devices based on the back-end-of-the-line-compatible LNO films is carried out. We show that the films deposited at 450 °C consist of incipient nanocrystals of the LaNiO phase randomly distributed within the amorphous matrix. This peculiar nanostructure gives rise to the self-rectifying double-pinched hysteresis effect in TiN/LNO/Pt devices. In addition, the device demonstrates area dependence of the resistance in the high and low resistance states, which together with the absence of a forming process indicates nonfilamentary resistive switching, based on space charge accumulation under applied bias. The memory window can be increased through the application of a higher voltage amplitude or subsequent sweeps at constant voltage, which indicates the ability of the device for dynamic conductance modulation. Overall, self-selective and forming-free nonfilamentary TiN/LNO/Pt devices can be integrated in neuromorphic arrays without the additional selector, which allows for increased integration density
Probing the Inert Doublet Model via vector-boson fusion at a muon collider
No full textIn this work, we explore the discovery potential of the Inert Doublet Model (IDM) via the vector boson fusion (VBF) channel at a muon collider with centre-of-mass energy of 10 TeV. The Inert Doublet Model is a two-Higgs-doublet model variant with an unbroken discrete ℤ symmetry, featuring new stable scalar particles that can serve as dark matter candidates. Current dark matter data constrain the phenomenologically viable parameter space of the IDM and render certain collider signatures elusive due to tiny couplings. However, VBF-type processes can still exhibit significant enhancements compared to the Standard Model, presenting a promising avenue to probe the IDM at a high-energy muon collider. We consider as our specific target process , where H and A are the lightest and second-lightest new scalars and ℓ can be electrons or muons. We perform both cut-based and machine-learning improved sensitivity analyses for such a signal, finding a population of promising benchmark scenarios. We additionally investigate the impact of the collider energy by comparing sensitivities to the target process at 3 TeV and 10 TeV. Our results provide a clear motivation for a muon collider design capable of reaching a 10 TeV centre-of-mass energy. We furthermore discuss constraints stemming from new-physics corrections to the Higgs to di-photon decay rate as well as the trilinear Higgs coupling in detail, using state-of-the-art higher-order calculations