Field quantization is fundamental to quantum optics and polaritonic chemistry and is usually explored in microcavities through light-matter interactions. Here, we report strong resonant coupling of the two-level excitation of a dinickel (Ni2) complex molecule with its intrinsically recycled scattering field in free space under ambient conditions using weak, off-resonant excitation. The Ni2 unit acts simultaneously as a Jaynes-Cummings (JC) molecular emitter and an angstrom-scale optical resonator. The system exhibits well-resolved resonance-fluorescence signatures, including vacuum Rabi doublets and Mollow triplets. Simulations of the second-order correlation function g (2)(τ) confirm photon antibunching and underdamped Rabi oscillations, consistent with JC dynamics. Collective coupling scales with molecular number N as Ω N = N N Ω 1 , distinct from the N Ω 1 Tavis-Cummings scaling, enabling ultrastrong coupling with few molecules. These results demonstrate that a Ni2 complex can be a chemically defined molecular quantum emitter for nonclassical light generation and used for studying polaritonic control of chemical reactivity.

Pyroptosis is a proinflammatory form of regulated cell death across the tree of life. The gasdermin (GSDM) protein family functions as an evolutionarily conserved executioner of pyroptotic cell death by forming membrane pores. As the canonical activation mechanism, proteolytic cleavage drives the formation of GSDM pores. In contrast to the well-studied modern GSDM-directed pyroptotic pathway, biochemical mechanisms of primitive GSDM pores are poorly understood. Here, we functionally characterize two primitive GSDM variants with cytotoxicity, one of which is a bacterial homolog (termed bGSDM) from Runella zeae, and the other refers to a fungal homolog (fGSDM/HET-Q1) of Podospora anserina. The cleavage of bGSDM (or fGSDM/HET-Q1) by two distantly related proteases enables the in vitro reconstitution of GSDM progenitor-gated pyroptotic pores on liposome. In particular, we present high-resolution cryo-electron microscopy structures of two primitive pyroptotic pores, consisting of a Runella bGSDM ring at 3.25 angstroms and a Podospora fGSDM pore at 2.68 angstroms. Unlike the large bGSDM pore arranged in 46-fold symmetry, the smallest fGSDM pore is composed of 20 HET-Q1 protomers. Structure-to-function studies illuminate how bGSDM/fGSDM protomers assemble into distinct membrane pores. We also investigate the feasibility of engineering primitive GSDM pores to counter top-priority bacterial/fungal pathogens. Collectively, our findings offer a primitive mechanism for lytic cell death executed by flexible pores.

We report here the structure of Pyrococcus abyssi rubredoxin determined at a resolution of 0.43 Å. This, to the best of our knowledge, represents the highest resolution protein structure yet determined. Experimentally, the determination of this structure has been made possible by a series of technical innovations and streamlined procedures that are described herein. The structure model refined with spherical scattering factors, the so-called independent atom model (IAM), reveals many positive difference densities that can be attributed to electrons at the midpoint of chemical bonds. To validate the interpretation that these do indeed represent bonding electrons, we have connected the DiSCaMB transferable aspherical atom model (TAAM) library to BUSTER. TAAM refinements resolve all positive density features in midpoints of chemical bonds. Extrapolating the findings and methodology reported here, we anticipate that it should now be possible to routinely acquire accurate X-ray diffraction data for quantum crystallography of biological macromolecules. This is particularly relevant to the study of enzyme mechanisms, which are well documented to entail quantum-mechanical phenomena.

Collagen, a fundamental constituent of the extracellular matrix, has long remained elusive to high-resolution structural characterization. Using a tailored system and optimized cryo-electron microscopy processing for long-period filaments, we determined the structure of native collagen fibrils from the porcine vitreous body, with local resolutions extending from 2.6 to 7 angstroms. Each 67-nanometer periodic unit contains type II, V/XI, and IX collagen triple helices together with opticin, at a stoichiometry of 8:4:4:4, which reveals their detailed higher-order molecular packing. Abundant galactose-glucose disaccharides modify hydroxylysine residues in conserved -glycine-X-hydroxylysine- motifs, mediating fibril packing and structural stability. Our structure uncovers the glycan-mediated assembly principle of collagen fibrils and clarifies the structure-function basis of collagens in the vitreous body.

This work presents a comprehensive device-to-circuit analysis of channel-engineered gate-all-around (GAA) FETs intended for advanced CMOS logic applications, namely the comb-shaped FET (C-FET) and inter-bridge FET (I-FET), benchmarked against a conventional nanosheet FET (NS-FET). All devices are designed according to sub-3-nm IRDS guidelines and evaluated through calibrated 3D TCAD simulations. The results show that the incorporation of vertical inter-bridge (IB) channels in C-FET and I-FET significantly enhances the effective width, leading to notable improvements in drive current, with the I-FET achieving the highest [Formula: see text] and [Formula: see text] ratio. Scalability studies reveal that the I-FET retains superior performance under variations in gate length and IB dimensions while maintaining acceptable short-channel behavior. Analog and RF evaluations indicate that both C-FET and I-FET exhibit enhanced transconductance, cut-off frequency, and reduced intrinsic delay compared to NS-FETs, making them promising candidates for high-speed applications. Circuit-level simulations using LUT-based Verilog-A models further confirm that C-FET and I-FET deliver higher switching currents and improved ring-oscillator frequencies, with the I-FET achieving the maximum [Formula: see text] across all supply voltages and stage counts. Overall, the results demonstrate that channel-engineered C-FET and I-FET architectures provide substantial performance advantages over conventional nanosheet devices, highlighting their suitability for advanced CMOS and RF systems for angstrom technology nodes.

Plasticity is critical for processing semiconductors and ceramics and advancing flexible, deformable electronics. Perovskites like CsPbX3 (X = Cl, Br, I) and SrTiO3 exhibit remarkable room-temperature plasticity through {110} < 1 1 ¯ 0> dislocations, yet their atomic structures remain unresolved. While theoretical models predict mobile, glide-dissociated dislocations, scanning transmission electron microscopy (STEM) observations often reveal sessile, climb-dissociated structures, inconsistent with their plasticity and high-temperature climb requirements. Here, employing electrostatic dose modulator (EDM)-based pulsed electron beams that maintain the original sub-angstrom resolution, we successfully resolved intrinsic, glide-dissociated dislocations in perovskites at atomic level. The beam-off intervals allow beam-induced point defects to recombine, thereby truncating the sustained period of peak defect concentrations. Switching to continuous beams instead triggers glide-to-climb transitions, where the climbed structures depend on core chemistry: anion-terminated dislocations form compact structures, while cation-terminated ones are extended. These findings elucidate the intrinsic dislocation structures and deformation mechanisms in perovskites, offering insights to other semiconductors/ceramics show similar climb-dissociation, like Al2O3. The EDM-based pulsed beam technique enables non-destructive, atomic-scale observation of beam-sensitive materials, also establishes a versatile platform for active nanostructure modulation, holding great potential for semiconductor defect engineering.

Membrane transporters move polar solutes across lipid bilayers to regulate cellular metabolism, signaling, and drug distribution. These proteins operate via an alternating-access mechanism, cycling between extracellular-, intermediate-, and intracellular-facing conformations. The human excitatory amino acid transporter 1 (EAAT1) protects neurons from excitotoxic damage by mediating the uptake of glutamate and aspartate into glial cells. Defects in EAAT1 function result in numerous pathologies, including epilepsy and ataxia, suggesting that positive modulation of these transporters might ameliorate glutamate neurotoxicity. However, developing EAAT1 activators requires understanding the timing of conformational changes, which remain largely unexplored. Here, we establish an experimental platform that combines single-molecule Förster resonance energy transfer (smFRET) to monitor real-time conformational dynamics, single-transporter activity assays to correlate dynamics with function, and cryogenic electron microscopy (cryoEM) to visualize discrete conformations at high resolution. This platform enables detection of Ångstrom-scale movements of single transporter molecules in real time, revealing that EAAT1 intersperses rapid conformational dynamics with long pauses. Slow and fast dynamics can be modulated by substrates, membrane composition, and mutations, and are correlated with the enrichment of specific structural states. We leverage this platform to investigate an EAAT1 mutation associated with severe episodic ataxia and show that it inhibits transport by stabilizing a paused cytoplasm-facing conformation. These results identify multimodal dynamics as an intrinsic, regulatable feature of EAAT1 function and, therefore, a potential therapeutic target. Henceforth, our integrated platform will facilitate investigations of other regulatory factors, including the effects of small-molecule and lipid modulators on the transport cycle.

Heteroresistance (HR) is an antibiotic resistance phenotype characterized by the presence of rare resistant subpopulations (frequency ≈ 10-7 to 10-4) within a main susceptible bacterial population. During antibiotic exposure, these subpopulations can be enriched and cause treatment failure. Standard antibiotic susceptibility testing (AST) often fails to detect HR, and the current gold-standard population analysis profile (PAP) test is labor-intensive and time-consuming. We present a digital phenotyping approach combining droplet microfluidics with image texture to detect HR from clinical isolates, including Gram-negative (Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii) and Gram-positive (Staphylococcus aureus) bacteria isolated from bloodstream infections. Our method achieves detection at subpopulation frequencies as low as 10-6 in 12 to 30 h, depending on bacterial species, which is faster than the PAP test, together with single-cell resolution and high-throughput. This computationally assisted microfluidic platform enables rapid and accurate identification of HR, representing a step toward targeted antibiotic therapy in critical infections.

Maturation of [FeFe]-hydrogenase depends on the HydF maturase, a [4Fe-4S]-containing scaffold protein that assembles and delivers the organometallic [2Fe] subsite of the H-cluster. Despite extensive research, the function of the HydF [4Fe-4S] cluster and its interaction with the [2Fe] cofactor remains unresolved, with conflicting evidence regarding cyanide linkage isomerism and the functional role of the cubane. Using [57]Fe nuclear resonance vibrational spectroscopy in combination with selective isotopic labeling, we show that the [2Fe] subsite binds adjacent to the [4Fe-4S] cluster without forming a covalent cyanide bridge, while remaining electronically coupled. Complementary protein structure predictions support this arrangement and reconcile prior spectroscopic, mutagenesis, and structural studies. Extending this framework to earlier biosynthetic steps, additional structure predictions suggest that the [4Fe-4S] cluster contributes to assembly of the CH2-NH-CH2 bridge of the [2Fe] site via interactions with the lipoate cofactor of the aminomethyl-lipoyl H-protein, thereby positioning reactive components in proximity to the [2Fe] precursor. Together, these results provide a coherent structural and mechanistic framework for HydF function across distinct stages of H-cluster biosynthesis.

Nucleosomes are the repeating unit of chromatin. They act as recognition platforms for chromatin-binding factors that coordinate genome maintenance. The chromatin remodeler Amplified in Liver Cancer 1 (ALC1) is a key component of the DNA-damage response and a promising therapeutic target in cancer. Through extensive classification of our previously deposited cryo-electron microscopy dataset, we identified a previously unresolved ALC1-nucleosome complex characterized by a more open conformation of ALC1. This is the first structure of ALC1 in which all domains are visualized in the context of a nucleosome complex, including the regulatory macro domain and a single α-helix motif within the linker. This newly identified conformation may represent an intermediate between the auto-inhibited and active states, and provides new structural insights into the conformational transitions that regulate the activity of ALC1.

Small-angle X-ray scattering (SAXS) is a powerful and widely used technique for structural biology, providing information about solution structures, i.e., without the need for crystallization or cryogenic conditions. However, its applicability is limited in cases where sample heterogeneity, conformational mixtures, or aggregation are present. While modern BioSAXS routinely employs inline purification (e.g., SEC-SAXS) to address heterogeneity, gas-phase SAXS, enabled by native mass spectrometry as a sample delivery method, offers an even higher degree of population selectivity by providing well-defined and mass-selected ion populations. The principal challenge of this approach is the inherently low particle density in the gas phase. In the present overview, we present simulations of gas-phase SAXS viral nonstructural proteins and capsids and compare them against diffraction patterns from prototypical GroEL. We evaluate the expected scattering signal under experimentally realistic conditions and discuss potential implementations and use cases at both synchrotron radiation sources and X-ray free-electron lasers, thereby outlining regimes in which gas-phase SAXS may become a viable complementary tool for structural studies.

High-temperature ceramic compound Al5C3N belongs to the scarcely studied Al-C-N system. It was originally reported as an ordered compound in noncentrosymmetric space group P63mc and described as a nanolaminate with an -Al2C-AlN-Al2C2- stacking sequence. The recently reported structural disorder in the related compound Al4SiC4 led us to question this proposed structure for Al5C3N and investigate the possibility of a disordered structure in the centrosymmetric space group P63/mmc. In the present work, we employed different synthesis routes to maximize the yield and quality of the desired phase, and applied a variety of techniques to probe the Al5C3N crystal structure. Our single-crystal X-ray diffraction analysis clearly indicates that noncentrosymmetric space group P63mc must be rejected. From a joint refinement of single-crystal X-ray and neutron powder diffraction data, the occupancies of C and N were refined at two sites in P63/mmc resulting in the stacking sequence -Al2C-Al(C/N)-Al2(C/N)2-. Furthermore, DFT calculations show that a centrosymmetric disordered structure described in a supercell has the lowest energy, 0.2 eV per formula unit, relative to the previously reported P63mc structure. The calculated band structure shows both direct and indirect bandgaps, which leads to implications for the physical properties. Finally, STEM analysis provides additional evidence that the crystal structure of Al5C3N is better described in centrosymmetric space group P63/mmc.

ConspectusElectrons and protons are the simplest particles in chemistry, and their transfers are among the most fundamental chemical reactions. It is increasingly recognized that these two particles often transfer in the same elementary kinetic step, resulting in the most common type of proton-coupled electron transfer (PCET). PCET has evolved from a curiosity to a major research field that is central to a broad range of processes in chemistry, biology, and materials science.PCET evolved from electron transfer, in both its experimental and theoretical origins. One wonders how the field would be different if it had been called electron-coupled proton transfer. This equivalent terminology illustrates that the proton is on equal footing to the electron, making PCET perhaps the simplest case where the quantum properties of both an electron and a nucleus need to be considered.The fundamental understanding of PCET in solution builds on the remarkably impactful theory of electron transfer (ET) developed by R. A. Marcus and others. At a basic level, ET theory is marked by a quadratic dependence of the reaction barrier on the reaction free energy (ΔG[⧧] on ΔG°), with normal and 'inverted' regions separated by a barrierless region (ΔG[⧧] = 0), plus an electronic coupling that determines the electron tunneling probability. The theory for PCET includes additional essential elements: the quantum mechanical treatment of the transferring proton(s) as tunneling particles, multiple channels corresponding to reactant and product electron-proton vibronic states, vibronic coupling rather than electronic coupling, and a distribution of proton donor-acceptor distances.Our recent studies of ultrafast intramolecular PCET in molecular triads were the first to demonstrate the corresponding free-energy dependence for PCET, including the inverted region. Inverted behavior was previously thought to be difficult to observe experimentally for PCET because it connects vibronic states rather than electronic states. Due to the more closely spaced vibronic state energy levels compared to electronic state energy levels, there is usually a nearly barrierless pair of reactant and product vibronic states that obviates the inverted region. For these molecular triads, however, the vibronic coupling is very small for the barrierless pair, allowing observation of the hallmark inverted region.While looking for ultrafast PCET, we discovered a new elementary chemical reaction that we denoted proton-coupled energy transfer (PCEnT). In PCEnT, proton transfer (PT) is coupled to electronic excitation energy transfer. As with PCET, PT is required for the reaction to be thermodynamically accessible. In our molecular triads, PT occurs within the phenol-pyridine acceptor unit, concerted with electron transfer to a photoexcited anthracene (PCET) or electronic excitation energy transfer from a photoexcited anthracene (PCEnT). The dominant reaction depends on the molecular substituents and reaction conditions. A theory for PCEnT with some of the same essential elements as PCET theory, along with some fundamental differences, has been developed and applied to a triad system.

Sub-Ångström macromolecular crystallography allows the construction of structural models without any prior chemical knowledge and stereochemical restraints, making it possible to visualize deviations from peptide planarity, distortions of the planarity of aromatic ring systems and subtle alternate conformation networks. It also holds the promise of observing aspherical density features and other quantum-mechanical phenomena. However, the degree to which radiation damage might affect the details that can be discerned from biological structures at such resolutions has remained unknown. To address this, we report here the first study of radiation-damage effects at sub-Ångström resolution on Pyrococcus abyssi rubredoxin. Our data, collected at 100 K, indicate that the oxidized (Fe[3+]) state of the Fe atom is preserved to a large degree at a dose of 50 kGy, whereas at 1 MGy it is partially reduced to the Fe[2+] state. Isomorphous difference maps reveal extensive conformational changes at 1 MGy that are most likely coupled to the reduction of Fe[3+]. At 1 MGy, hydrogen densities that are visible at 50 kGy are preserved, but are distinctly blurred by dose. These findings suggest that the `global' radiation damage in reciprocal space and the associated blurring of electron density in real space proceed through small structural changes that are much more extended than the local damage at specific sites which is normally seen at lower resolution. Thus, the `global' and `specific' damage could be viewed as two sides of the same coin. Our study highlights the unique benefits of using low-dose data-collection protocols on large crystals fully bathed in a large `top-hat' beam with a uniform fluence profile for accurate sub-Ångström structural investigations on macromolecules, as only this experimental configuration can deliver the uniform spatial distribution of dose necessary to resolve the fine details of progressive radiation damage: a capability for which we propose the term `resolution in dose'.

In ordinary solids, nonlinear optical responses are typically studied in terms of unit-cell averages due to the ångström-scale lattice constants. In contrast, moiré superlattices, characterized by a large length scale, unlock an often-overlooked degree of freedom: intrasupercell spatial variations of local observables. Here, we formulate the second-order direct current (dc) charge response in a spatially resolved manner, showing that even uniform optical illumination can drive a static, spatially nonuniform charge redistribution within a supercell. This effect is ubiquitous and cannot be forbidden by any crystalline symmetries. Furthermore, we identify a dominant contribution arising from diverging analytical response coefficients, which leads to linear-in-time growth of the redistribution in the absence of relaxation. This growth is driven by the convergence or divergence of local dc photocurrents. Applying our theory to twisted bilayer MoTe_{2}, we demonstrate strong, highly tunable charge modulation controlled by light intensity and frequency, opening a route to in situ, all-optical control of moiré-periodic electrostatic potentials. Our Letter underscores the importance of intracell degrees of freedom, which enable a qualitatively richer class of nonlinear optical responses in moiré superlattices.