Bacterial microcompartments (BMCs) are versatile, genetically programmable protein shells with broad potential for enzyme encapsulation and synthetic biology. The BMC shell from Haliangium ochraceum (HO) has emerged as a tractable system for enzyme encapsulation. Despite the rapid expansion of shell-based encapsulation technologies, both mechanistic understanding and rational design of this and other shell-like encapsulation systems are restrained by a lack of quantitative cargo measurements. In this work, we establish a robust, generalizable strategy for quantifying cargo encapsulated in HO BMC shells by integrating cryo-electron tomography (cryo-ET) with small-angle X-ray scattering (SAXS). Using cryo-ET for direct measurements of internal cargo density and shell structure classifications, we have calibrated a SAXS model that can quantify encapsulated cargo under functional, solution-state conditions. Using this combined approach, we characterized the morphological and structural changes that accompany variable cargo loading in HO BMC shells, revealing how encapsulation influences shell geometry and assembly. These insights highlight constraints relevant to SAXS-based quantification and provide actionable design principles for optimizing future BMC engineering efforts. This work delivers methodological advancement and conceptual foundation for more predictive, quantitative control of protein-based enzyme encapsulation systems, offering a model that extends readily to other systems through shell dimensions and cargo molecular weight.

Directed assembly of abiotic catalysts onto biological redox protein frameworks is of interest as an approach for the synthesis of biohybrid catalysts that combine features of both synthetic and biological materials. In this report, we provide a multiscale characterization of the platinum nanoparticle (NP) hydrogen-evolving catalysts that are assembled by light-driven reductive precipitation of platinum from an aqueous salt solution onto the photosystem I protein (PSI), isolated from cyanobacteria as trimeric PSI. The resulting PSI-NP assemblies were analyzed using a combination of X-ray energy-dispersive spectroscopy (XEDS), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), small-angle X-ray scattering (SAXS), and high-energy X-ray scattering with atomic pair distribution function (PDF) analyses. The results show that the PSI-supported NPs are approximately 1.8 nm diameter disk-shaped particles that assemble at discrete sites with 145 Å separation. This separation is too large to be consistent with NP nucleation and growth at a site adjacent to the FB cofactor site. Instead, we suggest a mechanism for NP growth at hydrophobic sites on the PSI stromal surface. The NPs photoreductively assembled on the PSI stromal surface are found to be analogous to the nanostructures produced by successive cycles of atomic layer deposition (ALD) of platinum onto 40 nm porous anodic alumina oxide supports, although the mechanisms for nucleation appear to differ. This work establishes a foundation for the investigation of the reductive assembly of abiotic metal catalysts at sites connected to photochemically reducing equivalent production in PSI.

The exploitation of the strong light-matter coupling regime and exciton-polariton condensates has emerged as a compelling approach to introduce strong interactions and nonlinearities into numerous photonic applications. The use of colloidal semiconductor quantum dots with strong three-dimensional confinement as the active material in optical microcavities would be highly advantageous due to their versatile structural and compositional tunability and wet-chemical processability, as well as potentially enhanced, confinement-induced polaritonic interactions. Yet, to date, exciton-polariton condensation in a microcavity has neither been achieved with epitaxial nor with colloidal quantum dots. Here, we demonstrate room-temperature polariton condensation in a thin film of monodisperse, colloidal CsPbBr3 quantum dots, placed in a tunable optical resonator with a Gaussian-shaped deformation serving as wavelength-scale potential well for polaritons. The onset of polariton condensation under pulsed optical excitation is manifested in emission by its characteristic superlinear intensity dependence, reduced linewidth, blueshift, and extended temporal coherence.

Bacterial microcompartments (BMCs) are proteinaceous organelles that self-assemble into selectively permeable shells that encapsulate enzymatic cargo. BMCs enhance catalytic pathways by reducing crosstalk among metabolites, preventing harmful intermediates from leaking into the cytosol and increasing reaction efficiency via enzyme colocalization. The intrinsic properties of BMCs make them attractive for biotechnological engineering. However, in vivo expression methods for shell synthesis have significant drawbacks that limit the potential design space for these nanocompartments. Here, we describe the development of an efficient and rapid method for the in vitro assembly of BMC shells from their protein building blocks. Our method enables large-scale construction of BMC shells by utilizing urea as a chaotropic agent to control self-assembly and provides an approach for encapsulation of both biotic and abiotic cargo under a broad range of reaction conditions. We demonstrate an enhanced level of control over the assembly of BMC shells in vitro and expand the design parameter space for engineering BMC systems with specialized and enhanced catalytic properties.

Bacterial microcompartments (BMCs) are self-assembling protein shell structures that are widely investigated across a broad range of biological and abiotic chemistry applications. A central challenge in BMC research is the targeted capture of enzymes during shell assembly. While crystallography and cryo-EM techniques have been successful in determining BMC shell structures, there has been only limited success in visualizing the location of BMC-captured enzyme cargo. Here, we demonstrate the opportunity to use small-angle X-ray scattering (SAXS) and pair distance distribution function (PDDF) measurements combined with quantitative comparison to coordinate structure models as an approach to characterize BMC shell structures in solution conditions directly relevant to biochemical function. Using this approach, we analyzed BMC shells from Haliangium ochraceum (HO) that were isolated following expression in E. coli. The analysis allowed the BMC shell structures and the extent of encapsulated enzyme cargo to be identified. Notably, the results demonstrate that HO-BMC shells adventitiously capture significant amounts of cytoplasmic cargo during assembly in E. coli. Our findings highlight the utility of SAXS/PDDF analysis for evaluating BMC architectures and enzyme encapsulation, offering valuable insights for designing BMC shells as platforms for biological and abiotic catalyst capture within confined environments.

X-ray scattering has become a major tool in the structural characterization of nanoscale materials. Thanks to the widely available experimental and computational atomic models, coordinate-based X-ray scattering simulation has played a crucial role in data interpretation in the past two decades. However, simulation of real-space pair distance distribution functions (PDDFs) from small- and wide-angle X-ray scattering, SAXS/WAXS, has been relatively less exploited. This study presents a comparison of PDDF simulation methods, which are applied to molecular structures that range in size from β-cyclodextrin [1 kDa molecular weight (MW), 66 non-hydrogen atoms] to the satellite tobacco mosaic virus capsid (1.1 MDa MW, 81 960 non-hydrogen atoms). The results demonstrate the power of interpretation of experimental SAXS/WAXS from the real-space view, particularly by providing a more intuitive method for understanding of partial structure contributions. Furthermore, the computational efficiency of PDDF simulation algorithms makes them attractive as approaches for the analysis of large nanoscale materials and biological assemblies. The simulation methods demonstrated in this article have been implemented in stand-alone software, SolX 3.0, which is available to download from https://12idb.xray.aps.anl.gov/solx.html.

Emulating angstrom-scale dynamics of the highly selective biological ion channels is a challenging task. Recent work on angstrom-scale artificial channels has expanded our understanding of ion transport and uptake mechanisms under confinement. However, the role of chemical environment in such channels is still not well understood. Here, we report the anomalously enhanced transport and uptake of ions under confined MoS 2 -based channels that are ~five angstroms in size. The ion uptake preference in the MoS 2 -based channels can be changed by the selection of surface functional groups and ion uptake sequence due to the interplay between kinetic and thermodynamic factors that depend on whether the ions are mixed or not prior to uptake. Our work offers a holistic picture of ion transport in 2D confinement and highlights ion interplay in this regime.

The synthesis and investigation of [Rh(DHMPE)2][BF4] (1) is reported. 1 features proton-responsive 1,2-bis(di(hydroxymethyl)phosphino)ethane (DHMPE) ligands, which readily capture CO2 from atmospheric sources upon deprotonation. The protonation state of the DHMPE ligand was observed to have a significant impact on the catalytic reactivity of 1 with CO2. Deprotonation and CO2 binding to 1 results in a ~10-fold rate enhancement in catalytic degenerate CO2 reduction with formate, monitored by 12C/13C isotope exchange between H12CO2- and 13CO2. Studies performed using a similar complex lacking hydroxyl ligand functionality ([Rh(DEPE)2][BF4] where DEPE = 1,2-bis(diethylphosphino)ethane) do not show the same rate enhancements when base is added. CO2 binding to 1 is proposed to facilitate pre-organization of formate/ CO2 in the transition state to lower the activation energy and increase the observed catalytic rate. Incorporation of proton-responsive DHMPE ligands not only permits CO2 capture from air, but also provides a unique approach to accelerate the kinetics of catalytic CO2 reduction to formate.

We investigate the ultrafast electronic and thermal properties of the bulk amorphous cobalt oxide water oxidation catalysts cobalt-phosphate (CoPi) and cobalt borate (CoBi) using optical pump/X-ray probe correlated with in situ electrochemical transient absorption spectroscopy. The electronic signature of a light-generated intermediate species is compared to steady-state in situ heating X-ray absorption spectroscopy (XAS), suggestive of non-thermal contributions to charge transfer formation on ultrafast timescales. With Co K-edge transient absorption spectroscopy, we observe a net photoreduction following 400 nm excitation that also initiates a potential-dependent increase in the excited-state fraction of trapped charge carriers that persists on nanosecond to microsecond timescales and is identified as a potential precursor state to oxygen evolving reactions (OER). Distinctly, the formation of excited-state species cannot be fully explained by photothermal reaction dynamics alone, with potential contributions from electronic motion acting in concert with macroscopic redox activity. The results can influence the design of water-splitting catalytic materials for tuning dimensionality, confinement, and charge delocalization across structures.

Appreciating that the role of the solute-solvent and other outer-sphere interactions is essential for understanding chemistry and chemical dynamics in solution, experimental approaches are needed to address the structural consequences of these interactions, complementing condensed-matter simulations and coarse-grained theories. High-energy X-ray scattering (HEXS) combined with pair distribution function analysis presents the opportunity to probe these structures directly and to develop quantitative, atomistic models of molecular systems in situ in the solution phase. However, at concentrations relevant to solution-phase chemistry, the total scattering signal is dominated by the bulk solvent, prompting researchers to adopt a differential approach to eliminate this unwanted background. Though similar approaches are well established in quantitative structural studies of macromolecules in solution by small- and wide-angle X-ray scattering (SAXS/WAXS), analogous studies in the HEXS regime-where sub-ångström spatial resolution is achieved-remain underdeveloped, in part due to the lack of a rigorous theoretical description of the experiment. To address this, herein we develop a framework for differential solution scattering experiments conducted at high energies, which includes concepts of the solvent-excluded volume introduced to describe SAXS/WAXS data, as well as concepts from the time-resolved X-ray scattering community. Our theory is supported by numerical simulations and experiment and paves the way for establishing quantitative methods to determine the atomic structures of small molecules in solution with resolution approaching that of crystallography.

Transparent conducting oxides (TCOs) are widely used in thin film transistors (TFTs), displays, window coatings, and solar energy conversion applications, with varying demands on mobility, conductivity, transparency, and roughness. We investigate supercycle atomic layer deposition (ALD) dosing strategies that achieve high electron mobility while inhibiting the crystallization of In2O3-based TCOs and producing smoother films. ALD In2O3 layers (A) of varying thickness are separated by a single cycle of ALD ZnO (B) or SnO2 (C). The resulting quaternary indium zinc tin oxide (IZTO) thin film properties depend strongly on the AN:B:AN:C structure, where "N" varies from 1 to 9 In2O3 ALD cycles. The IZTO thin films remain amorphous for N < 8 or 4 sequential In2O3 layers at deposition temperatures of 150 or 175 degrees C, respectively. The highest conductivity and carrier mobility for amorphous films, 1.6 x 10-3 Omega cm and 50-55 cm2V-1s-1 respectively, are observed nearest the crystallization transition. This dilute substitution strategy produces carrier mobilities among the highest reported for amorphous indium-based materials fabricated by ALD and comparable to those of crystalline ALD indium tin oxide (ITO).

The application of grazing-incidence total X-ray scattering (GITXS) for pair distribution function (PDF) analysis using >50 keV X-rays from synchrotron light sources has created new opportunities for structural characterization of supported thin films with high resolution. Compared with grazing-incidence wide-angle X-ray scattering, which is only useful for highly ordered materials, GITXS/PDFs expand such analysis to largely disordered or nanostructured materials by examining the atomic pair correlations dependent on the direction relative to the surface of the supporting substrate. A characterization of nanocrystalline In2O3-derived thin films is presented here with in-plane-isotropic and out-of-plane-anisotropic orientational ordering of the atomic structure, each synthesized using different techniques. The atomic orientations of such films are known to vary based on the synthetic conditions. Here, an azimuthal orientational analysis of these films using GITXS with a single incident angle is shown to resolve the markedly different orientations of the atomic structures with respect to the planar support and the different degrees of long-range order, and hence, the terminal surface chemistries. It is anticipated that orientational analysis of GITXS/PDF data will offer opportunities to extend structural analyses of thin films by providing a means to qualitatively determine the major atomic orientation within nanocrystalline and, eventually, non-crystalline films.

Coherent nonlinear spectroscopy offers us a window into the system-bath interactions in materials. Specifically, the spectral lineshapes can reveal the nature and dynamics of the environmental fluctuations surrounding the system of interest. Here we will discuss how stochastic non-equilibrium exciton dynamics manifest in the peculiar lineshapes and how they provide mechanistic insights into the nature of exciton-phonon and exciton-exciton interactions in nanostructured derivatives of metal halide perovskites. Despite the success of such classical optical probes in unveiling the many-body physics in materials, we will elaborate on the ambiguities still present in the resultant photophysical models that stem primarily due to the high excitation intensities used in the measurements. We will also discuss alternative experimental methodologies based on quantum entangled photons, which may offer superior signal to noise ratio and thus enabling the measurement of many-body interactions at close to single photon excitation densities.

Photosynthetic conversion of light energy into chemical energy occurs in sheet-like membrane-bound compartments called thylakoids and is mediated by large integral membrane protein-pigment complexes called reaction centers (RCs). Oxygenic photosynthesis of higher plants, cyanobacteria and algae requires the symbiotic linking of two RCs, photosystem II (PSII) and photosystem I (PSI), to split water and assimilate carbon dioxide. Worldwide there is a large research investment in developing RC-based hybrids that utilize the highly evolved solar energy conversion capabilities of RCs to power catalytic reactions for solar fuel generation. Of particular interest is the solar-powered production of H2, a clean and renewable energy source that can replace carbon-based fossil fuels and help provide for ever-increasing global energy demands. Recently, we developed thylakoid membrane hybrids with abiotic catalysts and demonstrated that photosynthetic Z-scheme electron flow from the light-driven water oxidation at PSII can drive H2 production from PSI. One of these hybrid systems was created by self-assembling Pt-nanoparticles (PtNPs) with the stromal subunits of PSI that extend beyond the membrane plane in both spinach and cyanobacterial thylakoids. Using PtNPs as site-specific probe molecules, we report the electron microscopic (EM) imaging of oligomeric structure, location and organization of PSI in thylakoid membranes and provide the first direct visualization of photosynthetic Z-scheme solar water-splitting biohybrids for clean H2 production.

Facilitating photoinduced electron transfer (PET) while minimizing rapid charge-recombination processes to produce a long-lived charge-separated (CS) state represents a primary challenge associated with achieving efficient solar fuel production. Natural photosynthetic systems employ intermolecular interactions to arrange the electron-transfer relay in reaction centers and promote a directional flow of electrons. This work explores a similar tactic through the synthesis and ground- and excited-state characterization of two Cu(I)bis(phenanthroline) chromophores with homoleptic and heteroleptic coordination geometries and which are functionalized with negatively charged sulfonate groups. The addition of sulfonate groups enables solubility in pure water, and it also induces assembly with the dicationic electron acceptor methyl viologen (MV2+) via bimolecular, dynamic electrostatic interactions. The effect of the sulfonate groups on the ground- and excited-state properties was evaluated by comparison with the unsulfonated analogues in 1:1 acetonitrile/water. The excited-state lifetimes for all sulfonated complexes are similar to what we expect from previous literature, with the exception of the sulfonated heteroleptic complex whose metal-to-ligand charge-transfer (MLCT) lifetime in water has two components that are fit to 10 and 77 ns. For the sulfonated complexes, we detected reduced MV+• in both solvent environments following MLCT excitation, but control measurements in 1:1 acetonitrile/water with the unsulfonated analogues showed no PET to MV2+, indicating that electrostatically driven supramolecular assemblies of the sulfonated complexes with MV2+ facilitate the observed PET. Additionally, the strength of the intermolecular interactions driving the formation of these assemblies changes drastically with the solvent environment. In 1:1 acetonitrile/water, PET occurred from both sulfonated complexes with quantum yields (ΦET) of 2-3% but increased to a remarkable 98% for the sulfonated heteroleptic complex with a 3 μs CS-state lifetime in water.

Controlling the ion transport through graphene oxide (GO) membrane is challenging, particularly in the aqueous environment due to its strong swelling tendency. Fine-tuning the interlayer spacing and chemistry is critical to create highly selective membranes. We investigate the effect of single-site divalent cations in tuning GO membrane properties. Competitive ionic permeation test indicates that Cu2+ cations dominate the transport through the 2D channels of GO membrane over other cations (Mg2+/Ca2+/Co2+). Without/With the single-site M2+ modifications, pristine GO, Mg-GO, Ca-GO, and Cu-GO membranes show interlayer spacings of ∼13.6, 15.6, 14.5, and 12.3 Å in wet state, respectively. The Cu-GO membrane shows a two-fold decrease of NaCl (1 M) permeation rate comparing to pristine GO, Mg-GO, and Ca-GO membranes. In reverse osmosis tests using 1000 ppm NaCl and Na2SO4 as feeds, Cu-GO membrane shows rejection of ∼78% and ∼94%, respectively, which are 5%-10% higher than its counterpart membranes.

Die Molekülstrukturen von fünf redox- und photoaktiven Bimetallkomplexen in der Lösungsphase wurden im Forschungsartikel von Xiaosong Li, Karen L. Mulfort und Mitarbeitern mittels Hochenergie-Röntgenstreuung und paarweiser Atomverteilungsfunktion aufgedeckt (e202111764). Die Analyse zeigt signifikante Konformationsunterschiede zwischen der Lösungsphase und den Festkörperstrukturen dieser Komplexe, die für die Wechselwirkungen zwischen den beiden Metallzentren relevant sein könnten.

The cobalt-phosphate amorphous oxyhydroxide water-splitting catalyst, CoPi, is widely investigated because of its reactivity and self-repair analogous to the oxygen-evolving catalyst in Photosystem II. CoPi films show optical absorption features analogous to those seen more generally in transition metal oxides and oxygen-evolving catalysts. Possible photocatalytic properties of CoPi have, up until now, not been considered. Herein, we report on the finding of wavelength-dependent photo-electrochemical responses in CoPi. Red light excitation (623 nm) into a manifold of charge transfer and d-d electronic transitions was seen to produce photoanodic current responses that enhance OER, while blue light excitation (415 nm) within the ligand-to-metal charge-transfer transition was found to produce photocathodic responses that inhibit OER and oxidative repair. These results demonstrate intrinsic wave-length-dependent photo-electrochemistry in CoPi and opportunities to use light-excited states in CoPi, and potentially other transition metal oxides, to enhance OER and to track reaction mechanisms using light-triggered, pump-probe techniques.