Selective Macrocyclization of Unprotected Peptides with an Ex Situ Gaseous Linchpin Reagent.

Peptide cyclization has dramatic effects on a variety of important properties, enhancing metabolic stability, limiting conformational flexibility, and altering cellular entry and intracellular localization. The hydrophilic, polyfunctional nature of peptides creates chemoselectivity challenges in macrocyclization, especially for natural sequences without biorthogonal handles. Herein, we describe a gaseous sulfonyl chloride-derived reagent that achieves amine-amine, amine-phenol, and amine-aniline crosslinking via a minimalist linchpin strategy that affords macrocyclic urea or carbamate products. The cyclization reaction is metal-mediated, and involves a novel application of sulfine species that remains unexplored in aqueous or biological contexts. The aqueous method delivers unique cyclic or bicyclic topologies directly from a variety of natural bioactive peptides without the need for protecting-group strategies.

Templated Synthesis of Copper Nanoclusters with a Hybrid Lysozyme-Polymer Material for Enhanced Fluorescence.

Hybrid materials that combine organic polymers and biomacromolecules offer unique opportunities for precisely controlling 3D chemical environments. Although biological or organic templates have been separately used to control the growth of inorganic nanoclusters, hybrid structures represent a relatively unexplored approach to tailoring nanocluster properties. Here, we demonstrate that a molecularly defined lysozyme-polymer resin material acts as a structural scaffold for the synthesis of copper nanoclusters (CuNCs) with well controlled size distributions. The resulting CuNCs have significantly enhanced fluorescence compared with syntheses based on polymeric or biological templates alone. The synergistic approach described here is appealing for the synthesis of biocompatible fluorescent labels with improved photostability.

B cells in the pneumococcus-infected lung are heterogeneous and require CD4+ T cell help including CD40L to become resident memory B cells.

Recovery from respiratory pneumococcal infections generates lung-localized protection against heterotypic bacteria, mediated by resident memory lymphocytes. Optimal protection in mice requires re-exposure to pneumococcus within days of initial infection. Serial surface marker phenotyping of B cell populations in a model of pneumococcal heterotypic immunity revealed that bacterial re-exposure stimulates the immediate accumulation of dynamic and heterogeneous populations of B cells in the lung, and is essential for the establishment of lung resident memory B (BRM) cells. The B cells in the early wave were activated, proliferating locally, and associated with both CD4+ T cells and CXCL13. Antagonist- and antibody-mediated interventions were implemented during this early timeframe to demonstrate that lymphocyte recirculation, CD4+ cells, and CD40 ligand (CD40L) signaling were all needed for lung BRM cell establishment, whereas CXCL13 signaling was not. While most prominent as aggregates in the loose connective tissue of bronchovascular bundles, morphometry and live lung imaging analyses showed that lung BRM cells were equally numerous as single cells dispersed throughout the alveolar septae. We propose that CD40L signaling from antigen-stimulated CD4+ T cells in the infected lung is critical to establishment of local BRM cells, which subsequently protect the airways and parenchyma against future potential infections.

Influenza Induces Lung Lymphangiogenesis Independent of YAP/TAZ Activity in Lymphatic Endothelial Cells.

The lymphatic system consists of a vessel network lined by specialized lymphatic endothelial cells (LECs) that are responsible for tissue fluid homeostasis and immune cell trafficking. The mechanisms for organ-specific LEC responses to environmental cues are not well understood. We found robust lymphangiogenesis during influenza A virus infection in the adult mouse lung. We show that the number of LECs increases 2-fold at 7 days post-influenza infection (dpi) and 3-fold at 21 dpi, and that lymphangiogenesis is preceded by lymphatic dilation. We also show that the expanded lymphatic network enhances fluid drainage to mediastinal lymph nodes. Using EdU labeling, we found that a significantly higher number of pulmonary LECs are proliferating at 7 dpi compared to LECs in homeostatic conditions. Lineage tracing during influenza indicates that new pulmonary LECs are derived from preexisting LECs rather than non-LEC progenitors. Lastly, using a conditional LEC-specific YAP/TAZ knockout model, we established that lymphangiogenesis, fluid transport and the immune response to influenza are independent of YAP/TAZ activity in LECs. These findings were unexpected, as they indicate that YAP/TAZ signaling is not crucial for these processes.

Separation of Nanoparticle Seed Pseudoisomers via Amplification of Their Crystallographic Differences.

Seed-mediated syntheses rely on small nanoparticle (NP) precursors that act as templates for growth but are often inhomogeneous with respect to their internal twinning structures (e.g., single crystalline, multiply twinned), leading to nonuniform product morphologies. To address this, we developed a method for separating seed NPs of the same approximate size (∼ 10 nm) but with different interior twinning (i.e., NP "pseudoisomers") by exaggerating their crystallographic differences through heteroexpitaxial metal overgrowth. Specifically, single crystalline and pentatwinned Au seeds that are natively inseparable via traditional methods exhibit drastically different Ag shell morphologies that allow for their selective precipitation through colloidal depletion forces. Oxidation of the Ag shell from separated particles results in seeds that are both size uniform and crystallographically pure (>99%), allowing for the controlled synthesis of a library of Oh- and D5h-symmetric gold NPs bearing {111}, {110}, {730}, {310}, {720}, and {100} facets, several of which have no precedent in the literature. These results lay the foundation for precision nanosynthesis by establishing a new paradigm for the purification of NP precursors.

GL7 ligand expression defines a novel subset of CD4+ TRM cells in lungs recovered from pneumococcus.

Streptococcus pneumoniae is the most common etiology of bacterial pneumonia, one of the leading causes of death in children and the elderly worldwide. During non-lethal infections with S. pneumoniae, lymphocytes accumulate in the lungs and protect against reinfection with serotype-mismatched strains. Cluster of differentiation CD4+ resident memory T (TRM) cells are known to be crucial for this protection, but the diversity of lung CD4+ TRM cells has yet to be fully delineated. We aimed to identify unique subsets and their contributions to lung immunity. After recovery from pneumococcal infections, we identified a distinct subset of CD4+ T cells defined by the phenotype CD11ahiCD69+GL7+ in mouse lungs. Phenotypic analyses for markers of lymphocyte memory and residence demonstrated that GL7+ T cells are a subset of CD4+ TRM cells. Functional studies revealed that unlike GL7- TRM subsets that were mostly (RAR-related Orphan Receptor gamma T) RORγT+, GL7+ TRM cells exhibited higher levels of (T-box expressed in T cells) T-bet and Gata-3, corresponding with increased synthesis of interferon-γ, interleukin-13, and interleukin-5, inherent to both T helper 1 (TH1) and TH2 functions. Thus, we propose that these cells provide novel contributions during pneumococcal pneumonia, serving as important determinants of lung immunity.

Atomically precise nanoclusters predominantly seed gold nanoparticle syntheses.

Seed-mediated synthesis strategies, in which small gold nanoparticle precursors are added to a growth solution to initiate heterogeneous nucleation, are among the most prevalent, simple, and productive methodologies for generating well-defined colloidal anisotropic nanostructures. However, the size, structure, and chemical properties of the seeds remain poorly understood, which partially explains the lack of mechanistic understanding of many particle growth reactions. Here, we identify the majority component in the seed solution as an atomically precise gold nanocluster, consisting of a 32-atom Au core with 8 halide ligands and 12 neutral ligands constituting a bound ion pair between a halide and the cationic surfactant: Au32X8[AQA+•X-]12 (X = Cl, Br; AQA = alkyl quaternary ammonium). Ligand exchange is dynamic and versatile, occurring on the order of minutes and allowing for the formation of 48 distinct Au32 clusters with AQAX (alkyl quaternary ammonium halide) ligands. Anisotropic nanoparticle syntheses seeded with solutions enriched in Au32X8[AQA+•X-]12 show narrower size distributions and fewer impurity particle shapes, indicating the importance of this cluster as a precursor to the growth of well-defined nanostructures.

Blood Variation Implicates Respiratory Limits on Elevational Ranges of Andean Birds.

AbstractThe extent to which species ranges reflect intrinsic physiological tolerances is a major question in evolutionary ecology. To date, consensus has been hindered by the limited tractability of experimental approaches across most of the tree of life. Here, we apply a macrophysiological approach to understand how hematological traits related to oxygen transport shape elevational ranges in a tropical biodiversity hot spot. Along Andean elevational gradients, we measured traits that affect blood oxygen-carrying capacity-total and cellular hemoglobin concentration and hematocrit, the volume percentage of red blood cells-for 2,355 individuals of 136 bird species. We used these data to evaluate the influence of hematological traits on elevational ranges. First, we asked whether the sensitivity of hematological traits to changes in elevation is predictive of elevational range breadth. Second, we asked whether variance in hematological traits changed as a function of distance to the nearest elevational range limit. We found that birds showing greater hematological sensitivity had broader elevational ranges, consistent with the idea that a greater acclimatization capacity facilitates elevational range expansion. We further found reduced variation in hematological traits in birds sampled near their elevational range limits and at high absolute elevations, patterns consistent with intensified natural selection, reduced effective population size, or compensatory changes in other cardiorespiratory traits. Our findings suggest that constraints on hematological sensitivity and local genetic adaptation to oxygen availability promote the evolution of the narrow elevational ranges that underpin tropical montane biodiversity.

Surface Ligands Dictate the Mechanical Properties of Inorganic Nanomaterials.

The ability for organic surface chemistry to influence the properties of inorganic nanomaterials is appreciated in some instances but is poorly understood in terms of mechanical behavior. Here we demonstrate that the global mechanical strength of a silver nanoplate can be modulated according to the local binding enthalpy of its surface ligands. A continuum-based core-shell model for nanoplate deformation shows that the interior of a particle retains bulk-like properties while the surface shell has yield strength values that depend on surface chemistry. Electron diffraction experiments reveal that, relative to the core, atoms at the nanoplate surface undergo lattice expansion and disordering directly related to the coordinating strength of the surface ligand. As a result, plastic deformation of the shell is more difficult, leading to an enhancement of the global mechanical strength of the plate. These results demonstrate a size-dependent coupling between chemistry and mechanics at the nanoscale.

Plate-Like Colloidal Metal Nanoparticles.

The pseudo-two-dimensional (2D) morphology of plate-like metal nanoparticles makes them one of the most anisotropic, mechanistically understood, and tunable structures available. Although well-known for their superior plasmonic properties, recent progress in the 2D growth of various other materials has led to an increasingly diverse family of plate-like metal nanoparticles, giving rise to numerous appealing properties and applications. In this review, we summarize recent progress on the solution-phase growth of colloidal plate-like metal nanoparticles, including plasmonic and other metals, with an emphasis on mechanistic insights for different synthetic strategies, the crystallographic habits of different metals, and the use of nanoplates as scaffolds for the synthesis of other derivative structures. We additionally highlight representative self-assembly techniques and provide a brief overview on the attractive properties and unique versatility benefiting from the 2D morphology. Finally, we share our opinions on the existing challenges and future perspectives for plate-like metal nanomaterials.

The evolution of white-tailed jackrabbit camouflage in response to past and future seasonal climates.

The genetic basis of adaptive traits has rarely been used to predict future vulnerability of populations to climate change. We show that light versus dark seasonal pelage in white-tailed jackrabbits (Lepus townsendii) tracks snow cover and is primarily determined by genetic variation at endothelin receptor type B (EDNRB), corin serine peptidase (CORIN), and agouti signaling protein (ASIP). Winter color variation was associated with deeply divergent alleles at these genes, reflecting selection on both ancestral and introgressed variation. Forecasted reductions in snow cover are likely to induce widespread camouflage mismatch. However, simulated populations with variation for darker winter pelage are predicted to adapt rapidly, providing a trait-based genetic framework to facilitate evolutionary rescue. These discoveries demonstrate how the genetic basis of climate change adaptation can inform conservation.

Branching phenomena in nanostructure synthesis illuminated by the study of Ni-based nanocomposites.

Branching phenomena are ubiquitous in both natural and artificial crystallization processes. The branched nanostructures' emergent properties depend upon their structures, but their structural tunability is limited by an inadequate understanding of their formation mechanisms. Here we developed an ensemble of Nickel-Based nano-Composites (NBCs) to investigate branching phenomena in solution-phase synthesis with precision and in depth. NBCs of 24 morphologies, including dots, core@shell dots, hollow shells, clusters, polyhedra, platelets, dendrites, urchins, and dandelions, were synthesized through systematic adjustment of multiple synthesis parameters. Relationships between the synthesis parameters and the resultant morphologies were analyzed. Classical or non-classical models of nucleation, nascent growth, 1D growth, 2D growth, 3D reconstruction, aggregation, and carburization were defined individually and then integrated to provide a holistic view of the formation mechanism of branched NBCs. Finally, guidelines were extracted and verified to guide the rational solution-phase syntheses of branched nanomaterials with emergent biological, chemical, and physical properties for potential applications in immunology, catalysis, energy storage, and optics. Demonstrating a systematic approach for deconvoluting the formation mechanism and enhancing the synthesis tunability, this work is intended to benefit the conception, development, and improvement of analogous artificial branched nanostructures. Moreover, the progress on this front of synthesis science would, hopefully, deepen our understanding of branching phenomena in nature.

Environmental iodine speciation quantification in seawater and snow using ion exchange chromatography and UV spectrophotometric detection.

The behaviour and distribution of iodine in the environment are of significant interest in a range of scientific disciplines, from health, as iodine is an essential element for humans and animals, to climate and air quality, to geochemistry. Aquatic environments are the reservoir for iodine, where it exists in low concentrations as iodide, iodate and dissolved organic iodine and in which it undergoes redox reactions. The current measurement techniques for iodine species are typically time-consuming, subject to relatively poor precision and require specialist instrumentation including those that require mercury as an electrode. We present a new method for measuring iodine species, that is tailored towards lower dissolved organic carbon waters, such as seawater, rainwater and snow, using ion exchange chromatography (IC) with direct ultra-violet spectrophotometric detection of iodide and without the need for sample pre-concentration. Simple chemical amendments to the sample allow for the quantification of both iodate and dissolved organic iodine in addition to iodide. The developed IC method, which takes 16 min, was applied to contrasting samples that encompass a wide range of aqueous environments, from Arctic sea-ice snow (low concentrations) to coastal seawater (complex sample matrix). Linear calibrations are demonstrated for all matrices, using gravimetrically prepared potassium iodide standards. The detection limit for the iodide ion is 0.12 nM based on the standard deviation of the blank, while sample reproducibility is typically <2% at >8 nM and ∼4% at <8 nM. Since there is no environmental certified reference material for iodine species, the measurements made on seawater samples using this IC method were compared to those obtained using established analytical techniques; iodide voltammetry and iodate spectrophotometry. We calculated recoveries of 102 ± 16% (n = 107) for iodide and 116 ± 9% (n = 103) for iodate, the latter difference may be due to an underestimation of iodate by the spectrophotometric method. We further compared a chemical oxidation and reduction of the sample to an ultra-violet digestion to establish the total dissolved iodine content, the average recovery following chemical amendments was 98 ± 4% (n = 92). The new method represents a simple, efficient, green, precise and sensitive method for measuring dissolved speciated iodine in complex matrices.

FGFR2b signalling restricts lineage-flexible alveolar progenitors during mouse lung development and converges in mature alveolar type 2 cells.

The specification, characterization, and fate of alveolar type 1 and type 2 (AT1 and AT2) progenitors during embryonic lung development are poorly defined. Current models of distal epithelial lineage formation fail to capture the heterogeneity and dynamic contribution of progenitor pools present during early development. Furthermore, few studies explore the pathways involved in alveolar progenitor specification and fate. In this paper, we build upon our previously published work on the regulation of airway epithelial progenitors by fibroblast growth factor receptor 2b (FGFR2b) signalling during early (E12.5) and mid (E14.5) pseudoglandular stage lung development. Our results suggest that a significant proportion of AT2 and AT1 progenitors are lineage-flexible during late pseudoglandular stage development, and that lineage commitment is regulated in part by FGFR2b signalling. We have characterized a set of direct FGFR2b targets at E16.5 which are likely involved in alveolar lineage formation. These signature genes converge on a subpopulation of AT2 cells later in development and are downregulated in AT2 cells transitioning to the AT1 lineage during repair after injury in adults. Our findings highlight the extensive heterogeneity of pneumocytes by elucidating the role of FGFR2b signalling in these cells during early airway epithelial lineage formation, as well as during repair after injury.

Lectin-like oxidized low-density lipoprotein receptor 1 attenuates pneumonia-induced lung injury.

Identifying host factors that contribute to pneumonia incidence and severity are of utmost importance to guiding the development of more effective therapies. Lectin-like oxidized low-density lipoprotein receptor 1 (LOX-1, encoded by OLR1) is a scavenger receptor known to promote vascular injury and inflammation, but whether and how LOX-1 functions in the lung are unknown. Here, we provide evidence of substantial accumulation of LOX-1 in the lungs of patients with acute respiratory distress syndrome and in mice with pneumonia. Unlike previously described injurious contributions of LOX-1, we found that LOX-1 is uniquely protective in the pulmonary airspaces, limiting proteinaceous edema and inflammation. We also identified alveolar macrophages and recruited neutrophils as 2 prominent sites of LOX-1 expression in the lungs, whereby macrophages are capable of further induction during pneumonia and neutrophils exhibit a rapid, but heterogenous, elevation of LOX-1 in the infected lung. Blockade of LOX-1 led to dysregulated immune signaling in alveolar macrophages, marked by alterations in activation markers and a concomitant elevation of inflammatory gene networks. However, bone marrow chimeras also suggested a prominent role for neutrophils in LOX-1-mediated lung protection, further supported by LOX-1+ neutrophils exhibiting transcriptional changes consistent with reparative processes. Taken together, this work establishes LOX-1 as a tissue-protective factor in the lungs during pneumonia, possibly mediated by its influence on immune signaling in alveolar macrophages and LOX-1+ airspace neutrophils.

Assembly of planar chiral superlattices from achiral building blocks.

The spontaneous assembly of chiral structures from building blocks that lack chirality is fundamentally important for colloidal chemistry and has implications for the formation of advanced optical materials. Here, we find that purified achiral gold tetrahedron-shaped nanoparticles assemble into two-dimensional superlattices that exhibit planar chirality under a balance of repulsive electrostatic and attractive van der Waals and depletion forces. A model accounting for these interactions shows that the growth of planar structures is kinetically preferred over similar three-dimensional products, explaining their selective formation. Exploration and mapping of different packing symmetries demonstrates that the hexagonal chiral phase forms exclusively because of geometric constraints imposed by the presence of constituent tetrahedra with sharp tips. A formation mechanism is proposed in which the chiral phase nucleates from within a related 2D achiral phase by clockwise or counterclockwise rotation of tetrahedra about their central axis. These results lay the scientific foundation for the high-throughput assembly of planar chiral metamaterials.

Subterranean carbon flows from source to stygofauna: a case study on the atyid shrimp Stygiocaris stylifera (Holthuis, 1960) from Barrow Island (WA).

Groundwater biota are crucial for the ecological functioning of subterranean ecosystems. However, while knowledge of the taxonomic diversity of groundwater invertebrates (stygofauna) is increasing, functional ecological information is still limited. Here, we investigate seldom empirically tested assumptions around stygofaunal trophic plasticity in coping with oligotrophic habitats. We focus on Barrow Island (Western Australia), an ideal natural laboratory due to the occurrence of natural oil seeps in association with aquifers. The trophic position and food source use of the endemic atyid shrimp Stygiocaris stylifera (Holthuis, 1960) were assessed via δ13C and δ15N stable isotope analysis (SIA). Background information on the environmental conditions was gathered through hydrochemical data and δ13C SIA combined with 14C data from dissolved inorganic/organic carbon and particulate organic carbon from groundwater samples. Our results indicate carbon enrichment in proximity to the natural oil seepage coupled with changes in trophic positions of S. stylifera from higher consumers/predators to biofilm grazers/decomposers. These results are consistent with an increased involvement of hydrocarbon seeps and associated microbial communities in the carbon flows and confirm potential for the trophic flexibility in stygofauna. Further investigations involving other trophic groups will help elucidate the functioning of the ecosystems at a community level.

Fgfr2b signaling is essential for the maintenance of the alveolar epithelial type 2 lineage during lung homeostasis in mice.

Fibroblast growth factor receptor 2b (Fgfr2b) signaling is essential throughout lung development to form the alveolar epithelial lineage. However, its role in alveolar epithelial type 2 cells (AT2s) homeostasis was recently considered dispensable. SftpcCreERT2; Fgfr2bflox/flox; tdTomatoflox/flox mice were used to delete Fgfr2b expression in cells belonging to the AT2 lineage, which contains mature AT2s and a novel SftpcLow lineage-traced population called "injury activated alveolar progenitors" or IAAPs. Upon continuous tamoxifen exposure for either 1 or 2 weeks to delete Fgfr2b, a shrinking of the AT2 population is observed. Mature AT2s exit the cell cycle, undergo apoptosis and fail to form alveolospheres in vitro. However, the lung morphometry appears normal, suggesting the involvement of compensatory mechanisms. In mutant lungs, IAAPs which escaped Fgfr2b deletion expand, display enhanced alveolosphere formation in vitro and increase drastically their AT2 signature, suggesting differentiation towards mature AT2s. Interestingly, a significant increase in AT2s and decrease in IAPPs occurs after a 1-week tamoxifen exposure followed by an 8-week chase period. Although mature AT2s partially recover their alveolosphere formation capabilities, the IAAPs no longer display this property. Single-cell RNA seq analysis confirms that AT2s and IAAPs represent stable and distinct cell populations and recapitulate some of their characteristics observed in vivo. Our results underscore the essential role played by Fgfr2b signaling in the maintenance of the AT2 lineage in the adult lung during homeostasis and suggest that the IAAPs could represent a new population of AT2 progenitors.

Cell-Surface Programmed Death Ligand-1 Expression Identifies a Sub-Population of Distal Epithelial Cells Enriched in Idiopathic Pulmonary Fibrosis.

Idiopathic lung fibrosis (IPF) is a fatal lung disease characterized by chronic epithelial injury and exhausted repair capacity of the alveolar compartment, associated with the expansion of cells with intermediate alveolar epithelial cell (AT2) characteristics. Using SftpcCreERT2/+: tdTomatoflox/flox mice, we previously identified a lung population of quiescent injury-activated alveolar epithelial progenitors (IAAPs), marked by low expression of the AT2 lineage trace marker tdTomato (Tomlow) and characterized by high levels of Pd-l1 (Cd274) expression. This led us to hypothesize that a population with similar properties exists in the human lung. To that end, we used flow cytometry to characterize the CD274 cell-surface expression in lung epithelial cells isolated from donor and end-stage IPF lungs. The identity and functional behavior of these cells were further characterized by qPCR analysis, in vitro organoid formation, and ex vivo precision-cut lung slices (PCLSs). Our analysis led to the identification of a population of CD274pos cells expressing intermediate levels of SFTPC, which was expanded in IPF lungs. While donor CD274pos cells initiated clone formation, they did not expand significantly in 3D organoids in AT2-supportive conditions. However, an increased number of CD274pos cells was found in cultured PCLS. In conclusion, we demonstrate that, similar to IAAPs in the mouse lung, a population of CD274-expressing cells exists in the normal human lung, and this population is expanded in the IPF lung and in an ex vivo PCLS assay, suggestive of progenitor cell behavior. CD274 function in these cells as a checkpoint inhibitor may be crucial for their progenitor function, suggesting that CD274 inhibition, unless specifically targeted, might further injure the already precarious lung epithelial compartment in IPF.