Characteristic Ring Research Articles

Development of a carbohydrate-binding protein prediction algorithm using structural features of stacking aromatic rings

Carbohydrate-protein interactions play fundamental roles in numerous aspects of biological activities, and the search for new carbohydrate (CHO)-binding proteins (CBPs) has long been a research focus. In this study, through the analysis of CBP structures, we identified significant enrichment of aromatic residues in CHO-binding regions. We further summarized the structural features of these aromatic rings within the CHO-stacking region, namely “exposing” and “proximity” features, and developed a screening algorithm that can identify CHO-stacking Trp (tryptophan) residues based on these two features. Our Trp screening algorithm can achieve high accuracy in both CBP (specificity score 0.93) and CBS (Carbohydrate binding site, precision score 0.77) prediction using experimentally determined protein structures. We also applied our screening algorithm on AlphaGO pan-species predicted models and observed significant enrichment of carbohydrate-related functions in predicted CBP candidates across different species. Moreover, through carbohydrate arrays, we experimentally verified the CHO-binding ability of four candidate proteins, which further confirms the robustness of the algorithm. This study provides another perspective on proteome-wide CBP and CBS prediction. Our results not only help to reveal the structural mechanism of CHO-binding, but also provide a pan-species CBP dataset for future CHO-protein interaction exploration.

Structural insight into the lead identification of a dual inhibitor of PDE1B and PDE10A: Integrating pharmacophore-based virtual screening, molecular docking, and structure-activity-relationship approaches

Schizophrenia is a chronic neuropsychiatric disorder affecting more than 1% of the world's population. Current antipsychotic treatments show inadequacy in mitigating the negative and cognitive symptoms of schizophrenia. In addition, these medications cause undesirable extrapyramidal side effects. According to the studies, inhibition of phosphodiesterase (PDE) 1B and PDE10A simultaneously can alleviate positive, negative, and cognitive symptoms of schizophrenia. Thus, this study aims to identify new dual inhibitors of PDE1B and PDE10A using ligand-based pharmacophore modelling, virtual screening, and molecular docking studies. Accordingly, the generated pharmacophore models of PDE1B and PDE10A comprised hydrogen bond acceptor, aromatic ring, and hydrophobic features. These features were essential for retrieving the active hits from the Universal Natural Product Database in the virtual screening. Additional filters were subsequently employed to identify potential hits that could be developed into central nervous system-active compounds. Hits meeting all the screening criteria were subjected to docking studies with PDE1B and PDE10A. Among these hits, UNPD167314 exhibited significant binding affinities for the target receptors. It occupied the P-clamp and displayed hydrophobic, aromatic, and hydrogen bond interactions with the active site residues of both receptors, thus selected as a lead compound for the design of potent and selective dual inhibitors. The structural modifications of UNPD167314 resulted in the design of 35 novel inhibitors. Out of 35, four compounds exhibited high and comparable binding affinities for both PDE1B and PDE10A, making them promising candidates for further evaluation and optimisation.

Synthesis and Spectroscopic Properties of Diarylethene‐Subporphyrinoid Hybrids

Two novel diarylethene‐fused subporphyrinoids were prepared and characterized. A mono diarylethene derivative was obtained via a statistical condensation reaction with 2 eq. of 1,2‐dicyanobenzene and 1 eq. of thiophene‐disubstituted butenedinitrile. The symmetric triply diarylethene‐fused subporphyrazine was synthesized via a cyclotrimerization reaction of the thiophene‐disubstituted butenedinitrile derivative. These compounds were characterized by NMR spectroscopy and high‐resolution mass spectrometry. The spectroscopic properties have been measured in hexane and in chloroform. The mono diarylethene‐fused‐type compound showed photochromism at 580 nm and >700 nm wavelength, accompanied by degradation. According to DFT calculations, photoreactivity likely depends on the contribution of aromatic feature of pyrrole ring bonded to two thiophene rings.

Corrole-based conjugated monomer as a new functional molecule for designing affinity interfaces

Here, a novel corrole-based conjugated monomer, pyrrole-corrole (Py-Cor) was synthesized to design a functional interface for affinity interactions, which dramatically increases the sensor signal towards model proteins of immunoglobulin G, albumin, and lysozyme. First, the monomer was characterized by nuclear magnetic resonance spectroscopy (NMR), high-resolution mass spectrometry (HRMS), and Fourier transform infrared spectroscopy (FTIR). Then, the functional monomer was electrochemically polymerized on a gold electrode in the presence of pristine pyrrole as a comonomer. The polymeric film was characterized via both chemical and electrochemical routes by conducting cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and Raman spectroscopy measurements. Due to the metal chelating feature of the corrole ring, copper(II) [Cu(II)] ions were utilized to design a metal chelate affinity film for demonstrating their interaction capability with various proteins. Cu(II) immobilization process was achieved by voltammetry whereas the metal chelate affinity studies were performed using EIS measurements. In order to show the effect of the presence of Cu(II) ions, the sensor performance in terms of the protein recognition capabilities was carried out both in the presence/absence of Cu(II) ions. The presence of Cu(II) ions in the structure significantly improved the recognition performance of the interfaces as well as enhanced the resulted semi-circuit diameters.

Development of implantable electrode based on bioresorbable Mg alloy for tissue welding application

An implantable electrode based on bioresorbable Mg-Nd-Zn-Zr alloy was developed for next-generation radiofrequency (RF) tissue welding application, aiming to reduce thermal damage and enhance anastomotic strength. The Mg alloy electrode was designed with different structural features of cylindrical surface (CS) and continuous long ring (LR) in the welding area, and the electrothermal simulations were studied by finite element analysis (FEA). Meanwhile, the temperature variation during tissue welding was monitored and the anastomotic strength of welded tissue was assessed by measuring the avulsion force and burst pressure. FEA results showed that the mean temperature in the welding area and the proportion of necrotic tissue were significantly reduced when applying an alternating current of 110 V for 10 s to the LR electrode. In the experiment of tissue welding ex vivo, the maximum and mean temperatures of tissues welded by the LR electrode were also significantly reduced and the anastomotic strength of welded tissue could be obviously improved. Overall, an ideal welding temperature and anastomotic strength which meet the clinical requirement can be obtained after applying the LR electrode, suggesting that Mg-Nd-Zn-Zr alloy with optimal structure design shows great potential to develop implantable electrode for next-generation RF tissue welding application.

A global springback compensation method for manufacturing metallic seal ring with complex cross-section and submillimeter precision

The fabrication of complex thin-walled components with irregular cross-sectional geometries often necessitates multi-pass forming processes. The springback phenomena at the microscale level contribute significantly difficulty to the precise control of geometrical accuracy for such components. To achieve submillimeter precision control of micro features in metal seal rings, this research proposed a global springback compensation method to facilitate the attainment of the optimized surfaces of dies. Through the analysis of changes in cross-sectional shape, stress distribution and bending moment in the multiple stages, several partition points were set up to divide the cross-section into four zones. For a partitional control of the manufactured surface, the compensation magnitudes for each segment are determined by iteratively refining the compensation factors using the secant method. The iteration of compensation factors is based on the deviation of dimensions measured by finite element simulation, which greatly saves experimental costs. The experimental results indicate that the predictive dimensional alterations by the global compensation agree with the experimental ones exhibiting a maximum error of less than 3 %. Furthermore, the springback behavior during the unloading and trimming stages coupling caused a dimensional error of 14.9 % for the wave width and 8.3 % for the peak width. Following the application of coupled compensation through two iterations, a distinct decrease in the relative average errors of springback values for both part width and peak width, achieving reductions to 2.4 % and 0.6 %, respectively. Compared to the traditional single springback compensation technique, the global compensation strategy effectively mitigates the out-of-tolerance issues induced by the trimming process.

In Silico Analysis for Exploring the Potential Inhibitors Against Breast Cancer (MCF7) Using Curcumin Analogue Compounds

Breast cancer is one of the most problematic diseases in the world. Currently, there are no potential vaccines for the treatment of this disease. Therefore, finding effective compounds, such as curcumin analogs, is crucial to inhibit breast cancer. Forty-five synthesized curcumin analogs were tested on the MCF7 cell line using the MTT assay. It was shown that nine curcumin compounds, Cpd 5, Cpd 9, Cpd 17, Cpd 18, Cpd 21, Cpd 25, Cpd 28, Cpd 32, and Cpd 45, had better inhibitory activities against breast cancer. Furthermore, in silico analysis was developed using 2D and 3D QSAR models with high predictive ability, with an r2 value of 0.834. In addition, based on molecular docking, molecular dynamics, and pharmacophore results, it was shown that these nine compounds had the lowest binding free energy and were also stable during the simulation. The presence of methoxy groups, hydrogen bond donors, and aromatic ring features are the main factors that enhance the biological activity of curcumin analogs. Therefore, these compounds could serve as references for the next stage of drug design.

Cyclooctatetraene‐Embedded Carbon Nanorings

AbstractWith the prosperity of the development of carbon nanorings, certain topologically or functionally unique units‐embedded carbon nanorings have sprung up in the past decade. Herein, we report the facile and efficient synthesis of three cyclooctatetraene‐embedded carbon nanorings (COTCNRs) that contain three (COTCNR1 and COTCNR2) and four (COTCNR3) COT units in a one‐pot Yamamoto coupling. These nanorings feature hoop‐shaped segments of Gyroid (G‐), Diamond (D‐), and Primitive (P‐) type carbon schwarzites. The conformations of the trimeric nanorings COTCNR1 and COTCNR2 are shape‐persistent, whereas the tetrameric COTCNR3 possesses a flexible carbon skeleton which undergoes conformational changes upon forming host–guest complexes with fullerenes (C60 and C70), whose co‐crystals may potentially serve as fullerene‐based semiconducting supramolecular wires with electrical conductivities on the order of 10−7 S cm−1 (for C60⊂COTCNR3) and 10−8 S cm−1 (for C70⊂COTCNR3) under ambient conditions. This research not only describes highly efficient one‐step syntheses of three cyclooctatetraene‐embedded carbon nanorings which feature hoop‐shaped segments of distinctive topological carbon schwarzites, but also demonstrates the potential application in electronics of the one‐dimensional fullerene arrays secured by COTCNR3.

Cyclooctatetraene-Embedded Carbon Nanorings.

With the prosperity of the development of carbon nanorings, certain topologically or functionally unique units-embedded carbon nanorings have sprung up in the past decade. Herein, we report the facile and efficient synthesis of three cyclooctatetraene-embedded carbon nanorings (COTCNRs) that contain three (COTCNR1 and COTCNR2) and four (COTCNR3) COT units in a one-pot Yamamoto coupling. These nanorings feature hoop-shaped segments of Gyroid (G-), Diamond (D-), and Primitive (P-) type carbon schwarzites. The conformations of the trimeric nanorings COTCNR1 and COTCNR2 are shape-persistent, whereas the tetrameric COTCNR3 possesses a flexible carbon skeleton which undergoes conformational changes upon forming host-guest complexes with fullerenes (C60 and C70), whose co-crystals may potentially serve as fullerene-based semiconducting supramolecular wires with electrical conductivities on the order of 10-7 S cm-1 (for C60⊂COTCNR3) and 10-8 S cm-1 (for C70⊂COTCNR3) under ambient conditions. This research not only describes highly efficient one-step syntheses of three cyclooctatetraene-embedded carbon nanorings which feature hoop-shaped segments of distinctive topological carbon schwarzites, but also demonstrates the potential application in electronics of the one-dimensional fullerene arrays secured by COTCNR3.

Clinical characteristics and outcomes of patients with metastatic colitis-associated cancer treated with EGFR inhibitors.

37 Background: Colitis-associated cancer (CAC) is a devastating complication of inflammatory bowel disease. CAC tumor biology differs from that of sporadic colorectal cancer (CRC). Patients (pts) with (w/) metastatic CAC (mCAC) treated w/ 1st line (1L) chemotherapy have worse outcomes than pts w/ sporadic metastatic CRC (mCRC). EGFR inhibitor (EGFRi) w/ chemotherapy is standard of care for mCRC that is left (L) sided, RAS wild type (WT), without BRAF V600E mutation (mut) or ERBB2 amplification (amp). There are no published data on efficacy of EGFRi in CAC. We report outcomes of mCAC pts treated w/ EGFRi. Methods: Cases were identified by querying a prospectively maintained database of CAC pts seen at Memorial Sloan Kettering Cancer Center from 1/2000-present. Among mCAC pts who received EGFRi (n = 16), outcomes of interest: best response, progression-free survival (PFS), and overall survival (OS). PFS was calculated from date of 1st treatment w/ EGFRi until progression or death. OS was calculated from date of 1st treatment w/ EGFRi until death or last follow-up. Survival analyses were performed using Kaplan-Meier method. Data were obtained through review of electronic medical records. Results: 84 pts w/ mCAC were identified (52 L sided, 24 right [R] sided, 8 small bowel). Genomics were consistent w/ our prior reports: 79% TP53 mut, 19% APC mut, 14% MYC amp/gain, 32% KRAS mut, 4% BRAF mut, 6% ERBB2 amp. Limiting to pts w/ tumors that were L sided, RAS WT, without BRAF V600E mut or ERBB2 amp, we identified 34 (40%) mCAC pts. 16 (47%) of these pts received EGFRi as 2L or 3L therapy. 3 pts (19%) received EGFRi alone, 13 pts (81%) received EGFRi w/ FOLFIRI or irinotecan. 8 pts (50%) had tumors that were high grade and/or w/ signet ring features. Metastatic sites at initiation of EGFRi: lymph node (69%), liver (50%), lung (50%), peritoneum (38%), bone (38%), soft tissue (38%). 2 pts (12.5%, 95% CI: 1.5-38.3%) had a response, 4 pts (25%) had stable disease (SD), and 10 pts (62.5%) had progressive disease (PD) as best response. Median PFS and OS: 3.0 months (95% CI: 1.8-8.7) and 11.5 months (95% CI: 8.8-17.4), respectively. 2 additional pts w/ R sided CAC received EGFRi w/ SD and PD as best responses. Conclusions: Pts w/ mCAC, who by established criteria are eligible for treatment w/ EGFRi, have rapid progression and low response rates to EGFRi. This suggests that unlike sporadic CRC, CAC may not be driven primarily by EGFR. Many had high grade histology and unusual sites of metastases (bone, soft tissue). Experiments are under way to elucidate mechanisms underlying resistance to EGFRi and will be reported. These include immunohistochemistry for EGFR and its ligands, transcriptomic analyses to classify consensus molecular subtypes, and assessment of EGF dependence and EGFRi sensitivity in CAC organoids.

Topology of anisotropic glasses from persistent homology analysis

Glasses are typically isotropic, but permanent or transient anisotropy can be induced by tensile strain. We use persistent homology (PH) analysis to explore the topological effects of such anisotropy in SiO2Na2O glass ensembles with variable alkali concentration as a function of frozen-in anisotropic strain. Statistical information was extracted on ring (H1) and cavity (H2) features, whereby anisotropic stretching was found to induce strong variations in the ring topology of the –O-Si-O- backbone, but only minor changes in the overall cavity statistics or in the Na distribution (the Na distribution was found to be governed by H2 persistence). Tensile fracture led to total recovery of network topology relative to the pristine (isotropic) glass. In revealing such reactions, PH and persistence similarity analysis may help to differentiate purely entropic orientation and irreversible structural alterations leading to glass anisotropy.

Harnessing the benzyne insertion consequence to enable π-extended pyrido-acridine and quinazolino-phenanthridine.

Distinct protocols have been devised for the preparation of hybrid heterocyclic scaffolds like π-extended pyrido-acridines and quinazolino-phenanthridines duly materialized through Rh(III)- and Pd(II)-mediated catalytic courses commencing from acridine and quinazolimine scaffolds. Interestingly, the parent compounds (acridines and quinazolimines) are actualized from 2-aminobenzonitrile and anthranilic acid, where 2-aminobenzonitrile acts as the 1,4-dipolarophilic species and anthranilic acid as the benzyne precursor. The molecular assembly of acridine suggests the participation of two benzyne units. In addition, the structural motif of the quinazolimine ring features one benzyne unit. Further, indolizine ring containing the enaminonitrile skeleton upon exposure to benzyne forms an indolizine fused quinoline ring, decorated with three benzyne units.

Local geometry-perceptive mesh convolution with multi-ring receptive field

Learning 3D mesh representation is necessary for many computer vision and graphic tasks. Recently, some works have studied convolution methods for directly processing input meshes. However, these methods are usually weak in extracting local geometry information because of the disadvantages such as isotropic filter, neglect of mesh topology, and a small convolution field. In this paper, we introduce a local geometry-perceptive mesh convolution, which pays attention to mesh irregular structures for efficiently capturing geometry features in a multi-ring receptive field. Specifically, we define each template node’s dynamic neighbor-attention weights used in multiple attention aggregation operations for obtaining local mesh change information of different vertices in the multi-ring field. After each aggregation, a shared anisotropic filter maps the catenation of each new vertex and its neighbors for extracting geometry features of the current ring. Then, complete local geometry features of each vertex in its large local field are obtained by summing the mapped results of each aggregation. Moreover, the position features of each vertex are added to its local geometry features to get the final representation vector of the vertex. We demonstrate the proposed mesh convolution method’s strong ability in modeling 3D mesh shapes.

Comprehensive in silico discovery of c-Src tyrosine kinase inhibitors in cancer treatment: A unified approach combining pharmacophore modeling, 3D QSAR, DFT, and molecular dynamics simulation

ObjectiveTo investigate c-Src, a non-receptor tyrosine kinase dysregulated in various cancer types including colon, breast, and pancreatic cancers, as a potential drug target for cancer therapy. MethodsLigand-based pharmacophore modeling and 3D-QSAR analysis on a dataset of 34c-Src tyrosine kinase inhibitors were employed. The established pharmacophore model (DDRRR_1) features two hydrogen bond donor (D) and three aromatic ring (R) features, exhibiting favorable parameters (R2 = 0.926; Q2 = 0.895; F value = 47.9). Hypothesis validation, enrichment analysis, and contour plot analysis were conducted, followed by virtual screening of a PubChem database using the optimized pharmacophore model and filtering based on the Lipinski rule of five. ResultsThe most promising inhibitors underwent multistep molecular docking, density Functional Theory (DFT) analysis, ADMET assessments, molecular dynamics simulation, and PCA. CID_70144047 emerged as the most promising hit with all the above favorable properties. ConclusionThe study provides a comprehensive approach for identifying novel c-Src tyrosine kinase inhibitors, highlighting CID_70144047 as a promising leads with potential therapeutic applications in cancer treatment.

Structural feature-based strategy for the identification of diterpene alkaloids in Aconitum carmichaeli Debeaux

The taproot of Aconitum carmichaelii Debeaux (AC), a poisonous Traditional Chinese Medicine, has been widely used to treat joint pain, rheumatism and dysmenorrhea. Fermentation is a traditional drug processing method that reduces toxicity or increases efficacy. However, the chemical composition of AC, especially fermented AC, has not been fully elucidated. Therefore, it is necessary to establish a method to characterize the chemical composition of raw and fermented AC. In this study, a structural feature-based comprehensive strategy was employed to identify the chemical components of raw and fermented AC. A highly selective method consisting of mass defect filtering (MDF), ring double bond (RDB), nitrogen rule, and feature MS fragments filtering was established using UPLC-Q-Orbitrap-MS. By the established method, 230 diterpene alkaloids were characterized in raw AC, including 108 amine, 68 monoester, and 54 diester diterpene alkaloids. 145 of them were potential new compounds. Totals of 466 diterpene alkaloids were identified in fermented AC, including 231 amine, 162 monoester, and 73 diester diterpene alkaloids. 397 of them were potential new compounds. Ester hydrolysis, hydroxylation, and demethylation were the major transformation pathways during fermentation. An integrated approach with highly selective based on the structural feature of analytes was established and applied to identify the chemicals in AC. The strategy showed great performance in improving the accuracy and coverage of the identification by using LC-MS.

Linking Topographical Ring Features to Geochemical and Geophysical Anomalies

Circular features in forests seen from air have been studied for several decades at different locations around the world. Forest rings, as they are called in Canada’s boreal forests, express several geochemical (pH, carbonate content) and geophysical (surface potential) anomalies on their 20–30 m wide ring edges. Although it has been proposed that microbial processes may cause these anomalies, the exact mechanisms of ring formation are still unknown. We focused on the Thorn North forest ring in Ontario, Canada to correlate the surface potential anomaly to soil gas concentrations. Field measurements showed that the surface potential drop at the ring edge center is framed by peaks in CO2 production, which is linked to O2 depletion and methane generation. Carbon isotope signatures were found to drop to lighter values (down to −20‰), suggesting increased respiration. Higher concentrations of uronic acids bound to extracellular polymeric substances were found, indicating that the surface potential anomaly is linked to respiration. 16S rRNA gene sequencing of shallow soil did not indicate a dominant microbial group on the edges; instead, principal component analysis showed that the microbial composition was controlled by the substrate (clayey vs. sandy soil), therefore future studies should focus on deeper ground layers.

An orientation-free ring feature descriptor with stain-variability normalization for pathology image matching

Comprehensively analyzing the corresponding regions in the images of serial slices stained using different methods is a common but important operation in pathological diagnosis. To help increase the efficiency of the analysis, various image registration methods are proposed to match the corresponding regions in different images, but their performance is highly influenced by the rotations, deformations, and variations of staining between the serial pathology images. In this work, we propose an orientation-free ring feature descriptor with stain-variability normalization for pathology image matching. Specifically, we normalize image staining to similar levels to minimize the impact of staining differences on pathology image matching. To overcome the rotation and deformation issues, we propose a rotation-invariance orientation-free ring feature descriptor that generates novel adaptive bins from ring features to build feature vectors. We measure the Euclidean distance of the feature vectors to evaluate keypoint similarity to achieve pathology image matching. A total of 46 pairs of clinical pathology images in hematoxylin-eosin and immunohistochemistry straining to verify the performance of our method. Experimental results indicate that our method meets the pathology image matching accuracy requirements (error ¡ 300μm), especially competent for large-angle rotation cases common in clinical practice.

A MICROSCOPY INVESTIGATION OF RUBBER COMPOUND CRACK PRECURSORS AND TENSILE FRACTURE SURFACES

ABSTRACT Tensile stress–strain testing is used to investigate the fracture behavior of carbon black–reinforced styrene–butadiene rubber, using 50 replicate specimens. Four vulcanized rubber compounds are studied: a CB-filled SBR with standard mixing conditions (control), the same formulation with intentional poor mixing of the CB, and materials identical to the control material but formed by adding minor amounts of 0.5-mm-diameter glass microspheres (beads)—serving as large model defects/inclusions—using a two-roll mill at two levels, corresponding to average values of 0.78 and 6.24 beads per gauge section region of the tensile test specimen. Microscopy analysis of the resulting fracture surfaces was conducted to complement our recent publication on Weibull failure statistics for distributions of tensile strength and crack precursor size. All 200 fractured specimens from tensile testing at 23°C were imaged with light microscopy and exhibited fracture surfaces characterized by relatively smooth planes perpendicular to the uniaxial loading direction. Most tensile failures originated from the edges of the dumbbell specimens, in line with expectations from fracture mechanics. Light microscopy revealed concentric fracture ring features of high specular reflectance emanating from crack precursors, which are a universal feature of the failure process for these compounds and independent of precursor type, size, or location. Noncontact interferometric microscopy confirmed that the rings resulted from variations in surface micro-roughness, proceeding outward from the precursor as rough–smooth–rough to the edge of the fracture surface. Fracture rings were also observed for tensile tests performed at 80°C. The variation in surface roughness of the fracture surface has parallels to the stick–slip tearing behavior seen for rubbers torn at medium to high rates. To the best of the authors’ knowledge, this is the first time that such striking features have been reported.

Orbital configurations of spaceborne interferometers for studying photon rings of supermassive black holes

Recent advances in technology coupled with the progress of observational radio astronomy methods resulted in achieving a major milestone of astrophysics - a direct image of the shadow of a supermassive black hole, taken by the Earth-based Event Horizon Telescope (EHT). The EHT was able to achieve a resolution of ∼20μas, enabling it to resolve the shadows of the black holes in the centres of two celestial objects: the supergiant elliptical galaxy M87 and the Milky Way Galaxy. The EHT results mark the start of a new round of development of next generation Very Long Baseline Interferometers (VLBI) which will be able to operate at millimetre and sub-millimetre wavelengths. The inclusion of baselines exceeding the diameter of the Earth and observation at as short a wavelength as possible is imperative for further development of high resolution astronomical observations. This can be achieved by a spaceborne VLBI system. We consider the preliminary mission design of such a system, specifically focused on the detection and analysis of photon rings, an intrinsic feature of supermassive black holes. Optimised Earth, Sun–Earth L2 and Earth–Moon L2 orbit configurations for the space interferometer system are presented, all of which provide an order of magnitude improvement in resolution compared to the EHT. Such a space-borne interferometer would be able to conduct a comprehensive survey of supermassive black holes in active galactic nuclei and enable uniquely robust and accurate tests of strong gravity, through detection of the photon ring features.

2H-Phosphindole-Enabled Dearomatization and [4+2] Cycloaddition of (Hetero)Arenes.

The heavier main group multiple bonds offer an effective tool for small molecule activation. Transient 2H-phosphinidole working as a reactive phosphadiene system undergoes phospha-Diels-Alder reaction with a wide range of non-activated aromatic carbocycles and heterocycles, including naphthalene, anthracene, phenanthrene, furan, thiophene, pyrrole, pyridine, and benzo-fused heterocycles, affording concise access to a range of polycyclic fused rings feature with phosphorus at the bridgehead. These results demonstrate that non-activated (hetero)arenes are capable of acting as 2π systems in [4+2] cycloaddition with highly reactive 2H-phosphindole complex.