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Phosphorylation of G-protein-coupled receptors (GPCRs) by GPCR kinases (GRKs) desensitizes G-protein signalling and promotes arrestin signalling, which is also modulated by biased ligands1–6. The molecular assembly of GRKs on GPCRs and the basis of GRK-mediated biased signalling remain largely unknown owing to the weak GPCR–GRK interactions. Here we report the complex structure of neurotensin receptor 1 (NTSR1) bound to GRK2, Gαqand the arrestin-biased ligand SBI-5537. The density map reveals the arrangement of the intact GRK2 with the receptor, with the N-terminal helix of GRK2 docking into the open cytoplasmic pocket formed by the outward movement of the receptor transmembrane helix 6, analogous to the binding of the G protein to the receptor. SBI-553 binds at the interface between GRK2 and NTSR1 to enhance GRK2 binding. The binding mode of SBI-553 is compatible with arrestin binding but clashes with the binding of Gαqprotein, thus providing a mechanism for its arrestin-biased signalling capability. In sum, our structure provides a rational model for understanding the details of GPCR–GRK interactions and GRK2-mediated biased signalling.

Class B G-protein-coupled receptors (GPCRs), including glucagon-like peptide 1 receptor (GLP1R) and parathyroid hormone 1 receptor (PTH1R), are important drug targets1–5. Injectable peptide drugs targeting these receptors have been developed, but orally available small-molecule drugs remain under development6,7. Here we report the high-resolution structure of human PTH1R in complex with the stimulatory G protein (Gs) and a small-molecule agonist, PCO371, which reveals an unexpected binding mode of PCO371 at the cytoplasmic interface of PTH1R with Gs. The PCO371-binding site is totally different from all binding sites previously reported for small molecules or peptide ligands in GPCRs. The residues that make up the PCO371-binding pocket are conserved in class B GPCRs, and a single alteration in PTH2R and two residue alterations in GLP1R convert these receptors to respond to PCO371. Functional assays reveal that PCO371 is a G-protein-biased agonist that is defective in promoting PTH1R-mediated arrestin signalling. Together, these results uncover a distinct binding site for designing small-molecule agonists for PTH1R and possibly other members of the class B GPCRs and define a receptor conformation that is specific only for G-protein activation but not arrestin signalling. These insights should facilitate the design of distinct types of class B GPCR small-molecule agonist for various therapeutic indications.

Platelet-activating factor (PAF) is a potent phospholipid mediator crucial in multiple inflammatory and immune responses through binding and activating the PAF receptor (PAFR). However, drug development targeting the PAFR has been limited, partly due to an incomplete understanding of its activation mechanism. Here, we present a 2.9-Å structure of the PAF-bound PAFR-Gicomplex. Structural and mutagenesis analyses unveil a specific binding mode of PAF, with the choline head forming cation-π interactions within PAFR hydrophobic pocket, while the alkyl tail penetrates deeply into an aromatic cleft between TM4 and TM5. Binding of PAF modulates conformational changes in key motifs of PAFR, triggering the outward movement of TM6, TM7, and helix 8 for G protein coupling. Molecular dynamics simulation suggests a membrane-side pathway for PAF entry into PAFR via the TM4-TM5 cavity. By providing molecular insights into PAFR signaling, this work contributes a foundation for developing therapeutic interventions targeting PAF signal axis.

Tuning the performance of nanoparticle (NP) catalysts by controlling the NP surface strain has evolved as an important strategy to optimize NP catalysis in many energy conversion reactions. Here, we present our new study on using an eigenforce model to predict and experiments to verify the strain-induced catalysis enhancement of the oxygen reduction reaction (ORR) in the presence of L10-CoMPt NPs (M = Mn, Fe, Ni, Cu, Ni). The eigenforce model allowed us to predict anisotropic (that is, two-dimensional) strain levels on distorted Pt(111) surfaces. Experimentally, by preparing a series of 5 nm L10-CoMPt NPs, we could push the ORR catalytic activity of these NPs toward the optimum region of the theoretical two-dimensional volcano plot predicted for L10-CoMPt. The best ORR catalyst in the alloy NP series we studied is L10-CoNiPt, which has a mass activity of 3.1 A/mgPtand a specific activity of 9.3 mA/cm2at room temperature with only 15.9% loss of mass activity after 30 000 cycles at 60 °C in 0.1 M HClO4.

Understanding the Cu-catalyzed electrochemical CO2reduction reaction (CO2RR) under ambient conditions is both fundamentally interesting and technologically important for selective CO2RR to hydrocarbons. Current Cu catalysts studied for the CO2RR can show high activity but tend to yield a mixture of different hydrocarbons, posing a serious challenge on using any of these catalysts for selective CO2RR. Here, we report a new perovskite-type copper(I) nitride (Cu3N) nanocube (NC) catalyst for selective CO2RR. The 25 nm Cu3N NCs show high CO2RR selectivity and stability to ethylene (C2H4) at −1.6 V (vs reversible hydrogen electrode (RHE)) with the Faradaic efficiency of 60%, mass activity of 34 A/g, and C2H4/CH4molar ratio of >2000. More detailed electrochemical characterization, X-ray photon spectroscopy, and density functional theory calculations suggest that the high CO2RR selectivity is likely a result of (100) Cu(I) stabilization by the Cu3N structure, which favors CO–CHO coupling on the (100) Cu3N surface, leading to selective formation of C2H4. Our study presents a good example of utilizing metal nitrides as highly efficient nanocatalysts for selective CO2RR to hydrocarbons that will be important for sustainable chemistry/energy applications.

Springback caused by elastic recovery is known to be a major disadvantage in sheet metal forming. Many studies focused on the prediction and compensation of springback in the bending process have used simulation and numerical methods, with experimental tests rarely being reported. A new approach, aimed at decreasing springback, is presented in this paper to solve the springback problem and provide a reference for other researchers. A new edge bending method called “incremental bending” has been developed and implemented on aluminum sheet at room temperature. Using this method, bending strain was lowered, leading to a reduction in springback. 3D Digital Image Correlation, an optical measurement technique, was adopted simultaneously to provide a high accuracy measurement of the full field strain distribution and springback curvature, making it very suitable for springback measurement. The experimental results show an obvious reduction of springback, which agrees well with the theoretical analysis. This work could help to minimize springback in sheet metal bending dramatically and improve formability and productivity, as well as provide a reference for researchers studying cold-bending. Details of the basic bending theory, experimental method, experimental results, and analysis will be demonstrated in the following content.

Intermetallic nanoparticles (NPs) described in this Account are a class of metallic alloy NPs within which metal atoms are bonded via strong d-orbital interaction and ordered anisotropically in a specific crystallographic direction. Compared to the common metallic alloy NPs with solid solution structure, intermetallic NPs are generally more stable against chemical oxidation and etching. The strict stoichiometry requirement, well-defined atom binding environment and layered atomic arrangement also make intermetallic NPs an ideal model for understanding their physical and catalytic properties. This account summarizes the synthetic principles and strategies developed to obtain monodisperse intermetallic NPs, especially tetragonal L10-NPs. The thermodynamics and kinetics involved in the conversion between disordered and ordered structures are briefly discussed. The synthetic methods are grouped into two slightly different categories: solution-phase synthesis followed by solid state annealing and direct solution-phase synthesis. In the former method, high-surface-area supports are often needed to disperse NPs and to prevent them from aggregation, while in the latter method such supports are not required since the structure conversion temperature is lowered to a level that the conversion can proceed in the solution reaction condition. In any of these two synthetic approaches, various factors influencing intermetallic structure formation should be carefully controlled to ensure more complete structural transition within NPs. Using representative synthetic examples, we highlight the strategies explored to facilitate the formation of intermetallic structure, including the introduction of vacancies/defects within NP structures and the control of atom addition rate/seed-mediated diffusion to lower the energy barrier. These strategies illustrate how the concept of thermodynamics and kinetics can be used to design the synthesis of intermetallic NPs. Additionally, to correlate NP structure and catalysis, we introduce briefly the d-band theory to explain how the electronic, strain and ensemble effects can be used to tune NP catalysis. We focus specifically on Pt-, Pd-, and Au-based L10-NPs and demonstrate how these L10-NPs could be prepared to show much enhanced catalysis for electrochemical reactions, including oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), formic acid oxidation reaction (FAOR), and thermo-oxidation reaction of CO. Due to the enhanced metal atom stability in the “sandwich”-type structure, the roles of the first-row transition metal atoms in catalysis are better understood to achieve catalysis optimization. This concept can be extended to other alloy NPs, demonstrating great potentials in using intermetallic structures to control NP reduction and oxidation catalysis for important chemical and energy applications.

Stabilizing transition metals (M) in MPt alloy under acidic conditions is challenging, yet crucial to boost Pt catalysis toward oxygen reduction reaction (ORR). We synthesized ∼9 nm hard-magnet core/shell L10-CoPt/Pt nanoparticles with 2–3 atomic layers of strained Pt shell for ORR. At 60°C in acid, the hard-magnet L10-CoPt better stabilizes Co (5% loss after 24 hr) than soft-magnet A1-CoPt (34% loss in 7 hr). L10-CoPt/Pt achieves mass activities (MA) of 0.56 A/mgPtinitially and 0.45 A/mgPtafter 30,000 voltage cycles in the membrane electrode assembly at 80°C, exceeding the DOE 2020 targets on Pt activity and durability (0.44 A/mgPtin MA and <40% loss in MA after 30,000 cycles). Density functional theory calculations suggest that the ligand effect of Co and the biaxial strain (−4.50%/−4.25%) of the Pt shell weaken the binding of oxygenated species, leading to enhanced ORR performance in fuel cells.

We report a new strategy of controlling catalytic activity and selectivity of Cu nanoparticles (NPs) for the ammonia borane initiated hydrogenation reaction. Cu NPs are active and selective for chemoselective reduction of nitrostyrene to vinylaniline under ambient conditions. Their activity, selectivity, and more importantly, stability are greatly enhanced by their anchoring on WO2.72nanorods, providing a room-temperature full conversion of nitrostyrene selectively to vinylaniline (>99% yield). Compared with all other catalysts developed thus far, our new Cu/WO2.72catalyst shows much enhanced hydrogenation selectivity and stability without the use of pressured hydrogen. The synthetic approach demonstrated here can be extended to prepare various M/WO2.72catalysts (M = Fe, Co, Ni), with M being stabilized for many chemical reactions.

Many population genomic studies have been conducted in the past to search for traces of recent events of positive selection. These traces, however, can be obscured by temporal variation of population size or other demographic factors. To reduce the confounding impact of demography, the coalescent tree topology has been used as an additional source of information for detecting recent positive selection in a population or a species. Based on the branching pattern at the root, we partition the hypothetical coalescent tree, inferred from a sequence sample, into two subtrees. The reasoning is that positive selection could impose a strong impact on branch length in one of the two subtrees while demography has the same effect on average on both subtrees. Thus, positive selection should be detectable by comparing statistics calculated for the two subtrees. Simulations demonstrate that the proposed test based on these principles has high power to detect recent positive selection even when DNA polymorphism data from only one locus is available, and that it is robust to the confounding effect of demography. One feature is that all components in the summary statistics (Du) can be computed analytically. Moreover, misinference of derived and ancestral alleles is seen to have only a limited effect on the test, and it therefore avoids a notorious problem when searching for traces of recent positive selection.

The spatial phase-shift technique has been successfully applied to an out-of-plane speckle interferometry system. Its application to a pure in-plane sensitive system has not been reported yet. This paper presents a novel optical configuration that enables the application of the spatial phase-shift technique to pure in-plane sensitive dual-beam speckle interferometry. The new spatial phase-shift dual-beam speckle interferometry (SPS-DBSP) uses a dual-beam in-plane electronic speckle pattern interferometry configuration with individual aperture shears, avoiding the interference in the object plane by the use of a low-coherence source, and different optical paths. The measured object is illuminated by two incoherent beams that are generated by a delay line, which is larger than the coherence length of the laser. The two beams reflected from the object surface interfere with each other at the CCD plane because of different optical paths. A spatial phase shift is introduced by the angle between the two apertures when they are mapped to the same optical axis. The phase of the in-plane deformation can directly be extracted from the speckle patterns by the Fourier transform method. The capability of SPS-DBSI is demonstrated by theoretical discussion as well as experiments.

A novel 3D digital image correlation (DIC) system based on a single three charge-couple device (3CCD) color camera is proposed in this paper. Images from three different perspectives are captured by a 3CCD camera using a reflective-based pseudo-vision system. These images are then separated by the different CCD channels, and the correlation algorithm for the multi-camera DIC system is adopted to evaluate the images. Compared to the conventional multi-camera DIC system, the proposed system is much more compact. In addition, the proposed system has no loss of spatial resolution, compares to the traditional single camera DIC system. The complex surface measurement ability and the measurement accuracy is significantly improved through the use of the multi-camera DIC algorithm. The principle of the proposed system is described in detail as well as the experimental setup. A series of validation tests are performed, and the results are verified with the commercial 3D-DIC system.

NixWO2.72nanorods (NRs) are synthesized by a one-pot reaction of Ni(acac)2and WCl4. In the rod structure, Ni(II) intercalates in the defective perovskite-type WO2.72and is stabilized. The NixWO2.72NRs show the x-dependent electrocatalysis for the oxygen evolution reaction (OER) in 0.1 M KOH with Ni0.78WO2.72being the most efficient, even outperforming the commercial Ir-catalyst. The synthesis is not limited to NixWO2.72but can be extended to MxWO2.72(M = Co, Fe) as well, providing a new class of oxide-based catalysts for efficient OER and other energy conversion reactions.

The 26S proteasome is an ATP-dependent dynamic 2.5 MDa protease that regulates numerous essential cellular functions through degradation of ubiquitinated substrates. Here we present a near-atomic-resolution cryo-EM map of the S. cerevisiae 26S proteasome in complex with ADP-AlFx. Our biochemical and structural data reveal that the proteasome-ADP-AlFx is in an activated state, displaying a distinct conformational configuration especially in the AAA-ATPase motor region. Noteworthy, this map demonstrates an asymmetric nucleotide binding pattern with four consecutive AAA-ATPase subunits bound with nucleotide. The remaining two subunits, Rpt2 and Rpt6, with empty or only partially occupied nucleotide pocket exhibit pronounced conformational changes in the AAA-ATPase ring, which may represent a collective result of allosteric cooperativity of all the AAA-ATPase subunits responding to ATP hydrolysis. This collective motion of Rpt2 and Rpt6 results in an elevation of their pore loops, which could play an important role in substrate processing of proteasome. Our data also imply that the nucleotide occupancy pattern could be related to the activation status of the complex. Moreover, the HbYX tail insertion may not be sufficient to maintain the gate opening of 20S core particle. Our results provide new insights into the mechanisms of nucleotide-driven allosteric cooperativity of the complex and of the substrate processing by the proteasome.

TiO2was coated onto mesoporous silica SBA-15 by hydrolysis of tetrabutyl titanate to prepare 15 wt% TiO2@SBA-15 composites (15TS). The 15TS composites retain the mesostructure of the SBA-15 host, and TiO2was highly dispersed and uniformly coated. 5 wt% Pt nanoparticles supported on 15TS were employed for liquid-phase selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL). Compared with the Pt catalyst supported on pristine SBA-15, the Pt/15TS catalyst afforded higher activity and selectivity to COL. Furthermore, the modification of the Pt/15TS catalyst by FeOxcan greatly improve the activity and selectivity to COL. As a result, the Pt–FeOx/15TS catalyst displayed excellent selectivity to COL (around 84.5%) at nearly complete CAL conversion. Of particular note is that further calcination of the Pt–FeOx/15TS catalyst precursor in air at 773 K before reduction would greatly enhance the catalytic performance. Consequently, the TOF reached 3.06 s−1with a selectivity to COL of 86.4% over the Pt–FeOx/15TS-773 catalyst. Moreover, the Pt–FeOx/15TS-773 catalyst can also be reused about eight times without distinct loss in activity or selectivity. Based on characterization by XPS and H2-TPR, the important promotion effect of FeOxand strong metal–support interaction played key roles in preferential adsorption and activation of CO bonds in CAL.

This article shows an experimental validation of the volume conservation assumption (zero plastic volume change assumption) for aluminum alloy (AA6000) sheet metal. A series of tensile tests were conducted. During the tensile tests, an optimized digital image correlation setup was used to simultaneously measure three principal strain components. The experimental results show that, at locations outside the necking band, AA6000 strictly follows the zero plastic volume change assumption throughout the duration of the test. Inside the necking band, AA6000 follows the zero plastic volume change assumption in the elastic range and early plastic range. However, before failure, a visible volume strain increase can be found inside the necking band, which shows that, in the deep plastic zone, AA6000 does not always follow the volume conservation assumption. The experiment plan, measurement setup optimization, experimental results and data analysis are shown in detail.

Niacin, an age-old lipid-lowering drug, acts through the hydroxycarboxylic acid receptor 2 (HCAR2), a G protein-coupled receptor (GPCR). Yet, its use is hindered by side effects like skin flushing. To address this, specific HCAR2 agonists, like MK-6892 and GSK256073, with fewer adverse effects have been created. However, the activation mechanism of HCAR2 by niacin and these new agonists is not well understood. Here we present three cryo-electron microscopy structures of Gi-coupled HCAR2 bound to niacin, MK-6892, and GSK256073. Our findings reveal that different ligands induce varying binding pockets in HCAR2, influenced by aromatic amino acid cluster (W91ECL1, H1614.59, W1885.38, H1895.39and F1935.43) from receptor ECL1, TM4, and TM5. Additionally, conserved residues R1113.36and Y2847.43, unique to the HCA receptor family, likely initiate activation signal propagation in HCAR2. Together, this study offers insights into ligand recognition, receptor activation, and G protein coupling in HCAR2, paving the way for HCAR2-targeted drug development.

A new material's forming limit diagram (FLD) must be obtained before it can be used for stampings. Compared to conventional methods, the ISO method with a digital image correlation system provides an efficient way to conduct these tests. However the ISO method is position dependent, so the evaluation procedure for aluminum alloy will be seriously affected by the multiple necking strain distribution, resulting in much error. In this paper, a modified ISO method, which can be used for the evaluation of the aluminum alloy FLD, is proposed, and errors resulting from multiple necking were eliminated through detection of the major necking area. An FLD evaluation software was also programmed. An FLD0punch test was conducted to verify the new modified ISO method. Through comparison of the results with the accepted value, the FLD0value evaluated from the modified method was determined to be much more accurate than the standard method.

Pt nanoparticles entrapped in ordered mesoporous CMK-3 carbons with p6mm symmetry were prepared using a facile impregnation method, and the resulting materials were characterized using X-ray diffraction spectroscopy, N2adsorption-desorption, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The Pt nanoparticles were highly dispersed in the CMK-3 with 43.7% dispersion. The Pt/CMK-3 catalyst was an effective catalyst for the liquid-phase hydrogenation of nitrobenzene and its derivatives under the experimental conditions studied here. The Pt/CMK-3 catalyst was more active than commercial Pt/C catalyst in most cases. A highest turnover frequency of 43.8 s−1was measured when the Pt/CMK-3 catalyst was applied for the hydrogenation of 2-methyl-nitrobenzene in ethanol under optimal conditions. It is worthy of note that the Pt/CMK-3 catalyst could be recycled easily, and could be reused at least fourteen times without any loss in activity or selectivity for the hydrogenation of nitrobenzene in ethanol.

Double Parallel Joints coordinate measuring machine (CMM) is a new type coordinate measuring device with 9 structural parameters with accuracy difficult to be ensured just by processing and assembly. Calibration is needed to identify the structural parameters of the measuring machine. This article describes the calibration process of such a Double Parallel Joints CMM, and simulation was employed to analyze how the number of samples and angle measurement accuracy influence the measurement precision and calibration result during calibrating process. The conclusions are very instructive to precision design or error allocation and calibration process of the Double Parallel Joints CMM.

Osteocytes are mechanosensitive bone cells, but little is known about their effects on tumor cells in response to mechanical stimulation. We treated breast cancer cells with osteocyte-derived conditioned medium (CM) and fluid flow-treated conditioned medium (FFCM) with 0.25 Pa and 1 Pa shear stress. Notably, CM and FFCM at 0.25 Pa induced the mesenchymal-to-epithelial transition (MET), but FFCM at 1 Pa induced the epithelial-to-mesenchymal transition (EMT). This suggested that the effects of fluid flow on conditioned media depend on flow intensity. Fluorescence resonance energy transfer (FRET)-based evaluation of Src activity and vinculin molecular force showed that osteopontin was involved in EMT and MET switching. A mouse model of tumor-induced osteolysis was tested using dynamic tibia loadings of 1, 2, and 5 N. The low 1 N loading suppressed tumor-induced osteolysis, but this beneficial effect was lost and reversed with loads at 2 and 5 N, respectively. Changing the loading intensities in vivo also led to changes in serum TGFβ levels and the composition of tumor-associated volatile organic compounds in the urine. Collectively, this study demonstrated the critical role of intensity-dependent mechanotransduction and osteopontin in tumor-osteocyte communication, indicating that a biophysical factor can tangibly alter the behaviors of tumor cells in the bone microenvironment.

As a Ca2+-activated lipid scramblase and ion channel that mediates Ca2+influx, TMEM16F relies on both functions to facilitate extracellular vesicle generation, blood coagulation, and bone formation. How a bona fide ion channel scrambles lipids remains elusive. Our structural analyses revealed the coexistence of an intact channel pore and PIP2-dependent protein conformation changes leading to membrane distortion. Correlated to the extent of membrane distortion, many tightly bound lipids are slanted. Structure-based mutagenesis studies further reveal that neutralization of some lipid-binding residues or those near membrane distortion specifically alters the onset of lipid scrambling, but not Ca2+influx, thus identifying features outside of channel pore that are important for lipid scrambling. Together, our studies demonstrate that membrane distortion does not require open hydrophilic grooves facing the membrane interior and provide further evidence to suggest separate pathways for lipid scrambling and ion permeation.

Circulating cell-free tumor DNA (ctDNA) is a promising biomarker in cancer. Ultrasensitive technologies enable detection of low (< 0.1%) mutant allele frequencies, a pre-requisite to fully utilize the potential of ctDNA in cancer diagnostics. In addition, the entire liquid biopsy workflow needs to be carefully optimized to enable reliable ctDNA analysis. Here, we discuss important considerations for ctDNA detection in plasma. We show how each experimental step can easily be evaluated using simple quantitative PCR assays, including detection of cellular DNA contamination and PCR inhibition. Furthermore, ctDNA assay performance is also demonstrated to be affected by both DNA fragmentation and target sequence. Finally, we show that quantitative PCR is useful to estimate the required sequencing depth and to monitor DNA losses throughout the workflow. The use of quality control assays enables the development of robust and standardized workflows that facilitate the implementation of ctDNA analysis into clinical routine.