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The human MT 1 and MT 2 melatonin receptors 1 , 2 are G-protein-coupled receptors (GPCRs) that help to regulate circadian rhythm and sleep patterns 3 . Drug development efforts have targeted both receptors for the treatment of insomnia, circadian rhythm and mood disorders, and cancer 3 , and MT 2 has also been implicated in type 2 diabetes 4 , 5 . Here we report X-ray free electron laser (XFEL) structures of the human MT 2 receptor in complex with the agonists 2-phenylmelatonin (2-PMT) and ramelteon 6 at resolutions of 2.8 Å and 3.3 Å, respectively, along with two structures of function-related mutants: H208 5.46 A (superscripts represent the Ballesteros–Weinstein residue numbering nomenclature 7 ) and N86 2.50 D, obtained in complex with 2-PMT. Comparison of the structures of MT 2 with a published structure 8 of MT 1 reveals that, despite conservation of the orthosteric ligand-binding site residues, there are notable conformational variations as well as differences in [ 3 H]melatonin dissociation kinetics that provide insights into the selectivity between melatonin receptor subtypes. A membrane-buried lateral ligand entry channel is observed in both MT 1 and MT 2 , but in addition the MT 2 structures reveal a narrow opening towards the solvent in the extracellular part of the receptor. We provide functional and kinetic data that support a prominent role for intramembrane ligand entry in both receptors, and suggest that there might also be an extracellular entry path in MT 2 . Our findings contribute to a molecular understanding of melatonin receptor subtype selectivity and ligand access modes, which are essential for the design of highly selective melatonin tool compounds and therapeutic agents. Structural and functional studies show that the MT 2 melatonin receptor, unlike the MT 1 receptor, contains an extracellular opening for ligand entry, shedding light on receptor subtype specificity.

A glassy carbon electrode (GCE) modified with poly(sulfosalicylic acid) (PSA) and poly(diallyldimethylammonium chloride)-graphene (PDDA-GN) was prepared by a simple self-assembly method. The formation of films was ascribed to the electrostatic force between negatively charged PSA and positively charged PDDA-GN as well as the π–π stacking interaction between PSA and PDDA-GN. The as prepared films were characterized by scanning electron microscopy (SEM), Raman spectroscopy and electrochemical methods. Under the optimized condition, the modified GCE showed two well-defined redox waves for catechol (CT) and hydroquinone (HQ) in cyclic voltammetry (CV) with a peak potential separation of 111 mV, which ensured the anti-interference ability of the electrochemical sensor and made simultaneous determination of dihydroxybenzene isomers possible in real samples. The corresponding oxidation currents increased remarkably compared with those obtained at the bare GCE, PSA/GCE and PDDA-GN/GCE, respectively. Differential pulse voltammetry (DPV) was used for the simultaneous determination of CT and HQ. The anodic peak current of CT was linear in the concentration from 1 × 10−6 to 4 × 10−4 M in the presence of 3 × 10−5 M HQ, and the detection limit was 2.2 × 10−7 M (S/N = 3). At the same time, the anodic peak current of HQ was linear in the concentration from 2 × 10−6 to 4 × 10−4 M in the presence of 2 × 10−5 M CT, and the detection limit was 3.9 × 10−7 M (S/N = 3). The proposed method was applied to simultaneous determination of CT and HQ in tap water with satisfactory results. These results indicated that PSA/PDDA-GN is a promising modified material with great potential in electrocatalysis and electrochemical sensing.

The human MT and MT melatonin receptors are G-protein-coupled receptors (GPCRs) that help to regulate circadian rhythm and sleep patterns . Drug development efforts have targeted both receptors for the treatment of insomnia, circadian rhythm and mood disorders, and cancer , and MT has also been implicated in type 2 diabetes . Here we report X-ray free electron laser (XFEL) structures of the human MT receptor in complex with the agonists 2-phenylmelatonin (2-PMT) and ramelteon at resolutions of 2.8 Å and 3.3 Å, respectively, along with two structures of function-related mutants: H208 A (superscripts represent the Ballesteros-Weinstein residue numbering nomenclature ) and N86 D, obtained in complex with 2-PMT. Comparison of the structures of MT with a published structure of MT reveals that, despite conservation of the orthosteric ligand-binding site residues, there are notable conformational variations as well as differences in [ H]melatonin dissociation kinetics that provide insights into the selectivity between melatonin receptor subtypes. A membrane-buried lateral ligand entry channel is observed in both MT and MT , but in addition the MT structures reveal a narrow opening towards the solvent in the extracellular part of the receptor. We provide functional and kinetic data that support a prominent role for intramembrane ligand entry in both receptors, and suggest that there might also be an extracellular entry path in MT . Our findings contribute to a molecular understanding of melatonin receptor subtype selectivity and ligand access modes, which are essential for the design of highly selective melatonin tool compounds and therapeutic agents.

In this paper, a new type of anionic surfactant containing four carboxylates was synthesized by a four-step synthetic reaction including bromination reaction and primary amide protective reaction. Intermediates and final products of each step in the whole synthetic process were characterized by 1H NMR and MS. Purification of the anionic surfactant was accomplished through combination of recrystallization and silica gel column chromatography. The structure and the critical micelle concentration (CMC) of this surfactant at different temperatures were also investigated. Unlike traditional monocarboxylate surfactant easy to form lamellar mesostructure, this surfactant has the hexagonal mesophase structure and comparatively low CMC, hopefully to be applied in the preparation of mesoporous metal oxides.

Control of vehicle platoon can effectively reduce the traffic accidents caused by fatigue driving and misoperation, reduce air resistance by eliminating the inter-vehicle gap which will effectively reduce fuel consumption and exhaust emissions. A hierarchical control scheme for vehicle platoons is proposed in this paper. Considering safety, consistency, and passengers’ comfort, a synchronous distributed model predictive controller is designed as an upper-level controller, in which a constraint guaranteeing string stability is introduced into the involved local optimization problem so as to guarantee that the inter-vehicle gap error gradually attenuates as it propagates downstream. A terminal equality constraint is added to guarantee asymptotic consensus of vehicle platoons. By constructing the vehicle inverse longitudinal dynamics model, a lower-level control scheme with feedforward and feedback controllers is designed to adjust the throttle angle and brake pressure of vehicles. A PID is used as the feedback controller to eliminate the influence of unmodeled dynamics and uncertainties. Finally, the performance of longitudinal tracking with the proposed control scheme is validated by joint simulations with PreScan, CarSim, and Simulink.

The activation properties of ammonium oxalate on the flotation of pyrite and arsenopyrite in the lime system were studied in this work. Single mineral flotation tests showed that the ammonium oxalate strongly activated pyrite in high alkalinity and high Ca 2+ system, whereas arsenopyrite was almost unaffected. In mineral mixtures tests, the recovery difference between pyrite and arsenopyrite after adding ammonium oxalate is more than 85%. After ammonium oxalate and ethyl xanthate treatment, the hydrophobicity of pyrite increased significantly, and the contact angle increased from 66.62° to 75.15° and then to 81.21°. After ammonium oxalate treatment, the amount of ethyl xanthate adsorption on the pyrite surface significantly increased and was much greater than that on the arsenopyrite surface. Zeta potential measurements showed that after activation by ammonium oxalate, there was a shift in the zeta potential of pyrite to more negative values by adding xanthate. X-ray photoelectron spectroscopy test showed that after ammonium oxalate treatment, the O 1s content on the surface of pyrite decreased from 44.03% to 26.18%, and the S 2p content increased from 14.01% to 27.26%, which confirmed that the ammonium oxalate-treated pyrite surface was more hydrophobic than the untreated surface. Therefore, ammonium oxalate may be used as a selective activator of pyrite in the lime system, which achieves an efficient flotation separation of S—As sulfide ores under high alkalinity and high Ca 2+ concentration conditions.

Lodging is one of the major constraints that threaten crop productivity. Although the relationship between cell walls and straw strength has been well recognized, little relevant research has been done in wheat, particularly on the monomer composition and structural characteristics of cell wall polymers and the arrangement of vascular bundles. In this study, we systematically investigated cell wall- and straw-related traits in a range of wheat germplasm resources and culm mutants using a high-throughput platform for cell wall analysis. We found that varieties with higher breaking force exhibited higher levels of crystalline cellulose but fewer hemicellulose components than other varieties. The lignin content was not consistent with the breaking force; instead, the lignin monomer constitution might be important because a significantly higher proportion of p-hydroxyphenyl (H) and guaiacyl (G) but a lower proportion of syringyl (S) monomers of lignin was found in the higher breaking force group. The crystallinity detected by X-ray diffraction was positively correlated with breaking force, indicating that the physical/chemical properties of polysaccharides also deserve attention. In terms of anatomical characteristics, the varieties with higher breaking force had a lower number and area of smaller vascular bundles in the peripheral sclerenchyma than other varieties. These results, together with the finding of a highly significant correlation between stem breaking force and straw fresh weight, 2nd internode width, flag leaf width and SiO2 content, should provide systematic information for breeding for lodging resistance. Graphic abstract

Graphene/silicon Schottky junctions have been proven efficient for photodetection, but the existing high dark current seriously restricts applications such as weak signal detection. In this paper, a thin layer of gadolinium iron garnet (Gd3Fe5O12, GdIG) film is introduced to engineer the interface of a graphene/silicon Schottky photodetector. The novel structure shows a significant decrease in dark current by 54 times at a −2 V bias. It also exhibits high performance in a self-powered mode in terms of an Ilight/Idark ratio up to 8.2 × 106 and a specific detectivity of 1.35 × 1013 Jones at 633 nm, showing appealing potential for weak-light detection. Practical suitability characterizations reveal a broadband absorption covering ultraviolet to near-infrared light and a large linear response with a wide range of light intensities. The device holds an operation speed of 0.15 ms, a stable response for 500 continuous working cycles, and long-term environmental stability after several months. Theoretical analysis shows that the interlayer increases the barrier height and passivates the contact surface so that the dark current is suppressed. This work demonstrates the good capacity of GdIG thin films as interlayer materials and provides a new solution for high-performance photodetectors.

As a result of antibiotic overuse, bacterial antibiotic resistance has become a severe threat to worldwide public health. The development of more effective antimicrobial therapies and alternative antibiotic strategies is urgently required. The role played by bacterial membrane vesicles (BMVs) in antibiotic resistance has become a current focus of research. BMVs are nanoparticles derived from the membrane components of Gram-negative and Gram-positive bacteria and contain diverse components originating from the cell envelope and cytoplasm. Antibiotic stress stimulates the secretion of BMVs. BMVs promote and mediate antibiotic resistance by multiple mechanisms. BMVs have been investigated as conceptually new antibiotics and drug-delivery vehicles. In this article, we outline the research related to BMVs and antibiotic resistance as a reference for the intentional use of BMVs to combat antibiotic resistance.