A convenient, fast and selective water analysis method is highly desirable in industrial and detection processes. Here a robust microporous Zn-MOF (metal-organic framework, Zn(hpi2cf)(DMF)(H
O)) is ...assembled from a dual-emissive H
hpi2cf (5-(2-(5-fluoro-2-hydroxyphenyl)-4,5-bis(4-fluorophenyl)-1H-imidazol-1-yl)isophthalic acid) ligand that exhibits characteristic excited state intramolecular proton transfer (ESIPT). This Zn-MOF contains amphipathic micropores (<3 Å) and undergoes extremely facile single-crystal-to-single-crystal transformation driven by reversible removal/uptake of coordinating water molecules simply stimulated by dry gas blowing or gentle heating at 70 °C, manifesting an excellent example of dynamic reversible coordination behaviour. The interconversion between the hydrated and dehydrated phases can turn the ligand ESIPT process on or off, resulting in sensitive two-colour photoluminescence switching over cycles. Therefore, this Zn-MOF represents an excellent PL water-sensing material, showing a fast (on the order of seconds) and highly selective response to water on a molecular level. Furthermore, paper or in situ grown ZnO-based sensing films have been fabricated and applied in humidity sensing (RH<1%), detection of traces of water (<0.05% v/v) in various organic solvents, thermal imaging and as a thermometer.
Carbon‐based single metal atom catalysts (SACs) are being extensively investigated to improve the kinetics of the Li–S redox reaction, which is greatly important for batteries with cell‐level energy ...densities >500 W h kg‐1. However, there are contradictory reports regarding the electrocatalytic activities of the different metal atoms and the role of the metal atom in LiS chemistry still remains unclear. This is due to the complex relationship between the catalytic behavior and the structure of carbon‐based SACs. Here, the catalytic behavior and active‐site geometry, oxidation state, and the electronic structure of different metal centers (Fe/Co/Ni) embedded in nitrogen‐doped graphene, and having similar physicochemical characteristics, are studied. Combining X‐ray absorption spectroscopy, density functional theory calculations, and electrochemical analysis, it is revealed that the coordination‐geometry and oxidation state of the metal atoms are modified when interacting with sulfur species. This interaction is strongly dependent on the hybridization of metal 3d and S p‐orbitals. A moderate hybridization with the Fermi level crossing the metal 3d band is more favorable for LiS redox reactions. This study thus provides a fundamental understanding of how metal atoms in SACs impact LiS redox behavior and offers new guidelines to develop highly active catalytic materials for high‐performance LiS batteries.
The critical role of single metal atoms is elucidated in LiS redox reactions. The coordination geometry and oxidation state of metal atoms strongly depend on the metal‐sulfur interaction. A moderate metal‐sulfur interaction, arising from the moderate hybridization of metal 3d and S p orbitals with the Fermi‐level crossing the metal 3d band, is more favorable for LiS redox reactions.
Absolute chiral environments are rare in regular polyhedral and prismatic architectures, but are achievable from self-assembly of metal-organic cages/containers (MOCs), which endow us with a ...promising ability to imitate natural organization systems to accomplish stereochemical recognition, catalysis and separation. Here we report a general assembly approach to homochiral MOCs with robust chemical viability suitable for various practical applications. A stepwise process for assembly of enantiopure ΔΔΔΔΔΔΔΔ- and ΛΛΛΛΛΛΛΛ-Pd6(RuL3)8 MOCs is accomplished by pre-resolution of the Δ/Λ-Ru-metalloligand precursors. The obtained Pd-Ru bimetallic MOCs feature in large D4-symmetric chiral space imposed by the predetermined Ru(II)-octahedral stereoconfigurations, which are substitutionally inert, stable, water-soluble and are capable of encapsulating a dozen guests per cage. Chiral resolution tests reveal diverse host-guest stereoselectivity towards different chiral molecules, which demonstrate enantioseparation ability for atropisomeric compounds with C2 symmetry. NMR studies indicate a distinctive resolution process depending on guest exchange dynamics, which is differentiable between host-guest diastereomers.
Total syntheses of shizukaols A and E Wu, Jian-Li; Lu, Yin-Suo; Tang, Bencan ...
Nature communications,
10/2018, Letnik:
9, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Shizukaols possess a common heptacyclic framework containing more than ten contiguous stereocenters and potential biological activities. Here we report that the total syntheses of shizukaols A (1) ...and E (2), two lindenane-type dimers from the Chloranthaceae family, are achieved via a modified biomimetic Diels-Alder reaction. The common crucial biomimetic diene 23 and ethylene species (6, 17) are obtained through either a highly Z-selective olefination of α-siloxy ketone with ynolate anions or an intramolecular Horner-Wadsworth-Emmons olefination from commercially available Wieland-Miescher ketone (7). This synthetic approach here opens up practical avenues for the total syntheses of the intriguing Chloranthaceae family members, as well as the understanding of their relevant biological action in nature.
The design of functional metalloenzymes is attractive, but few designs can exceed the catalytic rate of native enzymes. In order to create an effective artificial dehaloperoxidase (DHP), we ...redesigned the heme center of myoglobin (Mb) by introducing a distal Tyr43 and replacing the distal His64 with an Asp, which combines the structural features of chloroperoxidase (a distal Asp) with DHP (a distal Tyr). The rationally designed F43Y/H64D Mb was shown to exhibit a remarkable dehalogenation activity, with a catalytic efficiency more than 1000-fold higher than that of a native DHP from A. ornata. To the best of our knowledge, this is the highest activity reported to date for an artificial DHP. Moreover, X-ray structures of F43Y/H64D Mb and in complex with a typical substrate, 2,4,6-trichlorophenol (TCP), revealed a distal substrate binding site and crucial roles of both distal Tyr43 and Asp64. This study not only provides insights into the structure and function relationship of native and artificial DHPs but also suggests potential applications in bioremediation of toxic halophenols.
Protein design is able to create artificial proteins with advanced functions, and computer simulation plays a key role in guiding the rational design. In the absence of structural evidence for ...cytoglobin (Cgb) with an intramolecular disulfide bond, we recently designed a de novo disulfide bond in myoglobin (Mb) based on structural alignment (i.e., V21C/V66C Mb double mutant). To provide deep insight into the regulation role of the Cys21-Cys66 disulfide bond, we herein perform molecular dynamics (MD) simulation of the fluoride-protein complex by using a fluoride ion as a probe, which reveals detailed interactions of the fluoride ion in the heme distal pocket, involving both the distal His64 and water molecules. Moreover, we determined the kinetic parameters of fluoride binding to the double mutant. The results agree with the MD simulation and show that the formation of the Cys21-Cys66 disulfide bond facilitates both fluoride binding to and dissociating from the heme iron. Therefore, the combination of theoretical and experimental studies provides valuable information for understanding the structure and function of heme proteins, as regulated by a disulfide bond. This study is thus able to guide the rational design of artificial proteins with tunable functions in the future.
Mutations in the proline-rich transmembrane protein 2 （PRRT2） are associated with paroxysmal kinesigenic dys- kinesia （PKD） and several other paroxysmal neurological diseases, but the PRRT2 function ...and pathogenic mecha- nisms remain largely obscure. Here we show that PRRT2 is a presynaptic protein that interacts with components of the SNARE complex and downregulates its formation. Loss-of-function mutant mice showed PKD-like phenotypes triggered by generalized seizures, hyperthermia, or optogenetic stimulation of the cerebellum. Mutant mice with spe- cific PRRT2 deletion in cerebellar granule cells （GCs） recapitulate the behavioral phenotypes seen in Prrt2-null mice. Furthermore, recording made in cerebellar slices showed that optogenetic stimulation of GCs results in transient elevation followed by suppression of Purkinje cell firing. The anticonvulsant drug carbamazepine used in PKD treat- ment also relieved PKD-like behaviors in mutant mice. Together, our findings identify PRRT2 as a novel regulator of the SNARE complex and provide a circuit mechanism underlying the PRRT2-related behaviors.
In this article, a novel high-efficiency harmonic beamforming technique based on time-modulated arrays (TMAs) with multistate time modulators is proposed. The typical single-sideband TMAs suppress ...the image harmonic components in the radio frequency (RF) channel, which means low power conversion efficiency, large power consumption, and a major heat dissipation problem. To circumvent these constraints, we present a novel phase modulation (PM) waveform with a linear phase that can be easily constructed using multiple fixed delay lines and a pair of single-pole-multi-throw (SPMT) RF switches. This fundamental PM waveform enables the creation of uniform radiation patterns. Furthermore, two complementary methodologies are proposed for synthesizing more advanced radiation patterns that need nonuniform array weights. One method is to change the linear phase slope of PM waveforms that exhibit sideband radiation but have 100% feeding network efficiency. The other option is to investigate hybrid amplitude and PM (HAPM) waveforms, which suffer from inefficiencies in the feeding network but do not exhibit sideband radiation. Besides, the comprehensive efficiency evaluation formulas have been effectively derived. Simulations have been done to verify its effectiveness.
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•S-doped Ni Co layered double hydroxide and PPy nanotubes (NiCo-LDH-S/PNTs) was made.•Zeolitic imidazolate framework-67 give Co and template of sheet-assembled ...polyhedron.•NiCo-LDH-S/PNTs shows the highest specific capacitance (CF) of 1936.3F/g at 10 mV/s.•Battery supercapacitor hybrid shows maximum energy density of 16.3 Wh/kg at 650 W/kg.•The CF retention of 74% and Coulombic efficiency of 90% are got after 8,000 cycles.
Nickel and cobalt layered double hydroxide (NiCo-LDH) has large specific surface area and interlayer spacing, multiple redox states and high ion-exchange capability, but poor electrical conductivity, severe agglomerations and structural defect restrict energy storage ability of NiCo-LDH as active materiel of battery supercapacitor hybrids (BSH). In this study, it is the first time to design sulfur-doped NiCo-LDH and polypyrrole nanotubes composites (NiCo-LDH-S/PNTs) from zeolitic imidazolate framework-67 (ZIF-67) as the efficient active material of BSH using electrospinning and hydrothermal processes. Effects of sulfur doping amounts are investigated. The one-dimensional hollow polypyrrole decorated with NiCo-LDH-S sheets with high aspect ratio provides straight charge-transfer routes and abundant contacts with electrolyte. The highest specific capacitance (CF) of 1936.3 F/g (specific capacity of 322.8 mAh/g) is achieved for the NiCo-LDH-S/PNTs with sulfur doping amount of 7% at 10 mV/s. The BSH comprising graphene LDH negative electrode and NiCo-LDH-S/PNTs positive electrode shows the maximum energy density of 16.28 Wh/kg at 650 W/kg. The CF retention of 74% and Coulombic efficiency of 90% are also achieved after 8000 charge/discharge cycles.
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Experimental evidence has shown that per- and polyfluoroalkyl substances (PFAS) alternatives and mixtures may exert hepatotoxic effects in animals. However, epidemiological evidence ...is limited. This research aimed to explore associations of PFAS and the alternatives with liver function in a general adult population. The study participants consisted of 1,303 adults from a community-based cross-sectional investigation in Guangzhou, China, from November 2018 to August 2019. We selected 13 PFAS with detection rates > 85% in serum samples and focused on perfluorooctane-sulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and their alternatives 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA), 8:2 Cl-PFESA, and perfluorohexanoic acid (PFHxA) as predictors of outcome. Six liver function biomarkers (ALB, ALT, AST, GGT, ALP, and DBIL) were chosen as outcomes. We applied regression models with restricted cubic spline function to explore correlations between single PFAS and liver function and inspected the combined effect of PFAS mixtures on liver by applying Bayesian kernel machine regression (BKMR). We discovered positive associations among PFAS and liver function biomarkers except for ALP. For example, compared with the 25th percentile of PFAS concentration, the level of ALT increased by 12.36% (95% CI: 7.91%, 16.98%) for ln-6:2 Cl-PFESA, 5.59% (95% CI: 2.35%, 8.92%) for ln-8:2 Cl-PFESA, 3.56% (95% CI: −0.39%, 7.68%) for ln-PFHxA, 13.91% (95% CI: 8.93%, 19.13%) for ln-PFOA, and 14.25% (95% CI: 9.91%, 18.77%) for ln-PFOS at their 75th percentile. In addition, higher exposed serum PFAS was found to be correlated with greater odds of abnormal liver function. Analysis from BKMR models also showed an adverse association between PFAS mixtures and liver function. The combined effect of the PFAS mixture appeared to be non-interactive, in which PFOS was the main contributor to the overall effect. Our findings provide evidence of associations between PFAS alternatives, PFAS mixtures, and liver function in the general adult population.
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