Tuning Electrocatalytic Water Oxidation Activity: Insights from the Active-Site Distance in LnCu6 Clusters.

Atomically precise metal clusters serve as a unique model for unraveling the intricate mechanism of the catalytic reaction and exploring the complex relationship between structure and activity. Herein, three series of water-soluble heterometallic clusters LnCu6, abbreviated as LnCu6-AC (Ln = La, Nd, Gd, Er, Yb; HAC = acetic acid), LnCu6-IM (Ln = La and Nd; IM = Imidazole), and LnCu6-IDA (Ln = Nd; H2IDA = Iminodiacetic acid) are presented, each featuring a uniform metallic core stabilized by distinct protected ligands. Crystal structure analysis reveals a triangular prism topology formed by six Cu2+ ions around one Ln3+ ion in LnCu6, with variations in Cu···Cu distances attributed to different ligands. Electrocatalytic oxygen evolution reaction (OER) shows that these different LnCu6 clusters exhibit different OER activities with remarkable turnover frequency of 135 s-1 for NdCu6-AC, 79 s-1 for NdCu6-IM and 32 s-1 for NdCu6-IDA. Structural analysis and Density Functional Theory (DFT) calculations underscore the correlation between shorter Cu···Cu distances and improves OER catalytic activity, emphasizing the pivotal role of active-site distance in regulating electrocatalytic OER activities. These results provide valuable insights into the OER mechanism and contribute to the design of efficient homogeneous OER electrocatalysts.

Metal-support spin orders: Crucial effect on electrocatalytic oxygen reduction.

Magnetic property (e.g. spin order) of support is of great importance in the rational design of heterogeneous catalysts. Herein, we have taken the Ni-supported ferromagnetic (FM) CrBr3 support (Nix/CrBr3) to thoroughly investigate the effect of spin-order on electrocatalytic oxygen reduction reaction (ORR) via spin-polarized density functional theory calculations. Specifically, Ni loading induces anti-FM coupling in Ni-Cr, leading to a transition from FM-to-ferrimagnetic (FIM) properties, while Ni-Ni metallic bonds create a robust FM direct exchange, benefiting the improvement of the phase transition temperature. Interestingly, with the increase in Ni loading, the easy magnetic axis changes from out-of-plane (2D-Heisenberg) to in-plane (2D-XY). The adsorption properties of Nix/CrBr3, involving O2 adsorption energy and configuration, are not governed by the d-band center but strongly correlate with magnetic anisotropy. It is noteworthy that the applied potential and electrolyte acidity triggers spin-order transition phenomena during the ORR and induces the catalytic pathway change from 4e- ORR to 2e- ORR with the excellent onset potential of 0.93 V/reversible hydrogen electrode, comparable to the existing most excellent noble-metal catalysts. Generally, these findings offer new avenues to understand and design heterogeneous catalysts with magnetic support.

Co-Dissolved Isostructural Polyoxovanadates to Construct Single-Atom-Site Catalysts for Efficient CO2 Photoreduction.

We explored a co-dissolved strategy to embed mono-dispersed Pt center into V2 O5 support via dissolving [PtV9 O28 ]7- into [V10 O28 ]6- aqueous solution. The uniform dispersion of [PtV9 O28 ]7- in [V10 O28 ]6- solution allows [PtV9 O28 ]7- to be surrounded by [V10 O28 ]6- clusters via a freeze-drying process. The V centers in both [PtV9 O28 ]7- and [V10 O28 ]6- were converted into V2 O5 via a calcination process to stabilize Pt center. These double separations can effectively prevent the Pt center agglomeration during the high-temperature conversion process, and achieve 100 % utilization of Pt in [PtV9 O28 ]7- . The resulting Pt-V2 O5 single-atom-site catalysts exhibit a CH4 yield of 247.6 µmol g-1 h-1 , 25 times higher than that of Pt nanoparticle on the V2 O5 support, which was accompanied by the lactic acid photooxidation to form pyruvic acid. Systematical investigations on this unambiguous structure demonstrate an important role of Pt-O atomic pair synergy for highly efficient CO2 photoreduction.

Dual effect of the coordination field and sulphuric acid on the properties of a single-atom catalyst in the electrosynthesis of H2O2.

Electrocatalytic synthesis of hydrogen peroxide (H2O2) via the two-electron oxygen reduction reaction (2e- ORR) is the ideal solution for on-site H2O2 production. Herein, we propose a new strategy for creating new 2e- ORR catalysts by introducing electron-deficient B atoms and electron-rich N atoms to regulate the coordination field of metal ions on a graphene substrate. Through the first-principles density functional theory (DFT) calculations, NiN2B2-h was screened out as it had a low overpotential (0.12 V) for 2e- ORR. The Bader charge analysis revealed that B atoms increased the charge density of Ni atoms, leading to moderate binding of O2. Furthermore, the combination of ab initio molecular dynamic (AIMD) calculations and DFT calculations in an H2SO4 environment revealed a new reaction mechanism of H2O2 synthesis, involving proton-transfer between activated O2 and HSO4-. Moreover, the rate-determining step (0.63 eV) of H2O2 desorption in the presence of H2SO4 was different from that of OOH* protonation (0.45 eV) under the gas phase. This difference is attributed to the hydrogen-bond network in the acid solution.

Axially Coordinated Gold Nanoclusters Tailoring Fe-N-C Nanozymes for Enhanced Oxidase-Like Specificity and Activity.

Metal-organic frameworks (MOF) derived nitrogen-doped carbon-supported monodisperse Fe (Fe-N-C) catalysts are intensively studied, but great challenges remain in understanding the relationship between the coordination structure and the performance of Fe-N-C nanozymes. Herein, a novel nanocluster ligand-bridging strategy is proposed for constructing Fe-S1 N4 structures with axially coordinated S and Au nanoclusters on ZIF-8 derived Fe-N-C (labeled Aux /Fe-S1 N4 -C). The axial Au nanoclusters facilitate electron transfer to Fe active sites, utilizing the bridging ligand S as a medium, thereby enhancing the oxygen adsorption capacity of composite nanozymes. Compared to Fe-N-C, Aux /Fe-S1 N4 -C exhibits high oxidase-like specificity and activity, and holds great potential for detecting acetylcholinesterase activity with a detection limit of 5.1 µU mL-1 , surpassing most reported nanozymes.

Visible-Light Photocatalytic Overall Water Splitting on a B4C3/CxNy Z-Scheme Heterojunction: Role of Ultrafast Carrier Recombination-Transfer Kinetics.

Herein, combining density functional theory (DFT) calculations with nonadiabatic molecular dynamics (NAMD), we built a computational framework to rationally screen from a series of 2D conjugated carbon nitrides (CNs) to match with B4C3, resulting in the excellent direct Z-scheme photocatalyst (B4C3/C6N6) for overall water splitting (OWS). Studies on interface engineering and ultrafast dynamics of carrier recombination-transfer show that in the B4C3/C6N6 system, compared with the slower interlayer migration process of carriers, strong nonadiabatic coupling and longer quantum decoherence time accelerates weak carrier interlayer recombination on a subpicosecond time scale, enabling simultaneous triggering of hydrogen evolution reaction (HER) with ΔG = -0.23 eV and spontaneous oxygen evolution reaction (OER) in the absence of sacrificial or cocatalysts. In general, our work will promote the design of efficient direct Z-scheme photocatalysts from an ultrafast dynamics perspective.

Preparation of novel diperylene-cored polyimide photocatalyst with broad-spectra response and high stability.

A novel polyimide (PI) with broad-spectra response, high photocatalytic activity and stability under super acidic conditions (pH = 0) was synthesized via polymerizing method. Two types of perylene-cored materials (PDIAN and PTCDA) with anhydride and diamine respectively, were applied as precursors for PI polymerization. The as-prepared PI was optimized at 1:1 initial molar ratio of PDIAN to PTCDA. Using common PI (synthesized from melamine and pyromellitic dianhydride) as comparison, the Cr(VI) reduction rate was boosted from 25.4% to 96.6% within 120 min light irradiation. The corresponding rate constant by PI(PDIAN/PTCDA) was estimated to be ca. 11.7 times relative to that by common PI. The boosted performance was ascribed to the strong π-π conjugation from diperylene cores, which can decrease the photoluminescence intensity and electrochemical impedance, so as to promote the separation and transfer of photogenerated electron-hole pairs. In addition, the optimized PI(PDIAN/PTCDA) displayed wide-spectra response, which can still work under 730 nm light. The influencing factors toward Cr(VI) reduction were also clarified to be beneficial at lower pH and increased concentration of hole scavenger. After five cycles at pH 0, the PI still maintained excellent redox activity and structural stability.

Cooperatively interface role of surface atoms and aqueous media on single atom catalytic property for H2O2 synthesis.

Direct electrosynthesis of hydrogen peroxide (H2O2) from H2 and O2 is a promising alternative to currently industrial Riedl-Pfleiderer route. Utilizing a combination of density functional theory (DFT) and ab-initio-molecular dynamic simulation (AIMD), we presented an effective computational framework to identify the cooperative role of surface atoms(e.g. O, N and S) and aqueous media on catalytic performance of single-atom catalysts (SACs) supported Nb2C MXenes. Computational results shown that both Ni/Nb2CN2 and Co/Nb2CS2 have low overpotentials of 0.17 V and 0.20 V, and the barrier of 0.89 eV and 0.67 eV for 2e- ORR under gas phase, respectively, while in aqueous phase, hydrogen bond framework on the surface promotes the transfer of proton, resulting in the lower 2e- ORR overpotential (0.05 V) in Co/Nb2CS2 and lower barrier (almost 0.01 eV) for rate-determining step (RDS) in Ni/Nb2CN2. Electronically, we found that the less-electronegativity N and S relative to O more benefit to mediate the activation degree of O2 on SACs and thereby improve catalytic selectivity. Thus, it is concluded that both surface atom and aqueous medium synergistically promote catalytic property for H2O2 synthesis.

Aqueous Preparation of Maillard Reaction Intermediate from Glutathione and Xylose and its Volatile Formation During Thermal Treatment.

Maillard reaction intermediate (MGX) generated from glutathione and xylose in aqueous medium was prepared via the Maillard reaction performed under a two-stage temperature increase process. The purified MGX was identified by Fourier-transform infrared spectroscopy, mass spectrometry, and nuclear magnetic resonance as N-(1-deoxy-d-xylulos-1-yl)-glutathione (Amadori compound, C15 H25 O10 N3 S) with five main isomers. The method of Maillard reaction performed under a two-stage temperature increase process was further verified by high-performance liquid chromatography. The optimal reaction time and temperature for the preparation of MGX was determined as 60 min at 90 °C. The yield of MGX was increased from 8.60% to 55.52% through thermal reaction coupled with vacuum dehydration. In addition, rapid and more Maillard-type volatile compounds were formed in MGX during thermal treatment than that in Maillard reaction products or glutathione-xylose mixture. Beside, MGX possessed more pleasing meat-like volatile profile compared with the Amadori compound of glutamic acid-xylose (AAX), cysteine-xylose (ACX), and glycine-xylose (AGX). Therefore, it suggested that the MGX had the potential to achieve a better flavor formation during thermal treatment. PRACTICAL APPLICATION: Maillard reaction intermediates, such as Amadori or Heyns rearrangement products (ARP or HRP), are important flavor precursors, which possess stable physicochemical properties, but tend to degrade into flavor compounds at high temperatures. Maillard reaction intermediate from glutathione and xylose acts as primary flavor enhancers to complete Maillard reaction to produce flavors in the subsequent thermal processing, which can significantly improve and stabilize the flavor quality of the meaty food, and deserves a very broad application prospects. The new developed method will be a significant theoretical basis on research preparation and properties of Maillard reaction intermediates in complex food systems.

Causes of misdiagnosis in assessing tubal patency by transvaginal real-time three-dimensional hysterosalpingo-contrast sonography.

OBJECTIVE: This study aims to investigate the causes of misdiagnosis in assessing tubal patency by transvaginal real-time three-dimensional hysterosalpingo-contrast sonography (TVS RT-3D-HyCoSy), in order to improve the diagnostic efficiency of TVS RT-3D-HyCoSy. METHODS: A total of 162 oviducts of 83 infertility patients were examined by TVS RT-3D-HyCoSy. These results were compared with the gold standard for laparoscopic dye studies, and the misdiagnosed cases were analyzed. RESULTS: TVS RT-3D-HyCoSy revealed that 68 oviducts were unobstructed and 94 obstructed. The results for the 144 oviducts were in line with the gold standard, while those for 18 oviducts were not. The accuracy rate of the TVS RT-3D-HyCoSy was 88.9%, and the misdiagnosis rate was 11.1%. The main causes of misdiagnosis included contrast medium countercurrent and diffusion, oviduct spasm, abnormal shape or position of the oviduct, pelvic adhesion, and poor imaging operation. CONCLUSION: TVS RT-3D-HyCoSy can well-evaluate tubal patency, and understand and improve the cause of misdiagnosis. Furthermore, the diagnostic efficiency of TVS RT-3D-HyCoSy can still be further improved.

Preparation of N-(1-Deoxy-Α-D-Xylulos-1-Yl)-Glutamic Acid via Aqueous Maillard Reaction Coupled with Vacuum Dehydration and Its Flavor Formation Through Thermal Treatment of Baking Process.

Amadori rearrangement product (ARP) derived from glutamic acid (Glu) and xylose (Xyl) was prepared by aqueous Maillard reaction. Subsequently, ion exchange chromatography, MS, and NMR were used for purification and identification, confirming that the molecular formula of ARP was C10 H17 NO8 , namely N-(1-deoxy-α-D-xylulos-1-yl)-glutamic acid, with a molecular mass of 279 Da. To improve the aqueous yield of ARP, a thermal reaction coupled with vacuum dehydration was used and the yield of ARP was increased from 2.07% to 75.11%. Furthermore, flavor formation capacity of ARP by a thermal treatment simulated to a baking process was compared with Maillard reaction products, Maillard-dehydration reaction products, and Glu-Xyl mixture. The results indicated that a larger amount of volatile flavor compounds and a biscuit-like, burnt aroma was generated rapidly from the mixture of ARP and unreacted Glu-Xyl, which could be a potential flavor enhancer for baked foods. PRACTICAL APPLICATION: Maillard reaction performed in aqueous medium through thermal reaction combined with vacuum dehydration is a novel and practical technology that could be widely used to produce Maillard reaction intermediates (MRIs), such as Amadori or Heyns rearrangement products, which are regarded as significant nonvolatile aroma precursors and have stable physical and chemical properties compared with Maillard reaction products (MRPs). MRI derived from glutamic acid and xylose is a potential substitute of MRPs for flavorings preparation and shows a great capacity to generate fresh flavors in a short time at high temperature, which meets the requirements of baking foods. Therefore, the new developed method could be a promising tool for MRI preparation and application in food and flavoring industries.

N-(1-Deoxy-d-xylulos-1-yl)-glutathione: A Maillard Reaction Intermediate Predominating in Aqueous Glutathione-Xylose Systems by Simultaneous Dehydration-Reaction.

The effect of simultaneous dehydration-reaction (SDR) on Amadori rearrangement product (ARP) N-(1-deoxy-d-xylulos-1-yl)-glutathione and its key degradation products, 3-deoxyxylosone (3-DX) and 1-deoxyxylosone (1-DX), were investigated in an aqueous glutathione-xylose (GSH-Xyl) system. The yield of ARP was increased to 67.98% by SDR compared with 8.44% by atmospheric thermal reaction at 80 °C. Reaction kinetics was applied to analyze the mechanism and characteristics of ARP formation and degradation under SDR. ARP formation and degradation rate was highly dependent on temperature, and the latter was more sensitive to temperature. By regulating the reaction conditions of temperature and pH, the ratio of ARP formation rate constant to its degradation rate constant could be controlled to achieve an efficient preparation of ARP from GSH-Xyl Maillard reaction through SDR.

MicroRNA-300 suppresses metastasis of oral squamous cell carcinoma by inhibiting epithelial-to-mesenchymal transition.

INTRODUCTION: Oral cancer is the sixth most prevalent form of cancer, with oral squamous cell carcinomas (OSCCs) exhibiting the highest morbidity of all head and neck cancers. However, the specific metastatic mechanism is not yet clear. MicroR-300 (miR-300) has been identified as a critical regulator in tumor development. In this study, we focused on the roles of miR-300 in regulating epithelial-mesenchymal transition (EMT) in OSCC. METHODS: The surgical specimens from cases of OSCC (N=120) were collected, and the miR-300 expression was tested and the results were analyzed for possible correlations with clinical characteristics, and the prognostic significance was assessed by Kaplan-Meier analysis and Cox proportional hazards regression in OSCC patients. In addition, the proliferation and invasion of OSCC cells were evaluated after transfection of miR-300 mimics or inhibitor. At last, the role of miR-300 in EMT was investigated. RESULTS: The results showed that miR-300 levels were significantly lower in patients with OSCC than in controls and miR-300 levels in patients with OSCC were significantly associated with TNM classification. Kaplan-Meier analysis indicated that miR-300 with lower level had significantly decreased overall survival and disease-free survival of OSCC patients. In multivariate analysis, TNM stage, miR-300 expression and tobacco usage were the independent prognostic factors for overall survival and disease-free survival in OSCC. Moreover, in vitro experiments showed that miR-300 could inhibit the proliferation and invasion of OSCC cells. More importantly, miR-300 could inhibit the EMT process. In addition, we found that ET-1 could inhibit the expression of miR-300. CONCLUSION: Our findings indicated that miR-300 could suppress metastasis of OSCC by inhibiting EMT. The present study indicates that miR-300 is a potential therapeutic agent for OSCC.

SIRT1 acts as a potential tumor suppressor in oral squamous cell carcinoma.

BACKGROUND: Oral squamous cell carcinoma (OSCC) is the most common malignant tumor in oral cancer, however, the mechanism underlying OSCC tumorigenesis is unknown. SIRT1, has been considered a prominent tumor-suppressing/promoting gene in various solid tumors, although the precise role of SIRT1 in OSCC progression remains unknown. METHODS: SIRT1 expression was assessed in surgically resected specimens from patients with OSCC for histopathologic factors. SIRT1 levels in OSCC were determined, SIRT1 overexpression was achieved on transfecting OSCC cells with a SIRT1-containing plasmid, followed by evaluation of proliferative ability and invasiveness of these cells. RESULTS: SIRT1 levels were significantly lower in patients with OSCC than in controls (p < 0.05). Moreover, SIRT1 levels in patients with OSCC were significantly associated with the lymphovascular permeation but not with the sex, age, stage and location. Furthermore, SIRT1 overexpression inhibited proliferation and invasion in OSCC cells. CONCLUSION: The present results suggest that SIRT1 is a potential tumor suppressor in OSCC.

Causes of misdiagnosis in assessing tubal patency by transvaginal real-time three-dimensional hysterosalpingo-contrast sonography

SUMMARY OBJECTIVE This study aims to investigate the causes of misdiagnosis in assessing tubal patency by transvaginal real-time three-dimensional hysterosalpingo-contrast sonography (TVS RT-3D-HyCoSy), in order to improve the diagnostic efficiency of TVS RT-3D-HyCoSy. METHODS A total of 162 oviducts of 83 infertility patients were examined by TVS RT-3D-HyCoSy. These results were compared with the gold standard for laparoscopic dye studies, and the misdiagnosed cases were analyzed. RESULTS TVS RT-3D-HyCoSy revealed that 68 oviducts were unobstructed and 94 obstructed. The results for the 144 oviducts were in line with the gold standard, while those for 18 oviducts were not. The accuracy rate of the TVS RT-3D-HyCoSy was 88.9%, and the misdiagnosis rate was 11.1%. The main causes of misdiagnosis included contrast medium countercurrent and diffusion, oviduct spasm, abnormal shape or position of the oviduct, pelvic adhesion, and poor imaging operation. CONCLUSION TVS RT-3D-HyCoSy can well-evaluate tubal patency, and understand and improve the cause of misdiagnosis. Furthermore, the diagnostic efficiency of TVS RT-3D-HyCoSy can still be further improved.

RESUMO OBJETIVO Este estudo tem como objetivo investigar as causas do diagnóstico equivocado na avaliação da patência tubária por meio da ultrassonografia de contraste histerosalpingo em tempo real transvaginal (TVS RT-3D-HyCoSy), a fim de melhorar a eficiência diagnóstica das TVS RT-3D-HyCoSy. MÉTODOS Um total de 162 ovidutos em 83 pacientes da infertilidade foi examinado por TVS RT-3D-HyCoSy. Esses resultados foram comparados com o padrão ouro para estudos de tintura laparoscópica, e os casos diagnosticados erroneamente foram analisados. RESULTADOS TVS RT-3D-HyCoSy revelaram que 68 ovidutos foram desobstruídos e 94 ovidutos foram obstruídos. Os resultados para os 144 ovidutos estavam em consonância com o padrão ouro, enquanto que aqueles para os 18 ovidutos, não. A taxa de acurácia do TVS RT-3D-HyCoSy foi de 88,9%, e a taxa de erro de diagnóstico foi de 11,1%. As principais causas de erro de diagnóstico incluíram contraponto e difusão do meio de contraste, espasmo do oviduto, forma ou posição anormal do oviduto, adesão pélvica e má operação de imagem. CONCLUSÃO TVS RT-3D-HyCoSy pode bem avaliar a patência tubária, e compreender e melhorar a causa do erro de diagnóstico. Além disso, a eficiência diagnóstica do TVS RT-3D-HyCoSy ainda pode ser melhorada.