Catalysts with Trimetallic Sites on Graphene-like C2N for Electrocatalytic Nitrogen Reduction Reaction: A Theoretical Investigation.

Electrocatalytic nitrogen reduction reaction (NRR) is a green and highly efficient way to replace the industrial Haber-Bosch process. Herein, clusters consisting of three transition metal atoms loaded on C2N as NRR electrocatalysts are investigated using density functional theory (DFT). Meanwhile, Ca was introduced as a promoter and the role of Ca in NRR was investigated. It was found that Ca anchored to the catalyst can act as an electron donor and effectively promote the activation of N2 on M3. In both M3@C2N and M3Ca@C2N (M=Fe, Co, Ni), the limiting potential (UL) is less negative than that of the Ru(0001) surface and has the ability to suppress the competitive hydrogen evolution reaction (HER). Among them, Fe3@C2N is suggested to be the most promising candidate for NRR with high thermal stability, strong N2 adsorption ability, low limiting potential, and good NRR selectivity. The concepts of trimetallic sites and alkaline earth metal promoters in this work provide theoretical guidance for the rational design of atomically active sites in electrocatalytic NRR.

Selective Reduction of NO into N2 Catalyzed by Rh1-Doped Cluster Anions RhCe2O3-5.

Catalytic conversion of toxic nitrogen oxide (NO) and carbon monoxide (CO) into nitrogen (N2) and carbon dioxide (CO2) is imperative under the weight of the increasingly stringent emission regulations, while a fundamental understanding of the nature of the active site to selectively drive N2 generation is elusive. Herein, in combination with state-of-the-art mass-spectrometric experiments and quantum-chemical calculations, we demonstrated that the rhodium-cerium oxide clusters RhCe2O3-5- can catalytically drive NO reduction by CO and give rise to N2 and CO2. This finding represents a sharp improvement in cluster science where N2O is commonly produced in the rarely established examples of catalytic NO reduction mediated with gas-phase clusters. We demonstrated the importance of the unique chemical environment in the RhCe2O3- cluster to guide the substantially improved N2 selectivity: a triatomic Lewis "acid-base-acid" Ceδ+-Rhδ--Ceδ+ site is proposed to strongly adsorb two NO molecules as well as the N2O intermediate that is attached on the Rh atom and can facilely dissociate to form N2 assisted by both Ce atoms.

Catalytic NO Reduction by NO Pre-Adsorbed RhCeO2 NO- Clusters.

A fundamental understanding on the dynamically structural evolution of catalysts induced by reactant gases under working conditions is challenging but pivotal in catalyst design. Herein, in combination with state-of-the-art mass spectrometry for cluster reactions, cryogenic photoelectron imaging spectroscopy, and quantum-chemical calculations, we identified that NO adsorption on rhodium-cerium bimetallic oxide cluster RhCeO2 - can create a Ce3+ ion in product RhCeO2 NO- that serves as the starting point to trigger the catalysis of NO reduction by CO. Theoretical calculations substantiated that the reduction of another two NO molecules into N2 O takes place exclusively on the Ce3+ ion while Rh behaves like a promoter to buffer electrons and cooperates with Ce3+ to drive NO reduction. Our finding demonstrates the importance of NO in regulating the catalytic behavior of Rh under reaction conditions and provides much-needed insights into the essence of NO reduction over Rh/CeO2 , one of the most efficient components in three-way catalysts for NOx removal.

Reverse water-gas shift reaction catalyzed by diatomic rhodium anions.

The reverse water-gas shift (RWGS, CO2 + H2 → CO + H2O, ΔH298 = +0.44 eV) reaction mediated by the diatomic anion Rh2- was successfully constructed. The generation of a gas-phase H2O molecule and ion product [Rh2(CO)ads]- was identified unambiguously at room temperature and the only elementary step that requires extra energy to complete the catalysis is the desorption of CO from [Rh2(CO)ads]-. This experimentally identified Rh2- anion represents the first gas-phase species that can drive the RWGS reaction because it is challenging to design effective routes to yield H2O from CO2 and H2. The reactions were performed by using our newly developed double ion trap reactors and characterized by mass spectrometry, photoelectron spectroscopy, and high-level quantum-chemical calculations. We found that the order that the reactants (CO2 or D2) were fed into the reactor did not have a pronounced impact on the reactivity and the final product distribution (D2O and Rh2CO-). The atomically precise insights into the key steps to guide the reaction toward the RWGS direction were provided.

Facile CO bond cleavage on polynuclear vanadium nitride clusters V4N5.

Identifying the structural configurations of precursors for CO dissociation is fundamentally interesting and industrially important in the fields of, e.g., Fischer-Tropsch synthesis. Herein, we demonstrated that CO could be dissociated on polynuclear vanadium nitride V4N5- clusters at room temperature, and a key intermediate, with CO in a N-assisted tilted bridge coordination where the C-O bond ruptures easily, was discovered. The reaction was characterized by mass spectrometry, photoelectron spectroscopy, and quantum-chemistry calculations, and the nature of the adsorbed CO on product V4N5CO- was further characterized by a collision-induced dissociation experiment. Theoretical analysis evidences that CO dissociation is predominantly governed by the low-coordinated V and N atoms on the (V3N4)VN- cluster and the V3N4 moiety resembles a support. This finding strongly suggests that a novel mode for facile CO dissociation was identified in a gas-phase cluster study.

Water-Gas Shift Catalyzed by Iridium-Vanadium Oxide Clusters IrVO2- with Iridium in a Rare Oxidation State of -II.

The discovery of compounds containing transition metals with an unusual and well-established oxidation state is vital to enrich our horizon on formal oxidation state. Herein, benefiting from the study of the water-gas shift reaction (CO + H2O → CO2 + H2) mediated with the iridium-vanadium oxide cluster IrVO2-, the missing -II oxidation state of iridium was identified. The reactions were performed by using our newly developed double ion trap reactors that can spatially separate the addition of reactants and are characterized by mass spectrometry and quantum-chemical calculations. This finding makes an important step that all the proposed 13 oxidation states of iridium (+IX to -III) have been known. The iridium atom in the IrVO2- cluster features the Ir═V double bond and resembles chemically the coordinated oxygen atom. A reactivity study demonstrated that the flexible role switch of iridium between an oxygen-atom like (Ir-IIVO2-) and a transition-metal-atom like behavior (Ir+IIVO3-) in different species can drive the water-gas shift reaction in the gas phase under ambient conditions. This result parallels and well rationalizes the extraordinary reactivity of oxide-supported iridium single-atom catalysts in related condensed-phase reactions.

CTRP1 decreases ABCA1 expression and promotes lipid accumulation through the miR-424-5p/FoxO1 pathway in THP-1 macrophage-derived foam cells.

Prevention of ATP binding cassette transporter A1 (ABCA1)-dependent cholesterol efflux leads to lipid accumulation in macrophages and atherosclerosis development. C1q tumor necrosis factor-related protein 1 (CTRP1), a conserved paralog of adiponectin, has been shown to aggravate atherosclerosis via its proinflammatory property. However, very little is known about its effects on ABCA1 expression and macrophage lipid accumulation. In the current studies, we found that CTRP1 downregulated ABCA1 expression, inhibited cholesterol efflux to apoA-I and promoted lipid accumulation in THP-1 macrophage-derived foam cells. Forkhead box O1 (FoxO1), a transcriptional repressor of ABCA1, was identified as a direct target of miR-424-5p. Mechanistically, CTRP1 attenuated miR-424-5p levels and then augmented FoxO1 expression in the nucleus, which led to downregulation of ABCA1 expression and inhibition of cholesterol efflux. In conclusion, these findings suggest that CTRP1 restrains cholesterol efflux and facilitates macrophage lipid accumulation through the miR-424-5p/FoxO1/ABCA1 signaling pathway, thereby providing a novel mechanistical insight into its proatherosclerotic action.

Activation of Carbon Dioxide by CoCDn- (n = 0-4) Anions.

Laser ablation generated CoCDn- (n = 0-4) anions were mass selected and then reacted with CO2 in an ion trap reactor. The reactions were characterized by mass spectrometry and quantum chemical calculations. The experimental results demonstrated that the CoC- anion can convert CO2 into CO. In contrast, the bare Co- anion is inert toward CO2. Coordinated D ligands can modify the reactivity of CoCD1-4- in which CoCD1-3- can reduce CO2 into CO selectively and CoCD4- can only adsorb CO2. The crucial roles of the coordinated C and D ligands to tune the reactivity of CoCDn- (n = 0-4) toward CO2 were rationalized by theoretical calculations. Note that the hydrogenation process that is usually observed in the reactions of gas-phase metal hydrides with CO2 is completely suppressed for the reactions CoCDn- + CO2. This study provides insights into the molecular-level origin for the observations that CO can be selectively generated from CO2 catalyzed by cobalt-containing carbides in heterogeneous catalysis.

A Facile N≡N Bond Cleavage by the Trinuclear Metal Center in Vanadium Carbide Cluster Anions V3C4.

Cleavage of the triple N≡N bond by metal clusters is of fundamental interest and practical importance in nitrogen fixation. Previous studies of N≡N bond cleavage by gas-phase metal clusters emphasized the importance of the dinuclear metal centers. Herein, the dissociative adsorption of N2 and subsequent C-N coupling on trinuclear carbide cluster anions V3C4- under thermal collision conditions have been characterized by employing mass spectrometry (collision induced dissociation), cryogenic photoelectron imaging spectroscopy, and quantum chemistry calculations. A theoretical analysis identified a crucial adsorption intermediate with N2 bonded with the V3 metal core in the end-on/side-on/side-on (ESS) mode, which most likely enables the facile cleavage of the N≡N bond. Such a vital N2 coordination in the ESS mode is a result of symmetry-matched interactions between the occupied orbitals of the metal core and both of the two empty π* orbitals of N2. Furthermore, carbon ligands also play a considerable role in enhancing the reactivity of the metal core toward N2. This study strongly suggests a new mechanism of N≡N bond cleavage by gas-phase metal clusters.

Catalytic CO Oxidation by O2 Mediated with Single Gold Atom Doped Titanium Oxide Cluster Anions AuTi2 O4-6.

Gas-phase studies on catalytic CO oxidation by O2 mediated with gold-containing heteronuclear metal oxide clusters are vital to obtain the structure-reactivity relationship of supported gold catalysts, while it is challenging to trigger the reactivity of clusters with closed-shell electronic structure in O2 activation. Herein, we identified that CO oxidation by O2 can be catalyzed by the AuTi2 O4-6- clusters, among which AuTi2 O4- with closed-shell electronic structure can effectively activate O2 . The reactions were characterized by mass spectrometry and quantum chemical calculations. Theoretical calculations showed that in the initial stage of O2 activation, the Ti2 O4 moiety in AuTi2 O4- contributes dominantly to activate O2 into superoxide (O2- ⋅) without participation of the Au atom. In subsequent steps, the intimate charge transfer interaction between Au and the Ti2 O4 moiety drives the direct dissociation of the O2- ⋅ unit.

Reactivity of Neutral Tantalum Sulfide Clusters Ta3Sn (n = 0-4) with N2.

Nitrogen (N2) fixation is a challenging and vital issue in chemistry. Inspired by the fact that the active sites of nitrogenases are polynuclear metal sulfide clusters, the reactivity of gas-phase metal sulfide clusters toward N2 has received considerable attention to gain fundamental insights into nitrogen fixation. Herein, neutral tantalum sulfide clusters have been prepared and their reactivity toward N2 has been investigated by mass spectrometry in conjunction with density functional theory (DFT) calculations. The experimental results showed that Ta3Sn (n = 0-3) could adsorb N2, while Ta3S4 was inert to N2. The DFT calculations revealed that the complete cleavage of the N≡N bond on the trinuclear metal center in the Ta3S0-3/N2 reaction systems was overall barrierless under thermal collision conditions. The sulfur ligands can facilitate the approaching of N2 toward the metal center but weaken the electron-donating ability of the metal center. The inertness of Ta3S4 is ascribed to the electron-deficient state of Ta3 in Ta3S4 and the least effective orbital interaction in the Ta3S4/N2 couple. This study provides new insights into the ligand effect on the interaction of the metal clusters with N2.

High glucose condition inhibits trophoblast proliferation, migration and invasion by downregulating placental growth factor expression.

AIM: This study aimed to investigate the effect of high glucose (HG) level on the proliferation, migration and invasion of trophoblasts and determine the role of placental growth factor (PLGF) in the process. METHODS: HTR8-S/Vneo was treated with different concentrations of d-glucose (0, 10, 15, 20, 25 and 30 µM) at different times (0, 6, 12 and 24 h). qRT-PCR and Western blot analyses were used to measure PLGF expression. The protein level of PLGF was measured by immunofluorescence. Cell proliferation was assessed with CCK-8 analysis. Wound healing and transwell assays were used to evaluate cell migration and invasion. Intercellular ROS was detected with DCFH-DA. RESULTS: After d-glucose treatment, the viability decreased in 25 and 30 µM groups. The HG group (25 µM) showed inhibited cell migration and invasion ability. The mRNA and protein levels of PLGF decreased under HG condition. Elevated ROS production was also detected in the HG group. Knocked-down PLGF expression enhanced increased ROS production and decreased cell migration and invasion, which reverted to the original levels after PLGF was overexpressed. CONCLUSION: High glucose treatment inhibited HTR8-S/Vneo viability, migration and invasion by downregulating PLGF expression.

Neutral Au1-Doped Cluster Catalysts AuTi2O3-6 for CO Oxidation by O2.

Oxide supported gold catalysts (e.g., Au/TiO2) are of great significance in heterogeneous catalysis owing to their extraordinary catalytic activity. Study of heteronuclear metal oxide clusters (HMOCs, e.g., Au xTi yO z q) is an important way to uncover the molecular-level mechanisms of gold catalysis in the related heterogeneous catalytic systems. However, the current studies of HMOCs are focused on charged clusters with little attention paid to neutral species. The reactivity study of neutral HMOCs is vital to have a comprehensive understanding of heterogeneous catalysis, but it is experimentally challenging because of the difficulty of cluster ionization and detection without fragmentation. Herein, benefiting from a homemade time-of-flight mass spectrometer coupled with a vacuum ultraviolet laser system, the reactivity of neutral Au1-doped titanium oxide clusters AuTi2O3-6 in catalytic CO oxidation by O2 has been successfully identified. The mechanistic details of the catalysis have been elucidated by quantum chemistry calculations. The crucial roles of the mobile AuCO species that can facilitate not only the process of CO oxidation but also the process of O2 activation have been discovered in the cluster catalysis. The fascinating results are of substantial importance to understand the mechanisms of CO oxidation over Au/TiO2, one type of the best studied gold catalysts.

Mechanistic Variants in Methane Activation Mediated by Gold(I) Supported on Silicon Oxide Clusters.

Cationic gold has been frequently identified as a suitable reactive species for activating methane in condensed-phase studies. However, it is far from clear how the coordination site manipulates the activity of such species. Herein, by anchoring AuI on silicon oxide cluster supports of variable sizes, the site-specific methane activation by AuI -Ox has been clarified by mass spectrometry in conjunction with quantum chemistry calculations. An unexpected mechanistic switch in C-H activation was identified for the cluster anions Au(SiO2 )n O- (n=1-3) that selectively activate one of the four C-H bonds of methane with different reaction efficiencies: a low efficiency was observed for the two-fold-coordinated gold ion (AuI, 2f ), which was anchored on an AuSiO3 - or AuSi2 O5 - cluster, through an oxidative addition mechanism (a homolytic process), and high efficiency was observed for the one-fold-coordinated gold ion (AuI, 1f ), which was supported on an AuSi3 O7 - cluster, through Lewis acid/base pairs mechanism (AuI, 1f ⋅⋅⋅O2- , a heterolytic process). Fine regulation of the 5d orbital level of the Au atom by the oxygen ligands accounted for the mechanistic difference between AuI, 2f and AuI, 1f species. The mechanistic understanding of the reactivity of AuI -Ox at a strictly molecular level can be used to clarify the dissimilar activity of gold anchored on different oxide supports.

miR-23b-3p and miR-125b-5p downregulate apo(a) expression by targeting Ets1 in HepG2 cells.

High concentrations of plasma lipoprotein(a) [Lp(a)] have been inferred to be an independent risk factor for cardiovascular and cerebrovascular diseases, such as coronary artery diseases, restenosis, and stroke. Apolipoprotein(a) [apo(a)] is one of the most important components of Lp(a) and contributes greatly to the increased concentration of plasma Lp(a). As a critical positive transacting factor of apo(a) gene, Ets1 has been proven as a target gene of several miRNAs, such as miR-193b, miR-125b-5p, miR-200b, miR-1, and miR-499. In this study, a series of experiments on miRNAs and relative miRNAs inhibitor delivered HepG2 cells were conducted, and two miRNAs that downregulate the apo(a) by targeting the 3'-UTR of Ets1 were identified. Results showed that apo(a) and Ets1 were differentially expressed in SMMC7721 and HepG2 cell lines. Meanwhile, apo(a) and Ets1 were inversely correlated with several hepatic endogenous miRNAs, such as miR-125b-5p, miR-23b-3p, miR-26a-5p, and miR-423-5p, which were predicted to bind to Ets1. Results show that miR-125b-5p and miR-23b-3p mimics could inhibit the synthesis of apo(a) by directly targeting Ets1 in HepG2, thereby reducing the plasma Lp (a) concentration.

Thermal activation of methane by vanadium boride cluster cations VBn+ (n = 3-6).

Investigation on the reactivity of atomic clusters represents an important approach to discover new species to activate and transform methane, the most stable alkane molecule. While a few types of transition metal species have been found to be capable of cleaving the C-H bond of methane, methane activation by the transition metal boride species has not been explored yet. This study reports that vanadium boride cluster cations VBn+ (n = 3-6) can dehydrogenate methane under thermal collision conditions. The mechanistic details of the efficient reactions have been elucidated by quantum chemistry calculations on the VB3+ reaction system. Compared to the non-polar bare B3 cluster, the B3 moiety in VB3+ can be polarized by the V+ cation and thus its reactivity toward methane can be much enhanced. This study provides new insights into the rational design of boron-based catalysts for methane activation.

Coupling of Methane and Carbon Dioxide Mediated by Diatomic Copper Boride Cations.

The use of CH4 and CO2 to produce value-added chemicals via direct C-C coupling is a challenging chemistry problem because of the inertness of these two molecules. Herein, mass spectrometric experiments and high-level quantum-chemical calculations have identified the first diatomic species (CuB+ ) that can couple CH4 with CO2 under thermal collision conditions to produce ketene (H2 C=C=O), an important intermediate in synthetic chemistry. The order to feed the reactants (CH4 and CO2 ) is important and CH4 should be firstly fed to produce the C2 product. Molecular-level mechanisms including control of product selectivity have been revealed for coupling of CH4 with CO2 under mild conditions.

Size-Dependent Reactivity of Nano-Sized Neutral Manganese Oxide Clusters toward Ethylene.

Neutral manganese oxide clusters with the general composition Mn2 N O3 N+x (N=2-22; x=-1, 0, 1) with dimensions up to a nanosize were prepared by laser ablation and reacted with C2 H4 in a fast flow reactor. The size-dependent reactivity of C2 H4 adsorption on these clusters was experimentally identified and the adsorption reactivity decreases generally with an increase of the cluster size. Density functional theory calculations were performed to study the geometrical and electronic structures of the Mn2 N O3 N (N=1-6) clusters. The calculated results indicated that the coordination number and the charge distribution of the metal centers are responsible for the experimentally observed size-dependent reactivity. The highly charged Mn atoms with low coordination are preferential to adsorb C2 H4 . In contrast, the neutral manganese oxide clusters are completely inert toward the saturated hydrocarbon molecule C2 H6 . This work provides new perspectives to design related materials in the separation of hydrocarbon molecules.

Effect of electroacupuncture intervention on angiogenesis in psoriasis mice. / ç”µé’ˆå¯¹é“¶å±‘ç— å°é¼ è¡€ç®¡ç”Ÿæˆçš„å½±å“åŠæœºåˆ¶ç ”ç©¶.

OBJECTIVES: To observe the effect of electroacupuncture (EA) stimulation of "Zusanli"(ST36) and"Xuehai"(SP10) on the angiogenesis of the local injured skin tissue in mice with psoriasis, so as to explore its mechanisms underlying improvement of psoriasis-induced skin lesions. METHODS: A total of 24 female BALB/c mice aged 6-8 weeks were randomly divided into control, model and EA groups, with 8 mice in each group. The psoriasis-like skin lesion model was established by application of 5% imiquimod (IMQ) cream to the mice's back skin, 62.5 mg/d, for 7 days after local depilation, and the mice of the control group received local application of an equal amount of petroleum jelly once a day for 7 days. EA stimulation (2 Hz/100 Hz) was applied to ST36 and SP10 for 30 min, once daily for 7 consecutive days. Photos of the topical injured skin at the back were taken every day, and the severity of psoriasis lesions (psoriasis area and severity index ï¼»PASIï¼½) was scaled. Following H.E. staining, the morphological changes in the injured skin tissue were observed with epidermal thickness analyzed, and the Masson staining was used to observe the proportion of collagen fibers in the injured skin tissues. Immunohistochemical method was used to detect the expression of microvascular markers CD31 and vascular endothelial growth factor (VEGF) and the microvascular density (MVD) was calculated. Western blot was used to detect the expression levels of CD31, VEGF proteins and mitogen activated protein kinases (MAPK) signaling pathway related proteins p38, phosphorylated p38 (p-p38), extracellular regulated protein kinases (ERK), p-ERK, c-Jun N-terminal kinase (JNK) and p-JNK in the injured skin tissue. RESULTS: Compared with the control group, the mice in the model group showed an evident increase in the erythema score, scales score, skin thickening score and PASI score, epidermal thickness, proportion of the collagen fibers, MVD value of CD31 and VEGF, and expression levels of CD31 and VEGF proteins, and p-p38/p38, p-ERK/ERK and p-JNK/JNK ratios in the injured skin tissue (P<0.001, P<0.01). In contrast to the model group, the EA group had a significant decrease in the levels of all the indexes mentioned above (P<0.05, P<0.01, P<0.001). CONCLUSIONS: EA intervention can improve the psoriasis-like skin lesions induced by IMQ in mice, which may be related with its functions in down-regulating the expression of angiogenic related factors CD31 and VEGF proteins and MAPK signaling pathway related proteins in the topical injured skin tissue.

Association Between Dietary Factors and Chronic Sinusitis Among Korean Individuals: Insights From a Large Population-Based Study in Asia.

Objective: Population-based studies on chronic sinusitis have predominantly focused on Europe and the Americas, but research on chronic sinusitis within large Asian populations remains scarce. This study aims to explore the link between dietary factors and chronic sinusitis among ethnic Koreans in Asia. Design: A cross-sectional study. Setting: Data were collected from the Korean National Health and Nutrition Examination Survey (KNHANES) in 2012. Participants: Participants in the study were included based on a doctor's diagnosis of chronic sinusitis, as determined through the ear, nose, and throat examination questionnaires. Results: Adolescents [adjusted P value (aP) < .001, adjusted odds ratio (aOR) = 1.881, 95% confidence interval (CI) = 1.380-2.564] and individuals with college and higher education (aP = .042, aOR = 1.298, 95% CI = 1.009-1.669) were more likely to develop chronic rhinosinusitis. In addition, levels of dietary fat [P = .001, interquartile range (IQR) = 34.085] and energy intake (P = .004, IQR = 981.106) were associated with an increased risk of chronic sinusitis. Moreover, high dietary inflammatory index (aP < .001, aOR = 0.547, 95% CI = 0.415-0.721), and high intake of fried pork chops (aP = .028, aOR = 1.335, 95% CI = 1.033-1.777), bread (aP = .024, aOR = 1.364, 95% CI = 1.042-1.786), and rice (aP = .021, aOR = 1.382, 95% CI = 1.051-1.818) were risk factors for chronic sinusitis, while cucumber consumption (aP < .001, aOR = 0.547, 95% CI = 0.415-0.721) was a protective factor for chronic sinusitis. Conclusion: This study revealed a significant correlation between diet and development of chronic sinusitis. These findings suggest that promoting an anti-inflammatory dietary pattern and providing guidance on healthy eating habits could help reduce the incidence of chronic sinusitis and enhance its management.