Degradation of the transition metal@Pt core-shell nanoparticle catalyst: a DFT study.

Electrocatalysts in acidic media face the issues of inactivation and degradation with complex thermodynamic processes. A density functional theory (DFT) calculation is performed to investigate the galvanic and pitting etching processes of metal@Pt (M@Pt) core-shell nanoparticles (12 transition elements are selected to replace the core atoms). The dissolution process with atomic etching follows the dissolution potential site-dependence phenomena, and the dissolution potential of the Pt shell exhibits a negative linear correlation with the average d-band center of the Pt shell. We have found that the specific shape effect, core-shell contact area and period effect all affect the potential difference at each step in the dissolution process. Meanwhile, the core atom segregation reduces the dissolution potential to form defects on the outermost shell, which is the driving force of halogen-pitting. By analyzing the 12 core elements and M@Pt nanoparticles of three specific shapes, Ir@Pt nanoparticles with a TCO-structure exhibit a high initial potential in multistep dissolution process throughout the galvanic etching process and good performance with respect to pitting corrosion and are strong candidates for nanoparticle catalysts.

[Effects of isovitexin on transient outward potassium current of ventricular myocytes in rats].

To investigate the effects of isovitexin Ⅳ on transient outward potassium current in rat ventricular myocytes. In this study, MTT assay was used to investigate the safe range of isovitexin. The results showed that the IC50 of the drug was in the range of 10-30 µmol•L⁻¹, and the drug concentration of 1-3 µmol•L⁻¹ for the patch clamp test was within the safe range. In addition, the single ventricular myocytes were obtained by single-enzymatic hydrolysis through aortic retrograde perfusion. The transient outward potassium current (Ito) of rat ventricular myocytes was guided and measured by whole-cell patch-clamp technique and the changes of current characteristics were recorded after isovite was applied. When the concentration of IV was less than 0.1 µmol•L⁻¹, there was no significant effect on Ito. However, with the increase in the concentration of IV (≥0.3 µmol•L⁻¹), the peak of Ito was decreased gradually, from (32.32±2.9) pA/pF to （25.83±4.3） pA/pF, 1 µmol•L⁻¹ IV and (19.51±3.5) pA/pF, 3 µmol•L⁻¹ IV respectively, with an inhibition effect in a concentration-dependent manner. In the range of 1-3 µmol•L⁻¹, IV down-regulated the I-V curve of Ito significantly. The activation curve showed that IV can enable the maximum half activation potential (V1/2) to move to the positive direction, and the V1/2 was increased from (19.59±1.6) mV to (22.81±1.7) mV and (28.86±1.4) mV at concentration of 1, 3 µmol•L⁻¹, meanwhile the activation curve moved to the right. However, the maximum half inactivating potential (V1/2) of the steady-state inactivation curve of Ito was significantly decreased from (－51.43±0.99) mV to (－61.81±1.3) mV with concentration of 1 µmol•L⁻¹ and (－71.50±1.4) mV with concentration of 3 µmol•L⁻¹. The inactivation time constant of recovery from inactivation (τ) was up-regulated significantly from (94.89±0.73) ms to (118.5±1.5) ms and (162.4±1.4) ms at concentration of 1, 3 µmol•L⁻¹ respectively. Meanwhile IV could enable the inactivation recovery curve to move to the right, which suggested that it can prolong the recovery time from inactivation of the transient outward potassium channel. In conclusion, isovitexin had a high inhibitory effect on Ito in rat ventricular myocytes.

Controllable assembly, characterization and catalytic properties of a new Strandberg-type organophosphotungstate.

Using phenylphosphonic acid, simple tungstate and copper(ii) compounds as starting materials, an organic-inorganic hybrid Strandberg-type organophosphotungstate, {[(Cu(H2O)(µ-bipy))2(C6H5PO3)2W5O15]}n (bipy = 4,4'-bipyridyl) (1), was assembled successfully under hydrothermal conditions and characterized by physico-chemical and spectroscopic methods. Compound 1 represents the first example of a transition metal complex modified organophosphotungstate cluster. In the crystal structure of compound 1, the polymeric 1-D {Cu-bipy}n chains are interconnected by [(C6H5PO3)2W5O15](4-) (abbreviated as {(C6H5P)2W5}) units into a 3-D framework. A hollow Keggin isopolytungstate [H2W12O40](6-) ({W12})-Cu(ii) coordination polymer, {[Cu(bipy)2((µ-bipy)Cu(bipy))2(H2W12O40)]·12H2O}n (2), was obtained at different molar ratios of the starting materials and pH. The two Cu(ii) coordination polymers exhibit good acid-catalytic activity for the synthesis of cyclohexanone ethylene ketal. Their fluorescence properties were studied.

Tim-4 Inhibits NO Generation by Murine Macrophages.

OBJECTIVE: T cell immunoglobulin- and mucin-domain-containing molecule-4 (Tim-4) receives much attention as a potentially negative regulator of immune responses. However, its modulation on macrophages has not been fully elucidated so far. This study aimed to identify the role of Tim-4 in nitric oxide (NO) modulation. METHODS: Macrophages were stimulated with 100 ng/ml LPS or 100 U/ml IFN-γ. RT-PCR was performed to detect TIM-4 mRNA expression. Tim-4 blocking antibody and NF-κB inhibitory ligand were involved in the study. NO levels were assayed by Griess reaction. Phosphorylation of NF-κB, Jak2 or Stat1 was verified by western blot. RESULTS: Tim-4 was up-regulated in murine macrophages after interferon-gamma (IFN-γ) stimulation. Tim-4 over-expression decreased NO production and inducible nitric oxide synthase (iNOS) expression in lipopolysaccharide (LPS) or IFN-γ-stimulated macrophages. Consistently, Tim-4 blockade promoted LPS or IFN-γ-induced NO secretion and iNOS expression. Tim-4 over-expression decreased LPS-induced nuclear factor kappa B (NF-κB) p65 phosphorylation in macrophages, which was abrogated by NF-κB inhibitory ligand. On the contrary, Tim-4 blocking increased LPS-induced NF-κB signaling, which was also abrogated by NF-κB inhibition. In addition, Tim-4 blockade promoted Jak2 and Stat1 phosphorylation in IFN-γ stimulated macrophages. CONCLUSION: These results indicate that Tim-4 is involved in negative regulation of NO production in macrophages, suggesting the critical role of Tim-4 in immune related diseases.

Two Strandberg-type organophosphomolybdates: synthesis, crystal structures and catalytic properties.

Two novel Strandberg-type organophosphomolybdate hybrid compounds [(Cu(H2O))2(µ-bipy)2(C6H5PO3)2Mo5O15]n (1) and [(Cu(H2O)2)2(µ-bipy)(C6H5PO3)2Mo5O15]n (2) (bipy = 4,4'-bipyridyl) were prepared under mild hydrothermal conditions and structurally characterized by physico-chemical and spectroscopic methods. Single crystal X-ray diffraction analysis reveals that compounds 1 and 2 are polyoxometalate-based Cu-coordination polymers with a three-dimensional framework. In 1, the Cu(2+) ions not only link [(C6H5PO3)2Mo5O15](4-) (abbreviated as {(C6H5P)2Mo5}) polyanions, but also act as connectors of bipy ligands to produce two symmetrical 1-D chains, all 1-D chains are further held together by polyanions to generate a 3-D network. In 2, each {(C6H5P)2Mo5} polyanion acting as a hexadentate ligand links four Cu(II)-bipy/H2O units, forming 2-D plane structures, which are further bridged by Cu(II)-bipy-Cu(II) fragments to generate a 3-D network. Their fluorescence properties and catalytic properties for the synthesis of cyclohexanone ethylene ketal were also investigated.