Stabilization of Ni-containing Keggin-type polyoxometalates with variable oxidation states as novel catalysts for electrochemical water oxidation †

The development of new recyclable and inexpensive electrochemically active species for water oxidation catalysis is the most crucial step for future utilization of renewables. Particularly, transition metal complexes containing internal multiple, cooperative metal centers to couple with redox catalysts in the inorganic Keggin-type polyoxometalate (POM) framework at high potential or under extreme pH conditions would be promising candidates. However, most reported Ni-containing POMs have been highly unstable towards hydrolytic decomposition, which precludes them from application as water oxidation catalysts (WOCs). Here, we have prepared new tri-Ni-containing POMs with variable oxidation states by charge tailored synthetic strategies for the first time and developed them as recyclable POMs for water oxidation catalysts. In addition, by implanting corresponding POM anions into the positively charged MIL-101(Cr) metal–organic framework (MOF), the entrapped Ni2+/Ni3+ species can show complete recyclability for water oxidation catalysis without encountering uncontrolled hydrolysis of the POM framework. As a result, a low onset potential of approximately 1.46 V vs. NHE for water oxidation with stable WOC performance is recorded. Based on this study, rational design and stabilization of other POM-electrocatalysts containing different multiple transition metal centres could be made possible

Proposed pathway for irradiation induced EMT.

<p>PTEN acts as an upstream regulator of the PI3K/Akt/GSK-3β signaling network to evoke the cascades of EMT. Slug regulates E-cadherin expression in a PTEN independent way.</p

Irradiation induced molecular and phenotypic changes of EMT.

<p>(A) Radiation cell survival curves and the clonogenic figures of the control KYSE-150 cells without irradiation and radioresistance subclone KYSE-150/RR cells. (B) Morphology of KYSE-150 and KYSE-150/RR cells was examined with phase-contrast microscopy. (C) Expression of EMT markers (E-cadherin and vimentin) and transcription repressors of E-cadherin (Snail and Slug) were detected by qRT-PCR, data shown as mean ±SD, *<i>P</i> <0.05. Data represent means with standard deviation from three independent experiments. (D) Representative western blots of E-cadherin, vimentin, Snail and Slug were showed.</p

Hsf4 counteracts Hsf1 transcription activities and increases lens epithelial cell survival in vitro

AbstractThe interplay between Hsf4 and Hsf1 plays an important role in the regulation of lens homeostasis. However, the mechanism of the intermolecular association involved is still unclear. In this paper, we find that reconstitution of Hsf4b into Hsf4−/− lens epithelial (mLEC/Hsf4−/−) cells can simultaneously downregulate Hsp70 expression and upregulate the expression of small heat shock proteins Hsp25 and αB-crystallin at both RNA and protein levels. ChIP assay results indicate Hsf4b, which binds to the promoters of Hsp90α, Hsp70.3, Hsp25 and αB-crystallin but not Hsp70.1, can inhibit Hsf1 binding to Hsp70.3 promoter and the heat shock mediated Hsp70 promoter activity by reducing Hsf1 protein expression. Hsf4b N-terminal hydrophobic region can interact with Hsf1 N-terminal hydrophobic region. Their interaction impairs Hsf1's intramolecular interaction between the N- and C-terminal hydrophobic regions, leading to Hsf1's cytosolic retention and protein degradation. Both lysosome inhibitors (chloroquine, pepstatin A plus E64d) and proteasome inhibitor MG132 can inhibit Hsf4-mediated Hsf1 protein degradation, but MG132 can induce Hsf1 activation as well. Upregulation of Hsf4b can significantly inhibit cisplatin and staurosporine induced lens epithelial cell apoptosis through direct upregulation of Hsp25 and αB-crystallin expression. Taken together, our results imply that upregulation of Hsf4b modulates the expression pattern of heat shock proteins in lens tissue by either directly binding to their promoters or promoting Hsf1 protein degradation. Moreover, upregulation of Hsf4b protects lens cell survival by upregulating anti-apoptotic pathways. These studies reveal a novel regulatory mechanism between Hsf1 and Hsf4b in modulating lens epithelial cell homeostasis

PTEN decreased Snail expression through inactivation of PI3K/Akt/GSK-3β signaling.

<p>(A) Expression of Snail and Slug detected by western blot analysis in KYSE-150 cells transfected with siPTEN or vehicle, or KYSE-150/RR cells transfected with pcDNA-PTEN or pcDNA3.0. (B) Expression of Snail were detected by qRT-PCR, data shown as mean±SD. (C) Representative western blot analysis showed expression of Akt, p-Akt, GSK-3β and p-GSK-3β. Data shown represent three different experiments. siPTEN is short for siRNA-PTEN. (D) Representative western blot analysis showed expression of Akt, p-Akt, GSK-3β, p-GSK-3β, Snail and E-cadherin in KYSE-150/RR cells with or without the phosphatidylinositol 3 kinase (PI3K) inhibitor, LY294002 (40 μM).</p

Irradiation-induced EMT enhanced cellular mobility.

<p>(A) KYSE-150 cells were subjected to a wound-healing assay with or without radiation at 100× magnification. Representative images were photographed right and 24 h after the scratch. (B) Representative images of migration assay and invasion assay of KYSE-150 cells with or without radiation were photographed after 24 h with crystal violet stain. (C) Summary graphs for migration and invasion (data shown as mean ±SD, * <i>P</i> <0.05).</p

PTEN deficiency is required for irradiation-induced EMT.

<p>(A) Radiation significantly decreases the expression of PTEN in the KESE-150/RR cells no matter in mRNA level (data presented as mean ±SD, **<i>P</i> <0.01) and protein level (representative western blots). (B) The transfected efficiency of siPTEN in KYSE-150 (left) and pcDNA-PTEN in KYSE-150/RR cells (right) (data presented as mean ±SD, **<i>P</i> <0.01). (C) Representative western blot analysis showed expression of PTEN, E-cadherin and vimentin in KYSE-150 cells transfected with siPTEN or vehicle, or KYSE-150/RR cells transfected with pcDNA-PTEN or pcDNA3.0. Data shown represent three different experiments. (D) Representative images of migration and invasion assay of KYSE-150 cells transfected with siPTEN or vehicle after 48 h (left); Summary graphs is for migration and invasion (right, data shown as mean ±SD, *<i>P</i> <0.05). (E) Representative images of migration assay and invasion assay of KYSE-150/RR cells transfected with pcDNA-PTEN or pcDNA3.0 were photographed after 24 h with crystal violet stain (left); Summary graphs for migration and invasion (right, data shown as mean ±SD, *<i>P</i> <0.05). siPTEN is short for siRNA-PTEN.</p

Precision Grinding Technology of Silicon Carbide (SiC) Ceramics by Longitudinal Torsional Ultrasonic Vibrations

Silicon carbide (SiC) ceramic material has become the most promising third-generation semiconductor material for its excellent mechanical properties at room temperature and high temperature. However, SiC ceramic machining has serious tool wear, low machining efficiency, poor machining quality and other disadvantages due to its high hardness and high wear resistance, which limits the promotion and application of such materials. In this paper, comparison experiments of longitudinal torsional ultrasonic vibration grinding (LTUVG) and common grinding (CG) of SiC ceramics were conducted, and the longitudinal torsional ultrasonic vibration grinding SiC ceramics cutting force model was developed. In addition, the effects of ultrasonic machining parameters on cutting forces, machining quality and subsurface cracking were investigated, and the main factors and optimal parameters affecting the cutting force improvement rate were obtained by orthogonal tests. The results showed that the maximum improvement of cutting force, surface roughness and subsurface crack fracture depth by longitudinal torsional ultrasonic vibrations were 82.59%, 22.78% and 30.75%, respectively. A longitudinal torsional ultrasonic vibrations cutting force prediction model containing the parameters of tool, material properties and ultrasound was established by the removal characteristics of SiC ceramic material, ultrasonic grinding principle and brittle fracture theory. And the predicted results were in good agreement with the experimental results, and the maximum error was less than 15%. The optimum process parameters for cutting force reduction were a spindle speed of 22,000 rpm, a feed rate of 600 mm/min and a depth of cut of 0.011 mm